Actual source code: snes.c

      1: #include <petsc/private/snesimpl.h>
      2: #include <petscdmshell.h>
      3: #include <petscdraw.h>
      4: #include <petscds.h>
      5: #include <petscdmadaptor.h>
      6: #include <petscconvest.h>

      8: PetscBool         SNESRegisterAllCalled = PETSC_FALSE;
      9: PetscFunctionList SNESList              = NULL;

     11: /* Logging support */
     12: PetscClassId  SNES_CLASSID, DMSNES_CLASSID;
     13: PetscLogEvent SNES_Solve, SNES_Setup, SNES_FunctionEval, SNES_JacobianEval, SNES_NGSEval, SNES_NGSFuncEval, SNES_NPCSolve, SNES_ObjectiveEval;

     15: /*@
     16:    SNESSetErrorIfNotConverged - Causes SNESSolve() to generate an error if the solver has not converged.

     18:    Logically Collective on SNES

     20:    Input Parameters:
     21: +  snes - iterative context obtained from SNESCreate()
     22: -  flg - PETSC_TRUE indicates you want the error generated

     24:    Options database keys:
     25: .  -snes_error_if_not_converged : this takes an optional truth value (0/1/no/yes/true/false)

     27:    Level: intermediate

     29:    Notes:
     30:     Normally PETSc continues if a linear solver fails to converge, you can call SNESGetConvergedReason() after a SNESSolve()
     31:     to determine if it has converged.

     33: .seealso: SNESGetErrorIfNotConverged(), KSPGetErrorIfNotConverged(), KSPSetErrorIFNotConverged()
     34: @*/
     35: PetscErrorCode  SNESSetErrorIfNotConverged(SNES snes,PetscBool flg)
     36: {
     40:   snes->errorifnotconverged = flg;
     41:   return(0);
     42: }

     44: /*@
     45:    SNESGetErrorIfNotConverged - Will SNESSolve() generate an error if the solver does not converge?

     47:    Not Collective

     49:    Input Parameter:
     50: .  snes - iterative context obtained from SNESCreate()

     52:    Output Parameter:
     53: .  flag - PETSC_TRUE if it will generate an error, else PETSC_FALSE

     55:    Level: intermediate

     57: .seealso:  SNESSetErrorIfNotConverged(), KSPGetErrorIfNotConverged(), KSPSetErrorIFNotConverged()
     58: @*/
     59: PetscErrorCode  SNESGetErrorIfNotConverged(SNES snes,PetscBool  *flag)
     60: {
     64:   *flag = snes->errorifnotconverged;
     65:   return(0);
     66: }

     68: /*@
     69:     SNESSetAlwaysComputesFinalResidual - does the SNES always compute the residual at the final solution?

     71:    Logically Collective on SNES

     73:     Input Parameters:
     74: +   snes - the shell SNES
     75: -   flg - is the residual computed?

     77:    Level: advanced

     79: .seealso: SNESGetAlwaysComputesFinalResidual()
     80: @*/
     81: PetscErrorCode  SNESSetAlwaysComputesFinalResidual(SNES snes, PetscBool flg)
     82: {
     85:   snes->alwayscomputesfinalresidual = flg;
     86:   return(0);
     87: }

     89: /*@
     90:     SNESGetAlwaysComputesFinalResidual - does the SNES always compute the residual at the final solution?

     92:    Logically Collective on SNES

     94:     Input Parameter:
     95: .   snes - the shell SNES

     97:     Output Parameter:
     98: .   flg - is the residual computed?

    100:    Level: advanced

    102: .seealso: SNESSetAlwaysComputesFinalResidual()
    103: @*/
    104: PetscErrorCode  SNESGetAlwaysComputesFinalResidual(SNES snes, PetscBool *flg)
    105: {
    108:   *flg = snes->alwayscomputesfinalresidual;
    109:   return(0);
    110: }

    112: /*@
    113:    SNESSetFunctionDomainError - tells SNES that the input vector to your SNESFunction is not
    114:      in the functions domain. For example, negative pressure.

    116:    Logically Collective on SNES

    118:    Input Parameters:
    119: .  snes - the SNES context

    121:    Level: advanced

    123: .seealso: SNESCreate(), SNESSetFunction(), SNESFunction
    124: @*/
    125: PetscErrorCode  SNESSetFunctionDomainError(SNES snes)
    126: {
    129:   if (snes->errorifnotconverged) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"User code indicates input vector is not in the function domain");
    130:   snes->domainerror = PETSC_TRUE;
    131:   return(0);
    132: }

    134: /*@
    135:    SNESSetJacobianDomainError - tells SNES that computeJacobian does not make sense any more. For example there is a negative element transformation.

    137:    Logically Collective on SNES

    139:    Input Parameters:
    140: .  snes - the SNES context

    142:    Level: advanced

    144: .seealso: SNESCreate(), SNESSetFunction(), SNESFunction(), SNESSetFunctionDomainError()
    145: @*/
    146: PetscErrorCode SNESSetJacobianDomainError(SNES snes)
    147: {
    150:   if (snes->errorifnotconverged) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"User code indicates computeJacobian does not make sense");
    151:   snes->jacobiandomainerror = PETSC_TRUE;
    152:   return(0);
    153: }

    155: /*@
    156:    SNESSetCheckJacobianDomainError - if or not to check jacobian domain error after each Jacobian evaluation. By default, we check Jacobian domain error
    157:    in the debug mode, and do not check it in the optimized mode.

    159:    Logically Collective on SNES

    161:    Input Parameters:
    162: +  snes - the SNES context
    163: -  flg  - indicates if or not to check jacobian domain error after each Jacobian evaluation

    165:    Level: advanced

    167: .seealso: SNESCreate(), SNESSetFunction(), SNESFunction(), SNESSetFunctionDomainError(), SNESGetCheckJacobianDomainError()
    168: @*/
    169: PetscErrorCode SNESSetCheckJacobianDomainError(SNES snes, PetscBool flg)
    170: {
    173:   snes->checkjacdomainerror = flg;
    174:   return(0);
    175: }

    177: /*@
    178:    SNESGetCheckJacobianDomainError - Get an indicator whether or not we are checking Jacobian domain errors after each Jacobian evaluation.

    180:    Logically Collective on SNES

    182:    Input Parameters:
    183: .  snes - the SNES context

    185:    Output Parameters:
    186: .  flg  - PETSC_FALSE indicates that we don't check jacobian domain errors after each Jacobian evaluation

    188:    Level: advanced

    190: .seealso: SNESCreate(), SNESSetFunction(), SNESFunction(), SNESSetFunctionDomainError(), SNESSetCheckJacobianDomainError()
    191: @*/
    192: PetscErrorCode SNESGetCheckJacobianDomainError(SNES snes, PetscBool *flg)
    193: {
    197:   *flg = snes->checkjacdomainerror;
    198:   return(0);
    199: }

    201: /*@
    202:    SNESGetFunctionDomainError - Gets the status of the domain error after a call to SNESComputeFunction;

    204:    Logically Collective on SNES

    206:    Input Parameters:
    207: .  snes - the SNES context

    209:    Output Parameters:
    210: .  domainerror - Set to PETSC_TRUE if there's a domain error; PETSC_FALSE otherwise.

    212:    Level: advanced

    214: .seealso: SNESSetFunctionDomainError(), SNESComputeFunction()
    215: @*/
    216: PetscErrorCode  SNESGetFunctionDomainError(SNES snes, PetscBool *domainerror)
    217: {
    221:   *domainerror = snes->domainerror;
    222:   return(0);
    223: }

    225: /*@
    226:    SNESGetJacobianDomainError - Gets the status of the Jacobian domain error after a call to SNESComputeJacobian;

    228:    Logically Collective on SNES

    230:    Input Parameters:
    231: .  snes - the SNES context

    233:    Output Parameters:
    234: .  domainerror - Set to PETSC_TRUE if there's a jacobian domain error; PETSC_FALSE otherwise.

    236:    Level: advanced

    238: .seealso: SNESSetFunctionDomainError(), SNESComputeFunction(),SNESGetFunctionDomainError()
    239: @*/
    240: PetscErrorCode SNESGetJacobianDomainError(SNES snes, PetscBool *domainerror)
    241: {
    245:   *domainerror = snes->jacobiandomainerror;
    246:   return(0);
    247: }

    249: /*@C
    250:   SNESLoad - Loads a SNES that has been stored in binary  with SNESView().

    252:   Collective on PetscViewer

    254:   Input Parameters:
    255: + newdm - the newly loaded SNES, this needs to have been created with SNESCreate() or
    256:            some related function before a call to SNESLoad().
    257: - viewer - binary file viewer, obtained from PetscViewerBinaryOpen()

    259:    Level: intermediate

    261:   Notes:
    262:    The type is determined by the data in the file, any type set into the SNES before this call is ignored.

    264:   Notes for advanced users:
    265:   Most users should not need to know the details of the binary storage
    266:   format, since SNESLoad() and TSView() completely hide these details.
    267:   But for anyone who's interested, the standard binary matrix storage
    268:   format is
    269: .vb
    270:      has not yet been determined
    271: .ve

    273: .seealso: PetscViewerBinaryOpen(), SNESView(), MatLoad(), VecLoad()
    274: @*/
    275: PetscErrorCode  SNESLoad(SNES snes, PetscViewer viewer)
    276: {
    278:   PetscBool      isbinary;
    279:   PetscInt       classid;
    280:   char           type[256];
    281:   KSP            ksp;
    282:   DM             dm;
    283:   DMSNES         dmsnes;

    288:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);
    289:   if (!isbinary) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONG,"Invalid viewer; open viewer with PetscViewerBinaryOpen()");

    291:   PetscViewerBinaryRead(viewer,&classid,1,NULL,PETSC_INT);
    292:   if (classid != SNES_FILE_CLASSID) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONG,"Not SNES next in file");
    293:   PetscViewerBinaryRead(viewer,type,256,NULL,PETSC_CHAR);
    294:   SNESSetType(snes, type);
    295:   if (snes->ops->load) {
    296:     (*snes->ops->load)(snes,viewer);
    297:   }
    298:   SNESGetDM(snes,&dm);
    299:   DMGetDMSNES(dm,&dmsnes);
    300:   DMSNESLoad(dmsnes,viewer);
    301:   SNESGetKSP(snes,&ksp);
    302:   KSPLoad(ksp,viewer);
    303:   return(0);
    304: }

    306: #include <petscdraw.h>
    307: #if defined(PETSC_HAVE_SAWS)
    308: #include <petscviewersaws.h>
    309: #endif

    311: /*@C
    312:    SNESViewFromOptions - View from Options

    314:    Collective on SNES

    316:    Input Parameters:
    317: +  A - the application ordering context
    318: .  obj - Optional object
    319: -  name - command line option

    321:    Level: intermediate
    322: .seealso:  SNES, SNESView, PetscObjectViewFromOptions(), SNESCreate()
    323: @*/
    324: PetscErrorCode  SNESViewFromOptions(SNES A,PetscObject obj,const char name[])
    325: {

    330:   PetscObjectViewFromOptions((PetscObject)A,obj,name);
    331:   return(0);
    332: }

    334: PETSC_EXTERN PetscErrorCode SNESComputeJacobian_DMDA(SNES,Vec,Mat,Mat,void*);

    336: /*@C
    337:    SNESView - Prints the SNES data structure.

    339:    Collective on SNES

    341:    Input Parameters:
    342: +  SNES - the SNES context
    343: -  viewer - visualization context

    345:    Options Database Key:
    346: .  -snes_view - Calls SNESView() at end of SNESSolve()

    348:    Notes:
    349:    The available visualization contexts include
    350: +     PETSC_VIEWER_STDOUT_SELF - standard output (default)
    351: -     PETSC_VIEWER_STDOUT_WORLD - synchronized standard
    352:          output where only the first processor opens
    353:          the file.  All other processors send their
    354:          data to the first processor to print.

    356:    The available formats include
    357: +     PETSC_VIEWER_DEFAULT - standard output (default)
    358: -     PETSC_VIEWER_ASCII_INFO_DETAIL - more verbose output for SNESNASM

    360:    The user can open an alternative visualization context with
    361:    PetscViewerASCIIOpen() - output to a specified file.

    363:   In the debugger you can do "call SNESView(snes,0)" to display the SNES solver. (The same holds for any PETSc object viewer).

    365:    Level: beginner

    367: .seealso: PetscViewerASCIIOpen()
    368: @*/
    369: PetscErrorCode  SNESView(SNES snes,PetscViewer viewer)
    370: {
    371:   SNESKSPEW      *kctx;
    373:   KSP            ksp;
    374:   SNESLineSearch linesearch;
    375:   PetscBool      iascii,isstring,isbinary,isdraw;
    376:   DMSNES         dmsnes;
    377: #if defined(PETSC_HAVE_SAWS)
    378:   PetscBool      issaws;
    379: #endif

    383:   if (!viewer) {
    384:     PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&viewer);
    385:   }

    389:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
    390:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);
    391:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);
    392:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERDRAW,&isdraw);
    393: #if defined(PETSC_HAVE_SAWS)
    394:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSAWS,&issaws);
    395: #endif
    396:   if (iascii) {
    397:     SNESNormSchedule normschedule;
    398:     DM               dm;
    399:     PetscErrorCode   (*cJ)(SNES,Vec,Mat,Mat,void*);
    400:     void             *ctx;
    401:     const char       *pre = "";

    403:     PetscObjectPrintClassNamePrefixType((PetscObject)snes,viewer);
    404:     if (!snes->setupcalled) {
    405:       PetscViewerASCIIPrintf(viewer,"  SNES has not been set up so information may be incomplete\n");
    406:     }
    407:     if (snes->ops->view) {
    408:       PetscViewerASCIIPushTab(viewer);
    409:       (*snes->ops->view)(snes,viewer);
    410:       PetscViewerASCIIPopTab(viewer);
    411:     }
    412:     PetscViewerASCIIPrintf(viewer,"  maximum iterations=%D, maximum function evaluations=%D\n",snes->max_its,snes->max_funcs);
    413:     PetscViewerASCIIPrintf(viewer,"  tolerances: relative=%g, absolute=%g, solution=%g\n",(double)snes->rtol,(double)snes->abstol,(double)snes->stol);
    414:     if (snes->usesksp) {
    415:       PetscViewerASCIIPrintf(viewer,"  total number of linear solver iterations=%D\n",snes->linear_its);
    416:     }
    417:     PetscViewerASCIIPrintf(viewer,"  total number of function evaluations=%D\n",snes->nfuncs);
    418:     SNESGetNormSchedule(snes, &normschedule);
    419:     if (normschedule > 0) {PetscViewerASCIIPrintf(viewer,"  norm schedule %s\n",SNESNormSchedules[normschedule]);}
    420:     if (snes->gridsequence) {
    421:       PetscViewerASCIIPrintf(viewer,"  total number of grid sequence refinements=%D\n",snes->gridsequence);
    422:     }
    423:     if (snes->ksp_ewconv) {
    424:       kctx = (SNESKSPEW*)snes->kspconvctx;
    425:       if (kctx) {
    426:         PetscViewerASCIIPrintf(viewer,"  Eisenstat-Walker computation of KSP relative tolerance (version %D)\n",kctx->version);
    427:         PetscViewerASCIIPrintf(viewer,"    rtol_0=%g, rtol_max=%g, threshold=%g\n",(double)kctx->rtol_0,(double)kctx->rtol_max,(double)kctx->threshold);
    428:         PetscViewerASCIIPrintf(viewer,"    gamma=%g, alpha=%g, alpha2=%g\n",(double)kctx->gamma,(double)kctx->alpha,(double)kctx->alpha2);
    429:       }
    430:     }
    431:     if (snes->lagpreconditioner == -1) {
    432:       PetscViewerASCIIPrintf(viewer,"  Preconditioned is never rebuilt\n");
    433:     } else if (snes->lagpreconditioner > 1) {
    434:       PetscViewerASCIIPrintf(viewer,"  Preconditioned is rebuilt every %D new Jacobians\n",snes->lagpreconditioner);
    435:     }
    436:     if (snes->lagjacobian == -1) {
    437:       PetscViewerASCIIPrintf(viewer,"  Jacobian is never rebuilt\n");
    438:     } else if (snes->lagjacobian > 1) {
    439:       PetscViewerASCIIPrintf(viewer,"  Jacobian is rebuilt every %D SNES iterations\n",snes->lagjacobian);
    440:     }
    441:     SNESGetDM(snes,&dm);
    442:     DMSNESGetJacobian(dm,&cJ,&ctx);
    443:     if (snes->mf_operator) {
    444:       PetscViewerASCIIPrintf(viewer,"  Jacobian is applied matrix-free with differencing\n");
    445:       pre  = "Preconditioning ";
    446:     }
    447:     if (cJ == SNESComputeJacobianDefault) {
    448:       PetscViewerASCIIPrintf(viewer,"  %sJacobian is built using finite differences one column at a time\n",pre);
    449:     } else if (cJ == SNESComputeJacobianDefaultColor) {
    450:       PetscViewerASCIIPrintf(viewer,"  %sJacobian is built using finite differences with coloring\n",pre);
    451:     /* it slightly breaks data encapsulation for access the DMDA information directly */
    452:     } else if (cJ == SNESComputeJacobian_DMDA) {
    453:       MatFDColoring fdcoloring;
    454:       PetscObjectQuery((PetscObject)dm,"DMDASNES_FDCOLORING",(PetscObject*)&fdcoloring);
    455:       if (fdcoloring) {
    456:         PetscViewerASCIIPrintf(viewer,"  %sJacobian is built using colored finite differences on a DMDA\n",pre);
    457:       } else {
    458:         PetscViewerASCIIPrintf(viewer,"  %sJacobian is built using a DMDA local Jacobian\n",pre);
    459:       }
    460:     } else if (snes->mf) {
    461:       PetscViewerASCIIPrintf(viewer,"  Jacobian is applied matrix-free with differencing, no explict Jacobian\n");
    462:     }
    463:   } else if (isstring) {
    464:     const char *type;
    465:     SNESGetType(snes,&type);
    466:     PetscViewerStringSPrintf(viewer," SNESType: %-7.7s",type);
    467:     if (snes->ops->view) {(*snes->ops->view)(snes,viewer);}
    468:   } else if (isbinary) {
    469:     PetscInt    classid = SNES_FILE_CLASSID;
    470:     MPI_Comm    comm;
    471:     PetscMPIInt rank;
    472:     char        type[256];

    474:     PetscObjectGetComm((PetscObject)snes,&comm);
    475:     MPI_Comm_rank(comm,&rank);
    476:     if (!rank) {
    477:       PetscViewerBinaryWrite(viewer,&classid,1,PETSC_INT);
    478:       PetscStrncpy(type,((PetscObject)snes)->type_name,sizeof(type));
    479:       PetscViewerBinaryWrite(viewer,type,sizeof(type),PETSC_CHAR);
    480:     }
    481:     if (snes->ops->view) {
    482:       (*snes->ops->view)(snes,viewer);
    483:     }
    484:   } else if (isdraw) {
    485:     PetscDraw draw;
    486:     char      str[36];
    487:     PetscReal x,y,bottom,h;

    489:     PetscViewerDrawGetDraw(viewer,0,&draw);
    490:     PetscDrawGetCurrentPoint(draw,&x,&y);
    491:     PetscStrncpy(str,"SNES: ",sizeof(str));
    492:     PetscStrlcat(str,((PetscObject)snes)->type_name,sizeof(str));
    493:     PetscDrawStringBoxed(draw,x,y,PETSC_DRAW_BLUE,PETSC_DRAW_BLACK,str,NULL,&h);
    494:     bottom = y - h;
    495:     PetscDrawPushCurrentPoint(draw,x,bottom);
    496:     if (snes->ops->view) {
    497:       (*snes->ops->view)(snes,viewer);
    498:     }
    499: #if defined(PETSC_HAVE_SAWS)
    500:   } else if (issaws) {
    501:     PetscMPIInt rank;
    502:     const char *name;

    504:     PetscObjectGetName((PetscObject)snes,&name);
    505:     MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
    506:     if (!((PetscObject)snes)->amsmem && !rank) {
    507:       char       dir[1024];

    509:       PetscObjectViewSAWs((PetscObject)snes,viewer);
    510:       PetscSNPrintf(dir,1024,"/PETSc/Objects/%s/its",name);
    511:       PetscStackCallSAWs(SAWs_Register,(dir,&snes->iter,1,SAWs_READ,SAWs_INT));
    512:       if (!snes->conv_hist) {
    513:         SNESSetConvergenceHistory(snes,NULL,NULL,PETSC_DECIDE,PETSC_TRUE);
    514:       }
    515:       PetscSNPrintf(dir,1024,"/PETSc/Objects/%s/conv_hist",name);
    516:       PetscStackCallSAWs(SAWs_Register,(dir,snes->conv_hist,10,SAWs_READ,SAWs_DOUBLE));
    517:     }
    518: #endif
    519:   }
    520:   if (snes->linesearch) {
    521:     SNESGetLineSearch(snes, &linesearch);
    522:     PetscViewerASCIIPushTab(viewer);
    523:     SNESLineSearchView(linesearch, viewer);
    524:     PetscViewerASCIIPopTab(viewer);
    525:   }
    526:   if (snes->npc && snes->usesnpc) {
    527:     PetscViewerASCIIPushTab(viewer);
    528:     SNESView(snes->npc, viewer);
    529:     PetscViewerASCIIPopTab(viewer);
    530:   }
    531:   PetscViewerASCIIPushTab(viewer);
    532:   DMGetDMSNES(snes->dm,&dmsnes);
    533:   DMSNESView(dmsnes, viewer);
    534:   PetscViewerASCIIPopTab(viewer);
    535:   if (snes->usesksp) {
    536:     SNESGetKSP(snes,&ksp);
    537:     PetscViewerASCIIPushTab(viewer);
    538:     KSPView(ksp,viewer);
    539:     PetscViewerASCIIPopTab(viewer);
    540:   }
    541:   if (isdraw) {
    542:     PetscDraw draw;
    543:     PetscViewerDrawGetDraw(viewer,0,&draw);
    544:     PetscDrawPopCurrentPoint(draw);
    545:   }
    546:   return(0);
    547: }

    549: /*
    550:   We retain a list of functions that also take SNES command
    551:   line options. These are called at the end SNESSetFromOptions()
    552: */
    553: #define MAXSETFROMOPTIONS 5
    554: static PetscInt numberofsetfromoptions;
    555: static PetscErrorCode (*othersetfromoptions[MAXSETFROMOPTIONS])(SNES);

    557: /*@C
    558:   SNESAddOptionsChecker - Adds an additional function to check for SNES options.

    560:   Not Collective

    562:   Input Parameter:
    563: . snescheck - function that checks for options

    565:   Level: developer

    567: .seealso: SNESSetFromOptions()
    568: @*/
    569: PetscErrorCode  SNESAddOptionsChecker(PetscErrorCode (*snescheck)(SNES))
    570: {
    572:   if (numberofsetfromoptions >= MAXSETFROMOPTIONS) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE, "Too many options checkers, only %D allowed", MAXSETFROMOPTIONS);
    573:   othersetfromoptions[numberofsetfromoptions++] = snescheck;
    574:   return(0);
    575: }

    577: PETSC_INTERN PetscErrorCode SNESDefaultMatrixFreeCreate2(SNES,Vec,Mat*);

    579: static PetscErrorCode SNESSetUpMatrixFree_Private(SNES snes, PetscBool hasOperator, PetscInt version)
    580: {
    581:   Mat            J;
    583:   MatNullSpace   nullsp;

    588:   if (!snes->vec_func && (snes->jacobian || snes->jacobian_pre)) {
    589:     Mat A = snes->jacobian, B = snes->jacobian_pre;
    590:     MatCreateVecs(A ? A : B, NULL,&snes->vec_func);
    591:   }

    593:   if (version == 1) {
    594:     MatCreateSNESMF(snes,&J);
    595:     MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);
    596:     MatSetFromOptions(J);
    597:   } else if (version == 2) {
    598:     if (!snes->vec_func) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"SNESSetFunction() must be called first");
    599: #if !defined(PETSC_USE_COMPLEX) && !defined(PETSC_USE_REAL_SINGLE) && !defined(PETSC_USE_REAL___FLOAT128) && !defined(PETSC_USE_REAL___FP16)
    600:     SNESDefaultMatrixFreeCreate2(snes,snes->vec_func,&J);
    601: #else
    602:     SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP, "matrix-free operator routines (version 2)");
    603: #endif
    604:   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE, "matrix-free operator routines, only version 1 and 2");

    606:   /* attach any user provided null space that was on Amat to the newly created matrix free matrix */
    607:   if (snes->jacobian) {
    608:     MatGetNullSpace(snes->jacobian,&nullsp);
    609:     if (nullsp) {
    610:       MatSetNullSpace(J,nullsp);
    611:     }
    612:   }

    614:   PetscInfo1(snes,"Setting default matrix-free operator routines (version %D)\n", version);
    615:   if (hasOperator) {

    617:     /* This version replaces the user provided Jacobian matrix with a
    618:        matrix-free version but still employs the user-provided preconditioner matrix. */
    619:     SNESSetJacobian(snes,J,NULL,NULL,NULL);
    620:   } else {
    621:     /* This version replaces both the user-provided Jacobian and the user-
    622:      provided preconditioner Jacobian with the default matrix free version. */
    623:     if ((snes->npcside== PC_LEFT) && snes->npc) {
    624:       if (!snes->jacobian){SNESSetJacobian(snes,J,NULL,NULL,NULL);}
    625:     } else {
    626:       KSP       ksp;
    627:       PC        pc;
    628:       PetscBool match;

    630:       SNESSetJacobian(snes,J,J,MatMFFDComputeJacobian,NULL);
    631:       /* Force no preconditioner */
    632:       SNESGetKSP(snes,&ksp);
    633:       KSPGetPC(ksp,&pc);
    634:       PetscObjectTypeCompare((PetscObject)pc,PCSHELL,&match);
    635:       if (!match) {
    636:         PetscInfo(snes,"Setting default matrix-free preconditioner routines\nThat is no preconditioner is being used\n");
    637:         PCSetType(pc,PCNONE);
    638:       }
    639:     }
    640:   }
    641:   MatDestroy(&J);
    642:   return(0);
    643: }

    645: static PetscErrorCode DMRestrictHook_SNESVecSol(DM dmfine,Mat Restrict,Vec Rscale,Mat Inject,DM dmcoarse,void *ctx)
    646: {
    647:   SNES           snes = (SNES)ctx;
    649:   Vec            Xfine,Xfine_named = NULL,Xcoarse;

    652:   if (PetscLogPrintInfo) {
    653:     PetscInt finelevel,coarselevel,fineclevel,coarseclevel;
    654:     DMGetRefineLevel(dmfine,&finelevel);
    655:     DMGetCoarsenLevel(dmfine,&fineclevel);
    656:     DMGetRefineLevel(dmcoarse,&coarselevel);
    657:     DMGetCoarsenLevel(dmcoarse,&coarseclevel);
    658:     PetscInfo4(dmfine,"Restricting SNES solution vector from level %D-%D to level %D-%D\n",finelevel,fineclevel,coarselevel,coarseclevel);
    659:   }
    660:   if (dmfine == snes->dm) Xfine = snes->vec_sol;
    661:   else {
    662:     DMGetNamedGlobalVector(dmfine,"SNESVecSol",&Xfine_named);
    663:     Xfine = Xfine_named;
    664:   }
    665:   DMGetNamedGlobalVector(dmcoarse,"SNESVecSol",&Xcoarse);
    666:   if (Inject) {
    667:     MatRestrict(Inject,Xfine,Xcoarse);
    668:   } else {
    669:     MatRestrict(Restrict,Xfine,Xcoarse);
    670:     VecPointwiseMult(Xcoarse,Xcoarse,Rscale);
    671:   }
    672:   DMRestoreNamedGlobalVector(dmcoarse,"SNESVecSol",&Xcoarse);
    673:   if (Xfine_named) {DMRestoreNamedGlobalVector(dmfine,"SNESVecSol",&Xfine_named);}
    674:   return(0);
    675: }

    677: static PetscErrorCode DMCoarsenHook_SNESVecSol(DM dm,DM dmc,void *ctx)
    678: {

    682:   DMCoarsenHookAdd(dmc,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,ctx);
    683:   return(0);
    684: }

    686: /* This may be called to rediscretize the operator on levels of linear multigrid. The DM shuffle is so the user can
    687:  * safely call SNESGetDM() in their residual evaluation routine. */
    688: static PetscErrorCode KSPComputeOperators_SNES(KSP ksp,Mat A,Mat B,void *ctx)
    689: {
    690:   SNES           snes = (SNES)ctx;
    692:   Vec            X,Xnamed = NULL;
    693:   DM             dmsave;
    694:   void           *ctxsave;
    695:   PetscErrorCode (*jac)(SNES,Vec,Mat,Mat,void*) = NULL;

    698:   dmsave = snes->dm;
    699:   KSPGetDM(ksp,&snes->dm);
    700:   if (dmsave == snes->dm) X = snes->vec_sol; /* We are on the finest level */
    701:   else {                                     /* We are on a coarser level, this vec was initialized using a DM restrict hook */
    702:     DMGetNamedGlobalVector(snes->dm,"SNESVecSol",&Xnamed);
    703:     X    = Xnamed;
    704:     SNESGetJacobian(snes,NULL,NULL,&jac,&ctxsave);
    705:     /* If the DM's don't match up, the MatFDColoring context needed for the jacobian won't match up either -- fixit. */
    706:     if (jac == SNESComputeJacobianDefaultColor) {
    707:       SNESSetJacobian(snes,NULL,NULL,SNESComputeJacobianDefaultColor,NULL);
    708:     }
    709:   }
    710:   /* Make sure KSP DM has the Jacobian computation routine */
    711:   {
    712:     DMSNES sdm;

    714:     DMGetDMSNES(snes->dm, &sdm);
    715:     if (!sdm->ops->computejacobian) {
    716:       DMCopyDMSNES(dmsave, snes->dm);
    717:     }
    718:   }
    719:   /* Compute the operators */
    720:   SNESComputeJacobian(snes,X,A,B);
    721:   /* Put the previous context back */
    722:   if (snes->dm != dmsave && jac == SNESComputeJacobianDefaultColor) {
    723:     SNESSetJacobian(snes,NULL,NULL,jac,ctxsave);
    724:   }

    726:   if (Xnamed) {DMRestoreNamedGlobalVector(snes->dm,"SNESVecSol",&Xnamed);}
    727:   snes->dm = dmsave;
    728:   return(0);
    729: }

    731: /*@
    732:    SNESSetUpMatrices - ensures that matrices are available for SNES, to be called by SNESSetUp_XXX()

    734:    Collective

    736:    Input Arguments:
    737: .  snes - snes to configure

    739:    Level: developer

    741: .seealso: SNESSetUp()
    742: @*/
    743: PetscErrorCode SNESSetUpMatrices(SNES snes)
    744: {
    746:   DM             dm;
    747:   DMSNES         sdm;

    750:   SNESGetDM(snes,&dm);
    751:   DMGetDMSNES(dm,&sdm);
    752:   if (!snes->jacobian && snes->mf) {
    753:     Mat  J;
    754:     void *functx;
    755:     MatCreateSNESMF(snes,&J);
    756:     MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);
    757:     MatSetFromOptions(J);
    758:     SNESGetFunction(snes,NULL,NULL,&functx);
    759:     SNESSetJacobian(snes,J,J,NULL,NULL);
    760:     MatDestroy(&J);
    761:   } else if (snes->mf_operator && !snes->jacobian_pre && !snes->jacobian) {
    762:     Mat J,B;
    763:     MatCreateSNESMF(snes,&J);
    764:     MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);
    765:     MatSetFromOptions(J);
    766:     DMCreateMatrix(snes->dm,&B);
    767:     /* sdm->computejacobian was already set to reach here */
    768:     SNESSetJacobian(snes,J,B,NULL,NULL);
    769:     MatDestroy(&J);
    770:     MatDestroy(&B);
    771:   } else if (!snes->jacobian_pre) {
    772:     PetscDS   prob;
    773:     Mat       J, B;
    774:     PetscBool hasPrec   = PETSC_FALSE;

    776:     J    = snes->jacobian;
    777:     DMGetDS(dm, &prob);
    778:     if (prob) {PetscDSHasJacobianPreconditioner(prob, &hasPrec);}
    779:     if (J)            {PetscObjectReference((PetscObject) J);}
    780:     else if (hasPrec) {DMCreateMatrix(snes->dm, &J);}
    781:     DMCreateMatrix(snes->dm, &B);
    782:     SNESSetJacobian(snes, J ? J : B, B, NULL, NULL);
    783:     MatDestroy(&J);
    784:     MatDestroy(&B);
    785:   }
    786:   {
    787:     KSP ksp;
    788:     SNESGetKSP(snes,&ksp);
    789:     KSPSetComputeOperators(ksp,KSPComputeOperators_SNES,snes);
    790:     DMCoarsenHookAdd(snes->dm,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,snes);
    791:   }
    792:   return(0);
    793: }

    795: /*@C
    796:    SNESMonitorSetFromOptions - Sets a monitor function and viewer appropriate for the type indicated by the user

    798:    Collective on SNES

    800:    Input Parameters:
    801: +  snes - SNES object you wish to monitor
    802: .  name - the monitor type one is seeking
    803: .  help - message indicating what monitoring is done
    804: .  manual - manual page for the monitor
    805: .  monitor - the monitor function
    806: -  monitorsetup - a function that is called once ONLY if the user selected this monitor that may set additional features of the SNES or PetscViewer objects

    808:    Level: developer

    810: .seealso: PetscOptionsGetViewer(), PetscOptionsGetReal(), PetscOptionsHasName(), PetscOptionsGetString(),
    811:           PetscOptionsGetIntArray(), PetscOptionsGetRealArray(), PetscOptionsBool()
    812:           PetscOptionsInt(), PetscOptionsString(), PetscOptionsReal(), PetscOptionsBool(),
    813:           PetscOptionsName(), PetscOptionsBegin(), PetscOptionsEnd(), PetscOptionsHead(),
    814:           PetscOptionsStringArray(),PetscOptionsRealArray(), PetscOptionsScalar(),
    815:           PetscOptionsBoolGroupBegin(), PetscOptionsBoolGroup(), PetscOptionsBoolGroupEnd(),
    816:           PetscOptionsFList(), PetscOptionsEList()
    817: @*/
    818: PetscErrorCode  SNESMonitorSetFromOptions(SNES snes,const char name[],const char help[], const char manual[],PetscErrorCode (*monitor)(SNES,PetscInt,PetscReal,PetscViewerAndFormat*),PetscErrorCode (*monitorsetup)(SNES,PetscViewerAndFormat*))
    819: {
    820:   PetscErrorCode    ierr;
    821:   PetscViewer       viewer;
    822:   PetscViewerFormat format;
    823:   PetscBool         flg;

    826:   PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject) snes)->options,((PetscObject)snes)->prefix,name,&viewer,&format,&flg);
    827:   if (flg) {
    828:     PetscViewerAndFormat *vf;
    829:     PetscViewerAndFormatCreate(viewer,format,&vf);
    830:     PetscObjectDereference((PetscObject)viewer);
    831:     if (monitorsetup) {
    832:       (*monitorsetup)(snes,vf);
    833:     }
    834:     SNESMonitorSet(snes,(PetscErrorCode (*)(SNES,PetscInt,PetscReal,void*))monitor,vf,(PetscErrorCode (*)(void**))PetscViewerAndFormatDestroy);
    835:   }
    836:   return(0);
    837: }

    839: /*@
    840:    SNESSetFromOptions - Sets various SNES and KSP parameters from user options.

    842:    Collective on SNES

    844:    Input Parameter:
    845: .  snes - the SNES context

    847:    Options Database Keys:
    848: +  -snes_type <type> - newtonls, newtontr, ngmres, ncg, nrichardson, qn, vi, fas, SNESType for complete list
    849: .  -snes_stol - convergence tolerance in terms of the norm
    850:                 of the change in the solution between steps
    851: .  -snes_atol <abstol> - absolute tolerance of residual norm
    852: .  -snes_rtol <rtol> - relative decrease in tolerance norm from initial
    853: .  -snes_divergence_tolerance <divtol> - if the residual goes above divtol*rnorm0, exit with divergence
    854: .  -snes_force_iteration <force> - force SNESSolve() to take at least one iteration
    855: .  -snes_max_it <max_it> - maximum number of iterations
    856: .  -snes_max_funcs <max_funcs> - maximum number of function evaluations
    857: .  -snes_max_fail <max_fail> - maximum number of line search failures allowed before stopping, default is none
    858: .  -snes_max_linear_solve_fail - number of linear solver failures before SNESSolve() stops
    859: .  -snes_lag_preconditioner <lag> - how often preconditioner is rebuilt (use -1 to never rebuild)
    860: .  -snes_lag_preconditioner_persists <true,false> - retains the -snes_lag_preconditioner information across multiple SNESSolve()
    861: .  -snes_lag_jacobian <lag> - how often Jacobian is rebuilt (use -1 to never rebuild)
    862: .  -snes_lag_jacobian_persists <true,false> - retains the -snes_lag_jacobian information across multiple SNESSolve()
    863: .  -snes_trtol <trtol> - trust region tolerance
    864: .  -snes_no_convergence_test - skip convergence test in nonlinear
    865:                                solver; hence iterations will continue until max_it
    866:                                or some other criterion is reached. Saves expense
    867:                                of convergence test
    868: .  -snes_monitor [ascii][:filename][:viewer format] - prints residual norm at each iteration. if no filename given prints to stdout
    869: .  -snes_monitor_solution [ascii binary draw][:filename][:viewer format] - plots solution at each iteration
    870: .  -snes_monitor_residual [ascii binary draw][:filename][:viewer format] - plots residual (not its norm) at each iteration
    871: .  -snes_monitor_solution_update [ascii binary draw][:filename][:viewer format] - plots update to solution at each iteration
    872: .  -snes_monitor_lg_residualnorm - plots residual norm at each iteration
    873: .  -snes_monitor_lg_range - plots residual norm at each iteration
    874: .  -snes_fd - use finite differences to compute Jacobian; very slow, only for testing
    875: .  -snes_fd_color - use finite differences with coloring to compute Jacobian
    876: .  -snes_mf_ksp_monitor - if using matrix-free multiply then print h at each KSP iteration
    877: .  -snes_converged_reason - print the reason for convergence/divergence after each solve
    878: .  -npc_snes_type <type> - the SNES type to use as a nonlinear preconditioner
    879: .   -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one computed via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
    880: -   -snes_test_jacobian_view - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian.

    882:     Options Database for Eisenstat-Walker method:
    883: +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
    884: .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
    885: .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
    886: .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
    887: .  -snes_ksp_ew_gamma <gamma> - Sets gamma
    888: .  -snes_ksp_ew_alpha <alpha> - Sets alpha
    889: .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
    890: -  -snes_ksp_ew_threshold <threshold> - Sets threshold

    892:    Notes:
    893:    To see all options, run your program with the -help option or consult the users manual

    895:    Notes:
    896:       SNES supports three approaches for computing (approximate) Jacobians: user provided via SNESSetJacobian(), matrix free, and computing explictly with
    897:       finite differences and coloring using MatFDColoring. It is also possible to use automatic differentiation and the MatFDColoring object.

    899:    Level: beginner

    901: .seealso: SNESSetOptionsPrefix(), SNESResetFromOptions(), SNES, SNESCreate()
    902: @*/
    903: PetscErrorCode  SNESSetFromOptions(SNES snes)
    904: {
    905:   PetscBool      flg,pcset,persist,set;
    906:   PetscInt       i,indx,lag,grids;
    907:   const char     *deft        = SNESNEWTONLS;
    908:   const char     *convtests[] = {"default","skip","correct_pressure"};
    909:   SNESKSPEW      *kctx        = NULL;
    910:   char           type[256], monfilename[PETSC_MAX_PATH_LEN];
    912:   PCSide         pcside;
    913:   const char     *optionsprefix;

    917:   SNESRegisterAll();
    918:   PetscObjectOptionsBegin((PetscObject)snes);
    919:   if (((PetscObject)snes)->type_name) deft = ((PetscObject)snes)->type_name;
    920:   PetscOptionsFList("-snes_type","Nonlinear solver method","SNESSetType",SNESList,deft,type,256,&flg);
    921:   if (flg) {
    922:     SNESSetType(snes,type);
    923:   } else if (!((PetscObject)snes)->type_name) {
    924:     SNESSetType(snes,deft);
    925:   }
    926:   PetscOptionsReal("-snes_stol","Stop if step length less than","SNESSetTolerances",snes->stol,&snes->stol,NULL);
    927:   PetscOptionsReal("-snes_atol","Stop if function norm less than","SNESSetTolerances",snes->abstol,&snes->abstol,NULL);

    929:   PetscOptionsReal("-snes_rtol","Stop if decrease in function norm less than","SNESSetTolerances",snes->rtol,&snes->rtol,NULL);
    930:   PetscOptionsReal("-snes_divergence_tolerance","Stop if residual norm increases by this factor","SNESSetDivergenceTolerance",snes->divtol,&snes->divtol,NULL);
    931:   PetscOptionsInt("-snes_max_it","Maximum iterations","SNESSetTolerances",snes->max_its,&snes->max_its,NULL);
    932:   PetscOptionsInt("-snes_max_funcs","Maximum function evaluations","SNESSetTolerances",snes->max_funcs,&snes->max_funcs,NULL);
    933:   PetscOptionsInt("-snes_max_fail","Maximum nonlinear step failures","SNESSetMaxNonlinearStepFailures",snes->maxFailures,&snes->maxFailures,NULL);
    934:   PetscOptionsInt("-snes_max_linear_solve_fail","Maximum failures in linear solves allowed","SNESSetMaxLinearSolveFailures",snes->maxLinearSolveFailures,&snes->maxLinearSolveFailures,NULL);
    935:   PetscOptionsBool("-snes_error_if_not_converged","Generate error if solver does not converge","SNESSetErrorIfNotConverged",snes->errorifnotconverged,&snes->errorifnotconverged,NULL);
    936:   PetscOptionsBool("-snes_force_iteration","Force SNESSolve() to take at least one iteration","SNESSetForceIteration",snes->forceiteration,&snes->forceiteration,NULL);
    937:   PetscOptionsBool("-snes_check_jacobian_domain_error","Check Jacobian domain error after Jacobian evaluation","SNESCheckJacobianDomainError",snes->checkjacdomainerror,&snes->checkjacdomainerror,NULL);

    939:   PetscOptionsInt("-snes_lag_preconditioner","How often to rebuild preconditioner","SNESSetLagPreconditioner",snes->lagpreconditioner,&lag,&flg);
    940:   if (flg) {
    941:     if (lag == -1) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_USER,"Cannot set the lag to -1 from the command line since the preconditioner must be built as least once, perhaps you mean -2");
    942:     SNESSetLagPreconditioner(snes,lag);
    943:   }
    944:   PetscOptionsBool("-snes_lag_preconditioner_persists","Preconditioner lagging through multiple SNES solves","SNESSetLagPreconditionerPersists",snes->lagjac_persist,&persist,&flg);
    945:   if (flg) {
    946:     SNESSetLagPreconditionerPersists(snes,persist);
    947:   }
    948:   PetscOptionsInt("-snes_lag_jacobian","How often to rebuild Jacobian","SNESSetLagJacobian",snes->lagjacobian,&lag,&flg);
    949:   if (flg) {
    950:     if (lag == -1) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_USER,"Cannot set the lag to -1 from the command line since the Jacobian must be built as least once, perhaps you mean -2");
    951:     SNESSetLagJacobian(snes,lag);
    952:   }
    953:   PetscOptionsBool("-snes_lag_jacobian_persists","Jacobian lagging through multiple SNES solves","SNESSetLagJacobianPersists",snes->lagjac_persist,&persist,&flg);
    954:   if (flg) {
    955:     SNESSetLagJacobianPersists(snes,persist);
    956:   }

    958:   PetscOptionsInt("-snes_grid_sequence","Use grid sequencing to generate initial guess","SNESSetGridSequence",snes->gridsequence,&grids,&flg);
    959:   if (flg) {
    960:     SNESSetGridSequence(snes,grids);
    961:   }

    963:   PetscOptionsEList("-snes_convergence_test","Convergence test","SNESSetConvergenceTest",convtests,sizeof(convtests)/sizeof(char*),"default",&indx,&flg);
    964:   if (flg) {
    965:     switch (indx) {
    966:     case 0: SNESSetConvergenceTest(snes,SNESConvergedDefault,NULL,NULL); break;
    967:     case 1: SNESSetConvergenceTest(snes,SNESConvergedSkip,NULL,NULL); break;
    968:     case 2: SNESSetConvergenceTest(snes,SNESConvergedCorrectPressure,NULL,NULL); break;
    969:     }
    970:   }

    972:   PetscOptionsEList("-snes_norm_schedule","SNES Norm schedule","SNESSetNormSchedule",SNESNormSchedules,5,"function",&indx,&flg);
    973:   if (flg) { SNESSetNormSchedule(snes,(SNESNormSchedule)indx); }

    975:   PetscOptionsEList("-snes_function_type","SNES Norm schedule","SNESSetFunctionType",SNESFunctionTypes,2,"unpreconditioned",&indx,&flg);
    976:   if (flg) { SNESSetFunctionType(snes,(SNESFunctionType)indx); }

    978:   kctx = (SNESKSPEW*)snes->kspconvctx;

    980:   PetscOptionsBool("-snes_ksp_ew","Use Eisentat-Walker linear system convergence test","SNESKSPSetUseEW",snes->ksp_ewconv,&snes->ksp_ewconv,NULL);

    982:   PetscOptionsInt("-snes_ksp_ew_version","Version 1, 2 or 3","SNESKSPSetParametersEW",kctx->version,&kctx->version,NULL);
    983:   PetscOptionsReal("-snes_ksp_ew_rtol0","0 <= rtol0 < 1","SNESKSPSetParametersEW",kctx->rtol_0,&kctx->rtol_0,NULL);
    984:   PetscOptionsReal("-snes_ksp_ew_rtolmax","0 <= rtolmax < 1","SNESKSPSetParametersEW",kctx->rtol_max,&kctx->rtol_max,NULL);
    985:   PetscOptionsReal("-snes_ksp_ew_gamma","0 <= gamma <= 1","SNESKSPSetParametersEW",kctx->gamma,&kctx->gamma,NULL);
    986:   PetscOptionsReal("-snes_ksp_ew_alpha","1 < alpha <= 2","SNESKSPSetParametersEW",kctx->alpha,&kctx->alpha,NULL);
    987:   PetscOptionsReal("-snes_ksp_ew_alpha2","alpha2","SNESKSPSetParametersEW",kctx->alpha2,&kctx->alpha2,NULL);
    988:   PetscOptionsReal("-snes_ksp_ew_threshold","0 < threshold < 1","SNESKSPSetParametersEW",kctx->threshold,&kctx->threshold,NULL);

    990:   flg  = PETSC_FALSE;
    991:   PetscOptionsBool("-snes_monitor_cancel","Remove all monitors","SNESMonitorCancel",flg,&flg,&set);
    992:   if (set && flg) {SNESMonitorCancel(snes);}

    994:   SNESMonitorSetFromOptions(snes,"-snes_monitor","Monitor norm of function","SNESMonitorDefault",SNESMonitorDefault,NULL);
    995:   SNESMonitorSetFromOptions(snes,"-snes_monitor_short","Monitor norm of function with fewer digits","SNESMonitorDefaultShort",SNESMonitorDefaultShort,NULL);
    996:   SNESMonitorSetFromOptions(snes,"-snes_monitor_range","Monitor range of elements of function","SNESMonitorRange",SNESMonitorRange,NULL);

    998:   SNESMonitorSetFromOptions(snes,"-snes_monitor_ratio","Monitor ratios of the norm of function for consecutive steps","SNESMonitorRatio",SNESMonitorRatio,SNESMonitorRatioSetUp);
    999:   SNESMonitorSetFromOptions(snes,"-snes_monitor_field","Monitor norm of function (split into fields)","SNESMonitorDefaultField",SNESMonitorDefaultField,NULL);
    1000:   SNESMonitorSetFromOptions(snes,"-snes_monitor_solution","View solution at each iteration","SNESMonitorSolution",SNESMonitorSolution,NULL);
    1001:   SNESMonitorSetFromOptions(snes,"-snes_monitor_solution_update","View correction at each iteration","SNESMonitorSolutionUpdate",SNESMonitorSolutionUpdate,NULL);
    1002:   SNESMonitorSetFromOptions(snes,"-snes_monitor_residual","View residual at each iteration","SNESMonitorResidual",SNESMonitorResidual,NULL);
    1003:   SNESMonitorSetFromOptions(snes,"-snes_monitor_jacupdate_spectrum","Print the change in the spectrum of the Jacobian","SNESMonitorJacUpdateSpectrum",SNESMonitorJacUpdateSpectrum,NULL);
    1004:   SNESMonitorSetFromOptions(snes,"-snes_monitor_fields","Monitor norm of function per field","SNESMonitorSet",SNESMonitorFields,NULL);

    1006:   PetscOptionsString("-snes_monitor_python","Use Python function","SNESMonitorSet",NULL,monfilename,sizeof(monfilename),&flg);
    1007:   if (flg) {PetscPythonMonitorSet((PetscObject)snes,monfilename);}

    1009:   flg  = PETSC_FALSE;
    1010:   PetscOptionsBool("-snes_monitor_lg_range","Plot function range at each iteration","SNESMonitorLGRange",flg,&flg,NULL);
    1011:   if (flg) {
    1012:     PetscViewer ctx;

    1014:     PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),NULL,NULL,PETSC_DECIDE,PETSC_DECIDE,400,300,&ctx);
    1015:     SNESMonitorSet(snes,SNESMonitorLGRange,ctx,(PetscErrorCode (*)(void**))PetscViewerDestroy);
    1016:   }

    1018:   flg  = PETSC_FALSE;
    1019:   PetscOptionsBool("-snes_converged_reason_view_cancel","Remove all converged reason viewers","SNESConvergedReasonViewCancel",flg,&flg,&set);
    1020:   if (set && flg) {SNESConvergedReasonViewCancel(snes);}

    1022:   flg  = PETSC_FALSE;
    1023:   PetscOptionsBool("-snes_fd","Use finite differences (slow) to compute Jacobian","SNESComputeJacobianDefault",flg,&flg,NULL);
    1024:   if (flg) {
    1025:     void    *functx;
    1026:     DM      dm;
    1027:     DMSNES  sdm;
    1028:     SNESGetDM(snes,&dm);
    1029:     DMGetDMSNES(dm,&sdm);
    1030:     sdm->jacobianctx = NULL;
    1031:     SNESGetFunction(snes,NULL,NULL,&functx);
    1032:     SNESSetJacobian(snes,snes->jacobian,snes->jacobian_pre,SNESComputeJacobianDefault,functx);
    1033:     PetscInfo(snes,"Setting default finite difference Jacobian matrix\n");
    1034:   }

    1036:   flg  = PETSC_FALSE;
    1037:   PetscOptionsBool("-snes_fd_function","Use finite differences (slow) to compute function from user objective","SNESObjectiveComputeFunctionDefaultFD",flg,&flg,NULL);
    1038:   if (flg) {
    1039:     SNESSetFunction(snes,NULL,SNESObjectiveComputeFunctionDefaultFD,NULL);
    1040:   }

    1042:   flg  = PETSC_FALSE;
    1043:   PetscOptionsBool("-snes_fd_color","Use finite differences with coloring to compute Jacobian","SNESComputeJacobianDefaultColor",flg,&flg,NULL);
    1044:   if (flg) {
    1045:     DM             dm;
    1046:     DMSNES         sdm;
    1047:     SNESGetDM(snes,&dm);
    1048:     DMGetDMSNES(dm,&sdm);
    1049:     sdm->jacobianctx = NULL;
    1050:     SNESSetJacobian(snes,snes->jacobian,snes->jacobian_pre,SNESComputeJacobianDefaultColor,NULL);
    1051:     PetscInfo(snes,"Setting default finite difference coloring Jacobian matrix\n");
    1052:   }

    1054:   flg  = PETSC_FALSE;
    1055:   PetscOptionsBool("-snes_mf_operator","Use a Matrix-Free Jacobian with user-provided preconditioner matrix","SNESSetUseMatrixFree",PETSC_FALSE,&snes->mf_operator,&flg);
    1056:   if (flg && snes->mf_operator) {
    1057:     snes->mf_operator = PETSC_TRUE;
    1058:     snes->mf          = PETSC_TRUE;
    1059:   }
    1060:   flg  = PETSC_FALSE;
    1061:   PetscOptionsBool("-snes_mf","Use a Matrix-Free Jacobian with no preconditioner matrix","SNESSetUseMatrixFree",PETSC_FALSE,&snes->mf,&flg);
    1062:   if (!flg && snes->mf_operator) snes->mf = PETSC_TRUE;
    1063:   PetscOptionsInt("-snes_mf_version","Matrix-Free routines version 1 or 2","None",snes->mf_version,&snes->mf_version,NULL);

    1065:   flg  = PETSC_FALSE;
    1066:   SNESGetNPCSide(snes,&pcside);
    1067:   PetscOptionsEnum("-snes_npc_side","SNES nonlinear preconditioner side","SNESSetNPCSide",PCSides,(PetscEnum)pcside,(PetscEnum*)&pcside,&flg);
    1068:   if (flg) {SNESSetNPCSide(snes,pcside);}

    1070: #if defined(PETSC_HAVE_SAWS)
    1071:   /*
    1072:     Publish convergence information using SAWs
    1073:   */
    1074:   flg  = PETSC_FALSE;
    1075:   PetscOptionsBool("-snes_monitor_saws","Publish SNES progress using SAWs","SNESMonitorSet",flg,&flg,NULL);
    1076:   if (flg) {
    1077:     void *ctx;
    1078:     SNESMonitorSAWsCreate(snes,&ctx);
    1079:     SNESMonitorSet(snes,SNESMonitorSAWs,ctx,SNESMonitorSAWsDestroy);
    1080:   }
    1081: #endif
    1082: #if defined(PETSC_HAVE_SAWS)
    1083:   {
    1084:   PetscBool set;
    1085:   flg  = PETSC_FALSE;
    1086:   PetscOptionsBool("-snes_saws_block","Block for SAWs at end of SNESSolve","PetscObjectSAWsBlock",((PetscObject)snes)->amspublishblock,&flg,&set);
    1087:   if (set) {
    1088:     PetscObjectSAWsSetBlock((PetscObject)snes,flg);
    1089:   }
    1090:   }
    1091: #endif

    1093:   for (i = 0; i < numberofsetfromoptions; i++) {
    1094:     (*othersetfromoptions[i])(snes);
    1095:   }

    1097:   if (snes->ops->setfromoptions) {
    1098:     (*snes->ops->setfromoptions)(PetscOptionsObject,snes);
    1099:   }

    1101:   /* process any options handlers added with PetscObjectAddOptionsHandler() */
    1102:   PetscObjectProcessOptionsHandlers(PetscOptionsObject,(PetscObject)snes);
    1103:   PetscOptionsEnd();

    1105:   if (snes->linesearch) {
    1106:     SNESGetLineSearch(snes, &snes->linesearch);
    1107:     SNESLineSearchSetFromOptions(snes->linesearch);
    1108:   }

    1110:   if (snes->usesksp) {
    1111:     if (!snes->ksp) {SNESGetKSP(snes,&snes->ksp);}
    1112:     KSPSetOperators(snes->ksp,snes->jacobian,snes->jacobian_pre);
    1113:     KSPSetFromOptions(snes->ksp);
    1114:   }

    1116:   /* if user has set the SNES NPC type via options database, create it. */
    1117:   SNESGetOptionsPrefix(snes, &optionsprefix);
    1118:   PetscOptionsHasName(((PetscObject)snes)->options,optionsprefix, "-npc_snes_type", &pcset);
    1119:   if (pcset && (!snes->npc)) {
    1120:     SNESGetNPC(snes, &snes->npc);
    1121:   }
    1122:   if (snes->npc) {
    1123:     SNESSetFromOptions(snes->npc);
    1124:   }
    1125:   snes->setfromoptionscalled++;
    1126:   return(0);
    1127: }

    1129: /*@
    1130:    SNESResetFromOptions - Sets various SNES and KSP parameters from user options ONLY if the SNES was previously set from options

    1132:    Collective on SNES

    1134:    Input Parameter:
    1135: .  snes - the SNES context

    1137:    Level: beginner

    1139: .seealso: SNESSetFromOptions(), SNESSetOptionsPrefix()
    1140: @*/
    1141: PetscErrorCode SNESResetFromOptions(SNES snes)
    1142: {

    1146:   if (snes->setfromoptionscalled) {SNESSetFromOptions(snes);}
    1147:   return(0);
    1148: }

    1150: /*@C
    1151:    SNESSetComputeApplicationContext - Sets an optional function to compute a user-defined context for
    1152:    the nonlinear solvers.

    1154:    Logically Collective on SNES

    1156:    Input Parameters:
    1157: +  snes - the SNES context
    1158: .  compute - function to compute the context
    1159: -  destroy - function to destroy the context

    1161:    Level: intermediate

    1163:    Notes:
    1164:    This function is currently not available from Fortran.

    1166: .seealso: SNESGetApplicationContext(), SNESSetComputeApplicationContext(), SNESGetApplicationContext()
    1167: @*/
    1168: PetscErrorCode  SNESSetComputeApplicationContext(SNES snes,PetscErrorCode (*compute)(SNES,void**),PetscErrorCode (*destroy)(void**))
    1169: {
    1172:   snes->ops->usercompute = compute;
    1173:   snes->ops->userdestroy = destroy;
    1174:   return(0);
    1175: }

    1177: /*@
    1178:    SNESSetApplicationContext - Sets the optional user-defined context for
    1179:    the nonlinear solvers.

    1181:    Logically Collective on SNES

    1183:    Input Parameters:
    1184: +  snes - the SNES context
    1185: -  usrP - optional user context

    1187:    Level: intermediate

    1189:    Fortran Notes:
    1190:     To use this from Fortran you must write a Fortran interface definition for this
    1191:     function that tells Fortran the Fortran derived data type that you are passing in as the ctx argument.

    1193: .seealso: SNESGetApplicationContext()
    1194: @*/
    1195: PetscErrorCode  SNESSetApplicationContext(SNES snes,void *usrP)
    1196: {
    1198:   KSP            ksp;

    1202:   SNESGetKSP(snes,&ksp);
    1203:   KSPSetApplicationContext(ksp,usrP);
    1204:   snes->user = usrP;
    1205:   return(0);
    1206: }

    1208: /*@
    1209:    SNESGetApplicationContext - Gets the user-defined context for the
    1210:    nonlinear solvers.

    1212:    Not Collective

    1214:    Input Parameter:
    1215: .  snes - SNES context

    1217:    Output Parameter:
    1218: .  usrP - user context

    1220:    Fortran Notes:
    1221:     To use this from Fortran you must write a Fortran interface definition for this
    1222:     function that tells Fortran the Fortran derived data type that you are passing in as the ctx argument.

    1224:    Level: intermediate

    1226: .seealso: SNESSetApplicationContext()
    1227: @*/
    1228: PetscErrorCode  SNESGetApplicationContext(SNES snes,void *usrP)
    1229: {
    1232:   *(void**)usrP = snes->user;
    1233:   return(0);
    1234: }

    1236: /*@
    1237:    SNESSetUseMatrixFree - indicates that SNES should use matrix free finite difference matrix vector products internally to apply the Jacobian.

    1239:    Collective on SNES

    1241:    Input Parameters:
    1242: +  snes - SNES context
    1243: .  mf_operator - use matrix-free only for the Amat used by SNESSetJacobian(), this means the user provided Pmat will continue to be used
    1244: -  mf - use matrix-free for both the Amat and Pmat used by SNESSetJacobian(), both the Amat and Pmat set in SNESSetJacobian() will be ignored

    1246:    Options Database:
    1247: + -snes_mf - use matrix free for both the mat and pmat operator
    1248: . -snes_mf_operator - use matrix free only for the mat operator
    1249: . -snes_fd_color - compute the Jacobian via coloring and finite differences.
    1250: - -snes_fd - compute the Jacobian via finite differences (slow)

    1252:    Level: intermediate

    1254:    Notes:
    1255:       SNES supports three approaches for computing (approximate) Jacobians: user provided via SNESSetJacobian(), matrix free, and computing explictly with
    1256:       finite differences and coloring using MatFDColoring. It is also possible to use automatic differentiation and the MatFDColoring object.

    1258: .seealso:   SNESGetUseMatrixFree(), MatCreateSNESMF(), SNESComputeJacobianDefaultColor()
    1259: @*/
    1260: PetscErrorCode  SNESSetUseMatrixFree(SNES snes,PetscBool mf_operator,PetscBool mf)
    1261: {
    1266:   snes->mf          = mf_operator ? PETSC_TRUE : mf;
    1267:   snes->mf_operator = mf_operator;
    1268:   return(0);
    1269: }

    1271: /*@
    1272:    SNESGetUseMatrixFree - indicates if the SNES uses matrix free finite difference matrix vector products to apply the Jacobian.

    1274:    Collective on SNES

    1276:    Input Parameter:
    1277: .  snes - SNES context

    1279:    Output Parameters:
    1280: +  mf_operator - use matrix-free only for the Amat used by SNESSetJacobian(), this means the user provided Pmat will continue to be used
    1281: -  mf - use matrix-free for both the Amat and Pmat used by SNESSetJacobian(), both the Amat and Pmat set in SNESSetJacobian() will be ignored

    1283:    Options Database:
    1284: + -snes_mf - use matrix free for both the mat and pmat operator
    1285: - -snes_mf_operator - use matrix free only for the mat operator

    1287:    Level: intermediate

    1289: .seealso:   SNESSetUseMatrixFree(), MatCreateSNESMF()
    1290: @*/
    1291: PetscErrorCode  SNESGetUseMatrixFree(SNES snes,PetscBool *mf_operator,PetscBool *mf)
    1292: {
    1295:   if (mf)          *mf          = snes->mf;
    1296:   if (mf_operator) *mf_operator = snes->mf_operator;
    1297:   return(0);
    1298: }

    1300: /*@
    1301:    SNESGetIterationNumber - Gets the number of nonlinear iterations completed
    1302:    at this time.

    1304:    Not Collective

    1306:    Input Parameter:
    1307: .  snes - SNES context

    1309:    Output Parameter:
    1310: .  iter - iteration number

    1312:    Notes:
    1313:    For example, during the computation of iteration 2 this would return 1.

    1315:    This is useful for using lagged Jacobians (where one does not recompute the
    1316:    Jacobian at each SNES iteration). For example, the code
    1317: .vb
    1318:       SNESGetIterationNumber(snes,&it);
    1319:       if (!(it % 2)) {
    1320:         [compute Jacobian here]
    1321:       }
    1322: .ve
    1323:    can be used in your ComputeJacobian() function to cause the Jacobian to be
    1324:    recomputed every second SNES iteration.

    1326:    After the SNES solve is complete this will return the number of nonlinear iterations used.

    1328:    Level: intermediate

    1330: .seealso:   SNESGetLinearSolveIterations()
    1331: @*/
    1332: PetscErrorCode  SNESGetIterationNumber(SNES snes,PetscInt *iter)
    1333: {
    1337:   *iter = snes->iter;
    1338:   return(0);
    1339: }

    1341: /*@
    1342:    SNESSetIterationNumber - Sets the current iteration number.

    1344:    Not Collective

    1346:    Input Parameter:
    1347: +  snes - SNES context
    1348: -  iter - iteration number

    1350:    Level: developer

    1352: .seealso:   SNESGetLinearSolveIterations()
    1353: @*/
    1354: PetscErrorCode  SNESSetIterationNumber(SNES snes,PetscInt iter)
    1355: {

    1360:   PetscObjectSAWsTakeAccess((PetscObject)snes);
    1361:   snes->iter = iter;
    1362:   PetscObjectSAWsGrantAccess((PetscObject)snes);
    1363:   return(0);
    1364: }

    1366: /*@
    1367:    SNESGetNonlinearStepFailures - Gets the number of unsuccessful steps
    1368:    attempted by the nonlinear solver.

    1370:    Not Collective

    1372:    Input Parameter:
    1373: .  snes - SNES context

    1375:    Output Parameter:
    1376: .  nfails - number of unsuccessful steps attempted

    1378:    Notes:
    1379:    This counter is reset to zero for each successive call to SNESSolve().

    1381:    Level: intermediate

    1383: .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
    1384:           SNESSetMaxNonlinearStepFailures(), SNESGetMaxNonlinearStepFailures()
    1385: @*/
    1386: PetscErrorCode  SNESGetNonlinearStepFailures(SNES snes,PetscInt *nfails)
    1387: {
    1391:   *nfails = snes->numFailures;
    1392:   return(0);
    1393: }

    1395: /*@
    1396:    SNESSetMaxNonlinearStepFailures - Sets the maximum number of unsuccessful steps
    1397:    attempted by the nonlinear solver before it gives up.

    1399:    Not Collective

    1401:    Input Parameters:
    1402: +  snes     - SNES context
    1403: -  maxFails - maximum of unsuccessful steps

    1405:    Level: intermediate

    1407: .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
    1408:           SNESGetMaxNonlinearStepFailures(), SNESGetNonlinearStepFailures()
    1409: @*/
    1410: PetscErrorCode  SNESSetMaxNonlinearStepFailures(SNES snes, PetscInt maxFails)
    1411: {
    1414:   snes->maxFailures = maxFails;
    1415:   return(0);
    1416: }

    1418: /*@
    1419:    SNESGetMaxNonlinearStepFailures - Gets the maximum number of unsuccessful steps
    1420:    attempted by the nonlinear solver before it gives up.

    1422:    Not Collective

    1424:    Input Parameter:
    1425: .  snes     - SNES context

    1427:    Output Parameter:
    1428: .  maxFails - maximum of unsuccessful steps

    1430:    Level: intermediate

    1432: .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
    1433:           SNESSetMaxNonlinearStepFailures(), SNESGetNonlinearStepFailures()

    1435: @*/
    1436: PetscErrorCode  SNESGetMaxNonlinearStepFailures(SNES snes, PetscInt *maxFails)
    1437: {
    1441:   *maxFails = snes->maxFailures;
    1442:   return(0);
    1443: }

    1445: /*@
    1446:    SNESGetNumberFunctionEvals - Gets the number of user provided function evaluations
    1447:      done by SNES.

    1449:    Not Collective

    1451:    Input Parameter:
    1452: .  snes     - SNES context

    1454:    Output Parameter:
    1455: .  nfuncs - number of evaluations

    1457:    Level: intermediate

    1459:    Notes:
    1460:     Reset every time SNESSolve is called unless SNESSetCountersReset() is used.

    1462: .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(), SNESSetCountersReset()
    1463: @*/
    1464: PetscErrorCode  SNESGetNumberFunctionEvals(SNES snes, PetscInt *nfuncs)
    1465: {
    1469:   *nfuncs = snes->nfuncs;
    1470:   return(0);
    1471: }

    1473: /*@
    1474:    SNESGetLinearSolveFailures - Gets the number of failed (non-converged)
    1475:    linear solvers.

    1477:    Not Collective

    1479:    Input Parameter:
    1480: .  snes - SNES context

    1482:    Output Parameter:
    1483: .  nfails - number of failed solves

    1485:    Level: intermediate

    1487:    Options Database Keys:
    1488: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

    1490:    Notes:
    1491:    This counter is reset to zero for each successive call to SNESSolve().

    1493: .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures()
    1494: @*/
    1495: PetscErrorCode  SNESGetLinearSolveFailures(SNES snes,PetscInt *nfails)
    1496: {
    1500:   *nfails = snes->numLinearSolveFailures;
    1501:   return(0);
    1502: }

    1504: /*@
    1505:    SNESSetMaxLinearSolveFailures - the number of failed linear solve attempts
    1506:    allowed before SNES returns with a diverged reason of SNES_DIVERGED_LINEAR_SOLVE

    1508:    Logically Collective on SNES

    1510:    Input Parameters:
    1511: +  snes     - SNES context
    1512: -  maxFails - maximum allowed linear solve failures

    1514:    Level: intermediate

    1516:    Options Database Keys:
    1517: . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated

    1519:    Notes:
    1520:     By default this is 0; that is SNES returns on the first failed linear solve

    1522: .seealso: SNESGetLinearSolveFailures(), SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations()
    1523: @*/
    1524: PetscErrorCode  SNESSetMaxLinearSolveFailures(SNES snes, PetscInt maxFails)
    1525: {
    1529:   snes->maxLinearSolveFailures = maxFails;
    1530:   return(0);
    1531: }

    1533: /*@
    1534:    SNESGetMaxLinearSolveFailures - gets the maximum number of linear solve failures that
    1535:      are allowed before SNES terminates

    1537:    Not Collective

    1539:    Input Parameter:
    1540: .  snes     - SNES context

    1542:    Output Parameter:
    1543: .  maxFails - maximum of unsuccessful solves allowed

    1545:    Level: intermediate

    1547:    Notes:
    1548:     By default this is 1; that is SNES returns on the first failed linear solve

    1550: .seealso: SNESGetLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(),
    1551: @*/
    1552: PetscErrorCode  SNESGetMaxLinearSolveFailures(SNES snes, PetscInt *maxFails)
    1553: {
    1557:   *maxFails = snes->maxLinearSolveFailures;
    1558:   return(0);
    1559: }

    1561: /*@
    1562:    SNESGetLinearSolveIterations - Gets the total number of linear iterations
    1563:    used by the nonlinear solver.

    1565:    Not Collective

    1567:    Input Parameter:
    1568: .  snes - SNES context

    1570:    Output Parameter:
    1571: .  lits - number of linear iterations

    1573:    Notes:
    1574:    This counter is reset to zero for each successive call to SNESSolve() unless SNESSetCountersReset() is used.

    1576:    If the linear solver fails inside the SNESSolve() the iterations for that call to the linear solver are not included. If you wish to count them
    1577:    then call KSPGetIterationNumber() after the failed solve.

    1579:    Level: intermediate

    1581: .seealso:  SNESGetIterationNumber(), SNESGetLinearSolveFailures(), SNESGetMaxLinearSolveFailures(), SNESSetCountersReset()
    1582: @*/
    1583: PetscErrorCode  SNESGetLinearSolveIterations(SNES snes,PetscInt *lits)
    1584: {
    1588:   *lits = snes->linear_its;
    1589:   return(0);
    1590: }

    1592: /*@
    1593:    SNESSetCountersReset - Sets whether or not the counters for linear iterations and function evaluations
    1594:    are reset every time SNESSolve() is called.

    1596:    Logically Collective on SNES

    1598:    Input Parameter:
    1599: +  snes - SNES context
    1600: -  reset - whether to reset the counters or not

    1602:    Notes:
    1603:    This defaults to PETSC_TRUE

    1605:    Level: developer

    1607: .seealso:  SNESGetNumberFunctionEvals(), SNESGetLinearSolveIterations(), SNESGetNPC()
    1608: @*/
    1609: PetscErrorCode  SNESSetCountersReset(SNES snes,PetscBool reset)
    1610: {
    1614:   snes->counters_reset = reset;
    1615:   return(0);
    1616: }

    1619: /*@
    1620:    SNESSetKSP - Sets a KSP context for the SNES object to use

    1622:    Not Collective, but the SNES and KSP objects must live on the same MPI_Comm

    1624:    Input Parameters:
    1625: +  snes - the SNES context
    1626: -  ksp - the KSP context

    1628:    Notes:
    1629:    The SNES object already has its KSP object, you can obtain with SNESGetKSP()
    1630:    so this routine is rarely needed.

    1632:    The KSP object that is already in the SNES object has its reference count
    1633:    decreased by one.

    1635:    Level: developer

    1637: .seealso: KSPGetPC(), SNESCreate(), KSPCreate(), SNESSetKSP()
    1638: @*/
    1639: PetscErrorCode  SNESSetKSP(SNES snes,KSP ksp)
    1640: {

    1647:   PetscObjectReference((PetscObject)ksp);
    1648:   if (snes->ksp) {PetscObjectDereference((PetscObject)snes->ksp);}
    1649:   snes->ksp = ksp;
    1650:   return(0);
    1651: }

    1653: /* -----------------------------------------------------------*/
    1654: /*@
    1655:    SNESCreate - Creates a nonlinear solver context.

    1657:    Collective

    1659:    Input Parameters:
    1660: .  comm - MPI communicator

    1662:    Output Parameter:
    1663: .  outsnes - the new SNES context

    1665:    Options Database Keys:
    1666: +   -snes_mf - Activates default matrix-free Jacobian-vector products,
    1667:                and no preconditioning matrix
    1668: .   -snes_mf_operator - Activates default matrix-free Jacobian-vector
    1669:                products, and a user-provided preconditioning matrix
    1670:                as set by SNESSetJacobian()
    1671: -   -snes_fd - Uses (slow!) finite differences to compute Jacobian

    1673:    Level: beginner

    1675:    Developer Notes:
    1676:     SNES always creates a KSP object even though many SNES methods do not use it. This is
    1677:                     unfortunate and should be fixed at some point. The flag snes->usesksp indicates if the
    1678:                     particular method does use KSP and regulates if the information about the KSP is printed
    1679:                     in SNESView(). TSSetFromOptions() does call SNESSetFromOptions() which can lead to users being confused
    1680:                     by help messages about meaningless SNES options.

    1682:                     SNES always creates the snes->kspconvctx even though it is used by only one type. This should
    1683:                     be fixed.

    1685: .seealso: SNESSolve(), SNESDestroy(), SNES, SNESSetLagPreconditioner(), SNESSetLagJacobian()

    1687: @*/
    1688: PetscErrorCode  SNESCreate(MPI_Comm comm,SNES *outsnes)
    1689: {
    1691:   SNES           snes;
    1692:   SNESKSPEW      *kctx;

    1696:   *outsnes = NULL;
    1697:   SNESInitializePackage();

    1699:   PetscHeaderCreate(snes,SNES_CLASSID,"SNES","Nonlinear solver","SNES",comm,SNESDestroy,SNESView);

    1701:   snes->ops->converged    = SNESConvergedDefault;
    1702:   snes->usesksp           = PETSC_TRUE;
    1703:   snes->tolerancesset     = PETSC_FALSE;
    1704:   snes->max_its           = 50;
    1705:   snes->max_funcs         = 10000;
    1706:   snes->norm              = 0.0;
    1707:   snes->xnorm             = 0.0;
    1708:   snes->ynorm             = 0.0;
    1709:   snes->normschedule      = SNES_NORM_ALWAYS;
    1710:   snes->functype          = SNES_FUNCTION_DEFAULT;
    1711: #if defined(PETSC_USE_REAL_SINGLE)
    1712:   snes->rtol              = 1.e-5;
    1713: #else
    1714:   snes->rtol              = 1.e-8;
    1715: #endif
    1716:   snes->ttol              = 0.0;
    1717: #if defined(PETSC_USE_REAL_SINGLE)
    1718:   snes->abstol            = 1.e-25;
    1719: #else
    1720:   snes->abstol            = 1.e-50;
    1721: #endif
    1722: #if defined(PETSC_USE_REAL_SINGLE)
    1723:   snes->stol              = 1.e-5;
    1724: #else
    1725:   snes->stol              = 1.e-8;
    1726: #endif
    1727: #if defined(PETSC_USE_REAL_SINGLE)
    1728:   snes->deltatol          = 1.e-6;
    1729: #else
    1730:   snes->deltatol          = 1.e-12;
    1731: #endif
    1732:   snes->divtol            = 1.e4;
    1733:   snes->rnorm0            = 0;
    1734:   snes->nfuncs            = 0;
    1735:   snes->numFailures       = 0;
    1736:   snes->maxFailures       = 1;
    1737:   snes->linear_its        = 0;
    1738:   snes->lagjacobian       = 1;
    1739:   snes->jac_iter          = 0;
    1740:   snes->lagjac_persist    = PETSC_FALSE;
    1741:   snes->lagpreconditioner = 1;
    1742:   snes->pre_iter          = 0;
    1743:   snes->lagpre_persist    = PETSC_FALSE;
    1744:   snes->numbermonitors    = 0;
    1745:   snes->numberreasonviews = 0;
    1746:   snes->data              = NULL;
    1747:   snes->setupcalled       = PETSC_FALSE;
    1748:   snes->ksp_ewconv        = PETSC_FALSE;
    1749:   snes->nwork             = 0;
    1750:   snes->work              = NULL;
    1751:   snes->nvwork            = 0;
    1752:   snes->vwork             = NULL;
    1753:   snes->conv_hist_len     = 0;
    1754:   snes->conv_hist_max     = 0;
    1755:   snes->conv_hist         = NULL;
    1756:   snes->conv_hist_its     = NULL;
    1757:   snes->conv_hist_reset   = PETSC_TRUE;
    1758:   snes->counters_reset    = PETSC_TRUE;
    1759:   snes->vec_func_init_set = PETSC_FALSE;
    1760:   snes->reason            = SNES_CONVERGED_ITERATING;
    1761:   snes->npcside           = PC_RIGHT;
    1762:   snes->setfromoptionscalled = 0;

    1764:   snes->mf          = PETSC_FALSE;
    1765:   snes->mf_operator = PETSC_FALSE;
    1766:   snes->mf_version  = 1;

    1768:   snes->numLinearSolveFailures = 0;
    1769:   snes->maxLinearSolveFailures = 1;

    1771:   snes->vizerotolerance = 1.e-8;
    1772:   snes->checkjacdomainerror = PetscDefined(USE_DEBUG) ? PETSC_TRUE : PETSC_FALSE;

    1774:   /* Set this to true if the implementation of SNESSolve_XXX does compute the residual at the final solution. */
    1775:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

    1777:   /* Create context to compute Eisenstat-Walker relative tolerance for KSP */
    1778:   PetscNewLog(snes,&kctx);

    1780:   snes->kspconvctx  = (void*)kctx;
    1781:   kctx->version     = 2;
    1782:   kctx->rtol_0      = .3; /* Eisenstat and Walker suggest rtol_0=.5, but
    1783:                              this was too large for some test cases */
    1784:   kctx->rtol_last   = 0.0;
    1785:   kctx->rtol_max    = .9;
    1786:   kctx->gamma       = 1.0;
    1787:   kctx->alpha       = .5*(1.0 + PetscSqrtReal(5.0));
    1788:   kctx->alpha2      = kctx->alpha;
    1789:   kctx->threshold   = .1;
    1790:   kctx->lresid_last = 0.0;
    1791:   kctx->norm_last   = 0.0;

    1793:   *outsnes = snes;
    1794:   return(0);
    1795: }

    1797: /*MC
    1798:     SNESFunction - Functional form used to convey the nonlinear function to be solved by SNES

    1800:      Synopsis:
    1801:      #include "petscsnes.h"
    1802:      PetscErrorCode SNESFunction(SNES snes,Vec x,Vec f,void *ctx);

    1804:      Collective on snes

    1806:      Input Parameters:
    1807: +     snes - the SNES context
    1808: .     x    - state at which to evaluate residual
    1809: -     ctx     - optional user-defined function context, passed in with SNESSetFunction()

    1811:      Output Parameter:
    1812: .     f  - vector to put residual (function value)

    1814:    Level: intermediate

    1816: .seealso:   SNESSetFunction(), SNESGetFunction()
    1817: M*/

    1819: /*@C
    1820:    SNESSetFunction - Sets the function evaluation routine and function
    1821:    vector for use by the SNES routines in solving systems of nonlinear
    1822:    equations.

    1824:    Logically Collective on SNES

    1826:    Input Parameters:
    1827: +  snes - the SNES context
    1828: .  r - vector to store function value
    1829: .  f - function evaluation routine; see SNESFunction for calling sequence details
    1830: -  ctx - [optional] user-defined context for private data for the
    1831:          function evaluation routine (may be NULL)

    1833:    Notes:
    1834:    The Newton-like methods typically solve linear systems of the form
    1835: $      f'(x) x = -f(x),
    1836:    where f'(x) denotes the Jacobian matrix and f(x) is the function.

    1838:    Level: beginner

    1840: .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetPicard(), SNESFunction
    1841: @*/
    1842: PetscErrorCode  SNESSetFunction(SNES snes,Vec r,PetscErrorCode (*f)(SNES,Vec,Vec,void*),void *ctx)
    1843: {
    1845:   DM             dm;

    1849:   if (r) {
    1852:     PetscObjectReference((PetscObject)r);
    1853:     VecDestroy(&snes->vec_func);

    1855:     snes->vec_func = r;
    1856:   }
    1857:   SNESGetDM(snes,&dm);
    1858:   DMSNESSetFunction(dm,f,ctx);
    1859:   return(0);
    1860: }

    1863: /*@C
    1864:    SNESSetInitialFunction - Sets the function vector to be used as the
    1865:    function norm at the initialization of the method.  In some
    1866:    instances, the user has precomputed the function before calling
    1867:    SNESSolve.  This function allows one to avoid a redundant call
    1868:    to SNESComputeFunction in that case.

    1870:    Logically Collective on SNES

    1872:    Input Parameters:
    1873: +  snes - the SNES context
    1874: -  f - vector to store function value

    1876:    Notes:
    1877:    This should not be modified during the solution procedure.

    1879:    This is used extensively in the SNESFAS hierarchy and in nonlinear preconditioning.

    1881:    Level: developer

    1883: .seealso: SNESSetFunction(), SNESComputeFunction(), SNESSetInitialFunctionNorm()
    1884: @*/
    1885: PetscErrorCode  SNESSetInitialFunction(SNES snes, Vec f)
    1886: {
    1888:   Vec            vec_func;

    1894:   if (snes->npcside== PC_LEFT && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
    1895:     snes->vec_func_init_set = PETSC_FALSE;
    1896:     return(0);
    1897:   }
    1898:   SNESGetFunction(snes,&vec_func,NULL,NULL);
    1899:   VecCopy(f, vec_func);

    1901:   snes->vec_func_init_set = PETSC_TRUE;
    1902:   return(0);
    1903: }

    1905: /*@
    1906:    SNESSetNormSchedule - Sets the SNESNormSchedule used in covergence and monitoring
    1907:    of the SNES method.

    1909:    Logically Collective on SNES

    1911:    Input Parameters:
    1912: +  snes - the SNES context
    1913: -  normschedule - the frequency of norm computation

    1915:    Options Database Key:
    1916: .  -snes_norm_schedule <none, always, initialonly, finalonly, initalfinalonly>

    1918:    Notes:
    1919:    Only certain SNES methods support certain SNESNormSchedules.  Most require evaluation
    1920:    of the nonlinear function and the taking of its norm at every iteration to
    1921:    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
    1922:    (SNESNGS) and the like do not require the norm of the function to be computed, and therfore
    1923:    may either be monitored for convergence or not.  As these are often used as nonlinear
    1924:    preconditioners, monitoring the norm of their error is not a useful enterprise within
    1925:    their solution.

    1927:    Level: developer

    1929: .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    1930: @*/
    1931: PetscErrorCode  SNESSetNormSchedule(SNES snes, SNESNormSchedule normschedule)
    1932: {
    1935:   snes->normschedule = normschedule;
    1936:   return(0);
    1937: }

    1940: /*@
    1941:    SNESGetNormSchedule - Gets the SNESNormSchedule used in covergence and monitoring
    1942:    of the SNES method.

    1944:    Logically Collective on SNES

    1946:    Input Parameters:
    1947: +  snes - the SNES context
    1948: -  normschedule - the type of the norm used

    1950:    Level: advanced

    1952: .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    1953: @*/
    1954: PetscErrorCode  SNESGetNormSchedule(SNES snes, SNESNormSchedule *normschedule)
    1955: {
    1958:   *normschedule = snes->normschedule;
    1959:   return(0);
    1960: }

    1963: /*@
    1964:   SNESSetFunctionNorm - Sets the last computed residual norm.

    1966:   Logically Collective on SNES

    1968:   Input Parameters:
    1969: + snes - the SNES context

    1971: - normschedule - the frequency of norm computation

    1973:   Level: developer

    1975: .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    1976: @*/
    1977: PetscErrorCode SNESSetFunctionNorm(SNES snes, PetscReal norm)
    1978: {
    1981:   snes->norm = norm;
    1982:   return(0);
    1983: }

    1985: /*@
    1986:   SNESGetFunctionNorm - Gets the last computed norm of the residual

    1988:   Not Collective

    1990:   Input Parameter:
    1991: . snes - the SNES context

    1993:   Output Parameter:
    1994: . norm - the last computed residual norm

    1996:   Level: developer

    1998: .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    1999: @*/
    2000: PetscErrorCode SNESGetFunctionNorm(SNES snes, PetscReal *norm)
    2001: {
    2005:   *norm = snes->norm;
    2006:   return(0);
    2007: }

    2009: /*@
    2010:   SNESGetUpdateNorm - Gets the last computed norm of the Newton update

    2012:   Not Collective

    2014:   Input Parameter:
    2015: . snes - the SNES context

    2017:   Output Parameter:
    2018: . ynorm - the last computed update norm

    2020:   Level: developer

    2022: .seealso: SNESSetNormSchedule(), SNESComputeFunction(), SNESGetFunctionNorm()
    2023: @*/
    2024: PetscErrorCode SNESGetUpdateNorm(SNES snes, PetscReal *ynorm)
    2025: {
    2029:   *ynorm = snes->ynorm;
    2030:   return(0);
    2031: }

    2033: /*@
    2034:   SNESGetSolutionNorm - Gets the last computed norm of the solution

    2036:   Not Collective

    2038:   Input Parameter:
    2039: . snes - the SNES context

    2041:   Output Parameter:
    2042: . xnorm - the last computed solution norm

    2044:   Level: developer

    2046: .seealso: SNESSetNormSchedule(), SNESComputeFunction(), SNESGetFunctionNorm(), SNESGetUpdateNorm()
    2047: @*/
    2048: PetscErrorCode SNESGetSolutionNorm(SNES snes, PetscReal *xnorm)
    2049: {
    2053:   *xnorm = snes->xnorm;
    2054:   return(0);
    2055: }

    2057: /*@C
    2058:    SNESSetFunctionType - Sets the SNESNormSchedule used in covergence and monitoring
    2059:    of the SNES method.

    2061:    Logically Collective on SNES

    2063:    Input Parameters:
    2064: +  snes - the SNES context
    2065: -  normschedule - the frequency of norm computation

    2067:    Notes:
    2068:    Only certain SNES methods support certain SNESNormSchedules.  Most require evaluation
    2069:    of the nonlinear function and the taking of its norm at every iteration to
    2070:    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
    2071:    (SNESNGS) and the like do not require the norm of the function to be computed, and therfore
    2072:    may either be monitored for convergence or not.  As these are often used as nonlinear
    2073:    preconditioners, monitoring the norm of their error is not a useful enterprise within
    2074:    their solution.

    2076:    Level: developer

    2078: .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    2079: @*/
    2080: PetscErrorCode  SNESSetFunctionType(SNES snes, SNESFunctionType type)
    2081: {
    2084:   snes->functype = type;
    2085:   return(0);
    2086: }

    2089: /*@C
    2090:    SNESGetFunctionType - Gets the SNESNormSchedule used in covergence and monitoring
    2091:    of the SNES method.

    2093:    Logically Collective on SNES

    2095:    Input Parameters:
    2096: +  snes - the SNES context
    2097: -  normschedule - the type of the norm used

    2099:    Level: advanced

    2101: .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
    2102: @*/
    2103: PetscErrorCode  SNESGetFunctionType(SNES snes, SNESFunctionType *type)
    2104: {
    2107:   *type = snes->functype;
    2108:   return(0);
    2109: }

    2111: /*MC
    2112:     SNESNGSFunction - function used to convey a Gauss-Seidel sweep on the nonlinear function

    2114:      Synopsis:
    2115: #include <petscsnes.h>
    2116: $    SNESNGSFunction(SNES snes,Vec x,Vec b,void *ctx);

    2118:      Collective on snes

    2120:      Input Parameters:
    2121: +  X   - solution vector
    2122: .  B   - RHS vector
    2123: -  ctx - optional user-defined Gauss-Seidel context

    2125:      Output Parameter:
    2126: .  X   - solution vector

    2128:    Level: intermediate

    2130: .seealso:   SNESSetNGS(), SNESGetNGS()
    2131: M*/

    2133: /*@C
    2134:    SNESSetNGS - Sets the user nonlinear Gauss-Seidel routine for
    2135:    use with composed nonlinear solvers.

    2137:    Input Parameters:
    2138: +  snes   - the SNES context
    2139: .  f - function evaluation routine to apply Gauss-Seidel see SNESNGSFunction
    2140: -  ctx    - [optional] user-defined context for private data for the
    2141:             smoother evaluation routine (may be NULL)

    2143:    Notes:
    2144:    The NGS routines are used by the composed nonlinear solver to generate
    2145:     a problem appropriate update to the solution, particularly FAS.

    2147:    Level: intermediate

    2149: .seealso: SNESGetFunction(), SNESComputeNGS()
    2150: @*/
    2151: PetscErrorCode SNESSetNGS(SNES snes,PetscErrorCode (*f)(SNES,Vec,Vec,void*),void *ctx)
    2152: {
    2154:   DM             dm;

    2158:   SNESGetDM(snes,&dm);
    2159:   DMSNESSetNGS(dm,f,ctx);
    2160:   return(0);
    2161: }

    2163: PetscErrorCode SNESPicardComputeFunction(SNES snes,Vec x,Vec f,void *ctx)
    2164: {
    2166:   DM             dm;
    2167:   DMSNES         sdm;

    2170:   SNESGetDM(snes,&dm);
    2171:   DMGetDMSNES(dm,&sdm);
    2172:   if (!sdm->ops->computepfunction) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetPicard() to provide Picard function.");
    2173:   if (!sdm->ops->computepjacobian) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetPicard() to provide Picard Jacobian.");
    2174:   /*  A(x)*x - b(x) */
    2175:   PetscStackPush("SNES Picard user function");
    2176:   (*sdm->ops->computepfunction)(snes,x,f,sdm->pctx);
    2177:   PetscStackPop;
    2178:   PetscStackPush("SNES Picard user Jacobian");
    2179:   (*sdm->ops->computepjacobian)(snes,x,snes->jacobian,snes->jacobian_pre,sdm->pctx);
    2180:   PetscStackPop;
    2181:   VecScale(f,-1.0);
    2182:   MatMultAdd(snes->jacobian,x,f,f);
    2183:   return(0);
    2184: }

    2186: PetscErrorCode SNESPicardComputeJacobian(SNES snes,Vec x1,Mat J,Mat B,void *ctx)
    2187: {
    2189:   /* the jacobian matrix should be pre-filled in SNESPicardComputeFunction */
    2190:   return(0);
    2191: }

    2193: /*@C
    2194:    SNESSetPicard - Use SNES to solve the semilinear-system A(x) x = b(x) via a Picard type iteration (Picard linearization)

    2196:    Logically Collective on SNES

    2198:    Input Parameters:
    2199: +  snes - the SNES context
    2200: .  r - vector to store function value
    2201: .  b - function evaluation routine
    2202: .  Amat - matrix with which A(x) x - b(x) is to be computed
    2203: .  Pmat - matrix from which preconditioner is computed (usually the same as Amat)
    2204: .  J  - function to compute matrix value, see SNESJacobianFunction for details on its calling sequence
    2205: -  ctx - [optional] user-defined context for private data for the
    2206:          function evaluation routine (may be NULL)

    2208:    Notes:
    2209:     We do not recomemend using this routine. It is far better to provide the nonlinear function F() and some approximation to the Jacobian and use
    2210:     an approximate Newton solver. This interface is provided to allow porting/testing a previous Picard based code in PETSc before converting it to approximate Newton.

    2212:     One can call SNESSetPicard() or SNESSetFunction() (and possibly SNESSetJacobian()) but cannot call both

    2214: $     Solves the equation A(x) x = b(x) via the defect correction algorithm A(x^{n}) (x^{n+1} - x^{n}) = b(x^{n}) - A(x^{n})x^{n}
    2215: $     Note that when an exact solver is used this corresponds to the "classic" Picard A(x^{n}) x^{n+1} = b(x^{n}) iteration.

    2217:      Run with -snes_mf_operator to solve the system with Newton's method using A(x^{n}) to construct the preconditioner.

    2219:    We implement the defect correction form of the Picard iteration because it converges much more generally when inexact linear solvers are used then
    2220:    the direct Picard iteration A(x^n) x^{n+1} = b(x^n)

    2222:    There is some controversity over the definition of a Picard iteration for nonlinear systems but almost everyone agrees that it involves a linear solve and some
    2223:    believe it is the iteration  A(x^{n}) x^{n+1} = b(x^{n}) hence we use the name Picard. If anyone has an authoritative  reference that defines the Picard iteration
    2224:    different please contact us at petsc-dev@mcs.anl.gov and we'll have an entirely new argument :-).

    2226:    Level: intermediate

    2228: .seealso: SNESGetFunction(), SNESSetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESGetPicard(), SNESLineSearchPreCheckPicard(), SNESJacobianFunction
    2229: @*/
    2230: PetscErrorCode  SNESSetPicard(SNES snes,Vec r,PetscErrorCode (*b)(SNES,Vec,Vec,void*),Mat Amat, Mat Pmat, PetscErrorCode (*J)(SNES,Vec,Mat,Mat,void*),void *ctx)
    2231: {
    2233:   DM             dm;

    2237:   SNESGetDM(snes, &dm);
    2238:   DMSNESSetPicard(dm,b,J,ctx);
    2239:   SNESSetFunction(snes,r,SNESPicardComputeFunction,ctx);
    2240:   SNESSetJacobian(snes,Amat,Pmat,SNESPicardComputeJacobian,ctx);
    2241:   return(0);
    2242: }

    2244: /*@C
    2245:    SNESGetPicard - Returns the context for the Picard iteration

    2247:    Not Collective, but Vec is parallel if SNES is parallel. Collective if Vec is requested, but has not been created yet.

    2249:    Input Parameter:
    2250: .  snes - the SNES context

    2252:    Output Parameter:
    2253: +  r - the function (or NULL)
    2254: .  f - the function (or NULL); see SNESFunction for calling sequence details
    2255: .  Amat - the matrix used to defined the operation A(x) x - b(x) (or NULL)
    2256: .  Pmat  - the matrix from which the preconditioner will be constructed (or NULL)
    2257: .  J - the function for matrix evaluation (or NULL); see SNESJacobianFunction for calling sequence details
    2258: -  ctx - the function context (or NULL)

    2260:    Level: advanced

    2262: .seealso: SNESSetPicard(), SNESGetFunction(), SNESGetJacobian(), SNESGetDM(), SNESFunction, SNESJacobianFunction
    2263: @*/
    2264: PetscErrorCode  SNESGetPicard(SNES snes,Vec *r,PetscErrorCode (**f)(SNES,Vec,Vec,void*),Mat *Amat, Mat *Pmat, PetscErrorCode (**J)(SNES,Vec,Mat,Mat,void*),void **ctx)
    2265: {
    2267:   DM             dm;

    2271:   SNESGetFunction(snes,r,NULL,NULL);
    2272:   SNESGetJacobian(snes,Amat,Pmat,NULL,NULL);
    2273:   SNESGetDM(snes,&dm);
    2274:   DMSNESGetPicard(dm,f,J,ctx);
    2275:   return(0);
    2276: }

    2278: /*@C
    2279:    SNESSetComputeInitialGuess - Sets a routine used to compute an initial guess for the problem

    2281:    Logically Collective on SNES

    2283:    Input Parameters:
    2284: +  snes - the SNES context
    2285: .  func - function evaluation routine
    2286: -  ctx - [optional] user-defined context for private data for the
    2287:          function evaluation routine (may be NULL)

    2289:    Calling sequence of func:
    2290: $    func (SNES snes,Vec x,void *ctx);

    2292: .  f - function vector
    2293: -  ctx - optional user-defined function context

    2295:    Level: intermediate

    2297: .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian()
    2298: @*/
    2299: PetscErrorCode  SNESSetComputeInitialGuess(SNES snes,PetscErrorCode (*func)(SNES,Vec,void*),void *ctx)
    2300: {
    2303:   if (func) snes->ops->computeinitialguess = func;
    2304:   if (ctx)  snes->initialguessP            = ctx;
    2305:   return(0);
    2306: }

    2308: /* --------------------------------------------------------------- */
    2309: /*@C
    2310:    SNESGetRhs - Gets the vector for solving F(x) = rhs. If rhs is not set
    2311:    it assumes a zero right hand side.

    2313:    Logically Collective on SNES

    2315:    Input Parameter:
    2316: .  snes - the SNES context

    2318:    Output Parameter:
    2319: .  rhs - the right hand side vector or NULL if the right hand side vector is null

    2321:    Level: intermediate

    2323: .seealso: SNESGetSolution(), SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction()
    2324: @*/
    2325: PetscErrorCode  SNESGetRhs(SNES snes,Vec *rhs)
    2326: {
    2330:   *rhs = snes->vec_rhs;
    2331:   return(0);
    2332: }

    2334: /*@
    2335:    SNESComputeFunction - Calls the function that has been set with SNESSetFunction().

    2337:    Collective on SNES

    2339:    Input Parameters:
    2340: +  snes - the SNES context
    2341: -  x - input vector

    2343:    Output Parameter:
    2344: .  y - function vector, as set by SNESSetFunction()

    2346:    Notes:
    2347:    SNESComputeFunction() is typically used within nonlinear solvers
    2348:    implementations, so most users would not generally call this routine
    2349:    themselves.

    2351:    Level: developer

    2353: .seealso: SNESSetFunction(), SNESGetFunction()
    2354: @*/
    2355: PetscErrorCode  SNESComputeFunction(SNES snes,Vec x,Vec y)
    2356: {
    2358:   DM             dm;
    2359:   DMSNES         sdm;

    2367:   VecValidValues(x,2,PETSC_TRUE);

    2369:   SNESGetDM(snes,&dm);
    2370:   DMGetDMSNES(dm,&sdm);
    2371:   if (sdm->ops->computefunction) {
    2372:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) {
    2373:       PetscLogEventBegin(SNES_FunctionEval,snes,x,y,0);
    2374:     }
    2375:     VecLockReadPush(x);
    2376:     PetscStackPush("SNES user function");
    2377:     /* ensure domainerror is false prior to computefunction evaluation (may not have been reset) */
    2378:     snes->domainerror = PETSC_FALSE;
    2379:     (*sdm->ops->computefunction)(snes,x,y,sdm->functionctx);
    2380:     PetscStackPop;
    2381:     VecLockReadPop(x);
    2382:     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) {
    2383:       PetscLogEventEnd(SNES_FunctionEval,snes,x,y,0);
    2384:     }
    2385:   } else if (snes->vec_rhs) {
    2386:     MatMult(snes->jacobian, x, y);
    2387:   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetFunction() or SNESSetDM() before SNESComputeFunction(), likely called from SNESSolve().");
    2388:   if (snes->vec_rhs) {
    2389:     VecAXPY(y,-1.0,snes->vec_rhs);
    2390:   }
    2391:   snes->nfuncs++;
    2392:   /*
    2393:      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
    2394:      propagate the value to all processes
    2395:   */
    2396:   if (snes->domainerror) {
    2397:     VecSetInf(y);
    2398:   }
    2399:   return(0);
    2400: }

    2402: /*@
    2403:    SNESComputeNGS - Calls the Gauss-Seidel function that has been set with  SNESSetNGS().

    2405:    Collective on SNES

    2407:    Input Parameters:
    2408: +  snes - the SNES context
    2409: .  x - input vector
    2410: -  b - rhs vector

    2412:    Output Parameter:
    2413: .  x - new solution vector

    2415:    Notes:
    2416:    SNESComputeNGS() is typically used within composed nonlinear solver
    2417:    implementations, so most users would not generally call this routine
    2418:    themselves.

    2420:    Level: developer

    2422: .seealso: SNESSetNGS(), SNESComputeFunction()
    2423: @*/
    2424: PetscErrorCode  SNESComputeNGS(SNES snes,Vec b,Vec x)
    2425: {
    2427:   DM             dm;
    2428:   DMSNES         sdm;

    2436:   if (b) {VecValidValues(b,2,PETSC_TRUE);}
    2437:   PetscLogEventBegin(SNES_NGSEval,snes,x,b,0);
    2438:   SNESGetDM(snes,&dm);
    2439:   DMGetDMSNES(dm,&sdm);
    2440:   if (sdm->ops->computegs) {
    2441:     if (b) {VecLockReadPush(b);}
    2442:     PetscStackPush("SNES user NGS");
    2443:     (*sdm->ops->computegs)(snes,x,b,sdm->gsctx);
    2444:     PetscStackPop;
    2445:     if (b) {VecLockReadPop(b);}
    2446:   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetNGS() before SNESComputeNGS(), likely called from SNESSolve().");
    2447:   PetscLogEventEnd(SNES_NGSEval,snes,x,b,0);
    2448:   return(0);
    2449: }

    2451: PetscErrorCode SNESTestJacobian(SNES snes)
    2452: {
    2453:   Mat               A,B,C,D,jacobian;
    2454:   Vec               x = snes->vec_sol,f = snes->vec_func;
    2455:   PetscErrorCode    ierr;
    2456:   PetscReal         nrm,gnorm;
    2457:   PetscReal         threshold = 1.e-5;
    2458:   MatType           mattype;
    2459:   PetscInt          m,n,M,N;
    2460:   void              *functx;
    2461:   PetscBool         complete_print = PETSC_FALSE,threshold_print = PETSC_FALSE,test = PETSC_FALSE,flg,istranspose;
    2462:   PetscViewer       viewer,mviewer;
    2463:   MPI_Comm          comm;
    2464:   PetscInt          tabs;
    2465:   static PetscBool  directionsprinted = PETSC_FALSE;
    2466:   PetscViewerFormat format;

    2469:   PetscObjectOptionsBegin((PetscObject)snes);
    2470:   PetscOptionsName("-snes_test_jacobian","Compare hand-coded and finite difference Jacobians","None",&test);
    2471:   PetscOptionsReal("-snes_test_jacobian", "Threshold for element difference between hand-coded and finite difference being meaningful", "None", threshold, &threshold,NULL);
    2472:   PetscOptionsViewer("-snes_test_jacobian_view","View difference between hand-coded and finite difference Jacobians element entries","None",&mviewer,&format,&complete_print);
    2473:   if (!complete_print) {
    2474:     PetscOptionsDeprecated("-snes_test_jacobian_display","-snes_test_jacobian_view","3.13",NULL);
    2475:     PetscOptionsViewer("-snes_test_jacobian_display","Display difference between hand-coded and finite difference Jacobians","None",&mviewer,&format,&complete_print);
    2476:   }
    2477:   /* for compatibility with PETSc 3.9 and older. */
    2478:   PetscOptionsDeprecated("-snes_test_jacobian_display_threshold","-snes_test_jacobian","3.13","-snes_test_jacobian accepts an optional threshold (since v3.10)");
    2479:   PetscOptionsReal("-snes_test_jacobian_display_threshold", "Display difference between hand-coded and finite difference Jacobians which exceed input threshold", "None", threshold, &threshold, &threshold_print);
    2480:   PetscOptionsEnd();
    2481:   if (!test) return(0);

    2483:   PetscObjectGetComm((PetscObject)snes,&comm);
    2484:   PetscViewerASCIIGetStdout(comm,&viewer);
    2485:   PetscViewerASCIIGetTab(viewer, &tabs);
    2486:   PetscViewerASCIISetTab(viewer, ((PetscObject)snes)->tablevel);
    2487:   PetscViewerASCIIPrintf(viewer,"  ---------- Testing Jacobian -------------\n");
    2488:   if (!complete_print && !directionsprinted) {
    2489:     PetscViewerASCIIPrintf(viewer,"  Run with -snes_test_jacobian_view and optionally -snes_test_jacobian <threshold> to show difference\n");
    2490:     PetscViewerASCIIPrintf(viewer,"    of hand-coded and finite difference Jacobian entries greater than <threshold>.\n");
    2491:   }
    2492:   if (!directionsprinted) {
    2493:     PetscViewerASCIIPrintf(viewer,"  Testing hand-coded Jacobian, if (for double precision runs) ||J - Jfd||_F/||J||_F is\n");
    2494:     PetscViewerASCIIPrintf(viewer,"    O(1.e-8), the hand-coded Jacobian is probably correct.\n");
    2495:     directionsprinted = PETSC_TRUE;
    2496:   }
    2497:   if (complete_print) {
    2498:     PetscViewerPushFormat(mviewer,format);
    2499:   }

    2501:   PetscObjectTypeCompare((PetscObject)snes->jacobian,MATMFFD,&flg);
    2502:   if (!flg) jacobian = snes->jacobian;
    2503:   else jacobian = snes->jacobian_pre;

    2505:   if (!x) {
    2506:     MatCreateVecs(jacobian, &x, NULL);
    2507:   } else {
    2508:     PetscObjectReference((PetscObject) x);
    2509:   }
    2510:   if (!f) {
    2511:     VecDuplicate(x, &f);
    2512:   } else {
    2513:     PetscObjectReference((PetscObject) f);
    2514:   }
    2515:   /* evaluate the function at this point because SNESComputeJacobianDefault() assumes that the function has been evaluated and put into snes->vec_func */
    2516:   SNESComputeFunction(snes,x,f);
    2517:   VecDestroy(&f);
    2518:   PetscObjectTypeCompare((PetscObject)snes,SNESKSPTRANSPOSEONLY,&istranspose);
    2519:   while (jacobian) {
    2520:     Mat JT = NULL, Jsave = NULL;

    2522:     if (istranspose) {
    2523:       MatCreateTranspose(jacobian,&JT);
    2524:       Jsave = jacobian;
    2525:       jacobian = JT;
    2526:     }
    2527:     PetscObjectBaseTypeCompareAny((PetscObject)jacobian,&flg,MATSEQAIJ,MATMPIAIJ,MATSEQDENSE,MATMPIDENSE,MATSEQBAIJ,MATMPIBAIJ,MATSEQSBAIJ,MATMPISBAIJ,"");
    2528:     if (flg) {
    2529:       A    = jacobian;
    2530:       PetscObjectReference((PetscObject)A);
    2531:     } else {
    2532:       MatComputeOperator(jacobian,MATAIJ,&A);
    2533:     }

    2535:     MatGetType(A,&mattype);
    2536:     MatGetSize(A,&M,&N);
    2537:     MatGetLocalSize(A,&m,&n);
    2538:     MatCreate(PetscObjectComm((PetscObject)A),&B);
    2539:     MatSetType(B,mattype);
    2540:     MatSetSizes(B,m,n,M,N);
    2541:     MatSetBlockSizesFromMats(B,A,A);
    2542:     MatSetUp(B);
    2543:     MatSetOption(B,MAT_NEW_NONZERO_ALLOCATION_ERR,PETSC_FALSE);

    2545:     SNESGetFunction(snes,NULL,NULL,&functx);
    2546:     SNESComputeJacobianDefault(snes,x,B,B,functx);

    2548:     MatDuplicate(B,MAT_COPY_VALUES,&D);
    2549:     MatAYPX(D,-1.0,A,DIFFERENT_NONZERO_PATTERN);
    2550:     MatNorm(D,NORM_FROBENIUS,&nrm);
    2551:     MatNorm(A,NORM_FROBENIUS,&gnorm);
    2552:     MatDestroy(&D);
    2553:     if (!gnorm) gnorm = 1; /* just in case */
    2554:     PetscViewerASCIIPrintf(viewer,"  ||J - Jfd||_F/||J||_F = %g, ||J - Jfd||_F = %g\n",(double)(nrm/gnorm),(double)nrm);

    2556:     if (complete_print) {
    2557:       PetscViewerASCIIPrintf(viewer,"  Hand-coded Jacobian ----------\n");
    2558:       MatView(A,mviewer);
    2559:       PetscViewerASCIIPrintf(viewer,"  Finite difference Jacobian ----------\n");
    2560:       MatView(B,mviewer);
    2561:     }

    2563:     if (threshold_print || complete_print) {
    2564:       PetscInt          Istart, Iend, *ccols, bncols, cncols, j, row;
    2565:       PetscScalar       *cvals;
    2566:       const PetscInt    *bcols;
    2567:       const PetscScalar *bvals;

    2569:       MatCreate(PetscObjectComm((PetscObject)A),&C);
    2570:       MatSetType(C,mattype);
    2571:       MatSetSizes(C,m,n,M,N);
    2572:       MatSetBlockSizesFromMats(C,A,A);
    2573:       MatSetUp(C);
    2574:       MatSetOption(C,MAT_NEW_NONZERO_ALLOCATION_ERR,PETSC_FALSE);

    2576:       MatAYPX(B,-1.0,A,DIFFERENT_NONZERO_PATTERN);
    2577:       MatGetOwnershipRange(B,&Istart,&Iend);

    2579:       for (row = Istart; row < Iend; row++) {
    2580:         MatGetRow(B,row,&bncols,&bcols,&bvals);
    2581:         PetscMalloc2(bncols,&ccols,bncols,&cvals);
    2582:         for (j = 0, cncols = 0; j < bncols; j++) {
    2583:           if (PetscAbsScalar(bvals[j]) > threshold) {
    2584:             ccols[cncols] = bcols[j];
    2585:             cvals[cncols] = bvals[j];
    2586:             cncols += 1;
    2587:           }
    2588:         }
    2589:         if (cncols) {
    2590:           MatSetValues(C,1,&row,cncols,ccols,cvals,INSERT_VALUES);
    2591:         }
    2592:         MatRestoreRow(B,row,&bncols,&bcols,&bvals);
    2593:         PetscFree2(ccols,cvals);
    2594:       }
    2595:       MatAssemblyBegin(C,MAT_FINAL_ASSEMBLY);
    2596:       MatAssemblyEnd(C,MAT_FINAL_ASSEMBLY);
    2597:       PetscViewerASCIIPrintf(viewer,"  Hand-coded minus finite-difference Jacobian with tolerance %g ----------\n",(double)threshold);
    2598:       MatView(C,complete_print ? mviewer : viewer);
    2599:       MatDestroy(&C);
    2600:     }
    2601:     MatDestroy(&A);
    2602:     MatDestroy(&B);
    2603:     MatDestroy(&JT);
    2604:     if (Jsave) jacobian = Jsave;
    2605:     if (jacobian != snes->jacobian_pre) {
    2606:       jacobian = snes->jacobian_pre;
    2607:       PetscViewerASCIIPrintf(viewer,"  ---------- Testing Jacobian for preconditioner -------------\n");
    2608:     }
    2609:     else jacobian = NULL;
    2610:   }
    2611:   VecDestroy(&x);
    2612:   if (complete_print) {
    2613:     PetscViewerPopFormat(mviewer);
    2614:   }
    2615:   if (mviewer) { PetscViewerDestroy(&mviewer); }
    2616:   PetscViewerASCIISetTab(viewer,tabs);
    2617:   return(0);
    2618: }

    2620: /*@
    2621:    SNESComputeJacobian - Computes the Jacobian matrix that has been set with SNESSetJacobian().

    2623:    Collective on SNES

    2625:    Input Parameters:
    2626: +  snes - the SNES context
    2627: -  x - input vector

    2629:    Output Parameters:
    2630: +  A - Jacobian matrix
    2631: -  B - optional preconditioning matrix

    2633:   Options Database Keys:
    2634: +    -snes_lag_preconditioner <lag>
    2635: .    -snes_lag_jacobian <lag>
    2636: .    -snes_test_jacobian <optional threshold> - compare the user provided Jacobian with one compute via finite differences to check for errors.  If a threshold is given, display only those entries whose difference is greater than the threshold.
    2637: .    -snes_test_jacobian_view - display the user provided Jacobian, the finite difference Jacobian and the difference between them to help users detect the location of errors in the user provided Jacobian
    2638: .    -snes_compare_explicit - Compare the computed Jacobian to the finite difference Jacobian and output the differences
    2639: .    -snes_compare_explicit_draw  - Compare the computed Jacobian to the finite difference Jacobian and draw the result
    2640: .    -snes_compare_explicit_contour  - Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
    2641: .    -snes_compare_operator  - Make the comparison options above use the operator instead of the preconditioning matrix
    2642: .    -snes_compare_coloring - Compute the finite difference Jacobian using coloring and display norms of difference
    2643: .    -snes_compare_coloring_display - Compute the finite differece Jacobian using coloring and display verbose differences
    2644: .    -snes_compare_coloring_threshold - Display only those matrix entries that differ by more than a given threshold
    2645: .    -snes_compare_coloring_threshold_atol - Absolute tolerance for difference in matrix entries to be displayed by -snes_compare_coloring_threshold
    2646: .    -snes_compare_coloring_threshold_rtol - Relative tolerance for difference in matrix entries to be displayed by -snes_compare_coloring_threshold
    2647: .    -snes_compare_coloring_draw - Compute the finite differece Jacobian using coloring and draw differences
    2648: -    -snes_compare_coloring_draw_contour - Compute the finite differece Jacobian using coloring and show contours of matrices and differences

    2651:    Notes:
    2652:    Most users should not need to explicitly call this routine, as it
    2653:    is used internally within the nonlinear solvers.

    2655:    Developer Notes:
    2656:     This has duplicative ways of checking the accuracy of the user provided Jacobian (see the options above). This is for historical reasons, the routine SNESTestJacobian() use to used
    2657:       for with the SNESType of test that has been removed.

    2659:    Level: developer

    2661: .seealso:  SNESSetJacobian(), KSPSetOperators(), MatStructure, SNESSetLagPreconditioner(), SNESSetLagJacobian()
    2662: @*/
    2663: PetscErrorCode  SNESComputeJacobian(SNES snes,Vec X,Mat A,Mat B)
    2664: {
    2666:   PetscBool      flag;
    2667:   DM             dm;
    2668:   DMSNES         sdm;
    2669:   KSP            ksp;

    2675:   VecValidValues(X,2,PETSC_TRUE);
    2676:   SNESGetDM(snes,&dm);
    2677:   DMGetDMSNES(dm,&sdm);

    2679:   if (!sdm->ops->computejacobian) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_USER,"Must call SNESSetJacobian(), DMSNESSetJacobian(), DMDASNESSetJacobianLocal(), etc");

    2681:   /* make sure that MatAssemblyBegin/End() is called on A matrix if it is matrix free */

    2683:   if (snes->lagjacobian == -2) {
    2684:     snes->lagjacobian = -1;

    2686:     PetscInfo(snes,"Recomputing Jacobian/preconditioner because lag is -2 (means compute Jacobian, but then never again) \n");
    2687:   } else if (snes->lagjacobian == -1) {
    2688:     PetscInfo(snes,"Reusing Jacobian/preconditioner because lag is -1\n");
    2689:     PetscObjectTypeCompare((PetscObject)A,MATMFFD,&flag);
    2690:     if (flag) {
    2691:       MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
    2692:       MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
    2693:     }
    2694:     return(0);
    2695:   } else if (snes->lagjacobian > 1 && (snes->iter + snes->jac_iter) % snes->lagjacobian) {
    2696:     PetscInfo2(snes,"Reusing Jacobian/preconditioner because lag is %D and SNES iteration is %D\n",snes->lagjacobian,snes->iter);
    2697:     PetscObjectTypeCompare((PetscObject)A,MATMFFD,&flag);
    2698:     if (flag) {
    2699:       MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
    2700:       MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
    2701:     }
    2702:     return(0);
    2703:   }
    2704:   if (snes->npc && snes->npcside== PC_LEFT) {
    2705:     MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
    2706:     MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
    2707:     return(0);
    2708:   }

    2710:   PetscLogEventBegin(SNES_JacobianEval,snes,X,A,B);
    2711:   VecLockReadPush(X);
    2712:   PetscStackPush("SNES user Jacobian function");
    2713:   (*sdm->ops->computejacobian)(snes,X,A,B,sdm->jacobianctx);
    2714:   PetscStackPop;
    2715:   VecLockReadPop(X);
    2716:   PetscLogEventEnd(SNES_JacobianEval,snes,X,A,B);

    2718:   /* attach latest linearization point to the preconditioning matrix */
    2719:   PetscObjectCompose((PetscObject)B,"__SNES_latest_X",(PetscObject)X);

    2721:   /* the next line ensures that snes->ksp exists */
    2722:   SNESGetKSP(snes,&ksp);
    2723:   if (snes->lagpreconditioner == -2) {
    2724:     PetscInfo(snes,"Rebuilding preconditioner exactly once since lag is -2\n");
    2725:     KSPSetReusePreconditioner(snes->ksp,PETSC_FALSE);
    2726:     snes->lagpreconditioner = -1;
    2727:   } else if (snes->lagpreconditioner == -1) {
    2728:     PetscInfo(snes,"Reusing preconditioner because lag is -1\n");
    2729:     KSPSetReusePreconditioner(snes->ksp,PETSC_TRUE);
    2730:   } else if (snes->lagpreconditioner > 1 && (snes->iter + snes->pre_iter) % snes->lagpreconditioner) {
    2731:     PetscInfo2(snes,"Reusing preconditioner because lag is %D and SNES iteration is %D\n",snes->lagpreconditioner,snes->iter);
    2732:     KSPSetReusePreconditioner(snes->ksp,PETSC_TRUE);
    2733:   } else {
    2734:     PetscInfo(snes,"Rebuilding preconditioner\n");
    2735:     KSPSetReusePreconditioner(snes->ksp,PETSC_FALSE);
    2736:   }

    2738:   SNESTestJacobian(snes);
    2739:   /* make sure user returned a correct Jacobian and preconditioner */
    2742:   {
    2743:     PetscBool flag = PETSC_FALSE,flag_draw = PETSC_FALSE,flag_contour = PETSC_FALSE,flag_operator = PETSC_FALSE;
    2744:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject) snes)->options,((PetscObject)snes)->prefix,"-snes_compare_explicit",NULL,NULL,&flag);
    2745:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject) snes)->options,((PetscObject)snes)->prefix,"-snes_compare_explicit_draw",NULL,NULL,&flag_draw);
    2746:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject) snes)->options,((PetscObject)snes)->prefix,"-snes_compare_explicit_draw_contour",NULL,NULL,&flag_contour);
    2747:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject) snes)->options,((PetscObject)snes)->prefix,"-snes_compare_operator",NULL,NULL,&flag_operator);
    2748:     if (flag || flag_draw || flag_contour) {
    2749:       Mat          Bexp_mine = NULL,Bexp,FDexp;
    2750:       PetscViewer  vdraw,vstdout;
    2751:       PetscBool    flg;
    2752:       if (flag_operator) {
    2753:         MatComputeOperator(A,MATAIJ,&Bexp_mine);
    2754:         Bexp = Bexp_mine;
    2755:       } else {
    2756:         /* See if the preconditioning matrix can be viewed and added directly */
    2757:         PetscObjectBaseTypeCompareAny((PetscObject)B,&flg,MATSEQAIJ,MATMPIAIJ,MATSEQDENSE,MATMPIDENSE,MATSEQBAIJ,MATMPIBAIJ,MATSEQSBAIJ,MATMPIBAIJ,"");
    2758:         if (flg) Bexp = B;
    2759:         else {
    2760:           /* If the "preconditioning" matrix is itself MATSHELL or some other type without direct support */
    2761:           MatComputeOperator(B,MATAIJ,&Bexp_mine);
    2762:           Bexp = Bexp_mine;
    2763:         }
    2764:       }
    2765:       MatConvert(Bexp,MATSAME,MAT_INITIAL_MATRIX,&FDexp);
    2766:       SNESComputeJacobianDefault(snes,X,FDexp,FDexp,NULL);
    2767:       PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&vstdout);
    2768:       if (flag_draw || flag_contour) {
    2769:         PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),NULL,"Explicit Jacobians",PETSC_DECIDE,PETSC_DECIDE,300,300,&vdraw);
    2770:         if (flag_contour) {PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);}
    2771:       } else vdraw = NULL;
    2772:       PetscViewerASCIIPrintf(vstdout,"Explicit %s\n",flag_operator ? "Jacobian" : "preconditioning Jacobian");
    2773:       if (flag) {MatView(Bexp,vstdout);}
    2774:       if (vdraw) {MatView(Bexp,vdraw);}
    2775:       PetscViewerASCIIPrintf(vstdout,"Finite difference Jacobian\n");
    2776:       if (flag) {MatView(FDexp,vstdout);}
    2777:       if (vdraw) {MatView(FDexp,vdraw);}
    2778:       MatAYPX(FDexp,-1.0,Bexp,SAME_NONZERO_PATTERN);
    2779:       PetscViewerASCIIPrintf(vstdout,"User-provided matrix minus finite difference Jacobian\n");
    2780:       if (flag) {MatView(FDexp,vstdout);}
    2781:       if (vdraw) {              /* Always use contour for the difference */
    2782:         PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);
    2783:         MatView(FDexp,vdraw);
    2784:         PetscViewerPopFormat(vdraw);
    2785:       }
    2786:       if (flag_contour) {PetscViewerPopFormat(vdraw);}
    2787:       PetscViewerDestroy(&vdraw);
    2788:       MatDestroy(&Bexp_mine);
    2789:       MatDestroy(&FDexp);
    2790:     }
    2791:   }
    2792:   {
    2793:     PetscBool flag = PETSC_FALSE,flag_display = PETSC_FALSE,flag_draw = PETSC_FALSE,flag_contour = PETSC_FALSE,flag_threshold = PETSC_FALSE;
    2794:     PetscReal threshold_atol = PETSC_SQRT_MACHINE_EPSILON,threshold_rtol = 10*PETSC_SQRT_MACHINE_EPSILON;
    2795:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring",NULL,NULL,&flag);
    2796:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_display",NULL,NULL,&flag_display);
    2797:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_draw",NULL,NULL,&flag_draw);
    2798:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_draw_contour",NULL,NULL,&flag_contour);
    2799:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold",NULL,NULL,&flag_threshold);
    2800:     if (flag_threshold) {
    2801:       PetscOptionsGetReal(((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold_rtol",&threshold_rtol,NULL);
    2802:       PetscOptionsGetReal(((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold_atol",&threshold_atol,NULL);
    2803:     }
    2804:     if (flag || flag_display || flag_draw || flag_contour || flag_threshold) {
    2805:       Mat            Bfd;
    2806:       PetscViewer    vdraw,vstdout;
    2807:       MatColoring    coloring;
    2808:       ISColoring     iscoloring;
    2809:       MatFDColoring  matfdcoloring;
    2810:       PetscErrorCode (*func)(SNES,Vec,Vec,void*);
    2811:       void           *funcctx;
    2812:       PetscReal      norm1,norm2,normmax;

    2814:       MatDuplicate(B,MAT_DO_NOT_COPY_VALUES,&Bfd);
    2815:       MatColoringCreate(Bfd,&coloring);
    2816:       MatColoringSetType(coloring,MATCOLORINGSL);
    2817:       MatColoringSetFromOptions(coloring);
    2818:       MatColoringApply(coloring,&iscoloring);
    2819:       MatColoringDestroy(&coloring);
    2820:       MatFDColoringCreate(Bfd,iscoloring,&matfdcoloring);
    2821:       MatFDColoringSetFromOptions(matfdcoloring);
    2822:       MatFDColoringSetUp(Bfd,iscoloring,matfdcoloring);
    2823:       ISColoringDestroy(&iscoloring);

    2825:       /* This method of getting the function is currently unreliable since it doesn't work for DM local functions. */
    2826:       SNESGetFunction(snes,NULL,&func,&funcctx);
    2827:       MatFDColoringSetFunction(matfdcoloring,(PetscErrorCode (*)(void))func,funcctx);
    2828:       PetscObjectSetOptionsPrefix((PetscObject)matfdcoloring,((PetscObject)snes)->prefix);
    2829:       PetscObjectAppendOptionsPrefix((PetscObject)matfdcoloring,"coloring_");
    2830:       MatFDColoringSetFromOptions(matfdcoloring);
    2831:       MatFDColoringApply(Bfd,matfdcoloring,X,snes);
    2832:       MatFDColoringDestroy(&matfdcoloring);

    2834:       PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&vstdout);
    2835:       if (flag_draw || flag_contour) {
    2836:         PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),NULL,"Colored Jacobians",PETSC_DECIDE,PETSC_DECIDE,300,300,&vdraw);
    2837:         if (flag_contour) {PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);}
    2838:       } else vdraw = NULL;
    2839:       PetscViewerASCIIPrintf(vstdout,"Explicit preconditioning Jacobian\n");
    2840:       if (flag_display) {MatView(B,vstdout);}
    2841:       if (vdraw) {MatView(B,vdraw);}
    2842:       PetscViewerASCIIPrintf(vstdout,"Colored Finite difference Jacobian\n");
    2843:       if (flag_display) {MatView(Bfd,vstdout);}
    2844:       if (vdraw) {MatView(Bfd,vdraw);}
    2845:       MatAYPX(Bfd,-1.0,B,SAME_NONZERO_PATTERN);
    2846:       MatNorm(Bfd,NORM_1,&norm1);
    2847:       MatNorm(Bfd,NORM_FROBENIUS,&norm2);
    2848:       MatNorm(Bfd,NORM_MAX,&normmax);
    2849:       PetscViewerASCIIPrintf(vstdout,"User-provided matrix minus finite difference Jacobian, norm1=%g normFrob=%g normmax=%g\n",(double)norm1,(double)norm2,(double)normmax);
    2850:       if (flag_display) {MatView(Bfd,vstdout);}
    2851:       if (vdraw) {              /* Always use contour for the difference */
    2852:         PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);
    2853:         MatView(Bfd,vdraw);
    2854:         PetscViewerPopFormat(vdraw);
    2855:       }
    2856:       if (flag_contour) {PetscViewerPopFormat(vdraw);}

    2858:       if (flag_threshold) {
    2859:         PetscInt bs,rstart,rend,i;
    2860:         MatGetBlockSize(B,&bs);
    2861:         MatGetOwnershipRange(B,&rstart,&rend);
    2862:         for (i=rstart; i<rend; i++) {
    2863:           const PetscScalar *ba,*ca;
    2864:           const PetscInt    *bj,*cj;
    2865:           PetscInt          bn,cn,j,maxentrycol = -1,maxdiffcol = -1,maxrdiffcol = -1;
    2866:           PetscReal         maxentry = 0,maxdiff = 0,maxrdiff = 0;
    2867:           MatGetRow(B,i,&bn,&bj,&ba);
    2868:           MatGetRow(Bfd,i,&cn,&cj,&ca);
    2869:           if (bn != cn) SETERRQ(((PetscObject)A)->comm,PETSC_ERR_PLIB,"Unexpected different nonzero pattern in -snes_compare_coloring_threshold");
    2870:           for (j=0; j<bn; j++) {
    2871:             PetscReal rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol*PetscAbsScalar(ba[j]));
    2872:             if (PetscAbsScalar(ba[j]) > PetscAbs(maxentry)) {
    2873:               maxentrycol = bj[j];
    2874:               maxentry    = PetscRealPart(ba[j]);
    2875:             }
    2876:             if (PetscAbsScalar(ca[j]) > PetscAbs(maxdiff)) {
    2877:               maxdiffcol = bj[j];
    2878:               maxdiff    = PetscRealPart(ca[j]);
    2879:             }
    2880:             if (rdiff > maxrdiff) {
    2881:               maxrdiffcol = bj[j];
    2882:               maxrdiff    = rdiff;
    2883:             }
    2884:           }
    2885:           if (maxrdiff > 1) {
    2886:             PetscViewerASCIIPrintf(vstdout,"row %D (maxentry=%g at %D, maxdiff=%g at %D, maxrdiff=%g at %D):",i,(double)maxentry,maxentrycol,(double)maxdiff,maxdiffcol,(double)maxrdiff,maxrdiffcol);
    2887:             for (j=0; j<bn; j++) {
    2888:               PetscReal rdiff;
    2889:               rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol*PetscAbsScalar(ba[j]));
    2890:               if (rdiff > 1) {
    2891:                 PetscViewerASCIIPrintf(vstdout," (%D,%g:%g)",bj[j],(double)PetscRealPart(ba[j]),(double)PetscRealPart(ca[j]));
    2892:               }
    2893:             }
    2894:             PetscViewerASCIIPrintf(vstdout,"\n",i,maxentry,maxdiff,maxrdiff);
    2895:           }
    2896:           MatRestoreRow(B,i,&bn,&bj,&ba);
    2897:           MatRestoreRow(Bfd,i,&cn,&cj,&ca);
    2898:         }
    2899:       }
    2900:       PetscViewerDestroy(&vdraw);
    2901:       MatDestroy(&Bfd);
    2902:     }
    2903:   }
    2904:   return(0);
    2905: }

    2907: /*MC
    2908:     SNESJacobianFunction - Function used to convey the nonlinear Jacobian of the function to be solved by SNES

    2910:      Synopsis:
    2911:      #include "petscsnes.h"
    2912:      PetscErrorCode SNESJacobianFunction(SNES snes,Vec x,Mat Amat,Mat Pmat,void *ctx);

    2914:      Collective on snes

    2916:     Input Parameters:
    2917: +  x - input vector, the Jacobian is to be computed at this value
    2918: -  ctx - [optional] user-defined Jacobian context

    2920:     Output Parameters:
    2921: +  Amat - the matrix that defines the (approximate) Jacobian
    2922: -  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.

    2924:    Level: intermediate

    2926: .seealso:   SNESSetFunction(), SNESGetFunction(), SNESSetJacobian(), SNESGetJacobian()
    2927: M*/

    2929: /*@C
    2930:    SNESSetJacobian - Sets the function to compute Jacobian as well as the
    2931:    location to store the matrix.

    2933:    Logically Collective on SNES

    2935:    Input Parameters:
    2936: +  snes - the SNES context
    2937: .  Amat - the matrix that defines the (approximate) Jacobian
    2938: .  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.
    2939: .  J - Jacobian evaluation routine (if NULL then SNES retains any previously set value), see SNESJacobianFunction for details
    2940: -  ctx - [optional] user-defined context for private data for the
    2941:          Jacobian evaluation routine (may be NULL) (if NULL then SNES retains any previously set value)

    2943:    Notes:
    2944:    If the Amat matrix and Pmat matrix are different you must call MatAssemblyBegin/End() on
    2945:    each matrix.

    2947:    If you know the operator Amat has a null space you can use MatSetNullSpace() and MatSetTransposeNullSpace() to supply the null
    2948:    space to Amat and the KSP solvers will automatically use that null space as needed during the solution process.

    2950:    If using SNESComputeJacobianDefaultColor() to assemble a Jacobian, the ctx argument
    2951:    must be a MatFDColoring.

    2953:    Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
    2954:    example is to use the "Picard linearization" which only differentiates through the highest order parts of each term.

    2956:    Level: beginner

    2958: .seealso: KSPSetOperators(), SNESSetFunction(), MatMFFDComputeJacobian(), SNESComputeJacobianDefaultColor(), MatStructure, J,
    2959:           SNESSetPicard(), SNESJacobianFunction
    2960: @*/
    2961: PetscErrorCode  SNESSetJacobian(SNES snes,Mat Amat,Mat Pmat,PetscErrorCode (*J)(SNES,Vec,Mat,Mat,void*),void *ctx)
    2962: {
    2964:   DM             dm;

    2972:   SNESGetDM(snes,&dm);
    2973:   DMSNESSetJacobian(dm,J,ctx);
    2974:   if (Amat) {
    2975:     PetscObjectReference((PetscObject)Amat);
    2976:     MatDestroy(&snes->jacobian);

    2978:     snes->jacobian = Amat;
    2979:   }
    2980:   if (Pmat) {
    2981:     PetscObjectReference((PetscObject)Pmat);
    2982:     MatDestroy(&snes->jacobian_pre);

    2984:     snes->jacobian_pre = Pmat;
    2985:   }
    2986:   return(0);
    2987: }

    2989: /*@C
    2990:    SNESGetJacobian - Returns the Jacobian matrix and optionally the user
    2991:    provided context for evaluating the Jacobian.

    2993:    Not Collective, but Mat object will be parallel if SNES object is

    2995:    Input Parameter:
    2996: .  snes - the nonlinear solver context

    2998:    Output Parameters:
    2999: +  Amat - location to stash (approximate) Jacobian matrix (or NULL)
    3000: .  Pmat - location to stash matrix used to compute the preconditioner (or NULL)
    3001: .  J - location to put Jacobian function (or NULL), see SNESJacobianFunction for details on its calling sequence
    3002: -  ctx - location to stash Jacobian ctx (or NULL)

    3004:    Level: advanced

    3006: .seealso: SNESSetJacobian(), SNESComputeJacobian(), SNESJacobianFunction, SNESGetFunction()
    3007: @*/
    3008: PetscErrorCode SNESGetJacobian(SNES snes,Mat *Amat,Mat *Pmat,PetscErrorCode (**J)(SNES,Vec,Mat,Mat,void*),void **ctx)
    3009: {
    3011:   DM             dm;
    3012:   DMSNES         sdm;

    3016:   if (Amat) *Amat = snes->jacobian;
    3017:   if (Pmat) *Pmat = snes->jacobian_pre;
    3018:   SNESGetDM(snes,&dm);
    3019:   DMGetDMSNES(dm,&sdm);
    3020:   if (J) *J = sdm->ops->computejacobian;
    3021:   if (ctx) *ctx = sdm->jacobianctx;
    3022:   return(0);
    3023: }

    3025: static PetscErrorCode SNESSetDefaultComputeJacobian(SNES snes)
    3026: {
    3028:   DM             dm;
    3029:   DMSNES         sdm;

    3032:   SNESGetDM(snes,&dm);
    3033:   DMGetDMSNES(dm,&sdm);
    3034:   if (!sdm->ops->computejacobian && snes->jacobian_pre) {
    3035:     DM        dm;
    3036:     PetscBool isdense,ismf;

    3038:     SNESGetDM(snes,&dm);
    3039:     PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre,&isdense,MATSEQDENSE,MATMPIDENSE,MATDENSE,NULL);
    3040:     PetscObjectTypeCompareAny((PetscObject)snes->jacobian_pre,&ismf,MATMFFD,MATSHELL,NULL);
    3041:     if (isdense) {
    3042:       DMSNESSetJacobian(dm,SNESComputeJacobianDefault,NULL);
    3043:     } else if (!ismf) {
    3044:       DMSNESSetJacobian(dm,SNESComputeJacobianDefaultColor,NULL);
    3045:     }
    3046:   }
    3047:   return(0);
    3048: }

    3050: /*@
    3051:    SNESSetUp - Sets up the internal data structures for the later use
    3052:    of a nonlinear solver.

    3054:    Collective on SNES

    3056:    Input Parameters:
    3057: .  snes - the SNES context

    3059:    Notes:
    3060:    For basic use of the SNES solvers the user need not explicitly call
    3061:    SNESSetUp(), since these actions will automatically occur during
    3062:    the call to SNESSolve().  However, if one wishes to control this
    3063:    phase separately, SNESSetUp() should be called after SNESCreate()
    3064:    and optional routines of the form SNESSetXXX(), but before SNESSolve().

    3066:    Level: advanced

    3068: .seealso: SNESCreate(), SNESSolve(), SNESDestroy()
    3069: @*/
    3070: PetscErrorCode  SNESSetUp(SNES snes)
    3071: {
    3073:   DM             dm;
    3074:   DMSNES         sdm;
    3075:   SNESLineSearch linesearch, pclinesearch;
    3076:   void           *lsprectx,*lspostctx;
    3077:   PetscErrorCode (*precheck)(SNESLineSearch,Vec,Vec,PetscBool*,void*);
    3078:   PetscErrorCode (*postcheck)(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);
    3079:   PetscErrorCode (*func)(SNES,Vec,Vec,void*);
    3080:   Vec            f,fpc;
    3081:   void           *funcctx;
    3082:   PetscErrorCode (*jac)(SNES,Vec,Mat,Mat,void*);
    3083:   void           *jacctx,*appctx;
    3084:   Mat            j,jpre;

    3088:   if (snes->setupcalled) return(0);
    3089:   PetscLogEventBegin(SNES_Setup,snes,0,0,0);

    3091:   if (!((PetscObject)snes)->type_name) {
    3092:     SNESSetType(snes,SNESNEWTONLS);
    3093:   }

    3095:   SNESGetFunction(snes,&snes->vec_func,NULL,NULL);

    3097:   SNESGetDM(snes,&dm);
    3098:   DMGetDMSNES(dm,&sdm);
    3099:   if (!sdm->ops->computefunction) SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_ARG_WRONGSTATE,"Function never provided to SNES object");
    3100:   SNESSetDefaultComputeJacobian(snes);

    3102:   if (!snes->vec_func) {
    3103:     DMCreateGlobalVector(dm,&snes->vec_func);
    3104:   }

    3106:   if (!snes->ksp) {
    3107:     SNESGetKSP(snes, &snes->ksp);
    3108:   }

    3110:   if (snes->linesearch) {
    3111:     SNESGetLineSearch(snes, &snes->linesearch);
    3112:     SNESLineSearchSetFunction(snes->linesearch,SNESComputeFunction);
    3113:   }

    3115:   if (snes->npc && (snes->npcside== PC_LEFT)) {
    3116:     snes->mf          = PETSC_TRUE;
    3117:     snes->mf_operator = PETSC_FALSE;
    3118:   }

    3120:   if (snes->npc) {
    3121:     /* copy the DM over */
    3122:     SNESGetDM(snes,&dm);
    3123:     SNESSetDM(snes->npc,dm);

    3125:     SNESGetFunction(snes,&f,&func,&funcctx);
    3126:     VecDuplicate(f,&fpc);
    3127:     SNESSetFunction(snes->npc,fpc,func,funcctx);
    3128:     SNESGetJacobian(snes,&j,&jpre,&jac,&jacctx);
    3129:     SNESSetJacobian(snes->npc,j,jpre,jac,jacctx);
    3130:     SNESGetApplicationContext(snes,&appctx);
    3131:     SNESSetApplicationContext(snes->npc,appctx);
    3132:     VecDestroy(&fpc);

    3134:     /* copy the function pointers over */
    3135:     PetscObjectCopyFortranFunctionPointers((PetscObject)snes,(PetscObject)snes->npc);

    3137:     /* default to 1 iteration */
    3138:     SNESSetTolerances(snes->npc,0.0,0.0,0.0,1,snes->npc->max_funcs);
    3139:     if (snes->npcside==PC_RIGHT) {
    3140:       SNESSetNormSchedule(snes->npc,SNES_NORM_FINAL_ONLY);
    3141:     } else {
    3142:       SNESSetNormSchedule(snes->npc,SNES_NORM_NONE);
    3143:     }
    3144:     SNESSetFromOptions(snes->npc);

    3146:     /* copy the line search context over */
    3147:     if (snes->linesearch && snes->npc->linesearch) {
    3148:       SNESGetLineSearch(snes,&linesearch);
    3149:       SNESGetLineSearch(snes->npc,&pclinesearch);
    3150:       SNESLineSearchGetPreCheck(linesearch,&precheck,&lsprectx);
    3151:       SNESLineSearchGetPostCheck(linesearch,&postcheck,&lspostctx);
    3152:       SNESLineSearchSetPreCheck(pclinesearch,precheck,lsprectx);
    3153:       SNESLineSearchSetPostCheck(pclinesearch,postcheck,lspostctx);
    3154:       PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)pclinesearch);
    3155:     }
    3156:   }
    3157:   if (snes->mf) {
    3158:     SNESSetUpMatrixFree_Private(snes, snes->mf_operator, snes->mf_version);
    3159:   }
    3160:   if (snes->ops->usercompute && !snes->user) {
    3161:     (*snes->ops->usercompute)(snes,(void**)&snes->user);
    3162:   }

    3164:   snes->jac_iter = 0;
    3165:   snes->pre_iter = 0;

    3167:   if (snes->ops->setup) {
    3168:     (*snes->ops->setup)(snes);
    3169:   }

    3171:   SNESSetDefaultComputeJacobian(snes);

    3173:   if (snes->npc && (snes->npcside== PC_LEFT)) {
    3174:     if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
    3175:       if (snes->linesearch){
    3176:         SNESGetLineSearch(snes,&linesearch);
    3177:         SNESLineSearchSetFunction(linesearch,SNESComputeFunctionDefaultNPC);
    3178:       }
    3179:     }
    3180:   }
    3181:   PetscLogEventEnd(SNES_Setup,snes,0,0,0);
    3182:   snes->setupcalled = PETSC_TRUE;
    3183:   return(0);
    3184: }

    3186: /*@
    3187:    SNESReset - Resets a SNES context to the snessetupcalled = 0 state and removes any allocated Vecs and Mats

    3189:    Collective on SNES

    3191:    Input Parameter:
    3192: .  snes - iterative context obtained from SNESCreate()

    3194:    Level: intermediate

    3196:    Notes:
    3197:     Also calls the application context destroy routine set with SNESSetComputeApplicationContext()

    3199: .seealso: SNESCreate(), SNESSetUp(), SNESSolve()
    3200: @*/
    3201: PetscErrorCode  SNESReset(SNES snes)
    3202: {

    3207:   if (snes->ops->userdestroy && snes->user) {
    3208:     (*snes->ops->userdestroy)((void**)&snes->user);
    3209:     snes->user = NULL;
    3210:   }
    3211:   if (snes->npc) {
    3212:     SNESReset(snes->npc);
    3213:   }

    3215:   if (snes->ops->reset) {
    3216:     (*snes->ops->reset)(snes);
    3217:   }
    3218:   if (snes->ksp) {
    3219:     KSPReset(snes->ksp);
    3220:   }

    3222:   if (snes->linesearch) {
    3223:     SNESLineSearchReset(snes->linesearch);
    3224:   }

    3226:   VecDestroy(&snes->vec_rhs);
    3227:   VecDestroy(&snes->vec_sol);
    3228:   VecDestroy(&snes->vec_sol_update);
    3229:   VecDestroy(&snes->vec_func);
    3230:   MatDestroy(&snes->jacobian);
    3231:   MatDestroy(&snes->jacobian_pre);
    3232:   VecDestroyVecs(snes->nwork,&snes->work);
    3233:   VecDestroyVecs(snes->nvwork,&snes->vwork);

    3235:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

    3237:   snes->nwork       = snes->nvwork = 0;
    3238:   snes->setupcalled = PETSC_FALSE;
    3239:   return(0);
    3240: }

    3242: /*@
    3243:    SNESConvergedReasonViewCancel - Clears all the reasonview functions for a SNES object.

    3245:    Collective on SNES

    3247:    Input Parameter:
    3248: .  snes - iterative context obtained from SNESCreate()

    3250:    Level: intermediate

    3252: .seealso: SNESCreate(), SNESDestroy(), SNESReset()
    3253: @*/
    3254: PetscErrorCode  SNESConvergedReasonViewCancel(SNES snes)
    3255: {
    3257:   PetscInt       i;

    3261:   for (i=0; i<snes->numberreasonviews; i++) {
    3262:     if (snes->reasonviewdestroy[i]) {
    3263:       (*snes->reasonviewdestroy[i])(&snes->reasonviewcontext[i]);
    3264:     }
    3265:   }
    3266:   snes->numberreasonviews = 0;
    3267:   return(0);
    3268: }

    3270: /*@C
    3271:    SNESDestroy - Destroys the nonlinear solver context that was created
    3272:    with SNESCreate().

    3274:    Collective on SNES

    3276:    Input Parameter:
    3277: .  snes - the SNES context

    3279:    Level: beginner

    3281: .seealso: SNESCreate(), SNESSolve()
    3282: @*/
    3283: PetscErrorCode  SNESDestroy(SNES *snes)
    3284: {

    3288:   if (!*snes) return(0);
    3290:   if (--((PetscObject)(*snes))->refct > 0) {*snes = NULL; return(0);}

    3292:   SNESReset((*snes));
    3293:   SNESDestroy(&(*snes)->npc);

    3295:   /* if memory was published with SAWs then destroy it */
    3296:   PetscObjectSAWsViewOff((PetscObject)*snes);
    3297:   if ((*snes)->ops->destroy) {(*((*snes))->ops->destroy)((*snes));}

    3299:   if ((*snes)->dm) {DMCoarsenHookRemove((*snes)->dm,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,*snes);}
    3300:   DMDestroy(&(*snes)->dm);
    3301:   KSPDestroy(&(*snes)->ksp);
    3302:   SNESLineSearchDestroy(&(*snes)->linesearch);

    3304:   PetscFree((*snes)->kspconvctx);
    3305:   if ((*snes)->ops->convergeddestroy) {
    3306:     (*(*snes)->ops->convergeddestroy)((*snes)->cnvP);
    3307:   }
    3308:   if ((*snes)->conv_hist_alloc) {
    3309:     PetscFree2((*snes)->conv_hist,(*snes)->conv_hist_its);
    3310:   }
    3311:   SNESMonitorCancel((*snes));
    3312:   SNESConvergedReasonViewCancel((*snes));
    3313:   PetscHeaderDestroy(snes);
    3314:   return(0);
    3315: }

    3317: /* ----------- Routines to set solver parameters ---------- */

    3319: /*@
    3320:    SNESSetLagPreconditioner - Determines when the preconditioner is rebuilt in the nonlinear solve.

    3322:    Logically Collective on SNES

    3324:    Input Parameters:
    3325: +  snes - the SNES context
    3326: -  lag - 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
    3327:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

    3329:    Options Database Keys:
    3330: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
    3331: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
    3332: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
    3333: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

    3335:    Notes:
    3336:    The default is 1
    3337:    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or SNESSetLagPreconditionerPersists() was called

    3339:    SNESSetLagPreconditionerPersists() allows using the same uniform lagging (for example every second solve) across multiple solves.

    3341:    Level: intermediate

    3343: .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESSetLagPreconditionerPersists(),
    3344:           SNESSetLagJacobianPersists()

    3346: @*/
    3347: PetscErrorCode  SNESSetLagPreconditioner(SNES snes,PetscInt lag)
    3348: {
    3351:   if (lag < -2) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag must be -2, -1, 1 or greater");
    3352:   if (!lag) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag cannot be 0");
    3354:   snes->lagpreconditioner = lag;
    3355:   return(0);
    3356: }

    3358: /*@
    3359:    SNESSetGridSequence - sets the number of steps of grid sequencing that SNES does

    3361:    Logically Collective on SNES

    3363:    Input Parameters:
    3364: +  snes - the SNES context
    3365: -  steps - the number of refinements to do, defaults to 0

    3367:    Options Database Keys:
    3368: .    -snes_grid_sequence <steps>

    3370:    Level: intermediate

    3372:    Notes:
    3373:    Use SNESGetSolution() to extract the fine grid solution after grid sequencing.

    3375: .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetGridSequence()

    3377: @*/
    3378: PetscErrorCode  SNESSetGridSequence(SNES snes,PetscInt steps)
    3379: {
    3383:   snes->gridsequence = steps;
    3384:   return(0);
    3385: }

    3387: /*@
    3388:    SNESGetGridSequence - gets the number of steps of grid sequencing that SNES does

    3390:    Logically Collective on SNES

    3392:    Input Parameter:
    3393: .  snes - the SNES context

    3395:    Output Parameter:
    3396: .  steps - the number of refinements to do, defaults to 0

    3398:    Options Database Keys:
    3399: .    -snes_grid_sequence <steps>

    3401:    Level: intermediate

    3403:    Notes:
    3404:    Use SNESGetSolution() to extract the fine grid solution after grid sequencing.

    3406: .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESSetGridSequence()

    3408: @*/
    3409: PetscErrorCode  SNESGetGridSequence(SNES snes,PetscInt *steps)
    3410: {
    3413:   *steps = snes->gridsequence;
    3414:   return(0);
    3415: }

    3417: /*@
    3418:    SNESGetLagPreconditioner - Indicates how often the preconditioner is rebuilt

    3420:    Not Collective

    3422:    Input Parameter:
    3423: .  snes - the SNES context

    3425:    Output Parameter:
    3426: .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
    3427:          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that

    3429:    Options Database Keys:
    3430: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
    3431: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
    3432: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
    3433: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

    3435:    Notes:
    3436:    The default is 1
    3437:    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1

    3439:    Level: intermediate

    3441: .seealso: SNESSetTrustRegionTolerance(), SNESSetLagPreconditioner(), SNESSetLagJacobianPersists(), SNESSetLagPreconditionerPersists()

    3443: @*/
    3444: PetscErrorCode  SNESGetLagPreconditioner(SNES snes,PetscInt *lag)
    3445: {
    3448:   *lag = snes->lagpreconditioner;
    3449:   return(0);
    3450: }

    3452: /*@
    3453:    SNESSetLagJacobian - Determines when the Jacobian is rebuilt in the nonlinear solve. See SNESSetLagPreconditioner() for determining how
    3454:      often the preconditioner is rebuilt.

    3456:    Logically Collective on SNES

    3458:    Input Parameters:
    3459: +  snes - the SNES context
    3460: -  lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
    3461:          the Jacobian is built etc. -2 means rebuild at next chance but then never again

    3463:    Options Database Keys:
    3464: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
    3465: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
    3466: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
    3467: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag.

    3469:    Notes:
    3470:    The default is 1
    3471:    The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
    3472:    If  -1 is used before the very first nonlinear solve the CODE WILL FAIL! because no Jacobian is used, use -2 to indicate you want it recomputed
    3473:    at the next Newton step but never again (unless it is reset to another value)

    3475:    Level: intermediate

    3477: .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagPreconditioner(), SNESGetLagJacobianPersists(), SNESSetLagPreconditionerPersists()

    3479: @*/
    3480: PetscErrorCode  SNESSetLagJacobian(SNES snes,PetscInt lag)
    3481: {
    3484:   if (lag < -2) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag must be -2, -1, 1 or greater");
    3485:   if (!lag) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag cannot be 0");
    3487:   snes->lagjacobian = lag;
    3488:   return(0);
    3489: }

    3491: /*@
    3492:    SNESGetLagJacobian - Indicates how often the Jacobian is rebuilt. See SNESGetLagPreconditioner() to determine when the preconditioner is rebuilt

    3494:    Not Collective

    3496:    Input Parameter:
    3497: .  snes - the SNES context

    3499:    Output Parameter:
    3500: .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
    3501:          the Jacobian is built etc.

    3503:    Notes:
    3504:    The default is 1
    3505:    The jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1 or SNESSetLagJacobianPersists() was called.

    3507:    Level: intermediate

    3509: .seealso: SNESSetTrustRegionTolerance(), SNESSetLagJacobian(), SNESSetLagPreconditioner(), SNESGetLagPreconditioner(), SNESSetLagJacobianPersists(), SNESSetLagPreconditionerPersists()

    3511: @*/
    3512: PetscErrorCode  SNESGetLagJacobian(SNES snes,PetscInt *lag)
    3513: {
    3516:   *lag = snes->lagjacobian;
    3517:   return(0);
    3518: }

    3520: /*@
    3521:    SNESSetLagJacobianPersists - Set whether or not the Jacobian lagging persists through multiple solves

    3523:    Logically collective on SNES

    3525:    Input Parameter:
    3526: +  snes - the SNES context
    3527: -   flg - jacobian lagging persists if true

    3529:    Options Database Keys:
    3530: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
    3531: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
    3532: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
    3533: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

    3536:    Notes:
    3537:     This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by
    3538:    several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several
    3539:    timesteps may present huge efficiency gains.

    3541:    Level: developer

    3543: .seealso: SNESSetLagPreconditionerPersists(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetNPC(), SNESSetLagJacobianPersists()

    3545: @*/
    3546: PetscErrorCode  SNESSetLagJacobianPersists(SNES snes,PetscBool flg)
    3547: {
    3551:   snes->lagjac_persist = flg;
    3552:   return(0);
    3553: }

    3555: /*@
    3556:    SNESSetLagPreconditionerPersists - Set whether or not the preconditioner lagging persists through multiple nonlinear solves

    3558:    Logically Collective on SNES

    3560:    Input Parameter:
    3561: +  snes - the SNES context
    3562: -   flg - preconditioner lagging persists if true

    3564:    Options Database Keys:
    3565: +    -snes_lag_jacobian_persists <true,false> - sets the persistence
    3566: .    -snes_lag_jacobian <-2,1,2,...> - sets the lag
    3567: .    -snes_lag_preconditioner_persists <true,false> - sets the persistence
    3568: -    -snes_lag_preconditioner <-2,1,2,...> - sets the lag

    3570:    Notes:
    3571:     This is useful both for nonlinear preconditioning, where it's appropriate to have the preconditioner be stale
    3572:    by several solves, and for implicit time-stepping, where preconditioner lagging in the inner nonlinear solve over
    3573:    several timesteps may present huge efficiency gains.

    3575:    Level: developer

    3577: .seealso: SNESSetLagJacobianPersists(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetNPC(), SNESSetLagPreconditioner()

    3579: @*/
    3580: PetscErrorCode  SNESSetLagPreconditionerPersists(SNES snes,PetscBool flg)
    3581: {
    3585:   snes->lagpre_persist = flg;
    3586:   return(0);
    3587: }

    3589: /*@
    3590:    SNESSetForceIteration - force SNESSolve() to take at least one iteration regardless of the initial residual norm

    3592:    Logically Collective on SNES

    3594:    Input Parameters:
    3595: +  snes - the SNES context
    3596: -  force - PETSC_TRUE require at least one iteration

    3598:    Options Database Keys:
    3599: .    -snes_force_iteration <force> - Sets forcing an iteration

    3601:    Notes:
    3602:    This is used sometimes with TS to prevent TS from detecting a false steady state solution

    3604:    Level: intermediate

    3606: .seealso: SNESSetTrustRegionTolerance(), SNESSetDivergenceTolerance()
    3607: @*/
    3608: PetscErrorCode  SNESSetForceIteration(SNES snes,PetscBool force)
    3609: {
    3612:   snes->forceiteration = force;
    3613:   return(0);
    3614: }

    3616: /*@
    3617:    SNESGetForceIteration - Whether or not to force SNESSolve() take at least one iteration regardless of the initial residual norm

    3619:    Logically Collective on SNES

    3621:    Input Parameters:
    3622: .  snes - the SNES context

    3624:    Output Parameter:
    3625: .  force - PETSC_TRUE requires at least one iteration.

    3627:    Level: intermediate

    3629: .seealso: SNESSetForceIteration(), SNESSetTrustRegionTolerance(), SNESSetDivergenceTolerance()
    3630: @*/
    3631: PetscErrorCode  SNESGetForceIteration(SNES snes,PetscBool *force)
    3632: {
    3635:   *force = snes->forceiteration;
    3636:   return(0);
    3637: }

    3639: /*@
    3640:    SNESSetTolerances - Sets various parameters used in convergence tests.

    3642:    Logically Collective on SNES

    3644:    Input Parameters:
    3645: +  snes - the SNES context
    3646: .  abstol - absolute convergence tolerance
    3647: .  rtol - relative convergence tolerance
    3648: .  stol -  convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
    3649: .  maxit - maximum number of iterations
    3650: -  maxf - maximum number of function evaluations (-1 indicates no limit)

    3652:    Options Database Keys:
    3653: +    -snes_atol <abstol> - Sets abstol
    3654: .    -snes_rtol <rtol> - Sets rtol
    3655: .    -snes_stol <stol> - Sets stol
    3656: .    -snes_max_it <maxit> - Sets maxit
    3657: -    -snes_max_funcs <maxf> - Sets maxf

    3659:    Notes:
    3660:    The default maximum number of iterations is 50.
    3661:    The default maximum number of function evaluations is 1000.

    3663:    Level: intermediate

    3665: .seealso: SNESSetTrustRegionTolerance(), SNESSetDivergenceTolerance(), SNESSetForceIteration()
    3666: @*/
    3667: PetscErrorCode  SNESSetTolerances(SNES snes,PetscReal abstol,PetscReal rtol,PetscReal stol,PetscInt maxit,PetscInt maxf)
    3668: {

    3677:   if (abstol != PETSC_DEFAULT) {
    3678:     if (abstol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Absolute tolerance %g must be non-negative",(double)abstol);
    3679:     snes->abstol = abstol;
    3680:   }
    3681:   if (rtol != PETSC_DEFAULT) {
    3682:     if (rtol < 0.0 || 1.0 <= rtol) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Relative tolerance %g must be non-negative and less than 1.0",(double)rtol);
    3683:     snes->rtol = rtol;
    3684:   }
    3685:   if (stol != PETSC_DEFAULT) {
    3686:     if (stol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Step tolerance %g must be non-negative",(double)stol);
    3687:     snes->stol = stol;
    3688:   }
    3689:   if (maxit != PETSC_DEFAULT) {
    3690:     if (maxit < 0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Maximum number of iterations %D must be non-negative",maxit);
    3691:     snes->max_its = maxit;
    3692:   }
    3693:   if (maxf != PETSC_DEFAULT) {
    3694:     if (maxf < -1) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Maximum number of function evaluations %D must be -1 or nonnegative",maxf);
    3695:     snes->max_funcs = maxf;
    3696:   }
    3697:   snes->tolerancesset = PETSC_TRUE;
    3698:   return(0);
    3699: }

    3701: /*@
    3702:    SNESSetDivergenceTolerance - Sets the divergence tolerance used for the SNES divergence test.

    3704:    Logically Collective on SNES

    3706:    Input Parameters:
    3707: +  snes - the SNES context
    3708: -  divtol - the divergence tolerance. Use -1 to deactivate the test.

    3710:    Options Database Keys:
    3711: .    -snes_divergence_tolerance <divtol> - Sets divtol

    3713:    Notes:
    3714:    The default divergence tolerance is 1e4.

    3716:    Level: intermediate

    3718: .seealso: SNESSetTolerances(), SNESGetDivergenceTolerance
    3719: @*/
    3720: PetscErrorCode  SNESSetDivergenceTolerance(SNES snes,PetscReal divtol)
    3721: {

    3726:   if (divtol != PETSC_DEFAULT) {
    3727:     snes->divtol = divtol;
    3728:   }
    3729:   else {
    3730:     snes->divtol = 1.0e4;
    3731:   }
    3732:   return(0);
    3733: }

    3735: /*@
    3736:    SNESGetTolerances - Gets various parameters used in convergence tests.

    3738:    Not Collective

    3740:    Input Parameters:
    3741: +  snes - the SNES context
    3742: .  atol - absolute convergence tolerance
    3743: .  rtol - relative convergence tolerance
    3744: .  stol -  convergence tolerance in terms of the norm
    3745:            of the change in the solution between steps
    3746: .  maxit - maximum number of iterations
    3747: -  maxf - maximum number of function evaluations

    3749:    Notes:
    3750:    The user can specify NULL for any parameter that is not needed.

    3752:    Level: intermediate

    3754: .seealso: SNESSetTolerances()
    3755: @*/
    3756: PetscErrorCode  SNESGetTolerances(SNES snes,PetscReal *atol,PetscReal *rtol,PetscReal *stol,PetscInt *maxit,PetscInt *maxf)
    3757: {
    3760:   if (atol)  *atol  = snes->abstol;
    3761:   if (rtol)  *rtol  = snes->rtol;
    3762:   if (stol)  *stol  = snes->stol;
    3763:   if (maxit) *maxit = snes->max_its;
    3764:   if (maxf)  *maxf  = snes->max_funcs;
    3765:   return(0);
    3766: }

    3768: /*@
    3769:    SNESGetDivergenceTolerance - Gets divergence tolerance used in divergence test.

    3771:    Not Collective

    3773:    Input Parameters:
    3774: +  snes - the SNES context
    3775: -  divtol - divergence tolerance

    3777:    Level: intermediate

    3779: .seealso: SNESSetDivergenceTolerance()
    3780: @*/
    3781: PetscErrorCode  SNESGetDivergenceTolerance(SNES snes,PetscReal *divtol)
    3782: {
    3785:   if (divtol) *divtol = snes->divtol;
    3786:   return(0);
    3787: }

    3789: /*@
    3790:    SNESSetTrustRegionTolerance - Sets the trust region parameter tolerance.

    3792:    Logically Collective on SNES

    3794:    Input Parameters:
    3795: +  snes - the SNES context
    3796: -  tol - tolerance

    3798:    Options Database Key:
    3799: .  -snes_trtol <tol> - Sets tol

    3801:    Level: intermediate

    3803: .seealso: SNESSetTolerances()
    3804: @*/
    3805: PetscErrorCode  SNESSetTrustRegionTolerance(SNES snes,PetscReal tol)
    3806: {
    3810:   snes->deltatol = tol;
    3811:   return(0);
    3812: }

    3814: PETSC_INTERN PetscErrorCode  SNESMonitorRange_Private(SNES,PetscInt,PetscReal*);

    3816: PetscErrorCode  SNESMonitorLGRange(SNES snes,PetscInt n,PetscReal rnorm,void *monctx)
    3817: {
    3818:   PetscDrawLG      lg;
    3819:   PetscErrorCode   ierr;
    3820:   PetscReal        x,y,per;
    3821:   PetscViewer      v = (PetscViewer)monctx;
    3822:   static PetscReal prev; /* should be in the context */
    3823:   PetscDraw        draw;

    3827:   PetscViewerDrawGetDrawLG(v,0,&lg);
    3828:   if (!n) {PetscDrawLGReset(lg);}
    3829:   PetscDrawLGGetDraw(lg,&draw);
    3830:   PetscDrawSetTitle(draw,"Residual norm");
    3831:   x    = (PetscReal)n;
    3832:   if (rnorm > 0.0) y = PetscLog10Real(rnorm);
    3833:   else y = -15.0;
    3834:   PetscDrawLGAddPoint(lg,&x,&y);
    3835:   if (n < 20 || !(n % 5) || snes->reason) {
    3836:     PetscDrawLGDraw(lg);
    3837:     PetscDrawLGSave(lg);
    3838:   }

    3840:   PetscViewerDrawGetDrawLG(v,1,&lg);
    3841:   if (!n) {PetscDrawLGReset(lg);}
    3842:   PetscDrawLGGetDraw(lg,&draw);
    3843:   PetscDrawSetTitle(draw,"% elemts > .2*max elemt");
    3844:    SNESMonitorRange_Private(snes,n,&per);
    3845:   x    = (PetscReal)n;
    3846:   y    = 100.0*per;
    3847:   PetscDrawLGAddPoint(lg,&x,&y);
    3848:   if (n < 20 || !(n % 5) || snes->reason) {
    3849:     PetscDrawLGDraw(lg);
    3850:     PetscDrawLGSave(lg);
    3851:   }

    3853:   PetscViewerDrawGetDrawLG(v,2,&lg);
    3854:   if (!n) {prev = rnorm;PetscDrawLGReset(lg);}
    3855:   PetscDrawLGGetDraw(lg,&draw);
    3856:   PetscDrawSetTitle(draw,"(norm -oldnorm)/oldnorm");
    3857:   x    = (PetscReal)n;
    3858:   y    = (prev - rnorm)/prev;
    3859:   PetscDrawLGAddPoint(lg,&x,&y);
    3860:   if (n < 20 || !(n % 5) || snes->reason) {
    3861:     PetscDrawLGDraw(lg);
    3862:     PetscDrawLGSave(lg);
    3863:   }

    3865:   PetscViewerDrawGetDrawLG(v,3,&lg);
    3866:   if (!n) {PetscDrawLGReset(lg);}
    3867:   PetscDrawLGGetDraw(lg,&draw);
    3868:   PetscDrawSetTitle(draw,"(norm -oldnorm)/oldnorm*(% > .2 max)");
    3869:   x    = (PetscReal)n;
    3870:   y    = (prev - rnorm)/(prev*per);
    3871:   if (n > 2) { /*skip initial crazy value */
    3872:     PetscDrawLGAddPoint(lg,&x,&y);
    3873:   }
    3874:   if (n < 20 || !(n % 5) || snes->reason) {
    3875:     PetscDrawLGDraw(lg);
    3876:     PetscDrawLGSave(lg);
    3877:   }
    3878:   prev = rnorm;
    3879:   return(0);
    3880: }

    3882: /*@
    3883:    SNESMonitor - runs the user provided monitor routines, if they exist

    3885:    Collective on SNES

    3887:    Input Parameters:
    3888: +  snes - nonlinear solver context obtained from SNESCreate()
    3889: .  iter - iteration number
    3890: -  rnorm - relative norm of the residual

    3892:    Notes:
    3893:    This routine is called by the SNES implementations.
    3894:    It does not typically need to be called by the user.

    3896:    Level: developer

    3898: .seealso: SNESMonitorSet()
    3899: @*/
    3900: PetscErrorCode  SNESMonitor(SNES snes,PetscInt iter,PetscReal rnorm)
    3901: {
    3903:   PetscInt       i,n = snes->numbermonitors;

    3906:   VecLockReadPush(snes->vec_sol);
    3907:   for (i=0; i<n; i++) {
    3908:     (*snes->monitor[i])(snes,iter,rnorm,snes->monitorcontext[i]);
    3909:   }
    3910:   VecLockReadPop(snes->vec_sol);
    3911:   return(0);
    3912: }

    3914: /* ------------ Routines to set performance monitoring options ----------- */

    3916: /*MC
    3917:     SNESMonitorFunction - functional form passed to SNESMonitorSet() to monitor convergence of nonlinear solver

    3919:      Synopsis:
    3920: #include <petscsnes.h>
    3921: $    PetscErrorCode SNESMonitorFunction(SNES snes,PetscInt its, PetscReal norm,void *mctx)

    3923:      Collective on snes

    3925:     Input Parameters:
    3926: +    snes - the SNES context
    3927: .    its - iteration number
    3928: .    norm - 2-norm function value (may be estimated)
    3929: -    mctx - [optional] monitoring context

    3931:    Level: advanced

    3933: .seealso:   SNESMonitorSet(), SNESMonitorGet()
    3934: M*/

    3936: /*@C
    3937:    SNESMonitorSet - Sets an ADDITIONAL function that is to be used at every
    3938:    iteration of the nonlinear solver to display the iteration's
    3939:    progress.

    3941:    Logically Collective on SNES

    3943:    Input Parameters:
    3944: +  snes - the SNES context
    3945: .  f - the monitor function, see SNESMonitorFunction for the calling sequence
    3946: .  mctx - [optional] user-defined context for private data for the
    3947:           monitor routine (use NULL if no context is desired)
    3948: -  monitordestroy - [optional] routine that frees monitor context
    3949:           (may be NULL)

    3951:    Options Database Keys:
    3952: +    -snes_monitor        - sets SNESMonitorDefault()
    3953: .    -snes_monitor draw::draw_lg - sets line graph monitor,
    3954: -    -snes_monitor_cancel - cancels all monitors that have
    3955:                             been hardwired into a code by
    3956:                             calls to SNESMonitorSet(), but
    3957:                             does not cancel those set via
    3958:                             the options database.

    3960:    Notes:
    3961:    Several different monitoring routines may be set by calling
    3962:    SNESMonitorSet() multiple times; all will be called in the
    3963:    order in which they were set.

    3965:    Fortran Notes:
    3966:     Only a single monitor function can be set for each SNES object

    3968:    Level: intermediate

    3970: .seealso: SNESMonitorDefault(), SNESMonitorCancel(), SNESMonitorFunction
    3971: @*/
    3972: PetscErrorCode  SNESMonitorSet(SNES snes,PetscErrorCode (*f)(SNES,PetscInt,PetscReal,void*),void *mctx,PetscErrorCode (*monitordestroy)(void**))
    3973: {
    3974:   PetscInt       i;
    3976:   PetscBool      identical;

    3980:   for (i=0; i<snes->numbermonitors;i++) {
    3981:     PetscMonitorCompare((PetscErrorCode (*)(void))f,mctx,monitordestroy,(PetscErrorCode (*)(void))snes->monitor[i],snes->monitorcontext[i],snes->monitordestroy[i],&identical);
    3982:     if (identical) return(0);
    3983:   }
    3984:   if (snes->numbermonitors >= MAXSNESMONITORS) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Too many monitors set");
    3985:   snes->monitor[snes->numbermonitors]          = f;
    3986:   snes->monitordestroy[snes->numbermonitors]   = monitordestroy;
    3987:   snes->monitorcontext[snes->numbermonitors++] = (void*)mctx;
    3988:   return(0);
    3989: }

    3991: /*@
    3992:    SNESMonitorCancel - Clears all the monitor functions for a SNES object.

    3994:    Logically Collective on SNES

    3996:    Input Parameters:
    3997: .  snes - the SNES context

    3999:    Options Database Key:
    4000: .  -snes_monitor_cancel - cancels all monitors that have been hardwired
    4001:     into a code by calls to SNESMonitorSet(), but does not cancel those
    4002:     set via the options database

    4004:    Notes:
    4005:    There is no way to clear one specific monitor from a SNES object.

    4007:    Level: intermediate

    4009: .seealso: SNESMonitorDefault(), SNESMonitorSet()
    4010: @*/
    4011: PetscErrorCode  SNESMonitorCancel(SNES snes)
    4012: {
    4014:   PetscInt       i;

    4018:   for (i=0; i<snes->numbermonitors; i++) {
    4019:     if (snes->monitordestroy[i]) {
    4020:       (*snes->monitordestroy[i])(&snes->monitorcontext[i]);
    4021:     }
    4022:   }
    4023:   snes->numbermonitors = 0;
    4024:   return(0);
    4025: }

    4027: /*MC
    4028:     SNESConvergenceTestFunction - functional form used for testing of convergence of nonlinear solver

    4030:      Synopsis:
    4031: #include <petscsnes.h>
    4032: $     PetscErrorCode SNESConvergenceTest(SNES snes,PetscInt it,PetscReal xnorm,PetscReal gnorm,PetscReal f,SNESConvergedReason *reason,void *cctx)

    4034:      Collective on snes

    4036:     Input Parameters:
    4037: +    snes - the SNES context
    4038: .    it - current iteration (0 is the first and is before any Newton step)
    4039: .    xnorm - 2-norm of current iterate
    4040: .    gnorm - 2-norm of current step
    4041: .    f - 2-norm of function
    4042: -    cctx - [optional] convergence context

    4044:     Output Parameter:
    4045: .    reason - reason for convergence/divergence, only needs to be set when convergence or divergence is detected

    4047:    Level: intermediate

    4049: .seealso:   SNESSetConvergenceTest(), SNESGetConvergenceTest()
    4050: M*/

    4052: /*@C
    4053:    SNESSetConvergenceTest - Sets the function that is to be used
    4054:    to test for convergence of the nonlinear iterative solution.

    4056:    Logically Collective on SNES

    4058:    Input Parameters:
    4059: +  snes - the SNES context
    4060: .  SNESConvergenceTestFunction - routine to test for convergence
    4061: .  cctx - [optional] context for private data for the convergence routine  (may be NULL)
    4062: -  destroy - [optional] destructor for the context (may be NULL; PETSC_NULL_FUNCTION in Fortran)

    4064:    Level: advanced

    4066: .seealso: SNESConvergedDefault(), SNESConvergedSkip(), SNESConvergenceTestFunction
    4067: @*/
    4068: PetscErrorCode  SNESSetConvergenceTest(SNES snes,PetscErrorCode (*SNESConvergenceTestFunction)(SNES,PetscInt,PetscReal,PetscReal,PetscReal,SNESConvergedReason*,void*),void *cctx,PetscErrorCode (*destroy)(void*))
    4069: {

    4074:   if (!SNESConvergenceTestFunction) SNESConvergenceTestFunction = SNESConvergedSkip;
    4075:   if (snes->ops->convergeddestroy) {
    4076:     (*snes->ops->convergeddestroy)(snes->cnvP);
    4077:   }
    4078:   snes->ops->converged        = SNESConvergenceTestFunction;
    4079:   snes->ops->convergeddestroy = destroy;
    4080:   snes->cnvP                  = cctx;
    4081:   return(0);
    4082: }

    4084: /*@
    4085:    SNESGetConvergedReason - Gets the reason the SNES iteration was stopped.

    4087:    Not Collective

    4089:    Input Parameter:
    4090: .  snes - the SNES context

    4092:    Output Parameter:
    4093: .  reason - negative value indicates diverged, positive value converged, see SNESConvergedReason or the
    4094:             manual pages for the individual convergence tests for complete lists

    4096:    Options Database:
    4097: .   -snes_converged_reason - prints the reason to standard out

    4099:    Level: intermediate

    4101:    Notes:
    4102:     Should only be called after the call the SNESSolve() is complete, if it is called earlier it returns the value SNES__CONVERGED_ITERATING.

    4104: .seealso: SNESSetConvergenceTest(), SNESSetConvergedReason(), SNESConvergedReason
    4105: @*/
    4106: PetscErrorCode SNESGetConvergedReason(SNES snes,SNESConvergedReason *reason)
    4107: {
    4111:   *reason = snes->reason;
    4112:   return(0);
    4113: }

    4115: /*@C
    4116:    SNESGetConvergedReasonString - Return a human readable string for snes converged reason

    4118:    Not Collective

    4120:    Input Parameter:
    4121: .  snes - the SNES context

    4123:    Output Parameter:
    4124: .  strreason - a human readable string that describes SNES converged reason

    4126:    Level: beginner

    4128: .seealso: SNESGetConvergedReason()
    4129: @*/
    4130: PetscErrorCode SNESGetConvergedReasonString(SNES snes, const char** strreason)
    4131: {
    4135:   *strreason = SNESConvergedReasons[snes->reason];
    4136:   return(0);
    4137: }

    4139: /*@
    4140:    SNESSetConvergedReason - Sets the reason the SNES iteration was stopped.

    4142:    Not Collective

    4144:    Input Parameters:
    4145: +  snes - the SNES context
    4146: -  reason - negative value indicates diverged, positive value converged, see SNESConvergedReason or the
    4147:             manual pages for the individual convergence tests for complete lists

    4149:    Level: intermediate

    4151: .seealso: SNESGetConvergedReason(), SNESSetConvergenceTest(), SNESConvergedReason
    4152: @*/
    4153: PetscErrorCode SNESSetConvergedReason(SNES snes,SNESConvergedReason reason)
    4154: {
    4157:   snes->reason = reason;
    4158:   return(0);
    4159: }

    4161: /*@
    4162:    SNESSetConvergenceHistory - Sets the array used to hold the convergence history.

    4164:    Logically Collective on SNES

    4166:    Input Parameters:
    4167: +  snes - iterative context obtained from SNESCreate()
    4168: .  a   - array to hold history, this array will contain the function norms computed at each step
    4169: .  its - integer array holds the number of linear iterations for each solve.
    4170: .  na  - size of a and its
    4171: -  reset - PETSC_TRUE indicates each new nonlinear solve resets the history counter to zero,
    4172:            else it continues storing new values for new nonlinear solves after the old ones

    4174:    Notes:
    4175:    If 'a' and 'its' are NULL then space is allocated for the history. If 'na' PETSC_DECIDE or PETSC_DEFAULT then a
    4176:    default array of length 10000 is allocated.

    4178:    This routine is useful, e.g., when running a code for purposes
    4179:    of accurate performance monitoring, when no I/O should be done
    4180:    during the section of code that is being timed.

    4182:    Level: intermediate

    4184: .seealso: SNESGetConvergenceHistory()

    4186: @*/
    4187: PetscErrorCode  SNESSetConvergenceHistory(SNES snes,PetscReal a[],PetscInt its[],PetscInt na,PetscBool reset)
    4188: {

    4195:   if (!a) {
    4196:     if (na == PETSC_DECIDE || na == PETSC_DEFAULT) na = 1000;
    4197:     PetscCalloc2(na,&a,na,&its);
    4198:     snes->conv_hist_alloc = PETSC_TRUE;
    4199:   }
    4200:   snes->conv_hist       = a;
    4201:   snes->conv_hist_its   = its;
    4202:   snes->conv_hist_max   = na;
    4203:   snes->conv_hist_len   = 0;
    4204:   snes->conv_hist_reset = reset;
    4205:   return(0);
    4206: }

    4208: #if defined(PETSC_HAVE_MATLAB_ENGINE)
    4209: #include <engine.h>   /* MATLAB include file */
    4210: #include <mex.h>      /* MATLAB include file */

    4212: PETSC_EXTERN mxArray *SNESGetConvergenceHistoryMatlab(SNES snes)
    4213: {
    4214:   mxArray   *mat;
    4215:   PetscInt  i;
    4216:   PetscReal *ar;

    4219:   mat = mxCreateDoubleMatrix(snes->conv_hist_len,1,mxREAL);
    4220:   ar  = (PetscReal*) mxGetData(mat);
    4221:   for (i=0; i<snes->conv_hist_len; i++) ar[i] = snes->conv_hist[i];
    4222:   PetscFunctionReturn(mat);
    4223: }
    4224: #endif

    4226: /*@C
    4227:    SNESGetConvergenceHistory - Gets the array used to hold the convergence history.

    4229:    Not Collective

    4231:    Input Parameter:
    4232: .  snes - iterative context obtained from SNESCreate()

    4234:    Output Parameters:
    4235: +  a   - array to hold history
    4236: .  its - integer array holds the number of linear iterations (or
    4237:          negative if not converged) for each solve.
    4238: -  na  - size of a and its

    4240:    Notes:
    4241:     The calling sequence for this routine in Fortran is
    4242: $   call SNESGetConvergenceHistory(SNES snes, integer na, integer ierr)

    4244:    This routine is useful, e.g., when running a code for purposes
    4245:    of accurate performance monitoring, when no I/O should be done
    4246:    during the section of code that is being timed.

    4248:    Level: intermediate

    4250: .seealso: SNESSetConvergenceHistory()

    4252: @*/
    4253: PetscErrorCode  SNESGetConvergenceHistory(SNES snes,PetscReal *a[],PetscInt *its[],PetscInt *na)
    4254: {
    4257:   if (a)   *a   = snes->conv_hist;
    4258:   if (its) *its = snes->conv_hist_its;
    4259:   if (na)  *na  = snes->conv_hist_len;
    4260:   return(0);
    4261: }

    4263: /*@C
    4264:   SNESSetUpdate - Sets the general-purpose update function called
    4265:   at the beginning of every iteration of the nonlinear solve. Specifically
    4266:   it is called just before the Jacobian is "evaluated".

    4268:   Logically Collective on SNES

    4270:   Input Parameters:
    4271: + snes - The nonlinear solver context
    4272: - func - The function

    4274:   Calling sequence of func:
    4275: $ func (SNES snes, PetscInt step);

    4277: . step - The current step of the iteration

    4279:   Level: advanced

    4281:   Note: This is NOT what one uses to update the ghost points before a function evaluation, that should be done at the beginning of your FormFunction()
    4282:         This is not used by most users.

    4284: .seealso SNESSetJacobian(), SNESSolve()
    4285: @*/
    4286: PetscErrorCode  SNESSetUpdate(SNES snes, PetscErrorCode (*func)(SNES, PetscInt))
    4287: {
    4290:   snes->ops->update = func;
    4291:   return(0);
    4292: }

    4294: /*
    4295:    SNESScaleStep_Private - Scales a step so that its length is less than the
    4296:    positive parameter delta.

    4298:     Input Parameters:
    4299: +   snes - the SNES context
    4300: .   y - approximate solution of linear system
    4301: .   fnorm - 2-norm of current function
    4302: -   delta - trust region size

    4304:     Output Parameters:
    4305: +   gpnorm - predicted function norm at the new point, assuming local
    4306:     linearization.  The value is zero if the step lies within the trust
    4307:     region, and exceeds zero otherwise.
    4308: -   ynorm - 2-norm of the step

    4310:     Note:
    4311:     For non-trust region methods such as SNESNEWTONLS, the parameter delta
    4312:     is set to be the maximum allowable step size.

    4314: */
    4315: PetscErrorCode SNESScaleStep_Private(SNES snes,Vec y,PetscReal *fnorm,PetscReal *delta,PetscReal *gpnorm,PetscReal *ynorm)
    4316: {
    4317:   PetscReal      nrm;
    4318:   PetscScalar    cnorm;

    4326:   VecNorm(y,NORM_2,&nrm);
    4327:   if (nrm > *delta) {
    4328:     nrm     = *delta/nrm;
    4329:     *gpnorm = (1.0 - nrm)*(*fnorm);
    4330:     cnorm   = nrm;
    4331:     VecScale(y,cnorm);
    4332:     *ynorm  = *delta;
    4333:   } else {
    4334:     *gpnorm = 0.0;
    4335:     *ynorm  = nrm;
    4336:   }
    4337:   return(0);
    4338: }

    4340: /*@C
    4341:    SNESConvergedReasonView - Displays the reason a SNES solve converged or diverged to a viewer

    4343:    Collective on SNES

    4345:    Parameter:
    4346: +  snes - iterative context obtained from SNESCreate()
    4347: -  viewer - the viewer to display the reason

    4350:    Options Database Keys:
    4351: +  -snes_converged_reason - print reason for converged or diverged, also prints number of iterations
    4352: -  -snes_converged_reason ::failed - only print reason and number of iterations when diverged

    4354:   Notes:
    4355:      To change the format of the output call PetscViewerPushFormat(viewer,format) before this call. Use PETSC_VIEWER_DEFAULT for the default,
    4356:      use PETSC_VIEWER_FAILED to only display a reason if it fails.

    4358:    Level: beginner

    4360: .seealso: SNESCreate(), SNESSetUp(), SNESDestroy(), SNESSetTolerances(), SNESConvergedDefault(), SNESGetConvergedReason(), SNESConvergedReasonViewFromOptions(),
    4361:           PetscViewerPushFormat(), PetscViewerPopFormat()

    4363: @*/
    4364: PetscErrorCode  SNESConvergedReasonView(SNES snes,PetscViewer viewer)
    4365: {
    4366:   PetscViewerFormat format;
    4367:   PetscBool         isAscii;
    4368:   PetscErrorCode    ierr;

    4371:   if (!viewer) viewer = PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes));
    4372:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&isAscii);
    4373:   if (isAscii) {
    4374:     PetscViewerGetFormat(viewer, &format);
    4375:     PetscViewerASCIIAddTab(viewer,((PetscObject)snes)->tablevel);
    4376:     if (format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
    4377:       DM              dm;
    4378:       Vec             u;
    4379:       PetscDS         prob;
    4380:       PetscInt        Nf, f;
    4381:       PetscErrorCode (**exactSol)(PetscInt, PetscReal, const PetscReal[], PetscInt, PetscScalar[], void *);
    4382:       void            **exactCtx;
    4383:       PetscReal       error;

    4385:       SNESGetDM(snes, &dm);
    4386:       SNESGetSolution(snes, &u);
    4387:       DMGetDS(dm, &prob);
    4388:       PetscDSGetNumFields(prob, &Nf);
    4389:       PetscMalloc2(Nf, &exactSol, Nf, &exactCtx);
    4390:       for (f = 0; f < Nf; ++f) {PetscDSGetExactSolution(prob, f, &exactSol[f], &exactCtx[f]);}
    4391:       DMComputeL2Diff(dm, 0.0, exactSol, exactCtx, u, &error);
    4392:       PetscFree2(exactSol, exactCtx);
    4393:       if (error < 1.0e-11) {PetscViewerASCIIPrintf(viewer, "L_2 Error: < 1.0e-11\n");}
    4394:       else                 {PetscViewerASCIIPrintf(viewer, "L_2 Error: %g\n", error);}
    4395:     }
    4396:     if (snes->reason > 0 && format != PETSC_VIEWER_FAILED) {
    4397:       if (((PetscObject) snes)->prefix) {
    4398:         PetscViewerASCIIPrintf(viewer,"Nonlinear %s solve converged due to %s iterations %D\n",((PetscObject) snes)->prefix,SNESConvergedReasons[snes->reason],snes->iter);
    4399:       } else {
    4400:         PetscViewerASCIIPrintf(viewer,"Nonlinear solve converged due to %s iterations %D\n",SNESConvergedReasons[snes->reason],snes->iter);
    4401:       }
    4402:     } else if (snes->reason <= 0) {
    4403:       if (((PetscObject) snes)->prefix) {
    4404:         PetscViewerASCIIPrintf(viewer,"Nonlinear %s solve did not converge due to %s iterations %D\n",((PetscObject) snes)->prefix,SNESConvergedReasons[snes->reason],snes->iter);
    4405:       } else {
    4406:         PetscViewerASCIIPrintf(viewer,"Nonlinear solve did not converge due to %s iterations %D\n",SNESConvergedReasons[snes->reason],snes->iter);
    4407:       }
    4408:     }
    4409:     PetscViewerASCIISubtractTab(viewer,((PetscObject)snes)->tablevel);
    4410:   }
    4411:   return(0);
    4412: }

    4414: /*@C
    4415:    SNESConvergedReasonViewSet - Sets an ADDITIONAL function that is to be used at the
    4416:     end of the nonlinear solver to display the conver reason of the nonlinear solver.

    4418:    Logically Collective on SNES

    4420:    Input Parameters:
    4421: +  snes - the SNES context
    4422: .  f - the snes converged reason view function
    4423: .  vctx - [optional] user-defined context for private data for the
    4424:           snes converged reason view routine (use NULL if no context is desired)
    4425: -  reasonviewdestroy - [optional] routine that frees reasonview context
    4426:           (may be NULL)

    4428:    Options Database Keys:
    4429: +    -snes_converged_reason        - sets a default SNESConvergedReasonView()
    4430: -    -snes_converged_reason_view_cancel - cancels all converged reason viewers that have
    4431:                             been hardwired into a code by
    4432:                             calls to SNESConvergedReasonViewSet(), but
    4433:                             does not cancel those set via
    4434:                             the options database.

    4436:    Notes:
    4437:    Several different converged reason view routines may be set by calling
    4438:    SNESConvergedReasonViewSet() multiple times; all will be called in the
    4439:    order in which they were set.

    4441:    Level: intermediate

    4443: .seealso: SNESConvergedReasonView(), SNESConvergedReasonViewCancel()
    4444: @*/
    4445: PetscErrorCode  SNESConvergedReasonViewSet(SNES snes,PetscErrorCode (*f)(SNES,void*),void *vctx,PetscErrorCode (*reasonviewdestroy)(void**))
    4446: {
    4447:   PetscInt       i;
    4449:   PetscBool      identical;

    4453:   for (i=0; i<snes->numberreasonviews;i++) {
    4454:     PetscMonitorCompare((PetscErrorCode (*)(void))f,vctx,reasonviewdestroy,(PetscErrorCode (*)(void))snes->reasonview[i],snes->reasonviewcontext[i],snes->reasonviewdestroy[i],&identical);
    4455:     if (identical) return(0);
    4456:   }
    4457:   if (snes->numberreasonviews >= MAXSNESREASONVIEWS) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Too many SNES reasonview set");
    4458:   snes->reasonview[snes->numberreasonviews]          = f;
    4459:   snes->reasonviewdestroy[snes->numberreasonviews]   = reasonviewdestroy;
    4460:   snes->reasonviewcontext[snes->numberreasonviews++] = (void*)vctx;
    4461:   return(0);
    4462: }

    4464: /*@
    4465:   SNESConvergedReasonViewFromOptions - Processes command line options to determine if/how a SNESReason is to be viewed.
    4466:                                        All the user-provided convergedReasonView routines will be involved as well, if they exist.

    4468:   Collective on SNES

    4470:   Input Parameters:
    4471: . snes   - the SNES object

    4473:   Level: intermediate

    4475: .seealso: SNESCreate(), SNESSetUp(), SNESDestroy(), SNESSetTolerances(), SNESConvergedDefault(), SNESGetConvergedReason(), SNESConvergedReasonView()

    4477: @*/
    4478: PetscErrorCode SNESConvergedReasonViewFromOptions(SNES snes)
    4479: {
    4480:   PetscErrorCode    ierr;
    4481:   PetscViewer       viewer;
    4482:   PetscBool         flg;
    4483:   static PetscBool  incall = PETSC_FALSE;
    4484:   PetscViewerFormat format;
    4485:   PetscInt          i;

    4488:   if (incall) return(0);
    4489:   incall = PETSC_TRUE;

    4491:   /* All user-provided viewers are called first, if they exist. */
    4492:   for (i=0; i<snes->numberreasonviews; i++) {
    4493:     (*snes->reasonview[i])(snes,snes->reasonviewcontext[i]);
    4494:   }

    4496:   /* Call PETSc default routine if users ask for it */
    4497:   PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_converged_reason",&viewer,&format,&flg);
    4498:   if (flg) {
    4499:     PetscViewerPushFormat(viewer,format);
    4500:     SNESConvergedReasonView(snes,viewer);
    4501:     PetscViewerPopFormat(viewer);
    4502:     PetscViewerDestroy(&viewer);
    4503:   }
    4504:   incall = PETSC_FALSE;
    4505:   return(0);
    4506: }

    4508: /*@
    4509:    SNESSolve - Solves a nonlinear system F(x) = b.
    4510:    Call SNESSolve() after calling SNESCreate() and optional routines of the form SNESSetXXX().

    4512:    Collective on SNES

    4514:    Input Parameters:
    4515: +  snes - the SNES context
    4516: .  b - the constant part of the equation F(x) = b, or NULL to use zero.
    4517: -  x - the solution vector.

    4519:    Notes:
    4520:    The user should initialize the vector,x, with the initial guess
    4521:    for the nonlinear solve prior to calling SNESSolve.  In particular,
    4522:    to employ an initial guess of zero, the user should explicitly set
    4523:    this vector to zero by calling VecSet().

    4525:    Level: beginner

    4527: .seealso: SNESCreate(), SNESDestroy(), SNESSetFunction(), SNESSetJacobian(), SNESSetGridSequence(), SNESGetSolution()
    4528: @*/
    4529: PetscErrorCode  SNESSolve(SNES snes,Vec b,Vec x)
    4530: {
    4531:   PetscErrorCode    ierr;
    4532:   PetscBool         flg;
    4533:   PetscInt          grid;
    4534:   Vec               xcreated = NULL;
    4535:   DM                dm;

    4544:   /* High level operations using the nonlinear solver */
    4545:   {
    4546:     PetscViewer       viewer;
    4547:     PetscViewerFormat format;
    4548:     PetscInt          num;
    4549:     PetscBool         flg;
    4550:     static PetscBool  incall = PETSC_FALSE;

    4552:     if (!incall) {
    4553:       /* Estimate the convergence rate of the discretization */
    4554:       PetscOptionsGetViewer(PetscObjectComm((PetscObject) snes),((PetscObject)snes)->options, ((PetscObject) snes)->prefix, "-snes_convergence_estimate", &viewer, &format, &flg);
    4555:       if (flg) {
    4556:         PetscConvEst conv;
    4557:         DM           dm;
    4558:         PetscReal   *alpha; /* Convergence rate of the solution error for each field in the L_2 norm */
    4559:         PetscInt     Nf;

    4561:         incall = PETSC_TRUE;
    4562:         SNESGetDM(snes, &dm);
    4563:         DMGetNumFields(dm, &Nf);
    4564:         PetscCalloc1(Nf, &alpha);
    4565:         PetscConvEstCreate(PetscObjectComm((PetscObject) snes), &conv);
    4566:         PetscConvEstSetSolver(conv, (PetscObject) snes);
    4567:         PetscConvEstSetFromOptions(conv);
    4568:         PetscConvEstSetUp(conv);
    4569:         PetscConvEstGetConvRate(conv, alpha);
    4570:         PetscViewerPushFormat(viewer, format);
    4571:         PetscConvEstRateView(conv, alpha, viewer);
    4572:         PetscViewerPopFormat(viewer);
    4573:         PetscViewerDestroy(&viewer);
    4574:         PetscConvEstDestroy(&conv);
    4575:         PetscFree(alpha);
    4576:         incall = PETSC_FALSE;
    4577:       }
    4578:       /* Adaptively refine the initial grid */
    4579:       num  = 1;
    4580:       PetscOptionsGetInt(NULL, ((PetscObject) snes)->prefix, "-snes_adapt_initial", &num, &flg);
    4581:       if (flg) {
    4582:         DMAdaptor adaptor;

    4584:         incall = PETSC_TRUE;
    4585:         DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor);
    4586:         DMAdaptorSetSolver(adaptor, snes);
    4587:         DMAdaptorSetSequenceLength(adaptor, num);
    4588:         DMAdaptorSetFromOptions(adaptor);
    4589:         DMAdaptorSetUp(adaptor);
    4590:         DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_INITIAL, &dm, &x);
    4591:         DMAdaptorDestroy(&adaptor);
    4592:         incall = PETSC_FALSE;
    4593:       }
    4594:       /* Use grid sequencing to adapt */
    4595:       num  = 0;
    4596:       PetscOptionsGetInt(NULL, ((PetscObject) snes)->prefix, "-snes_adapt_sequence", &num, NULL);
    4597:       if (num) {
    4598:         DMAdaptor adaptor;

    4600:         incall = PETSC_TRUE;
    4601:         DMAdaptorCreate(PetscObjectComm((PetscObject)snes), &adaptor);
    4602:         DMAdaptorSetSolver(adaptor, snes);
    4603:         DMAdaptorSetSequenceLength(adaptor, num);
    4604:         DMAdaptorSetFromOptions(adaptor);
    4605:         DMAdaptorSetUp(adaptor);
    4606:         DMAdaptorAdapt(adaptor, x, DM_ADAPTATION_SEQUENTIAL, &dm, &x);
    4607:         DMAdaptorDestroy(&adaptor);
    4608:         incall = PETSC_FALSE;
    4609:       }
    4610:     }
    4611:   }
    4612:   if (!x) {
    4613:     SNESGetDM(snes,&dm);
    4614:     DMCreateGlobalVector(dm,&xcreated);
    4615:     x    = xcreated;
    4616:   }
    4617:   SNESViewFromOptions(snes,NULL,"-snes_view_pre");

    4619:   for (grid=0; grid<snes->gridsequence; grid++) {PetscViewerASCIIPushTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)));}
    4620:   for (grid=0; grid<snes->gridsequence+1; grid++) {

    4622:     /* set solution vector */
    4623:     if (!grid) {PetscObjectReference((PetscObject)x);}
    4624:     VecDestroy(&snes->vec_sol);
    4625:     snes->vec_sol = x;
    4626:     SNESGetDM(snes,&dm);

    4628:     /* set affine vector if provided */
    4629:     if (b) { PetscObjectReference((PetscObject)b); }
    4630:     VecDestroy(&snes->vec_rhs);
    4631:     snes->vec_rhs = b;

    4633:     if (snes->vec_rhs && (snes->vec_func == snes->vec_rhs)) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_IDN,"Right hand side vector cannot be function vector");
    4634:     if (snes->vec_func == snes->vec_sol) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_IDN,"Solution vector cannot be function vector");
    4635:     if (snes->vec_rhs  == snes->vec_sol) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_IDN,"Solution vector cannot be right hand side vector");
    4636:     if (!snes->vec_sol_update /* && snes->vec_sol */) {
    4637:       VecDuplicate(snes->vec_sol,&snes->vec_sol_update);
    4638:       PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->vec_sol_update);
    4639:     }
    4640:     DMShellSetGlobalVector(dm,snes->vec_sol);
    4641:     SNESSetUp(snes);

    4643:     if (!grid) {
    4644:       if (snes->ops->computeinitialguess) {
    4645:         (*snes->ops->computeinitialguess)(snes,snes->vec_sol,snes->initialguessP);
    4646:       }
    4647:     }

    4649:     if (snes->conv_hist_reset) snes->conv_hist_len = 0;
    4650:     if (snes->counters_reset) {snes->nfuncs = 0; snes->linear_its = 0; snes->numFailures = 0;}

    4652:     PetscLogEventBegin(SNES_Solve,snes,0,0,0);
    4653:     (*snes->ops->solve)(snes);
    4654:     PetscLogEventEnd(SNES_Solve,snes,0,0,0);
    4655:     if (!snes->reason) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Internal error, solver returned without setting converged reason");
    4656:     snes->domainerror = PETSC_FALSE; /* clear the flag if it has been set */

    4658:     if (snes->lagjac_persist) snes->jac_iter += snes->iter;
    4659:     if (snes->lagpre_persist) snes->pre_iter += snes->iter;

    4661:     PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->options,((PetscObject)snes)->prefix,"-snes_test_local_min",NULL,NULL,&flg);
    4662:     if (flg && !PetscPreLoadingOn) { SNESTestLocalMin(snes); }
    4663:     /* Call converged reason views. This may involve user-provided viewers as well */
    4664:     SNESConvergedReasonViewFromOptions(snes);

    4666:     if (snes->errorifnotconverged && snes->reason < 0) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_NOT_CONVERGED,"SNESSolve has not converged");
    4667:     if (snes->reason < 0) break;
    4668:     if (grid <  snes->gridsequence) {
    4669:       DM  fine;
    4670:       Vec xnew;
    4671:       Mat interp;

    4673:       DMRefine(snes->dm,PetscObjectComm((PetscObject)snes),&fine);
    4674:       if (!fine) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_INCOMP,"DMRefine() did not perform any refinement, cannot continue grid sequencing");
    4675:       DMCreateInterpolation(snes->dm,fine,&interp,NULL);
    4676:       DMCreateGlobalVector(fine,&xnew);
    4677:       MatInterpolate(interp,x,xnew);
    4678:       DMInterpolate(snes->dm,interp,fine);
    4679:       MatDestroy(&interp);
    4680:       x    = xnew;

    4682:       SNESReset(snes);
    4683:       SNESSetDM(snes,fine);
    4684:       SNESResetFromOptions(snes);
    4685:       DMDestroy(&fine);
    4686:       PetscViewerASCIIPopTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)));
    4687:     }
    4688:   }
    4689:   SNESViewFromOptions(snes,NULL,"-snes_view");
    4690:   VecViewFromOptions(snes->vec_sol,(PetscObject)snes,"-snes_view_solution");
    4691:   DMMonitor(snes->dm);

    4693:   VecDestroy(&xcreated);
    4694:   PetscObjectSAWsBlock((PetscObject)snes);
    4695:   return(0);
    4696: }

    4698: /* --------- Internal routines for SNES Package --------- */

    4700: /*@C
    4701:    SNESSetType - Sets the method for the nonlinear solver.

    4703:    Collective on SNES

    4705:    Input Parameters:
    4706: +  snes - the SNES context
    4707: -  type - a known method

    4709:    Options Database Key:
    4710: .  -snes_type <type> - Sets the method; use -help for a list
    4711:    of available methods (for instance, newtonls or newtontr)

    4713:    Notes:
    4714:    See "petsc/include/petscsnes.h" for available methods (for instance)
    4715: +    SNESNEWTONLS - Newton's method with line search
    4716:      (systems of nonlinear equations)
    4717: -    SNESNEWTONTR - Newton's method with trust region
    4718:      (systems of nonlinear equations)

    4720:   Normally, it is best to use the SNESSetFromOptions() command and then
    4721:   set the SNES solver type from the options database rather than by using
    4722:   this routine.  Using the options database provides the user with
    4723:   maximum flexibility in evaluating the many nonlinear solvers.
    4724:   The SNESSetType() routine is provided for those situations where it
    4725:   is necessary to set the nonlinear solver independently of the command
    4726:   line or options database.  This might be the case, for example, when
    4727:   the choice of solver changes during the execution of the program,
    4728:   and the user's application is taking responsibility for choosing the
    4729:   appropriate method.

    4731:     Developer Notes:
    4732:     SNESRegister() adds a constructor for a new SNESType to SNESList, SNESSetType() locates
    4733:     the constructor in that list and calls it to create the spexific object.

    4735:   Level: intermediate

    4737: .seealso: SNESType, SNESCreate(), SNESDestroy(), SNESGetType(), SNESSetFromOptions()

    4739: @*/
    4740: PetscErrorCode  SNESSetType(SNES snes,SNESType type)
    4741: {
    4742:   PetscErrorCode ierr,(*r)(SNES);
    4743:   PetscBool      match;

    4749:   PetscObjectTypeCompare((PetscObject)snes,type,&match);
    4750:   if (match) return(0);

    4752:   PetscFunctionListFind(SNESList,type,&r);
    4753:   if (!r) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_UNKNOWN_TYPE,"Unable to find requested SNES type %s",type);
    4754:   /* Destroy the previous private SNES context */
    4755:   if (snes->ops->destroy) {
    4756:     (*(snes)->ops->destroy)(snes);
    4757:     snes->ops->destroy = NULL;
    4758:   }
    4759:   /* Reinitialize function pointers in SNESOps structure */
    4760:   snes->ops->setup          = NULL;
    4761:   snes->ops->solve          = NULL;
    4762:   snes->ops->view           = NULL;
    4763:   snes->ops->setfromoptions = NULL;
    4764:   snes->ops->destroy        = NULL;

    4766:   /* It may happen the user has customized the line search before calling SNESSetType */
    4767:   if (((PetscObject)snes)->type_name) {
    4768:     SNESLineSearchDestroy(&snes->linesearch);
    4769:   }

    4771:   /* Call the SNESCreate_XXX routine for this particular Nonlinear solver */
    4772:   snes->setupcalled = PETSC_FALSE;

    4774:   PetscObjectChangeTypeName((PetscObject)snes,type);
    4775:   (*r)(snes);
    4776:   return(0);
    4777: }

    4779: /*@C
    4780:    SNESGetType - Gets the SNES method type and name (as a string).

    4782:    Not Collective

    4784:    Input Parameter:
    4785: .  snes - nonlinear solver context

    4787:    Output Parameter:
    4788: .  type - SNES method (a character string)

    4790:    Level: intermediate

    4792: @*/
    4793: PetscErrorCode  SNESGetType(SNES snes,SNESType *type)
    4794: {
    4798:   *type = ((PetscObject)snes)->type_name;
    4799:   return(0);
    4800: }

    4802: /*@
    4803:   SNESSetSolution - Sets the solution vector for use by the SNES routines.

    4805:   Logically Collective on SNES

    4807:   Input Parameters:
    4808: + snes - the SNES context obtained from SNESCreate()
    4809: - u    - the solution vector

    4811:   Level: beginner

    4813: @*/
    4814: PetscErrorCode SNESSetSolution(SNES snes, Vec u)
    4815: {
    4816:   DM             dm;

    4822:   PetscObjectReference((PetscObject) u);
    4823:   VecDestroy(&snes->vec_sol);

    4825:   snes->vec_sol = u;

    4827:   SNESGetDM(snes, &dm);
    4828:   DMShellSetGlobalVector(dm, u);
    4829:   return(0);
    4830: }

    4832: /*@
    4833:    SNESGetSolution - Returns the vector where the approximate solution is
    4834:    stored. This is the fine grid solution when using SNESSetGridSequence().

    4836:    Not Collective, but Vec is parallel if SNES is parallel

    4838:    Input Parameter:
    4839: .  snes - the SNES context

    4841:    Output Parameter:
    4842: .  x - the solution

    4844:    Level: intermediate

    4846: .seealso:  SNESGetSolutionUpdate(), SNESGetFunction()
    4847: @*/
    4848: PetscErrorCode  SNESGetSolution(SNES snes,Vec *x)
    4849: {
    4853:   *x = snes->vec_sol;
    4854:   return(0);
    4855: }

    4857: /*@
    4858:    SNESGetSolutionUpdate - Returns the vector where the solution update is
    4859:    stored.

    4861:    Not Collective, but Vec is parallel if SNES is parallel

    4863:    Input Parameter:
    4864: .  snes - the SNES context

    4866:    Output Parameter:
    4867: .  x - the solution update

    4869:    Level: advanced

    4871: .seealso: SNESGetSolution(), SNESGetFunction()
    4872: @*/
    4873: PetscErrorCode  SNESGetSolutionUpdate(SNES snes,Vec *x)
    4874: {
    4878:   *x = snes->vec_sol_update;
    4879:   return(0);
    4880: }

    4882: /*@C
    4883:    SNESGetFunction - Returns the vector where the function is stored.

    4885:    Not Collective, but Vec is parallel if SNES is parallel. Collective if Vec is requested, but has not been created yet.

    4887:    Input Parameter:
    4888: .  snes - the SNES context

    4890:    Output Parameter:
    4891: +  r - the vector that is used to store residuals (or NULL if you don't want it)
    4892: .  f - the function (or NULL if you don't want it); see SNESFunction for calling sequence details
    4893: -  ctx - the function context (or NULL if you don't want it)

    4895:    Level: advanced

    4897:     Notes: The vector r DOES NOT, in general contain the current value of the SNES nonlinear function

    4899: .seealso: SNESSetFunction(), SNESGetSolution(), SNESFunction
    4900: @*/
    4901: PetscErrorCode  SNESGetFunction(SNES snes,Vec *r,PetscErrorCode (**f)(SNES,Vec,Vec,void*),void **ctx)
    4902: {
    4904:   DM             dm;

    4908:   if (r) {
    4909:     if (!snes->vec_func) {
    4910:       if (snes->vec_rhs) {
    4911:         VecDuplicate(snes->vec_rhs,&snes->vec_func);
    4912:       } else if (snes->vec_sol) {
    4913:         VecDuplicate(snes->vec_sol,&snes->vec_func);
    4914:       } else if (snes->dm) {
    4915:         DMCreateGlobalVector(snes->dm,&snes->vec_func);
    4916:       }
    4917:     }
    4918:     *r = snes->vec_func;
    4919:   }
    4920:   SNESGetDM(snes,&dm);
    4921:   DMSNESGetFunction(dm,f,ctx);
    4922:   return(0);
    4923: }

    4925: /*@C
    4926:    SNESGetNGS - Returns the NGS function and context.

    4928:    Input Parameter:
    4929: .  snes - the SNES context

    4931:    Output Parameter:
    4932: +  f - the function (or NULL) see SNESNGSFunction for details
    4933: -  ctx    - the function context (or NULL)

    4935:    Level: advanced

    4937: .seealso: SNESSetNGS(), SNESGetFunction()
    4938: @*/

    4940: PetscErrorCode SNESGetNGS (SNES snes, PetscErrorCode (**f)(SNES, Vec, Vec, void*), void ** ctx)
    4941: {
    4943:   DM             dm;

    4947:   SNESGetDM(snes,&dm);
    4948:   DMSNESGetNGS(dm,f,ctx);
    4949:   return(0);
    4950: }

    4952: /*@C
    4953:    SNESSetOptionsPrefix - Sets the prefix used for searching for all
    4954:    SNES options in the database.

    4956:    Logically Collective on SNES

    4958:    Input Parameter:
    4959: +  snes - the SNES context
    4960: -  prefix - the prefix to prepend to all option names

    4962:    Notes:
    4963:    A hyphen (-) must NOT be given at the beginning of the prefix name.
    4964:    The first character of all runtime options is AUTOMATICALLY the hyphen.

    4966:    Level: advanced

    4968: .seealso: SNESSetFromOptions()
    4969: @*/
    4970: PetscErrorCode  SNESSetOptionsPrefix(SNES snes,const char prefix[])
    4971: {

    4976:   PetscObjectSetOptionsPrefix((PetscObject)snes,prefix);
    4977:   if (!snes->ksp) {SNESGetKSP(snes,&snes->ksp);}
    4978:   if (snes->linesearch) {
    4979:     SNESGetLineSearch(snes,&snes->linesearch);
    4980:     PetscObjectSetOptionsPrefix((PetscObject)snes->linesearch,prefix);
    4981:   }
    4982:   KSPSetOptionsPrefix(snes->ksp,prefix);
    4983:   return(0);
    4984: }

    4986: /*@C
    4987:    SNESAppendOptionsPrefix - Appends to the prefix used for searching for all
    4988:    SNES options in the database.

    4990:    Logically Collective on SNES

    4992:    Input Parameters:
    4993: +  snes - the SNES context
    4994: -  prefix - the prefix to prepend to all option names

    4996:    Notes:
    4997:    A hyphen (-) must NOT be given at the beginning of the prefix name.
    4998:    The first character of all runtime options is AUTOMATICALLY the hyphen.

    5000:    Level: advanced

    5002: .seealso: SNESGetOptionsPrefix()
    5003: @*/
    5004: PetscErrorCode  SNESAppendOptionsPrefix(SNES snes,const char prefix[])
    5005: {

    5010:   PetscObjectAppendOptionsPrefix((PetscObject)snes,prefix);
    5011:   if (!snes->ksp) {SNESGetKSP(snes,&snes->ksp);}
    5012:   if (snes->linesearch) {
    5013:     SNESGetLineSearch(snes,&snes->linesearch);
    5014:     PetscObjectAppendOptionsPrefix((PetscObject)snes->linesearch,prefix);
    5015:   }
    5016:   KSPAppendOptionsPrefix(snes->ksp,prefix);
    5017:   return(0);
    5018: }

    5020: /*@C
    5021:    SNESGetOptionsPrefix - Sets the prefix used for searching for all
    5022:    SNES options in the database.

    5024:    Not Collective

    5026:    Input Parameter:
    5027: .  snes - the SNES context

    5029:    Output Parameter:
    5030: .  prefix - pointer to the prefix string used

    5032:    Notes:
    5033:     On the fortran side, the user should pass in a string 'prefix' of
    5034:    sufficient length to hold the prefix.

    5036:    Level: advanced

    5038: .seealso: SNESAppendOptionsPrefix()
    5039: @*/
    5040: PetscErrorCode  SNESGetOptionsPrefix(SNES snes,const char *prefix[])
    5041: {

    5046:   PetscObjectGetOptionsPrefix((PetscObject)snes,prefix);
    5047:   return(0);
    5048: }

    5051: /*@C
    5052:   SNESRegister - Adds a method to the nonlinear solver package.

    5054:    Not collective

    5056:    Input Parameters:
    5057: +  name_solver - name of a new user-defined solver
    5058: -  routine_create - routine to create method context

    5060:    Notes:
    5061:    SNESRegister() may be called multiple times to add several user-defined solvers.

    5063:    Sample usage:
    5064: .vb
    5065:    SNESRegister("my_solver",MySolverCreate);
    5066: .ve

    5068:    Then, your solver can be chosen with the procedural interface via
    5069: $     SNESSetType(snes,"my_solver")
    5070:    or at runtime via the option
    5071: $     -snes_type my_solver

    5073:    Level: advanced

    5075:     Note: If your function is not being put into a shared library then use SNESRegister() instead

    5077: .seealso: SNESRegisterAll(), SNESRegisterDestroy()

    5079:   Level: advanced
    5080: @*/
    5081: PetscErrorCode  SNESRegister(const char sname[],PetscErrorCode (*function)(SNES))
    5082: {

    5086:   SNESInitializePackage();
    5087:   PetscFunctionListAdd(&SNESList,sname,function);
    5088:   return(0);
    5089: }

    5091: PetscErrorCode  SNESTestLocalMin(SNES snes)
    5092: {
    5094:   PetscInt       N,i,j;
    5095:   Vec            u,uh,fh;
    5096:   PetscScalar    value;
    5097:   PetscReal      norm;

    5100:   SNESGetSolution(snes,&u);
    5101:   VecDuplicate(u,&uh);
    5102:   VecDuplicate(u,&fh);

    5104:   /* currently only works for sequential */
    5105:   PetscPrintf(PetscObjectComm((PetscObject)snes),"Testing FormFunction() for local min\n");
    5106:   VecGetSize(u,&N);
    5107:   for (i=0; i<N; i++) {
    5108:     VecCopy(u,uh);
    5109:     PetscPrintf(PetscObjectComm((PetscObject)snes),"i = %D\n",i);
    5110:     for (j=-10; j<11; j++) {
    5111:       value = PetscSign(j)*PetscExpReal(PetscAbs(j)-10.0);
    5112:       VecSetValue(uh,i,value,ADD_VALUES);
    5113:       SNESComputeFunction(snes,uh,fh);
    5114:       VecNorm(fh,NORM_2,&norm);
    5115:       PetscPrintf(PetscObjectComm((PetscObject)snes),"       j norm %D %18.16e\n",j,norm);
    5116:       value = -value;
    5117:       VecSetValue(uh,i,value,ADD_VALUES);
    5118:     }
    5119:   }
    5120:   VecDestroy(&uh);
    5121:   VecDestroy(&fh);
    5122:   return(0);
    5123: }

    5125: /*@
    5126:    SNESKSPSetUseEW - Sets SNES use Eisenstat-Walker method for
    5127:    computing relative tolerance for linear solvers within an inexact
    5128:    Newton method.

    5130:    Logically Collective on SNES

    5132:    Input Parameters:
    5133: +  snes - SNES context
    5134: -  flag - PETSC_TRUE or PETSC_FALSE

    5136:     Options Database:
    5137: +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
    5138: .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
    5139: .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
    5140: .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
    5141: .  -snes_ksp_ew_gamma <gamma> - Sets gamma
    5142: .  -snes_ksp_ew_alpha <alpha> - Sets alpha
    5143: .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
    5144: -  -snes_ksp_ew_threshold <threshold> - Sets threshold

    5146:    Notes:
    5147:    Currently, the default is to use a constant relative tolerance for
    5148:    the inner linear solvers.  Alternatively, one can use the
    5149:    Eisenstat-Walker method, where the relative convergence tolerance
    5150:    is reset at each Newton iteration according progress of the nonlinear
    5151:    solver.

    5153:    Level: advanced

    5155:    Reference:
    5156:    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
    5157:    inexact Newton method", SISC 17 (1), pp.16-32, 1996.

    5159: .seealso: SNESKSPGetUseEW(), SNESKSPGetParametersEW(), SNESKSPSetParametersEW()
    5160: @*/
    5161: PetscErrorCode  SNESKSPSetUseEW(SNES snes,PetscBool flag)
    5162: {
    5166:   snes->ksp_ewconv = flag;
    5167:   return(0);
    5168: }

    5170: /*@
    5171:    SNESKSPGetUseEW - Gets if SNES is using Eisenstat-Walker method
    5172:    for computing relative tolerance for linear solvers within an
    5173:    inexact Newton method.

    5175:    Not Collective

    5177:    Input Parameter:
    5178: .  snes - SNES context

    5180:    Output Parameter:
    5181: .  flag - PETSC_TRUE or PETSC_FALSE

    5183:    Notes:
    5184:    Currently, the default is to use a constant relative tolerance for
    5185:    the inner linear solvers.  Alternatively, one can use the
    5186:    Eisenstat-Walker method, where the relative convergence tolerance
    5187:    is reset at each Newton iteration according progress of the nonlinear
    5188:    solver.

    5190:    Level: advanced

    5192:    Reference:
    5193:    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
    5194:    inexact Newton method", SISC 17 (1), pp.16-32, 1996.

    5196: .seealso: SNESKSPSetUseEW(), SNESKSPGetParametersEW(), SNESKSPSetParametersEW()
    5197: @*/
    5198: PetscErrorCode  SNESKSPGetUseEW(SNES snes, PetscBool  *flag)
    5199: {
    5203:   *flag = snes->ksp_ewconv;
    5204:   return(0);
    5205: }

    5207: /*@
    5208:    SNESKSPSetParametersEW - Sets parameters for Eisenstat-Walker
    5209:    convergence criteria for the linear solvers within an inexact
    5210:    Newton method.

    5212:    Logically Collective on SNES

    5214:    Input Parameters:
    5215: +    snes - SNES context
    5216: .    version - version 1, 2 (default is 2) or 3
    5217: .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
    5218: .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
    5219: .    gamma - multiplicative factor for version 2 rtol computation
    5220:              (0 <= gamma2 <= 1)
    5221: .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
    5222: .    alpha2 - power for safeguard
    5223: -    threshold - threshold for imposing safeguard (0 < threshold < 1)

    5225:    Note:
    5226:    Version 3 was contributed by Luis Chacon, June 2006.

    5228:    Use PETSC_DEFAULT to retain the default for any of the parameters.

    5230:    Level: advanced

    5232:    Reference:
    5233:    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
    5234:    inexact Newton method", Utah State University Math. Stat. Dept. Res.
    5235:    Report 6/94/75, June, 1994, to appear in SIAM J. Sci. Comput.

    5237: .seealso: SNESKSPSetUseEW(), SNESKSPGetUseEW(), SNESKSPGetParametersEW()
    5238: @*/
    5239: PetscErrorCode  SNESKSPSetParametersEW(SNES snes,PetscInt version,PetscReal rtol_0,PetscReal rtol_max,PetscReal gamma,PetscReal alpha,PetscReal alpha2,PetscReal threshold)
    5240: {
    5241:   SNESKSPEW *kctx;

    5245:   kctx = (SNESKSPEW*)snes->kspconvctx;
    5246:   if (!kctx) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"No Eisenstat-Walker context existing");

    5255:   if (version != PETSC_DEFAULT)   kctx->version   = version;
    5256:   if (rtol_0 != PETSC_DEFAULT)    kctx->rtol_0    = rtol_0;
    5257:   if (rtol_max != PETSC_DEFAULT)  kctx->rtol_max  = rtol_max;
    5258:   if (gamma != PETSC_DEFAULT)     kctx->gamma     = gamma;
    5259:   if (alpha != PETSC_DEFAULT)     kctx->alpha     = alpha;
    5260:   if (alpha2 != PETSC_DEFAULT)    kctx->alpha2    = alpha2;
    5261:   if (threshold != PETSC_DEFAULT) kctx->threshold = threshold;

    5263:   if (kctx->version < 1 || kctx->version > 3) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Only versions 1, 2 and 3 are supported: %D",kctx->version);
    5264:   if (kctx->rtol_0 < 0.0 || kctx->rtol_0 >= 1.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"0.0 <= rtol_0 < 1.0: %g",(double)kctx->rtol_0);
    5265:   if (kctx->rtol_max < 0.0 || kctx->rtol_max >= 1.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"0.0 <= rtol_max (%g) < 1.0\n",(double)kctx->rtol_max);
    5266:   if (kctx->gamma < 0.0 || kctx->gamma > 1.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"0.0 <= gamma (%g) <= 1.0\n",(double)kctx->gamma);
    5267:   if (kctx->alpha <= 1.0 || kctx->alpha > 2.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"1.0 < alpha (%g) <= 2.0\n",(double)kctx->alpha);
    5268:   if (kctx->threshold <= 0.0 || kctx->threshold >= 1.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"0.0 < threshold (%g) < 1.0\n",(double)kctx->threshold);
    5269:   return(0);
    5270: }

    5272: /*@
    5273:    SNESKSPGetParametersEW - Gets parameters for Eisenstat-Walker
    5274:    convergence criteria for the linear solvers within an inexact
    5275:    Newton method.

    5277:    Not Collective

    5279:    Input Parameters:
    5280:      snes - SNES context

    5282:    Output Parameters:
    5283: +    version - version 1, 2 (default is 2) or 3
    5284: .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
    5285: .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
    5286: .    gamma - multiplicative factor for version 2 rtol computation (0 <= gamma2 <= 1)
    5287: .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
    5288: .    alpha2 - power for safeguard
    5289: -    threshold - threshold for imposing safeguard (0 < threshold < 1)

    5291:    Level: advanced

    5293: .seealso: SNESKSPSetUseEW(), SNESKSPGetUseEW(), SNESKSPSetParametersEW()
    5294: @*/
    5295: PetscErrorCode  SNESKSPGetParametersEW(SNES snes,PetscInt *version,PetscReal *rtol_0,PetscReal *rtol_max,PetscReal *gamma,PetscReal *alpha,PetscReal *alpha2,PetscReal *threshold)
    5296: {
    5297:   SNESKSPEW *kctx;

    5301:   kctx = (SNESKSPEW*)snes->kspconvctx;
    5302:   if (!kctx) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"No Eisenstat-Walker context existing");
    5303:   if (version)   *version   = kctx->version;
    5304:   if (rtol_0)    *rtol_0    = kctx->rtol_0;
    5305:   if (rtol_max)  *rtol_max  = kctx->rtol_max;
    5306:   if (gamma)     *gamma     = kctx->gamma;
    5307:   if (alpha)     *alpha     = kctx->alpha;
    5308:   if (alpha2)    *alpha2    = kctx->alpha2;
    5309:   if (threshold) *threshold = kctx->threshold;
    5310:   return(0);
    5311: }

    5313:  PetscErrorCode KSPPreSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
    5314: {
    5316:   SNESKSPEW      *kctx = (SNESKSPEW*)snes->kspconvctx;
    5317:   PetscReal      rtol  = PETSC_DEFAULT,stol;

    5320:   if (!snes->ksp_ewconv) return(0);
    5321:   if (!snes->iter) {
    5322:     rtol = kctx->rtol_0; /* first time in, so use the original user rtol */
    5323:     VecNorm(snes->vec_func,NORM_2,&kctx->norm_first);
    5324:   }
    5325:   else {
    5326:     if (kctx->version == 1) {
    5327:       rtol = (snes->norm - kctx->lresid_last)/kctx->norm_last;
    5328:       if (rtol < 0.0) rtol = -rtol;
    5329:       stol = PetscPowReal(kctx->rtol_last,kctx->alpha2);
    5330:       if (stol > kctx->threshold) rtol = PetscMax(rtol,stol);
    5331:     } else if (kctx->version == 2) {
    5332:       rtol = kctx->gamma * PetscPowReal(snes->norm/kctx->norm_last,kctx->alpha);
    5333:       stol = kctx->gamma * PetscPowReal(kctx->rtol_last,kctx->alpha);
    5334:       if (stol > kctx->threshold) rtol = PetscMax(rtol,stol);
    5335:     } else if (kctx->version == 3) { /* contributed by Luis Chacon, June 2006. */
    5336:       rtol = kctx->gamma * PetscPowReal(snes->norm/kctx->norm_last,kctx->alpha);
    5337:       /* safeguard: avoid sharp decrease of rtol */
    5338:       stol = kctx->gamma*PetscPowReal(kctx->rtol_last,kctx->alpha);
    5339:       stol = PetscMax(rtol,stol);
    5340:       rtol = PetscMin(kctx->rtol_0,stol);
    5341:       /* safeguard: avoid oversolving */
    5342:       stol = kctx->gamma*(kctx->norm_first*snes->rtol)/snes->norm;
    5343:       stol = PetscMax(rtol,stol);
    5344:       rtol = PetscMin(kctx->rtol_0,stol);
    5345:     } else SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Only versions 1, 2 or 3 are supported: %D",kctx->version);
    5346:   }
    5347:   /* safeguard: avoid rtol greater than one */
    5348:   rtol = PetscMin(rtol,kctx->rtol_max);
    5349:   KSPSetTolerances(ksp,rtol,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);
    5350:   PetscInfo3(snes,"iter %D, Eisenstat-Walker (version %D) KSP rtol=%g\n",snes->iter,kctx->version,(double)rtol);
    5351:   return(0);
    5352: }

    5354: PetscErrorCode KSPPostSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
    5355: {
    5357:   SNESKSPEW      *kctx = (SNESKSPEW*)snes->kspconvctx;
    5358:   PCSide         pcside;
    5359:   Vec            lres;

    5362:   if (!snes->ksp_ewconv) return(0);
    5363:   KSPGetTolerances(ksp,&kctx->rtol_last,NULL,NULL,NULL);
    5364:   kctx->norm_last = snes->norm;
    5365:   if (kctx->version == 1) {
    5366:     PC        pc;
    5367:     PetscBool isNone;

    5369:     KSPGetPC(ksp, &pc);
    5370:     PetscObjectTypeCompare((PetscObject) pc, PCNONE, &isNone);
    5371:     KSPGetPCSide(ksp,&pcside);
    5372:      if (pcside == PC_RIGHT || isNone) { /* XXX Should we also test KSP_UNPRECONDITIONED_NORM ? */
    5373:       /* KSP residual is true linear residual */
    5374:       KSPGetResidualNorm(ksp,&kctx->lresid_last);
    5375:     } else {
    5376:       /* KSP residual is preconditioned residual */
    5377:       /* compute true linear residual norm */
    5378:       VecDuplicate(b,&lres);
    5379:       MatMult(snes->jacobian,x,lres);
    5380:       VecAYPX(lres,-1.0,b);
    5381:       VecNorm(lres,NORM_2,&kctx->lresid_last);
    5382:       VecDestroy(&lres);
    5383:     }
    5384:   }
    5385:   return(0);
    5386: }

    5388: /*@
    5389:    SNESGetKSP - Returns the KSP context for a SNES solver.

    5391:    Not Collective, but if SNES object is parallel, then KSP object is parallel

    5393:    Input Parameter:
    5394: .  snes - the SNES context

    5396:    Output Parameter:
    5397: .  ksp - the KSP context

    5399:    Notes:
    5400:    The user can then directly manipulate the KSP context to set various
    5401:    options, etc.  Likewise, the user can then extract and manipulate the
    5402:    PC contexts as well.

    5404:    Level: beginner

    5406: .seealso: KSPGetPC(), SNESCreate(), KSPCreate(), SNESSetKSP()
    5407: @*/
    5408: PetscErrorCode  SNESGetKSP(SNES snes,KSP *ksp)
    5409: {

    5416:   if (!snes->ksp) {
    5417:     KSPCreate(PetscObjectComm((PetscObject)snes),&snes->ksp);
    5418:     PetscObjectIncrementTabLevel((PetscObject)snes->ksp,(PetscObject)snes,1);
    5419:     PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->ksp);

    5421:     KSPSetPreSolve(snes->ksp,(PetscErrorCode (*)(KSP,Vec,Vec,void*))KSPPreSolve_SNESEW,snes);
    5422:     KSPSetPostSolve(snes->ksp,(PetscErrorCode (*)(KSP,Vec,Vec,void*))KSPPostSolve_SNESEW,snes);

    5424:     KSPMonitorSetFromOptions(snes->ksp, "-snes_monitor_ksp", "snes_preconditioned_residual", snes);
    5425:     PetscObjectSetOptions((PetscObject)snes->ksp,((PetscObject)snes)->options);
    5426:   }
    5427:   *ksp = snes->ksp;
    5428:   return(0);
    5429: }

    5432: #include <petsc/private/dmimpl.h>
    5433: /*@
    5434:    SNESSetDM - Sets the DM that may be used by some nonlinear solvers or their underlying preconditioners

    5436:    Logically Collective on SNES

    5438:    Input Parameters:
    5439: +  snes - the nonlinear solver context
    5440: -  dm - the dm, cannot be NULL

    5442:    Notes:
    5443:    A DM can only be used for solving one problem at a time because information about the problem is stored on the DM,
    5444:    even when not using interfaces like DMSNESSetFunction().  Use DMClone() to get a distinct DM when solving different
    5445:    problems using the same function space.

    5447:    Level: intermediate

    5449: .seealso: SNESGetDM(), KSPSetDM(), KSPGetDM()
    5450: @*/
    5451: PetscErrorCode  SNESSetDM(SNES snes,DM dm)
    5452: {
    5454:   KSP            ksp;
    5455:   DMSNES         sdm;

    5460:   PetscObjectReference((PetscObject)dm);
    5461:   if (snes->dm) {               /* Move the DMSNES context over to the new DM unless the new DM already has one */
    5462:     if (snes->dm->dmsnes && !dm->dmsnes) {
    5463:       DMCopyDMSNES(snes->dm,dm);
    5464:       DMGetDMSNES(snes->dm,&sdm);
    5465:       if (sdm->originaldm == snes->dm) sdm->originaldm = dm; /* Grant write privileges to the replacement DM */
    5466:     }
    5467:     DMCoarsenHookRemove(snes->dm,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,snes);
    5468:     DMDestroy(&snes->dm);
    5469:   }
    5470:   snes->dm     = dm;
    5471:   snes->dmAuto = PETSC_FALSE;

    5473:   SNESGetKSP(snes,&ksp);
    5474:   KSPSetDM(ksp,dm);
    5475:   KSPSetDMActive(ksp,PETSC_FALSE);
    5476:   if (snes->npc) {
    5477:     SNESSetDM(snes->npc, snes->dm);
    5478:     SNESSetNPCSide(snes,snes->npcside);
    5479:   }
    5480:   return(0);
    5481: }

    5483: /*@
    5484:    SNESGetDM - Gets the DM that may be used by some preconditioners

    5486:    Not Collective but DM obtained is parallel on SNES

    5488:    Input Parameter:
    5489: . snes - the preconditioner context

    5491:    Output Parameter:
    5492: .  dm - the dm

    5494:    Level: intermediate

    5496: .seealso: SNESSetDM(), KSPSetDM(), KSPGetDM()
    5497: @*/
    5498: PetscErrorCode  SNESGetDM(SNES snes,DM *dm)
    5499: {

    5504:   if (!snes->dm) {
    5505:     DMShellCreate(PetscObjectComm((PetscObject)snes),&snes->dm);
    5506:     snes->dmAuto = PETSC_TRUE;
    5507:   }
    5508:   *dm = snes->dm;
    5509:   return(0);
    5510: }

    5512: /*@
    5513:   SNESSetNPC - Sets the nonlinear preconditioner to be used.

    5515:   Collective on SNES

    5517:   Input Parameters:
    5518: + snes - iterative context obtained from SNESCreate()
    5519: - pc   - the preconditioner object

    5521:   Notes:
    5522:   Use SNESGetNPC() to retrieve the preconditioner context (for example,
    5523:   to configure it using the API).

    5525:   Level: developer

    5527: .seealso: SNESGetNPC(), SNESHasNPC()
    5528: @*/
    5529: PetscErrorCode SNESSetNPC(SNES snes, SNES pc)
    5530: {

    5537:   PetscObjectReference((PetscObject) pc);
    5538:   SNESDestroy(&snes->npc);
    5539:   snes->npc = pc;
    5540:   PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->npc);
    5541:   return(0);
    5542: }

    5544: /*@
    5545:   SNESGetNPC - Creates a nonlinear preconditioning solver (SNES) to be used to precondition the nonlinear solver.

    5547:   Not Collective; but any changes to the obtained SNES object must be applied collectively

    5549:   Input Parameter:
    5550: . snes - iterative context obtained from SNESCreate()

    5552:   Output Parameter:
    5553: . pc - preconditioner context

    5555:   Options Database:
    5556: . -npc_snes_type <type> - set the type of the SNES to use as the nonlinear preconditioner

    5558:   Notes:
    5559:     If a SNES was previously set with SNESSetNPC() then that SNES is returned, otherwise a new SNES object is created.

    5561:     The (preconditioner) SNES returned automatically inherits the same nonlinear function and Jacobian supplied to the original
    5562:     SNES during SNESSetUp()

    5564:   Level: developer

    5566: .seealso: SNESSetNPC(), SNESHasNPC(), SNES, SNESCreate()
    5567: @*/
    5568: PetscErrorCode SNESGetNPC(SNES snes, SNES *pc)
    5569: {
    5571:   const char     *optionsprefix;

    5576:   if (!snes->npc) {
    5577:     SNESCreate(PetscObjectComm((PetscObject)snes),&snes->npc);
    5578:     PetscObjectIncrementTabLevel((PetscObject)snes->npc,(PetscObject)snes,1);
    5579:     PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->npc);
    5580:     SNESGetOptionsPrefix(snes,&optionsprefix);
    5581:     SNESSetOptionsPrefix(snes->npc,optionsprefix);
    5582:     SNESAppendOptionsPrefix(snes->npc,"npc_");
    5583:     SNESSetCountersReset(snes->npc,PETSC_FALSE);
    5584:   }
    5585:   *pc = snes->npc;
    5586:   return(0);
    5587: }

    5589: /*@
    5590:   SNESHasNPC - Returns whether a nonlinear preconditioner exists

    5592:   Not Collective

    5594:   Input Parameter:
    5595: . snes - iterative context obtained from SNESCreate()

    5597:   Output Parameter:
    5598: . has_npc - whether the SNES has an NPC or not

    5600:   Level: developer

    5602: .seealso: SNESSetNPC(), SNESGetNPC()
    5603: @*/
    5604: PetscErrorCode SNESHasNPC(SNES snes, PetscBool *has_npc)
    5605: {
    5608:   *has_npc = (PetscBool) (snes->npc ? PETSC_TRUE : PETSC_FALSE);
    5609:   return(0);
    5610: }

    5612: /*@
    5613:     SNESSetNPCSide - Sets the preconditioning side.

    5615:     Logically Collective on SNES

    5617:     Input Parameter:
    5618: .   snes - iterative context obtained from SNESCreate()

    5620:     Output Parameter:
    5621: .   side - the preconditioning side, where side is one of
    5622: .vb
    5623:       PC_LEFT - left preconditioning
    5624:       PC_RIGHT - right preconditioning (default for most nonlinear solvers)
    5625: .ve

    5627:     Options Database Keys:
    5628: .   -snes_pc_side <right,left>

    5630:     Notes:
    5631:     SNESNRICHARDSON and SNESNCG only support left preconditioning.

    5633:     Level: intermediate

    5635: .seealso: SNESGetNPCSide(), KSPSetPCSide()
    5636: @*/
    5637: PetscErrorCode  SNESSetNPCSide(SNES snes,PCSide side)
    5638: {
    5642:   snes->npcside= side;
    5643:   return(0);
    5644: }

    5646: /*@
    5647:     SNESGetNPCSide - Gets the preconditioning side.

    5649:     Not Collective

    5651:     Input Parameter:
    5652: .   snes - iterative context obtained from SNESCreate()

    5654:     Output Parameter:
    5655: .   side - the preconditioning side, where side is one of
    5656: .vb
    5657:       PC_LEFT - left preconditioning
    5658:       PC_RIGHT - right preconditioning (default for most nonlinear solvers)
    5659: .ve

    5661:     Level: intermediate

    5663: .seealso: SNESSetNPCSide(), KSPGetPCSide()
    5664: @*/
    5665: PetscErrorCode  SNESGetNPCSide(SNES snes,PCSide *side)
    5666: {
    5670:   *side = snes->npcside;
    5671:   return(0);
    5672: }

    5674: /*@
    5675:   SNESSetLineSearch - Sets the linesearch on the SNES instance.

    5677:   Collective on SNES

    5679:   Input Parameters:
    5680: + snes - iterative context obtained from SNESCreate()
    5681: - linesearch   - the linesearch object

    5683:   Notes:
    5684:   Use SNESGetLineSearch() to retrieve the preconditioner context (for example,
    5685:   to configure it using the API).

    5687:   Level: developer

    5689: .seealso: SNESGetLineSearch()
    5690: @*/
    5691: PetscErrorCode SNESSetLineSearch(SNES snes, SNESLineSearch linesearch)
    5692: {

    5699:   PetscObjectReference((PetscObject) linesearch);
    5700:   SNESLineSearchDestroy(&snes->linesearch);

    5702:   snes->linesearch = linesearch;

    5704:   PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->linesearch);
    5705:   return(0);
    5706: }

    5708: /*@
    5709:   SNESGetLineSearch - Returns a pointer to the line search context set with SNESSetLineSearch()
    5710:   or creates a default line search instance associated with the SNES and returns it.

    5712:   Not Collective

    5714:   Input Parameter:
    5715: . snes - iterative context obtained from SNESCreate()

    5717:   Output Parameter:
    5718: . linesearch - linesearch context

    5720:   Level: beginner

    5722: .seealso: SNESSetLineSearch(), SNESLineSearchCreate()
    5723: @*/
    5724: PetscErrorCode SNESGetLineSearch(SNES snes, SNESLineSearch *linesearch)
    5725: {
    5727:   const char     *optionsprefix;

    5732:   if (!snes->linesearch) {
    5733:     SNESGetOptionsPrefix(snes, &optionsprefix);
    5734:     SNESLineSearchCreate(PetscObjectComm((PetscObject)snes), &snes->linesearch);
    5735:     SNESLineSearchSetSNES(snes->linesearch, snes);
    5736:     SNESLineSearchAppendOptionsPrefix(snes->linesearch, optionsprefix);
    5737:     PetscObjectIncrementTabLevel((PetscObject) snes->linesearch, (PetscObject) snes, 1);
    5738:     PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->linesearch);
    5739:   }
    5740:   *linesearch = snes->linesearch;
    5741:   return(0);
    5742: }