Actual source code: fgmres.c

      2: /*
      3:     This file implements FGMRES (a Generalized Minimal Residual) method.
      4:     Reference:  Saad, 1993.

      6:     Preconditioning:  If the preconditioner is constant then this fgmres
      7:     code is equivalent to RIGHT-PRECONDITIONED GMRES.
      8:     FGMRES is a modification of gmres that allows the preconditioner to change
      9:     at each iteration.

     11:     Restarts:  Restarts are basically solves with x0 not equal to zero.

     13:        Contributed by Allison Baker

     15: */

     17: #include <../src/ksp/ksp/impls/gmres/fgmres/fgmresimpl.h>
     18: #define FGMRES_DELTA_DIRECTIONS 10
     19: #define FGMRES_DEFAULT_MAXK     30
     20: static PetscErrorCode KSPFGMRESGetNewVectors(KSP,PetscInt);
     21: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP,PetscInt,PetscBool,PetscReal*);
     22: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar*,Vec,Vec,KSP,PetscInt);

     24: /*

     26:     KSPSetUp_FGMRES - Sets up the workspace needed by fgmres.

     28:     This is called once, usually automatically by KSPSolve() or KSPSetUp(),
     29:     but can be called directly by KSPSetUp().

     31: */
     32: PetscErrorCode    KSPSetUp_FGMRES(KSP ksp)
     33: {
     35:   PetscInt       max_k,k;
     36:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)ksp->data;

     39:   max_k = fgmres->max_k;

     41:   KSPSetUp_GMRES(ksp);

     43:   PetscMalloc1(max_k+2,&fgmres->prevecs);
     44:   PetscMalloc1(max_k+2,&fgmres->prevecs_user_work);
     45:   PetscLogObjectMemory((PetscObject)ksp,(max_k+2)*(2*sizeof(void*)));

     47:   /* fgmres->vv_allocated includes extra work vectors, which are not used in the additional
     48:      block of vectors used to store the preconditioned directions, hence  the -VEC_OFFSET
     49:      term for this first allocation of vectors holding preconditioned directions */
     50:   KSPCreateVecs(ksp,fgmres->vv_allocated-VEC_OFFSET,&fgmres->prevecs_user_work[0],0,NULL);
     51:   PetscLogObjectParents(ksp,fgmres->vv_allocated-VEC_OFFSET,fgmres->prevecs_user_work[0]);
     52:   for (k=0; k < fgmres->vv_allocated - VEC_OFFSET ; k++) {
     53:     fgmres->prevecs[k] = fgmres->prevecs_user_work[0][k];
     54:   }
     55:   return(0);
     56: }

     58: /*
     59:     KSPFGMRESResidual - This routine computes the initial residual (NOT PRECONDITIONED)
     60: */
     61: static PetscErrorCode KSPFGMRESResidual(KSP ksp)
     62: {
     63:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)(ksp->data);
     64:   Mat            Amat,Pmat;

     68:   PCGetOperators(ksp->pc,&Amat,&Pmat);

     70:   /* put A*x into VEC_TEMP */
     71:   KSP_MatMult(ksp,Amat,ksp->vec_sol,VEC_TEMP);
     72:   /* now put residual (-A*x + f) into vec_vv(0) */
     73:   VecWAXPY(VEC_VV(0),-1.0,VEC_TEMP,ksp->vec_rhs);
     74:   return(0);
     75: }

     77: /*

     79:     KSPFGMRESCycle - Run fgmres, possibly with restart.  Return residual
     80:                   history if requested.

     82:     input parameters:
     83: .        fgmres  - structure containing parameters and work areas

     85:     output parameters:
     86: .        itcount - number of iterations used.  If null, ignored.
     87: .        converged - 0 if not converged

     90:     Notes:
     91:     On entry, the value in vector VEC_VV(0) should be
     92:     the initial residual.

     95:  */
     96: PetscErrorCode KSPFGMRESCycle(PetscInt *itcount,KSP ksp)
     97: {

     99:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)(ksp->data);
    100:   PetscReal      res_norm;
    101:   PetscReal      hapbnd,tt;
    102:   PetscBool      hapend = PETSC_FALSE;  /* indicates happy breakdown ending */
    104:   PetscInt       loc_it;                /* local count of # of dir. in Krylov space */
    105:   PetscInt       max_k = fgmres->max_k; /* max # of directions Krylov space */
    106:   Mat            Amat,Pmat;

    109:   /* Number of pseudo iterations since last restart is the number
    110:      of prestart directions */
    111:   loc_it = 0;

    113:   /* note: (fgmres->it) is always set one less than (loc_it) It is used in
    114:      KSPBUILDSolution_FGMRES, where it is passed to KSPFGMRESBuildSoln.
    115:      Note that when KSPFGMRESBuildSoln is called from this function,
    116:      (loc_it -1) is passed, so the two are equivalent */
    117:   fgmres->it = (loc_it - 1);

    119:   /* initial residual is in VEC_VV(0)  - compute its norm*/
    120:   VecNorm(VEC_VV(0),NORM_2,&res_norm);
    121:   KSPCheckNorm(ksp,res_norm);

    123:   /* first entry in right-hand-side of hessenberg system is just
    124:      the initial residual norm */
    125:   *RS(0) = res_norm;

    127:   ksp->rnorm = res_norm;
    128:   KSPLogResidualHistory(ksp,res_norm);
    129:   KSPMonitor(ksp,ksp->its,res_norm);

    131:   /* check for the convergence - maybe the current guess is good enough */
    132:   (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);
    133:   if (ksp->reason) {
    134:     if (itcount) *itcount = 0;
    135:     return(0);
    136:   }

    138:   /* scale VEC_VV (the initial residual) */
    139:   VecScale(VEC_VV(0),1.0/res_norm);

    141:   /* MAIN ITERATION LOOP BEGINNING*/
    142:   /* keep iterating until we have converged OR generated the max number
    143:      of directions OR reached the max number of iterations for the method */
    144:   while (!ksp->reason && loc_it < max_k && ksp->its < ksp->max_it) {
    145:     if (loc_it) {
    146:       KSPLogResidualHistory(ksp,res_norm);
    147:       KSPMonitor(ksp,ksp->its,res_norm);
    148:     }
    149:     fgmres->it = (loc_it - 1);

    151:     /* see if more space is needed for work vectors */
    152:     if (fgmres->vv_allocated <= loc_it + VEC_OFFSET + 1) {
    153:       KSPFGMRESGetNewVectors(ksp,loc_it+1);
    154:       /* (loc_it+1) is passed in as number of the first vector that should
    155:          be allocated */
    156:     }

    158:     /* CHANGE THE PRECONDITIONER? */
    159:     /* ModifyPC is the callback function that can be used to
    160:        change the PC or its attributes before its applied */
    161:     (*fgmres->modifypc)(ksp,ksp->its,loc_it,res_norm,fgmres->modifyctx);

    164:     /* apply PRECONDITIONER to direction vector and store with
    165:        preconditioned vectors in prevec */
    166:     KSP_PCApply(ksp,VEC_VV(loc_it),PREVEC(loc_it));

    168:     PCGetOperators(ksp->pc,&Amat,&Pmat);
    169:     /* Multiply preconditioned vector by operator - put in VEC_VV(loc_it+1) */
    170:     KSP_MatMult(ksp,Amat,PREVEC(loc_it),VEC_VV(1+loc_it));

    173:     /* update hessenberg matrix and do Gram-Schmidt - new direction is in
    174:        VEC_VV(1+loc_it)*/
    175:     (*fgmres->orthog)(ksp,loc_it);

    177:     /* new entry in hessenburg is the 2-norm of our new direction */
    178:     VecNorm(VEC_VV(loc_it+1),NORM_2,&tt);

    180:     *HH(loc_it+1,loc_it)  = tt;
    181:     *HES(loc_it+1,loc_it) = tt;

    183:     /* Happy Breakdown Check */
    184:     hapbnd = PetscAbsScalar((tt) / *RS(loc_it));
    185:     /* RS(loc_it) contains the res_norm from the last iteration  */
    186:     hapbnd = PetscMin(fgmres->haptol,hapbnd);
    187:     if (tt > hapbnd) {
    188:       /* scale new direction by its norm */
    189:       VecScale(VEC_VV(loc_it+1),1.0/tt);
    190:     } else {
    191:       /* This happens when the solution is exactly reached. */
    192:       /* So there is no new direction... */
    193:       VecSet(VEC_TEMP,0.0);     /* set VEC_TEMP to 0 */
    194:       hapend = PETSC_TRUE;
    195:     }
    196:     /* note that for FGMRES we could get HES(loc_it+1, loc_it)  = 0 and the
    197:        current solution would not be exact if HES was singular.  Note that
    198:        HH non-singular implies that HES is no singular, and HES is guaranteed
    199:        to be nonsingular when PREVECS are linearly independent and A is
    200:        nonsingular (in GMRES, the nonsingularity of A implies the nonsingularity
    201:        of HES). So we should really add a check to verify that HES is nonsingular.*/

    204:     /* Now apply rotations to new col of hessenberg (and right side of system),
    205:        calculate new rotation, and get new residual norm at the same time*/
    206:     KSPFGMRESUpdateHessenberg(ksp,loc_it,hapend,&res_norm);
    207:     if (ksp->reason) break;

    209:     loc_it++;
    210:     fgmres->it = (loc_it-1);   /* Add this here in case it has converged */

    212:     PetscObjectSAWsTakeAccess((PetscObject)ksp);
    213:     ksp->its++;
    214:     ksp->rnorm = res_norm;
    215:     PetscObjectSAWsGrantAccess((PetscObject)ksp);

    217:     (*ksp->converged)(ksp,ksp->its,res_norm,&ksp->reason,ksp->cnvP);

    219:     /* Catch error in happy breakdown and signal convergence and break from loop */
    220:     if (hapend) {
    221:       if (!ksp->reason) {
    222:         if (ksp->errorifnotconverged) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_NOT_CONVERGED,"You reached the happy break down, but convergence was not indicated. Residual norm = %g",(double)res_norm);
    223:         else {
    224:           ksp->reason = KSP_DIVERGED_BREAKDOWN;
    225:           break;
    226:         }
    227:       }
    228:     }
    229:   }
    230:   /* END OF ITERATION LOOP */
    231:   KSPLogResidualHistory(ksp,res_norm);

    233:   /*
    234:      Monitor if we know that we will not return for a restart */
    235:   if (loc_it && (ksp->reason || ksp->its >= ksp->max_it)) {
    236:     KSPMonitor(ksp,ksp->its,res_norm);
    237:   }

    239:   if (itcount) *itcount = loc_it;

    241:   /*
    242:     Down here we have to solve for the "best" coefficients of the Krylov
    243:     columns, add the solution values together, and possibly unwind the
    244:     preconditioning from the solution
    245:    */

    247:   /* Form the solution (or the solution so far) */
    248:   /* Note: must pass in (loc_it-1) for iteration count so that KSPFGMRESBuildSoln
    249:      properly navigates */

    251:   KSPFGMRESBuildSoln(RS(0),ksp->vec_sol,ksp->vec_sol,ksp,loc_it-1);
    252:   return(0);
    253: }

    255: /*
    256:     KSPSolve_FGMRES - This routine applies the FGMRES method.

    259:    Input Parameter:
    260: .     ksp - the Krylov space object that was set to use fgmres

    262:    Output Parameter:
    263: .     outits - number of iterations used

    265: */

    267: PetscErrorCode KSPSolve_FGMRES(KSP ksp)
    268: {
    270:   PetscInt       cycle_its = 0; /* iterations done in a call to KSPFGMRESCycle */
    271:   KSP_FGMRES     *fgmres   = (KSP_FGMRES*)ksp->data;
    272:   PetscBool      diagonalscale;

    275:   PCGetDiagonalScale(ksp->pc,&diagonalscale);
    276:   if (diagonalscale) SETERRQ1(PetscObjectComm((PetscObject)ksp),PETSC_ERR_SUP,"Krylov method %s does not support diagonal scaling",((PetscObject)ksp)->type_name);

    278:   PetscObjectSAWsTakeAccess((PetscObject)ksp);
    279:   ksp->its = 0;
    280:   PetscObjectSAWsGrantAccess((PetscObject)ksp);

    282:   /* Compute the initial (NOT preconditioned) residual */
    283:   if (!ksp->guess_zero) {
    284:     KSPFGMRESResidual(ksp);
    285:   } else { /* guess is 0 so residual is F (which is in ksp->vec_rhs) */
    286:     VecCopy(ksp->vec_rhs,VEC_VV(0));
    287:   }
    288:   /* now the residual is in VEC_VV(0) - which is what
    289:      KSPFGMRESCycle expects... */

    291:   KSPFGMRESCycle(&cycle_its,ksp);
    292:   while (!ksp->reason) {
    293:     KSPFGMRESResidual(ksp);
    294:     if (ksp->its >= ksp->max_it) break;
    295:     KSPFGMRESCycle(&cycle_its,ksp);
    296:   }
    297:   /* mark lack of convergence */
    298:   if (ksp->its >= ksp->max_it && !ksp->reason) ksp->reason = KSP_DIVERGED_ITS;
    299:   return(0);
    300: }

    302: extern PetscErrorCode KSPReset_FGMRES(KSP);
    303: /*

    305:    KSPDestroy_FGMRES - Frees all memory space used by the Krylov method.

    307: */
    308: PetscErrorCode KSPDestroy_FGMRES(KSP ksp)
    309: {

    313:   KSPReset_FGMRES(ksp);
    314:   PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",NULL);
    315:   KSPDestroy_GMRES(ksp);
    316:   return(0);
    317: }

    319: /*
    320:     KSPFGMRESBuildSoln - create the solution from the starting vector and the
    321:                       current iterates.

    323:     Input parameters:
    324:         nrs - work area of size it + 1.
    325:         vguess  - index of initial guess
    326:         vdest - index of result.  Note that vguess may == vdest (replace
    327:                 guess with the solution).
    328:         it - HH upper triangular part is a block of size (it+1) x (it+1)

    330:      This is an internal routine that knows about the FGMRES internals.
    331:  */
    332: static PetscErrorCode KSPFGMRESBuildSoln(PetscScalar *nrs,Vec vguess,Vec vdest,KSP ksp,PetscInt it)
    333: {
    334:   PetscScalar    tt;
    336:   PetscInt       ii,k,j;
    337:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)(ksp->data);

    340:   /* Solve for solution vector that minimizes the residual */

    342:   /* If it is < 0, no fgmres steps have been performed */
    343:   if (it < 0) {
    344:     VecCopy(vguess,vdest); /* VecCopy() is smart, exists immediately if vguess == vdest */
    345:     return(0);
    346:   }

    348:   /* so fgmres steps HAVE been performed */

    350:   /* solve the upper triangular system - RS is the right side and HH is
    351:      the upper triangular matrix  - put soln in nrs */
    352:   if (*HH(it,it) != 0.0) {
    353:     nrs[it] = *RS(it) / *HH(it,it);
    354:   } else {
    355:     nrs[it] = 0.0;
    356:   }
    357:   for (ii=1; ii<=it; ii++) {
    358:     k  = it - ii;
    359:     tt = *RS(k);
    360:     for (j=k+1; j<=it; j++) tt = tt - *HH(k,j) * nrs[j];
    361:     nrs[k] = tt / *HH(k,k);
    362:   }

    364:   /* Accumulate the correction to the soln of the preconditioned prob. in
    365:      VEC_TEMP - note that we use the preconditioned vectors  */
    366:   VecSet(VEC_TEMP,0.0); /* set VEC_TEMP components to 0 */
    367:   VecMAXPY(VEC_TEMP,it+1,nrs,&PREVEC(0));

    369:   /* put updated solution into vdest.*/
    370:   if (vdest != vguess) {
    371:     VecCopy(VEC_TEMP,vdest);
    372:     VecAXPY(vdest,1.0,vguess);
    373:   } else { /* replace guess with solution */
    374:     VecAXPY(vdest,1.0,VEC_TEMP);
    375:   }
    376:   return(0);
    377: }

    379: /*

    381:     KSPFGMRESUpdateHessenberg - Do the scalar work for the orthogonalization.
    382:                             Return new residual.

    384:     input parameters:

    386: .        ksp -    Krylov space object
    387: .        it  -    plane rotations are applied to the (it+1)th column of the
    388:                   modified hessenberg (i.e. HH(:,it))
    389: .        hapend - PETSC_FALSE not happy breakdown ending.

    391:     output parameters:
    392: .        res - the new residual

    394:  */
    395: static PetscErrorCode KSPFGMRESUpdateHessenberg(KSP ksp,PetscInt it,PetscBool hapend,PetscReal *res)
    396: {
    397:   PetscScalar *hh,*cc,*ss,tt;
    398:   PetscInt    j;
    399:   KSP_FGMRES  *fgmres = (KSP_FGMRES*)(ksp->data);

    402:   hh = HH(0,it);   /* pointer to beginning of column to update - so
    403:                       incrementing hh "steps down" the (it+1)th col of HH*/
    404:   cc = CC(0);      /* beginning of cosine rotations */
    405:   ss = SS(0);      /* beginning of sine rotations */

    407:   /* Apply all the previously computed plane rotations to the new column
    408:      of the Hessenberg matrix */
    409:   /* Note: this uses the rotation [conj(c)  s ; -s   c], c= cos(theta), s= sin(theta),
    410:      and some refs have [c   s ; -conj(s)  c] (don't be confused!) */

    412:   for (j=1; j<=it; j++) {
    413:     tt  = *hh;
    414:     *hh = PetscConj(*cc) * tt + *ss * *(hh+1);
    415:     hh++;
    416:     *hh = *cc++ * *hh - (*ss++ * tt);
    417:     /* hh, cc, and ss have all been incremented one by end of loop */
    418:   }

    420:   /*
    421:     compute the new plane rotation, and apply it to:
    422:      1) the right-hand-side of the Hessenberg system (RS)
    423:         note: it affects RS(it) and RS(it+1)
    424:      2) the new column of the Hessenberg matrix
    425:         note: it affects HH(it,it) which is currently pointed to
    426:         by hh and HH(it+1, it) (*(hh+1))
    427:     thus obtaining the updated value of the residual...
    428:   */

    430:   /* compute new plane rotation */

    432:   if (!hapend) {
    433:     tt = PetscSqrtScalar(PetscConj(*hh) * *hh + PetscConj(*(hh+1)) * *(hh+1));
    434:     if (tt == 0.0) {
    435:       ksp->reason = KSP_DIVERGED_NULL;
    436:       return(0);
    437:     }

    439:     *cc = *hh / tt;         /* new cosine value */
    440:     *ss = *(hh+1) / tt;        /* new sine value */

    442:     /* apply to 1) and 2) */
    443:     *RS(it+1) = -(*ss * *RS(it));
    444:     *RS(it)   = PetscConj(*cc) * *RS(it);
    445:     *hh       = PetscConj(*cc) * *hh + *ss * *(hh+1);

    447:     /* residual is the last element (it+1) of right-hand side! */
    448:     *res = PetscAbsScalar(*RS(it+1));

    450:   } else { /* happy breakdown: HH(it+1, it) = 0, therfore we don't need to apply
    451:             another rotation matrix (so RH doesn't change).  The new residual is
    452:             always the new sine term times the residual from last time (RS(it)),
    453:             but now the new sine rotation would be zero...so the residual should
    454:             be zero...so we will multiply "zero" by the last residual.  This might
    455:             not be exactly what we want to do here -could just return "zero". */

    457:     *res = 0.0;
    458:   }
    459:   return(0);
    460: }

    462: /*

    464:    KSPFGMRESGetNewVectors - This routine allocates more work vectors, starting from
    465:                          VEC_VV(it), and more preconditioned work vectors, starting
    466:                          from PREVEC(i).

    468: */
    469: static PetscErrorCode KSPFGMRESGetNewVectors(KSP ksp,PetscInt it)
    470: {
    471:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)ksp->data;
    472:   PetscInt       nwork   = fgmres->nwork_alloc; /* number of work vector chunks allocated */
    473:   PetscInt       nalloc;                      /* number to allocate */
    475:   PetscInt       k;

    478:   nalloc = fgmres->delta_allocate; /* number of vectors to allocate
    479:                                       in a single chunk */

    481:   /* Adjust the number to allocate to make sure that we don't exceed the
    482:      number of available slots (fgmres->vecs_allocated)*/
    483:   if (it + VEC_OFFSET + nalloc >= fgmres->vecs_allocated) {
    484:     nalloc = fgmres->vecs_allocated - it - VEC_OFFSET;
    485:   }
    486:   if (!nalloc) return(0);

    488:   fgmres->vv_allocated += nalloc; /* vv_allocated is the number of vectors allocated */

    490:   /* work vectors */
    491:   KSPCreateVecs(ksp,nalloc,&fgmres->user_work[nwork],0,NULL);
    492:   PetscLogObjectParents(ksp,nalloc,fgmres->user_work[nwork]);
    493:   for (k=0; k < nalloc; k++) {
    494:     fgmres->vecs[it+VEC_OFFSET+k] = fgmres->user_work[nwork][k];
    495:   }
    496:   /* specify size of chunk allocated */
    497:   fgmres->mwork_alloc[nwork] = nalloc;

    499:   /* preconditioned vectors */
    500:   KSPCreateVecs(ksp,nalloc,&fgmres->prevecs_user_work[nwork],0,NULL);
    501:   PetscLogObjectParents(ksp,nalloc,fgmres->prevecs_user_work[nwork]);
    502:   for (k=0; k < nalloc; k++) {
    503:     fgmres->prevecs[it+k] = fgmres->prevecs_user_work[nwork][k];
    504:   }

    506:   /* increment the number of work vector chunks */
    507:   fgmres->nwork_alloc++;
    508:   return(0);
    509: }

    511: /*

    513:    KSPBuildSolution_FGMRES

    515:      Input Parameter:
    516: .     ksp - the Krylov space object
    517: .     ptr-

    519:    Output Parameter:
    520: .     result - the solution

    522:    Note: this calls KSPFGMRESBuildSoln - the same function that KSPFGMRESCycle
    523:    calls directly.

    525: */
    526: PetscErrorCode KSPBuildSolution_FGMRES(KSP ksp,Vec ptr,Vec *result)
    527: {
    528:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)ksp->data;

    532:   if (!ptr) {
    533:     if (!fgmres->sol_temp) {
    534:       VecDuplicate(ksp->vec_sol,&fgmres->sol_temp);
    535:       PetscLogObjectParent((PetscObject)ksp,(PetscObject)fgmres->sol_temp);
    536:     }
    537:     ptr = fgmres->sol_temp;
    538:   }
    539:   if (!fgmres->nrs) {
    540:     /* allocate the work area */
    541:     PetscMalloc1(fgmres->max_k,&fgmres->nrs);
    542:     PetscLogObjectMemory((PetscObject)ksp,fgmres->max_k*sizeof(PetscScalar));
    543:   }

    545:   KSPFGMRESBuildSoln(fgmres->nrs,ksp->vec_sol,ptr,ksp,fgmres->it);
    546:   if (result) *result = ptr;
    547:   return(0);
    548: }

    550: PetscErrorCode KSPSetFromOptions_FGMRES(PetscOptionItems *PetscOptionsObject,KSP ksp)
    551: {
    553:   PetscBool      flg;

    556:   KSPSetFromOptions_GMRES(PetscOptionsObject,ksp);
    557:   PetscOptionsHead(PetscOptionsObject,"KSP flexible GMRES Options");
    558:   PetscOptionsBoolGroupBegin("-ksp_fgmres_modifypcnochange","do not vary the preconditioner","KSPFGMRESSetModifyPC",&flg);
    559:   if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCNoChange,NULL,NULL);}
    560:   PetscOptionsBoolGroupEnd("-ksp_fgmres_modifypcksp","vary the KSP based preconditioner","KSPFGMRESSetModifyPC",&flg);
    561:   if (flg) {KSPFGMRESSetModifyPC(ksp,KSPFGMRESModifyPCKSP,NULL,NULL);}
    562:   PetscOptionsTail();
    563:   return(0);
    564: }

    566: typedef PetscErrorCode (*FCN1)(KSP,PetscInt,PetscInt,PetscReal,void*); /* force argument to next function to not be extern C*/
    567: typedef PetscErrorCode (*FCN2)(void*);

    569: static PetscErrorCode  KSPFGMRESSetModifyPC_FGMRES(KSP ksp,FCN1 fcn,void *ctx,FCN2 d)
    570: {
    573:   ((KSP_FGMRES*)ksp->data)->modifypc      = fcn;
    574:   ((KSP_FGMRES*)ksp->data)->modifydestroy = d;
    575:   ((KSP_FGMRES*)ksp->data)->modifyctx     = ctx;
    576:   return(0);
    577: }

    580: PetscErrorCode KSPReset_FGMRES(KSP ksp)
    581: {
    582:   KSP_FGMRES     *fgmres = (KSP_FGMRES*)ksp->data;
    584:   PetscInt       i;

    587:   PetscFree (fgmres->prevecs);
    588:   if (fgmres->nwork_alloc>0){
    589:     i=0;
    590:     /* In the first allocation we allocated VEC_OFFSET fewer vectors in prevecs */
    591:     VecDestroyVecs(fgmres->mwork_alloc[i]-VEC_OFFSET,&fgmres->prevecs_user_work[i]);
    592:     for (i=1; i<fgmres->nwork_alloc; i++) {
    593:       VecDestroyVecs(fgmres->mwork_alloc[i],&fgmres->prevecs_user_work[i]);
    594:     }
    595:   }
    596:   PetscFree(fgmres->prevecs_user_work);
    597:   if (fgmres->modifydestroy) {
    598:     (*fgmres->modifydestroy)(fgmres->modifyctx);
    599:   }
    600:   KSPReset_GMRES(ksp);
    601:   return(0);
    602: }

    604: PetscErrorCode  KSPGMRESSetRestart_FGMRES(KSP ksp,PetscInt max_k)
    605: {
    606:   KSP_FGMRES     *gmres = (KSP_FGMRES*)ksp->data;

    610:   if (max_k < 1) SETERRQ(PetscObjectComm((PetscObject)ksp),PETSC_ERR_ARG_OUTOFRANGE,"Restart must be positive");
    611:   if (!ksp->setupstage) {
    612:     gmres->max_k = max_k;
    613:   } else if (gmres->max_k != max_k) {
    614:     gmres->max_k    = max_k;
    615:     ksp->setupstage = KSP_SETUP_NEW;
    616:     /* free the data structures, then create them again */
    617:     KSPReset_FGMRES(ksp);
    618:   }
    619:   return(0);
    620: }

    622: PetscErrorCode  KSPGMRESGetRestart_FGMRES(KSP ksp,PetscInt *max_k)
    623: {
    624:   KSP_FGMRES *gmres = (KSP_FGMRES*)ksp->data;

    627:   *max_k = gmres->max_k;
    628:   return(0);
    629: }

    631: /*MC
    632:      KSPFGMRES - Implements the Flexible Generalized Minimal Residual method.
    633:                 developed by Saad with restart

    636:    Options Database Keys:
    637: +   -ksp_gmres_restart <restart> - the number of Krylov directions to orthogonalize against
    638: .   -ksp_gmres_haptol <tol> - sets the tolerance for "happy ending" (exact convergence)
    639: .   -ksp_gmres_preallocate - preallocate all the Krylov search directions initially (otherwise groups of
    640:                              vectors are allocated as needed)
    641: .   -ksp_gmres_classicalgramschmidt - use classical (unmodified) Gram-Schmidt to orthogonalize against the Krylov space (fast) (the default)
    642: .   -ksp_gmres_modifiedgramschmidt - use modified Gram-Schmidt in the orthogonalization (more stable, but slower)
    643: .   -ksp_gmres_cgs_refinement_type <refine_never,refine_ifneeded,refine_always> - determine if iterative refinement is used to increase the
    644:                                    stability of the classical Gram-Schmidt  orthogonalization.
    645: .   -ksp_gmres_krylov_monitor - plot the Krylov space generated
    646: .   -ksp_fgmres_modifypcnochange - do not change the preconditioner between iterations
    647: -   -ksp_fgmres_modifypcksp - modify the preconditioner using KSPFGMRESModifyPCKSP()

    649:    Level: beginner

    651:     Notes:
    652:     See KSPFGMRESSetModifyPC() for how to vary the preconditioner between iterations
    653:            Only right preconditioning is supported.

    655:     Notes:
    656:     The following options -ksp_type fgmres -pc_type ksp -ksp_ksp_type bcgs -ksp_view -ksp_pc_type jacobi make the preconditioner (or inner solver)
    657:            be bi-CG-stab with a preconditioner of Jacobi.

    659:     Developer Notes:
    660:     This object is subclassed off of KSPGMRES

    662: .seealso:  KSPCreate(), KSPSetType(), KSPType (for list of available types), KSP, KSPGMRES, KSPLGMRES,
    663:            KSPGMRESSetRestart(), KSPGMRESSetHapTol(), KSPGMRESSetPreAllocateVectors(), KSPGMRESSetOrthogonalization(), KSPGMRESGetOrthogonalization(),
    664:            KSPGMRESClassicalGramSchmidtOrthogonalization(), KSPGMRESModifiedGramSchmidtOrthogonalization(),
    665:            KSPGMRESCGSRefinementType, KSPGMRESSetCGSRefinementType(),  KSPGMRESGetCGSRefinementType(), KSPGMRESMonitorKrylov(), KSPFGMRESSetModifyPC(),
    666:            KSPFGMRESModifyPCKSP()

    668: M*/

    670: PETSC_EXTERN PetscErrorCode KSPCreate_FGMRES(KSP ksp)
    671: {
    672:   KSP_FGMRES     *fgmres;

    676:   PetscNewLog(ksp,&fgmres);

    678:   ksp->data                              = (void*)fgmres;
    679:   ksp->ops->buildsolution                = KSPBuildSolution_FGMRES;
    680:   ksp->ops->setup                        = KSPSetUp_FGMRES;
    681:   ksp->ops->solve                        = KSPSolve_FGMRES;
    682:   ksp->ops->reset                        = KSPReset_FGMRES;
    683:   ksp->ops->destroy                      = KSPDestroy_FGMRES;
    684:   ksp->ops->view                         = KSPView_GMRES;
    685:   ksp->ops->setfromoptions               = KSPSetFromOptions_FGMRES;
    686:   ksp->ops->computeextremesingularvalues = KSPComputeExtremeSingularValues_GMRES;
    687:   ksp->ops->computeeigenvalues           = KSPComputeEigenvalues_GMRES;

    689:   KSPSetSupportedNorm(ksp,KSP_NORM_UNPRECONDITIONED,PC_RIGHT,3);
    690:   KSPSetSupportedNorm(ksp,KSP_NORM_NONE,PC_RIGHT,1);

    692:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetPreAllocateVectors_C",KSPGMRESSetPreAllocateVectors_GMRES);
    693:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetOrthogonalization_C",KSPGMRESSetOrthogonalization_GMRES);
    694:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetOrthogonalization_C",KSPGMRESGetOrthogonalization_GMRES);
    695:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetRestart_C",KSPGMRESSetRestart_FGMRES);
    696:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetRestart_C",KSPGMRESGetRestart_FGMRES);
    697:   PetscObjectComposeFunction((PetscObject)ksp,"KSPFGMRESSetModifyPC_C",KSPFGMRESSetModifyPC_FGMRES);
    698:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESSetCGSRefinementType_C",KSPGMRESSetCGSRefinementType_GMRES);
    699:   PetscObjectComposeFunction((PetscObject)ksp,"KSPGMRESGetCGSRefinementType_C",KSPGMRESGetCGSRefinementType_GMRES);

    702:   fgmres->haptol         = 1.0e-30;
    703:   fgmres->q_preallocate  = 0;
    704:   fgmres->delta_allocate = FGMRES_DELTA_DIRECTIONS;
    705:   fgmres->orthog         = KSPGMRESClassicalGramSchmidtOrthogonalization;
    706:   fgmres->nrs            = NULL;
    707:   fgmres->sol_temp       = NULL;
    708:   fgmres->max_k          = FGMRES_DEFAULT_MAXK;
    709:   fgmres->Rsvd           = NULL;
    710:   fgmres->orthogwork     = NULL;
    711:   fgmres->modifypc       = KSPFGMRESModifyPCNoChange;
    712:   fgmres->modifyctx      = NULL;
    713:   fgmres->modifydestroy  = NULL;
    714:   fgmres->cgstype        = KSP_GMRES_CGS_REFINE_NEVER;
    715:   return(0);
    716: }