Actual source code: bjacobi.c

      1: /*
      2:    Defines a block Jacobi preconditioner.
      3: */

      5: #include <../src/ksp/pc/impls/bjacobi/bjacobi.h>

      7: static PetscErrorCode PCSetUp_BJacobi_Singleblock(PC, Mat, Mat);
      8: static PetscErrorCode PCSetUp_BJacobi_Multiblock(PC, Mat, Mat);
      9: static PetscErrorCode PCSetUp_BJacobi_Multiproc(PC);

     11: static PetscErrorCode PCSetUp_BJacobi(PC pc)
     12: {
     13:   PC_BJacobi *jac = (PC_BJacobi *)pc->data;
     14:   Mat         mat = pc->mat, pmat = pc->pmat;
     15:   PetscBool   hasop;
     16:   PetscInt    N, M, start, i, sum, end;
     17:   PetscInt    bs, i_start = -1, i_end = -1;
     18:   PetscMPIInt rank, size;

     20:   PetscFunctionBegin;
     21:   PetscCallMPI(MPI_Comm_rank(PetscObjectComm((PetscObject)pc), &rank));
     22:   PetscCallMPI(MPI_Comm_size(PetscObjectComm((PetscObject)pc), &size));
     23:   PetscCall(MatGetLocalSize(pc->pmat, &M, &N));
     24:   PetscCall(MatGetBlockSize(pc->pmat, &bs));

     26:   if (jac->n > 0 && jac->n < size) {
     27:     PetscCall(PCSetUp_BJacobi_Multiproc(pc));
     28:     PetscFunctionReturn(PETSC_SUCCESS);
     29:   }

     31:   /*    Determines the number of blocks assigned to each processor */
     32:   /*   local block count  given */
     33:   if (jac->n_local > 0 && jac->n < 0) {
     34:     PetscCallMPI(MPIU_Allreduce(&jac->n_local, &jac->n, 1, MPIU_INT, MPI_SUM, PetscObjectComm((PetscObject)pc)));
     35:     if (jac->l_lens) { /* check that user set these correctly */
     36:       sum = 0;
     37:       for (i = 0; i < jac->n_local; i++) {
     38:         PetscCheck(jac->l_lens[i] / bs * bs == jac->l_lens[i], PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Mat blocksize doesn't match block Jacobi layout");
     39:         sum += jac->l_lens[i];
     40:       }
     41:       PetscCheck(sum == M, PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Local lens set incorrectly");
     42:     } else {
     43:       PetscCall(PetscMalloc1(jac->n_local, &jac->l_lens));
     44:       for (i = 0; i < jac->n_local; i++) jac->l_lens[i] = bs * ((M / bs) / jac->n_local + (((M / bs) % jac->n_local) > i));
     45:     }
     46:   } else if (jac->n > 0 && jac->n_local < 0) { /* global block count given */
     47:     /* global blocks given: determine which ones are local */
     48:     if (jac->g_lens) {
     49:       /* check if the g_lens is has valid entries */
     50:       for (i = 0; i < jac->n; i++) {
     51:         PetscCheck(jac->g_lens[i], PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Zero block not allowed");
     52:         PetscCheck(jac->g_lens[i] / bs * bs == jac->g_lens[i], PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Mat blocksize doesn't match block Jacobi layout");
     53:       }
     54:       if (size == 1) {
     55:         jac->n_local = jac->n;
     56:         PetscCall(PetscMalloc1(jac->n_local, &jac->l_lens));
     57:         PetscCall(PetscArraycpy(jac->l_lens, jac->g_lens, jac->n_local));
     58:         /* check that user set these correctly */
     59:         sum = 0;
     60:         for (i = 0; i < jac->n_local; i++) sum += jac->l_lens[i];
     61:         PetscCheck(sum == M, PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Global lens set incorrectly");
     62:       } else {
     63:         PetscCall(MatGetOwnershipRange(pc->pmat, &start, &end));
     64:         /* loop over blocks determining first one owned by me */
     65:         sum = 0;
     66:         for (i = 0; i < jac->n + 1; i++) {
     67:           if (sum == start) {
     68:             i_start = i;
     69:             goto start_1;
     70:           }
     71:           if (i < jac->n) sum += jac->g_lens[i];
     72:         }
     73:         SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Block sizes used in PCBJacobiSetTotalBlocks()\nare not compatible with parallel matrix layout");
     74:       start_1:
     75:         for (i = i_start; i < jac->n + 1; i++) {
     76:           if (sum == end) {
     77:             i_end = i;
     78:             goto end_1;
     79:           }
     80:           if (i < jac->n) sum += jac->g_lens[i];
     81:         }
     82:         SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Block sizes used in PCBJacobiSetTotalBlocks()\nare not compatible with parallel matrix layout");
     83:       end_1:
     84:         jac->n_local = i_end - i_start;
     85:         PetscCall(PetscMalloc1(jac->n_local, &jac->l_lens));
     86:         PetscCall(PetscArraycpy(jac->l_lens, jac->g_lens + i_start, jac->n_local));
     87:       }
     88:     } else { /* no global blocks given, determine then using default layout */
     89:       jac->n_local = jac->n / size + ((jac->n % size) > rank);
     90:       PetscCall(PetscMalloc1(jac->n_local, &jac->l_lens));
     91:       for (i = 0; i < jac->n_local; i++) {
     92:         jac->l_lens[i] = ((M / bs) / jac->n_local + (((M / bs) % jac->n_local) > i)) * bs;
     93:         PetscCheck(jac->l_lens[i], PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Too many blocks given");
     94:       }
     95:     }
     96:   } else if (jac->n < 0 && jac->n_local < 0) { /* no blocks given */
     97:     jac->n       = size;
     98:     jac->n_local = 1;
     99:     PetscCall(PetscMalloc1(1, &jac->l_lens));
    100:     jac->l_lens[0] = M;
    101:   } else { /* jac->n > 0 && jac->n_local > 0 */
    102:     if (!jac->l_lens) {
    103:       PetscCall(PetscMalloc1(jac->n_local, &jac->l_lens));
    104:       for (i = 0; i < jac->n_local; i++) jac->l_lens[i] = bs * ((M / bs) / jac->n_local + (((M / bs) % jac->n_local) > i));
    105:     }
    106:   }
    107:   PetscCheck(jac->n_local >= 1, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Number of blocks is less than number of processors");

    109:   /*    Determines mat and pmat */
    110:   PetscCall(MatHasOperation(pc->mat, MATOP_GET_DIAGONAL_BLOCK, &hasop));
    111:   if (!hasop && size == 1) {
    112:     mat  = pc->mat;
    113:     pmat = pc->pmat;
    114:   } else {
    115:     if (pc->useAmat) {
    116:       /* use block from Amat matrix, not Pmat for local MatMult() */
    117:       PetscCall(MatGetDiagonalBlock(pc->mat, &mat));
    118:     }
    119:     if (pc->pmat != pc->mat || !pc->useAmat) {
    120:       PetscCall(MatGetDiagonalBlock(pc->pmat, &pmat));
    121:     } else pmat = mat;
    122:   }

    124:   /*
    125:      Setup code depends on the number of blocks
    126:   */
    127:   if (jac->n_local == 1) {
    128:     PetscCall(PCSetUp_BJacobi_Singleblock(pc, mat, pmat));
    129:   } else {
    130:     PetscCall(PCSetUp_BJacobi_Multiblock(pc, mat, pmat));
    131:   }
    132:   PetscFunctionReturn(PETSC_SUCCESS);
    133: }

    135: /* Default destroy, if it has never been setup */
    136: static PetscErrorCode PCDestroy_BJacobi(PC pc)
    137: {
    138:   PC_BJacobi *jac = (PC_BJacobi *)pc->data;

    140:   PetscFunctionBegin;
    141:   PetscCall(PetscFree(jac->g_lens));
    142:   PetscCall(PetscFree(jac->l_lens));
    143:   PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCBJacobiGetSubKSP_C", NULL));
    144:   PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCBJacobiSetTotalBlocks_C", NULL));
    145:   PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCBJacobiGetTotalBlocks_C", NULL));
    146:   PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCBJacobiSetLocalBlocks_C", NULL));
    147:   PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCBJacobiGetLocalBlocks_C", NULL));
    148:   PetscCall(PetscFree(pc->data));
    149:   PetscFunctionReturn(PETSC_SUCCESS);
    150: }

    152: static PetscErrorCode PCSetFromOptions_BJacobi(PC pc, PetscOptionItems *PetscOptionsObject)
    153: {
    154:   PC_BJacobi *jac = (PC_BJacobi *)pc->data;
    155:   PetscInt    blocks, i;
    156:   PetscBool   flg;

    158:   PetscFunctionBegin;
    159:   PetscOptionsHeadBegin(PetscOptionsObject, "Block Jacobi options");
    160:   PetscCall(PetscOptionsInt("-pc_bjacobi_blocks", "Total number of blocks", "PCBJacobiSetTotalBlocks", jac->n, &blocks, &flg));
    161:   if (flg) PetscCall(PCBJacobiSetTotalBlocks(pc, blocks, NULL));
    162:   PetscCall(PetscOptionsInt("-pc_bjacobi_local_blocks", "Local number of blocks", "PCBJacobiSetLocalBlocks", jac->n_local, &blocks, &flg));
    163:   if (flg) PetscCall(PCBJacobiSetLocalBlocks(pc, blocks, NULL));
    164:   if (jac->ksp) {
    165:     /* The sub-KSP has already been set up (e.g., PCSetUp_BJacobi_Singleblock), but KSPSetFromOptions was not called
    166:      * unless we had already been called. */
    167:     for (i = 0; i < jac->n_local; i++) PetscCall(KSPSetFromOptions(jac->ksp[i]));
    168:   }
    169:   PetscOptionsHeadEnd();
    170:   PetscFunctionReturn(PETSC_SUCCESS);
    171: }

    173: #include <petscdraw.h>
    174: static PetscErrorCode PCView_BJacobi(PC pc, PetscViewer viewer)
    175: {
    176:   PC_BJacobi           *jac   = (PC_BJacobi *)pc->data;
    177:   PC_BJacobi_Multiproc *mpjac = (PC_BJacobi_Multiproc *)jac->data;
    178:   PetscMPIInt           rank;
    179:   PetscInt              i;
    180:   PetscBool             iascii, isstring, isdraw;
    181:   PetscViewer           sviewer;
    182:   PetscViewerFormat     format;
    183:   const char           *prefix;

    185:   PetscFunctionBegin;
    186:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
    187:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSTRING, &isstring));
    188:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERDRAW, &isdraw));
    189:   if (iascii) {
    190:     if (pc->useAmat) PetscCall(PetscViewerASCIIPrintf(viewer, "  using Amat local matrix, number of blocks = %" PetscInt_FMT "\n", jac->n));
    191:     PetscCall(PetscViewerASCIIPrintf(viewer, "  number of blocks = %" PetscInt_FMT "\n", jac->n));
    192:     PetscCallMPI(MPI_Comm_rank(PetscObjectComm((PetscObject)pc), &rank));
    193:     PetscCall(PetscViewerGetFormat(viewer, &format));
    194:     if (format != PETSC_VIEWER_ASCII_INFO_DETAIL) {
    195:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Local solver information for first block is in the following KSP and PC objects on rank 0:\n"));
    196:       PetscCall(PCGetOptionsPrefix(pc, &prefix));
    197:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Use -%sksp_view ::ascii_info_detail to display information for all blocks\n", prefix ? prefix : ""));
    198:       if (jac->ksp && !jac->psubcomm) {
    199:         PetscCall(PetscViewerGetSubViewer(viewer, PETSC_COMM_SELF, &sviewer));
    200:         if (rank == 0) {
    201:           PetscCall(PetscViewerASCIIPushTab(sviewer));
    202:           PetscCall(KSPView(jac->ksp[0], sviewer));
    203:           PetscCall(PetscViewerASCIIPopTab(sviewer));
    204:         }
    205:         PetscCall(PetscViewerRestoreSubViewer(viewer, PETSC_COMM_SELF, &sviewer));
    206:         /*  extra call needed because of the two calls to PetscViewerASCIIPushSynchronized() in PetscViewerGetSubViewer() */
    207:         PetscCall(PetscViewerASCIIPopSynchronized(viewer));
    208:       } else if (mpjac && jac->ksp && mpjac->psubcomm) {
    209:         PetscCall(PetscViewerGetSubViewer(viewer, mpjac->psubcomm->child, &sviewer));
    210:         if (!mpjac->psubcomm->color) {
    211:           PetscCall(PetscViewerASCIIPushTab(sviewer));
    212:           PetscCall(KSPView(*jac->ksp, sviewer));
    213:           PetscCall(PetscViewerASCIIPopTab(sviewer));
    214:         }
    215:         PetscCall(PetscViewerRestoreSubViewer(viewer, mpjac->psubcomm->child, &sviewer));
    216:         /*  extra call needed because of the two calls to PetscViewerASCIIPushSynchronized() in PetscViewerGetSubViewer() */
    217:         PetscCall(PetscViewerASCIIPopSynchronized(viewer));
    218:       }
    219:     } else {
    220:       PetscInt n_global;
    221:       PetscCallMPI(MPIU_Allreduce(&jac->n_local, &n_global, 1, MPIU_INT, MPI_MAX, PetscObjectComm((PetscObject)pc)));
    222:       PetscCall(PetscViewerASCIIPushSynchronized(viewer));
    223:       PetscCall(PetscViewerASCIIPrintf(viewer, "  Local solver information for each block is in the following KSP and PC objects:\n"));
    224:       PetscCall(PetscViewerASCIIPushTab(viewer));
    225:       PetscCall(PetscViewerGetSubViewer(viewer, PETSC_COMM_SELF, &sviewer));
    226:       PetscCall(PetscViewerASCIIPrintf(sviewer, "[%d] number of local blocks = %" PetscInt_FMT ", first local block number = %" PetscInt_FMT "\n", rank, jac->n_local, jac->first_local));
    227:       for (i = 0; i < jac->n_local; i++) {
    228:         PetscCall(PetscViewerASCIIPrintf(sviewer, "[%d] local block number %" PetscInt_FMT "\n", rank, i));
    229:         PetscCall(KSPView(jac->ksp[i], sviewer));
    230:         PetscCall(PetscViewerASCIIPrintf(sviewer, "- - - - - - - - - - - - - - - - - -\n"));
    231:       }
    232:       PetscCall(PetscViewerRestoreSubViewer(viewer, PETSC_COMM_SELF, &sviewer));
    233:       PetscCall(PetscViewerASCIIPopTab(viewer));
    234:       PetscCall(PetscViewerASCIIPopSynchronized(viewer));
    235:     }
    236:   } else if (isstring) {
    237:     PetscCall(PetscViewerStringSPrintf(viewer, " blks=%" PetscInt_FMT, jac->n));
    238:     PetscCall(PetscViewerGetSubViewer(viewer, PETSC_COMM_SELF, &sviewer));
    239:     if (jac->ksp) PetscCall(KSPView(jac->ksp[0], sviewer));
    240:     PetscCall(PetscViewerRestoreSubViewer(viewer, PETSC_COMM_SELF, &sviewer));
    241:   } else if (isdraw) {
    242:     PetscDraw draw;
    243:     char      str[25];
    244:     PetscReal x, y, bottom, h;

    246:     PetscCall(PetscViewerDrawGetDraw(viewer, 0, &draw));
    247:     PetscCall(PetscDrawGetCurrentPoint(draw, &x, &y));
    248:     PetscCall(PetscSNPrintf(str, 25, "Number blocks %" PetscInt_FMT, jac->n));
    249:     PetscCall(PetscDrawStringBoxed(draw, x, y, PETSC_DRAW_RED, PETSC_DRAW_BLACK, str, NULL, &h));
    250:     bottom = y - h;
    251:     PetscCall(PetscDrawPushCurrentPoint(draw, x, bottom));
    252:     /* warning the communicator on viewer is different then on ksp in parallel */
    253:     if (jac->ksp) PetscCall(KSPView(jac->ksp[0], viewer));
    254:     PetscCall(PetscDrawPopCurrentPoint(draw));
    255:   }
    256:   PetscFunctionReturn(PETSC_SUCCESS);
    257: }

    259: static PetscErrorCode PCBJacobiGetSubKSP_BJacobi(PC pc, PetscInt *n_local, PetscInt *first_local, KSP **ksp)
    260: {
    261:   PC_BJacobi *jac = (PC_BJacobi *)pc->data;

    263:   PetscFunctionBegin;
    264:   PetscCheck(pc->setupcalled, PetscObjectComm((PetscObject)pc), PETSC_ERR_ARG_WRONGSTATE, "Must call KSPSetUp() or PCSetUp() first");

    266:   if (n_local) *n_local = jac->n_local;
    267:   if (first_local) *first_local = jac->first_local;
    268:   if (ksp) *ksp = jac->ksp;
    269:   PetscFunctionReturn(PETSC_SUCCESS);
    270: }

    272: static PetscErrorCode PCBJacobiSetTotalBlocks_BJacobi(PC pc, PetscInt blocks, const PetscInt *lens)
    273: {
    274:   PC_BJacobi *jac = (PC_BJacobi *)pc->data;

    276:   PetscFunctionBegin;
    277:   PetscCheck(pc->setupcalled <= 0 || jac->n == blocks, PetscObjectComm((PetscObject)pc), PETSC_ERR_ORDER, "Cannot alter number of blocks after PCSetUp()/KSPSetUp() has been called");
    278:   jac->n = blocks;
    279:   if (!lens) jac->g_lens = NULL;
    280:   else {
    281:     PetscCall(PetscMalloc1(blocks, &jac->g_lens));
    282:     PetscCall(PetscArraycpy(jac->g_lens, lens, blocks));
    283:   }
    284:   PetscFunctionReturn(PETSC_SUCCESS);
    285: }

    287: static PetscErrorCode PCBJacobiGetTotalBlocks_BJacobi(PC pc, PetscInt *blocks, const PetscInt *lens[])
    288: {
    289:   PC_BJacobi *jac = (PC_BJacobi *)pc->data;

    291:   PetscFunctionBegin;
    292:   *blocks = jac->n;
    293:   if (lens) *lens = jac->g_lens;
    294:   PetscFunctionReturn(PETSC_SUCCESS);
    295: }

    297: static PetscErrorCode PCBJacobiSetLocalBlocks_BJacobi(PC pc, PetscInt blocks, const PetscInt lens[])
    298: {
    299:   PC_BJacobi *jac;

    301:   PetscFunctionBegin;
    302:   jac = (PC_BJacobi *)pc->data;

    304:   jac->n_local = blocks;
    305:   if (!lens) jac->l_lens = NULL;
    306:   else {
    307:     PetscCall(PetscMalloc1(blocks, &jac->l_lens));
    308:     PetscCall(PetscArraycpy(jac->l_lens, lens, blocks));
    309:   }
    310:   PetscFunctionReturn(PETSC_SUCCESS);
    311: }

    313: static PetscErrorCode PCBJacobiGetLocalBlocks_BJacobi(PC pc, PetscInt *blocks, const PetscInt *lens[])
    314: {
    315:   PC_BJacobi *jac = (PC_BJacobi *)pc->data;

    317:   PetscFunctionBegin;
    318:   *blocks = jac->n_local;
    319:   if (lens) *lens = jac->l_lens;
    320:   PetscFunctionReturn(PETSC_SUCCESS);
    321: }

    323: /*@C
    324:   PCBJacobiGetSubKSP - Gets the local `KSP` contexts for all blocks on
    325:   this processor.

    327:   Not Collective

    329:   Input Parameter:
    330: . pc - the preconditioner context

    332:   Output Parameters:
    333: + n_local     - the number of blocks on this processor, or NULL
    334: . first_local - the global number of the first block on this processor, or NULL
    335: - ksp         - the array of KSP contexts

    337:   Notes:
    338:   After `PCBJacobiGetSubKSP()` the array of `KSP` contexts is not to be freed.

    340:   Currently for some matrix implementations only 1 block per processor
    341:   is supported.

    343:   You must call `KSPSetUp()` or `PCSetUp()` before calling `PCBJacobiGetSubKSP()`.

    345:   Fortran Notes:
    346:   You must pass in a `KSP` array that is large enough to contain all the local `KSP`s.

    348:   You can call `PCBJacobiGetSubKSP`(pc,nlocal,firstlocal,`PETSC_NULL_KSP`,ierr) to determine how large the
    349:   `KSP` array must be.

    351:   Level: advanced

    353: .seealso: [](ch_ksp), `PCBJACOBI`, `PCASM`, `PCASMGetSubKSP()`
    354: @*/
    355: PetscErrorCode PCBJacobiGetSubKSP(PC pc, PetscInt *n_local, PetscInt *first_local, KSP *ksp[])
    356: {
    357:   PetscFunctionBegin;
    359:   PetscUseMethod(pc, "PCBJacobiGetSubKSP_C", (PC, PetscInt *, PetscInt *, KSP **), (pc, n_local, first_local, ksp));
    360:   PetscFunctionReturn(PETSC_SUCCESS);
    361: }

    363: /*@
    364:   PCBJacobiSetTotalBlocks - Sets the global number of blocks for the block
    365:   Jacobi preconditioner.

    367:   Collective

    369:   Input Parameters:
    370: + pc     - the preconditioner context
    371: . blocks - the number of blocks
    372: - lens   - [optional] integer array containing the size of each block

    374:   Options Database Key:
    375: . -pc_bjacobi_blocks <blocks> - Sets the number of global blocks

    377:   Note:
    378:   Currently only a limited number of blocking configurations are supported.
    379:   All processors sharing the `PC` must call this routine with the same data.

    381:   Level: intermediate

    383: .seealso: [](ch_ksp), `PCBJACOBI`, `PCSetUseAmat()`, `PCBJacobiSetLocalBlocks()`
    384: @*/
    385: PetscErrorCode PCBJacobiSetTotalBlocks(PC pc, PetscInt blocks, const PetscInt lens[])
    386: {
    387:   PetscFunctionBegin;
    389:   PetscCheck(blocks > 0, PetscObjectComm((PetscObject)pc), PETSC_ERR_ARG_OUTOFRANGE, "Must have positive blocks");
    390:   PetscTryMethod(pc, "PCBJacobiSetTotalBlocks_C", (PC, PetscInt, const PetscInt[]), (pc, blocks, lens));
    391:   PetscFunctionReturn(PETSC_SUCCESS);
    392: }

    394: /*@C
    395:   PCBJacobiGetTotalBlocks - Gets the global number of blocks for the block
    396:   Jacobi, `PCBJACOBI`, preconditioner.

    398:   Not Collective

    400:   Input Parameter:
    401: . pc - the preconditioner context

    403:   Output Parameters:
    404: + blocks - the number of blocks
    405: - lens   - integer array containing the size of each block

    407:   Level: intermediate

    409: .seealso: [](ch_ksp), `PCBJACOBI`, `PCSetUseAmat()`, `PCBJacobiGetLocalBlocks()`
    410: @*/
    411: PetscErrorCode PCBJacobiGetTotalBlocks(PC pc, PetscInt *blocks, const PetscInt *lens[])
    412: {
    413:   PetscFunctionBegin;
    415:   PetscAssertPointer(blocks, 2);
    416:   PetscUseMethod(pc, "PCBJacobiGetTotalBlocks_C", (PC, PetscInt *, const PetscInt *[]), (pc, blocks, lens));
    417:   PetscFunctionReturn(PETSC_SUCCESS);
    418: }

    420: /*@
    421:   PCBJacobiSetLocalBlocks - Sets the local number of blocks for the block
    422:   Jacobi, `PCBJACOBI`,  preconditioner.

    424:   Not Collective

    426:   Input Parameters:
    427: + pc     - the preconditioner context
    428: . blocks - the number of blocks
    429: - lens   - [optional] integer array containing size of each block

    431:   Options Database Key:
    432: . -pc_bjacobi_local_blocks <blocks> - Sets the number of local blocks

    434:   Note:
    435:   Currently only a limited number of blocking configurations are supported.

    437:   Level: intermediate

    439: .seealso: [](ch_ksp), `PCBJACOBI`, `PCSetUseAmat()`, `PCBJacobiSetTotalBlocks()`
    440: @*/
    441: PetscErrorCode PCBJacobiSetLocalBlocks(PC pc, PetscInt blocks, const PetscInt lens[])
    442: {
    443:   PetscFunctionBegin;
    445:   PetscCheck(blocks >= 0, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Must have nonegative blocks");
    446:   PetscTryMethod(pc, "PCBJacobiSetLocalBlocks_C", (PC, PetscInt, const PetscInt[]), (pc, blocks, lens));
    447:   PetscFunctionReturn(PETSC_SUCCESS);
    448: }

    450: /*@C
    451:   PCBJacobiGetLocalBlocks - Gets the local number of blocks for the block
    452:   Jacobi, `PCBJACOBI`, preconditioner.

    454:   Not Collective

    456:   Input Parameters:
    457: + pc     - the preconditioner context
    458: . blocks - the number of blocks
    459: - lens   - [optional] integer array containing size of each block

    461:   Note:
    462:   Currently only a limited number of blocking configurations are supported.

    464:   Level: intermediate

    466: .seealso: [](ch_ksp), `PCBJACOBI`, `PCSetUseAmat()`, `PCBJacobiGetTotalBlocks()`
    467: @*/
    468: PetscErrorCode PCBJacobiGetLocalBlocks(PC pc, PetscInt *blocks, const PetscInt *lens[])
    469: {
    470:   PetscFunctionBegin;
    472:   PetscAssertPointer(blocks, 2);
    473:   PetscUseMethod(pc, "PCBJacobiGetLocalBlocks_C", (PC, PetscInt *, const PetscInt *[]), (pc, blocks, lens));
    474:   PetscFunctionReturn(PETSC_SUCCESS);
    475: }

    477: /*MC
    478:    PCBJACOBI - Use block Jacobi preconditioning, each block is (approximately) solved with
    479:            its own `KSP` object.

    481:    Options Database Keys:
    482: +  -pc_use_amat - use Amat to apply block of operator in inner Krylov method
    483: -  -pc_bjacobi_blocks <n> - use n total blocks

    485:    Notes:
    486:     See `PCJACOBI` for diagonal Jacobi, `PCVPBJACOBI` for variable point block, and `PCPBJACOBI` for fixed size point block

    488:     Each processor can have one or more blocks, or a single block can be shared by several processes. Defaults to one block per processor.

    490:      To set options on the solvers for each block append -sub_ to all the `KSP` and `PC`
    491:         options database keys. For example, -sub_pc_type ilu -sub_pc_factor_levels 1 -sub_ksp_type preonly

    493:      To set the options on the solvers separate for each block call `PCBJacobiGetSubKSP()`
    494:          and set the options directly on the resulting `KSP` object (you can access its `PC`
    495:          `KSPGetPC()`)

    497:      For GPU-based vectors (`VECCUDA`, `VECViennaCL`) it is recommended to use exactly one block per MPI process for best
    498:          performance.  Different block partitioning may lead to additional data transfers
    499:          between host and GPU that lead to degraded performance.

    501:      When multiple processes share a single block, each block encompasses exactly all the unknowns owned its set of processes.

    503:    Level: beginner

    505: .seealso: [](ch_ksp), `PCCreate()`, `PCSetType()`, `PCType`, `PC`, `PCType`,
    506:           `PCASM`, `PCSetUseAmat()`, `PCGetUseAmat()`, `PCBJacobiGetSubKSP()`, `PCBJacobiSetTotalBlocks()`,
    507:           `PCBJacobiSetLocalBlocks()`, `PCSetModifySubMatrices()`, `PCJACOBI`, `PCVPBJACOBI`, `PCPBJACOBI`
    508: M*/

    510: PETSC_EXTERN PetscErrorCode PCCreate_BJacobi(PC pc)
    511: {
    512:   PetscMPIInt rank;
    513:   PC_BJacobi *jac;

    515:   PetscFunctionBegin;
    516:   PetscCall(PetscNew(&jac));
    517:   PetscCallMPI(MPI_Comm_rank(PetscObjectComm((PetscObject)pc), &rank));

    519:   pc->ops->apply           = NULL;
    520:   pc->ops->matapply        = NULL;
    521:   pc->ops->applytranspose  = NULL;
    522:   pc->ops->setup           = PCSetUp_BJacobi;
    523:   pc->ops->destroy         = PCDestroy_BJacobi;
    524:   pc->ops->setfromoptions  = PCSetFromOptions_BJacobi;
    525:   pc->ops->view            = PCView_BJacobi;
    526:   pc->ops->applyrichardson = NULL;

    528:   pc->data         = (void *)jac;
    529:   jac->n           = -1;
    530:   jac->n_local     = -1;
    531:   jac->first_local = rank;
    532:   jac->ksp         = NULL;
    533:   jac->g_lens      = NULL;
    534:   jac->l_lens      = NULL;
    535:   jac->psubcomm    = NULL;

    537:   PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCBJacobiGetSubKSP_C", PCBJacobiGetSubKSP_BJacobi));
    538:   PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCBJacobiSetTotalBlocks_C", PCBJacobiSetTotalBlocks_BJacobi));
    539:   PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCBJacobiGetTotalBlocks_C", PCBJacobiGetTotalBlocks_BJacobi));
    540:   PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCBJacobiSetLocalBlocks_C", PCBJacobiSetLocalBlocks_BJacobi));
    541:   PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCBJacobiGetLocalBlocks_C", PCBJacobiGetLocalBlocks_BJacobi));
    542:   PetscFunctionReturn(PETSC_SUCCESS);
    543: }

    545: /*
    546:         These are for a single block per processor; works for AIJ, BAIJ; Seq and MPI
    547: */
    548: static PetscErrorCode PCReset_BJacobi_Singleblock(PC pc)
    549: {
    550:   PC_BJacobi             *jac  = (PC_BJacobi *)pc->data;
    551:   PC_BJacobi_Singleblock *bjac = (PC_BJacobi_Singleblock *)jac->data;

    553:   PetscFunctionBegin;
    554:   PetscCall(KSPReset(jac->ksp[0]));
    555:   PetscCall(VecDestroy(&bjac->x));
    556:   PetscCall(VecDestroy(&bjac->y));
    557:   PetscFunctionReturn(PETSC_SUCCESS);
    558: }

    560: static PetscErrorCode PCDestroy_BJacobi_Singleblock(PC pc)
    561: {
    562:   PC_BJacobi             *jac  = (PC_BJacobi *)pc->data;
    563:   PC_BJacobi_Singleblock *bjac = (PC_BJacobi_Singleblock *)jac->data;

    565:   PetscFunctionBegin;
    566:   PetscCall(PCReset_BJacobi_Singleblock(pc));
    567:   PetscCall(KSPDestroy(&jac->ksp[0]));
    568:   PetscCall(PetscFree(jac->ksp));
    569:   PetscCall(PetscFree(bjac));
    570:   PetscCall(PCDestroy_BJacobi(pc));
    571:   PetscFunctionReturn(PETSC_SUCCESS);
    572: }

    574: static PetscErrorCode PCSetUpOnBlocks_BJacobi_Singleblock(PC pc)
    575: {
    576:   PC_BJacobi        *jac    = (PC_BJacobi *)pc->data;
    577:   KSP                subksp = jac->ksp[0];
    578:   KSPConvergedReason reason;

    580:   PetscFunctionBegin;
    581:   PetscCall(KSPSetUp(subksp));
    582:   PetscCall(KSPGetConvergedReason(subksp, &reason));
    583:   if (reason == KSP_DIVERGED_PC_FAILED) pc->failedreason = PC_SUBPC_ERROR;
    584:   PetscFunctionReturn(PETSC_SUCCESS);
    585: }

    587: static PetscErrorCode PCApply_BJacobi_Singleblock(PC pc, Vec x, Vec y)
    588: {
    589:   PC_BJacobi             *jac  = (PC_BJacobi *)pc->data;
    590:   PC_BJacobi_Singleblock *bjac = (PC_BJacobi_Singleblock *)jac->data;

    592:   PetscFunctionBegin;
    593:   PetscCall(VecGetLocalVectorRead(x, bjac->x));
    594:   PetscCall(VecGetLocalVector(y, bjac->y));
    595:   /* Since the inner KSP matrix may point directly to the diagonal block of an MPI matrix the inner
    596:      matrix may change even if the outer KSP/PC has not updated the preconditioner, this will trigger a rebuild
    597:      of the inner preconditioner automatically unless we pass down the outer preconditioners reuse flag.*/
    598:   PetscCall(KSPSetReusePreconditioner(jac->ksp[0], pc->reusepreconditioner));
    599:   PetscCall(KSPSolve(jac->ksp[0], bjac->x, bjac->y));
    600:   PetscCall(KSPCheckSolve(jac->ksp[0], pc, bjac->y));
    601:   PetscCall(VecRestoreLocalVectorRead(x, bjac->x));
    602:   PetscCall(VecRestoreLocalVector(y, bjac->y));
    603:   PetscFunctionReturn(PETSC_SUCCESS);
    604: }

    606: static PetscErrorCode PCMatApply_BJacobi_Singleblock(PC pc, Mat X, Mat Y)
    607: {
    608:   PC_BJacobi *jac = (PC_BJacobi *)pc->data;
    609:   Mat         sX, sY;

    611:   PetscFunctionBegin;
    612:   /* Since the inner KSP matrix may point directly to the diagonal block of an MPI matrix the inner
    613:      matrix may change even if the outer KSP/PC has not updated the preconditioner, this will trigger a rebuild
    614:      of the inner preconditioner automatically unless we pass down the outer preconditioners reuse flag.*/
    615:   PetscCall(KSPSetReusePreconditioner(jac->ksp[0], pc->reusepreconditioner));
    616:   PetscCall(MatDenseGetLocalMatrix(X, &sX));
    617:   PetscCall(MatDenseGetLocalMatrix(Y, &sY));
    618:   PetscCall(KSPMatSolve(jac->ksp[0], sX, sY));
    619:   PetscFunctionReturn(PETSC_SUCCESS);
    620: }

    622: static PetscErrorCode PCApplySymmetricLeft_BJacobi_Singleblock(PC pc, Vec x, Vec y)
    623: {
    624:   PC_BJacobi             *jac  = (PC_BJacobi *)pc->data;
    625:   PC_BJacobi_Singleblock *bjac = (PC_BJacobi_Singleblock *)jac->data;
    626:   PetscScalar            *y_array;
    627:   const PetscScalar      *x_array;
    628:   PC                      subpc;

    630:   PetscFunctionBegin;
    631:   /*
    632:       The VecPlaceArray() is to avoid having to copy the
    633:     y vector into the bjac->x vector. The reason for
    634:     the bjac->x vector is that we need a sequential vector
    635:     for the sequential solve.
    636:   */
    637:   PetscCall(VecGetArrayRead(x, &x_array));
    638:   PetscCall(VecGetArray(y, &y_array));
    639:   PetscCall(VecPlaceArray(bjac->x, x_array));
    640:   PetscCall(VecPlaceArray(bjac->y, y_array));
    641:   /* apply the symmetric left portion of the inner PC operator */
    642:   /* note this bypasses the inner KSP and its options completely */
    643:   PetscCall(KSPGetPC(jac->ksp[0], &subpc));
    644:   PetscCall(PCApplySymmetricLeft(subpc, bjac->x, bjac->y));
    645:   PetscCall(VecResetArray(bjac->x));
    646:   PetscCall(VecResetArray(bjac->y));
    647:   PetscCall(VecRestoreArrayRead(x, &x_array));
    648:   PetscCall(VecRestoreArray(y, &y_array));
    649:   PetscFunctionReturn(PETSC_SUCCESS);
    650: }

    652: static PetscErrorCode PCApplySymmetricRight_BJacobi_Singleblock(PC pc, Vec x, Vec y)
    653: {
    654:   PC_BJacobi             *jac  = (PC_BJacobi *)pc->data;
    655:   PC_BJacobi_Singleblock *bjac = (PC_BJacobi_Singleblock *)jac->data;
    656:   PetscScalar            *y_array;
    657:   const PetscScalar      *x_array;
    658:   PC                      subpc;

    660:   PetscFunctionBegin;
    661:   /*
    662:       The VecPlaceArray() is to avoid having to copy the
    663:     y vector into the bjac->x vector. The reason for
    664:     the bjac->x vector is that we need a sequential vector
    665:     for the sequential solve.
    666:   */
    667:   PetscCall(VecGetArrayRead(x, &x_array));
    668:   PetscCall(VecGetArray(y, &y_array));
    669:   PetscCall(VecPlaceArray(bjac->x, x_array));
    670:   PetscCall(VecPlaceArray(bjac->y, y_array));

    672:   /* apply the symmetric right portion of the inner PC operator */
    673:   /* note this bypasses the inner KSP and its options completely */

    675:   PetscCall(KSPGetPC(jac->ksp[0], &subpc));
    676:   PetscCall(PCApplySymmetricRight(subpc, bjac->x, bjac->y));

    678:   PetscCall(VecResetArray(bjac->x));
    679:   PetscCall(VecResetArray(bjac->y));
    680:   PetscCall(VecRestoreArrayRead(x, &x_array));
    681:   PetscCall(VecRestoreArray(y, &y_array));
    682:   PetscFunctionReturn(PETSC_SUCCESS);
    683: }

    685: static PetscErrorCode PCApplyTranspose_BJacobi_Singleblock(PC pc, Vec x, Vec y)
    686: {
    687:   PC_BJacobi             *jac  = (PC_BJacobi *)pc->data;
    688:   PC_BJacobi_Singleblock *bjac = (PC_BJacobi_Singleblock *)jac->data;
    689:   PetscScalar            *y_array;
    690:   const PetscScalar      *x_array;

    692:   PetscFunctionBegin;
    693:   /*
    694:       The VecPlaceArray() is to avoid having to copy the
    695:     y vector into the bjac->x vector. The reason for
    696:     the bjac->x vector is that we need a sequential vector
    697:     for the sequential solve.
    698:   */
    699:   PetscCall(VecGetArrayRead(x, &x_array));
    700:   PetscCall(VecGetArray(y, &y_array));
    701:   PetscCall(VecPlaceArray(bjac->x, x_array));
    702:   PetscCall(VecPlaceArray(bjac->y, y_array));
    703:   PetscCall(KSPSolveTranspose(jac->ksp[0], bjac->x, bjac->y));
    704:   PetscCall(KSPCheckSolve(jac->ksp[0], pc, bjac->y));
    705:   PetscCall(VecResetArray(bjac->x));
    706:   PetscCall(VecResetArray(bjac->y));
    707:   PetscCall(VecRestoreArrayRead(x, &x_array));
    708:   PetscCall(VecRestoreArray(y, &y_array));
    709:   PetscFunctionReturn(PETSC_SUCCESS);
    710: }

    712: static PetscErrorCode PCSetUp_BJacobi_Singleblock(PC pc, Mat mat, Mat pmat)
    713: {
    714:   PC_BJacobi             *jac = (PC_BJacobi *)pc->data;
    715:   PetscInt                m;
    716:   KSP                     ksp;
    717:   PC_BJacobi_Singleblock *bjac;
    718:   PetscBool               wasSetup = PETSC_TRUE;
    719:   VecType                 vectype;
    720:   const char             *prefix;

    722:   PetscFunctionBegin;
    723:   if (!pc->setupcalled) {
    724:     if (!jac->ksp) {
    725:       PetscInt nestlevel;

    727:       wasSetup = PETSC_FALSE;

    729:       PetscCall(KSPCreate(PETSC_COMM_SELF, &ksp));
    730:       PetscCall(PCGetKSPNestLevel(pc, &nestlevel));
    731:       PetscCall(KSPSetNestLevel(ksp, nestlevel + 1));
    732:       PetscCall(KSPSetErrorIfNotConverged(ksp, pc->erroriffailure));
    733:       PetscCall(PetscObjectIncrementTabLevel((PetscObject)ksp, (PetscObject)pc, 1));
    734:       PetscCall(KSPSetType(ksp, KSPPREONLY));
    735:       PetscCall(PCGetOptionsPrefix(pc, &prefix));
    736:       PetscCall(KSPSetOptionsPrefix(ksp, prefix));
    737:       PetscCall(KSPAppendOptionsPrefix(ksp, "sub_"));

    739:       pc->ops->reset               = PCReset_BJacobi_Singleblock;
    740:       pc->ops->destroy             = PCDestroy_BJacobi_Singleblock;
    741:       pc->ops->apply               = PCApply_BJacobi_Singleblock;
    742:       pc->ops->matapply            = PCMatApply_BJacobi_Singleblock;
    743:       pc->ops->applysymmetricleft  = PCApplySymmetricLeft_BJacobi_Singleblock;
    744:       pc->ops->applysymmetricright = PCApplySymmetricRight_BJacobi_Singleblock;
    745:       pc->ops->applytranspose      = PCApplyTranspose_BJacobi_Singleblock;
    746:       pc->ops->setuponblocks       = PCSetUpOnBlocks_BJacobi_Singleblock;

    748:       PetscCall(PetscMalloc1(1, &jac->ksp));
    749:       jac->ksp[0] = ksp;

    751:       PetscCall(PetscNew(&bjac));
    752:       jac->data = (void *)bjac;
    753:     } else {
    754:       ksp  = jac->ksp[0];
    755:       bjac = (PC_BJacobi_Singleblock *)jac->data;
    756:     }

    758:     /*
    759:       The reason we need to generate these vectors is to serve
    760:       as the right-hand side and solution vector for the solve on the
    761:       block. We do not need to allocate space for the vectors since
    762:       that is provided via VecPlaceArray() just before the call to
    763:       KSPSolve() on the block.
    764:     */
    765:     PetscCall(MatGetSize(pmat, &m, &m));
    766:     PetscCall(VecCreateSeqWithArray(PETSC_COMM_SELF, 1, m, NULL, &bjac->x));
    767:     PetscCall(VecCreateSeqWithArray(PETSC_COMM_SELF, 1, m, NULL, &bjac->y));
    768:     PetscCall(MatGetVecType(pmat, &vectype));
    769:     PetscCall(VecSetType(bjac->x, vectype));
    770:     PetscCall(VecSetType(bjac->y, vectype));
    771:   } else {
    772:     ksp  = jac->ksp[0];
    773:     bjac = (PC_BJacobi_Singleblock *)jac->data;
    774:   }
    775:   PetscCall(KSPGetOptionsPrefix(ksp, &prefix));
    776:   if (pc->useAmat) {
    777:     PetscCall(KSPSetOperators(ksp, mat, pmat));
    778:     PetscCall(MatSetOptionsPrefix(mat, prefix));
    779:   } else {
    780:     PetscCall(KSPSetOperators(ksp, pmat, pmat));
    781:   }
    782:   PetscCall(MatSetOptionsPrefix(pmat, prefix));
    783:   if (!wasSetup && pc->setfromoptionscalled) {
    784:     /* If PCSetFromOptions_BJacobi is called later, KSPSetFromOptions will be called at that time. */
    785:     PetscCall(KSPSetFromOptions(ksp));
    786:   }
    787:   PetscFunctionReturn(PETSC_SUCCESS);
    788: }

    790: static PetscErrorCode PCReset_BJacobi_Multiblock(PC pc)
    791: {
    792:   PC_BJacobi            *jac  = (PC_BJacobi *)pc->data;
    793:   PC_BJacobi_Multiblock *bjac = (PC_BJacobi_Multiblock *)jac->data;
    794:   PetscInt               i;

    796:   PetscFunctionBegin;
    797:   if (bjac && bjac->pmat) {
    798:     PetscCall(MatDestroyMatrices(jac->n_local, &bjac->pmat));
    799:     if (pc->useAmat) PetscCall(MatDestroyMatrices(jac->n_local, &bjac->mat));
    800:   }

    802:   for (i = 0; i < jac->n_local; i++) {
    803:     PetscCall(KSPReset(jac->ksp[i]));
    804:     if (bjac && bjac->x) {
    805:       PetscCall(VecDestroy(&bjac->x[i]));
    806:       PetscCall(VecDestroy(&bjac->y[i]));
    807:       PetscCall(ISDestroy(&bjac->is[i]));
    808:     }
    809:   }
    810:   PetscCall(PetscFree(jac->l_lens));
    811:   PetscCall(PetscFree(jac->g_lens));
    812:   PetscFunctionReturn(PETSC_SUCCESS);
    813: }

    815: static PetscErrorCode PCDestroy_BJacobi_Multiblock(PC pc)
    816: {
    817:   PC_BJacobi            *jac  = (PC_BJacobi *)pc->data;
    818:   PC_BJacobi_Multiblock *bjac = (PC_BJacobi_Multiblock *)jac->data;
    819:   PetscInt               i;

    821:   PetscFunctionBegin;
    822:   PetscCall(PCReset_BJacobi_Multiblock(pc));
    823:   if (bjac) {
    824:     PetscCall(PetscFree2(bjac->x, bjac->y));
    825:     PetscCall(PetscFree(bjac->starts));
    826:     PetscCall(PetscFree(bjac->is));
    827:   }
    828:   PetscCall(PetscFree(jac->data));
    829:   for (i = 0; i < jac->n_local; i++) PetscCall(KSPDestroy(&jac->ksp[i]));
    830:   PetscCall(PetscFree(jac->ksp));
    831:   PetscCall(PCDestroy_BJacobi(pc));
    832:   PetscFunctionReturn(PETSC_SUCCESS);
    833: }

    835: static PetscErrorCode PCSetUpOnBlocks_BJacobi_Multiblock(PC pc)
    836: {
    837:   PC_BJacobi        *jac = (PC_BJacobi *)pc->data;
    838:   PetscInt           i, n_local = jac->n_local;
    839:   KSPConvergedReason reason;

    841:   PetscFunctionBegin;
    842:   for (i = 0; i < n_local; i++) {
    843:     PetscCall(KSPSetUp(jac->ksp[i]));
    844:     PetscCall(KSPGetConvergedReason(jac->ksp[i], &reason));
    845:     if (reason == KSP_DIVERGED_PC_FAILED) pc->failedreason = PC_SUBPC_ERROR;
    846:   }
    847:   PetscFunctionReturn(PETSC_SUCCESS);
    848: }

    850: static PetscErrorCode PCApply_BJacobi_Multiblock(PC pc, Vec x, Vec y)
    851: {
    852:   PC_BJacobi            *jac = (PC_BJacobi *)pc->data;
    853:   PetscInt               i, n_local = jac->n_local;
    854:   PC_BJacobi_Multiblock *bjac = (PC_BJacobi_Multiblock *)jac->data;
    855:   PetscScalar           *yin;
    856:   const PetscScalar     *xin;

    858:   PetscFunctionBegin;
    859:   PetscCall(VecGetArrayRead(x, &xin));
    860:   PetscCall(VecGetArray(y, &yin));
    861:   for (i = 0; i < n_local; i++) {
    862:     /*
    863:        To avoid copying the subvector from x into a workspace we instead
    864:        make the workspace vector array point to the subpart of the array of
    865:        the global vector.
    866:     */
    867:     PetscCall(VecPlaceArray(bjac->x[i], xin + bjac->starts[i]));
    868:     PetscCall(VecPlaceArray(bjac->y[i], yin + bjac->starts[i]));

    870:     PetscCall(PetscLogEventBegin(PC_ApplyOnBlocks, jac->ksp[i], bjac->x[i], bjac->y[i], 0));
    871:     PetscCall(KSPSolve(jac->ksp[i], bjac->x[i], bjac->y[i]));
    872:     PetscCall(KSPCheckSolve(jac->ksp[i], pc, bjac->y[i]));
    873:     PetscCall(PetscLogEventEnd(PC_ApplyOnBlocks, jac->ksp[i], bjac->x[i], bjac->y[i], 0));

    875:     PetscCall(VecResetArray(bjac->x[i]));
    876:     PetscCall(VecResetArray(bjac->y[i]));
    877:   }
    878:   PetscCall(VecRestoreArrayRead(x, &xin));
    879:   PetscCall(VecRestoreArray(y, &yin));
    880:   PetscFunctionReturn(PETSC_SUCCESS);
    881: }

    883: static PetscErrorCode PCApplySymmetricLeft_BJacobi_Multiblock(PC pc, Vec x, Vec y)
    884: {
    885:   PC_BJacobi            *jac = (PC_BJacobi *)pc->data;
    886:   PetscInt               i, n_local = jac->n_local;
    887:   PC_BJacobi_Multiblock *bjac = (PC_BJacobi_Multiblock *)jac->data;
    888:   PetscScalar           *yin;
    889:   const PetscScalar     *xin;
    890:   PC                     subpc;

    892:   PetscFunctionBegin;
    893:   PetscCall(VecGetArrayRead(x, &xin));
    894:   PetscCall(VecGetArray(y, &yin));
    895:   for (i = 0; i < n_local; i++) {
    896:     /*
    897:        To avoid copying the subvector from x into a workspace we instead
    898:        make the workspace vector array point to the subpart of the array of
    899:        the global vector.
    900:     */
    901:     PetscCall(VecPlaceArray(bjac->x[i], xin + bjac->starts[i]));
    902:     PetscCall(VecPlaceArray(bjac->y[i], yin + bjac->starts[i]));

    904:     PetscCall(PetscLogEventBegin(PC_ApplyOnBlocks, jac->ksp[i], bjac->x[i], bjac->y[i], 0));
    905:     /* apply the symmetric left portion of the inner PC operator */
    906:     /* note this bypasses the inner KSP and its options completely */
    907:     PetscCall(KSPGetPC(jac->ksp[i], &subpc));
    908:     PetscCall(PCApplySymmetricLeft(subpc, bjac->x[i], bjac->y[i]));
    909:     PetscCall(PetscLogEventEnd(PC_ApplyOnBlocks, jac->ksp[i], bjac->x[i], bjac->y[i], 0));

    911:     PetscCall(VecResetArray(bjac->x[i]));
    912:     PetscCall(VecResetArray(bjac->y[i]));
    913:   }
    914:   PetscCall(VecRestoreArrayRead(x, &xin));
    915:   PetscCall(VecRestoreArray(y, &yin));
    916:   PetscFunctionReturn(PETSC_SUCCESS);
    917: }

    919: static PetscErrorCode PCApplySymmetricRight_BJacobi_Multiblock(PC pc, Vec x, Vec y)
    920: {
    921:   PC_BJacobi            *jac = (PC_BJacobi *)pc->data;
    922:   PetscInt               i, n_local = jac->n_local;
    923:   PC_BJacobi_Multiblock *bjac = (PC_BJacobi_Multiblock *)jac->data;
    924:   PetscScalar           *yin;
    925:   const PetscScalar     *xin;
    926:   PC                     subpc;

    928:   PetscFunctionBegin;
    929:   PetscCall(VecGetArrayRead(x, &xin));
    930:   PetscCall(VecGetArray(y, &yin));
    931:   for (i = 0; i < n_local; i++) {
    932:     /*
    933:        To avoid copying the subvector from x into a workspace we instead
    934:        make the workspace vector array point to the subpart of the array of
    935:        the global vector.
    936:     */
    937:     PetscCall(VecPlaceArray(bjac->x[i], xin + bjac->starts[i]));
    938:     PetscCall(VecPlaceArray(bjac->y[i], yin + bjac->starts[i]));

    940:     PetscCall(PetscLogEventBegin(PC_ApplyOnBlocks, jac->ksp[i], bjac->x[i], bjac->y[i], 0));
    941:     /* apply the symmetric left portion of the inner PC operator */
    942:     /* note this bypasses the inner KSP and its options completely */
    943:     PetscCall(KSPGetPC(jac->ksp[i], &subpc));
    944:     PetscCall(PCApplySymmetricRight(subpc, bjac->x[i], bjac->y[i]));
    945:     PetscCall(PetscLogEventEnd(PC_ApplyOnBlocks, jac->ksp[i], bjac->x[i], bjac->y[i], 0));

    947:     PetscCall(VecResetArray(bjac->x[i]));
    948:     PetscCall(VecResetArray(bjac->y[i]));
    949:   }
    950:   PetscCall(VecRestoreArrayRead(x, &xin));
    951:   PetscCall(VecRestoreArray(y, &yin));
    952:   PetscFunctionReturn(PETSC_SUCCESS);
    953: }

    955: static PetscErrorCode PCApplyTranspose_BJacobi_Multiblock(PC pc, Vec x, Vec y)
    956: {
    957:   PC_BJacobi            *jac = (PC_BJacobi *)pc->data;
    958:   PetscInt               i, n_local = jac->n_local;
    959:   PC_BJacobi_Multiblock *bjac = (PC_BJacobi_Multiblock *)jac->data;
    960:   PetscScalar           *yin;
    961:   const PetscScalar     *xin;

    963:   PetscFunctionBegin;
    964:   PetscCall(VecGetArrayRead(x, &xin));
    965:   PetscCall(VecGetArray(y, &yin));
    966:   for (i = 0; i < n_local; i++) {
    967:     /*
    968:        To avoid copying the subvector from x into a workspace we instead
    969:        make the workspace vector array point to the subpart of the array of
    970:        the global vector.
    971:     */
    972:     PetscCall(VecPlaceArray(bjac->x[i], xin + bjac->starts[i]));
    973:     PetscCall(VecPlaceArray(bjac->y[i], yin + bjac->starts[i]));

    975:     PetscCall(PetscLogEventBegin(PC_ApplyTransposeOnBlocks, jac->ksp[i], bjac->x[i], bjac->y[i], 0));
    976:     PetscCall(KSPSolveTranspose(jac->ksp[i], bjac->x[i], bjac->y[i]));
    977:     PetscCall(KSPCheckSolve(jac->ksp[i], pc, bjac->y[i]));
    978:     PetscCall(PetscLogEventEnd(PC_ApplyTransposeOnBlocks, jac->ksp[i], bjac->x[i], bjac->y[i], 0));

    980:     PetscCall(VecResetArray(bjac->x[i]));
    981:     PetscCall(VecResetArray(bjac->y[i]));
    982:   }
    983:   PetscCall(VecRestoreArrayRead(x, &xin));
    984:   PetscCall(VecRestoreArray(y, &yin));
    985:   PetscFunctionReturn(PETSC_SUCCESS);
    986: }

    988: static PetscErrorCode PCSetUp_BJacobi_Multiblock(PC pc, Mat mat, Mat pmat)
    989: {
    990:   PC_BJacobi            *jac = (PC_BJacobi *)pc->data;
    991:   PetscInt               m, n_local, N, M, start, i;
    992:   const char            *prefix;
    993:   KSP                    ksp;
    994:   Vec                    x, y;
    995:   PC_BJacobi_Multiblock *bjac = (PC_BJacobi_Multiblock *)jac->data;
    996:   PC                     subpc;
    997:   IS                     is;
    998:   MatReuse               scall;
    999:   VecType                vectype;
    1000:   MatNullSpace          *nullsp_mat = NULL, *nullsp_pmat = NULL;

    1002:   PetscFunctionBegin;
    1003:   PetscCall(MatGetLocalSize(pc->pmat, &M, &N));

    1005:   n_local = jac->n_local;

    1007:   if (pc->useAmat) {
    1008:     PetscBool same;
    1009:     PetscCall(PetscObjectTypeCompare((PetscObject)mat, ((PetscObject)pmat)->type_name, &same));
    1010:     PetscCheck(same, PetscObjectComm((PetscObject)pc), PETSC_ERR_ARG_INCOMP, "Matrices not of same type");
    1011:   }

    1013:   if (!pc->setupcalled) {
    1014:     PetscInt nestlevel;

    1016:     scall = MAT_INITIAL_MATRIX;

    1018:     if (!jac->ksp) {
    1019:       pc->ops->reset               = PCReset_BJacobi_Multiblock;
    1020:       pc->ops->destroy             = PCDestroy_BJacobi_Multiblock;
    1021:       pc->ops->apply               = PCApply_BJacobi_Multiblock;
    1022:       pc->ops->matapply            = NULL;
    1023:       pc->ops->applysymmetricleft  = PCApplySymmetricLeft_BJacobi_Multiblock;
    1024:       pc->ops->applysymmetricright = PCApplySymmetricRight_BJacobi_Multiblock;
    1025:       pc->ops->applytranspose      = PCApplyTranspose_BJacobi_Multiblock;
    1026:       pc->ops->setuponblocks       = PCSetUpOnBlocks_BJacobi_Multiblock;

    1028:       PetscCall(PetscNew(&bjac));
    1029:       PetscCall(PetscMalloc1(n_local, &jac->ksp));
    1030:       PetscCall(PetscMalloc2(n_local, &bjac->x, n_local, &bjac->y));
    1031:       PetscCall(PetscMalloc1(n_local, &bjac->starts));

    1033:       jac->data = (void *)bjac;
    1034:       PetscCall(PetscMalloc1(n_local, &bjac->is));

    1036:       for (i = 0; i < n_local; i++) {
    1037:         PetscCall(KSPCreate(PETSC_COMM_SELF, &ksp));
    1038:         PetscCall(PCGetKSPNestLevel(pc, &nestlevel));
    1039:         PetscCall(KSPSetNestLevel(ksp, nestlevel + 1));
    1040:         PetscCall(KSPSetErrorIfNotConverged(ksp, pc->erroriffailure));
    1041:         PetscCall(PetscObjectIncrementTabLevel((PetscObject)ksp, (PetscObject)pc, 1));
    1042:         PetscCall(KSPSetType(ksp, KSPPREONLY));
    1043:         PetscCall(KSPGetPC(ksp, &subpc));
    1044:         PetscCall(PCGetOptionsPrefix(pc, &prefix));
    1045:         PetscCall(KSPSetOptionsPrefix(ksp, prefix));
    1046:         PetscCall(KSPAppendOptionsPrefix(ksp, "sub_"));

    1048:         jac->ksp[i] = ksp;
    1049:       }
    1050:     } else {
    1051:       bjac = (PC_BJacobi_Multiblock *)jac->data;
    1052:     }

    1054:     start = 0;
    1055:     PetscCall(MatGetVecType(pmat, &vectype));
    1056:     for (i = 0; i < n_local; i++) {
    1057:       m = jac->l_lens[i];
    1058:       /*
    1059:       The reason we need to generate these vectors is to serve
    1060:       as the right-hand side and solution vector for the solve on the
    1061:       block. We do not need to allocate space for the vectors since
    1062:       that is provided via VecPlaceArray() just before the call to
    1063:       KSPSolve() on the block.

    1065:       */
    1066:       PetscCall(VecCreateSeq(PETSC_COMM_SELF, m, &x));
    1067:       PetscCall(VecCreateSeqWithArray(PETSC_COMM_SELF, 1, m, NULL, &y));
    1068:       PetscCall(VecSetType(x, vectype));
    1069:       PetscCall(VecSetType(y, vectype));

    1071:       bjac->x[i]      = x;
    1072:       bjac->y[i]      = y;
    1073:       bjac->starts[i] = start;

    1075:       PetscCall(ISCreateStride(PETSC_COMM_SELF, m, start, 1, &is));
    1076:       bjac->is[i] = is;

    1078:       start += m;
    1079:     }
    1080:   } else {
    1081:     bjac = (PC_BJacobi_Multiblock *)jac->data;
    1082:     /*
    1083:        Destroy the blocks from the previous iteration
    1084:     */
    1085:     if (pc->flag == DIFFERENT_NONZERO_PATTERN) {
    1086:       PetscCall(MatGetNullSpaces(n_local, bjac->pmat, &nullsp_pmat));
    1087:       PetscCall(MatDestroyMatrices(n_local, &bjac->pmat));
    1088:       if (pc->useAmat) {
    1089:         PetscCall(MatGetNullSpaces(n_local, bjac->mat, &nullsp_mat));
    1090:         PetscCall(MatDestroyMatrices(n_local, &bjac->mat));
    1091:       }
    1092:       scall = MAT_INITIAL_MATRIX;
    1093:     } else scall = MAT_REUSE_MATRIX;
    1094:   }

    1096:   PetscCall(MatCreateSubMatrices(pmat, n_local, bjac->is, bjac->is, scall, &bjac->pmat));
    1097:   if (nullsp_pmat) PetscCall(MatRestoreNullSpaces(n_local, bjac->pmat, &nullsp_pmat));
    1098:   if (pc->useAmat) {
    1099:     PetscCall(MatCreateSubMatrices(mat, n_local, bjac->is, bjac->is, scall, &bjac->mat));
    1100:     if (nullsp_mat) PetscCall(MatRestoreNullSpaces(n_local, bjac->mat, &nullsp_mat));
    1101:   }
    1102:   /* Return control to the user so that the submatrices can be modified (e.g., to apply
    1103:      different boundary conditions for the submatrices than for the global problem) */
    1104:   PetscCall(PCModifySubMatrices(pc, n_local, bjac->is, bjac->is, bjac->pmat, pc->modifysubmatricesP));

    1106:   for (i = 0; i < n_local; i++) {
    1107:     PetscCall(KSPGetOptionsPrefix(jac->ksp[i], &prefix));
    1108:     if (pc->useAmat) {
    1109:       PetscCall(KSPSetOperators(jac->ksp[i], bjac->mat[i], bjac->pmat[i]));
    1110:       PetscCall(MatSetOptionsPrefix(bjac->mat[i], prefix));
    1111:     } else {
    1112:       PetscCall(KSPSetOperators(jac->ksp[i], bjac->pmat[i], bjac->pmat[i]));
    1113:     }
    1114:     PetscCall(MatSetOptionsPrefix(bjac->pmat[i], prefix));
    1115:     if (pc->setfromoptionscalled) PetscCall(KSPSetFromOptions(jac->ksp[i]));
    1116:   }
    1117:   PetscFunctionReturn(PETSC_SUCCESS);
    1118: }

    1120: /*
    1121:       These are for a single block with multiple processes
    1122: */
    1123: static PetscErrorCode PCSetUpOnBlocks_BJacobi_Multiproc(PC pc)
    1124: {
    1125:   PC_BJacobi        *jac    = (PC_BJacobi *)pc->data;
    1126:   KSP                subksp = jac->ksp[0];
    1127:   KSPConvergedReason reason;

    1129:   PetscFunctionBegin;
    1130:   PetscCall(KSPSetUp(subksp));
    1131:   PetscCall(KSPGetConvergedReason(subksp, &reason));
    1132:   if (reason == KSP_DIVERGED_PC_FAILED) pc->failedreason = PC_SUBPC_ERROR;
    1133:   PetscFunctionReturn(PETSC_SUCCESS);
    1134: }

    1136: static PetscErrorCode PCReset_BJacobi_Multiproc(PC pc)
    1137: {
    1138:   PC_BJacobi           *jac   = (PC_BJacobi *)pc->data;
    1139:   PC_BJacobi_Multiproc *mpjac = (PC_BJacobi_Multiproc *)jac->data;

    1141:   PetscFunctionBegin;
    1142:   PetscCall(VecDestroy(&mpjac->ysub));
    1143:   PetscCall(VecDestroy(&mpjac->xsub));
    1144:   PetscCall(MatDestroy(&mpjac->submats));
    1145:   if (jac->ksp) PetscCall(KSPReset(jac->ksp[0]));
    1146:   PetscFunctionReturn(PETSC_SUCCESS);
    1147: }

    1149: static PetscErrorCode PCDestroy_BJacobi_Multiproc(PC pc)
    1150: {
    1151:   PC_BJacobi           *jac   = (PC_BJacobi *)pc->data;
    1152:   PC_BJacobi_Multiproc *mpjac = (PC_BJacobi_Multiproc *)jac->data;

    1154:   PetscFunctionBegin;
    1155:   PetscCall(PCReset_BJacobi_Multiproc(pc));
    1156:   PetscCall(KSPDestroy(&jac->ksp[0]));
    1157:   PetscCall(PetscFree(jac->ksp));
    1158:   PetscCall(PetscSubcommDestroy(&mpjac->psubcomm));

    1160:   PetscCall(PetscFree(mpjac));
    1161:   PetscCall(PCDestroy_BJacobi(pc));
    1162:   PetscFunctionReturn(PETSC_SUCCESS);
    1163: }

    1165: static PetscErrorCode PCApply_BJacobi_Multiproc(PC pc, Vec x, Vec y)
    1166: {
    1167:   PC_BJacobi           *jac   = (PC_BJacobi *)pc->data;
    1168:   PC_BJacobi_Multiproc *mpjac = (PC_BJacobi_Multiproc *)jac->data;
    1169:   PetscScalar          *yarray;
    1170:   const PetscScalar    *xarray;
    1171:   KSPConvergedReason    reason;

    1173:   PetscFunctionBegin;
    1174:   /* place x's and y's local arrays into xsub and ysub */
    1175:   PetscCall(VecGetArrayRead(x, &xarray));
    1176:   PetscCall(VecGetArray(y, &yarray));
    1177:   PetscCall(VecPlaceArray(mpjac->xsub, xarray));
    1178:   PetscCall(VecPlaceArray(mpjac->ysub, yarray));

    1180:   /* apply preconditioner on each matrix block */
    1181:   PetscCall(PetscLogEventBegin(PC_ApplyOnBlocks, jac->ksp[0], mpjac->xsub, mpjac->ysub, 0));
    1182:   PetscCall(KSPSolve(jac->ksp[0], mpjac->xsub, mpjac->ysub));
    1183:   PetscCall(KSPCheckSolve(jac->ksp[0], pc, mpjac->ysub));
    1184:   PetscCall(PetscLogEventEnd(PC_ApplyOnBlocks, jac->ksp[0], mpjac->xsub, mpjac->ysub, 0));
    1185:   PetscCall(KSPGetConvergedReason(jac->ksp[0], &reason));
    1186:   if (reason == KSP_DIVERGED_PC_FAILED) pc->failedreason = PC_SUBPC_ERROR;

    1188:   PetscCall(VecResetArray(mpjac->xsub));
    1189:   PetscCall(VecResetArray(mpjac->ysub));
    1190:   PetscCall(VecRestoreArrayRead(x, &xarray));
    1191:   PetscCall(VecRestoreArray(y, &yarray));
    1192:   PetscFunctionReturn(PETSC_SUCCESS);
    1193: }

    1195: static PetscErrorCode PCMatApply_BJacobi_Multiproc(PC pc, Mat X, Mat Y)
    1196: {
    1197:   PC_BJacobi        *jac = (PC_BJacobi *)pc->data;
    1198:   KSPConvergedReason reason;
    1199:   Mat                sX, sY;
    1200:   const PetscScalar *x;
    1201:   PetscScalar       *y;
    1202:   PetscInt           m, N, lda, ldb;

    1204:   PetscFunctionBegin;
    1205:   /* apply preconditioner on each matrix block */
    1206:   PetscCall(MatGetLocalSize(X, &m, NULL));
    1207:   PetscCall(MatGetSize(X, NULL, &N));
    1208:   PetscCall(MatDenseGetLDA(X, &lda));
    1209:   PetscCall(MatDenseGetLDA(Y, &ldb));
    1210:   PetscCall(MatDenseGetArrayRead(X, &x));
    1211:   PetscCall(MatDenseGetArrayWrite(Y, &y));
    1212:   PetscCall(MatCreateDense(PetscObjectComm((PetscObject)jac->ksp[0]), m, PETSC_DECIDE, PETSC_DECIDE, N, (PetscScalar *)x, &sX));
    1213:   PetscCall(MatCreateDense(PetscObjectComm((PetscObject)jac->ksp[0]), m, PETSC_DECIDE, PETSC_DECIDE, N, y, &sY));
    1214:   PetscCall(MatDenseSetLDA(sX, lda));
    1215:   PetscCall(MatDenseSetLDA(sY, ldb));
    1216:   PetscCall(PetscLogEventBegin(PC_ApplyOnBlocks, jac->ksp[0], X, Y, 0));
    1217:   PetscCall(KSPMatSolve(jac->ksp[0], sX, sY));
    1218:   PetscCall(KSPCheckSolve(jac->ksp[0], pc, NULL));
    1219:   PetscCall(PetscLogEventEnd(PC_ApplyOnBlocks, jac->ksp[0], X, Y, 0));
    1220:   PetscCall(MatDestroy(&sY));
    1221:   PetscCall(MatDestroy(&sX));
    1222:   PetscCall(MatDenseRestoreArrayWrite(Y, &y));
    1223:   PetscCall(MatDenseRestoreArrayRead(X, &x));
    1224:   PetscCall(KSPGetConvergedReason(jac->ksp[0], &reason));
    1225:   if (reason == KSP_DIVERGED_PC_FAILED) pc->failedreason = PC_SUBPC_ERROR;
    1226:   PetscFunctionReturn(PETSC_SUCCESS);
    1227: }

    1229: static PetscErrorCode PCSetUp_BJacobi_Multiproc(PC pc)
    1230: {
    1231:   PC_BJacobi           *jac   = (PC_BJacobi *)pc->data;
    1232:   PC_BJacobi_Multiproc *mpjac = (PC_BJacobi_Multiproc *)jac->data;
    1233:   PetscInt              m, n;
    1234:   MPI_Comm              comm, subcomm = 0;
    1235:   const char           *prefix;
    1236:   PetscBool             wasSetup = PETSC_TRUE;
    1237:   VecType               vectype;

    1239:   PetscFunctionBegin;
    1240:   PetscCall(PetscObjectGetComm((PetscObject)pc, &comm));
    1241:   PetscCheck(jac->n_local <= 1, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Only a single block in a subcommunicator is supported");
    1242:   jac->n_local = 1; /* currently only a single block is supported for a subcommunicator */
    1243:   if (!pc->setupcalled) {
    1244:     PetscInt nestlevel;

    1246:     wasSetup = PETSC_FALSE;
    1247:     PetscCall(PetscNew(&mpjac));
    1248:     jac->data = (void *)mpjac;

    1250:     /* initialize datastructure mpjac */
    1251:     if (!jac->psubcomm) {
    1252:       /* Create default contiguous subcommunicatiors if user does not provide them */
    1253:       PetscCall(PetscSubcommCreate(comm, &jac->psubcomm));
    1254:       PetscCall(PetscSubcommSetNumber(jac->psubcomm, jac->n));
    1255:       PetscCall(PetscSubcommSetType(jac->psubcomm, PETSC_SUBCOMM_CONTIGUOUS));
    1256:     }
    1257:     mpjac->psubcomm = jac->psubcomm;
    1258:     subcomm         = PetscSubcommChild(mpjac->psubcomm);

    1260:     /* Get matrix blocks of pmat */
    1261:     PetscCall(MatGetMultiProcBlock(pc->pmat, subcomm, MAT_INITIAL_MATRIX, &mpjac->submats));

    1263:     /* create a new PC that processors in each subcomm have copy of */
    1264:     PetscCall(PetscMalloc1(1, &jac->ksp));
    1265:     PetscCall(KSPCreate(subcomm, &jac->ksp[0]));
    1266:     PetscCall(PCGetKSPNestLevel(pc, &nestlevel));
    1267:     PetscCall(KSPSetNestLevel(jac->ksp[0], nestlevel + 1));
    1268:     PetscCall(KSPSetErrorIfNotConverged(jac->ksp[0], pc->erroriffailure));
    1269:     PetscCall(PetscObjectIncrementTabLevel((PetscObject)jac->ksp[0], (PetscObject)pc, 1));
    1270:     PetscCall(KSPSetOperators(jac->ksp[0], mpjac->submats, mpjac->submats));
    1271:     PetscCall(KSPGetPC(jac->ksp[0], &mpjac->pc));

    1273:     PetscCall(PCGetOptionsPrefix(pc, &prefix));
    1274:     PetscCall(KSPSetOptionsPrefix(jac->ksp[0], prefix));
    1275:     PetscCall(KSPAppendOptionsPrefix(jac->ksp[0], "sub_"));
    1276:     PetscCall(KSPGetOptionsPrefix(jac->ksp[0], &prefix));
    1277:     PetscCall(MatSetOptionsPrefix(mpjac->submats, prefix));

    1279:     /* create dummy vectors xsub and ysub */
    1280:     PetscCall(MatGetLocalSize(mpjac->submats, &m, &n));
    1281:     PetscCall(VecCreateMPIWithArray(subcomm, 1, n, PETSC_DECIDE, NULL, &mpjac->xsub));
    1282:     PetscCall(VecCreateMPIWithArray(subcomm, 1, m, PETSC_DECIDE, NULL, &mpjac->ysub));
    1283:     PetscCall(MatGetVecType(mpjac->submats, &vectype));
    1284:     PetscCall(VecSetType(mpjac->xsub, vectype));
    1285:     PetscCall(VecSetType(mpjac->ysub, vectype));

    1287:     pc->ops->setuponblocks = PCSetUpOnBlocks_BJacobi_Multiproc;
    1288:     pc->ops->reset         = PCReset_BJacobi_Multiproc;
    1289:     pc->ops->destroy       = PCDestroy_BJacobi_Multiproc;
    1290:     pc->ops->apply         = PCApply_BJacobi_Multiproc;
    1291:     pc->ops->matapply      = PCMatApply_BJacobi_Multiproc;
    1292:   } else { /* pc->setupcalled */
    1293:     subcomm = PetscSubcommChild(mpjac->psubcomm);
    1294:     if (pc->flag == DIFFERENT_NONZERO_PATTERN) {
    1295:       /* destroy old matrix blocks, then get new matrix blocks */
    1296:       if (mpjac->submats) PetscCall(MatDestroy(&mpjac->submats));
    1297:       PetscCall(MatGetMultiProcBlock(pc->pmat, subcomm, MAT_INITIAL_MATRIX, &mpjac->submats));
    1298:     } else {
    1299:       PetscCall(MatGetMultiProcBlock(pc->pmat, subcomm, MAT_REUSE_MATRIX, &mpjac->submats));
    1300:     }
    1301:     PetscCall(KSPSetOperators(jac->ksp[0], mpjac->submats, mpjac->submats));
    1302:   }

    1304:   if (!wasSetup && pc->setfromoptionscalled) PetscCall(KSPSetFromOptions(jac->ksp[0]));
    1305:   PetscFunctionReturn(PETSC_SUCCESS);
    1306: }