Date: 2021-03-03T22:27:49+00:00

Actual source code: convest.c
petsc-3.14.5 2021-03-03
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      1: #include <petscconvest.h>
      2: #include <petscdmplex.h>
      3: #include <petscds.h>

      5: #include <petsc/private/petscconvestimpl.h>

      7: static PetscErrorCode zero_private(PetscInt dim, PetscReal time, const PetscReal x[], PetscInt Nc, PetscScalar *u, void *ctx)
      8: {
      9:   PetscInt c;
     10:   for (c = 0; c < Nc; ++c) u[c] = 0.0;
     11:   return 0;
     12: }

     14: /*@
     15:   PetscConvEstDestroy - Destroys a PetscConvEst object

     17:   Collective on PetscConvEst

     19:   Input Parameter:
     20: . ce - The PetscConvEst object

     22:   Level: beginner

     24: .seealso: PetscConvEstCreate(), PetscConvEstGetConvRate()
     25: @*/
     26: PetscErrorCode PetscConvEstDestroy(PetscConvEst *ce)
     27: {

     31:   if (!*ce) return(0);
     33:   if (--((PetscObject)(*ce))->refct > 0) {
     34:     *ce = NULL;
     35:     return(0);
     36:   }
     37:   PetscFree3((*ce)->initGuess, (*ce)->exactSol, (*ce)->ctxs);
     38:   PetscFree((*ce)->errors);
     39:   PetscHeaderDestroy(ce);
     40:   return(0);
     41: }

     43: /*@
     44:   PetscConvEstSetFromOptions - Sets a PetscConvEst object from options

     46:   Collective on PetscConvEst

     48:   Input Parameters:
     49: . ce - The PetscConvEst object

     51:   Level: beginner

     53: .seealso: PetscConvEstCreate(), PetscConvEstGetConvRate()
     54: @*/
     55: PetscErrorCode PetscConvEstSetFromOptions(PetscConvEst ce)
     56: {

     60:   PetscOptionsBegin(PetscObjectComm((PetscObject) ce), "", "Convergence Estimator Options", "PetscConvEst");
     61:   PetscOptionsInt("-convest_num_refine", "The number of refinements for the convergence check", "PetscConvEst", ce->Nr, &ce->Nr, NULL);
     62:   PetscOptionsReal("-convest_refine_factor", "The increase in resolution in each dimension", "PetscConvEst", ce->r, &ce->r, NULL);
     63:   PetscOptionsBool("-convest_monitor", "Monitor the error for each convergence check", "PetscConvEst", ce->monitor, &ce->monitor, NULL);
     64:   PetscOptionsEnd();
     65:   return(0);
     66: }

     68: /*@
     69:   PetscConvEstView - Views a PetscConvEst object

     71:   Collective on PetscConvEst

     73:   Input Parameters:
     74: + ce     - The PetscConvEst object
     75: - viewer - The PetscViewer object

     77:   Level: beginner

     79: .seealso: PetscConvEstCreate(), PetscConvEstGetConvRate()
     80: @*/
     81: PetscErrorCode PetscConvEstView(PetscConvEst ce, PetscViewer viewer)
     82: {

     86:   PetscObjectPrintClassNamePrefixType((PetscObject) ce, viewer);
     87:   PetscViewerASCIIPrintf(viewer, "ConvEst with %D levels\n", ce->Nr+1);
     88:   return(0);
     89: }

     91: /*@
     92:   PetscConvEstGetSolver - Gets the solver used to produce discrete solutions

     94:   Not collective

     96:   Input Parameter:
     97: . ce     - The PetscConvEst object

     99:   Output Parameter:
    100: . solver - The solver

    102:   Level: intermediate

    104: .seealso: PetscConvEstSetSolver(), PetscConvEstCreate(), PetscConvEstGetConvRate()
    105: @*/
    106: PetscErrorCode PetscConvEstGetSolver(PetscConvEst ce, PetscObject *solver)
    107: {
    111:   *solver = ce->solver;
    112:   return(0);
    113: }

    115: /*@
    116:   PetscConvEstSetSolver - Sets the solver used to produce discrete solutions

    118:   Not collective

    120:   Input Parameters:
    121: + ce     - The PetscConvEst object
    122: - solver - The solver

    124:   Level: intermediate

    126:   Note: The solver MUST have an attached DM/DS, so that we know the exact solution

    128: .seealso: PetscConvEstGetSNES(), PetscConvEstCreate(), PetscConvEstGetConvRate()
    129: @*/
    130: PetscErrorCode PetscConvEstSetSolver(PetscConvEst ce, PetscObject solver)
    131: {

    137:   ce->solver = solver;
    138:   (*ce->ops->setsolver)(ce, solver);
    139:   return(0);
    140: }

    142: /*@
    143:   PetscConvEstSetUp - After the solver is specified, we create structures for estimating convergence

    145:   Collective on PetscConvEst

    147:   Input Parameters:
    148: . ce - The PetscConvEst object

    150:   Level: beginner

    152: .seealso: PetscConvEstCreate(), PetscConvEstGetConvRate()
    153: @*/
    154: PetscErrorCode PetscConvEstSetUp(PetscConvEst ce)
    155: {
    156:   PetscInt       Nf, f, Nds, s;

    160:   DMGetNumFields(ce->idm, &Nf);
    161:   ce->Nf = PetscMax(Nf, 1);
    162:   PetscMalloc1((ce->Nr+1)*ce->Nf, &ce->errors);
    163:   PetscCalloc3(ce->Nf, &ce->initGuess, ce->Nf, &ce->exactSol, ce->Nf, &ce->ctxs);
    164:   for (f = 0; f < Nf; ++f) ce->initGuess[f] = zero_private;
    165:   DMGetNumDS(ce->idm, &Nds);
    166:   for (s = 0; s < Nds; ++s) {
    167:     PetscDS         ds;
    168:     DMLabel         label;
    169:     IS              fieldIS;
    170:     const PetscInt *fields;
    171:     PetscInt        dsNf;

    173:     DMGetRegionNumDS(ce->idm, s, &label, &fieldIS, &ds);
    174:     PetscDSGetNumFields(ds, &dsNf);
    175:     if (fieldIS) {ISGetIndices(fieldIS, &fields);}
    176:     for (f = 0; f < dsNf; ++f) {
    177:       const PetscInt field = fields[f];
    178:       PetscDSGetExactSolution(ds, field, &ce->exactSol[field], &ce->ctxs[field]);
    179:     }
    180:     if (fieldIS) {ISRestoreIndices(fieldIS, &fields);}
    181:   }
    182:   for (f = 0; f < Nf; ++f) {
    183:     if (!ce->exactSol[f]) SETERRQ1(PetscObjectComm((PetscObject) ce), PETSC_ERR_ARG_WRONG, "DS must contain exact solution functions in order to estimate convergence, missing for field %D", f);
    184:   }
    185:   return(0);
    186: }

    188: PetscErrorCode PetscConvEstComputeInitialGuess(PetscConvEst ce, PetscInt r, DM dm, Vec u)
    189: {

    196:   (*ce->ops->initguess)(ce, r, dm, u);
    197:   return(0);
    198: }

    200: PetscErrorCode PetscConvEstComputeError(PetscConvEst ce, PetscInt r, DM dm, Vec u, PetscReal errors[])
    201: {

    209:   (*ce->ops->computeerror)(ce, r, dm, u, errors);
    210:   return(0);
    211: }

    213: /*@
    214:   PetscConvEstMonitorDefault - Monitors the convergence estimation loop

    216:   Collective on PetscConvEst

    218:   Input Parameter:
    219: + ce - The PetscConvEst object
    220: - r  - The refinement level

    222:   Options database keys:
    223: . -convest_monitor - Activate the monitor

    225:   Level: intermediate

    227: .seealso: PetscConvEstCreate(), PetscConvEstGetConvRate(), SNESSolve(), TSSolve()
    228: @*/
    229: PetscErrorCode PetscConvEstMonitorDefault(PetscConvEst ce, PetscInt r)
    230: {
    231:   MPI_Comm       comm;
    232:   PetscInt       f;

    236:   if (ce->monitor) {
    237:     PetscReal *errors = &ce->errors[r*ce->Nf];

    239:     PetscObjectGetComm((PetscObject) ce, &comm);
    240:     PetscPrintf(comm, "L_2 Error: ");
    241:     if (ce->Nf > 1) {PetscPrintf(comm, "[");}
    242:     for (f = 0; f < ce->Nf; ++f) {
    243:       if (f > 0) {PetscPrintf(comm, ", ");}
    244:       if (errors[f] < 1.0e-11) {PetscPrintf(comm, "< 1e-11");}
    245:       else                     {PetscPrintf(comm, "%g", (double) errors[f]);}
    246:     }
    247:     if (ce->Nf > 1) {PetscPrintf(comm, "]");}
    248:     PetscPrintf(comm, "\n");
    249:   }
    250:   return(0);
    251: }

    253: static PetscErrorCode PetscConvEstSetSNES_Private(PetscConvEst ce, PetscObject solver)
    254: {
    255:   PetscClassId   id;

    259:   PetscObjectGetClassId(ce->solver, &id);
    260:   if (id != SNES_CLASSID) SETERRQ(PetscObjectComm((PetscObject) ce), PETSC_ERR_ARG_WRONG, "Solver was not a SNES");
    261:   SNESGetDM((SNES) ce->solver, &ce->idm);
    262:   return(0);
    263: }

    265: static PetscErrorCode PetscConvEstInitGuessSNES_Private(PetscConvEst ce, PetscInt r, DM dm, Vec u)
    266: {

    270:   DMProjectFunction(dm, 0.0, ce->initGuess, ce->ctxs, INSERT_VALUES, u);
    271:   return(0);
    272: }

    274: static PetscErrorCode PetscConvEstComputeErrorSNES_Private(PetscConvEst ce, PetscInt r, DM dm, Vec u, PetscReal errors[])
    275: {

    279:   DMComputeL2FieldDiff(dm, 0.0, ce->exactSol, ce->ctxs, u, errors);
    280:   return(0);
    281: }

    283: static PetscErrorCode PetscConvEstGetConvRateSNES_Private(PetscConvEst ce, PetscReal alpha[])
    284: {
    285:   SNES           snes = (SNES) ce->solver;
    286:   DM            *dm;
    287:   PetscObject    disc;
    288:   PetscReal     *x, *y, slope, intercept;
    289:   PetscInt      *dof, Nr = ce->Nr, r, f, dim, oldlevel, oldnlev;
    290:   void          *ctx;

    294:   if (ce->r != 2.0) SETERRQ1(PetscObjectComm((PetscObject) ce), PETSC_ERR_SUP, "Only refinement factor 2 is currently supported (not %g)", (double) ce->r);
    295:   DMGetDimension(ce->idm, &dim);
    296:   DMGetApplicationContext(ce->idm, &ctx);
    297:   DMPlexSetRefinementUniform(ce->idm, PETSC_TRUE);
    298:   DMGetRefineLevel(ce->idm, &oldlevel);
    299:   PetscMalloc2((Nr+1), &dm, (Nr+1)*ce->Nf, &dof);
    300:   /* Loop over meshes */
    301:   dm[0] = ce->idm;
    302:   for (r = 0; r <= Nr; ++r) {
    303:     Vec           u;
    304: #if defined(PETSC_USE_LOG)
    305:     PetscLogStage stage;
    306: #endif
    307:     char          stageName[PETSC_MAX_PATH_LEN];
    308:     const char   *dmname, *uname;

    310:     PetscSNPrintf(stageName, PETSC_MAX_PATH_LEN-1, "ConvEst Refinement Level %D", r);
    311:     PetscLogStageRegister(stageName, &stage);
    312:     PetscLogStagePush(stage);
    313:     if (r > 0) {
    314:       DMRefine(dm[r-1], MPI_COMM_NULL, &dm[r]);
    315:       DMSetCoarseDM(dm[r], dm[r-1]);
    316:       DMCopyTransform(ce->idm, dm[r]);
    317:       PetscObjectGetName((PetscObject) dm[r-1], &dmname);
    318:       PetscObjectSetName((PetscObject) dm[r], dmname);
    319:       for (f = 0; f <= ce->Nf; ++f) {
    320:         PetscErrorCode (*nspconstr)(DM, PetscInt, PetscInt, MatNullSpace *);

    322:         DMGetNullSpaceConstructor(dm[r-1], f, &nspconstr);
    323:         DMSetNullSpaceConstructor(dm[r],   f,  nspconstr);
    324:       }
    325:     }
    326:     DMViewFromOptions(dm[r], NULL, "-conv_dm_view");
    327:     /* Create solution */
    328:     DMCreateGlobalVector(dm[r], &u);
    329:     DMGetField(dm[r], 0, NULL, &disc);
    330:     PetscObjectGetName(disc, &uname);
    331:     PetscObjectSetName((PetscObject) u, uname);
    332:     /* Setup solver */
    333:     SNESReset(snes);
    334:     SNESSetDM(snes, dm[r]);
    335:     DMPlexSetSNESLocalFEM(dm[r], ctx, ctx, ctx);
    336:     SNESSetFromOptions(snes);
    337:     /* Create initial guess */
    338:     PetscConvEstComputeInitialGuess(ce, r, dm[r], u);
    339:     SNESSolve(snes, NULL, u);
    340:     PetscLogEventBegin(ce->event, ce, 0, 0, 0);
    341:     PetscConvEstComputeError(ce, r, dm[r], u, &ce->errors[r*ce->Nf]);
    342:     PetscLogEventEnd(ce->event, ce, 0, 0, 0);
    343:     for (f = 0; f < ce->Nf; ++f) {
    344:       PetscSection s, fs;
    345:       PetscInt     lsize;

    347:       /* Could use DMGetOutputDM() to add in Dirichlet dofs */
    348:       DMGetLocalSection(dm[r], &s);
    349:       PetscSectionGetField(s, f, &fs);
    350:       PetscSectionGetConstrainedStorageSize(fs, &lsize);
    351:       MPI_Allreduce(&lsize, &dof[r*ce->Nf+f], 1, MPIU_INT, MPI_SUM, PetscObjectComm((PetscObject) snes));
    352:       PetscLogEventSetDof(ce->event, f, dof[r*ce->Nf+f]);
    353:       PetscLogEventSetError(ce->event, f, ce->errors[r*ce->Nf+f]);
    354:     }
    355:     /* Monitor */
    356:     PetscConvEstMonitorDefault(ce, r);
    357:     if (!r) {
    358:       /* PCReset() does not wipe out the level structure */
    359:       KSP ksp;
    360:       PC  pc;

    362:       SNESGetKSP(snes, &ksp);
    363:       KSPGetPC(ksp, &pc);
    364:       PCMGGetLevels(pc, &oldnlev);
    365:     }
    366:     /* Cleanup */
    367:     VecDestroy(&u);
    368:     PetscLogStagePop();
    369:   }
    370:   for (r = 1; r <= Nr; ++r) {
    371:     DMDestroy(&dm[r]);
    372:   }
    373:   /* Fit convergence rate */
    374:   PetscMalloc2(Nr+1, &x, Nr+1, &y);
    375:   for (f = 0; f < ce->Nf; ++f) {
    376:     for (r = 0; r <= Nr; ++r) {
    377:       x[r] = PetscLog10Real(dof[r*ce->Nf+f]);
    378:       y[r] = PetscLog10Real(ce->errors[r*ce->Nf+f]);
    379:     }
    380:     PetscLinearRegression(Nr+1, x, y, &slope, &intercept);
    381:     /* Since h^{-dim} = N, lg err = s lg N + b = -s dim lg h + b */
    382:     alpha[f] = -slope * dim;
    383:   }
    384:   PetscFree2(x, y);
    385:   PetscFree2(dm, dof);
    386:   /* Restore solver */
    387:   SNESReset(snes);
    388:   {
    389:     /* PCReset() does not wipe out the level structure */
    390:     KSP ksp;
    391:     PC  pc;

    393:     SNESGetKSP(snes, &ksp);
    394:     KSPGetPC(ksp, &pc);
    395:     PCMGSetLevels(pc, oldnlev, NULL);
    396:     DMSetRefineLevel(ce->idm, oldlevel); /* The damn DMCoarsen() calls in PCMG can reset this */
    397:   }
    398:   SNESSetDM(snes, ce->idm);
    399:   DMPlexSetSNESLocalFEM(ce->idm, ctx, ctx, ctx);
    400:   SNESSetFromOptions(snes);
    401:   return(0);
    402: }

    404: /*@
    405:   PetscConvEstGetConvRate - Returns an estimate of the convergence rate for the discretization

    407:   Not collective

    409:   Input Parameter:
    410: . ce   - The PetscConvEst object

    412:   Output Parameter:
    413: . alpha - The convergence rate for each field

    415:   Note: The convergence rate alpha is defined by
    416: $ || u_\Delta - u_exact || < C \Delta^alpha
    417: where u_\Delta is the discrete solution, and Delta is a measure of the discretization size. We usually use h for the
    418: spatial resolution and \Delta t for the temporal resolution.

    420: We solve a series of problems using increasing resolution (refined meshes or decreased timesteps), calculate an error
    421: based upon the exact solution in the DS, and then fit the result to our model above using linear regression.

    423:   Options database keys:
    424: + -snes_convergence_estimate : Execute convergence estimation inside SNESSolve() and print out the rate
    425: - -ts_convergence_estimate : Execute convergence estimation inside TSSolve() and print out the rate

    427:   Level: intermediate

    429: .seealso: PetscConvEstSetSolver(), PetscConvEstCreate(), PetscConvEstGetConvRate(), SNESSolve(), TSSolve()
    430: @*/
    431: PetscErrorCode PetscConvEstGetConvRate(PetscConvEst ce, PetscReal alpha[])
    432: {
    433:   PetscInt       f;

    437:   if (ce->event < 0) {PetscLogEventRegister("ConvEst Error", PETSC_OBJECT_CLASSID, &ce->event);}
    438:   for (f = 0; f < ce->Nf; ++f) alpha[f] = 0.0;
    439:   (*ce->ops->getconvrate)(ce, alpha);
    440:   return(0);
    441: }

    443: /*@
    444:   PetscConvEstRateView - Displays the convergence rate to a viewer

    446:    Collective on SNES

    448:    Parameter:
    449: +  snes - iterative context obtained from SNESCreate()
    450: .  alpha - the convergence rate for each field
    451: -  viewer - the viewer to display the reason

    453:    Options Database Keys:
    454: .  -snes_convergence_estimate - print the convergence rate

    456:    Level: developer

    458: .seealso: PetscConvEstGetRate()
    459: @*/
    460: PetscErrorCode PetscConvEstRateView(PetscConvEst ce, const PetscReal alpha[], PetscViewer viewer)
    461: {
    462:   PetscBool      isAscii;

    466:   PetscObjectTypeCompare((PetscObject) viewer, PETSCVIEWERASCII, &isAscii);
    467:   if (isAscii) {
    468:     PetscInt Nf = ce->Nf, f;

    470:     PetscViewerASCIIAddTab(viewer, ((PetscObject) ce)->tablevel);
    471:     PetscViewerASCIIPrintf(viewer, "L_2 convergence rate: ");
    472:     if (Nf > 1) {PetscViewerASCIIPrintf(viewer, "[");}
    473:     for (f = 0; f < Nf; ++f) {
    474:       if (f > 0) {PetscViewerASCIIPrintf(viewer, ", ");}
    475:       PetscViewerASCIIPrintf(viewer, "%#.2g", (double) alpha[f]);
    476:     }
    477:     if (Nf > 1) {PetscViewerASCIIPrintf(viewer, "]");}
    478:     PetscViewerASCIIPrintf(viewer, "\n");
    479:     PetscViewerASCIISubtractTab(viewer, ((PetscObject) ce)->tablevel);
    480:   }
    481:   return(0);
    482: }

    484: /*@
    485:   PetscConvEstCreate - Create a PetscConvEst object

    487:   Collective

    489:   Input Parameter:
    490: . comm - The communicator for the PetscConvEst object

    492:   Output Parameter:
    493: . ce   - The PetscConvEst object

    495:   Level: beginner

    497: .seealso: PetscConvEstDestroy(), PetscConvEstGetConvRate()
    498: @*/
    499: PetscErrorCode PetscConvEstCreate(MPI_Comm comm, PetscConvEst *ce)
    500: {

    505:   PetscSysInitializePackage();
    506:   PetscHeaderCreate(*ce, PETSC_OBJECT_CLASSID, "PetscConvEst", "ConvergenceEstimator", "SNES", comm, PetscConvEstDestroy, PetscConvEstView);
    507:   (*ce)->monitor = PETSC_FALSE;
    508:   (*ce)->r       = 2.0;
    509:   (*ce)->Nr      = 4;
    510:   (*ce)->event   = -1;
    511:   (*ce)->ops->setsolver    = PetscConvEstSetSNES_Private;
    512:   (*ce)->ops->initguess    = PetscConvEstInitGuessSNES_Private;
    513:   (*ce)->ops->computeerror = PetscConvEstComputeErrorSNES_Private;
    514:   (*ce)->ops->getconvrate  = PetscConvEstGetConvRateSNES_Private;
    515:   return(0);
    516: }