Actual source code: fas.c
petsc-3.15.0 2021-03-30
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      1: /* Defines the basic SNES object */
      2: #include <../src/snes/impls/fas/fasimpls.h>

      4: const char *const SNESFASTypes[] = {"MULTIPLICATIVE","ADDITIVE","FULL","KASKADE","SNESFASType","SNES_FAS",NULL};

      6: static PetscErrorCode SNESReset_FAS(SNES snes)
      7: {
      8:   SNES_FAS       *fas = (SNES_FAS*)snes->data;

     12:   SNESDestroy(&fas->smoothu);
     13:   SNESDestroy(&fas->smoothd);
     14:   MatDestroy(&fas->inject);
     15:   MatDestroy(&fas->interpolate);
     16:   MatDestroy(&fas->restrct);
     17:   VecDestroy(&fas->rscale);
     18:   VecDestroy(&fas->Xg);
     19:   VecDestroy(&fas->Fg);
     20:   if (fas->next) {SNESReset(fas->next);}
     21:   return(0);
     22: }

     24: static PetscErrorCode SNESDestroy_FAS(SNES snes)
     25: {
     26:   SNES_FAS       *fas = (SNES_FAS*)snes->data;

     30:   /* recursively resets and then destroys */
     31:   SNESReset_FAS(snes);
     32:   SNESDestroy(&fas->next);
     33:   PetscFree(fas);
     34:   return(0);
     35: }

     37: static PetscErrorCode SNESFASSetUpLineSearch_Private(SNES snes, SNES smooth)
     38: {
     39:   SNESLineSearch linesearch;
     40:   SNESLineSearch slinesearch;
     41:   void           *lsprectx,*lspostctx;
     42:   PetscErrorCode (*precheck)(SNESLineSearch,Vec,Vec,PetscBool*,void*);
     43:   PetscErrorCode (*postcheck)(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);

     47:   if (!snes->linesearch) return(0);
     48:   SNESGetLineSearch(snes,&linesearch);
     49:   SNESGetLineSearch(smooth,&slinesearch);
     50:   SNESLineSearchGetPreCheck(linesearch,&precheck,&lsprectx);
     51:   SNESLineSearchGetPostCheck(linesearch,&postcheck,&lspostctx);
     52:   SNESLineSearchSetPreCheck(slinesearch,precheck,lsprectx);
     53:   SNESLineSearchSetPostCheck(slinesearch,postcheck,lspostctx);
     54:   PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)slinesearch);
     55:   return(0);
     56: }

     58: static PetscErrorCode SNESFASCycleSetUpSmoother_Private(SNES snes, SNES smooth)
     59: {
     60:   SNES_FAS       *fas = (SNES_FAS*) snes->data;

     64:   PetscObjectCopyFortranFunctionPointers((PetscObject)snes, (PetscObject)smooth);
     65:   SNESSetFromOptions(smooth);
     66:   SNESFASSetUpLineSearch_Private(snes, smooth);

     68:   PetscObjectReference((PetscObject)snes->vec_sol);
     69:   PetscObjectReference((PetscObject)snes->vec_sol_update);
     70:   PetscObjectReference((PetscObject)snes->vec_func);
     71:   smooth->vec_sol        = snes->vec_sol;
     72:   smooth->vec_sol_update = snes->vec_sol_update;
     73:   smooth->vec_func       = snes->vec_func;

     75:   if (fas->eventsmoothsetup) {PetscLogEventBegin(fas->eventsmoothsetup,smooth,0,0,0);}
     76:   SNESSetUp(smooth);
     77:   if (fas->eventsmoothsetup) {PetscLogEventEnd(fas->eventsmoothsetup,smooth,0,0,0);}
     78:   return(0);
     79: }

     81: static PetscErrorCode SNESSetUp_FAS(SNES snes)
     82: {
     83:   SNES_FAS       *fas = (SNES_FAS*) snes->data;
     85:   PetscInt       dm_levels;
     86:   SNES           next;
     87:   PetscBool      isFine, hasCreateRestriction, hasCreateInjection;

     90:   SNESFASCycleIsFine(snes, &isFine);
     91:   if (fas->usedmfornumberoflevels && isFine) {
     92:     DMGetRefineLevel(snes->dm,&dm_levels);
     93:     dm_levels++;
     94:     if (dm_levels > fas->levels) {
     95:       /* reset the number of levels */
     96:       SNESFASSetLevels(snes,dm_levels,NULL);
     97:       SNESSetFromOptions(snes);
     98:     }
     99:   }
    100:   SNESFASCycleGetCorrection(snes, &next);
    101:   if (!isFine) snes->gridsequence = 0; /* no grid sequencing inside the multigrid hierarchy! */

    103:   SNESSetWorkVecs(snes, 2); /* work vectors used for intergrid transfers */

    105:   /* set up the smoothers if they haven't already been set up */
    106:   if (!fas->smoothd) {
    107:     SNESFASCycleCreateSmoother_Private(snes, &fas->smoothd);
    108:   }

    110:   if (snes->dm) {
    111:     /* set the smoother DMs properly */
    112:     if (fas->smoothu) {SNESSetDM(fas->smoothu, snes->dm);}
    113:     SNESSetDM(fas->smoothd, snes->dm);
    114:     /* construct EVERYTHING from the DM -- including the progressive set of smoothers */
    115:     if (next) {
    116:       /* for now -- assume the DM and the evaluation functions have been set externally */
    117:       if (!next->dm) {
    118:         DMCoarsen(snes->dm, PetscObjectComm((PetscObject)next), &next->dm);
    119:         SNESSetDM(next, next->dm);
    120:       }
    121:       /* set the interpolation and restriction from the DM */
    122:       if (!fas->interpolate) {
    123:         DMCreateInterpolation(next->dm, snes->dm, &fas->interpolate, &fas->rscale);
    124:         if (!fas->restrct) {
    125:           DMHasCreateRestriction(next->dm, &hasCreateRestriction);
    126:           /* DM can create restrictions, use that */
    127:           if (hasCreateRestriction) {
    128:             DMCreateRestriction(next->dm, snes->dm, &fas->restrct);
    129:           } else {
    130:             PetscObjectReference((PetscObject)fas->interpolate);
    131:             fas->restrct = fas->interpolate;
    132:           }
    133:         }
    134:       }
    135:       /* set the injection from the DM */
    136:       if (!fas->inject) {
    137:         DMHasCreateInjection(next->dm, &hasCreateInjection);
    138:         if (hasCreateInjection) {
    139:           DMCreateInjection(next->dm, snes->dm, &fas->inject);
    140:         }
    141:       }
    142:     }
    143:   }

    145:   /*pass the smoother, function, and jacobian up to the next level if it's not user set already */
    146:   if (fas->galerkin) {
    147:     if (next) {
    148:       SNESSetFunction(next, NULL, SNESFASGalerkinFunctionDefault, next);
    149:     }
    150:     if (fas->smoothd && fas->level != fas->levels - 1) {
    151:       SNESSetFunction(fas->smoothd, NULL, SNESFASGalerkinFunctionDefault, snes);
    152:     }
    153:     if (fas->smoothu && fas->level != fas->levels - 1) {
    154:       SNESSetFunction(fas->smoothu, NULL, SNESFASGalerkinFunctionDefault, snes);
    155:     }
    156:   }

    158:   /* sets the down (pre) smoother's default norm and sets it from options */
    159:   if (fas->smoothd) {
    160:     if (fas->level == 0 && fas->levels != 1) {
    161:       SNESSetNormSchedule(fas->smoothd, SNES_NORM_NONE);
    162:     } else {
    163:       SNESSetNormSchedule(fas->smoothd, SNES_NORM_FINAL_ONLY);
    164:     }
    165:     SNESFASCycleSetUpSmoother_Private(snes, fas->smoothd);
    166:   }

    168:   /* sets the up (post) smoother's default norm and sets it from options */
    169:   if (fas->smoothu) {
    170:     if (fas->level != fas->levels - 1) {
    171:       SNESSetNormSchedule(fas->smoothu, SNES_NORM_NONE);
    172:     } else {
    173:       SNESSetNormSchedule(fas->smoothu, SNES_NORM_FINAL_ONLY);
    174:     }
    175:     SNESFASCycleSetUpSmoother_Private(snes, fas->smoothu);
    176:   }

    178:   if (next) {
    179:     /* gotta set up the solution vector for this to work */
    180:     if (!next->vec_sol) {SNESFASCreateCoarseVec(snes,&next->vec_sol);}
    181:     if (!next->vec_rhs) {SNESFASCreateCoarseVec(snes,&next->vec_rhs);}
    182:     PetscObjectCopyFortranFunctionPointers((PetscObject)snes, (PetscObject)next);
    183:     SNESFASSetUpLineSearch_Private(snes, next);
    184:     SNESSetUp(next);
    185:   }

    187:   /* setup FAS work vectors */
    188:   if (fas->galerkin) {
    189:     VecDuplicate(snes->vec_sol, &fas->Xg);
    190:     VecDuplicate(snes->vec_sol, &fas->Fg);
    191:   }
    192:   return(0);
    193: }

    195: static PetscErrorCode SNESSetFromOptions_FAS(PetscOptionItems *PetscOptionsObject,SNES snes)
    196: {
    197:   SNES_FAS       *fas   = (SNES_FAS*) snes->data;
    198:   PetscInt       levels = 1;
    199:   PetscBool      flg    = PETSC_FALSE, upflg = PETSC_FALSE, downflg = PETSC_FALSE, monflg = PETSC_FALSE, galerkinflg = PETSC_FALSE,continuationflg = PETSC_FALSE;
    201:   SNESFASType    fastype;
    202:   const char     *optionsprefix;
    203:   SNESLineSearch linesearch;
    204:   PetscInt       m, n_up, n_down;
    205:   SNES           next;
    206:   PetscBool      isFine;

    209:   SNESFASCycleIsFine(snes, &isFine);
    210:   PetscOptionsHead(PetscOptionsObject,"SNESFAS Options-----------------------------------");

    212:   /* number of levels -- only process most options on the finest level */
    213:   if (isFine) {
    214:     PetscOptionsInt("-snes_fas_levels", "Number of Levels", "SNESFASSetLevels", levels, &levels, &flg);
    215:     if (!flg && snes->dm) {
    216:       DMGetRefineLevel(snes->dm,&levels);
    217:       levels++;
    218:       fas->usedmfornumberoflevels = PETSC_TRUE;
    219:     }
    220:     SNESFASSetLevels(snes, levels, NULL);
    221:     fastype = fas->fastype;
    222:     PetscOptionsEnum("-snes_fas_type","FAS correction type","SNESFASSetType",SNESFASTypes,(PetscEnum)fastype,(PetscEnum*)&fastype,&flg);
    223:     if (flg) {
    224:       SNESFASSetType(snes, fastype);
    225:     }

    227:     SNESGetOptionsPrefix(snes, &optionsprefix);
    228:     PetscOptionsInt("-snes_fas_cycles","Number of cycles","SNESFASSetCycles",fas->n_cycles,&m,&flg);
    229:     if (flg) {
    230:       SNESFASSetCycles(snes, m);
    231:     }
    232:     PetscOptionsBool("-snes_fas_continuation","Corrected grid-sequence continuation","SNESFASSetContinuation",fas->continuation,&continuationflg,&flg);
    233:     if (flg) {
    234:       SNESFASSetContinuation(snes,continuationflg);
    235:     }

    237:     PetscOptionsBool("-snes_fas_galerkin", "Form coarse problems with Galerkin","SNESFASSetGalerkin",fas->galerkin,&galerkinflg,&flg);
    238:     if (flg) {
    239:       SNESFASSetGalerkin(snes, galerkinflg);
    240:     }

    242:     if (fas->fastype == SNES_FAS_FULL) {
    243:       PetscOptionsBool("-snes_fas_full_downsweep","Smooth on the initial down sweep for full FAS cycles","SNESFASFullSetDownSweep",fas->full_downsweep,&fas->full_downsweep,&flg);
    244:       if (flg) {SNESFASFullSetDownSweep(snes,fas->full_downsweep);}
    245:       PetscOptionsBool("-snes_fas_full_total","Use total restriction and interpolaton on the indial down and up sweeps for the full FAS cycle","SNESFASFullSetUseTotal",fas->full_total,&fas->full_total,&flg);
    246:       if (flg) {SNESFASFullSetTotal(snes,fas->full_total);}
    247:     }

    249:     PetscOptionsInt("-snes_fas_smoothup","Number of post-smoothing steps","SNESFASSetNumberSmoothUp",fas->max_up_it,&n_up,&upflg);

    251:     PetscOptionsInt("-snes_fas_smoothdown","Number of pre-smoothing steps","SNESFASSetNumberSmoothDown",fas->max_down_it,&n_down,&downflg);

    253:     {
    254:       PetscViewer viewer;
    255:       PetscViewerFormat format;
    256:       PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject) snes)->options,((PetscObject)snes)->prefix,"-snes_fas_monitor",&viewer,&format,&monflg);
    257:       if (monflg) {
    258:         PetscViewerAndFormat *vf;
    259:         PetscViewerAndFormatCreate(viewer,format,&vf);
    260:         PetscObjectDereference((PetscObject)viewer);
    261:         SNESFASSetMonitor(snes,vf,PETSC_TRUE);
    262:       }
    263:     }
    264:     flg    = PETSC_FALSE;
    265:     monflg = PETSC_TRUE;
    266:     PetscOptionsBool("-snes_fas_log","Log times for each FAS level","SNESFASSetLog",monflg,&monflg,&flg);
    267:     if (flg) {SNESFASSetLog(snes,monflg);}
    268:   }

    270:   PetscOptionsTail();

    272:   /* setup from the determined types if there is no pointwise procedure or smoother defined */
    273:   if (upflg) {
    274:     SNESFASSetNumberSmoothUp(snes,n_up);
    275:   }
    276:   if (downflg) {
    277:     SNESFASSetNumberSmoothDown(snes,n_down);
    278:   }

    280:   /* set up the default line search for coarse grid corrections */
    281:   if (fas->fastype == SNES_FAS_ADDITIVE) {
    282:     if (!snes->linesearch) {
    283:       SNESGetLineSearch(snes, &linesearch);
    284:       SNESLineSearchSetType(linesearch, SNESLINESEARCHL2);
    285:     }
    286:   }

    288:   /* recursive option setting for the smoothers */
    289:   SNESFASCycleGetCorrection(snes, &next);
    290:   if (next) {SNESSetFromOptions(next);}
    291:   return(0);
    292: }

    294: #include <petscdraw.h>
    295: static PetscErrorCode SNESView_FAS(SNES snes, PetscViewer viewer)
    296: {
    297:   SNES_FAS       *fas = (SNES_FAS*) snes->data;
    298:   PetscBool      isFine,iascii,isdraw;
    299:   PetscInt       i;
    301:   SNES           smoothu, smoothd, levelsnes;

    304:   SNESFASCycleIsFine(snes, &isFine);
    305:   if (isFine) {
    306:     PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
    307:     PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERDRAW,&isdraw);
    308:     if (iascii) {
    309:       PetscViewerASCIIPrintf(viewer, "  type is %s, levels=%D, cycles=%D\n",  SNESFASTypes[fas->fastype], fas->levels, fas->n_cycles);
    310:       if (fas->galerkin) {
    311:         PetscViewerASCIIPrintf(viewer,"  Using Galerkin computed coarse grid function evaluation\n");
    312:       } else {
    313:         PetscViewerASCIIPrintf(viewer,"  Not using Galerkin computed coarse grid function evaluation\n");
    314:       }
    315:       for (i=0; i<fas->levels; i++) {
    316:         SNESFASGetCycleSNES(snes, i, &levelsnes);
    317:         SNESFASCycleGetSmootherUp(levelsnes, &smoothu);
    318:         SNESFASCycleGetSmootherDown(levelsnes, &smoothd);
    319:         if (!i) {
    320:           PetscViewerASCIIPrintf(viewer,"  Coarse grid solver -- level %D -------------------------------\n",i);
    321:         } else {
    322:           PetscViewerASCIIPrintf(viewer,"  Down solver (pre-smoother) on level %D -------------------------------\n",i);
    323:         }
    324:         PetscViewerASCIIPushTab(viewer);
    325:         if (smoothd) {
    326:           SNESView(smoothd,viewer);
    327:         } else {
    328:           PetscViewerASCIIPrintf(viewer,"Not yet available\n");
    329:         }
    330:         PetscViewerASCIIPopTab(viewer);
    331:         if (i && (smoothd == smoothu)) {
    332:           PetscViewerASCIIPrintf(viewer,"  Up solver (post-smoother) same as down solver (pre-smoother)\n");
    333:         } else if (i) {
    334:           PetscViewerASCIIPrintf(viewer,"  Up solver (post-smoother) on level %D -------------------------------\n",i);
    335:           PetscViewerASCIIPushTab(viewer);
    336:           if (smoothu) {
    337:             SNESView(smoothu,viewer);
    338:           } else {
    339:             PetscViewerASCIIPrintf(viewer,"Not yet available\n");
    340:           }
    341:           PetscViewerASCIIPopTab(viewer);
    342:         }
    343:       }
    344:     } else if (isdraw) {
    345:       PetscDraw draw;
    346:       PetscReal x,w,y,bottom,th,wth;
    347:       SNES_FAS  *curfas = fas;
    348:       PetscViewerDrawGetDraw(viewer,0,&draw);
    349:       PetscDrawGetCurrentPoint(draw,&x,&y);
    350:       PetscDrawStringGetSize(draw,&wth,&th);
    351:       bottom = y - th;
    352:       while (curfas) {
    353:         if (!curfas->smoothu) {
    354:           PetscDrawPushCurrentPoint(draw,x,bottom);
    355:           if (curfas->smoothd) SNESView(curfas->smoothd,viewer);
    356:           PetscDrawPopCurrentPoint(draw);
    357:         } else {
    358:           w    = 0.5*PetscMin(1.0-x,x);
    359:           PetscDrawPushCurrentPoint(draw,x-w,bottom);
    360:           if (curfas->smoothd) SNESView(curfas->smoothd,viewer);
    361:           PetscDrawPopCurrentPoint(draw);
    362:           PetscDrawPushCurrentPoint(draw,x+w,bottom);
    363:           if (curfas->smoothu) SNESView(curfas->smoothu,viewer);
    364:           PetscDrawPopCurrentPoint(draw);
    365:         }
    366:         /* this is totally bogus but we have no way of knowing how low the previous one was draw to */
    367:         bottom -= 5*th;
    368:         if (curfas->next) curfas = (SNES_FAS*)curfas->next->data;
    369:         else curfas = NULL;
    370:       }
    371:     }
    372:   }
    373:   return(0);
    374: }

    376: /*
    377: Defines the action of the downsmoother
    378:  */
    379: static PetscErrorCode SNESFASDownSmooth_Private(SNES snes, Vec B, Vec X, Vec F, PetscReal *fnorm)
    380: {
    381:   PetscErrorCode      ierr;
    382:   SNESConvergedReason reason;
    383:   Vec                 FPC;
    384:   SNES                smoothd;
    385:   PetscBool           flg;
    386:   SNES_FAS            *fas = (SNES_FAS*) snes->data;

    389:   SNESFASCycleGetSmootherDown(snes, &smoothd);
    390:   SNESSetInitialFunction(smoothd, F);
    391:   if (fas->eventsmoothsolve) {PetscLogEventBegin(fas->eventsmoothsolve,smoothd,B,X,0);}
    392:   SNESSolve(smoothd, B, X);
    393:   if (fas->eventsmoothsolve) {PetscLogEventEnd(fas->eventsmoothsolve,smoothd,B,X,0);}
    394:   /* check convergence reason for the smoother */
    395:   SNESGetConvergedReason(smoothd,&reason);
    396:   if (reason < 0 && !(reason == SNES_DIVERGED_MAX_IT || reason == SNES_DIVERGED_LOCAL_MIN || reason == SNES_DIVERGED_LINE_SEARCH)) {
    397:     snes->reason = SNES_DIVERGED_INNER;
    398:     return(0);
    399:   }

    401:   SNESGetFunction(smoothd, &FPC, NULL, NULL);
    402:   SNESGetAlwaysComputesFinalResidual(smoothd, &flg);
    403:   if (!flg) {
    404:     SNESComputeFunction(smoothd, X, FPC);
    405:   }
    406:   VecCopy(FPC, F);
    407:   if (fnorm) {VecNorm(F,NORM_2,fnorm);}
    408:   return(0);
    409: }

    412: /*
    413: Defines the action of the upsmoother
    414:  */
    415: static PetscErrorCode SNESFASUpSmooth_Private(SNES snes, Vec B, Vec X, Vec F, PetscReal *fnorm)
    416: {
    417:   PetscErrorCode      ierr;
    418:   SNESConvergedReason reason;
    419:   Vec                 FPC;
    420:   SNES                smoothu;
    421:   PetscBool           flg;
    422:   SNES_FAS            *fas = (SNES_FAS*) snes->data;

    425:   SNESFASCycleGetSmootherUp(snes, &smoothu);
    426:   if (fas->eventsmoothsolve) {PetscLogEventBegin(fas->eventsmoothsolve,smoothu,0,0,0);}
    427:   SNESSolve(smoothu, B, X);
    428:   if (fas->eventsmoothsolve) {PetscLogEventEnd(fas->eventsmoothsolve,smoothu,0,0,0);}
    429:   /* check convergence reason for the smoother */
    430:   SNESGetConvergedReason(smoothu,&reason);
    431:   if (reason < 0 && !(reason == SNES_DIVERGED_MAX_IT || reason == SNES_DIVERGED_LOCAL_MIN || reason == SNES_DIVERGED_LINE_SEARCH)) {
    432:     snes->reason = SNES_DIVERGED_INNER;
    433:     return(0);
    434:   }
    435:   SNESGetFunction(smoothu, &FPC, NULL, NULL);
    436:   SNESGetAlwaysComputesFinalResidual(smoothu, &flg);
    437:   if (!flg) {
    438:     SNESComputeFunction(smoothu, X, FPC);
    439:   }
    440:   VecCopy(FPC, F);
    441:   if (fnorm) {VecNorm(F,NORM_2,fnorm);}
    442:   return(0);
    443: }

    445: /*@
    446:    SNESFASCreateCoarseVec - create Vec corresponding to a state vector on one level coarser than current level

    448:    Collective

    450:    Input Arguments:
    451: .  snes - SNESFAS

    453:    Output Arguments:
    454: .  Xcoarse - vector on level one coarser than snes

    456:    Level: developer

    458: .seealso: SNESFASSetRestriction(), SNESFASRestrict()
    459: @*/
    460: PetscErrorCode SNESFASCreateCoarseVec(SNES snes,Vec *Xcoarse)
    461: {
    463:   SNES_FAS       *fas;

    468:   fas = (SNES_FAS*)snes->data;
    469:   if (fas->rscale) {
    470:     VecDuplicate(fas->rscale,Xcoarse);
    471:   } else if (fas->inject) {
    472:     MatCreateVecs(fas->inject,Xcoarse,NULL);
    473:   } else SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE,"Must set restriction or injection");
    474:   return(0);
    475: }

    477: /*@
    478:    SNESFASRestrict - restrict a Vec to the next coarser level

    480:    Collective

    482:    Input Arguments:
    483: +  fine - SNES from which to restrict
    484: -  Xfine - vector to restrict

    486:    Output Arguments:
    487: .  Xcoarse - result of restriction

    489:    Level: developer

    491: .seealso: SNESFASSetRestriction(), SNESFASSetInjection()
    492: @*/
    493: PetscErrorCode SNESFASRestrict(SNES fine,Vec Xfine,Vec Xcoarse)
    494: {
    496:   SNES_FAS       *fas;

    502:   fas = (SNES_FAS*)fine->data;
    503:   if (fas->inject) {
    504:     MatRestrict(fas->inject,Xfine,Xcoarse);
    505:   } else {
    506:     MatRestrict(fas->restrct,Xfine,Xcoarse);
    507:     VecPointwiseMult(Xcoarse,fas->rscale,Xcoarse);
    508:   }
    509:   return(0);
    510: }

    512: /*

    514: Performs a variant of FAS using the interpolated total coarse solution

    516: fine problem:   F(x) = b
    517: coarse problem: F^c(x^c) = Rb, Initial guess Rx
    518: interpolated solution: x^f = I x^c (total solution interpolation

    520:  */
    521: static PetscErrorCode SNESFASInterpolatedCoarseSolution(SNES snes, Vec X, Vec X_new)
    522: {
    523:   PetscErrorCode      ierr;
    524:   Vec                 X_c, B_c;
    525:   SNESConvergedReason reason;
    526:   SNES                next;
    527:   Mat                 restrct, interpolate;
    528:   SNES_FAS            *fasc;

    531:   SNESFASCycleGetCorrection(snes, &next);
    532:   if (next) {
    533:     fasc = (SNES_FAS*)next->data;

    535:     SNESFASCycleGetRestriction(snes, &restrct);
    536:     SNESFASCycleGetInterpolation(snes, &interpolate);

    538:     X_c  = next->vec_sol;

    540:     if (fasc->eventinterprestrict) {PetscLogEventBegin(fasc->eventinterprestrict,snes,0,0,0);}
    541:     /* restrict the total solution: Rb */
    542:     SNESFASRestrict(snes, X, X_c);
    543:     B_c = next->vec_rhs;
    544:     if (snes->vec_rhs) {
    545:       /* restrict the total rhs defect: Rb */
    546:       MatRestrict(restrct, snes->vec_rhs, B_c);
    547:     } else {
    548:       VecSet(B_c, 0.);
    549:     }
    550:     if (fasc->eventinterprestrict) {PetscLogEventEnd(fasc->eventinterprestrict,snes,0,0,0);}

    552:     SNESSolve(next, B_c, X_c);
    553:     SNESGetConvergedReason(next,&reason);
    554:     if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
    555:       snes->reason = SNES_DIVERGED_INNER;
    556:       return(0);
    557:     }
    558:     /* x^f <- Ix^c*/
    559:     DM dmc,dmf;

    561:     SNESGetDM(next, &dmc);
    562:     SNESGetDM(snes, &dmf);
    563:     if (fasc->eventinterprestrict) {PetscLogEventBegin(fasc->eventinterprestrict,snes,0,0,0);}
    564:     DMInterpolateSolution(dmc, dmf, interpolate, X_c, X_new);
    565:     if (fasc->eventinterprestrict) {PetscLogEventEnd(fasc->eventinterprestrict,snes,0,0,0);}
    566:     PetscObjectSetName((PetscObject) X_c, "Coarse solution");
    567:     VecViewFromOptions(X_c, NULL, "-fas_coarse_solution_view");
    568:     PetscObjectSetName((PetscObject) X_new, "Updated Fine solution");
    569:     VecViewFromOptions(X_new, NULL, "-fas_levels_1_solution_view");
    570:   }
    571:   return(0);
    572: }

    574: /*

    576: Performs the FAS coarse correction as:

    578: fine problem:   F(x) = b
    579: coarse problem: F^c(x^c) = b^c

    581: b^c = F^c(Rx) - R(F(x) - b)

    583:  */
    584: PetscErrorCode SNESFASCoarseCorrection(SNES snes, Vec X, Vec F, Vec X_new)
    585: {
    586:   PetscErrorCode      ierr;
    587:   Vec                 X_c, Xo_c, F_c, B_c;
    588:   SNESConvergedReason reason;
    589:   SNES                next;
    590:   Mat                 restrct, interpolate;
    591:   SNES_FAS            *fasc;

    594:   SNESFASCycleGetCorrection(snes, &next);
    595:   if (next) {
    596:     fasc = (SNES_FAS*)next->data;

    598:     SNESFASCycleGetRestriction(snes, &restrct);
    599:     SNESFASCycleGetInterpolation(snes, &interpolate);

    601:     X_c  = next->vec_sol;
    602:     Xo_c = next->work[0];
    603:     F_c  = next->vec_func;
    604:     B_c  = next->vec_rhs;

    606:     if (fasc->eventinterprestrict) {PetscLogEventBegin(fasc->eventinterprestrict,snes,0,0,0);}
    607:     SNESFASRestrict(snes, X, Xo_c);
    608:     /* restrict the defect: R(F(x) - b) */
    609:     MatRestrict(restrct, F, B_c);
    610:     if (fasc->eventinterprestrict) {PetscLogEventEnd(fasc->eventinterprestrict,snes,0,0,0);}

    612:     if (fasc->eventresidual) {PetscLogEventBegin(fasc->eventresidual,next,0,0,0);}
    613:     /* F_c = F^c(Rx) - R(F(x) - b) since the second term was sitting in next->vec_rhs */
    614:     SNESComputeFunction(next, Xo_c, F_c);
    615:     if (fasc->eventresidual) {PetscLogEventEnd(fasc->eventresidual,next,0,0,0);}

    617:     /* solve the coarse problem corresponding to F^c(x^c) = b^c = F^c(Rx) - R(F(x) - b) */
    618:     VecCopy(B_c, X_c);
    619:     VecCopy(F_c, B_c);
    620:     VecCopy(X_c, F_c);
    621:     /* set initial guess of the coarse problem to the projected fine solution */
    622:     VecCopy(Xo_c, X_c);

    624:     /* recurse to the next level */
    625:     SNESSetInitialFunction(next, F_c);
    626:     SNESSolve(next, B_c, X_c);
    627:     SNESGetConvergedReason(next,&reason);
    628:     if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
    629:       snes->reason = SNES_DIVERGED_INNER;
    630:       return(0);
    631:     }
    632:     /* correct as x <- x + I(x^c - Rx)*/
    633:     VecAXPY(X_c, -1.0, Xo_c);

    635:     if (fasc->eventinterprestrict) {PetscLogEventBegin(fasc->eventinterprestrict,snes,0,0,0);}
    636:     MatInterpolateAdd(interpolate, X_c, X, X_new);
    637:     if (fasc->eventinterprestrict) {PetscLogEventEnd(fasc->eventinterprestrict,snes,0,0,0);}
    638:     PetscObjectSetName((PetscObject) X_c, "Coarse correction");
    639:     VecViewFromOptions(X_c, NULL, "-fas_coarse_solution_view");
    640:     PetscObjectSetName((PetscObject) X_new, "Updated Fine solution");
    641:     VecViewFromOptions(X_new, NULL, "-fas_levels_1_solution_view");
    642:   }
    643:   return(0);
    644: }

    646: /*

    648: The additive cycle looks like:

    650: xhat = x
    651: xhat = dS(x, b)
    652: x = coarsecorrection(xhat, b_d)
    653: x = x + nu*(xhat - x);
    654: (optional) x = uS(x, b)

    656: With the coarse RHS (defect correction) as below.

    658:  */
    659: static PetscErrorCode SNESFASCycle_Additive(SNES snes, Vec X)
    660: {
    661:   Vec                  F, B, Xhat;
    662:   Vec                  X_c, Xo_c, F_c, B_c;
    663:   PetscErrorCode       ierr;
    664:   SNESConvergedReason  reason;
    665:   PetscReal            xnorm, fnorm, ynorm;
    666:   SNESLineSearchReason lsresult;
    667:   SNES                 next;
    668:   Mat                  restrct, interpolate;
    669:   SNES_FAS             *fas = (SNES_FAS*)snes->data,*fasc;

    672:   SNESFASCycleGetCorrection(snes, &next);
    673:   F    = snes->vec_func;
    674:   B    = snes->vec_rhs;
    675:   Xhat = snes->work[1];
    676:   VecCopy(X, Xhat);
    677:   /* recurse first */
    678:   if (next) {
    679:     fasc = (SNES_FAS*)next->data;
    680:     SNESFASCycleGetRestriction(snes, &restrct);
    681:     SNESFASCycleGetInterpolation(snes, &interpolate);
    682:     if (fas->eventresidual) {PetscLogEventBegin(fas->eventresidual,snes,0,0,0);}
    683:     SNESComputeFunction(snes, Xhat, F);
    684:     if (fas->eventresidual) {PetscLogEventEnd(fas->eventresidual,snes,0,0,0);}
    685:     VecNorm(F, NORM_2, &fnorm);
    686:     X_c  = next->vec_sol;
    687:     Xo_c = next->work[0];
    688:     F_c  = next->vec_func;
    689:     B_c  = next->vec_rhs;

    691:     SNESFASRestrict(snes,Xhat,Xo_c);
    692:     /* restrict the defect */
    693:     MatRestrict(restrct, F, B_c);

    695:     /* solve the coarse problem corresponding to F^c(x^c) = b^c = Rb + F^c(Rx) - RF(x) */
    696:     if (fasc->eventresidual) {PetscLogEventBegin(fasc->eventresidual,next,0,0,0);}
    697:     SNESComputeFunction(next, Xo_c, F_c);
    698:     if (fasc->eventresidual) {PetscLogEventEnd(fasc->eventresidual,next,0,0,0);}
    699:     VecCopy(B_c, X_c);
    700:     VecCopy(F_c, B_c);
    701:     VecCopy(X_c, F_c);
    702:     /* set initial guess of the coarse problem to the projected fine solution */
    703:     VecCopy(Xo_c, X_c);

    705:     /* recurse */
    706:     SNESSetInitialFunction(next, F_c);
    707:     SNESSolve(next, B_c, X_c);

    709:     /* smooth on this level */
    710:     SNESFASDownSmooth_Private(snes, B, X, F, &fnorm);

    712:     SNESGetConvergedReason(next,&reason);
    713:     if (reason < 0 && reason != SNES_DIVERGED_MAX_IT) {
    714:       snes->reason = SNES_DIVERGED_INNER;
    715:       return(0);
    716:     }

    718:     /* correct as x <- x + I(x^c - Rx)*/
    719:     VecAYPX(X_c, -1.0, Xo_c);
    720:     MatInterpolate(interpolate, X_c, Xhat);

    722:     /* additive correction of the coarse direction*/
    723:     SNESLineSearchApply(snes->linesearch, X, F, &fnorm, Xhat);
    724:     SNESLineSearchGetReason(snes->linesearch, &lsresult);
    725:     SNESLineSearchGetNorms(snes->linesearch, &xnorm, &snes->norm, &ynorm);
    726:     if (lsresult) {
    727:       if (++snes->numFailures >= snes->maxFailures) {
    728:         snes->reason = SNES_DIVERGED_LINE_SEARCH;
    729:         return(0);
    730:       }
    731:     }
    732:   } else {
    733:     SNESFASDownSmooth_Private(snes, B, X, F, &snes->norm);
    734:   }
    735:   return(0);
    736: }

    738: /*

    740: Defines the FAS cycle as:

    742: fine problem: F(x) = b
    743: coarse problem: F^c(x) = b^c

    745: b^c = F^c(Rx) - R(F(x) - b)

    747: correction:

    749: x = x + I(x^c - Rx)

    751:  */
    752: static PetscErrorCode SNESFASCycle_Multiplicative(SNES snes, Vec X)
    753: {

    756:   Vec            F,B;
    757:   SNES           next;

    760:   F = snes->vec_func;
    761:   B = snes->vec_rhs;
    762:   /* pre-smooth -- just update using the pre-smoother */
    763:   SNESFASCycleGetCorrection(snes, &next);
    764:   SNESFASDownSmooth_Private(snes, B, X, F, &snes->norm);
    765:   if (next) {
    766:     SNESFASCoarseCorrection(snes, X, F, X);
    767:     SNESFASUpSmooth_Private(snes, B, X, F, &snes->norm);
    768:   }
    769:   return(0);
    770: }

    772: static PetscErrorCode SNESFASCycleSetupPhase_Full(SNES snes)
    773: {
    774:   SNES           next;
    775:   SNES_FAS       *fas = (SNES_FAS*)snes->data;
    776:   PetscBool      isFine;

    780:   /* pre-smooth -- just update using the pre-smoother */
    781:   SNESFASCycleIsFine(snes,&isFine);
    782:   SNESFASCycleGetCorrection(snes,&next);
    783:   fas->full_stage = 0;
    784:   if (next) {SNESFASCycleSetupPhase_Full(next);}
    785:   return(0);
    786: }

    788: static PetscErrorCode SNESFASCycle_Full(SNES snes, Vec X)
    789: {
    791:   Vec            F,B;
    792:   SNES_FAS       *fas = (SNES_FAS*)snes->data;
    793:   PetscBool      isFine;
    794:   SNES           next;

    797:   F = snes->vec_func;
    798:   B = snes->vec_rhs;
    799:   SNESFASCycleIsFine(snes,&isFine);
    800:   SNESFASCycleGetCorrection(snes,&next);

    802:   if (isFine) {
    803:     SNESFASCycleSetupPhase_Full(snes);
    804:   }

    806:   if (fas->full_stage == 0) {
    807:     /* downsweep */
    808:     if (next) {
    809:       if (fas->level != 1) next->max_its += 1;
    810:       if (fas->full_downsweep) {SNESFASDownSmooth_Private(snes,B,X,F,&snes->norm);}
    811:       fas->full_downsweep = PETSC_TRUE;
    812:       if (fas->full_total) {SNESFASInterpolatedCoarseSolution(snes,X,X);}
    813:       else                 {SNESFASCoarseCorrection(snes,X,F,X);}
    814:       fas->full_total = PETSC_FALSE;
    815:       SNESFASUpSmooth_Private(snes,B,X,F,&snes->norm);
    816:       if (fas->level != 1) next->max_its -= 1;
    817:     } else {
    818:       /* The smoother on the coarse level is the coarse solver */
    819:       SNESFASDownSmooth_Private(snes,B,X,F,&snes->norm);
    820:     }
    821:     fas->full_stage = 1;
    822:   } else if (fas->full_stage == 1) {
    823:     if (snes->iter == 0) {SNESFASDownSmooth_Private(snes,B,X,F,&snes->norm);}
    824:     if (next) {
    825:       SNESFASCoarseCorrection(snes,X,F,X);
    826:       SNESFASUpSmooth_Private(snes,B,X,F,&snes->norm);
    827:     }
    828:   }
    829:   /* final v-cycle */
    830:   if (isFine) {
    831:     if (next) {
    832:       SNESFASCoarseCorrection(snes,X,F,X);
    833:       SNESFASUpSmooth_Private(snes,B,X,F,&snes->norm);
    834:     }
    835:   }
    836:   return(0);
    837: }

    839: static PetscErrorCode SNESFASCycle_Kaskade(SNES snes, Vec X)
    840: {
    842:   Vec            F,B;
    843:   SNES           next;

    846:   F = snes->vec_func;
    847:   B = snes->vec_rhs;
    848:   SNESFASCycleGetCorrection(snes,&next);
    849:   if (next) {
    850:     SNESFASCoarseCorrection(snes,X,F,X);
    851:     SNESFASUpSmooth_Private(snes,B,X,F,&snes->norm);
    852:   } else {
    853:     SNESFASDownSmooth_Private(snes,B,X,F,&snes->norm);
    854:   }
    855:   return(0);
    856: }

    858: PetscBool SNEScite = PETSC_FALSE;
    859: const char SNESCitation[] = "@techreport{pbmkbsxt2012,\n"
    860:                             "  title = {Composing Scalable Nonlinear Algebraic Solvers},\n"
    861:                             "  author = {Peter Brune and Mathew Knepley and Barry Smith and Xuemin Tu},\n"
    862:                             "  year = 2013,\n"
    863:                             "  type = Preprint,\n"
    864:                             "  number = {ANL/MCS-P2010-0112},\n"
    865:                             "  institution = {Argonne National Laboratory}\n}\n";

    867: static PetscErrorCode SNESSolve_FAS(SNES snes)
    868: {
    870:   PetscInt       i;
    871:   Vec            X, F;
    872:   PetscReal      fnorm;
    873:   SNES_FAS       *fas = (SNES_FAS*)snes->data,*ffas;
    874:   DM             dm;
    875:   PetscBool      isFine;

    878:   if (snes->xl || snes->xu || snes->ops->computevariablebounds) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE, "SNES solver %s does not support bounds", ((PetscObject)snes)->type_name);

    880:   PetscCitationsRegister(SNESCitation,&SNEScite);
    881:   snes->reason = SNES_CONVERGED_ITERATING;
    882:   X            = snes->vec_sol;
    883:   F            = snes->vec_func;

    885:   SNESFASCycleIsFine(snes, &isFine);
    886:   /* norm setup */
    887:   PetscObjectSAWsTakeAccess((PetscObject)snes);
    888:   snes->iter = 0;
    889:   snes->norm = 0;
    890:   PetscObjectSAWsGrantAccess((PetscObject)snes);
    891:   if (!snes->vec_func_init_set) {
    892:     if (fas->eventresidual) {PetscLogEventBegin(fas->eventresidual,snes,0,0,0);}
    893:     SNESComputeFunction(snes,X,F);
    894:     if (fas->eventresidual) {PetscLogEventEnd(fas->eventresidual,snes,0,0,0);}
    895:   } else snes->vec_func_init_set = PETSC_FALSE;

    897:   VecNorm(F, NORM_2, &fnorm); /* fnorm <- ||F||  */
    898:   SNESCheckFunctionNorm(snes,fnorm);
    899:   PetscObjectSAWsTakeAccess((PetscObject)snes);
    900:   snes->norm = fnorm;
    901:   PetscObjectSAWsGrantAccess((PetscObject)snes);
    902:   SNESLogConvergenceHistory(snes,fnorm,0);
    903:   SNESMonitor(snes,snes->iter,fnorm);

    905:   /* test convergence */
    906:   (*snes->ops->converged)(snes,0,0.0,0.0,fnorm,&snes->reason,snes->cnvP);
    907:   if (snes->reason) return(0);

    910:   if (isFine) {
    911:     /* propagate scale-dependent data up the hierarchy */
    912:     SNESGetDM(snes,&dm);
    913:     for (ffas=fas; ffas->next; ffas=(SNES_FAS*)ffas->next->data) {
    914:       DM dmcoarse;
    915:       SNESGetDM(ffas->next,&dmcoarse);
    916:       DMRestrict(dm,ffas->restrct,ffas->rscale,ffas->inject,dmcoarse);
    917:       dm   = dmcoarse;
    918:     }
    919:   }

    921:   for (i = 0; i < snes->max_its; i++) {
    922:     /* Call general purpose update function */
    923:     if (snes->ops->update) {
    924:       (*snes->ops->update)(snes, snes->iter);
    925:     }

    927:     if (fas->fastype == SNES_FAS_MULTIPLICATIVE) {
    928:       SNESFASCycle_Multiplicative(snes, X);
    929:     } else if (fas->fastype == SNES_FAS_ADDITIVE) {
    930:       SNESFASCycle_Additive(snes, X);
    931:     } else if (fas->fastype == SNES_FAS_FULL) {
    932:       SNESFASCycle_Full(snes, X);
    933:     } else if (fas->fastype == SNES_FAS_KASKADE) {
    934:       SNESFASCycle_Kaskade(snes, X);
    935:     } else SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONGSTATE,"Unsupported FAS type");

    937:     /* check for FAS cycle divergence */
    938:     if (snes->reason != SNES_CONVERGED_ITERATING) return(0);

    940:     /* Monitor convergence */
    941:     PetscObjectSAWsTakeAccess((PetscObject)snes);
    942:     snes->iter = i+1;
    943:     PetscObjectSAWsGrantAccess((PetscObject)snes);
    944:     SNESLogConvergenceHistory(snes,snes->norm,0);
    945:     SNESMonitor(snes,snes->iter,snes->norm);
    946:     /* Test for convergence */
    947:     if (isFine) {
    948:       (*snes->ops->converged)(snes,snes->iter,0.0,0.0,snes->norm,&snes->reason,snes->cnvP);
    949:       if (snes->reason) break;
    950:     }
    951:   }
    952:   if (i == snes->max_its) {
    953:     PetscInfo1(snes, "Maximum number of iterations has been reached: %D\n", i);
    954:     if (!snes->reason) snes->reason = SNES_DIVERGED_MAX_IT;
    955:   }
    956:   return(0);
    957: }

    959: /*MC

    961: SNESFAS - Full Approximation Scheme nonlinear multigrid solver.

    963:    The nonlinear problem is solved by correction using coarse versions
    964:    of the nonlinear problem.  This problem is perturbed so that a projected
    965:    solution of the fine problem elicits no correction from the coarse problem.

    967: Options Database:
    968: +   -snes_fas_levels -  The number of levels
    969: .   -snes_fas_cycles<1> -  The number of cycles -- 1 for V, 2 for W
    970: .   -snes_fas_type<additive,multiplicative,full,kaskade>  -  Additive or multiplicative cycle
    971: .   -snes_fas_galerkin<PETSC_FALSE> -  Form coarse problems by projection back upon the fine problem
    972: .   -snes_fas_smoothup<1> -  The number of iterations of the post-smoother
    973: .   -snes_fas_smoothdown<1> -  The number of iterations of the pre-smoother
    974: .   -snes_fas_monitor -  Monitor progress of all of the levels
    975: .   -snes_fas_full_downsweep<PETSC_FALSE> - call the downsmooth on the initial downsweep of full FAS
    976: .   -fas_levels_snes_ -  SNES options for all smoothers
    977: .   -fas_levels_cycle_snes_ -  SNES options for all cycles
    978: .   -fas_levels_i_snes_ -  SNES options for the smoothers on level i
    979: .   -fas_levels_i_cycle_snes_ - SNES options for the cycle on level i
    980: -   -fas_coarse_snes_ -  SNES options for the coarsest smoother

    982: Notes:
    983:    The organization of the FAS solver is slightly different from the organization of PCMG
    984:    As each level has smoother SNES instances(down and potentially up) and a cycle SNES instance.
    985:    The cycle SNES instance may be used for monitoring convergence on a particular level.

    987: Level: beginner

    989:    References:
    990: . 1. -  Peter R. Brune, Matthew G. Knepley, Barry F. Smith, and Xuemin Tu, "Composing Scalable Nonlinear Algebraic Solvers",
    991:    SIAM Review, 57(4), 2015

    993: .seealso: PCMG, SNESCreate(), SNES, SNESSetType(), SNESType (for list of available types)
    994: M*/

    996: PETSC_EXTERN PetscErrorCode SNESCreate_FAS(SNES snes)
    997: {
    998:   SNES_FAS       *fas;

    1002:   snes->ops->destroy        = SNESDestroy_FAS;
    1003:   snes->ops->setup          = SNESSetUp_FAS;
    1004:   snes->ops->setfromoptions = SNESSetFromOptions_FAS;
    1005:   snes->ops->view           = SNESView_FAS;
    1006:   snes->ops->solve          = SNESSolve_FAS;
    1007:   snes->ops->reset          = SNESReset_FAS;

    1009:   snes->usesksp = PETSC_FALSE;
    1010:   snes->usesnpc = PETSC_FALSE;

    1012:   if (!snes->tolerancesset) {
    1013:     snes->max_funcs = 30000;
    1014:     snes->max_its   = 10000;
    1015:   }

    1017:   snes->alwayscomputesfinalresidual = PETSC_TRUE;

    1019:   PetscNewLog(snes,&fas);

    1021:   snes->data                  = (void*) fas;
    1022:   fas->level                  = 0;
    1023:   fas->levels                 = 1;
    1024:   fas->n_cycles               = 1;
    1025:   fas->max_up_it              = 1;
    1026:   fas->max_down_it            = 1;
    1027:   fas->smoothu                = NULL;
    1028:   fas->smoothd                = NULL;
    1029:   fas->next                   = NULL;
    1030:   fas->previous               = NULL;
    1031:   fas->fine                   = snes;
    1032:   fas->interpolate            = NULL;
    1033:   fas->restrct                = NULL;
    1034:   fas->inject                 = NULL;
    1035:   fas->usedmfornumberoflevels = PETSC_FALSE;
    1036:   fas->fastype                = SNES_FAS_MULTIPLICATIVE;
    1037:   fas->full_downsweep         = PETSC_FALSE;
    1038:   fas->full_total             = PETSC_FALSE;

    1040:   fas->eventsmoothsetup    = 0;
    1041:   fas->eventsmoothsolve    = 0;
    1042:   fas->eventresidual       = 0;
    1043:   fas->eventinterprestrict = 0;
    1044:   return(0);
    1045: }