Date: 2013-07-02T14:46:38+00:00

Actual source code: mg.c
petsc-3.4.2 2013-07-02

      2: /*
      3:     Defines the multigrid preconditioner interface.
      4: */
      5: #include <../src/ksp/pc/impls/mg/mgimpl.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",rnorm,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",rnorm,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:   mglevels[levels-1]->b = b;
     71:   mglevels[levels-1]->x = x;

     73:   mg->rtol   = rtol;
     74:   mg->abstol = abstol;
     75:   mg->dtol   = dtol;
     76:   if (rtol) {
     77:     /* compute initial residual norm for relative convergence test */
     78:     PetscReal rnorm;
     79:     if (zeroguess) {
     80:       VecNorm(b,NORM_2,&rnorm);
     81:     } else {
     82:       (*mglevels[levels-1]->residual)(mglevels[levels-1]->A,b,x,w);
     83:       VecNorm(w,NORM_2,&rnorm);
     84:     }
     85:     mg->ttol = PetscMax(rtol*rnorm,abstol);
     86:   } else if (abstol) mg->ttol = abstol;
     87:   else mg->ttol = 0.0;

     89:   /* since smoother is applied to full system, not just residual we need to make sure that smoothers don't
     90:      stop prematurely due to small residual */
     91:   for (i=1; i<levels; i++) {
     92:     KSPSetTolerances(mglevels[i]->smoothu,0,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);
     93:     if (mglevels[i]->smoothu != mglevels[i]->smoothd) {
     94:       KSPSetTolerances(mglevels[i]->smoothd,0,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);
     95:     }
     96:   }

     98:   *reason = (PCRichardsonConvergedReason)0;
     99:   for (i=0; i<its; i++) {
    100:     PCMGMCycle_Private(pc,mglevels+levels-1,reason);
    101:     if (*reason) break;
    102:   }
    103:   if (!*reason) *reason = PCRICHARDSON_CONVERGED_ITS;
    104:   *outits = i;
    105:   return(0);
    106: }

    110: PetscErrorCode PCReset_MG(PC pc)
    111: {
    112:   PC_MG          *mg        = (PC_MG*)pc->data;
    113:   PC_MG_Levels   **mglevels = mg->levels;
    115:   PetscInt       i,n;

    118:   if (mglevels) {
    119:     n = mglevels[0]->levels;
    120:     for (i=0; i<n-1; i++) {
    121:       VecDestroy(&mglevels[i+1]->r);
    122:       VecDestroy(&mglevels[i]->b);
    123:       VecDestroy(&mglevels[i]->x);
    124:       MatDestroy(&mglevels[i+1]->restrct);
    125:       MatDestroy(&mglevels[i+1]->interpolate);
    126:       VecDestroy(&mglevels[i+1]->rscale);
    127:     }

    129:     for (i=0; i<n; i++) {
    130:       MatDestroy(&mglevels[i]->A);
    131:       if (mglevels[i]->smoothd != mglevels[i]->smoothu) {
    132:         KSPReset(mglevels[i]->smoothd);
    133:       }
    134:       KSPReset(mglevels[i]->smoothu);
    135:     }
    136:   }
    137:   return(0);
    138: }

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

    146:    Logically Collective on PC

    148:    Input Parameters:
    149: +  pc - the preconditioner context
    150: .  levels - the number of levels
    151: -  comms - optional communicators for each level; this is to allow solving the coarser problems
    152:            on smaller sets of processors. Use NULL_OBJECT for default in Fortran

    154:    Level: intermediate

    156:    Notes:
    157:      If the number of levels is one then the multigrid uses the -mg_levels prefix
    158:   for setting the level options rather than the -mg_coarse prefix.

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

    162: .seealso: PCMGSetType(), PCMGGetLevels()
    163: @*/
    164: PetscErrorCode  PCMGSetLevels(PC pc,PetscInt levels,MPI_Comm *comms)
    165: {
    167:   PC_MG          *mg        = (PC_MG*)pc->data;
    168:   MPI_Comm       comm;
    169:   PC_MG_Levels   **mglevels = mg->levels;
    170:   PetscInt       i;
    171:   PetscMPIInt    size;
    172:   const char     *prefix;
    173:   PC             ipc;
    174:   PetscInt       n;

    179:   PetscObjectGetComm((PetscObject)pc,&comm);
    180:   if (mg->nlevels == levels) return(0);
    181:   if (mglevels) {
    182:     /* changing the number of levels so free up the previous stuff */
    183:     PCReset_MG(pc);
    184:     n    = mglevels[0]->levels;
    185:     for (i=0; i<n; i++) {
    186:       if (mglevels[i]->smoothd != mglevels[i]->smoothu) {
    187:         KSPDestroy(&mglevels[i]->smoothd);
    188:       }
    189:       KSPDestroy(&mglevels[i]->smoothu);
    190:       PetscFree(mglevels[i]);
    191:     }
    192:     PetscFree(mg->levels);
    193:   }

    195:   mg->nlevels = levels;

    197:   PetscMalloc(levels*sizeof(PC_MG*),&mglevels);
    198:   PetscLogObjectMemory(pc,levels*(sizeof(PC_MG*)));

    200:   PCGetOptionsPrefix(pc,&prefix);

    202:   mg->stageApply = 0;
    203:   for (i=0; i<levels; i++) {
    204:     PetscNewLog(pc,PC_MG_Levels,&mglevels[i]);

    206:     mglevels[i]->level               = i;
    207:     mglevels[i]->levels              = levels;
    208:     mglevels[i]->cycles              = PC_MG_CYCLE_V;
    209:     mg->default_smoothu              = 2;
    210:     mg->default_smoothd              = 2;
    211:     mglevels[i]->eventsmoothsetup    = 0;
    212:     mglevels[i]->eventsmoothsolve    = 0;
    213:     mglevels[i]->eventresidual       = 0;
    214:     mglevels[i]->eventinterprestrict = 0;

    216:     if (comms) comm = comms[i];
    217:     KSPCreate(comm,&mglevels[i]->smoothd);
    218:     KSPSetType(mglevels[i]->smoothd,KSPCHEBYSHEV);
    219:     KSPSetConvergenceTest(mglevels[i]->smoothd,KSPSkipConverged,NULL,NULL);
    220:     KSPSetNormType(mglevels[i]->smoothd,KSP_NORM_NONE);
    221:     KSPGetPC(mglevels[i]->smoothd,&ipc);
    222:     PCSetType(ipc,PCSOR);
    223:     PetscObjectIncrementTabLevel((PetscObject)mglevels[i]->smoothd,(PetscObject)pc,levels-i);
    224:     KSPSetTolerances(mglevels[i]->smoothd,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT, i ? mg->default_smoothd : 1);
    225:     KSPSetOptionsPrefix(mglevels[i]->smoothd,prefix);

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

    231:       /* coarse solve is (redundant) LU by default; set shifttype NONZERO to avoid annoying zero-pivot in LU preconditioner */
    232:       KSPSetType(mglevels[0]->smoothd,KSPPREONLY);
    233:       KSPGetPC(mglevels[0]->smoothd,&ipc);
    234:       MPI_Comm_size(comm,&size);
    235:       if (size > 1) {
    236:         KSP innerksp;
    237:         PC  innerpc;
    238:         PCSetType(ipc,PCREDUNDANT);
    239:         PCRedundantGetKSP(ipc,&innerksp);
    240:         KSPGetPC(innerksp,&innerpc);
    241:         PCFactorSetShiftType(innerpc,MAT_SHIFT_INBLOCKS);
    242:       } else {
    243:         PCSetType(ipc,PCLU);
    244:         PCFactorSetShiftType(ipc,MAT_SHIFT_INBLOCKS);
    245:       }
    246:     } else {
    247:       char tprefix[128];
    248:       sprintf(tprefix,"mg_levels_%d_",(int)i);
    249:       KSPAppendOptionsPrefix(mglevels[i]->smoothd,tprefix);
    250:     }
    251:     PetscLogObjectParent(pc,mglevels[i]->smoothd);

    253:     mglevels[i]->smoothu = mglevels[i]->smoothd;
    254:     mg->rtol             = 0.0;
    255:     mg->abstol           = 0.0;
    256:     mg->dtol             = 0.0;
    257:     mg->ttol             = 0.0;
    258:     mg->cyclesperpcapply = 1;
    259:   }
    260:   mg->am                   = PC_MG_MULTIPLICATIVE;
    261:   mg->levels               = mglevels;
    262:   pc->ops->applyrichardson = PCApplyRichardson_MG;
    263:   return(0);
    264: }

    269: PetscErrorCode PCDestroy_MG(PC pc)
    270: {
    272:   PC_MG          *mg        = (PC_MG*)pc->data;
    273:   PC_MG_Levels   **mglevels = mg->levels;
    274:   PetscInt       i,n;

    277:   PCReset_MG(pc);
    278:   if (mglevels) {
    279:     n = mglevels[0]->levels;
    280:     for (i=0; i<n; i++) {
    281:       if (mglevels[i]->smoothd != mglevels[i]->smoothu) {
    282:         KSPDestroy(&mglevels[i]->smoothd);
    283:       }
    284:       KSPDestroy(&mglevels[i]->smoothu);
    285:       PetscFree(mglevels[i]);
    286:     }
    287:     PetscFree(mg->levels);
    288:   }
    289:   PetscFree(pc->data);
    290:   return(0);
    291: }

    295: extern PetscErrorCode PCMGACycle_Private(PC,PC_MG_Levels**);
    296: extern PetscErrorCode PCMGFCycle_Private(PC,PC_MG_Levels**);
    297: extern PetscErrorCode PCMGKCycle_Private(PC,PC_MG_Levels**);

    299: /*
    300:    PCApply_MG - Runs either an additive, multiplicative, Kaskadic
    301:              or full cycle of multigrid.

    303:   Note:
    304:   A simple wrapper which calls PCMGMCycle(),PCMGACycle(), or PCMGFCycle().
    305: */
    308: static PetscErrorCode PCApply_MG(PC pc,Vec b,Vec x)
    309: {
    310:   PC_MG          *mg        = (PC_MG*)pc->data;
    311:   PC_MG_Levels   **mglevels = mg->levels;
    313:   PetscInt       levels = mglevels[0]->levels,i;

    316:   if (mg->stageApply) {PetscLogStagePush(mg->stageApply);}
    317:   /* When the DM is supplying the matrix then it will not exist until here */
    318:   for (i=0; i<levels; i++) {
    319:     if (!mglevels[i]->A) {
    320:       KSPGetOperators(mglevels[i]->smoothu,&mglevels[i]->A,NULL,NULL);
    321:       PetscObjectReference((PetscObject)mglevels[i]->A);
    322:     }
    323:   }

    325:   mglevels[levels-1]->b = b;
    326:   mglevels[levels-1]->x = x;
    327:   if (mg->am == PC_MG_MULTIPLICATIVE) {
    328:     VecSet(x,0.0);
    329:     for (i=0; i<mg->cyclesperpcapply; i++) {
    330:       PCMGMCycle_Private(pc,mglevels+levels-1,NULL);
    331:     }
    332:   } else if (mg->am == PC_MG_ADDITIVE) {
    333:     PCMGACycle_Private(pc,mglevels);
    334:   } else if (mg->am == PC_MG_KASKADE) {
    335:     PCMGKCycle_Private(pc,mglevels);
    336:   } else {
    337:     PCMGFCycle_Private(pc,mglevels);
    338:   }
    339:   if (mg->stageApply) {PetscLogStagePop();}
    340:   return(0);
    341: }

    346: PetscErrorCode PCSetFromOptions_MG(PC pc)
    347: {
    349:   PetscInt       m,levels = 1,cycles;
    350:   PetscBool      flg,set;
    351:   PC_MG          *mg        = (PC_MG*)pc->data;
    352:   PC_MG_Levels   **mglevels = mg->levels;
    353:   PCMGType       mgtype;
    354:   PCMGCycleType  mgctype;

    357:   PetscOptionsHead("Multigrid options");
    358:   if (!mg->levels) {
    359:     PetscOptionsInt("-pc_mg_levels","Number of Levels","PCMGSetLevels",levels,&levels,&flg);
    360:     if (!flg && pc->dm) {
    361:       DMGetRefineLevel(pc->dm,&levels);
    362:       levels++;
    363:       mg->usedmfornumberoflevels = PETSC_TRUE;
    364:     }
    365:     PCMGSetLevels(pc,levels,NULL);
    366:   }
    367:   mglevels = mg->levels;

    369:   mgctype = (PCMGCycleType) mglevels[0]->cycles;
    370:   PetscOptionsEnum("-pc_mg_cycle_type","V cycle or for W-cycle","PCMGSetCycleType",PCMGCycleTypes,(PetscEnum)mgctype,(PetscEnum*)&mgctype,&flg);
    371:   if (flg) {
    372:     PCMGSetCycleType(pc,mgctype);
    373:   }
    374:   flg  = PETSC_FALSE;
    375:   PetscOptionsBool("-pc_mg_galerkin","Use Galerkin process to compute coarser operators","PCMGSetGalerkin",flg,&flg,&set);
    376:   if (set) {
    377:     PCMGSetGalerkin(pc,flg);
    378:   }
    379:   PetscOptionsInt("-pc_mg_smoothup","Number of post-smoothing steps","PCMGSetNumberSmoothUp",1,&m,&flg);
    380:   if (flg) {
    381:     PCMGSetNumberSmoothUp(pc,m);
    382:   }
    383:   PetscOptionsInt("-pc_mg_smoothdown","Number of pre-smoothing steps","PCMGSetNumberSmoothDown",1,&m,&flg);
    384:   if (flg) {
    385:     PCMGSetNumberSmoothDown(pc,m);
    386:   }
    387:   mgtype = mg->am;
    388:   PetscOptionsEnum("-pc_mg_type","Multigrid type","PCMGSetType",PCMGTypes,(PetscEnum)mgtype,(PetscEnum*)&mgtype,&flg);
    389:   if (flg) {
    390:     PCMGSetType(pc,mgtype);
    391:   }
    392:   if (mg->am == PC_MG_MULTIPLICATIVE) {
    393:     PetscOptionsInt("-pc_mg_multiplicative_cycles","Number of cycles for each preconditioner step","PCMGSetLevels",mg->cyclesperpcapply,&cycles,&flg);
    394:     if (flg) {
    395:       PCMGMultiplicativeSetCycles(pc,cycles);
    396:     }
    397:   }
    398:   flg  = PETSC_FALSE;
    399:   PetscOptionsBool("-pc_mg_log","Log times for each multigrid level","None",flg,&flg,NULL);
    400:   if (flg) {
    401:     PetscInt i;
    402:     char     eventname[128];
    403:     if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONGSTATE,"Must set MG levels before calling");
    404:     levels = mglevels[0]->levels;
    405:     for (i=0; i<levels; i++) {
    406:       sprintf(eventname,"MGSetup Level %d",(int)i);
    407:       PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventsmoothsetup);
    408:       sprintf(eventname,"MGSmooth Level %d",(int)i);
    409:       PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventsmoothsolve);
    410:       if (i) {
    411:         sprintf(eventname,"MGResid Level %d",(int)i);
    412:         PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventresidual);
    413:         sprintf(eventname,"MGInterp Level %d",(int)i);
    414:         PetscLogEventRegister(eventname,((PetscObject)pc)->classid,&mglevels[i]->eventinterprestrict);
    415:       }
    416:     }

    418: #if defined(PETSC_USE_LOG)
    419:     {
    420:       const char    *sname = "MG Apply";
    421:       PetscStageLog stageLog;
    422:       PetscInt      st;

    425:       PetscLogGetStageLog(&stageLog);
    426:       for (st = 0; st < stageLog->numStages; ++st) {
    427:         PetscBool same;

    429:         PetscStrcmp(stageLog->stageInfo[st].name, sname, &same);
    430:         if (same) mg->stageApply = st;
    431:       }
    432:       if (!mg->stageApply) {
    433:         PetscLogStageRegister(sname, &mg->stageApply);
    434:       }
    435:     }
    436: #endif
    437:   }
    438:   PetscOptionsTail();
    439:   return(0);
    440: }

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

    445: #include <petscdraw.h>
    448: PetscErrorCode PCView_MG(PC pc,PetscViewer viewer)
    449: {
    450:   PC_MG          *mg        = (PC_MG*)pc->data;
    451:   PC_MG_Levels   **mglevels = mg->levels;
    453:   PetscInt       levels = mglevels ? mglevels[0]->levels : 0,i;
    454:   PetscBool      iascii,isbinary,isdraw;

    457:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
    458:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);
    459:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERDRAW,&isdraw);
    460:   if (iascii) {
    461:     const char *cyclename = levels ? (mglevels[0]->cycles == PC_MG_CYCLE_V ? "v" : "w") : "unknown";
    462:     PetscViewerASCIIPrintf(viewer,"  MG: type is %s, levels=%D cycles=%s\n", PCMGTypes[mg->am],levels,cyclename);
    463:     if (mg->am == PC_MG_MULTIPLICATIVE) {
    464:       PetscViewerASCIIPrintf(viewer,"    Cycles per PCApply=%d\n",mg->cyclesperpcapply);
    465:     }
    466:     if (mg->galerkin) {
    467:       PetscViewerASCIIPrintf(viewer,"    Using Galerkin computed coarse grid matrices\n");
    468:     } else {
    469:       PetscViewerASCIIPrintf(viewer,"    Not using Galerkin computed coarse grid matrices\n");
    470:     }
    471:     for (i=0; i<levels; i++) {
    472:       if (!i) {
    473:         PetscViewerASCIIPrintf(viewer,"Coarse grid solver -- level -------------------------------\n",i);
    474:       } else {
    475:         PetscViewerASCIIPrintf(viewer,"Down solver (pre-smoother) on level %D -------------------------------\n",i);
    476:       }
    477:       PetscViewerASCIIPushTab(viewer);
    478:       KSPView(mglevels[i]->smoothd,viewer);
    479:       PetscViewerASCIIPopTab(viewer);
    480:       if (i && mglevels[i]->smoothd == mglevels[i]->smoothu) {
    481:         PetscViewerASCIIPrintf(viewer,"Up solver (post-smoother) same as down solver (pre-smoother)\n");
    482:       } else if (i) {
    483:         PetscViewerASCIIPrintf(viewer,"Up solver (post-smoother) on level %D -------------------------------\n",i);
    484:         PetscViewerASCIIPushTab(viewer);
    485:         KSPView(mglevels[i]->smoothu,viewer);
    486:         PetscViewerASCIIPopTab(viewer);
    487:       }
    488:     }
    489:   } else if (isbinary) {
    490:     for (i=levels-1; i>=0; i--) {
    491:       KSPView(mglevels[i]->smoothd,viewer);
    492:       if (i && mglevels[i]->smoothd != mglevels[i]->smoothu) {
    493:         KSPView(mglevels[i]->smoothu,viewer);
    494:       }
    495:     }
    496:   } else if (isdraw) {
    497:     PetscDraw draw;
    498:     PetscReal x,w,y,bottom,th;
    499:     PetscViewerDrawGetDraw(viewer,0,&draw);
    500:     PetscDrawGetCurrentPoint(draw,&x,&y);
    501:     PetscDrawStringGetSize(draw,NULL,&th);
    502:     bottom = y - th;
    503:     for (i=levels-1; i>=0; i--) {
    504:       if (!mglevels[i]->smoothu || (mglevels[i]->smoothu == mglevels[i]->smoothd)) {
    505:         PetscDrawPushCurrentPoint(draw,x,bottom);
    506:         KSPView(mglevels[i]->smoothd,viewer);
    507:         PetscDrawPopCurrentPoint(draw);
    508:       } else {
    509:         w    = 0.5*PetscMin(1.0-x,x);
    510:         PetscDrawPushCurrentPoint(draw,x+w,bottom);
    511:         KSPView(mglevels[i]->smoothd,viewer);
    512:         PetscDrawPopCurrentPoint(draw);
    513:         PetscDrawPushCurrentPoint(draw,x-w,bottom);
    514:         KSPView(mglevels[i]->smoothu,viewer);
    515:         PetscDrawPopCurrentPoint(draw);
    516:       }
    517:       PetscDrawGetBoundingBox(draw,NULL,&bottom,NULL,NULL);
    518:       bottom -= th;
    519:     }
    520:   }
    521:   return(0);
    522: }

    524: #include <petsc-private/dmimpl.h>
    525: #include <petsc-private/kspimpl.h>

    527: /*
    528:     Calls setup for the KSP on each level
    529: */
    532: PetscErrorCode PCSetUp_MG(PC pc)
    533: {
    534:   PC_MG          *mg        = (PC_MG*)pc->data;
    535:   PC_MG_Levels   **mglevels = mg->levels;
    537:   PetscInt       i,n = mglevels[0]->levels;
    538:   PC             cpc;
    539:   PetscBool      preonly,lu,redundant,cholesky,svd,dump = PETSC_FALSE,opsset,use_amat;
    540:   Mat            dA,dB;
    541:   MatStructure   uflag;
    542:   Vec            tvec;
    543:   DM             *dms;
    544:   PetscViewer    viewer = 0;

    547:   /* FIX: Move this to PCSetFromOptions_MG? */
    548:   if (mg->usedmfornumberoflevels) {
    549:     PetscInt levels;
    550:     DMGetRefineLevel(pc->dm,&levels);
    551:     levels++;
    552:     if (levels > n) { /* the problem is now being solved on a finer grid */
    553:       PCMGSetLevels(pc,levels,NULL);
    554:       n        = levels;
    555:       PCSetFromOptions(pc); /* it is bad to call this here, but otherwise will never be called for the new hierarchy */
    556:       mglevels =  mg->levels;
    557:     }
    558:   }
    559:   KSPGetPC(mglevels[0]->smoothd,&cpc);

    562:   /* If user did not provide fine grid operators OR operator was not updated since last global KSPSetOperators() */
    563:   /* so use those from global PC */
    564:   /* Is this what we always want? What if user wants to keep old one? */
    565:   KSPGetOperatorsSet(mglevels[n-1]->smoothd,NULL,&opsset);
    566:   if (opsset) {
    567:     Mat mmat;
    568:     KSPGetOperators(mglevels[n-1]->smoothd,NULL,&mmat,NULL);
    569:     if (mmat == pc->pmat) opsset = PETSC_FALSE;
    570:   }

    572:   if (!opsset) {
    573:     PCGetUseAmat(pc,&use_amat);
    574:     if(use_amat){
    575:       PetscInfo(pc,"Using outer operators to define finest grid operator \n  because PCMGGetSmoother(pc,nlevels-1,&ksp);KSPSetOperators(ksp,...); was not called.\n");
    576:       KSPSetOperators(mglevels[n-1]->smoothd,pc->mat,pc->pmat,pc->flag);
    577:     }
    578:     else {
    579:       PetscInfo(pc,"Using matrix (pmat) operators to define finest grid operator \n  because PCMGGetSmoother(pc,nlevels-1,&ksp);KSPSetOperators(ksp,...); was not called.\n");
    580:       KSPSetOperators(mglevels[n-1]->smoothd,pc->pmat,pc->pmat,pc->flag);
    581:     }
    582:   }

    584:   /* Skipping this for galerkin==2 (externally managed hierarchy such as ML and GAMG). Cleaner logic here would be great. Wrap ML/GAMG as DMs? */
    585:   if (pc->dm && mg->galerkin != 2 && !pc->setupcalled) {
    586:     /* construct the interpolation from the DMs */
    587:     Mat p;
    588:     Vec rscale;
    589:     PetscMalloc(n*sizeof(DM),&dms);
    590:     dms[n-1] = pc->dm;
    591:     for (i=n-2; i>-1; i--) {
    592:       DMKSP kdm;
    593:       DMCoarsen(dms[i+1],MPI_COMM_NULL,&dms[i]);
    594:       KSPSetDM(mglevels[i]->smoothd,dms[i]);
    595:       if (mg->galerkin) {KSPSetDMActive(mglevels[i]->smoothd,PETSC_FALSE);}
    596:       DMGetDMKSPWrite(dms[i],&kdm);
    597:       /* Ugly hack so that the next KSPSetUp() will use the RHS that we set. A better fix is to change dmActive to take
    598:        * a bitwise OR of computing the matrix, RHS, and initial iterate. */
    599:       kdm->ops->computerhs = NULL;
    600:       kdm->rhsctx          = NULL;
    601:       if (!mglevels[i+1]->interpolate) {
    602:         DMCreateInterpolation(dms[i],dms[i+1],&p,&rscale);
    603:         PCMGSetInterpolation(pc,i+1,p);
    604:         if (rscale) {PCMGSetRScale(pc,i+1,rscale);}
    605:         VecDestroy(&rscale);
    606:         MatDestroy(&p);
    607:       }
    608:     }

    610:     for (i=n-2; i>-1; i--) {
    611:       DMDestroy(&dms[i]);
    612:     }
    613:     PetscFree(dms);
    614:   }

    616:   if (pc->dm && !pc->setupcalled) {
    617:     /* finest smoother also gets DM but it is not active, independent of whether galerkin==2 */
    618:     KSPSetDM(mglevels[n-1]->smoothd,pc->dm);
    619:     KSPSetDMActive(mglevels[n-1]->smoothd,PETSC_FALSE);
    620:   }

    622:   if (mg->galerkin == 1) {
    623:     Mat B;
    624:     /* currently only handle case where mat and pmat are the same on coarser levels */
    625:     KSPGetOperators(mglevels[n-1]->smoothd,&dA,&dB,&uflag);
    626:     if (!pc->setupcalled) {
    627:       for (i=n-2; i>-1; i--) {
    628:         MatPtAP(dB,mglevels[i+1]->interpolate,MAT_INITIAL_MATRIX,1.0,&B);
    629:         KSPSetOperators(mglevels[i]->smoothd,B,B,uflag);
    630:         if (i != n-2) {PetscObjectDereference((PetscObject)dB);}
    631:         dB = B;
    632:       }
    633:       if (n > 1) {PetscObjectDereference((PetscObject)dB);}
    634:     } else {
    635:       for (i=n-2; i>-1; i--) {
    636:         KSPGetOperators(mglevels[i]->smoothd,NULL,&B,NULL);
    637:         MatPtAP(dB,mglevels[i+1]->interpolate,MAT_REUSE_MATRIX,1.0,&B);
    638:         KSPSetOperators(mglevels[i]->smoothd,B,B,uflag);
    639:         dB   = B;
    640:       }
    641:     }
    642:   } else if (!mg->galerkin && pc->dm && pc->dm->x) {
    643:     /* need to restrict Jacobian location to coarser meshes for evaluation */
    644:     for (i=n-2; i>-1; i--) {
    645:       Mat R;
    646:       Vec rscale;
    647:       if (!mglevels[i]->smoothd->dm->x) {
    648:         Vec *vecs;
    649:         KSPGetVecs(mglevels[i]->smoothd,1,&vecs,0,NULL);

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

    653:         PetscFree(vecs);
    654:       }
    655:       PCMGGetRestriction(pc,i+1,&R);
    656:       PCMGGetRScale(pc,i+1,&rscale);
    657:       MatRestrict(R,mglevels[i+1]->smoothd->dm->x,mglevels[i]->smoothd->dm->x);
    658:       VecPointwiseMult(mglevels[i]->smoothd->dm->x,mglevels[i]->smoothd->dm->x,rscale);
    659:     }
    660:   }
    661:   if (!mg->galerkin && pc->dm) {
    662:     for (i=n-2; i>=0; i--) {
    663:       DM  dmfine,dmcoarse;
    664:       Mat Restrict,Inject;
    665:       Vec rscale;
    666:       KSPGetDM(mglevels[i+1]->smoothd,&dmfine);
    667:       KSPGetDM(mglevels[i]->smoothd,&dmcoarse);
    668:       PCMGGetRestriction(pc,i+1,&Restrict);
    669:       PCMGGetRScale(pc,i+1,&rscale);
    670:       Inject = NULL;      /* Callback should create it if it needs Injection */
    671:       DMRestrict(dmfine,Restrict,rscale,Inject,dmcoarse);
    672:     }
    673:   }

    675:   if (!pc->setupcalled) {
    676:     for (i=0; i<n; i++) {
    677:       KSPSetFromOptions(mglevels[i]->smoothd);
    678:     }
    679:     for (i=1; i<n; i++) {
    680:       if (mglevels[i]->smoothu && (mglevels[i]->smoothu != mglevels[i]->smoothd)) {
    681:         KSPSetFromOptions(mglevels[i]->smoothu);
    682:       }
    683:     }
    684:     for (i=1; i<n; i++) {
    685:       PCMGGetInterpolation(pc,i,&mglevels[i]->interpolate);
    686:       PCMGGetRestriction(pc,i,&mglevels[i]->restrct);
    687:     }
    688:     for (i=0; i<n-1; i++) {
    689:       if (!mglevels[i]->b) {
    690:         Vec *vec;
    691:         KSPGetVecs(mglevels[i]->smoothd,1,&vec,0,NULL);
    692:         PCMGSetRhs(pc,i,*vec);
    693:         VecDestroy(vec);
    694:         PetscFree(vec);
    695:       }
    696:       if (!mglevels[i]->r && i) {
    697:         VecDuplicate(mglevels[i]->b,&tvec);
    698:         PCMGSetR(pc,i,tvec);
    699:         VecDestroy(&tvec);
    700:       }
    701:       if (!mglevels[i]->x) {
    702:         VecDuplicate(mglevels[i]->b,&tvec);
    703:         PCMGSetX(pc,i,tvec);
    704:         VecDestroy(&tvec);
    705:       }
    706:     }
    707:     if (n != 1 && !mglevels[n-1]->r) {
    708:       /* PCMGSetR() on the finest level if user did not supply it */
    709:       Vec *vec;
    710:       KSPGetVecs(mglevels[n-1]->smoothd,1,&vec,0,NULL);
    711:       PCMGSetR(pc,n-1,*vec);
    712:       VecDestroy(vec);
    713:       PetscFree(vec);
    714:     }
    715:   }

    717:   if (pc->dm) {
    718:     /* need to tell all the coarser levels to rebuild the matrix using the DM for that level */
    719:     for (i=0; i<n-1; i++) {
    720:       if (mglevels[i]->smoothd->setupstage != KSP_SETUP_NEW) mglevels[i]->smoothd->setupstage = KSP_SETUP_NEWMATRIX;
    721:     }
    722:   }

    724:   for (i=1; i<n; i++) {
    725:     if (mglevels[i]->smoothu == mglevels[i]->smoothd) {
    726:       /* if doing only down then initial guess is zero */
    727:       KSPSetInitialGuessNonzero(mglevels[i]->smoothd,PETSC_TRUE);
    728:     }
    729:     if (mglevels[i]->eventsmoothsetup) {PetscLogEventBegin(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    730:     KSPSetUp(mglevels[i]->smoothd);
    731:     if (mglevels[i]->eventsmoothsetup) {PetscLogEventEnd(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    732:     if (!mglevels[i]->residual) {
    733:       Mat mat;
    734:       KSPGetOperators(mglevels[i]->smoothd,NULL,&mat,NULL);
    735:       PCMGSetResidual(pc,i,PCMGResidual_Default,mat);
    736:     }
    737:   }
    738:   for (i=1; i<n; i++) {
    739:     if (mglevels[i]->smoothu && mglevels[i]->smoothu != mglevels[i]->smoothd) {
    740:       Mat          downmat,downpmat;
    741:       MatStructure matflag;

    743:       /* check if operators have been set for up, if not use down operators to set them */
    744:       KSPGetOperatorsSet(mglevels[i]->smoothu,&opsset,NULL);
    745:       if (!opsset) {
    746:         KSPGetOperators(mglevels[i]->smoothd,&downmat,&downpmat,&matflag);
    747:         KSPSetOperators(mglevels[i]->smoothu,downmat,downpmat,matflag);
    748:       }

    750:       KSPSetInitialGuessNonzero(mglevels[i]->smoothu,PETSC_TRUE);
    751:       if (mglevels[i]->eventsmoothsetup) {PetscLogEventBegin(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    752:       KSPSetUp(mglevels[i]->smoothu);
    753:       if (mglevels[i]->eventsmoothsetup) {PetscLogEventEnd(mglevels[i]->eventsmoothsetup,0,0,0,0);}
    754:     }
    755:   }

    757:   /*
    758:       If coarse solver is not direct method then DO NOT USE preonly
    759:   */
    760:   PetscObjectTypeCompare((PetscObject)mglevels[0]->smoothd,KSPPREONLY,&preonly);
    761:   if (preonly) {
    762:     PetscObjectTypeCompare((PetscObject)cpc,PCLU,&lu);
    763:     PetscObjectTypeCompare((PetscObject)cpc,PCREDUNDANT,&redundant);
    764:     PetscObjectTypeCompare((PetscObject)cpc,PCCHOLESKY,&cholesky);
    765:     PetscObjectTypeCompare((PetscObject)cpc,PCSVD,&svd);
    766:     if (!lu && !redundant && !cholesky && !svd) {
    767:       KSPSetType(mglevels[0]->smoothd,KSPGMRES);
    768:     }
    769:   }

    771:   if (!pc->setupcalled) {
    772:     KSPSetFromOptions(mglevels[0]->smoothd);
    773:   }

    775:   if (mglevels[0]->eventsmoothsetup) {PetscLogEventBegin(mglevels[0]->eventsmoothsetup,0,0,0,0);}
    776:   KSPSetUp(mglevels[0]->smoothd);
    777:   if (mglevels[0]->eventsmoothsetup) {PetscLogEventEnd(mglevels[0]->eventsmoothsetup,0,0,0,0);}

    779:   /*
    780:      Dump the interpolation/restriction matrices plus the
    781:    Jacobian/stiffness on each level. This allows MATLAB users to
    782:    easily check if the Galerkin condition A_c = R A_f R^T is satisfied.

    784:    Only support one or the other at the same time.
    785:   */
    786: #if defined(PETSC_USE_SOCKET_VIEWER)
    787:   PetscOptionsGetBool(((PetscObject)pc)->prefix,"-pc_mg_dump_matlab",&dump,NULL);
    788:   if (dump) viewer = PETSC_VIEWER_SOCKET_(PetscObjectComm((PetscObject)pc));
    789:   dump = PETSC_FALSE;
    790: #endif
    791:   PetscOptionsGetBool(((PetscObject)pc)->prefix,"-pc_mg_dump_binary",&dump,NULL);
    792:   if (dump) viewer = PETSC_VIEWER_BINARY_(PetscObjectComm((PetscObject)pc));

    794:   if (viewer) {
    795:     for (i=1; i<n; i++) {
    796:       MatView(mglevels[i]->restrct,viewer);
    797:     }
    798:     for (i=0; i<n; i++) {
    799:       KSPGetPC(mglevels[i]->smoothd,&pc);
    800:       MatView(pc->mat,viewer);
    801:     }
    802:   }
    803:   return(0);
    804: }

    806: /* -------------------------------------------------------------------------------------*/

    810: /*@
    811:    PCMGGetLevels - Gets the number of levels to use with MG.

    813:    Not Collective

    815:    Input Parameter:
    816: .  pc - the preconditioner context

    818:    Output parameter:
    819: .  levels - the number of levels

    821:    Level: advanced

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

    825: .seealso: PCMGSetLevels()
    826: @*/
    827: PetscErrorCode  PCMGGetLevels(PC pc,PetscInt *levels)
    828: {
    829:   PC_MG *mg = (PC_MG*)pc->data;

    834:   *levels = mg->nlevels;
    835:   return(0);
    836: }

    840: /*@
    841:    PCMGSetType - Determines the form of multigrid to use:
    842:    multiplicative, additive, full, or the Kaskade algorithm.

    844:    Logically Collective on PC

    846:    Input Parameters:
    847: +  pc - the preconditioner context
    848: -  form - multigrid form, one of PC_MG_MULTIPLICATIVE, PC_MG_ADDITIVE,
    849:    PC_MG_FULL, PC_MG_KASKADE

    851:    Options Database Key:
    852: .  -pc_mg_type <form> - Sets <form>, one of multiplicative,
    853:    additive, full, kaskade

    855:    Level: advanced

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

    859: .seealso: PCMGSetLevels()
    860: @*/
    861: PetscErrorCode  PCMGSetType(PC pc,PCMGType form)
    862: {
    863:   PC_MG *mg = (PC_MG*)pc->data;

    868:   mg->am = form;
    869:   if (form == PC_MG_MULTIPLICATIVE) pc->ops->applyrichardson = PCApplyRichardson_MG;
    870:   else pc->ops->applyrichardson = 0;
    871:   return(0);
    872: }

    876: /*@
    877:    PCMGSetCycleType - Sets the type cycles to use.  Use PCMGSetCycleTypeOnLevel() for more
    878:    complicated cycling.

    880:    Logically Collective on PC

    882:    Input Parameters:
    883: +  pc - the multigrid context
    884: -  PC_MG_CYCLE_V or PC_MG_CYCLE_W

    886:    Options Database Key:
    887: $  -pc_mg_cycle_type v or w

    889:    Level: advanced

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

    893: .seealso: PCMGSetCycleTypeOnLevel()
    894: @*/
    895: PetscErrorCode  PCMGSetCycleType(PC pc,PCMGCycleType n)
    896: {
    897:   PC_MG        *mg        = (PC_MG*)pc->data;
    898:   PC_MG_Levels **mglevels = mg->levels;
    899:   PetscInt     i,levels;

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

    907:   for (i=0; i<levels; i++) mglevels[i]->cycles = n;
    908:   return(0);
    909: }

    913: /*@
    914:    PCMGMultiplicativeSetCycles - Sets the number of cycles to use for each preconditioner step
    915:          of multigrid when PCMGType of PC_MG_MULTIPLICATIVE is used

    917:    Logically Collective on PC

    919:    Input Parameters:
    920: +  pc - the multigrid context
    921: -  n - number of cycles (default is 1)

    923:    Options Database Key:
    924: $  -pc_mg_multiplicative_cycles n

    926:    Level: advanced

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

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

    932: .seealso: PCMGSetCycleTypeOnLevel(), PCMGSetCycleType()
    933: @*/
    934: PetscErrorCode  PCMGMultiplicativeSetCycles(PC pc,PetscInt n)
    935: {
    936:   PC_MG        *mg        = (PC_MG*)pc->data;
    937:   PC_MG_Levels **mglevels = mg->levels;
    938:   PetscInt     i,levels;

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

    946:   for (i=0; i<levels; i++) mg->cyclesperpcapply = n;
    947:   return(0);
    948: }

    952: /*@
    953:    PCMGSetGalerkin - Causes the coarser grid matrices to be computed from the
    954:       finest grid via the Galerkin process: A_i-1 = r_i * A_i * r_i^t

    956:    Logically Collective on PC

    958:    Input Parameters:
    959: +  pc - the multigrid context
    960: -  use - PETSC_TRUE to use the Galerkin process to compute coarse-level operators

    962:    Options Database Key:
    963: $  -pc_mg_galerkin

    965:    Level: intermediate

    967: .keywords: MG, set, Galerkin

    969: .seealso: PCMGGetGalerkin()

    971: @*/
    972: PetscErrorCode PCMGSetGalerkin(PC pc,PetscBool use)
    973: {
    974:   PC_MG *mg = (PC_MG*)pc->data;

    978:   mg->galerkin = use ? 1 : 0;
    979:   return(0);
    980: }

    984: /*@
    985:    PCMGGetGalerkin - Checks if Galerkin multigrid is being used, i.e.
    986:       A_i-1 = r_i * A_i * r_i^t

    988:    Not Collective

    990:    Input Parameter:
    991: .  pc - the multigrid context

    993:    Output Parameter:
    994: .  gelerkin - PETSC_TRUE or PETSC_FALSE

    996:    Options Database Key:
    997: $  -pc_mg_galerkin

    999:    Level: intermediate

    1001: .keywords: MG, set, Galerkin

    1003: .seealso: PCMGSetGalerkin()

    1005: @*/
    1006: PetscErrorCode  PCMGGetGalerkin(PC pc,PetscBool  *galerkin)
    1007: {
    1008:   PC_MG *mg = (PC_MG*)pc->data;

    1012:   *galerkin = (PetscBool)mg->galerkin;
    1013:   return(0);
    1014: }

    1018: /*@
    1019:    PCMGSetNumberSmoothDown - Sets the number of pre-smoothing steps to
    1020:    use on all levels. Use PCMGGetSmootherDown() to set different
    1021:    pre-smoothing steps on different levels.

    1023:    Logically Collective on PC

    1025:    Input Parameters:
    1026: +  mg - the multigrid context
    1027: -  n - the number of smoothing steps

    1029:    Options Database Key:
    1030: .  -pc_mg_smoothdown <n> - Sets number of pre-smoothing steps

    1032:    Level: advanced

    1034: .keywords: MG, smooth, down, pre-smoothing, steps, multigrid

    1036: .seealso: PCMGSetNumberSmoothUp()
    1037: @*/
    1038: PetscErrorCode  PCMGSetNumberSmoothDown(PC pc,PetscInt n)
    1039: {
    1040:   PC_MG          *mg        = (PC_MG*)pc->data;
    1041:   PC_MG_Levels   **mglevels = mg->levels;
    1043:   PetscInt       i,levels;

    1047:   if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONGSTATE,"Must set MG levels before calling");
    1049:   levels = mglevels[0]->levels;

    1051:   for (i=1; i<levels; i++) {
    1052:     /* make sure smoother up and down are different */
    1053:     PCMGGetSmootherUp(pc,i,NULL);
    1054:     KSPSetTolerances(mglevels[i]->smoothd,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT,n);

    1056:     mg->default_smoothd = n;
    1057:   }
    1058:   return(0);
    1059: }

    1063: /*@
    1064:    PCMGSetNumberSmoothUp - Sets the number of post-smoothing steps to use
    1065:    on all levels. Use PCMGGetSmootherUp() to set different numbers of
    1066:    post-smoothing steps on different levels.

    1068:    Logically Collective on PC

    1070:    Input Parameters:
    1071: +  mg - the multigrid context
    1072: -  n - the number of smoothing steps

    1074:    Options Database Key:
    1075: .  -pc_mg_smoothup <n> - Sets number of post-smoothing steps

    1077:    Level: advanced

    1079:    Note: this does not set a value on the coarsest grid, since we assume that
    1080:     there is no separate smooth up on the coarsest grid.

    1082: .keywords: MG, smooth, up, post-smoothing, steps, multigrid

    1084: .seealso: PCMGSetNumberSmoothDown()
    1085: @*/
    1086: PetscErrorCode  PCMGSetNumberSmoothUp(PC pc,PetscInt n)
    1087: {
    1088:   PC_MG          *mg        = (PC_MG*)pc->data;
    1089:   PC_MG_Levels   **mglevels = mg->levels;
    1091:   PetscInt       i,levels;

    1095:   if (!mglevels) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_WRONGSTATE,"Must set MG levels before calling");
    1097:   levels = mglevels[0]->levels;

    1099:   for (i=1; i<levels; i++) {
    1100:     /* make sure smoother up and down are different */
    1101:     PCMGGetSmootherUp(pc,i,NULL);
    1102:     KSPSetTolerances(mglevels[i]->smoothu,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT,n);

    1104:     mg->default_smoothu = n;
    1105:   }
    1106:   return(0);
    1107: }

    1109: /* ----------------------------------------------------------------------------------------*/

    1111: /*MC
    1112:    PCMG - Use multigrid preconditioning. This preconditioner requires you provide additional
    1113:     information about the coarser grid matrices and restriction/interpolation operators.

    1115:    Options Database Keys:
    1116: +  -pc_mg_levels <nlevels> - number of levels including finest
    1117: .  -pc_mg_cycles v or w
    1118: .  -pc_mg_smoothup <n> - number of smoothing steps after interpolation
    1119: .  -pc_mg_smoothdown <n> - number of smoothing steps before applying restriction operator
    1120: .  -pc_mg_type <additive,multiplicative,full,kaskade> - multiplicative is the default
    1121: .  -pc_mg_log - log information about time spent on each level of the solver
    1122: .  -pc_mg_monitor - print information on the multigrid convergence
    1123: .  -pc_mg_galerkin - use Galerkin process to compute coarser operators, i.e. Acoarse = R A R'
    1124: .  -pc_mg_multiplicative_cycles - number of cycles to use as the preconditioner (defaults to 1)
    1125: .  -pc_mg_dump_matlab - dumps the matrices for each level and the restriction/interpolation matrices
    1126:                         to the Socket viewer for reading from MATLAB.
    1127: -  -pc_mg_dump_binary - dumps the matrices for each level and the restriction/interpolation matrices
    1128:                         to the binary output file called binaryoutput

    1130:    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

    1132:        When run with a single level the smoother options are used on that level NOT the coarse grid solver options

    1134:    Level: intermediate

    1136:    Concepts: multigrid/multilevel

    1138: .seealso:  PCCreate(), PCSetType(), PCType (for list of available types), PC, PCMGType, PCEXOTIC, PCGAMG, PCML, PCHYPRE
    1139:            PCMGSetLevels(), PCMGGetLevels(), PCMGSetType(), PCMGSetCycleType(), PCMGSetNumberSmoothDown(),
    1140:            PCMGSetNumberSmoothUp(), PCMGGetCoarseSolve(), PCMGSetResidual(), PCMGSetInterpolation(),
    1141:            PCMGSetRestriction(), PCMGGetSmoother(), PCMGGetSmootherUp(), PCMGGetSmootherDown(),
    1142:            PCMGSetCycleTypeOnLevel(), PCMGSetRhs(), PCMGSetX(), PCMGSetR()
    1143: M*/

    1147: PETSC_EXTERN PetscErrorCode PCCreate_MG(PC pc)
    1148: {
    1149:   PC_MG          *mg;

    1153:   PetscNewLog(pc,PC_MG,&mg);
    1154:   pc->data    = (void*)mg;
    1155:   mg->nlevels = -1;

    1157:   pc->useAmat = PETSC_TRUE;

    1159:   pc->ops->apply          = PCApply_MG;
    1160:   pc->ops->setup          = PCSetUp_MG;
    1161:   pc->ops->reset          = PCReset_MG;
    1162:   pc->ops->destroy        = PCDestroy_MG;
    1163:   pc->ops->setfromoptions = PCSetFromOptions_MG;
    1164:   pc->ops->view           = PCView_MG;
    1165:   return(0);
    1166: }