Actual source code: sor.c

  1: /*
  2:    Defines a  (S)SOR  preconditioner for any Mat implementation
  3: */
  4: #include <petsc/private/pcimpl.h>

  6: typedef struct {
  7:   PetscInt   its;  /* inner iterations, number of sweeps */
  8:   PetscInt   lits; /* local inner iterations, number of sweeps applied by the local matrix mat->A */
  9:   MatSORType sym;  /* forward, reverse, symmetric etc. */
 10:   PetscReal  omega;
 11:   PetscReal  fshift;
 12: } PC_SOR;

 14: static PetscErrorCode PCDestroy_SOR(PC pc)
 15: {
 16:   PetscObjectComposeFunction((PetscObject)pc, "PCSORSetSymmetric_C", NULL);
 17:   PetscObjectComposeFunction((PetscObject)pc, "PCSORSetOmega_C", NULL);
 18:   PetscObjectComposeFunction((PetscObject)pc, "PCSORSetIterations_C", NULL);
 19:   PetscObjectComposeFunction((PetscObject)pc, "PCSORGetSymmetric_C", NULL);
 20:   PetscObjectComposeFunction((PetscObject)pc, "PCSORGetOmega_C", NULL);
 21:   PetscObjectComposeFunction((PetscObject)pc, "PCSORGetIterations_C", NULL);
 22:   PetscFree(pc->data);
 23:   return 0;
 24: }

 26: static PetscErrorCode PCApply_SOR(PC pc, Vec x, Vec y)
 27: {
 28:   PC_SOR  *jac  = (PC_SOR *)pc->data;
 29:   PetscInt flag = jac->sym | SOR_ZERO_INITIAL_GUESS;

 31:   MatSOR(pc->pmat, x, jac->omega, (MatSORType)flag, jac->fshift, jac->its, jac->lits, y);
 32:   MatFactorGetError(pc->pmat, (MatFactorError *)&pc->failedreason);
 33:   return 0;
 34: }

 36: static PetscErrorCode PCApplyTranspose_SOR(PC pc, Vec x, Vec y)
 37: {
 38:   PC_SOR   *jac  = (PC_SOR *)pc->data;
 39:   PetscInt  flag = jac->sym | SOR_ZERO_INITIAL_GUESS;
 40:   PetscBool set, sym;

 42:   MatIsSymmetricKnown(pc->pmat, &set, &sym);
 44:   MatSOR(pc->pmat, x, jac->omega, (MatSORType)flag, jac->fshift, jac->its, jac->lits, y);
 45:   MatFactorGetError(pc->pmat, (MatFactorError *)&pc->failedreason);
 46:   return 0;
 47: }

 49: static PetscErrorCode PCApplyRichardson_SOR(PC pc, Vec b, Vec y, Vec w, PetscReal rtol, PetscReal abstol, PetscReal dtol, PetscInt its, PetscBool guesszero, PetscInt *outits, PCRichardsonConvergedReason *reason)
 50: {
 51:   PC_SOR    *jac   = (PC_SOR *)pc->data;
 52:   MatSORType stype = jac->sym;

 54:   PetscInfo(pc, "Warning, convergence criteria ignored, using %" PetscInt_FMT " iterations\n", its);
 55:   if (guesszero) stype = (MatSORType)(stype | SOR_ZERO_INITIAL_GUESS);
 56:   MatSOR(pc->pmat, b, jac->omega, stype, jac->fshift, its * jac->its, jac->lits, y);
 57:   MatFactorGetError(pc->pmat, (MatFactorError *)&pc->failedreason);
 58:   *outits = its;
 59:   *reason = PCRICHARDSON_CONVERGED_ITS;
 60:   return 0;
 61: }

 63: PetscErrorCode PCSetFromOptions_SOR(PC pc, PetscOptionItems *PetscOptionsObject)
 64: {
 65:   PC_SOR   *jac = (PC_SOR *)pc->data;
 66:   PetscBool flg;

 68:   PetscOptionsHeadBegin(PetscOptionsObject, "(S)SOR options");
 69:   PetscOptionsReal("-pc_sor_omega", "relaxation factor (0 < omega < 2)", "PCSORSetOmega", jac->omega, &jac->omega, NULL);
 70:   PetscOptionsReal("-pc_sor_diagonal_shift", "Add to the diagonal entries", "", jac->fshift, &jac->fshift, NULL);
 71:   PetscOptionsInt("-pc_sor_its", "number of inner SOR iterations", "PCSORSetIterations", jac->its, &jac->its, NULL);
 72:   PetscOptionsInt("-pc_sor_lits", "number of local inner SOR iterations", "PCSORSetIterations", jac->lits, &jac->lits, NULL);
 73:   PetscOptionsBoolGroupBegin("-pc_sor_symmetric", "SSOR, not SOR", "PCSORSetSymmetric", &flg);
 74:   if (flg) PCSORSetSymmetric(pc, SOR_SYMMETRIC_SWEEP);
 75:   PetscOptionsBoolGroup("-pc_sor_backward", "use backward sweep instead of forward", "PCSORSetSymmetric", &flg);
 76:   if (flg) PCSORSetSymmetric(pc, SOR_BACKWARD_SWEEP);
 77:   PetscOptionsBoolGroup("-pc_sor_forward", "use forward sweep", "PCSORSetSymmetric", &flg);
 78:   if (flg) PCSORSetSymmetric(pc, SOR_FORWARD_SWEEP);
 79:   PetscOptionsBoolGroup("-pc_sor_local_symmetric", "use SSOR separately on each processor", "PCSORSetSymmetric", &flg);
 80:   if (flg) PCSORSetSymmetric(pc, SOR_LOCAL_SYMMETRIC_SWEEP);
 81:   PetscOptionsBoolGroup("-pc_sor_local_backward", "use backward sweep locally", "PCSORSetSymmetric", &flg);
 82:   if (flg) PCSORSetSymmetric(pc, SOR_LOCAL_BACKWARD_SWEEP);
 83:   PetscOptionsBoolGroupEnd("-pc_sor_local_forward", "use forward sweep locally", "PCSORSetSymmetric", &flg);
 84:   if (flg) PCSORSetSymmetric(pc, SOR_LOCAL_FORWARD_SWEEP);
 85:   PetscOptionsHeadEnd();
 86:   return 0;
 87: }

 89: PetscErrorCode PCView_SOR(PC pc, PetscViewer viewer)
 90: {
 91:   PC_SOR     *jac = (PC_SOR *)pc->data;
 92:   MatSORType  sym = jac->sym;
 93:   const char *sortype;
 94:   PetscBool   iascii;

 96:   PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii);
 97:   if (iascii) {
 98:     if (sym & SOR_ZERO_INITIAL_GUESS) PetscViewerASCIIPrintf(viewer, "  zero initial guess\n");
 99:     if (sym == SOR_APPLY_UPPER) sortype = "apply_upper";
100:     else if (sym == SOR_APPLY_LOWER) sortype = "apply_lower";
101:     else if (sym & SOR_EISENSTAT) sortype = "Eisenstat";
102:     else if ((sym & SOR_SYMMETRIC_SWEEP) == SOR_SYMMETRIC_SWEEP) sortype = "symmetric";
103:     else if (sym & SOR_BACKWARD_SWEEP) sortype = "backward";
104:     else if (sym & SOR_FORWARD_SWEEP) sortype = "forward";
105:     else if ((sym & SOR_LOCAL_SYMMETRIC_SWEEP) == SOR_LOCAL_SYMMETRIC_SWEEP) sortype = "local_symmetric";
106:     else if (sym & SOR_LOCAL_FORWARD_SWEEP) sortype = "local_forward";
107:     else if (sym & SOR_LOCAL_BACKWARD_SWEEP) sortype = "local_backward";
108:     else sortype = "unknown";
109:     PetscViewerASCIIPrintf(viewer, "  type = %s, iterations = %" PetscInt_FMT ", local iterations = %" PetscInt_FMT ", omega = %g\n", sortype, jac->its, jac->lits, (double)jac->omega);
110:   }
111:   return 0;
112: }

114: static PetscErrorCode PCSORSetSymmetric_SOR(PC pc, MatSORType flag)
115: {
116:   PC_SOR *jac = (PC_SOR *)pc->data;

118:   jac->sym = flag;
119:   return 0;
120: }

122: static PetscErrorCode PCSORSetOmega_SOR(PC pc, PetscReal omega)
123: {
124:   PC_SOR *jac = (PC_SOR *)pc->data;

127:   jac->omega = omega;
128:   return 0;
129: }

131: static PetscErrorCode PCSORSetIterations_SOR(PC pc, PetscInt its, PetscInt lits)
132: {
133:   PC_SOR *jac = (PC_SOR *)pc->data;

135:   jac->its  = its;
136:   jac->lits = lits;
137:   return 0;
138: }

140: static PetscErrorCode PCSORGetSymmetric_SOR(PC pc, MatSORType *flag)
141: {
142:   PC_SOR *jac = (PC_SOR *)pc->data;

144:   *flag = jac->sym;
145:   return 0;
146: }

148: static PetscErrorCode PCSORGetOmega_SOR(PC pc, PetscReal *omega)
149: {
150:   PC_SOR *jac = (PC_SOR *)pc->data;

152:   *omega = jac->omega;
153:   return 0;
154: }

156: static PetscErrorCode PCSORGetIterations_SOR(PC pc, PetscInt *its, PetscInt *lits)
157: {
158:   PC_SOR *jac = (PC_SOR *)pc->data;

160:   if (its) *its = jac->its;
161:   if (lits) *lits = jac->lits;
162:   return 0;
163: }

165: /*@
166:    PCSORGetSymmetric - Gets the form the SOR preconditioner is using;   backward, or forward relaxation.  The local variants perform SOR on
167:    each processor.  By default forward relaxation is used.

169:    Logically Collective

171:    Input Parameter:
172: .  pc - the preconditioner context

174:    Output Parameter:
175: .  flag - one of the following
176: .vb
177:     SOR_FORWARD_SWEEP
178:     SOR_BACKWARD_SWEEP
179:     SOR_SYMMETRIC_SWEEP
180:     SOR_LOCAL_FORWARD_SWEEP
181:     SOR_LOCAL_BACKWARD_SWEEP
182:     SOR_LOCAL_SYMMETRIC_SWEEP
183: .ve

185:    Options Database Keys:
186: +  -pc_sor_symmetric - Activates symmetric version
187: .  -pc_sor_backward - Activates backward version
188: .  -pc_sor_local_forward - Activates local forward version
189: .  -pc_sor_local_symmetric - Activates local symmetric version
190: -  -pc_sor_local_backward - Activates local backward version

192:    Note:
193:    To use the Eisenstat trick with SSOR, employ the `PCEISENSTAT` preconditioner,
194:    which can be chosen with the option
195: .  -pc_type eisenstat - Activates Eisenstat trick

197:    Level: intermediate

199: .seealso: `PCSOR`, `PCEisenstatSetOmega()`, `PCSORSetIterations()`, `PCSORSetOmega()`, `PCSORSetSymmetric()`
200: @*/
201: PetscErrorCode PCSORGetSymmetric(PC pc, MatSORType *flag)
202: {
204:   PetscUseMethod(pc, "PCSORGetSymmetric_C", (PC, MatSORType *), (pc, flag));
205:   return 0;
206: }

208: /*@
209:    PCSORGetOmega - Gets the SOR relaxation coefficient, omega
210:    (where omega = 1.0 by default).

212:    Logically Collective

214:    Input Parameter:
215: .  pc - the preconditioner context

217:    Output Parameter:
218: .  omega - relaxation coefficient (0 < omega < 2).

220:    Options Database Key:
221: .  -pc_sor_omega <omega> - Sets omega

223:    Level: intermediate

225: .seealso: `PCSOR`, `PCSORSetSymmetric()`, `PCSORSetIterations()`, `PCEisenstatSetOmega()`, `PCSORSetOmega()`
226: @*/
227: PetscErrorCode PCSORGetOmega(PC pc, PetscReal *omega)
228: {
230:   PetscUseMethod(pc, "PCSORGetOmega_C", (PC, PetscReal *), (pc, omega));
231:   return 0;
232: }

234: /*@
235:    PCSORGetIterations - Gets the number of inner iterations to
236:    be used by the SOR preconditioner. The default is 1.

238:    Logically Collective

240:    Input Parameter:
241: .  pc - the preconditioner context

243:    Output Parameters:
244: +  lits - number of local iterations, smoothings over just variables on processor
245: -  its - number of parallel iterations to use; each parallel iteration has lits local iterations

247:    Options Database Keys:
248: +  -pc_sor_its <its> - Sets number of iterations
249: -  -pc_sor_lits <lits> - Sets number of local iterations

251:    Level: intermediate

253:    Note:
254:     When run on one processor the number of smoothings is lits*its

256: .seealso: `PCSOR`, `PCSORSetOmega()`, `PCSORSetSymmetric()`, `PCSORSetIterations()`
257: @*/
258: PetscErrorCode PCSORGetIterations(PC pc, PetscInt *its, PetscInt *lits)
259: {
261:   PetscUseMethod(pc, "PCSORGetIterations_C", (PC, PetscInt *, PetscInt *), (pc, its, lits));
262:   return 0;
263: }

265: /*@
266:    PCSORSetSymmetric - Sets the SOR preconditioner to use symmetric (SSOR),
267:    backward, or forward relaxation.  The local variants perform SOR on
268:    each processor.  By default forward relaxation is used.

270:    Logically Collective

272:    Input Parameters:
273: +  pc - the preconditioner context
274: -  flag - one of the following
275: .vb
276:     SOR_FORWARD_SWEEP
277:     SOR_BACKWARD_SWEEP
278:     SOR_SYMMETRIC_SWEEP
279:     SOR_LOCAL_FORWARD_SWEEP
280:     SOR_LOCAL_BACKWARD_SWEEP
281:     SOR_LOCAL_SYMMETRIC_SWEEP
282: .ve

284:    Options Database Keys:
285: +  -pc_sor_symmetric - Activates symmetric version
286: .  -pc_sor_backward - Activates backward version
287: .  -pc_sor_local_forward - Activates local forward version
288: .  -pc_sor_local_symmetric - Activates local symmetric version
289: -  -pc_sor_local_backward - Activates local backward version

291:    Note:
292:    To use the Eisenstat trick with SSOR, employ the PCEISENSTAT preconditioner,
293:    which can be chosen with the option
294: .  -pc_type eisenstat - Activates Eisenstat trick

296:    Level: intermediate

298: .seealso: `PCSOR`, `PCEisenstatSetOmega()`, `PCSORSetIterations()`, `PCSORSetOmega()`
299: @*/
300: PetscErrorCode PCSORSetSymmetric(PC pc, MatSORType flag)
301: {
304:   PetscTryMethod(pc, "PCSORSetSymmetric_C", (PC, MatSORType), (pc, flag));
305:   return 0;
306: }

308: /*@
309:    PCSORSetOmega - Sets the SOR relaxation coefficient, omega
310:    (where omega = 1.0 by default).

312:    Logically Collective

314:    Input Parameters:
315: +  pc - the preconditioner context
316: -  omega - relaxation coefficient (0 < omega < 2).

318:    Options Database Key:
319: .  -pc_sor_omega <omega> - Sets omega

321:    Level: intermediate

323:    Note:
324:    If omega != 1, you will need to set the `MAT_USE_INODE`S option to `PETSC_FALSE` on the matrix.

326: .seealso: `PCSOR`, `PCSORSetSymmetric()`, `PCSORSetIterations()`, `PCEisenstatSetOmega()`, `MatSetOption()`
327: @*/
328: PetscErrorCode PCSORSetOmega(PC pc, PetscReal omega)
329: {
332:   PetscTryMethod(pc, "PCSORSetOmega_C", (PC, PetscReal), (pc, omega));
333:   return 0;
334: }

336: /*@
337:    PCSORSetIterations - Sets the number of inner iterations to
338:    be used by the SOR preconditioner. The default is 1.

340:    Logically Collective

342:    Input Parameters:
343: +  pc - the preconditioner context
344: .  lits - number of local iterations, smoothings over just variables on processor
345: -  its - number of parallel iterations to use; each parallel iteration has lits local iterations

347:    Options Database Keys:
348: +  -pc_sor_its <its> - Sets number of iterations
349: -  -pc_sor_lits <lits> - Sets number of local iterations

351:    Level: intermediate

353:    Note:
354:     When run on one processor the number of smoothings is lits*its

356: .seealso: `PCSOR`, `PCSORSetOmega()`, `PCSORSetSymmetric()`
357: @*/
358: PetscErrorCode PCSORSetIterations(PC pc, PetscInt its, PetscInt lits)
359: {
362:   PetscTryMethod(pc, "PCSORSetIterations_C", (PC, PetscInt, PetscInt), (pc, its, lits));
363:   return 0;
364: }

366: /*MC
367:      PCSOR - (S)SOR (successive over relaxation, Gauss-Seidel) preconditioning

369:    Options Database Keys:
370: +  -pc_sor_symmetric - Activates symmetric version
371: .  -pc_sor_backward - Activates backward version
372: .  -pc_sor_forward - Activates forward version
373: .  -pc_sor_local_forward - Activates local forward version
374: .  -pc_sor_local_symmetric - Activates local symmetric version  (default version)
375: .  -pc_sor_local_backward - Activates local backward version
376: .  -pc_sor_omega <omega> - Sets omega
377: .  -pc_sor_diagonal_shift <shift> - shift the diagonal entries; useful if the matrix has zeros on the diagonal
378: .  -pc_sor_its <its> - Sets number of iterations   (default 1)
379: -  -pc_sor_lits <lits> - Sets number of local iterations  (default 1)

381:    Level: beginner

383:    Notes:
384:    Only implemented for the `MATAIJ`  and `MATSEQBAIJ` matrix formats.

386:    Not a true parallel SOR, in parallel this implementation corresponds to block
387:    Jacobi with SOR on each block.

389:           For `MATAIJ` matrices if a diagonal entry is zero (and the diagonal shift is zero) then by default the inverse of that
390:           zero will be used and hence the `KSPSolve()` will terminate with `KSP_DIVERGED_NANORINF`. If the option
391:           `KSPSetErrorIfNotConverged()` or -ksp_error_if_not_converged the code will terminate as soon as it detects the
392:           zero pivot.

394:           For `MATSEQBAIJ` matrices this implements point-block SOR, but the omega, its, lits options are not supported.

396:           For `MATSEQBAIJ` the diagonal blocks are inverted using dense LU with partial pivoting. If a zero pivot is detected
397:           the computation is stopped with an error

399:           If used with `KSPRICHARDSON` and no monitors the convergence test is skipped to improve speed, thus it always iterates
400:           the maximum number of iterations you've selected for `KSP`. It is usually used in this mode as a smoother for multigrid.

402:           If omega != 1, you will need to set the `MAT_USE_INODES` option to `PETSC_FALSE` on the matrix.

404: .seealso: `PCCreate()`, `PCSetType()`, `PCType`, `PC`, `PCJACOBI`,
405:           `PCSORSetIterations()`, `PCSORSetSymmetric()`, `PCSORSetOmega()`, `PCEISENSTAT`, `MatSetOption()`
406: M*/

408: PETSC_EXTERN PetscErrorCode PCCreate_SOR(PC pc)
409: {
410:   PC_SOR *jac;

412:   PetscNew(&jac);

414:   pc->ops->apply           = PCApply_SOR;
415:   pc->ops->applytranspose  = PCApplyTranspose_SOR;
416:   pc->ops->applyrichardson = PCApplyRichardson_SOR;
417:   pc->ops->setfromoptions  = PCSetFromOptions_SOR;
418:   pc->ops->setup           = NULL;
419:   pc->ops->view            = PCView_SOR;
420:   pc->ops->destroy         = PCDestroy_SOR;
421:   pc->data                 = (void *)jac;
422:   jac->sym                 = SOR_LOCAL_SYMMETRIC_SWEEP;
423:   jac->omega               = 1.0;
424:   jac->fshift              = 0.0;
425:   jac->its                 = 1;
426:   jac->lits                = 1;

428:   PetscObjectComposeFunction((PetscObject)pc, "PCSORSetSymmetric_C", PCSORSetSymmetric_SOR);
429:   PetscObjectComposeFunction((PetscObject)pc, "PCSORSetOmega_C", PCSORSetOmega_SOR);
430:   PetscObjectComposeFunction((PetscObject)pc, "PCSORSetIterations_C", PCSORSetIterations_SOR);
431:   PetscObjectComposeFunction((PetscObject)pc, "PCSORGetSymmetric_C", PCSORGetSymmetric_SOR);
432:   PetscObjectComposeFunction((PetscObject)pc, "PCSORGetOmega_C", PCSORGetOmega_SOR);
433:   PetscObjectComposeFunction((PetscObject)pc, "PCSORGetIterations_C", PCSORGetIterations_SOR);
434:   return 0;
435: }