Actual source code: telescope_coarsedm.c

      1: #include <petsc/private/matimpl.h>
      2: #include <petsc/private/pcimpl.h>
      3: #include <petsc/private/dmimpl.h>
      4: #include <petscksp.h>
      5: #include <petscdm.h>
      6: #include <petscdmda.h>
      7: #include <petscdmshell.h>

      9: #include "../src/ksp/pc/impls/telescope/telescope.h"

     11: static PetscBool  cited      = PETSC_FALSE;
     12: static const char citation[] = "@inproceedings{MaySananRuppKnepleySmith2016,\n"
     13:                                "  title     = {Extreme-Scale Multigrid Components within PETSc},\n"
     14:                                "  author    = {Dave A. May and Patrick Sanan and Karl Rupp and Matthew G. Knepley and Barry F. Smith},\n"
     15:                                "  booktitle = {Proceedings of the Platform for Advanced Scientific Computing Conference},\n"
     16:                                "  series    = {PASC '16},\n"
     17:                                "  isbn      = {978-1-4503-4126-4},\n"
     18:                                "  location  = {Lausanne, Switzerland},\n"
     19:                                "  pages     = {5:1--5:12},\n"
     20:                                "  articleno = {5},\n"
     21:                                "  numpages  = {12},\n"
     22:                                "  url       = {https://doi.acm.org/10.1145/2929908.2929913},\n"
     23:                                "  doi       = {10.1145/2929908.2929913},\n"
     24:                                "  acmid     = {2929913},\n"
     25:                                "  publisher = {ACM},\n"
     26:                                "  address   = {New York, NY, USA},\n"
     27:                                "  keywords  = {GPU, HPC, agglomeration, coarse-level solver, multigrid, parallel computing, preconditioning},\n"
     28:                                "  year      = {2016}\n"
     29:                                "}\n";

     31: typedef struct {
     32:   DM  dm_fine, dm_coarse; /* these DM's should be topologically identical but use different communicators */
     33:   Mat permutation;
     34:   Vec xp;
     35:   PetscErrorCode (*fp_dm_field_scatter)(DM, Vec, ScatterMode, DM, Vec);
     36:   PetscErrorCode (*fp_dm_state_scatter)(DM, ScatterMode, DM);
     37:   void *dmksp_context_determined;
     38:   void *dmksp_context_user;
     39: } PC_Telescope_CoarseDMCtx;

     41: static PetscErrorCode PCTelescopeSetUp_scatters_CoarseDM(PC pc, PC_Telescope sred, PC_Telescope_CoarseDMCtx *ctx)
     42: {
     43:   Vec        xred, yred, xtmp, x, xp;
     44:   VecScatter scatter;
     45:   IS         isin;
     46:   Mat        B;
     47:   PetscInt   m, bs, st, ed;
     48:   MPI_Comm   comm;

     50:   PetscFunctionBegin;
     51:   PetscCall(PetscObjectGetComm((PetscObject)pc, &comm));
     52:   PetscCall(PCGetOperators(pc, NULL, &B));
     53:   PetscCall(MatCreateVecs(B, &x, NULL));
     54:   PetscCall(MatGetBlockSize(B, &bs));
     55:   PetscCall(VecDuplicate(x, &xp));
     56:   m    = 0;
     57:   xred = NULL;
     58:   yred = NULL;
     59:   if (PCTelescope_isActiveRank(sred)) {
     60:     PetscCall(DMCreateGlobalVector(ctx->dm_coarse, &xred));
     61:     PetscCall(VecDuplicate(xred, &yred));
     62:     PetscCall(VecGetOwnershipRange(xred, &st, &ed));
     63:     PetscCall(ISCreateStride(comm, ed - st, st, 1, &isin));
     64:     PetscCall(VecGetLocalSize(xred, &m));
     65:   } else {
     66:     PetscCall(VecGetOwnershipRange(x, &st, &ed));
     67:     PetscCall(ISCreateStride(comm, 0, st, 1, &isin));
     68:   }
     69:   PetscCall(ISSetBlockSize(isin, bs));
     70:   PetscCall(VecCreate(comm, &xtmp));
     71:   PetscCall(VecSetSizes(xtmp, m, PETSC_DECIDE));
     72:   PetscCall(VecSetBlockSize(xtmp, bs));
     73:   PetscCall(VecSetType(xtmp, ((PetscObject)x)->type_name));
     74:   PetscCall(VecScatterCreate(x, isin, xtmp, NULL, &scatter));
     75:   sred->xred    = xred;
     76:   sred->yred    = yred;
     77:   sred->isin    = isin;
     78:   sred->scatter = scatter;
     79:   sred->xtmp    = xtmp;
     80:   ctx->xp       = xp;
     81:   PetscCall(VecDestroy(&x));
     82:   PetscFunctionReturn(PETSC_SUCCESS);
     83: }

     85: PetscErrorCode PCTelescopeSetUp_CoarseDM(PC pc, PC_Telescope sred)
     86: {
     87:   PC_Telescope_CoarseDMCtx *ctx;
     88:   DM                        dm, dm_coarse = NULL;
     89:   MPI_Comm                  comm;
     90:   PetscBool                 has_perm, has_kspcomputeoperators, using_kspcomputeoperators;

     92:   PetscFunctionBegin;
     93:   PetscCall(PetscInfo(pc, "PCTelescope: setup (CoarseDM)\n"));
     94:   PetscCall(PetscNew(&ctx));
     95:   sred->dm_ctx = (void *)ctx;

     97:   PetscCall(PetscObjectGetComm((PetscObject)pc, &comm));
     98:   PetscCall(PCGetDM(pc, &dm));
     99:   PetscCall(DMGetCoarseDM(dm, &dm_coarse));
    100:   ctx->dm_fine   = dm;
    101:   ctx->dm_coarse = dm_coarse;

    103:   /* attach coarse dm to ksp on sub communicator */
    104:   if (PCTelescope_isActiveRank(sred)) {
    105:     PetscCall(KSPSetDM(sred->ksp, ctx->dm_coarse));
    106:     if (sred->ignore_kspcomputeoperators) PetscCall(KSPSetDMActive(sred->ksp, KSP_DMACTIVE_ALL, PETSC_FALSE));
    107:   }

    109:   /* check if there is a method to provide a permutation */
    110:   has_perm                  = PETSC_FALSE;
    111:   has_kspcomputeoperators   = PETSC_FALSE;
    112:   using_kspcomputeoperators = PETSC_FALSE;

    114:   /* if no permutation is provided, we must rely on KSPSetComputeOperators */
    115:   {
    116:     PetscErrorCode (*dmfine_kspfunc)(KSP, Mat, Mat, void *) = NULL;
    117:     void *dmfine_kspctx = NULL, *dmcoarse_kspctx = NULL;
    118:     void *dmfine_appctx = NULL, *dmcoarse_appctx = NULL;
    119:     void *dmfine_shellctx = NULL, *dmcoarse_shellctx = NULL;

    121:     PetscCall(DMKSPGetComputeOperators(dm, &dmfine_kspfunc, &dmfine_kspctx));
    122:     if (dmfine_kspfunc) has_kspcomputeoperators = PETSC_TRUE;

    124:     PetscCall(DMGetApplicationContext(ctx->dm_fine, &dmfine_appctx));
    125:     PetscCall(DMShellGetContext(ctx->dm_fine, &dmfine_shellctx));

    127:     /* need to define dmcoarse_kspctx */
    128:     if (dmfine_kspfunc && !sred->ignore_kspcomputeoperators) {
    129:       PetscCall(PetscInfo(pc, "PCTelescope: KSPSetComputeOperators fetched from parent DM\n"));
    130:       if (PCTelescope_isActiveRank(sred)) {
    131:         PetscCall(DMGetApplicationContext(ctx->dm_coarse, &dmcoarse_appctx));
    132:         PetscCall(DMShellGetContext(ctx->dm_coarse, &dmcoarse_shellctx));
    133:       }

    135:       /* Assume that if the fine operator didn't require any context, neither will the coarse */
    136:       if (!dmfine_kspctx) {
    137:         dmcoarse_kspctx = NULL;
    138:         PetscCall(PetscInfo(pc, "PCTelescope: KSPSetComputeOperators using NULL context\n"));
    139:       } else {
    140:         PetscCall(PetscInfo(pc, "PCTelescope: KSPSetComputeOperators detected non-NULL context from parent DM \n"));
    141:         if (PCTelescope_isActiveRank(sred)) {
    142:           if (dmfine_kspctx == dmfine_appctx) {
    143:             dmcoarse_kspctx = dmcoarse_appctx;
    144:             PetscCall(PetscInfo(pc, "PCTelescope: KSPSetComputeOperators using context from DM->ApplicationContext\n"));
    145:             PetscCheck(dmcoarse_kspctx, PETSC_COMM_SELF, PETSC_ERR_USER, "Non NULL dmfine->kspctx == dmfine->appctx. NULL dmcoarse->appctx found. Likely this is an error");
    146:           } else if (dmfine_kspctx == dmfine_shellctx) {
    147:             dmcoarse_kspctx = dmcoarse_shellctx;
    148:             PetscCall(PetscInfo(pc, "PCTelescope: KSPSetComputeOperators using context from DMShell->Context\n"));
    149:             PetscCheck(dmcoarse_kspctx, PETSC_COMM_SELF, PETSC_ERR_USER, "Non NULL dmfine->kspctx == dmfine.shell->ctx. NULL dmcoarse.shell->ctx found. Likely this is an error");
    150:           }
    151:           ctx->dmksp_context_determined = dmcoarse_kspctx;

    153:           /* look for user provided method to fetch the context */
    154:           {
    155:             PetscErrorCode (*fp_get_coarsedm_context)(DM, void **) = NULL;
    156:             void *dmcoarse_context_user                            = NULL;
    157:             char  dmcoarse_method[PETSC_MAX_PATH_LEN];

    159:             PetscCall(PetscSNPrintf(dmcoarse_method, sizeof(dmcoarse_method), "PCTelescopeGetCoarseDMKSPContext"));
    160:             PetscCall(PetscObjectQueryFunction((PetscObject)ctx->dm_coarse, dmcoarse_method, &fp_get_coarsedm_context));
    161:             if (fp_get_coarsedm_context) {
    162:               PetscCall(PetscInfo(pc, "PCTelescope: Found composed method PCTelescopeGetCoarseDMKSPContext from coarse DM\n"));
    163:               PetscCall(fp_get_coarsedm_context(ctx->dm_coarse, &dmcoarse_context_user));
    164:               ctx->dmksp_context_user = dmcoarse_context_user;
    165:               dmcoarse_kspctx         = dmcoarse_context_user;
    166:             } else {
    167:               PetscCall(PetscInfo(pc, "PCTelescope: Failed to find composed method PCTelescopeGetCoarseDMKSPContext from coarse DM\n"));
    168:             }
    169:           }

    171:           if (!dmcoarse_kspctx) {
    172:             PetscCall(PetscInfo(pc, "PCTelescope: KSPSetComputeOperators failed to determine the context to use on sub-communicator\n"));
    173:             SETERRQ(PETSC_COMM_SELF, PETSC_ERR_USER, "Cannot determine which context with use for KSPSetComputeOperators() on sub-communicator");
    174:           }
    175:         }
    176:       }
    177:     }

    179:     if (dmfine_kspfunc && !sred->ignore_kspcomputeoperators) {
    180:       using_kspcomputeoperators = PETSC_TRUE;

    182:       if (PCTelescope_isActiveRank(sred)) {
    183:         /* sub ksp inherits dmksp_func and context provided by user */
    184:         PetscCall(KSPSetComputeOperators(sred->ksp, dmfine_kspfunc, dmcoarse_kspctx));
    185:         /* PetscCall(PetscObjectCopyFortranFunctionPointers((PetscObject)dm,(PetscObject)ctx->dmrepart)); */
    186:         PetscCall(KSPSetDMActive(sred->ksp, KSP_DMACTIVE_ALL, PETSC_TRUE));
    187:       }
    188:     }
    189:   }

    191:   PetscCheck(has_perm || !has_kspcomputeoperators || using_kspcomputeoperators, comm, PETSC_ERR_SUP, "No method to permute an operator was found on the parent DM. A method for KSPSetComputeOperators() was provided but it was requested to be ignored. Telescope setup cannot proceed");
    192:   PetscCheck(has_perm || has_kspcomputeoperators, comm, PETSC_ERR_SUP, "No method to permute an operator was found on the parent DM. No method for KSPSetComputeOperators() was provided. Telescope setup cannot proceed");

    194:   {
    195:     char dmfine_method[PETSC_MAX_PATH_LEN];

    197:     PetscCall(PetscSNPrintf(dmfine_method, sizeof(dmfine_method), "PCTelescopeFieldScatter"));
    198:     PetscCall(PetscObjectQueryFunction((PetscObject)ctx->dm_fine, dmfine_method, &ctx->fp_dm_field_scatter));

    200:     PetscCall(PetscSNPrintf(dmfine_method, sizeof(dmfine_method), "PCTelescopeStateScatter"));
    201:     PetscCall(PetscObjectQueryFunction((PetscObject)ctx->dm_fine, dmfine_method, &ctx->fp_dm_state_scatter));
    202:   }

    204:   if (ctx->fp_dm_state_scatter) {
    205:     PetscCall(PetscInfo(pc, "PCTelescope: Found composed method PCTelescopeStateScatter from parent DM\n"));
    206:   } else {
    207:     PetscCall(PetscInfo(pc, "PCTelescope: Failed to find composed method PCTelescopeStateScatter from parent DM\n"));
    208:   }

    210:   if (ctx->fp_dm_field_scatter) {
    211:     PetscCall(PetscInfo(pc, "PCTelescope: Found composed method PCTelescopeFieldScatter from parent DM\n"));
    212:   } else {
    213:     PetscCall(PetscInfo(pc, "PCTelescope: Failed to find composed method PCTelescopeFieldScatter from parent DM\n"));
    214:     SETERRQ(comm, PETSC_ERR_SUP, "No method to scatter fields between the parent DM and coarse DM was found. Must call PetscObjectComposeFunction() with the parent DM. Telescope setup cannot proceed");
    215:   }

    217:   /* PetscCall(PCTelescopeSetUp_permutation_CoarseDM(pc,sred,ctx)); */
    218:   PetscCall(PCTelescopeSetUp_scatters_CoarseDM(pc, sred, ctx));
    219:   PetscFunctionReturn(PETSC_SUCCESS);
    220: }

    222: PetscErrorCode PCApply_Telescope_CoarseDM(PC pc, Vec x, Vec y)
    223: {
    224:   PC_Telescope              sred = (PC_Telescope)pc->data;
    225:   Vec                       xred, yred;
    226:   PC_Telescope_CoarseDMCtx *ctx;

    228:   PetscFunctionBegin;
    229:   ctx  = (PC_Telescope_CoarseDMCtx *)sred->dm_ctx;
    230:   xred = sred->xred;
    231:   yred = sred->yred;

    233:   PetscCall(PetscCitationsRegister(citation, &cited));

    235:   if (ctx->fp_dm_state_scatter) PetscCall(ctx->fp_dm_state_scatter(ctx->dm_fine, SCATTER_FORWARD, ctx->dm_coarse));

    237:   PetscCall(ctx->fp_dm_field_scatter(ctx->dm_fine, x, SCATTER_FORWARD, ctx->dm_coarse, xred));

    239:   /* solve */
    240:   if (PCTelescope_isActiveRank(sred)) PetscCall(KSPSolve(sred->ksp, xred, yred));

    242:   PetscCall(ctx->fp_dm_field_scatter(ctx->dm_fine, y, SCATTER_REVERSE, ctx->dm_coarse, yred));
    243:   PetscFunctionReturn(PETSC_SUCCESS);
    244: }

    246: static PetscErrorCode PCTelescopeSubNullSpaceCreate_CoarseDM(PC pc, PC_Telescope sred, MatNullSpace nullspace, MatNullSpace *sub_nullspace)
    247: {
    248:   PetscBool                 has_const;
    249:   PetscInt                  k, n = 0;
    250:   const Vec                *vecs;
    251:   Vec                      *sub_vecs = NULL;
    252:   MPI_Comm                  subcomm;
    253:   PC_Telescope_CoarseDMCtx *ctx;

    255:   PetscFunctionBegin;
    256:   ctx     = (PC_Telescope_CoarseDMCtx *)sred->dm_ctx;
    257:   subcomm = sred->subcomm;
    258:   PetscCall(MatNullSpaceGetVecs(nullspace, &has_const, &n, &vecs));

    260:   if (PCTelescope_isActiveRank(sred)) {
    261:     /* create new vectors */
    262:     if (n) PetscCall(VecDuplicateVecs(sred->xred, n, &sub_vecs));
    263:   }

    265:   /* copy entries */
    266:   for (k = 0; k < n; k++) PetscCall(ctx->fp_dm_field_scatter(ctx->dm_fine, vecs[k], SCATTER_FORWARD, ctx->dm_coarse, sub_vecs[k]));

    268:   if (PCTelescope_isActiveRank(sred)) {
    269:     /* create new (near) nullspace for redundant object */
    270:     PetscCall(MatNullSpaceCreate(subcomm, has_const, n, sub_vecs, sub_nullspace));
    271:     PetscCall(VecDestroyVecs(n, &sub_vecs));
    272:   }
    273:   PetscFunctionReturn(PETSC_SUCCESS);
    274: }

    276: PetscErrorCode PCTelescopeMatNullSpaceCreate_CoarseDM(PC pc, PC_Telescope sred, Mat sub_mat)
    277: {
    278:   Mat                       B;
    279:   PC_Telescope_CoarseDMCtx *ctx;

    281:   PetscFunctionBegin;
    282:   ctx = (PC_Telescope_CoarseDMCtx *)sred->dm_ctx;
    283:   PetscCall(PCGetOperators(pc, NULL, &B));
    284:   {
    285:     MatNullSpace nullspace, sub_nullspace;
    286:     PetscCall(MatGetNullSpace(B, &nullspace));
    287:     if (nullspace) {
    288:       PetscCall(PetscInfo(pc, "PCTelescope: generating nullspace (CoarseDM)\n"));
    289:       PetscCall(PCTelescopeSubNullSpaceCreate_CoarseDM(pc, sred, nullspace, &sub_nullspace));

    291:       /* attach any user nullspace removal methods and contexts */
    292:       if (PCTelescope_isActiveRank(sred)) {
    293:         void *context = NULL;
    294:         if (nullspace->remove && !nullspace->rmctx) {
    295:           PetscCall(MatNullSpaceSetFunction(sub_nullspace, nullspace->remove, context));
    296:         } else if (nullspace->remove && nullspace->rmctx) {
    297:           char dmcoarse_method[PETSC_MAX_PATH_LEN];
    298:           PetscErrorCode (*fp_get_coarsedm_context)(DM, void **) = NULL;

    300:           PetscCall(PetscSNPrintf(dmcoarse_method, sizeof(dmcoarse_method), "PCTelescopeGetCoarseDMNullSpaceUserContext"));
    301:           PetscCall(PetscObjectQueryFunction((PetscObject)ctx->dm_coarse, dmcoarse_method, &fp_get_coarsedm_context));
    302:           PetscCheck(context, PETSC_COMM_SELF, PETSC_ERR_SUP, "Propagation of user null-space removal method with non-NULL context requires the coarse DM be composed with a function named \"%s\"", dmcoarse_method);
    303:           PetscCall(MatNullSpaceSetFunction(sub_nullspace, nullspace->remove, context));
    304:         }
    305:       }

    307:       if (PCTelescope_isActiveRank(sred)) {
    308:         PetscCall(MatSetNullSpace(sub_mat, sub_nullspace));
    309:         PetscCall(MatNullSpaceDestroy(&sub_nullspace));
    310:       }
    311:     }
    312:   }
    313:   {
    314:     MatNullSpace nearnullspace, sub_nearnullspace;
    315:     PetscCall(MatGetNearNullSpace(B, &nearnullspace));
    316:     if (nearnullspace) {
    317:       PetscCall(PetscInfo(pc, "PCTelescope: generating near nullspace (CoarseDM)\n"));
    318:       PetscCall(PCTelescopeSubNullSpaceCreate_CoarseDM(pc, sred, nearnullspace, &sub_nearnullspace));

    320:       /* attach any user nullspace removal methods and contexts */
    321:       if (PCTelescope_isActiveRank(sred)) {
    322:         void *context = NULL;
    323:         if (nearnullspace->remove && !nearnullspace->rmctx) {
    324:           PetscCall(MatNullSpaceSetFunction(sub_nearnullspace, nearnullspace->remove, context));
    325:         } else if (nearnullspace->remove && nearnullspace->rmctx) {
    326:           char dmcoarse_method[PETSC_MAX_PATH_LEN];
    327:           PetscErrorCode (*fp_get_coarsedm_context)(DM, void **) = NULL;

    329:           PetscCall(PetscSNPrintf(dmcoarse_method, sizeof(dmcoarse_method), "PCTelescopeGetCoarseDMNearNullSpaceUserContext"));
    330:           PetscCall(PetscObjectQueryFunction((PetscObject)ctx->dm_coarse, dmcoarse_method, &fp_get_coarsedm_context));
    331:           PetscCheck(context, PETSC_COMM_SELF, PETSC_ERR_SUP, "Propagation of user near null-space removal method with non-NULL context requires the coarse DM be composed with a function named \"%s\"", dmcoarse_method);
    332:           PetscCall(MatNullSpaceSetFunction(sub_nearnullspace, nearnullspace->remove, context));
    333:         }
    334:       }

    336:       if (PCTelescope_isActiveRank(sred)) {
    337:         PetscCall(MatSetNearNullSpace(sub_mat, sub_nearnullspace));
    338:         PetscCall(MatNullSpaceDestroy(&sub_nearnullspace));
    339:       }
    340:     }
    341:   }
    342:   PetscFunctionReturn(PETSC_SUCCESS);
    343: }

    345: PetscErrorCode PCReset_Telescope_CoarseDM(PC pc)
    346: {
    347:   PC_Telescope              sred = (PC_Telescope)pc->data;
    348:   PC_Telescope_CoarseDMCtx *ctx;

    350:   PetscFunctionBegin;
    351:   ctx              = (PC_Telescope_CoarseDMCtx *)sred->dm_ctx;
    352:   ctx->dm_fine     = NULL; /* since I did not increment the ref counter we set these to NULL */
    353:   ctx->dm_coarse   = NULL; /* since I did not increment the ref counter we set these to NULL */
    354:   ctx->permutation = NULL; /* this will be fetched from the dm so no need to call destroy */
    355:   PetscCall(VecDestroy(&ctx->xp));
    356:   ctx->fp_dm_field_scatter      = NULL;
    357:   ctx->fp_dm_state_scatter      = NULL;
    358:   ctx->dmksp_context_determined = NULL;
    359:   ctx->dmksp_context_user       = NULL;
    360:   PetscFunctionReturn(PETSC_SUCCESS);
    361: }

    363: PetscErrorCode PCApplyRichardson_Telescope_CoarseDM(PC pc, Vec x, Vec y, Vec w, PetscReal rtol, PetscReal abstol, PetscReal dtol, PetscInt its, PetscBool zeroguess, PetscInt *outits, PCRichardsonConvergedReason *reason)
    364: {
    365:   PC_Telescope              sred                     = (PC_Telescope)pc->data;
    366:   Vec                       yred                     = NULL;
    367:   PetscBool                 default_init_guess_value = PETSC_FALSE;
    368:   PC_Telescope_CoarseDMCtx *ctx;

    370:   PetscFunctionBegin;
    371:   ctx  = (PC_Telescope_CoarseDMCtx *)sred->dm_ctx;
    372:   yred = sred->yred;

    374:   PetscCheck(its <= 1, PetscObjectComm((PetscObject)pc), PETSC_ERR_SUP, "PCApplyRichardson_Telescope_CoarseDM only supports max_it = 1");
    375:   *reason = (PCRichardsonConvergedReason)0;

    377:   if (!zeroguess) {
    378:     PetscCall(PetscInfo(pc, "PCTelescopeCoarseDM: Scattering y for non-zero-initial guess\n"));

    380:     PetscCall(ctx->fp_dm_field_scatter(ctx->dm_fine, y, SCATTER_FORWARD, ctx->dm_coarse, yred));
    381:   }

    383:   if (PCTelescope_isActiveRank(sred)) {
    384:     PetscCall(KSPGetInitialGuessNonzero(sred->ksp, &default_init_guess_value));
    385:     if (!zeroguess) PetscCall(KSPSetInitialGuessNonzero(sred->ksp, PETSC_TRUE));
    386:   }

    388:   PetscCall(PCApply_Telescope_CoarseDM(pc, x, y));

    390:   if (PCTelescope_isActiveRank(sred)) PetscCall(KSPSetInitialGuessNonzero(sred->ksp, default_init_guess_value));

    392:   if (!*reason) *reason = PCRICHARDSON_CONVERGED_ITS;
    393:   *outits = 1;
    394:   PetscFunctionReturn(PETSC_SUCCESS);
    395: }