Actual source code: mg.c
petsc-3.13.6 2020-09-29
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      2: /*
      3:     Defines the multigrid preconditioner interface.
      4: */
      5:  #include <petsc/private/pcmgimpl.h>
      6:  #include <petscdm.h>
      7: PETSC_INTERN PetscErrorCode PCPreSolveChangeRHS(PC,PetscBool*);

      9: PetscErrorCode PCMGMCycle_Private(PC pc,PC_MG_Levels **mglevelsin,PCRichardsonConvergedReason *reason)
     10: {
     11:   PC_MG          *mg = (PC_MG*)pc->data;
     12:   PC_MG_Levels   *mgc,*mglevels = *mglevelsin;
     14:   PetscInt       cycles = (mglevels->level == 1) ? 1 : (PetscInt) mglevels->cycles;

     17:   if (mglevels->eventsmoothsolve) {PetscLogEventBegin(mglevels->eventsmoothsolve,0,0,0,0);}
     18:   KSPSolve(mglevels->smoothd,mglevels->b,mglevels->x);  /* pre-smooth */
     19:   KSPCheckSolve(mglevels->smoothd,pc,mglevels->x);
     20:   if (mglevels->eventsmoothsolve) {PetscLogEventEnd(mglevels->eventsmoothsolve,0,0,0,0);}
     21:   if (mglevels->level) {  /* not the coarsest grid */
     22:     if (mglevels->eventresidual) {PetscLogEventBegin(mglevels->eventresidual,0,0,0,0);}
     23:     (*mglevels->residual)(mglevels->A,mglevels->b,mglevels->x,mglevels->r);
     24:     if (mglevels->eventresidual) {PetscLogEventEnd(mglevels->eventresidual,0,0,0,0);}

     26:     /* if on finest level and have convergence criteria set */
     27:     if (mglevels->level == mglevels->levels-1 && mg->ttol && reason) {
     28:       PetscReal rnorm;
     29:       VecNorm(mglevels->r,NORM_2,&rnorm);
     30:       if (rnorm <= mg->ttol) {
     31:         if (rnorm < mg->abstol) {
     32:           *reason = PCRICHARDSON_CONVERGED_ATOL;
     33:           PetscInfo2(pc,"Linear solver has converged. Residual norm %g is less than absolute tolerance %g\n",(double)rnorm,(double)mg->abstol);
     34:         } else {
     35:           *reason = PCRICHARDSON_CONVERGED_RTOL;
     36:           PetscInfo2(pc,"Linear solver has converged. Residual norm %g is less than relative tolerance times initial residual norm %g\n",(double)rnorm,(double)mg->ttol);
     37:         }
     38:         return(0);
     39:       }
     40:     }

     42:     mgc = *(mglevelsin - 1);
     43:     if (mglevels->eventinterprestrict) {PetscLogEventBegin(mglevels->eventinterprestrict,0,0,0,0);}
     44:     MatRestrict(mglevels->restrct,mglevels->r,mgc->b);
     45:     if (mglevels->eventinterprestrict) {PetscLogEventEnd(mglevels->eventinterprestrict,0,0,0,0);}
     46:     VecSet(mgc->x,0.0);
     47:     while (cycles--) {
     48:       PCMGMCycle_Private(pc,mglevelsin-1,reason);
     49:     }
     50:     if (mglevels->eventinterprestrict) {PetscLogEventBegin(mglevels->eventinterprestrict,0,0,0,0);}
     51:     MatInterpolateAdd(mglevels->interpolate,mgc->x,mglevels->x,mglevels->x);
     52:     if (mglevels->eventinterprestrict) {PetscLogEventEnd(mglevels->eventinterprestrict,0,0,0,0);}
     53:     if (mglevels->eventsmoothsolve) {PetscLogEventBegin(mglevels->eventsmoothsolve,0,0,0,0);}
     54:     KSPSolve(mglevels->smoothu,mglevels->b,mglevels->x);    /* post smooth */
     55:     KSPCheckSolve(mglevels->smoothu,pc,mglevels->x);
     56:     if (mglevels->eventsmoothsolve) {PetscLogEventEnd(mglevels->eventsmoothsolve,0,0,0,0);}
     57:   }
     58:   return(0);
     59: }

     61: static PetscErrorCode PCApplyRichardson_MG(PC pc,Vec b,Vec x,Vec w,PetscReal rtol,PetscReal abstol, PetscReal dtol,PetscInt its,PetscBool zeroguess,PetscInt *outits,PCRichardsonConvergedReason *reason)
     62: {
     63:   PC_MG          *mg        = (PC_MG*)pc->data;
     64:   PC_MG_Levels   **mglevels = mg->levels;
     66:   PC             tpc;
     67:   PetscBool      changeu,changed;
     68:   PetscInt       levels = mglevels[0]->levels,i;

     71:   /* When the DM is supplying the matrix then it will not exist until here */
     72:   for (i=0; i<levels; i++) {
     73:     if (!mglevels[i]->A) {
     74:       KSPGetOperators(mglevels[i]->smoothu,&mglevels[i]->A,NULL);
     75:       PetscObjectReference((PetscObject)mglevels[i]->A);
     76:     }
     77:   }

     79:   KSPGetPC(mglevels[levels-1]->smoothd,&tpc);
     80:   PCPreSolveChangeRHS(tpc,&changed);
     81:   KSPGetPC(mglevels[levels-1]->smoothu,&tpc);
     82:   PCPreSolveChangeRHS(tpc,&changeu);
     83:   if (!changed && !changeu) {
     84:     VecDestroy(&mglevels[levels-1]->b);
     85:     mglevels[levels-1]->b = b;
     86:   } else { /* if the smoother changes the rhs during PreSolve, we cannot use the input vector */
     87:     if (!mglevels[levels-1]->b) {
     88:       Vec *vec;

     90:       KSPCreateVecs(mglevels[levels-1]->smoothd,1,&vec,0,NULL);
     91:       mglevels[levels-1]->b = *vec;
     92:       PetscFree(vec);
     93:     }
     94:     VecCopy(b,mglevels[levels-1]->b);
     95:   }
     96:   mglevels[levels-1]->x = x;

     98:   mg->rtol   = rtol;
     99:   mg->abstol = abstol;
    100:   mg->dtol   = dtol;
    101:   if (rtol) {
    102:     /* compute initial residual norm for relative convergence test */
    103:     PetscReal rnorm;
    104:     if (zeroguess) {
    105:       VecNorm(b,NORM_2,&rnorm);
    106:     } else {
    107:       (*mglevels[levels-1]->residual)(mglevels[levels-1]->A,b,x,w);
    108:       VecNorm(w,NORM_2,&rnorm);
    109:     }
    110:     mg->ttol = PetscMax(rtol*rnorm,abstol);
    111:   } else if (abstol) mg->ttol = abstol;
    112:   else mg->ttol = 0.0;

    114:   /* since smoother is applied to full system, not just residual we need to make sure that smoothers don't
    115:      stop prematurely due to small residual */
    116:   for (i=1; i<levels; i++) {
    117:     KSPSetTolerances(mglevels[i]->smoothu,0,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);
    118:     if (mglevels[i]->smoothu != mglevels[i]->smoothd) {
    119:       /* For Richardson the initial guess is nonzero since it is solving in each cycle the original system not just applying as a preconditioner */
    120:       KSPSetInitialGuessNonzero(mglevels[i]->smoothd,PETSC_TRUE);
    121:       KSPSetTolerances(mglevels[i]->smoothd,0,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);
    122:     }
    123:   }

    125:   *reason = (PCRichardsonConvergedReason)0;
    126:   for (i=0; i<its; i++) {
    127:     PCMGMCycle_Private(pc,mglevels+levels-1,reason);
    128:     if (*reason) break;
    129:   }
    130:   if (!*reason) *reason = PCRICHARDSON_CONVERGED_ITS;
    131:   *outits = i;
    132:   if (!changed && !changeu) mglevels[levels-1]->b = NULL;
    133:   return(0);
    134: }

    136: PetscErrorCode PCReset_MG(PC pc)
    137: {
    138:   PC_MG          *mg        = (PC_MG*)pc->data;
    139:   PC_MG_Levels   **mglevels = mg->levels;
    141:   PetscInt       i,n;

    144:   if (mglevels) {
    145:     n = mglevels[0]->levels;
    146:     for (i=0; i<n-1; i++) {
    147:       VecDestroy(&mglevels[i+1]->r);
    148:       VecDestroy(&mglevels[i]->b);
    149:       VecDestroy(&mglevels[i]->x);
    150:       MatDestroy(&mglevels[i+1]->restrct);
    151:       MatDestroy(&mglevels[i+1]->interpolate);
    152:       MatDestroy(&mglevels[i+1]->inject);
    153:       VecDestroy(&mglevels[i+1]->rscale);
    154:     }
    155:     /* this is not null only if the smoother on the finest level
    156:        changes the rhs during PreSolve */
    157:     VecDestroy(&mglevels[n-1]->b);

    159:     for (i=0; i<n; i++) {
    160:       MatDestroy(&mglevels[i]->A);
    161:       if (mglevels[i]->smoothd != mglevels[i]->smoothu) {
    162:         KSPReset(mglevels[i]->smoothd);
    163:       }
    164:       KSPReset(mglevels[i]->smoothu);
    165:     }
    166:   }
    167:   return(0);
    168: }

    170: PetscErrorCode PCMGSetLevels_MG(PC pc,PetscInt levels,MPI_Comm *comms)
    171: {
    173:   PC_MG          *mg        = (PC_MG*)pc->data;
    174:   MPI_Comm       comm;
    175:   PC_MG_Levels   **mglevels = mg->levels;
    176:   PCMGType       mgtype     = mg->am;
    177:   PetscInt       mgctype    = (PetscInt) PC_MG_CYCLE_V;
    178:   PetscInt       i;
    179:   PetscMPIInt    size;
    180:   const char     *prefix;
    181:   PC             ipc;
    182:   PetscInt       n;

    187:   if (mg->nlevels == levels) return(0);
    188:   PetscObjectGetComm((PetscObject)pc,&comm);
    189:   if (mglevels) {
    190:     mgctype = mglevels[0]->cycles;
    191:     /* changing the number of levels so free up the previous stuff */
    192:     PCReset_MG(pc);
    193:     n    = mglevels[0]->levels;
    194:     for (i=0; i<n; i++) {
    195:       if (mglevels[i]->smoothd != mglevels[i]->smoothu) {
    196:         KSPDestroy(&mglevels[i]->smoothd);
    197:       }
    198:       KSPDestroy(&mglevels[i]->smoothu);
    199:       PetscFree(mglevels[i]);
    200:     }
    201:     PetscFree(mg->levels);
    202:   }

    204:   mg->nlevels = levels;

    206:   PetscMalloc1(levels,&mglevels);
    207:   PetscLogObjectMemory((PetscObject)pc,levels*(sizeof(PC_MG*)));

    209:   PCGetOptionsPrefix(pc,&prefix);

    211:   mg->stageApply = 0;
    212:   for (i=0; i<levels; i++) {
    213:     PetscNewLog(pc,&mglevels[i]);

    215:     mglevels[i]->level               = i;
    216:     mglevels[i]->levels              = levels;
    217:     mglevels[i]->cycles              = mgctype;
    218:     mg->default_smoothu              = 2;
    219:     mg->default_smoothd              = 2;
    220:     mglevels[i]->eventsmoothsetup    = 0;
    221:     mglevels[i]->eventsmoothsolve    = 0;
    222:     mglevels[i]->eventresidual       = 0;
    223:     mglevels[i]->eventinterprestrict = 0;

    225:     if (comms) comm = comms[i];
    226:     KSPCreate(comm,&mglevels[i]->smoothd);
    227:     KSPSetErrorIfNotConverged(mglevels[i]->smoothd,pc->erroriffailure);
    228:     PetscObjectIncrementTabLevel((PetscObject)mglevels[i]->smoothd,(PetscObject)pc,levels-i);
    229:     KSPSetOptionsPrefix(mglevels[i]->smoothd,prefix);
    230:     PetscObjectComposedDataSetInt((PetscObject) mglevels[i]->smoothd, PetscMGLevelId, mglevels[i]->level);
    231:     if (i || levels == 1) {
    232:       char tprefix[128];

    234:       KSPSetType(mglevels[i]->smoothd,KSPCHEBYSHEV);
    235:       KSPSetConvergenceTest(mglevels[i]->smoothd,KSPConvergedSkip,NULL,NULL);
    236:       KSPSetNormType(mglevels[i]->smoothd,KSP_NORM_NONE);
    237:       KSPGetPC(mglevels[i]->smoothd,&ipc);
    238:       PCSetType(ipc,PCSOR);
    239:       KSPSetTolerances(mglevels[i]->smoothd,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT, mg->default_smoothd);

    241:       sprintf(tprefix,"mg_levels_%d_",(int)i);
    242:       KSPAppendOptionsPrefix(mglevels[i]->smoothd,tprefix);
    243:     } else {
    244:       KSPAppendOptionsPrefix(mglevels[0]->smoothd,"mg_coarse_");

    246:       /* coarse solve is (redundant) LU by default; set shifttype NONZERO to avoid annoying zero-pivot in LU preconditioner */
    247:       KSPSetType(mglevels[0]->smoothd,KSPPREONLY);
    248:       KSPGetPC(mglevels[0]->smoothd,&ipc);
    249:       MPI_Comm_size(comm,&size);
    250:       if (size > 1) {
    251:         PCSetType(ipc,PCREDUNDANT);
    252:       } else {
    253:         PCSetType(ipc,PCLU);
    254:       }
    255:       PCFactorSetShiftType(ipc,MAT_SHIFT_INBLOCKS);
    256:     }
    257:     PetscLogObjectParent((PetscObject)pc,(PetscObject)mglevels[i]->smoothd);

    259:     mglevels[i]->smoothu = mglevels[i]->smoothd;
    260:     mg->rtol             = 0.0;
    261:     mg->abstol           = 0.0;
    262:     mg->dtol             = 0.0;
    263:     mg->ttol             = 0.0;
    264:     mg->cyclesperpcapply = 1;
    265:   }
    266:   mg->levels = mglevels;
    267:   PCMGSetType(pc,mgtype);
    268:   return(0);
    269: }

    271: /*@C
    272:    PCMGSetLevels - Sets the number of levels to use with MG.
    273:    Must be called before any other MG routine.

    275:    Logically Collective on PC

    277:    Input Parameters:
    278: +  pc - the preconditioner context
    279: .  levels - the number of levels
    280: -  comms - optional communicators for each level; this is to allow solving the coarser problems
    281:            on smaller sets of processors.

    283:    Level: intermediate

    285:    Notes:
    286:      If the number of levels is one then the multigrid uses the -mg_levels prefix
    287:   for setting the level options rather than the -mg_coarse prefix.

    289: .seealso: PCMGSetType(), PCMGGetLevels()
    290: @*/
    291: PetscErrorCode PCMGSetLevels(PC pc,PetscInt levels,MPI_Comm *comms)
    292: {

    298:   PetscTryMethod(pc,"PCMGSetLevels_C",(PC,PetscInt,MPI_Comm*),(pc,levels,comms));
    299:   return(0);
    300: }

    303: PetscErrorCode PCDestroy_MG(PC pc)
    304: {
    306:   PC_MG          *mg        = (PC_MG*)pc->data;
    307:   PC_MG_Levels   **mglevels = mg->levels;
    308:   PetscInt       i,n;

    311:   PCReset_MG(pc);
    312:   if (mglevels) {
    313:     n = mglevels[0]->levels;
    314:     for (i=0; i<n; i++) {
    315:       if (mglevels[i]->smoothd != mglevels[i]->smoothu) {
    316:         KSPDestroy(&mglevels[i]->smoothd);
    317:       }
    318:       KSPDestroy(&mglevels[i]->smoothu);
    319:       PetscFree(mglevels[i]);
    320:     }
    321:     PetscFree(mg->levels);
    322:   }
    323:   PetscFree(pc->data);
    324:   PetscObjectComposeFunction((PetscObject)pc,"PCGetInterpolations_C",NULL);
    325:   PetscObjectComposeFunction((PetscObject)pc,"PCGetCoarseOperators_C",NULL);
    326:   return(0);
    327: }

    331: extern PetscErrorCode PCMGACycle_Private(PC,PC_MG_Levels**);
    332: extern PetscErrorCode PCMGFCycle_Private(PC,PC_MG_Levels**);
    333: extern PetscErrorCode PCMGKCycle_Private(PC,PC_MG_Levels**);

    335: /*
    336:    PCApply_MG - Runs either an additive, multiplicative, Kaskadic
    337:              or full cycle of multigrid.

    339:   Note:
    340:   A simple wrapper which calls PCMGMCycle(),PCMGACycle(), or PCMGFCycle().
    341: */
    342: static PetscErrorCode PCApply_MG(PC pc,Vec b,Vec x)
    343: {
    344:   PC_MG          *mg        = (PC_MG*)pc->data;
    345:   PC_MG_Levels   **mglevels = mg->levels;
    347:   PC             tpc;
    348:   PetscInt       levels = mglevels[0]->levels,i;
    349:   PetscBool      changeu,changed;

    352:   if (mg->stageApply) {PetscLogStagePush(mg->stageApply);}
    353:   /* When the DM is supplying the matrix then it will not exist until here */
    354:   for (i=0; i<levels; i++) {
    355:     if (!mglevels[i]->A) {
    356:       KSPGetOperators(mglevels[i]->smoothu,&mglevels[i]->A,NULL);
    357:       PetscObjectReference((PetscObject)mglevels[i]->A);
    358:     }
    359:   }

    361:   KSPGetPC(mglevels[levels-1]->smoothd,&tpc);
    362:   PCPreSolveChangeRHS(tpc,&changed);
    363:   KSPGetPC(mglevels[levels-1]->smoothu,&tpc);
    364:   PCPreSolveChangeRHS(tpc,&changeu);
    365:   if (!changeu && !changed) {
    366:     VecDestroy(&mglevels[levels-1]->b);
    367:     mglevels[levels-1]->b = b;
    368:   } else { /* if the smoother changes the rhs during PreSolve, we cannot use the input vector */
    369:     if (!mglevels[levels-1]->b) {
    370:       Vec *vec;

    372:       KSPCreateVecs(mglevels[levels-1]->smoothd,1,&vec,0,NULL);
    373:       mglevels[levels-1]->b = *vec;
    374:       PetscFree(vec);
    375:     }
    376:     VecCopy(b,mglevels[levels-1]->b);
    377:   }
    378:   mglevels[levels-1]->x = x;

    380:   if (mg->am == PC_MG_MULTIPLICATIVE) {
    381:     VecSet(x,0.0);
    382:     for (i=0; i<mg->cyclesperpcapply; i++) {
    383:       PCMGMCycle_Private(pc,mglevels+levels-1,NULL);
    384:     }
    385:   } else if (mg->am == PC_MG_ADDITIVE) {
    386:     PCMGACycle_Private(pc,mglevels);
    387:   } else if (mg->am == PC_MG_KASKADE) {
    388:     PCMGKCycle_Private(pc,mglevels);
    389:   } else {
    390:     PCMGFCycle_Private(pc,mglevels);
    391:   }
    392:   if (mg->stageApply) {PetscLogStagePop();}
    393:   if (!changeu && !changed) mglevels[levels-1]->b = NULL;
    394:   return(0);
    395: }

    398: PetscErrorCode PCSetFromOptions_MG(PetscOptionItems *PetscOptionsObject,PC pc)
    399: {
    400:   PetscErrorCode   ierr;
    401:   PetscInt         levels,cycles;
    402:   PetscBool        flg;
    403:   PC_MG            *mg = (PC_MG*)pc->data;
    404:   PC_MG_Levels     **mglevels;
    405:   PCMGType         mgtype;
    406:   PCMGCycleType    mgctype;
    407:   PCMGGalerkinType gtype;

    410:   levels = PetscMax(mg->nlevels,1);
    411:   PetscOptionsHead(PetscOptionsObject,"Multigrid options");
    412:   PetscOptionsInt("-pc_mg_levels","Number of Levels","PCMGSetLevels",levels,&levels,&flg);
    413:   if (!flg && !mg->levels && pc->dm) {
    414:     DMGetRefineLevel(pc->dm,&levels);
    415:     levels++;
    416:     mg->usedmfornumberoflevels = PETSC_TRUE;
    417:   }
    418:   PCMGSetLevels(pc,levels,NULL);
    419:   mglevels = mg->levels;

    421:   mgctype = (PCMGCycleType) mglevels[0]->cycles;
    422:   PetscOptionsEnum("-pc_mg_cycle_type","V cycle or for W-cycle","PCMGSetCycleType",PCMGCycleTypes,(PetscEnum)mgctype,(PetscEnum*)&mgctype,&flg);
    423:   if (flg) {
    424:     PCMGSetCycleType(pc,mgctype);
    425:   }
    426:   gtype = mg->galerkin;
    427:   PetscOptionsEnum("-pc_mg_galerkin","Use Galerkin process to compute coarser operators","PCMGSetGalerkin",PCMGGalerkinTypes,(PetscEnum)gtype,(PetscEnum*)&gtype,&flg);
    428:   if (flg) {
    429:     PCMGSetGalerkin(pc,gtype);
    430:   }
    431:   flg = PETSC_FALSE;
    432:   PetscOptionsBool("-pc_mg_distinct_smoothup","Create separate smoothup KSP and append the prefix _up","PCMGSetDistinctSmoothUp",PETSC_FALSE,&flg,NULL);
    433:   if (flg) {
    434:     PCMGSetDistinctSmoothUp(pc);
    435:   }
    436:   mgtype = mg->am;
    437:   PetscOptionsEnum("-pc_mg_type","Multigrid type","PCMGSetType",PCMGTypes,(PetscEnum)mgtype,(PetscEnum*)&mgtype,&flg);
    438:   if (flg) {
    439:     PCMGSetType(pc,mgtype);
    440:   }
    441:   if (mg->am == PC_MG_MULTIPLICATIVE) {
    442:     PetscOptionsInt("-pc_mg_multiplicative_cycles","Number of cycles for each preconditioner step","PCMGMultiplicativeSetCycles",mg->cyclesperpcapply,&cycles,&flg);
    443:     if (flg) {
    444:       PCMGMultiplicativeSetCycles(pc,cycles);
    445:     }
    446:   }
    447:   flg  = PETSC_FALSE;
    448:   PetscOptionsBool("-pc_mg_log","Log times for each multigrid level","None",flg,&flg,NULL);
    449:   if (flg) {
    450:     PetscInt i;
    451:     char     eventname[128];

    453:     levels = mglevels[0]->levels;
    454:     for (i=0; i<levels; i++) {
    455:       sprintf(eventname,"MGSetup Level %d",(int)i);
    456:       PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventsmoothsetup);
    457:       sprintf(eventname,"MGSmooth Level %d",(int)i);
    458:       PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventsmoothsolve);
    459:       if (i) {
    460:         sprintf(eventname,"MGResid Level %d",(int)i);
    461:         PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventresidual);
    462:         sprintf(eventname,"MGInterp Level %d",(int)i);
    463:         PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventinterprestrict);
    464:       }
    465:     }

    467: #if defined(PETSC_USE_LOG)
    468:     {
    469:       const char    *sname = "MG Apply";
    470:       PetscStageLog stageLog;
    471:       PetscInt      st;

    473:       PetscLogGetStageLog(&stageLog);
    474:       for (st = 0; st < stageLog->numStages; ++st) {
    475:         PetscBool same;

    477:         PetscStrcmp(stageLog->stageInfo[st].name, sname, &same);
    478:         if (same) mg->stageApply = st;
    479:       }
    480:       if (!mg->stageApply) {
    481:         PetscLogStageRegister(sname, &mg->stageApply);
    482:       }
    483:     }
    484: #endif
    485:   }
    486:   PetscOptionsTail();
    487:   return(0);
    488: }

    490: const char *const PCMGTypes[] = {"MULTIPLICATIVE","ADDITIVE","FULL","KASKADE","PCMGType","PC_MG",0};
    491: const char *const PCMGCycleTypes[] = {"invalid","v","w","PCMGCycleType","PC_MG_CYCLE",0};
    492: const char *const PCMGGalerkinTypes[] = {"both","pmat","mat","none","external","PCMGGalerkinType","PC_MG_GALERKIN",0};

    494:  #include <petscdraw.h>
    495: PetscErrorCode PCView_MG(PC pc,PetscViewer viewer)
    496: {
    497:   PC_MG          *mg        = (PC_MG*)pc->data;
    498:   PC_MG_Levels   **mglevels = mg->levels;
    500:   PetscInt       levels = mglevels ? mglevels[0]->levels : 0,i;
    501:   PetscBool      iascii,isbinary,isdraw;

    504:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
    505:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);
    506:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERDRAW,&isdraw);
    507:   if (iascii) {
    508:     const char *cyclename = levels ? (mglevels[0]->cycles == PC_MG_CYCLE_V ? "v" : "w") : "unknown";
    509:     PetscViewerASCIIPrintf(viewer,"  type is %s, levels=%D cycles=%s\n", PCMGTypes[mg->am],levels,cyclename);
    510:     if (mg->am == PC_MG_MULTIPLICATIVE) {
    511:       PetscViewerASCIIPrintf(viewer,"    Cycles per PCApply=%d\n",mg->cyclesperpcapply);
    512:     }
    513:     if (mg->galerkin == PC_MG_GALERKIN_BOTH) {
    514:       PetscViewerASCIIPrintf(viewer,"    Using Galerkin computed coarse grid matrices\n");
    515:     } else if (mg->galerkin == PC_MG_GALERKIN_PMAT) {
    516:       PetscViewerASCIIPrintf(viewer,"    Using Galerkin computed coarse grid matrices for pmat\n");
    517:     } else if (mg->galerkin == PC_MG_GALERKIN_MAT) {
    518:       PetscViewerASCIIPrintf(viewer,"    Using Galerkin computed coarse grid matrices for mat\n");
    519:     } else if (mg->galerkin == PC_MG_GALERKIN_EXTERNAL) {
    520:       PetscViewerASCIIPrintf(viewer,"    Using externally compute Galerkin coarse grid matrices\n");
    521:     } else {
    522:       PetscViewerASCIIPrintf(viewer,"    Not using Galerkin computed coarse grid matrices\n");
    523:     }
    524:     if (mg->view){
    525:       (*mg->view)(pc,viewer);
    526:     }
    527:     for (i=0; i<levels; i++) {
    528:       if (!i) {
    529:         PetscViewerASCIIPrintf(viewer,"Coarse grid solver -- level -------------------------------\n",i);
    530:       } else {
    531:         PetscViewerASCIIPrintf(viewer,"Down solver (pre-smoother) on level %D -------------------------------\n",i);
    532:       }
    533:       PetscViewerASCIIPushTab(viewer);
    534:       KSPView(mglevels[i]->smoothd,viewer);
    535:       PetscViewerASCIIPopTab(viewer);
    536:       if (i && mglevels[i]->smoothd == mglevels[i]->smoothu) {
    537:         PetscViewerASCIIPrintf(viewer,"Up solver (post-smoother) same as down solver (pre-smoother)\n");
    538:       } else if (i) {
    539:         PetscViewerASCIIPrintf(viewer,"Up solver (post-smoother) on level %D -------------------------------\n",i);
    540:         PetscViewerASCIIPushTab(viewer);
    541:         KSPView(mglevels[i]->smoothu,viewer);
    542:         PetscViewerASCIIPopTab(viewer);
    543:       }
    544:     }
    545:   } else if (isbinary) {
    546:     for (i=levels-1; i>=0; i--) {
    547:       KSPView(mglevels[i]->smoothd,viewer);
    548:       if (i && mglevels[i]->smoothd != mglevels[i]->smoothu) {
    549:         KSPView(mglevels[i]->smoothu,viewer);
    550:       }
    551:     }
    552:   } else if (isdraw) {
    553:     PetscDraw draw;
    554:     PetscReal x,w,y,bottom,th;
    555:     PetscViewerDrawGetDraw(viewer,0,&draw);
    556:     PetscDrawGetCurrentPoint(draw,&x,&y);
    557:     PetscDrawStringGetSize(draw,NULL,&th);
    558:     bottom = y - th;
    559:     for (i=levels-1; i>=0; i--) {
    560:       if (!mglevels[i]->smoothu || (mglevels[i]->smoothu == mglevels[i]->smoothd)) {
    561:         PetscDrawPushCurrentPoint(draw,x,bottom);
    562:         KSPView(mglevels[i]->smoothd,viewer);
    563:         PetscDrawPopCurrentPoint(draw);
    564:       } else {
    565:         w    = 0.5*PetscMin(1.0-x,x);
    566:         PetscDrawPushCurrentPoint(draw,x+w,bottom);
    567:         KSPView(mglevels[i]->smoothd,viewer);
    568:         PetscDrawPopCurrentPoint(draw);
    569:         PetscDrawPushCurrentPoint(draw,x-w,bottom);
    570:         KSPView(mglevels[i]->smoothu,viewer);
    571:         PetscDrawPopCurrentPoint(draw);
    572:       }
    573:       PetscDrawGetBoundingBox(draw,NULL,&bottom,NULL,NULL);
    574:       bottom -= th;
    575:     }
    576:   }
    577:   return(0);
    578: }

    580:  #include <petsc/private/dmimpl.h>
    581:  #include <petsc/private/kspimpl.h>

    583: /*
    584:     Calls setup for the KSP on each level
    585: */
    586: PetscErrorCode PCSetUp_MG(PC pc)
    587: {
    588:   PC_MG          *mg        = (PC_MG*)pc->data;
    589:   PC_MG_Levels   **mglevels = mg->levels;
    591:   PetscInt       i,n;
    592:   PC             cpc;
    593:   PetscBool      dump = PETSC_FALSE,opsset,use_amat,missinginterpolate = PETSC_FALSE;
    594:   Mat            dA,dB;
    595:   Vec            tvec;
    596:   DM             *dms;
    597:   PetscViewer    viewer = 0;
    598:   PetscBool      dAeqdB = PETSC_FALSE, needRestricts = PETSC_FALSE;

    601:   if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONGSTATE,"Must set MG levels with PCMGSetLevels() before setting up");
    602:   n = mglevels[0]->levels;
    603:   /* FIX: Move this to PCSetFromOptions_MG? */
    604:   if (mg->usedmfornumberoflevels) {
    605:     PetscInt levels;
    606:     DMGetRefineLevel(pc->dm,&levels);
    607:     levels++;
    608:     if (levels > n) { /* the problem is now being solved on a finer grid */
    609:       PCMGSetLevels(pc,levels,NULL);
    610:       n        = levels;
    611:       PCSetFromOptions(pc); /* it is bad to call this here, but otherwise will never be called for the new hierarchy */
    612:       mglevels = mg->levels;
    613:     }
    614:   }
    615:   KSPGetPC(mglevels[0]->smoothd,&cpc);

    618:   /* If user did not provide fine grid operators OR operator was not updated since last global KSPSetOperators() */
    619:   /* so use those from global PC */
    620:   /* Is this what we always want? What if user wants to keep old one? */
    621:   KSPGetOperatorsSet(mglevels[n-1]->smoothd,NULL,&opsset);
    622:   if (opsset) {
    623:     Mat mmat;
    624:     KSPGetOperators(mglevels[n-1]->smoothd,NULL,&mmat);
    625:     if (mmat == pc->pmat) opsset = PETSC_FALSE;
    626:   }

    628:   if (!opsset) {
    629:     PCGetUseAmat(pc,&use_amat);
    630:     if (use_amat) {
    631:       PetscInfo(pc,"Using outer operators to define finest grid operator \n  because PCMGGetSmoother(pc,nlevels-1,&ksp);KSPSetOperators(ksp,...); was not called.\n");
    632:       KSPSetOperators(mglevels[n-1]->smoothd,pc->mat,pc->pmat);
    633:     } else {
    634:       PetscInfo(pc,"Using matrix (pmat) operators to define finest grid operator \n  because PCMGGetSmoother(pc,nlevels-1,&ksp);KSPSetOperators(ksp,...); was not called.\n");
    635:       KSPSetOperators(mglevels[n-1]->smoothd,pc->pmat,pc->pmat);
    636:     }
    637:   }

    639:   for (i=n-1; i>0; i--) {
    640:     if (!(mglevels[i]->interpolate || mglevels[i]->restrct)) {
    641:       missinginterpolate = PETSC_TRUE;
    642:       continue;
    643:     }
    644:   }

    646:   KSPGetOperators(mglevels[n-1]->smoothd,&dA,&dB);
    647:   if (dA == dB) dAeqdB = PETSC_TRUE;
    648:   if ((mg->galerkin == PC_MG_GALERKIN_NONE) || (((mg->galerkin == PC_MG_GALERKIN_PMAT) || (mg->galerkin == PC_MG_GALERKIN_MAT)) && !dAeqdB)) {
    649:     needRestricts = PETSC_TRUE;  /* user must compute either mat, pmat, or both so must restrict x to coarser levels */
    650:   }

    653:   /*
    654:    Skipping if user has provided all interpolation/restriction needed (since DM might not be able to produce them (when coming from SNES/TS)
    655:    Skipping for galerkin==2 (externally managed hierarchy such as ML and GAMG). Cleaner logic here would be great. Wrap ML/GAMG as DMs?
    656:   */
    657:   if (missinginterpolate && pc->dm && mg->galerkin != PC_MG_GALERKIN_EXTERNAL && !pc->setupcalled) {
    658:         /* construct the interpolation from the DMs */
    659:     Mat p;
    660:     Vec rscale;
    661:     PetscMalloc1(n,&dms);
    662:     dms[n-1] = pc->dm;
    663:     /* Separately create them so we do not get DMKSP interference between levels */
    664:     for (i=n-2; i>-1; i--) {DMCoarsen(dms[i+1],MPI_COMM_NULL,&dms[i]);}
    665:         /*
    666:            Force the mat type of coarse level operator to be AIJ because usually we want to use LU for coarse level.
    667:            Notice that it can be overwritten by -mat_type because KSPSetUp() reads command line options.
    668:            But it is safe to use -dm_mat_type.

    670:            The mat type should not be hardcoded like this, we need to find a better way.
    671:     DMSetMatType(dms[0],MATAIJ);
    672:     */
    673:     for (i=n-2; i>-1; i--) {
    674:       DMKSP     kdm;
    675:       PetscBool dmhasrestrict, dmhasinject;
    676:       KSPSetDM(mglevels[i]->smoothd,dms[i]);
    677:       if (!needRestricts) {KSPSetDMActive(mglevels[i]->smoothd,PETSC_FALSE);}
    678:       if (mglevels[i]->smoothd != mglevels[i]->smoothu) {
    679:         KSPSetDM(mglevels[i]->smoothu,dms[i]);
    680:         if (!needRestricts) {KSPSetDMActive(mglevels[i]->smoothu,PETSC_FALSE);}
    681:       }
    682:       DMGetDMKSPWrite(dms[i],&kdm);
    683:       /* Ugly hack so that the next KSPSetUp() will use the RHS that we set. A better fix is to change dmActive to take
    684:        * a bitwise OR of computing the matrix, RHS, and initial iterate. */
    685:       kdm->ops->computerhs = NULL;
    686:       kdm->rhsctx          = NULL;
    687:       if (!mglevels[i+1]->interpolate) {
    688:         DMCreateInterpolation(dms[i],dms[i+1],&p,&rscale);
    689:         PCMGSetInterpolation(pc,i+1,p);
    690:         if (rscale) {PCMGSetRScale(pc,i+1,rscale);}
    691:         VecDestroy(&rscale);
    692:         MatDestroy(&p);
    693:       }
    694:       DMHasCreateRestriction(dms[i],&dmhasrestrict);
    695:       if (dmhasrestrict && !mglevels[i+1]->restrct){
    696:         DMCreateRestriction(dms[i],dms[i+1],&p);
    697:         PCMGSetRestriction(pc,i+1,p);
    698:         MatDestroy(&p);
    699:       }
    700:       DMHasCreateInjection(dms[i],&dmhasinject);
    701:       if (dmhasinject && !mglevels[i+1]->inject){
    702:         DMCreateInjection(dms[i],dms[i+1],&p);
    703:         PCMGSetInjection(pc,i+1,p);
    704:         MatDestroy(&p);
    705:       }
    706:     }

    708:     for (i=n-2; i>-1; i--) {DMDestroy(&dms[i]);}
    709:     PetscFree(dms);
    710:   }

    712:   if (pc->dm && !pc->setupcalled) {
    713:     /* finest smoother also gets DM but it is not active, independent of whether galerkin==PC_MG_GALERKIN_EXTERNAL */
    714:     KSPSetDM(mglevels[n-1]->smoothd,pc->dm);
    715:     KSPSetDMActive(mglevels[n-1]->smoothd,PETSC_FALSE);
    716:     if (mglevels[n-1]->smoothd != mglevels[n-1]->smoothu) {
    717:       KSPSetDM(mglevels[n-1]->smoothu,pc->dm);
    718:       KSPSetDMActive(mglevels[n-1]->smoothu,PETSC_FALSE);
    719:     }
    720:   }

    722:   if (mg->galerkin < PC_MG_GALERKIN_NONE) {
    723:     Mat       A,B;
    724:     PetscBool doA = PETSC_FALSE,doB = PETSC_FALSE;
    725:     MatReuse  reuse = MAT_INITIAL_MATRIX;

    727:     if ((mg->galerkin == PC_MG_GALERKIN_PMAT) || (mg->galerkin == PC_MG_GALERKIN_BOTH)) doB = PETSC_TRUE;
    728:     if ((mg->galerkin == PC_MG_GALERKIN_MAT) || ((mg->galerkin == PC_MG_GALERKIN_BOTH) && (dA != dB))) doA = PETSC_TRUE;
    729:     if (pc->setupcalled) reuse = MAT_REUSE_MATRIX;
    730:     for (i=n-2; i>-1; i--) {
    731:       if (!mglevels[i+1]->restrct && !mglevels[i+1]->interpolate) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONGSTATE,"Must provide interpolation or restriction for each MG level except level 0");
    732:       if (!mglevels[i+1]->interpolate) {
    733:         PCMGSetInterpolation(pc,i+1,mglevels[i+1]->restrct);
    734:       }
    735:       if (!mglevels[i+1]->restrct) {
    736:         PCMGSetRestriction(pc,i+1,mglevels[i+1]->interpolate);
    737:       }
    738:       if (reuse == MAT_REUSE_MATRIX) {
    739:         KSPGetOperators(mglevels[i]->smoothd,&A,&B);
    740:       }
    741:       if (doA) {
    742:         MatGalerkin(mglevels[i+1]->restrct,dA,mglevels[i+1]->interpolate,reuse,1.0,&A);
    743:       }
    744:       if (doB) {
    745:         MatGalerkin(mglevels[i+1]->restrct,dB,mglevels[i+1]->interpolate,reuse,1.0,&B);
    746:       }
    747:       /* the management of the PetscObjectReference() and PetscObjecDereference() below is rather delicate */
    748:       if (!doA && dAeqdB) {
    749:         if (reuse == MAT_INITIAL_MATRIX) {PetscObjectReference((PetscObject)B);}
    750:         A = B;
    751:       } else if (!doA && reuse == MAT_INITIAL_MATRIX ) {
    752:         KSPGetOperators(mglevels[i]->smoothd,&A,NULL);
    753:         PetscObjectReference((PetscObject)A);
    754:       }
    755:       if (!doB && dAeqdB) {
    756:         if (reuse == MAT_INITIAL_MATRIX) {PetscObjectReference((PetscObject)A);}
    757:         B = A;
    758:       } else if (!doB && reuse == MAT_INITIAL_MATRIX) {
    759:         KSPGetOperators(mglevels[i]->smoothd,NULL,&B);
    760:         PetscObjectReference((PetscObject)B);
    761:       }
    762:       if (reuse == MAT_INITIAL_MATRIX) {
    763:         KSPSetOperators(mglevels[i]->smoothd,A,B);
    764:         PetscObjectDereference((PetscObject)A);
    765:         PetscObjectDereference((PetscObject)B);
    766:       }
    767:       dA = A;
    768:       dB = B;
    769:     }
    770:   }
    771:   if (needRestricts && pc->dm) {
    772:     for (i=n-2; i>=0; i--) {
    773:       DM  dmfine,dmcoarse;
    774:       Mat Restrict,Inject;
    775:       Vec rscale;
    776:       KSPGetDM(mglevels[i+1]->smoothd,&dmfine);
    777:       KSPGetDM(mglevels[i]->smoothd,&dmcoarse);
    778:       PCMGGetRestriction(pc,i+1,&Restrict);
    779:       PCMGGetRScale(pc,i+1,&rscale);
    780:       PCMGGetInjection(pc,i+1,&Inject);
    781:       DMRestrict(dmfine,Restrict,rscale,Inject,dmcoarse);
    782:     }
    783:   }

    785:   if (!pc->setupcalled) {
    786:     for (i=0; i<n; i++) {
    787:       KSPSetFromOptions(mglevels[i]->smoothd);
    788:     }
    789:     for (i=1; i<n; i++) {
    790:       if (mglevels[i]->smoothu && (mglevels[i]->smoothu != mglevels[i]->smoothd)) {
    791:         KSPSetFromOptions(mglevels[i]->smoothu);
    792:       }
    793:     }
    794:     /* insure that if either interpolation or restriction is set the other other one is set */
    795:     for (i=1; i<n; i++) {
    796:       PCMGGetInterpolation(pc,i,NULL);
    797:       PCMGGetRestriction(pc,i,NULL);
    798:     }
    799:     for (i=0; i<n-1; i++) {
    800:       if (!mglevels[i]->b) {
    801:         Vec *vec;
    802:         KSPCreateVecs(mglevels[i]->smoothd,1,&vec,0,NULL);
    803:         PCMGSetRhs(pc,i,*vec);
    804:         VecDestroy(vec);
    805:         PetscFree(vec);
    806:       }
    807:       if (!mglevels[i]->r && i) {
    808:         VecDuplicate(mglevels[i]->b,&tvec);
    809:         PCMGSetR(pc,i,tvec);
    810:         VecDestroy(&tvec);
    811:       }
    812:       if (!mglevels[i]->x) {
    813:         VecDuplicate(mglevels[i]->b,&tvec);
    814:         PCMGSetX(pc,i,tvec);
    815:         VecDestroy(&tvec);
    816:       }
    817:     }
    818:     if (n != 1 && !mglevels[n-1]->r) {
    819:       /* PCMGSetR() on the finest level if user did not supply it */
    820:       Vec *vec;
    821:       KSPCreateVecs(mglevels[n-1]->smoothd,1,&vec,0,NULL);
    822:       PCMGSetR(pc,n-1,*vec);
    823:       VecDestroy(vec);
    824:       PetscFree(vec);
    825:     }
    826:   }

    828:   if (pc->dm) {
    829:     /* need to tell all the coarser levels to rebuild the matrix using the DM for that level */
    830:     for (i=0; i<n-1; i++) {
    831:       if (mglevels[i]->smoothd->setupstage != KSP_SETUP_NEW) mglevels[i]->smoothd->setupstage = KSP_SETUP_NEWMATRIX;
    832:     }
    833:   }

    835:   for (i=1; i<n; i++) {
    836:     if (mglevels[i]->smoothu == mglevels[i]->smoothd || mg->am == PC_MG_FULL || mg->am == PC_MG_KASKADE || mg->cyclesperpcapply > 1){
    837:       /* if doing only down then initial guess is zero */
    838:       KSPSetInitialGuessNonzero(mglevels[i]->smoothd,PETSC_TRUE);
    839:     }
    840:     if (mglevels[i]->eventsmoothsetup) {PetscLogEventBegin(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    841:     KSPSetUp(mglevels[i]->smoothd);
    842:     if (mglevels[i]->smoothd->reason == KSP_DIVERGED_PC_FAILED) {
    843:       pc->failedreason = PC_SUBPC_ERROR;
    844:     }
    845:     if (mglevels[i]->eventsmoothsetup) {PetscLogEventEnd(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    846:     if (!mglevels[i]->residual) {
    847:       Mat mat;
    848:       KSPGetOperators(mglevels[i]->smoothd,&mat,NULL);
    849:       PCMGSetResidual(pc,i,PCMGResidualDefault,mat);
    850:     }
    851:   }
    852:   for (i=1; i<n; i++) {
    853:     if (mglevels[i]->smoothu && mglevels[i]->smoothu != mglevels[i]->smoothd) {
    854:       Mat downmat,downpmat;

    856:       /* check if operators have been set for up, if not use down operators to set them */
    857:       KSPGetOperatorsSet(mglevels[i]->smoothu,&opsset,NULL);
    858:       if (!opsset) {
    859:         KSPGetOperators(mglevels[i]->smoothd,&downmat,&downpmat);
    860:         KSPSetOperators(mglevels[i]->smoothu,downmat,downpmat);
    861:       }

    863:       KSPSetInitialGuessNonzero(mglevels[i]->smoothu,PETSC_TRUE);
    864:       if (mglevels[i]->eventsmoothsetup) {PetscLogEventBegin(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    865:       KSPSetUp(mglevels[i]->smoothu);
    866:       if (mglevels[i]->smoothu->reason == KSP_DIVERGED_PC_FAILED) {
    867:         pc->failedreason = PC_SUBPC_ERROR;
    868:       }
    869:       if (mglevels[i]->eventsmoothsetup) {PetscLogEventEnd(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    870:     }
    871:   }

    873:   if (mglevels[0]->eventsmoothsetup) {PetscLogEventBegin(mglevels[0]->eventsmoothsetup,0,0,0,0);}
    874:   KSPSetUp(mglevels[0]->smoothd);
    875:   if (mglevels[0]->smoothd->reason == KSP_DIVERGED_PC_FAILED) {
    876:     pc->failedreason = PC_SUBPC_ERROR;
    877:   }
    878:   if (mglevels[0]->eventsmoothsetup) {PetscLogEventEnd(mglevels[0]->eventsmoothsetup,0,0,0,0);}

    880:   /*
    881:      Dump the interpolation/restriction matrices plus the
    882:    Jacobian/stiffness on each level. This allows MATLAB users to
    883:    easily check if the Galerkin condition A_c = R A_f R^T is satisfied.

    885:    Only support one or the other at the same time.
    886:   */
    887: #if defined(PETSC_USE_SOCKET_VIEWER)
    888:   PetscOptionsGetBool(((PetscObject)pc)->options,((PetscObject)pc)->prefix,"-pc_mg_dump_matlab",&dump,NULL);
    889:   if (dump) viewer = PETSC_VIEWER_SOCKET_(PetscObjectComm((PetscObject)pc));
    890:   dump = PETSC_FALSE;
    891: #endif
    892:   PetscOptionsGetBool(((PetscObject)pc)->options,((PetscObject)pc)->prefix,"-pc_mg_dump_binary",&dump,NULL);
    893:   if (dump) viewer = PETSC_VIEWER_BINARY_(PetscObjectComm((PetscObject)pc));

    895:   if (viewer) {
    896:     for (i=1; i<n; i++) {
    897:       MatView(mglevels[i]->restrct,viewer);
    898:     }
    899:     for (i=0; i<n; i++) {
    900:       KSPGetPC(mglevels[i]->smoothd,&pc);
    901:       MatView(pc->mat,viewer);
    902:     }
    903:   }
    904:   return(0);
    905: }

    907: /* -------------------------------------------------------------------------------------*/

    909: PetscErrorCode PCMGGetLevels_MG(PC pc, PetscInt *levels)
    910: {
    911:   PC_MG *mg = (PC_MG *) pc->data;

    914:   *levels = mg->nlevels;
    915:   return(0);
    916: }

    918: /*@
    919:    PCMGGetLevels - Gets the number of levels to use with MG.

    921:    Not Collective

    923:    Input Parameter:
    924: .  pc - the preconditioner context

    926:    Output parameter:
    927: .  levels - the number of levels

    929:    Level: advanced

    931: .seealso: PCMGSetLevels()
    932: @*/
    933: PetscErrorCode PCMGGetLevels(PC pc,PetscInt *levels)
    934: {

    940:   *levels = 0;
    941:   PetscTryMethod(pc,"PCMGGetLevels_C",(PC,PetscInt*),(pc,levels));
    942:   return(0);
    943: }

    945: /*@
    946:    PCMGSetType - Determines the form of multigrid to use:
    947:    multiplicative, additive, full, or the Kaskade algorithm.

    949:    Logically Collective on PC

    951:    Input Parameters:
    952: +  pc - the preconditioner context
    953: -  form - multigrid form, one of PC_MG_MULTIPLICATIVE, PC_MG_ADDITIVE,
    954:    PC_MG_FULL, PC_MG_KASKADE

    956:    Options Database Key:
    957: .  -pc_mg_type <form> - Sets <form>, one of multiplicative,
    958:    additive, full, kaskade

    960:    Level: advanced

    962: .seealso: PCMGSetLevels()
    963: @*/
    964: PetscErrorCode  PCMGSetType(PC pc,PCMGType form)
    965: {
    966:   PC_MG *mg = (PC_MG*)pc->data;

    971:   mg->am = form;
    972:   if (form == PC_MG_MULTIPLICATIVE) pc->ops->applyrichardson = PCApplyRichardson_MG;
    973:   else pc->ops->applyrichardson = NULL;
    974:   return(0);
    975: }

    977: /*@
    978:    PCMGGetType - Determines the form of multigrid to use:
    979:    multiplicative, additive, full, or the Kaskade algorithm.

    981:    Logically Collective on PC

    983:    Input Parameter:
    984: .  pc - the preconditioner context

    986:    Output Parameter:
    987: .  type - one of PC_MG_MULTIPLICATIVE, PC_MG_ADDITIVE,PC_MG_FULL, PC_MG_KASKADE

    990:    Level: advanced

    992: .seealso: PCMGSetLevels()
    993: @*/
    994: PetscErrorCode  PCMGGetType(PC pc,PCMGType *type)
    995: {
    996:   PC_MG *mg = (PC_MG*)pc->data;

    1000:   *type = mg->am;
    1001:   return(0);
    1002: }

    1004: /*@
    1005:    PCMGSetCycleType - Sets the type cycles to use.  Use PCMGSetCycleTypeOnLevel() for more
    1006:    complicated cycling.

    1008:    Logically Collective on PC

    1010:    Input Parameters:
    1011: +  pc - the multigrid context
    1012: -  n - either PC_MG_CYCLE_V or PC_MG_CYCLE_W

    1014:    Options Database Key:
    1015: .  -pc_mg_cycle_type <v,w> - provide the cycle desired

    1017:    Level: advanced

    1019: .seealso: PCMGSetCycleTypeOnLevel()
    1020: @*/
    1021: PetscErrorCode  PCMGSetCycleType(PC pc,PCMGCycleType n)
    1022: {
    1023:   PC_MG        *mg        = (PC_MG*)pc->data;
    1024:   PC_MG_Levels **mglevels = mg->levels;
    1025:   PetscInt     i,levels;

    1030:   if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ORDER,"Must set MG levels with PCMGSetLevels() before calling");
    1031:   levels = mglevels[0]->levels;
    1032:   for (i=0; i<levels; i++) mglevels[i]->cycles = n;
    1033:   return(0);
    1034: }

    1036: /*@
    1037:    PCMGMultiplicativeSetCycles - Sets the number of cycles to use for each preconditioner step
    1038:          of multigrid when PCMGType of PC_MG_MULTIPLICATIVE is used

    1040:    Logically Collective on PC

    1042:    Input Parameters:
    1043: +  pc - the multigrid context
    1044: -  n - number of cycles (default is 1)

    1046:    Options Database Key:
    1047: .  -pc_mg_multiplicative_cycles n

    1049:    Level: advanced

    1051:    Notes:
    1052:     This is not associated with setting a v or w cycle, that is set with PCMGSetCycleType()

    1054: .seealso: PCMGSetCycleTypeOnLevel(), PCMGSetCycleType()
    1055: @*/
    1056: PetscErrorCode  PCMGMultiplicativeSetCycles(PC pc,PetscInt n)
    1057: {
    1058:   PC_MG        *mg        = (PC_MG*)pc->data;

    1063:   mg->cyclesperpcapply = n;
    1064:   return(0);
    1065: }

    1067: PetscErrorCode PCMGSetGalerkin_MG(PC pc,PCMGGalerkinType use)
    1068: {
    1069:   PC_MG *mg = (PC_MG*)pc->data;

    1072:   mg->galerkin = use;
    1073:   return(0);
    1074: }

    1076: /*@
    1077:    PCMGSetGalerkin - Causes the coarser grid matrices to be computed from the
    1078:       finest grid via the Galerkin process: A_i-1 = r_i * A_i * p_i

    1080:    Logically Collective on PC

    1082:    Input Parameters:
    1083: +  pc - the multigrid context
    1084: -  use - one of PC_MG_GALERKIN_BOTH,PC_MG_GALERKIN_PMAT,PC_MG_GALERKIN_MAT, or PC_MG_GALERKIN_NONE

    1086:    Options Database Key:
    1087: .  -pc_mg_galerkin <both,pmat,mat,none>

    1089:    Level: intermediate

    1091:    Notes:
    1092:     Some codes that use PCMG such as PCGAMG use Galerkin internally while constructing the hierarchy and thus do not
    1093:      use the PCMG construction of the coarser grids.

    1095: .seealso: PCMGGetGalerkin(), PCMGGalerkinType

    1097: @*/
    1098: PetscErrorCode PCMGSetGalerkin(PC pc,PCMGGalerkinType use)
    1099: {

    1104:   PetscTryMethod(pc,"PCMGSetGalerkin_C",(PC,PCMGGalerkinType),(pc,use));
    1105:   return(0);
    1106: }

    1108: /*@
    1109:    PCMGGetGalerkin - Checks if Galerkin multigrid is being used, i.e.
    1110:       A_i-1 = r_i * A_i * p_i

    1112:    Not Collective

    1114:    Input Parameter:
    1115: .  pc - the multigrid context

    1117:    Output Parameter:
    1118: .  galerkin - one of PC_MG_GALERKIN_BOTH,PC_MG_GALERKIN_PMAT,PC_MG_GALERKIN_MAT, PC_MG_GALERKIN_NONE, or PC_MG_GALERKIN_EXTERNAL

    1120:    Level: intermediate

    1122: .seealso: PCMGSetGalerkin(), PCMGGalerkinType

    1124: @*/
    1125: PetscErrorCode  PCMGGetGalerkin(PC pc,PCMGGalerkinType  *galerkin)
    1126: {
    1127:   PC_MG *mg = (PC_MG*)pc->data;

    1131:   *galerkin = mg->galerkin;
    1132:   return(0);
    1133: }

    1135: /*@
    1136:    PCMGSetNumberSmooth - Sets the number of pre and post-smoothing steps to use
    1137:    on all levels.  Use PCMGDistinctSmoothUp() to create separate up and down smoothers if you want different numbers of
    1138:    pre- and post-smoothing steps.

    1140:    Logically Collective on PC

    1142:    Input Parameters:
    1143: +  mg - the multigrid context
    1144: -  n - the number of smoothing steps

    1146:    Options Database Key:
    1147: .  -mg_levels_ksp_max_it <n> - Sets number of pre and post-smoothing steps

    1149:    Level: advanced

    1151:    Notes:
    1152:     this does not set a value on the coarsest grid, since we assume that
    1153:     there is no separate smooth up on the coarsest grid.

    1155: .seealso: PCMGSetDistinctSmoothUp()
    1156: @*/
    1157: PetscErrorCode  PCMGSetNumberSmooth(PC pc,PetscInt n)
    1158: {
    1159:   PC_MG          *mg        = (PC_MG*)pc->data;
    1160:   PC_MG_Levels   **mglevels = mg->levels;
    1162:   PetscInt       i,levels;

    1167:   if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ORDER,"Must set MG levels with PCMGSetLevels() before calling");
    1168:   levels = mglevels[0]->levels;

    1170:   for (i=1; i<levels; i++) {
    1171:     KSPSetTolerances(mglevels[i]->smoothu,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT,n);
    1172:     KSPSetTolerances(mglevels[i]->smoothd,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT,n);
    1173:     mg->default_smoothu = n;
    1174:     mg->default_smoothd = n;
    1175:   }
    1176:   return(0);
    1177: }

    1179: /*@
    1180:    PCMGSetDistinctSmoothUp - sets the up (post) smoother to be a separate KSP from the down (pre) smoother on all levels
    1181:        and adds the suffix _up to the options name

    1183:    Logically Collective on PC

    1185:    Input Parameters:
    1186: .  pc - the preconditioner context

    1188:    Options Database Key:
    1189: .  -pc_mg_distinct_smoothup

    1191:    Level: advanced

    1193:    Notes:
    1194:     this does not set a value on the coarsest grid, since we assume that
    1195:     there is no separate smooth up on the coarsest grid.

    1197: .seealso: PCMGSetNumberSmooth()
    1198: @*/
    1199: PetscErrorCode  PCMGSetDistinctSmoothUp(PC pc)
    1200: {
    1201:   PC_MG          *mg        = (PC_MG*)pc->data;
    1202:   PC_MG_Levels   **mglevels = mg->levels;
    1204:   PetscInt       i,levels;
    1205:   KSP            subksp;

    1209:   if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ORDER,"Must set MG levels with PCMGSetLevels() before calling");
    1210:   levels = mglevels[0]->levels;

    1212:   for (i=1; i<levels; i++) {
    1213:     const char *prefix = NULL;
    1214:     /* make sure smoother up and down are different */
    1215:     PCMGGetSmootherUp(pc,i,&subksp);
    1216:     KSPGetOptionsPrefix(mglevels[i]->smoothd,&prefix);
    1217:     KSPSetOptionsPrefix(subksp,prefix);
    1218:     KSPAppendOptionsPrefix(subksp,"up_");
    1219:   }
    1220:   return(0);
    1221: }

    1223: /* No new matrices are created, and the coarse operator matrices are the references to the original ones */
    1224: PetscErrorCode  PCGetInterpolations_MG(PC pc,PetscInt *num_levels,Mat *interpolations[])
    1225: {
    1226:   PC_MG          *mg        = (PC_MG*)pc->data;
    1227:   PC_MG_Levels   **mglevels = mg->levels;
    1228:   Mat            *mat;
    1229:   PetscInt       l;

    1233:   if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONGSTATE,"Must set MG levels before calling");
    1234:   PetscMalloc1(mg->nlevels,&mat);
    1235:   for (l=1; l< mg->nlevels; l++) {
    1236:     mat[l-1] = mglevels[l]->interpolate;
    1237:     PetscObjectReference((PetscObject)mat[l-1]);
    1238:   }
    1239:   *num_levels = mg->nlevels;
    1240:   *interpolations = mat;
    1241:   return(0);
    1242: }

    1244: /* No new matrices are created, and the coarse operator matrices are the references to the original ones */
    1245: PetscErrorCode  PCGetCoarseOperators_MG(PC pc,PetscInt *num_levels,Mat *coarseOperators[])
    1246: {
    1247:   PC_MG          *mg        = (PC_MG*)pc->data;
    1248:   PC_MG_Levels   **mglevels = mg->levels;
    1249:   PetscInt       l;
    1250:   Mat            *mat;

    1254:   if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONGSTATE,"Must set MG levels before calling");
    1255:   PetscMalloc1(mg->nlevels,&mat);
    1256:   for (l=0; l<mg->nlevels-1; l++) {
    1257:     KSPGetOperators(mglevels[l]->smoothd,NULL,&(mat[l]));
    1258:     PetscObjectReference((PetscObject)mat[l]);
    1259:   }
    1260:   *num_levels = mg->nlevels;
    1261:   *coarseOperators = mat;
    1262:   return(0);
    1263: }

    1265: /* ----------------------------------------------------------------------------------------*/

    1267: /*MC
    1268:    PCMG - Use multigrid preconditioning. This preconditioner requires you provide additional
    1269:     information about the coarser grid matrices and restriction/interpolation operators.

    1271:    Options Database Keys:
    1272: +  -pc_mg_levels <nlevels> - number of levels including finest
    1273: .  -pc_mg_cycle_type <v,w> - provide the cycle desired
    1274: .  -pc_mg_type <additive,multiplicative,full,kaskade> - multiplicative is the default
    1275: .  -pc_mg_log - log information about time spent on each level of the solver
    1276: .  -pc_mg_distinct_smoothup - configure up (after interpolation) and down (before restriction) smoothers separately (with different options prefixes)
    1277: .  -pc_mg_galerkin <both,pmat,mat,none> - use Galerkin process to compute coarser operators, i.e. Acoarse = R A R'
    1278: .  -pc_mg_multiplicative_cycles - number of cycles to use as the preconditioner (defaults to 1)
    1279: .  -pc_mg_dump_matlab - dumps the matrices for each level and the restriction/interpolation matrices
    1280:                         to the Socket viewer for reading from MATLAB.
    1281: -  -pc_mg_dump_binary - dumps the matrices for each level and the restriction/interpolation matrices
    1282:                         to the binary output file called binaryoutput

    1284:    Notes:
    1285:     If one uses a Krylov method such GMRES or CG as the smoother then one must use KSPFGMRES, KSPGCR, or KSPRICHARDSON as the outer Krylov method

    1287:        When run with a single level the smoother options are used on that level NOT the coarse grid solver options

    1289:        When run with KSPRICHARDSON the convergence test changes slightly if monitor is turned on. The iteration count may change slightly. This
    1290:        is because without monitoring the residual norm is computed WITHIN each multigrid cycle on the finest level after the pre-smoothing
    1291:        (because the residual has just been computed for the multigrid algorithm and is hence available for free) while with monitoring the
    1292:        residual is computed at the end of each cycle.

    1294:    Level: intermediate

    1296: .seealso:  PCCreate(), PCSetType(), PCType (for list of available types), PC, PCMGType, PCEXOTIC, PCGAMG, PCML, PCHYPRE
    1297:            PCMGSetLevels(), PCMGGetLevels(), PCMGSetType(), PCMGSetCycleType(),
    1298:            PCMGSetDistinctSmoothUp(), PCMGGetCoarseSolve(), PCMGSetResidual(), PCMGSetInterpolation(),
    1299:            PCMGSetRestriction(), PCMGGetSmoother(), PCMGGetSmootherUp(), PCMGGetSmootherDown(),
    1300:            PCMGSetCycleTypeOnLevel(), PCMGSetRhs(), PCMGSetX(), PCMGSetR()
    1301: M*/

    1303: PETSC_EXTERN PetscErrorCode PCCreate_MG(PC pc)
    1304: {
    1305:   PC_MG          *mg;

    1309:   PetscNewLog(pc,&mg);
    1310:   pc->data     = (void*)mg;
    1311:   mg->nlevels  = -1;
    1312:   mg->am       = PC_MG_MULTIPLICATIVE;
    1313:   mg->galerkin = PC_MG_GALERKIN_NONE;

    1315:   pc->useAmat = PETSC_TRUE;

    1317:   pc->ops->apply          = PCApply_MG;
    1318:   pc->ops->setup          = PCSetUp_MG;
    1319:   pc->ops->reset          = PCReset_MG;
    1320:   pc->ops->destroy        = PCDestroy_MG;
    1321:   pc->ops->setfromoptions = PCSetFromOptions_MG;
    1322:   pc->ops->view           = PCView_MG;

    1324:   PetscObjectComposeFunction((PetscObject)pc,"PCMGSetGalerkin_C",PCMGSetGalerkin_MG);
    1325:   PetscObjectComposeFunction((PetscObject)pc,"PCMGGetLevels_C",PCMGGetLevels_MG);
    1326:   PetscObjectComposeFunction((PetscObject)pc,"PCMGSetLevels_C",PCMGSetLevels_MG);
    1327:   PetscObjectComposeFunction((PetscObject)pc,"PCGetInterpolations_C",PCGetInterpolations_MG);
    1328:   PetscObjectComposeFunction((PetscObject)pc,"PCGetCoarseOperators_C",PCGetCoarseOperators_MG);
    1329:   return(0);
    1330: }