Date: 2015-10-02T22:17:57+00:00

Actual source code: mg.c
petsc-3.6.2 2015-10-02
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      2: /*
      3:     Defines the multigrid preconditioner interface.
      4: */
      5: #include <petsc/private/pcmgimpl.h>                    /*I "petscksp.h" I*/
      6: #include <petscdm.h>

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

     18:   if (mglevels->eventsmoothsolve) {PetscLogEventBegin(mglevels->eventsmoothsolve,0,0,0,0);}
     19:   KSPSolve(mglevels->smoothd,mglevels->b,mglevels->x);  /* pre-smooth */
     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:     if (mglevels->eventsmoothsolve) {PetscLogEventEnd(mglevels->eventsmoothsolve,0,0,0,0);}
     56:   }
     57:   return(0);
     58: }

     62: 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)
     63: {
     64:   PC_MG          *mg        = (PC_MG*)pc->data;
     65:   PC_MG_Levels   **mglevels = mg->levels;
     67:   PetscInt       levels = mglevels[0]->levels,i;

     70:   /* When the DM is supplying the matrix then it will not exist until here */
     71:   for (i=0; i<levels; i++) {
     72:     if (!mglevels[i]->A) {
     73:       KSPGetOperators(mglevels[i]->smoothu,&mglevels[i]->A,NULL);
     74:       PetscObjectReference((PetscObject)mglevels[i]->A);
     75:     }
     76:   }
     77:   mglevels[levels-1]->b = b;
     78:   mglevels[levels-1]->x = x;

     80:   mg->rtol   = rtol;
     81:   mg->abstol = abstol;
     82:   mg->dtol   = dtol;
     83:   if (rtol) {
     84:     /* compute initial residual norm for relative convergence test */
     85:     PetscReal rnorm;
     86:     if (zeroguess) {
     87:       VecNorm(b,NORM_2,&rnorm);
     88:     } else {
     89:       (*mglevels[levels-1]->residual)(mglevels[levels-1]->A,b,x,w);
     90:       VecNorm(w,NORM_2,&rnorm);
     91:     }
     92:     mg->ttol = PetscMax(rtol*rnorm,abstol);
     93:   } else if (abstol) mg->ttol = abstol;
     94:   else mg->ttol = 0.0;

     96:   /* since smoother is applied to full system, not just residual we need to make sure that smoothers don't
     97:      stop prematurely due to small residual */
     98:   for (i=1; i<levels; i++) {
     99:     KSPSetTolerances(mglevels[i]->smoothu,0,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);
    100:     if (mglevels[i]->smoothu != mglevels[i]->smoothd) {
    101:       KSPSetTolerances(mglevels[i]->smoothd,0,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);
    102:     }
    103:   }

    105:   *reason = (PCRichardsonConvergedReason)0;
    106:   for (i=0; i<its; i++) {
    107:     PCMGMCycle_Private(pc,mglevels+levels-1,reason);
    108:     if (*reason) break;
    109:   }
    110:   if (!*reason) *reason = PCRICHARDSON_CONVERGED_ITS;
    111:   *outits = i;
    112:   return(0);
    113: }

    117: PetscErrorCode PCReset_MG(PC pc)
    118: {
    119:   PC_MG          *mg        = (PC_MG*)pc->data;
    120:   PC_MG_Levels   **mglevels = mg->levels;
    122:   PetscInt       i,n;

    125:   if (mglevels) {
    126:     n = mglevels[0]->levels;
    127:     for (i=0; i<n-1; i++) {
    128:       VecDestroy(&mglevels[i+1]->r);
    129:       VecDestroy(&mglevels[i]->b);
    130:       VecDestroy(&mglevels[i]->x);
    131:       MatDestroy(&mglevels[i+1]->restrct);
    132:       MatDestroy(&mglevels[i+1]->interpolate);
    133:       VecDestroy(&mglevels[i+1]->rscale);
    134:     }

    136:     for (i=0; i<n; i++) {
    137:       MatDestroy(&mglevels[i]->A);
    138:       if (mglevels[i]->smoothd != mglevels[i]->smoothu) {
    139:         KSPReset(mglevels[i]->smoothd);
    140:       }
    141:       KSPReset(mglevels[i]->smoothu);
    142:     }
    143:   }
    144:   return(0);
    145: }

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

    153:    Logically Collective on PC

    155:    Input Parameters:
    156: +  pc - the preconditioner context
    157: .  levels - the number of levels
    158: -  comms - optional communicators for each level; this is to allow solving the coarser problems
    159:            on smaller sets of processors. Use NULL_OBJECT for default in Fortran

    161:    Level: intermediate

    163:    Notes:
    164:      If the number of levels is one then the multigrid uses the -mg_levels prefix
    165:   for setting the level options rather than the -mg_coarse prefix.

    167: .keywords: MG, set, levels, multigrid

    169: .seealso: PCMGSetType(), PCMGGetLevels()
    170: @*/
    171: PetscErrorCode  PCMGSetLevels(PC pc,PetscInt levels,MPI_Comm *comms)
    172: {
    174:   PC_MG          *mg        = (PC_MG*)pc->data;
    175:   MPI_Comm       comm;
    176:   PC_MG_Levels   **mglevels = mg->levels;
    177:   PCMGType       mgtype     = mg->am;
    178:   PetscInt       mgctype    = (PetscInt) PC_MG_CYCLE_V;
    179:   PetscInt       i;
    180:   PetscMPIInt    size;
    181:   const char     *prefix;
    182:   PC             ipc;
    183:   PetscInt       n;

    188:   PetscObjectGetComm((PetscObject)pc,&comm);
    189:   if (mg->nlevels == levels) return(0);
    190:   if (mglevels) {
    191:     mgctype = mglevels[0]->cycles;
    192:     /* changing the number of levels so free up the previous stuff */
    193:     PCReset_MG(pc);
    194:     n    = mglevels[0]->levels;
    195:     for (i=0; i<n; i++) {
    196:       if (mglevels[i]->smoothd != mglevels[i]->smoothu) {
    197:         KSPDestroy(&mglevels[i]->smoothd);
    198:       }
    199:       KSPDestroy(&mglevels[i]->smoothu);
    200:       PetscFree(mglevels[i]);
    201:     }
    202:     PetscFree(mg->levels);
    203:   }

    205:   mg->nlevels = levels;

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

    210:   PCGetOptionsPrefix(pc,&prefix);

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

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

    226:     if (comms) comm = comms[i];
    227:     KSPCreate(comm,&mglevels[i]->smoothd);
    228:     KSPSetErrorIfNotConverged(mglevels[i]->smoothd,pc->erroriffailure);
    229:     KSPSetType(mglevels[i]->smoothd,KSPCHEBYSHEV);
    230:     KSPSetConvergenceTest(mglevels[i]->smoothd,KSPConvergedSkip,NULL,NULL);
    231:     KSPSetNormType(mglevels[i]->smoothd,KSP_NORM_NONE);
    232:     KSPGetPC(mglevels[i]->smoothd,&ipc);
    233:     PCSetType(ipc,PCSOR);
    234:     PetscObjectIncrementTabLevel((PetscObject)mglevels[i]->smoothd,(PetscObject)pc,levels-i);
    235:     KSPSetTolerances(mglevels[i]->smoothd,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT, i ? mg->default_smoothd : 1);
    236:     KSPSetOptionsPrefix(mglevels[i]->smoothd,prefix);

    238:     /* do special stuff for coarse grid */
    239:     if (!i && levels > 1) {
    240:       KSPAppendOptionsPrefix(mglevels[0]->smoothd,"mg_coarse_");

    242:       /* coarse solve is (redundant) LU by default; set shifttype NONZERO to avoid annoying zero-pivot in LU preconditioner */
    243:       KSPSetType(mglevels[0]->smoothd,KSPPREONLY);
    244:       KSPGetPC(mglevels[0]->smoothd,&ipc);
    245:       MPI_Comm_size(comm,&size);
    246:       if (size > 1) {
    247:         KSP innerksp;
    248:         PC  innerpc;
    249:         PCSetType(ipc,PCREDUNDANT);
    250:         PCRedundantGetKSP(ipc,&innerksp);
    251:         KSPGetPC(innerksp,&innerpc);
    252:         PCFactorSetShiftType(innerpc,MAT_SHIFT_INBLOCKS);
    253:       } else {
    254:         PCSetType(ipc,PCLU);
    255:         PCFactorSetShiftType(ipc,MAT_SHIFT_INBLOCKS);
    256:       }
    257:     } else {
    258:       char tprefix[128];
    259:       sprintf(tprefix,"mg_levels_%d_",(int)i);
    260:       KSPAppendOptionsPrefix(mglevels[i]->smoothd,tprefix);
    261:     }
    262:     PetscLogObjectParent((PetscObject)pc,(PetscObject)mglevels[i]->smoothd);

    264:     mglevels[i]->smoothu = mglevels[i]->smoothd;
    265:     mg->rtol             = 0.0;
    266:     mg->abstol           = 0.0;
    267:     mg->dtol             = 0.0;
    268:     mg->ttol             = 0.0;
    269:     mg->cyclesperpcapply = 1;
    270:   }
    271:   mg->levels = mglevels;
    272:   PCMGSetType(pc,mgtype);
    273:   return(0);
    274: }

    279: PetscErrorCode PCDestroy_MG(PC pc)
    280: {
    282:   PC_MG          *mg        = (PC_MG*)pc->data;
    283:   PC_MG_Levels   **mglevels = mg->levels;
    284:   PetscInt       i,n;

    287:   PCReset_MG(pc);
    288:   if (mglevels) {
    289:     n = mglevels[0]->levels;
    290:     for (i=0; i<n; i++) {
    291:       if (mglevels[i]->smoothd != mglevels[i]->smoothu) {
    292:         KSPDestroy(&mglevels[i]->smoothd);
    293:       }
    294:       KSPDestroy(&mglevels[i]->smoothu);
    295:       PetscFree(mglevels[i]);
    296:     }
    297:     PetscFree(mg->levels);
    298:   }
    299:   PetscFree(pc->data);
    300:   return(0);
    301: }

    305: extern PetscErrorCode PCMGACycle_Private(PC,PC_MG_Levels**);
    306: extern PetscErrorCode PCMGFCycle_Private(PC,PC_MG_Levels**);
    307: extern PetscErrorCode PCMGKCycle_Private(PC,PC_MG_Levels**);

    309: /*
    310:    PCApply_MG - Runs either an additive, multiplicative, Kaskadic
    311:              or full cycle of multigrid.

    313:   Note:
    314:   A simple wrapper which calls PCMGMCycle(),PCMGACycle(), or PCMGFCycle().
    315: */
    318: static PetscErrorCode PCApply_MG(PC pc,Vec b,Vec x)
    319: {
    320:   PC_MG          *mg        = (PC_MG*)pc->data;
    321:   PC_MG_Levels   **mglevels = mg->levels;
    323:   PetscInt       levels = mglevels[0]->levels,i;

    326:   if (mg->stageApply) {PetscLogStagePush(mg->stageApply);}
    327:   /* When the DM is supplying the matrix then it will not exist until here */
    328:   for (i=0; i<levels; i++) {
    329:     if (!mglevels[i]->A) {
    330:       KSPGetOperators(mglevels[i]->smoothu,&mglevels[i]->A,NULL);
    331:       PetscObjectReference((PetscObject)mglevels[i]->A);
    332:     }
    333:   }

    335:   mglevels[levels-1]->b = b;
    336:   mglevels[levels-1]->x = x;
    337:   if (mg->am == PC_MG_MULTIPLICATIVE) {
    338:     VecSet(x,0.0);
    339:     for (i=0; i<mg->cyclesperpcapply; i++) {
    340:       PCMGMCycle_Private(pc,mglevels+levels-1,NULL);
    341:     }
    342:   } else if (mg->am == PC_MG_ADDITIVE) {
    343:     PCMGACycle_Private(pc,mglevels);
    344:   } else if (mg->am == PC_MG_KASKADE) {
    345:     PCMGKCycle_Private(pc,mglevels);
    346:   } else {
    347:     PCMGFCycle_Private(pc,mglevels);
    348:   }
    349:   if (mg->stageApply) {PetscLogStagePop();}
    350:   return(0);
    351: }

    356: PetscErrorCode PCSetFromOptions_MG(PetscOptions *PetscOptionsObject,PC pc)
    357: {
    359:   PetscInt       m,levels = 1,cycles;
    360:   PetscBool      flg,set;
    361:   PC_MG          *mg        = (PC_MG*)pc->data;
    362:   PC_MG_Levels   **mglevels = mg->levels;
    363:   PCMGType       mgtype;
    364:   PCMGCycleType  mgctype;

    367:   PetscOptionsHead(PetscOptionsObject,"Multigrid options");
    368:   if (!mg->levels) {
    369:     PetscOptionsInt("-pc_mg_levels","Number of Levels","PCMGSetLevels",levels,&levels,&flg);
    370:     if (!flg && pc->dm) {
    371:       DMGetRefineLevel(pc->dm,&levels);
    372:       levels++;
    373:       mg->usedmfornumberoflevels = PETSC_TRUE;
    374:     }
    375:     PCMGSetLevels(pc,levels,NULL);
    376:   }
    377:   mglevels = mg->levels;

    379:   mgctype = (PCMGCycleType) mglevels[0]->cycles;
    380:   PetscOptionsEnum("-pc_mg_cycle_type","V cycle or for W-cycle","PCMGSetCycleType",PCMGCycleTypes,(PetscEnum)mgctype,(PetscEnum*)&mgctype,&flg);
    381:   if (flg) {
    382:     PCMGSetCycleType(pc,mgctype);
    383:   }
    384:   flg  = PETSC_FALSE;
    385:   PetscOptionsBool("-pc_mg_galerkin","Use Galerkin process to compute coarser operators","PCMGSetGalerkin",flg,&flg,&set);
    386:   if (set) {
    387:     PCMGSetGalerkin(pc,flg);
    388:   }
    389:   PetscOptionsInt("-pc_mg_smoothup","Number of post-smoothing steps","PCMGSetNumberSmoothUp",mg->default_smoothu,&m,&flg);
    390:   if (flg) {
    391:     PCMGSetNumberSmoothUp(pc,m);
    392:   }
    393:   PetscOptionsInt("-pc_mg_smoothdown","Number of pre-smoothing steps","PCMGSetNumberSmoothDown",mg->default_smoothd,&m,&flg);
    394:   if (flg) {
    395:     PCMGSetNumberSmoothDown(pc,m);
    396:   }
    397:   mgtype = mg->am;
    398:   PetscOptionsEnum("-pc_mg_type","Multigrid type","PCMGSetType",PCMGTypes,(PetscEnum)mgtype,(PetscEnum*)&mgtype,&flg);
    399:   if (flg) {
    400:     PCMGSetType(pc,mgtype);
    401:   }
    402:   if (mg->am == PC_MG_MULTIPLICATIVE) {
    403:     PetscOptionsInt("-pc_mg_multiplicative_cycles","Number of cycles for each preconditioner step","PCMGMultiplicativeSetCycles",mg->cyclesperpcapply,&cycles,&flg);
    404:     if (flg) {
    405:       PCMGMultiplicativeSetCycles(pc,cycles);
    406:     }
    407:   }
    408:   flg  = PETSC_FALSE;
    409:   PetscOptionsBool("-pc_mg_log","Log times for each multigrid level","None",flg,&flg,NULL);
    410:   if (flg) {
    411:     PetscInt i;
    412:     char     eventname[128];
    413:     if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONGSTATE,"Must set MG levels before calling");
    414:     levels = mglevels[0]->levels;
    415:     for (i=0; i<levels; i++) {
    416:       sprintf(eventname,"MGSetup Level %d",(int)i);
    417:       PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventsmoothsetup);
    418:       sprintf(eventname,"MGSmooth Level %d",(int)i);
    419:       PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventsmoothsolve);
    420:       if (i) {
    421:         sprintf(eventname,"MGResid Level %d",(int)i);
    422:         PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventresidual);
    423:         sprintf(eventname,"MGInterp Level %d",(int)i);
    424:         PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventinterprestrict);
    425:       }
    426:     }

    428: #if defined(PETSC_USE_LOG)
    429:     {
    430:       const char    *sname = "MG Apply";
    431:       PetscStageLog stageLog;
    432:       PetscInt      st;

    435:       PetscLogGetStageLog(&stageLog);
    436:       for (st = 0; st < stageLog->numStages; ++st) {
    437:         PetscBool same;

    439:         PetscStrcmp(stageLog->stageInfo[st].name, sname, &same);
    440:         if (same) mg->stageApply = st;
    441:       }
    442:       if (!mg->stageApply) {
    443:         PetscLogStageRegister(sname, &mg->stageApply);
    444:       }
    445:     }
    446: #endif
    447:   }
    448:   PetscOptionsTail();
    449:   return(0);
    450: }

    452: const char *const PCMGTypes[] = {"MULTIPLICATIVE","ADDITIVE","FULL","KASKADE","PCMGType","PC_MG",0};
    453: const char *const PCMGCycleTypes[] = {"invalid","v","w","PCMGCycleType","PC_MG_CYCLE",0};

    455: #include <petscdraw.h>
    458: PetscErrorCode PCView_MG(PC pc,PetscViewer viewer)
    459: {
    460:   PC_MG          *mg        = (PC_MG*)pc->data;
    461:   PC_MG_Levels   **mglevels = mg->levels;
    463:   PetscInt       levels = mglevels ? mglevels[0]->levels : 0,i;
    464:   PetscBool      iascii,isbinary,isdraw;

    467:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
    468:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);
    469:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERDRAW,&isdraw);
    470:   if (iascii) {
    471:     const char *cyclename = levels ? (mglevels[0]->cycles == PC_MG_CYCLE_V ? "v" : "w") : "unknown";
    472:     PetscViewerASCIIPrintf(viewer,"  MG: type is %s, levels=%D cycles=%s\n", PCMGTypes[mg->am],levels,cyclename);
    473:     if (mg->am == PC_MG_MULTIPLICATIVE) {
    474:       PetscViewerASCIIPrintf(viewer,"    Cycles per PCApply=%d\n",mg->cyclesperpcapply);
    475:     }
    476:     if (mg->galerkin) {
    477:       PetscViewerASCIIPrintf(viewer,"    Using Galerkin computed coarse grid matrices\n");
    478:     } else {
    479:       PetscViewerASCIIPrintf(viewer,"    Not using Galerkin computed coarse grid matrices\n");
    480:     }
    481:     if (mg->view){
    482:       (*mg->view)(pc,viewer);
    483:     }
    484:     for (i=0; i<levels; i++) {
    485:       if (!i) {
    486:         PetscViewerASCIIPrintf(viewer,"Coarse grid solver -- level -------------------------------\n",i);
    487:       } else {
    488:         PetscViewerASCIIPrintf(viewer,"Down solver (pre-smoother) on level %D -------------------------------\n",i);
    489:       }
    490:       PetscViewerASCIIPushTab(viewer);
    491:       KSPView(mglevels[i]->smoothd,viewer);
    492:       PetscViewerASCIIPopTab(viewer);
    493:       if (i && mglevels[i]->smoothd == mglevels[i]->smoothu) {
    494:         PetscViewerASCIIPrintf(viewer,"Up solver (post-smoother) same as down solver (pre-smoother)\n");
    495:       } else if (i) {
    496:         PetscViewerASCIIPrintf(viewer,"Up solver (post-smoother) on level %D -------------------------------\n",i);
    497:         PetscViewerASCIIPushTab(viewer);
    498:         KSPView(mglevels[i]->smoothu,viewer);
    499:         PetscViewerASCIIPopTab(viewer);
    500:       }
    501:     }
    502:   } else if (isbinary) {
    503:     for (i=levels-1; i>=0; i--) {
    504:       KSPView(mglevels[i]->smoothd,viewer);
    505:       if (i && mglevels[i]->smoothd != mglevels[i]->smoothu) {
    506:         KSPView(mglevels[i]->smoothu,viewer);
    507:       }
    508:     }
    509:   } else if (isdraw) {
    510:     PetscDraw draw;
    511:     PetscReal x,w,y,bottom,th;
    512:     PetscViewerDrawGetDraw(viewer,0,&draw);
    513:     PetscDrawGetCurrentPoint(draw,&x,&y);
    514:     PetscDrawStringGetSize(draw,NULL,&th);
    515:     bottom = y - th;
    516:     for (i=levels-1; i>=0; i--) {
    517:       if (!mglevels[i]->smoothu || (mglevels[i]->smoothu == mglevels[i]->smoothd)) {
    518:         PetscDrawPushCurrentPoint(draw,x,bottom);
    519:         KSPView(mglevels[i]->smoothd,viewer);
    520:         PetscDrawPopCurrentPoint(draw);
    521:       } else {
    522:         w    = 0.5*PetscMin(1.0-x,x);
    523:         PetscDrawPushCurrentPoint(draw,x+w,bottom);
    524:         KSPView(mglevels[i]->smoothd,viewer);
    525:         PetscDrawPopCurrentPoint(draw);
    526:         PetscDrawPushCurrentPoint(draw,x-w,bottom);
    527:         KSPView(mglevels[i]->smoothu,viewer);
    528:         PetscDrawPopCurrentPoint(draw);
    529:       }
    530:       PetscDrawGetBoundingBox(draw,NULL,&bottom,NULL,NULL);
    531:       bottom -= th;
    532:     }
    533:   }
    534:   return(0);
    535: }

    537: #include <petsc/private/dmimpl.h>
    538: #include <petsc/private/kspimpl.h>

    540: /*
    541:     Calls setup for the KSP on each level
    542: */
    545: PetscErrorCode PCSetUp_MG(PC pc)
    546: {
    547:   PC_MG          *mg        = (PC_MG*)pc->data;
    548:   PC_MG_Levels   **mglevels = mg->levels;
    550:   PetscInt       i,n = mglevels[0]->levels;
    551:   PC             cpc;
    552:   PetscBool      preonly,lu,redundant,cholesky,svd,dump = PETSC_FALSE,opsset,use_amat,missinginterpolate = PETSC_FALSE;
    553:   Mat            dA,dB;
    554:   Vec            tvec;
    555:   DM             *dms;
    556:   PetscViewer    viewer = 0;

    559:   /* FIX: Move this to PCSetFromOptions_MG? */
    560:   if (mg->usedmfornumberoflevels) {
    561:     PetscInt levels;
    562:     DMGetRefineLevel(pc->dm,&levels);
    563:     levels++;
    564:     if (levels > n) { /* the problem is now being solved on a finer grid */
    565:       PCMGSetLevels(pc,levels,NULL);
    566:       n        = levels;
    567:       PCSetFromOptions(pc); /* it is bad to call this here, but otherwise will never be called for the new hierarchy */
    568:       mglevels =  mg->levels;
    569:     }
    570:   }
    571:   KSPGetPC(mglevels[0]->smoothd,&cpc);

    574:   /* If user did not provide fine grid operators OR operator was not updated since last global KSPSetOperators() */
    575:   /* so use those from global PC */
    576:   /* Is this what we always want? What if user wants to keep old one? */
    577:   KSPGetOperatorsSet(mglevels[n-1]->smoothd,NULL,&opsset);
    578:   if (opsset) {
    579:     Mat mmat;
    580:     KSPGetOperators(mglevels[n-1]->smoothd,NULL,&mmat);
    581:     if (mmat == pc->pmat) opsset = PETSC_FALSE;
    582:   }

    584:   if (!opsset) {
    585:     PCGetUseAmat(pc,&use_amat);
    586:     if(use_amat){
    587:       PetscInfo(pc,"Using outer operators to define finest grid operator \n  because PCMGGetSmoother(pc,nlevels-1,&ksp);KSPSetOperators(ksp,...); was not called.\n");
    588:       KSPSetOperators(mglevels[n-1]->smoothd,pc->mat,pc->pmat);
    589:     }
    590:     else {
    591:       PetscInfo(pc,"Using matrix (pmat) operators to define finest grid operator \n  because PCMGGetSmoother(pc,nlevels-1,&ksp);KSPSetOperators(ksp,...); was not called.\n");
    592:       KSPSetOperators(mglevels[n-1]->smoothd,pc->pmat,pc->pmat);
    593:     }
    594:   }

    596:   for (i=n-1; i>0; i--) {
    597:     if (!(mglevels[i]->interpolate || mglevels[i]->restrct)) {
    598:       missinginterpolate = PETSC_TRUE;
    599:       continue;
    600:     }
    601:   }
    602:   /*
    603:    Skipping if user has provided all interpolation/restriction needed (since DM might not be able to produce them (when coming from SNES/TS)
    604:    Skipping for galerkin==2 (externally managed hierarchy such as ML and GAMG). Cleaner logic here would be great. Wrap ML/GAMG as DMs?
    605:   */
    606:   if (missinginterpolate && pc->dm && mg->galerkin != 2 && !pc->setupcalled) {
    607:     /* construct the interpolation from the DMs */
    608:     Mat p;
    609:     Vec rscale;
    610:     PetscMalloc1(n,&dms);
    611:     dms[n-1] = pc->dm;
    612:     /* Separately create them so we do not get DMKSP interference between levels */
    613:     for (i=n-2; i>-1; i--) {DMCoarsen(dms[i+1],MPI_COMM_NULL,&dms[i]);}
    614:     for (i=n-2; i>-1; i--) {
    615:       DMKSP kdm;
    616:       KSPSetDM(mglevels[i]->smoothd,dms[i]);
    617:       if (mg->galerkin) {KSPSetDMActive(mglevels[i]->smoothd,PETSC_FALSE);}
    618:       DMGetDMKSPWrite(dms[i],&kdm);
    619:       /* Ugly hack so that the next KSPSetUp() will use the RHS that we set. A better fix is to change dmActive to take
    620:        * a bitwise OR of computing the matrix, RHS, and initial iterate. */
    621:       kdm->ops->computerhs = NULL;
    622:       kdm->rhsctx          = NULL;
    623:       if (!mglevels[i+1]->interpolate) {
    624:         DMCreateInterpolation(dms[i],dms[i+1],&p,&rscale);
    625:         PCMGSetInterpolation(pc,i+1,p);
    626:         if (rscale) {PCMGSetRScale(pc,i+1,rscale);}
    627:         VecDestroy(&rscale);
    628:         MatDestroy(&p);
    629:       }
    630:     }

    632:     for (i=n-2; i>-1; i--) {DMDestroy(&dms[i]);}
    633:     PetscFree(dms);
    634:   }

    636:   if (pc->dm && !pc->setupcalled) {
    637:     /* finest smoother also gets DM but it is not active, independent of whether galerkin==2 */
    638:     KSPSetDM(mglevels[n-1]->smoothd,pc->dm);
    639:     KSPSetDMActive(mglevels[n-1]->smoothd,PETSC_FALSE);
    640:   }

    642:   if (mg->galerkin == 1) {
    643:     Mat B;
    644:     /* currently only handle case where mat and pmat are the same on coarser levels */
    645:     KSPGetOperators(mglevels[n-1]->smoothd,&dA,&dB);
    646:     if (!pc->setupcalled) {
    647:       for (i=n-2; i>-1; i--) {
    648:         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");
    649:         if (!mglevels[i+1]->interpolate) {
    650:           PCMGSetInterpolation(pc,i+1,mglevels[i+1]->restrct);
    651:         }
    652:         if (!mglevels[i+1]->restrct) {
    653:           PCMGSetRestriction(pc,i+1,mglevels[i+1]->interpolate);
    654:         }
    655:         if (mglevels[i+1]->interpolate == mglevels[i+1]->restrct) {
    656:           MatPtAP(dB,mglevels[i+1]->interpolate,MAT_INITIAL_MATRIX,1.0,&B);
    657:         } else {
    658:           MatMatMatMult(mglevels[i+1]->restrct,dB,mglevels[i+1]->interpolate,MAT_INITIAL_MATRIX,1.0,&B);
    659:         }
    660:         KSPSetOperators(mglevels[i]->smoothd,B,B);
    661:         if (i != n-2) {PetscObjectDereference((PetscObject)dB);}
    662:         dB = B;
    663:       }
    664:       if (n > 1) {PetscObjectDereference((PetscObject)dB);}
    665:     } else {
    666:       for (i=n-2; i>-1; i--) {
    667:         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");
    668:         if (!mglevels[i+1]->interpolate) {
    669:           PCMGSetInterpolation(pc,i+1,mglevels[i+1]->restrct);
    670:         }
    671:         if (!mglevels[i+1]->restrct) {
    672:           PCMGSetRestriction(pc,i+1,mglevels[i+1]->interpolate);
    673:         }
    674:         KSPGetOperators(mglevels[i]->smoothd,NULL,&B);
    675:         if (mglevels[i+1]->interpolate == mglevels[i+1]->restrct) {
    676:           MatPtAP(dB,mglevels[i+1]->interpolate,MAT_REUSE_MATRIX,1.0,&B);
    677:         } else {
    678:           MatMatMatMult(mglevels[i+1]->restrct,dB,mglevels[i+1]->interpolate,MAT_REUSE_MATRIX,1.0,&B);
    679:         }
    680:         KSPSetOperators(mglevels[i]->smoothd,B,B);
    681:         dB   = B;
    682:       }
    683:     }
    684:   } else if (!mg->galerkin && pc->dm && pc->dm->x) {
    685:     /* need to restrict Jacobian location to coarser meshes for evaluation */
    686:     for (i=n-2; i>-1; i--) {
    687:       Mat R;
    688:       Vec rscale;
    689:       if (!mglevels[i]->smoothd->dm->x) {
    690:         Vec *vecs;
    691:         KSPCreateVecs(mglevels[i]->smoothd,1,&vecs,0,NULL);

    693:         mglevels[i]->smoothd->dm->x = vecs[0];

    695:         PetscFree(vecs);
    696:       }
    697:       PCMGGetRestriction(pc,i+1,&R);
    698:       PCMGGetRScale(pc,i+1,&rscale);
    699:       MatRestrict(R,mglevels[i+1]->smoothd->dm->x,mglevels[i]->smoothd->dm->x);
    700:       VecPointwiseMult(mglevels[i]->smoothd->dm->x,mglevels[i]->smoothd->dm->x,rscale);
    701:     }
    702:   }
    703:   if (!mg->galerkin && pc->dm) {
    704:     for (i=n-2; i>=0; i--) {
    705:       DM  dmfine,dmcoarse;
    706:       Mat Restrict,Inject;
    707:       Vec rscale;
    708:       KSPGetDM(mglevels[i+1]->smoothd,&dmfine);
    709:       KSPGetDM(mglevels[i]->smoothd,&dmcoarse);
    710:       PCMGGetRestriction(pc,i+1,&Restrict);
    711:       PCMGGetRScale(pc,i+1,&rscale);
    712:       Inject = NULL;      /* Callback should create it if it needs Injection */
    713:       DMRestrict(dmfine,Restrict,rscale,Inject,dmcoarse);
    714:     }
    715:   }

    717:   if (!pc->setupcalled) {
    718:     for (i=0; i<n; i++) {
    719:       KSPSetFromOptions(mglevels[i]->smoothd);
    720:     }
    721:     for (i=1; i<n; i++) {
    722:       if (mglevels[i]->smoothu && (mglevels[i]->smoothu != mglevels[i]->smoothd)) {
    723:         KSPSetFromOptions(mglevels[i]->smoothu);
    724:       }
    725:     }
    726:     for (i=1; i<n; i++) {
    727:       PCMGGetInterpolation(pc,i,&mglevels[i]->interpolate);
    728:       PCMGGetRestriction(pc,i,&mglevels[i]->restrct);
    729:     }
    730:     for (i=0; i<n-1; i++) {
    731:       if (!mglevels[i]->b) {
    732:         Vec *vec;
    733:         KSPCreateVecs(mglevels[i]->smoothd,1,&vec,0,NULL);
    734:         PCMGSetRhs(pc,i,*vec);
    735:         VecDestroy(vec);
    736:         PetscFree(vec);
    737:       }
    738:       if (!mglevels[i]->r && i) {
    739:         VecDuplicate(mglevels[i]->b,&tvec);
    740:         PCMGSetR(pc,i,tvec);
    741:         VecDestroy(&tvec);
    742:       }
    743:       if (!mglevels[i]->x) {
    744:         VecDuplicate(mglevels[i]->b,&tvec);
    745:         PCMGSetX(pc,i,tvec);
    746:         VecDestroy(&tvec);
    747:       }
    748:     }
    749:     if (n != 1 && !mglevels[n-1]->r) {
    750:       /* PCMGSetR() on the finest level if user did not supply it */
    751:       Vec *vec;
    752:       KSPCreateVecs(mglevels[n-1]->smoothd,1,&vec,0,NULL);
    753:       PCMGSetR(pc,n-1,*vec);
    754:       VecDestroy(vec);
    755:       PetscFree(vec);
    756:     }
    757:   }

    759:   if (pc->dm) {
    760:     /* need to tell all the coarser levels to rebuild the matrix using the DM for that level */
    761:     for (i=0; i<n-1; i++) {
    762:       if (mglevels[i]->smoothd->setupstage != KSP_SETUP_NEW) mglevels[i]->smoothd->setupstage = KSP_SETUP_NEWMATRIX;
    763:     }
    764:   }

    766:   for (i=1; i<n; i++) {
    767:     if (mglevels[i]->smoothu == mglevels[i]->smoothd || mg->am == PC_MG_FULL || mg->am == PC_MG_KASKADE || mg->cyclesperpcapply > 1){
    768:       /* if doing only down then initial guess is zero */
    769:       KSPSetInitialGuessNonzero(mglevels[i]->smoothd,PETSC_TRUE);
    770:     }
    771:     if (mglevels[i]->eventsmoothsetup) {PetscLogEventBegin(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    772:     KSPSetUp(mglevels[i]->smoothd);
    773:     if (mglevels[i]->eventsmoothsetup) {PetscLogEventEnd(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    774:     if (!mglevels[i]->residual) {
    775:       Mat mat;
    776:       KSPGetOperators(mglevels[i]->smoothd,NULL,&mat);
    777:       PCMGSetResidual(pc,i,PCMGResidualDefault,mat);
    778:     }
    779:   }
    780:   for (i=1; i<n; i++) {
    781:     if (mglevels[i]->smoothu && mglevels[i]->smoothu != mglevels[i]->smoothd) {
    782:       Mat          downmat,downpmat;

    784:       /* check if operators have been set for up, if not use down operators to set them */
    785:       KSPGetOperatorsSet(mglevels[i]->smoothu,&opsset,NULL);
    786:       if (!opsset) {
    787:         KSPGetOperators(mglevels[i]->smoothd,&downmat,&downpmat);
    788:         KSPSetOperators(mglevels[i]->smoothu,downmat,downpmat);
    789:       }

    791:       KSPSetInitialGuessNonzero(mglevels[i]->smoothu,PETSC_TRUE);
    792:       if (mglevels[i]->eventsmoothsetup) {PetscLogEventBegin(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    793:       KSPSetUp(mglevels[i]->smoothu);
    794:       if (mglevels[i]->eventsmoothsetup) {PetscLogEventEnd(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    795:     }
    796:   }

    798:   /*
    799:       If coarse solver is not direct method then DO NOT USE preonly
    800:   */
    801:   PetscObjectTypeCompare((PetscObject)mglevels[0]->smoothd,KSPPREONLY,&preonly);
    802:   if (preonly) {
    803:     PetscObjectTypeCompare((PetscObject)cpc,PCLU,&lu);
    804:     PetscObjectTypeCompare((PetscObject)cpc,PCREDUNDANT,&redundant);
    805:     PetscObjectTypeCompare((PetscObject)cpc,PCCHOLESKY,&cholesky);
    806:     PetscObjectTypeCompare((PetscObject)cpc,PCSVD,&svd);
    807:     if (!lu && !redundant && !cholesky && !svd) {
    808:       KSPSetType(mglevels[0]->smoothd,KSPGMRES);
    809:     }
    810:   }

    812:   if (mglevels[0]->eventsmoothsetup) {PetscLogEventBegin(mglevels[0]->eventsmoothsetup,0,0,0,0);}
    813:   KSPSetUp(mglevels[0]->smoothd);
    814:   if (mglevels[0]->eventsmoothsetup) {PetscLogEventEnd(mglevels[0]->eventsmoothsetup,0,0,0,0);}

    816:   /*
    817:      Dump the interpolation/restriction matrices plus the
    818:    Jacobian/stiffness on each level. This allows MATLAB users to
    819:    easily check if the Galerkin condition A_c = R A_f R^T is satisfied.

    821:    Only support one or the other at the same time.
    822:   */
    823: #if defined(PETSC_USE_SOCKET_VIEWER)
    824:   PetscOptionsGetBool(((PetscObject)pc)->prefix,"-pc_mg_dump_matlab",&dump,NULL);
    825:   if (dump) viewer = PETSC_VIEWER_SOCKET_(PetscObjectComm((PetscObject)pc));
    826:   dump = PETSC_FALSE;
    827: #endif
    828:   PetscOptionsGetBool(((PetscObject)pc)->prefix,"-pc_mg_dump_binary",&dump,NULL);
    829:   if (dump) viewer = PETSC_VIEWER_BINARY_(PetscObjectComm((PetscObject)pc));

    831:   if (viewer) {
    832:     for (i=1; i<n; i++) {
    833:       MatView(mglevels[i]->restrct,viewer);
    834:     }
    835:     for (i=0; i<n; i++) {
    836:       KSPGetPC(mglevels[i]->smoothd,&pc);
    837:       MatView(pc->mat,viewer);
    838:     }
    839:   }
    840:   return(0);
    841: }

    843: /* -------------------------------------------------------------------------------------*/

    847: /*@
    848:    PCMGGetLevels - Gets the number of levels to use with MG.

    850:    Not Collective

    852:    Input Parameter:
    853: .  pc - the preconditioner context

    855:    Output parameter:
    856: .  levels - the number of levels

    858:    Level: advanced

    860: .keywords: MG, get, levels, multigrid

    862: .seealso: PCMGSetLevels()
    863: @*/
    864: PetscErrorCode  PCMGGetLevels(PC pc,PetscInt *levels)
    865: {
    866:   PC_MG *mg = (PC_MG*)pc->data;

    871:   *levels = mg->nlevels;
    872:   return(0);
    873: }

    877: /*@
    878:    PCMGSetType - Determines the form of multigrid to use:
    879:    multiplicative, additive, full, or the Kaskade algorithm.

    881:    Logically Collective on PC

    883:    Input Parameters:
    884: +  pc - the preconditioner context
    885: -  form - multigrid form, one of PC_MG_MULTIPLICATIVE, PC_MG_ADDITIVE,
    886:    PC_MG_FULL, PC_MG_KASKADE

    888:    Options Database Key:
    889: .  -pc_mg_type <form> - Sets <form>, one of multiplicative,
    890:    additive, full, kaskade

    892:    Level: advanced

    894: .keywords: MG, set, method, multiplicative, additive, full, Kaskade, multigrid

    896: .seealso: PCMGSetLevels()
    897: @*/
    898: PetscErrorCode  PCMGSetType(PC pc,PCMGType form)
    899: {
    900:   PC_MG *mg = (PC_MG*)pc->data;

    905:   mg->am = form;
    906:   if (form == PC_MG_MULTIPLICATIVE) pc->ops->applyrichardson = PCApplyRichardson_MG;
    907:   else pc->ops->applyrichardson = NULL;
    908:   return(0);
    909: }

    913: /*@
    914:    PCMGGetType - Determines the form of multigrid to use:
    915:    multiplicative, additive, full, or the Kaskade algorithm.

    917:    Logically Collective on PC

    919:    Input Parameter:
    920: .  pc - the preconditioner context

    922:    Output Parameter:
    923: .  type - one of PC_MG_MULTIPLICATIVE, PC_MG_ADDITIVE,PC_MG_FULL, PC_MG_KASKADE

    926:    Level: advanced

    928: .keywords: MG, set, method, multiplicative, additive, full, Kaskade, multigrid

    930: .seealso: PCMGSetLevels()
    931: @*/
    932: PetscErrorCode  PCMGGetType(PC pc,PCMGType *type)
    933: {
    934:   PC_MG *mg = (PC_MG*)pc->data;

    938:   *type = mg->am;
    939:   return(0);
    940: }

    944: /*@
    945:    PCMGSetCycleType - Sets the type cycles to use.  Use PCMGSetCycleTypeOnLevel() for more
    946:    complicated cycling.

    948:    Logically Collective on PC

    950:    Input Parameters:
    951: +  pc - the multigrid context
    952: -  PC_MG_CYCLE_V or PC_MG_CYCLE_W

    954:    Options Database Key:
    955: .  -pc_mg_cycle_type <v,w>

    957:    Level: advanced

    959: .keywords: MG, set, cycles, V-cycle, W-cycle, multigrid

    961: .seealso: PCMGSetCycleTypeOnLevel()
    962: @*/
    963: PetscErrorCode  PCMGSetCycleType(PC pc,PCMGCycleType n)
    964: {
    965:   PC_MG        *mg        = (PC_MG*)pc->data;
    966:   PC_MG_Levels **mglevels = mg->levels;
    967:   PetscInt     i,levels;

    971:   if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONGSTATE,"Must set MG levels before calling");
    973:   levels = mglevels[0]->levels;

    975:   for (i=0; i<levels; i++) mglevels[i]->cycles = n;
    976:   return(0);
    977: }

    981: /*@
    982:    PCMGMultiplicativeSetCycles - Sets the number of cycles to use for each preconditioner step
    983:          of multigrid when PCMGType of PC_MG_MULTIPLICATIVE is used

    985:    Logically Collective on PC

    987:    Input Parameters:
    988: +  pc - the multigrid context
    989: -  n - number of cycles (default is 1)

    991:    Options Database Key:
    992: .  -pc_mg_multiplicative_cycles n

    994:    Level: advanced

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

    998: .keywords: MG, set, cycles, V-cycle, W-cycle, multigrid

    1000: .seealso: PCMGSetCycleTypeOnLevel(), PCMGSetCycleType()
    1001: @*/
    1002: PetscErrorCode  PCMGMultiplicativeSetCycles(PC pc,PetscInt n)
    1003: {
    1004:   PC_MG        *mg        = (PC_MG*)pc->data;

    1009:   mg->cyclesperpcapply = n;
    1010:   return(0);
    1011: }

    1015: PetscErrorCode PCMGSetGalerkin_MG(PC pc,PetscBool use)
    1016: {
    1017:   PC_MG *mg = (PC_MG*)pc->data;

    1020:   mg->galerkin = use ? 1 : 0;
    1021:   return(0);
    1022: }

    1026: /*@
    1027:    PCMGSetGalerkin - Causes the coarser grid matrices to be computed from the
    1028:       finest grid via the Galerkin process: A_i-1 = r_i * A_i * p_i

    1030:    Logically Collective on PC

    1032:    Input Parameters:
    1033: +  pc - the multigrid context
    1034: -  use - PETSC_TRUE to use the Galerkin process to compute coarse-level operators

    1036:    Options Database Key:
    1037: .  -pc_mg_galerkin <true,false>

    1039:    Level: intermediate

    1041:    Notes: Some codes that use PCMG such as PCGAMG use Galerkin internally while constructing the hierarchy and thus do not
    1042:      use the PCMG construction of the coarser grids.

    1044: .keywords: MG, set, Galerkin

    1046: .seealso: PCMGGetGalerkin()

    1048: @*/
    1049: PetscErrorCode PCMGSetGalerkin(PC pc,PetscBool use)
    1050: {

    1055:   PetscTryMethod(pc,"PCMGSetGalerkin_C",(PC,PetscBool),(pc,use));
    1056:   return(0);
    1057: }

    1061: /*@
    1062:    PCMGGetGalerkin - Checks if Galerkin multigrid is being used, i.e.
    1063:       A_i-1 = r_i * A_i * p_i

    1065:    Not Collective

    1067:    Input Parameter:
    1068: .  pc - the multigrid context

    1070:    Output Parameter:
    1071: .  galerkin - PETSC_TRUE or PETSC_FALSE

    1073:    Options Database Key:
    1074: .  -pc_mg_galerkin

    1076:    Level: intermediate

    1078: .keywords: MG, set, Galerkin

    1080: .seealso: PCMGSetGalerkin()

    1082: @*/
    1083: PetscErrorCode  PCMGGetGalerkin(PC pc,PetscBool  *galerkin)
    1084: {
    1085:   PC_MG *mg = (PC_MG*)pc->data;

    1089:   *galerkin = (PetscBool)mg->galerkin;
    1090:   return(0);
    1091: }

    1095: /*@
    1096:    PCMGSetNumberSmoothDown - Sets the number of pre-smoothing steps to
    1097:    use on all levels. Use PCMGGetSmootherDown() to set different
    1098:    pre-smoothing steps on different levels.

    1100:    Logically Collective on PC

    1102:    Input Parameters:
    1103: +  mg - the multigrid context
    1104: -  n - the number of smoothing steps

    1106:    Options Database Key:
    1107: .  -pc_mg_smoothdown <n> - Sets number of pre-smoothing steps

    1109:    Level: advanced

    1111: .keywords: MG, smooth, down, pre-smoothing, steps, multigrid

    1113: .seealso: PCMGSetNumberSmoothUp()
    1114: @*/
    1115: PetscErrorCode  PCMGSetNumberSmoothDown(PC pc,PetscInt n)
    1116: {
    1117:   PC_MG          *mg        = (PC_MG*)pc->data;
    1118:   PC_MG_Levels   **mglevels = mg->levels;
    1120:   PetscInt       i,levels;

    1124:   if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONGSTATE,"Must set MG levels before calling");
    1126:   levels = mglevels[0]->levels;

    1128:   for (i=1; i<levels; i++) {
    1129:     /* make sure smoother up and down are different */
    1130:     PCMGGetSmootherUp(pc,i,NULL);
    1131:     KSPSetTolerances(mglevels[i]->smoothd,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT,n);

    1133:     mg->default_smoothd = n;
    1134:   }
    1135:   return(0);
    1136: }

    1140: /*@
    1141:    PCMGSetNumberSmoothUp - Sets the number of post-smoothing steps to use
    1142:    on all levels. Use PCMGGetSmootherUp() to set different numbers of
    1143:    post-smoothing steps on different levels.

    1145:    Logically Collective on PC

    1147:    Input Parameters:
    1148: +  mg - the multigrid context
    1149: -  n - the number of smoothing steps

    1151:    Options Database Key:
    1152: .  -pc_mg_smoothup <n> - Sets number of post-smoothing steps

    1154:    Level: advanced

    1156:    Note: this does not set a value on the coarsest grid, since we assume that
    1157:     there is no separate smooth up on the coarsest grid.

    1159: .keywords: MG, smooth, up, post-smoothing, steps, multigrid

    1161: .seealso: PCMGSetNumberSmoothDown()
    1162: @*/
    1163: PetscErrorCode  PCMGSetNumberSmoothUp(PC pc,PetscInt n)
    1164: {
    1165:   PC_MG          *mg        = (PC_MG*)pc->data;
    1166:   PC_MG_Levels   **mglevels = mg->levels;
    1168:   PetscInt       i,levels;

    1172:   if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONGSTATE,"Must set MG levels before calling");
    1174:   levels = mglevels[0]->levels;

    1176:   for (i=1; i<levels; i++) {
    1177:     /* make sure smoother up and down are different */
    1178:     PCMGGetSmootherUp(pc,i,NULL);
    1179:     KSPSetTolerances(mglevels[i]->smoothu,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT,n);

    1181:     mg->default_smoothu = n;
    1182:   }
    1183:   return(0);
    1184: }

    1186: /* ----------------------------------------------------------------------------------------*/

    1188: /*MC
    1189:    PCMG - Use multigrid preconditioning. This preconditioner requires you provide additional
    1190:     information about the coarser grid matrices and restriction/interpolation operators.

    1192:    Options Database Keys:
    1193: +  -pc_mg_levels <nlevels> - number of levels including finest
    1194: .  -pc_mg_cycles <v,w> -
    1195: .  -pc_mg_smoothup <n> - number of smoothing steps after interpolation
    1196: .  -pc_mg_smoothdown <n> - number of smoothing steps before applying restriction operator
    1197: .  -pc_mg_type <additive,multiplicative,full,kaskade> - multiplicative is the default
    1198: .  -pc_mg_log - log information about time spent on each level of the solver
    1199: .  -pc_mg_galerkin - use Galerkin process to compute coarser operators, i.e. Acoarse = R A R'
    1200: .  -pc_mg_multiplicative_cycles - number of cycles to use as the preconditioner (defaults to 1)
    1201: .  -pc_mg_dump_matlab - dumps the matrices for each level and the restriction/interpolation matrices
    1202:                         to the Socket viewer for reading from MATLAB.
    1203: -  -pc_mg_dump_binary - dumps the matrices for each level and the restriction/interpolation matrices
    1204:                         to the binary output file called binaryoutput

    1206:    Notes: By default this uses GMRES on the fine grid smoother so this should be used with KSPFGMRES or the smoother changed to not use GMRES

    1208:        When run with a single level the smoother options are used on that level NOT the coarse grid solver options

    1210:    Level: intermediate

    1212:    Concepts: multigrid/multilevel

    1214: .seealso:  PCCreate(), PCSetType(), PCType (for list of available types), PC, PCMGType, PCEXOTIC, PCGAMG, PCML, PCHYPRE
    1215:            PCMGSetLevels(), PCMGGetLevels(), PCMGSetType(), PCMGSetCycleType(), PCMGSetNumberSmoothDown(),
    1216:            PCMGSetNumberSmoothUp(), PCMGGetCoarseSolve(), PCMGSetResidual(), PCMGSetInterpolation(),
    1217:            PCMGSetRestriction(), PCMGGetSmoother(), PCMGGetSmootherUp(), PCMGGetSmootherDown(),
    1218:            PCMGSetCycleTypeOnLevel(), PCMGSetRhs(), PCMGSetX(), PCMGSetR()
    1219: M*/

    1223: PETSC_EXTERN PetscErrorCode PCCreate_MG(PC pc)
    1224: {
    1225:   PC_MG          *mg;

    1229:   PetscNewLog(pc,&mg);
    1230:   pc->data    = (void*)mg;
    1231:   mg->nlevels = -1;
    1232:   mg->am      = PC_MG_MULTIPLICATIVE;

    1234:   pc->useAmat = PETSC_TRUE;

    1236:   pc->ops->apply          = PCApply_MG;
    1237:   pc->ops->setup          = PCSetUp_MG;
    1238:   pc->ops->reset          = PCReset_MG;
    1239:   pc->ops->destroy        = PCDestroy_MG;
    1240:   pc->ops->setfromoptions = PCSetFromOptions_MG;
    1241:   pc->ops->view           = PCView_MG;

    1243:   PetscObjectComposeFunction((PetscObject)pc,"PCMGSetGalerkin_C",PCMGSetGalerkin_MG);
    1244:   return(0);
    1245: }