Actual source code: sor.c

petsc-3.7.4 2016-10-02
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  2: /*
  3:    Defines a  (S)SOR  preconditioner for any Mat implementation
  4: */
  5: #include <petsc/private/pcimpl.h>               /*I "petscpc.h" I*/

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

 17: static PetscErrorCode PCDestroy_SOR(PC pc)
 18: {

 22:   PetscFree(pc->data);
 23:   return(0);
 24: }

 26: #include <petsc/private/matimpl.h>
 29: static PetscErrorCode PCApply_SOR(PC pc,Vec x,Vec y)
 30: {
 31:   PC_SOR         *jac = (PC_SOR*)pc->data;
 33:   PetscInt       flag = jac->sym | SOR_ZERO_INITIAL_GUESS;
 34:   PetscReal      fshift;
 35: 
 37:   fshift = (jac->fshift ? jac->fshift : pc->erroriffailure ? 0.0 : -1.0);
 38:   MatSOR(pc->pmat,x,jac->omega,(MatSORType)flag,fshift,jac->its,jac->lits,y);
 39:   if (pc->pmat->errortype) pc->failedreason = (PCFailedReason)pc->pmat->errortype;
 40:   return(0);
 41: }

 45: 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)
 46: {
 47:   PC_SOR         *jac = (PC_SOR*)pc->data;
 49:   MatSORType     stype = jac->sym;
 50:   PetscReal      fshift;

 53:   PetscInfo1(pc,"Warning, convergence critera ignored, using %D iterations\n",its);
 54:   if (guesszero) stype = (MatSORType) (stype | SOR_ZERO_INITIAL_GUESS);
 55:   fshift = (jac->fshift ? jac->fshift : pc->erroriffailure ? 0.0 : -1.0);
 56:   MatSOR(pc->pmat,b,jac->omega,stype,fshift,its*jac->its,jac->lits,y);
 57:   if (pc->pmat->errortype) pc->failedreason = (PCFailedReason)pc->pmat->errortype;
 58:   *outits = its;
 59:   *reason = PCRICHARDSON_CONVERGED_ITS;
 60:   return(0);
 61: }

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

 72:   PetscOptionsHead(PetscOptionsObject,"(S)SOR options");
 73:   PetscOptionsReal("-pc_sor_omega","relaxation factor (0 < omega < 2)","PCSORSetOmega",jac->omega,&jac->omega,NULL);
 74:   PetscOptionsReal("-pc_sor_diagonal_shift","Add to the diagonal entries","",jac->fshift,&jac->fshift,NULL);
 75:   PetscOptionsInt("-pc_sor_its","number of inner SOR iterations","PCSORSetIterations",jac->its,&jac->its,NULL);
 76:   PetscOptionsInt("-pc_sor_lits","number of local inner SOR iterations","PCSORSetIterations",jac->lits,&jac->lits,NULL);
 77:   PetscOptionsBoolGroupBegin("-pc_sor_symmetric","SSOR, not SOR","PCSORSetSymmetric",&flg);
 78:   if (flg) {PCSORSetSymmetric(pc,SOR_SYMMETRIC_SWEEP);}
 79:   PetscOptionsBoolGroup("-pc_sor_backward","use backward sweep instead of forward","PCSORSetSymmetric",&flg);
 80:   if (flg) {PCSORSetSymmetric(pc,SOR_BACKWARD_SWEEP);}
 81:   PetscOptionsBoolGroup("-pc_sor_forward","use forward sweep","PCSORSetSymmetric",&flg);
 82:   if (flg) {PCSORSetSymmetric(pc,SOR_FORWARD_SWEEP);}
 83:   PetscOptionsBoolGroup("-pc_sor_local_symmetric","use SSOR separately on each processor","PCSORSetSymmetric",&flg);
 84:   if (flg) {PCSORSetSymmetric(pc,SOR_LOCAL_SYMMETRIC_SWEEP);}
 85:   PetscOptionsBoolGroup("-pc_sor_local_backward","use backward sweep locally","PCSORSetSymmetric",&flg);
 86:   if (flg) {PCSORSetSymmetric(pc,SOR_LOCAL_BACKWARD_SWEEP);}
 87:   PetscOptionsBoolGroupEnd("-pc_sor_local_forward","use forward sweep locally","PCSORSetSymmetric",&flg);
 88:   if (flg) {PCSORSetSymmetric(pc,SOR_LOCAL_FORWARD_SWEEP);}
 89:   PetscOptionsTail();
 90:   return(0);
 91: }

 95: PetscErrorCode PCView_SOR(PC pc,PetscViewer viewer)
 96: {
 97:   PC_SOR         *jac = (PC_SOR*)pc->data;
 98:   MatSORType     sym  = jac->sym;
 99:   const char     *sortype;
101:   PetscBool      iascii;

104:   PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);
105:   if (iascii) {
106:     if (sym & SOR_ZERO_INITIAL_GUESS) {PetscViewerASCIIPrintf(viewer,"  SOR:  zero initial guess\n");}
107:     if (sym == SOR_APPLY_UPPER)                                              sortype = "apply_upper";
108:     else if (sym == SOR_APPLY_LOWER)                                         sortype = "apply_lower";
109:     else if (sym & SOR_EISENSTAT)                                            sortype = "Eisenstat";
110:     else if ((sym & SOR_SYMMETRIC_SWEEP) == SOR_SYMMETRIC_SWEEP)             sortype = "symmetric";
111:     else if (sym & SOR_BACKWARD_SWEEP)                                       sortype = "backward";
112:     else if (sym & SOR_FORWARD_SWEEP)                                        sortype = "forward";
113:     else if ((sym & SOR_LOCAL_SYMMETRIC_SWEEP) == SOR_LOCAL_SYMMETRIC_SWEEP) sortype = "local_symmetric";
114:     else if (sym & SOR_LOCAL_FORWARD_SWEEP)                                  sortype = "local_forward";
115:     else if (sym & SOR_LOCAL_BACKWARD_SWEEP)                                 sortype = "local_backward";
116:     else                                                                     sortype = "unknown";
117:     PetscViewerASCIIPrintf(viewer,"  SOR: type = %s, iterations = %D, local iterations = %D, omega = %g\n",sortype,jac->its,jac->lits,(double)jac->omega);
118:   }
119:   return(0);
120: }


123: /* ------------------------------------------------------------------------------*/
126: static PetscErrorCode  PCSORSetSymmetric_SOR(PC pc,MatSORType flag)
127: {
128:   PC_SOR *jac = (PC_SOR*)pc->data;

131:   jac->sym = flag;
132:   return(0);
133: }

137: static PetscErrorCode  PCSORSetOmega_SOR(PC pc,PetscReal omega)
138: {
139:   PC_SOR *jac = (PC_SOR*)pc->data;

142:   if (omega >= 2.0 || omega <= 0.0) SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_ARG_OUTOFRANGE,"Relaxation out of range");
143:   jac->omega = omega;
144:   return(0);
145: }

149: static PetscErrorCode  PCSORSetIterations_SOR(PC pc,PetscInt its,PetscInt lits)
150: {
151:   PC_SOR *jac = (PC_SOR*)pc->data;

154:   jac->its  = its;
155:   jac->lits = lits;
156:   return(0);
157: }

161: static PetscErrorCode  PCSORGetSymmetric_SOR(PC pc,MatSORType *flag)
162: {
163:   PC_SOR *jac = (PC_SOR*)pc->data;

166:   *flag = jac->sym;
167:   return(0);
168: }

172: static PetscErrorCode  PCSORGetOmega_SOR(PC pc,PetscReal *omega)
173: {
174:   PC_SOR *jac = (PC_SOR*)pc->data;

177:   *omega = jac->omega;
178:   return(0);
179: }

183: static PetscErrorCode  PCSORGetIterations_SOR(PC pc,PetscInt *its,PetscInt *lits)
184: {
185:   PC_SOR *jac = (PC_SOR*)pc->data;

188:   if (its)  *its = jac->its;
189:   if (lits) *lits = jac->lits;
190:   return(0);
191: }

193: /* ------------------------------------------------------------------------------*/
196: /*@
197:    PCSORGetSymmetric - Gets the form the SOR preconditioner is using;   backward, or forward relaxation.  The local variants perform SOR on
198:    each processor.  By default forward relaxation is used.

200:    Logically Collective on PC

202:    Input Parameter:
203: .  pc - the preconditioner context

205:    Output Parameter:
206: .  flag - one of the following
207: .vb
208:     SOR_FORWARD_SWEEP
209:     SOR_BACKWARD_SWEEP
210:     SOR_SYMMETRIC_SWEEP
211:     SOR_LOCAL_FORWARD_SWEEP
212:     SOR_LOCAL_BACKWARD_SWEEP
213:     SOR_LOCAL_SYMMETRIC_SWEEP
214: .ve

216:    Options Database Keys:
217: +  -pc_sor_symmetric - Activates symmetric version
218: .  -pc_sor_backward - Activates backward version
219: .  -pc_sor_local_forward - Activates local forward version
220: .  -pc_sor_local_symmetric - Activates local symmetric version
221: -  -pc_sor_local_backward - Activates local backward version

223:    Notes:
224:    To use the Eisenstat trick with SSOR, employ the PCEISENSTAT preconditioner,
225:    which can be chosen with the option
226: .  -pc_type eisenstat - Activates Eisenstat trick

228:    Level: intermediate

230: .keywords: PC, SOR, SSOR, set, relaxation, sweep, forward, backward, symmetric

232: .seealso: PCEisenstatSetOmega(), PCSORSetIterations(), PCSORSetOmega(), PCSORSetSymmetric()
233: @*/
234: PetscErrorCode  PCSORGetSymmetric(PC pc,MatSORType *flag)
235: {

240:   PetscUseMethod(pc,"PCSORGetSymmetric_C",(PC,MatSORType*),(pc,flag));
241:   return(0);
242: }

246: /*@
247:    PCSORGetOmega - Gets the SOR relaxation coefficient, omega
248:    (where omega = 1.0 by default).

250:    Logically Collective on PC

252:    Input Parameter:
253: .  pc - the preconditioner context

255:    Output Parameter:
256: .  omega - relaxation coefficient (0 < omega < 2).

258:    Options Database Key:
259: .  -pc_sor_omega <omega> - Sets omega

261:    Level: intermediate

263: .keywords: PC, SOR, SSOR, set, relaxation, omega

265: .seealso: PCSORSetSymmetric(), PCSORSetIterations(), PCEisenstatSetOmega(), PCSORSetOmega()
266: @*/
267: PetscErrorCode  PCSORGetOmega(PC pc,PetscReal *omega)
268: {

273:   PetscUseMethod(pc,"PCSORGetOmega_C",(PC,PetscReal*),(pc,omega));
274:   return(0);
275: }

279: /*@
280:    PCSORGetIterations - Gets the number of inner iterations to
281:    be used by the SOR preconditioner. The default is 1.

283:    Logically Collective on PC

285:    Input Parameter:
286: .  pc - the preconditioner context

288:    Output Parameter:
289: +  lits - number of local iterations, smoothings over just variables on processor
290: -  its - number of parallel iterations to use; each parallel iteration has lits local iterations

292:    Options Database Key:
293: +  -pc_sor_its <its> - Sets number of iterations
294: -  -pc_sor_lits <lits> - Sets number of local iterations

296:    Level: intermediate

298:    Notes: When run on one processor the number of smoothings is lits*its

300: .keywords: PC, SOR, SSOR, set, iterations

302: .seealso: PCSORSetOmega(), PCSORSetSymmetric(), PCSORSetIterations()
303: @*/
304: PetscErrorCode  PCSORGetIterations(PC pc,PetscInt *its,PetscInt *lits)
305: {

310:   PetscUseMethod(pc,"PCSORGetIterations_C",(PC,PetscInt*,PetscInt*),(pc,its,lits));
311:   return(0);
312: }

316: /*@
317:    PCSORSetSymmetric - Sets the SOR preconditioner to use symmetric (SSOR),
318:    backward, or forward relaxation.  The local variants perform SOR on
319:    each processor.  By default forward relaxation is used.

321:    Logically Collective on PC

323:    Input Parameters:
324: +  pc - the preconditioner context
325: -  flag - one of the following
326: .vb
327:     SOR_FORWARD_SWEEP
328:     SOR_BACKWARD_SWEEP
329:     SOR_SYMMETRIC_SWEEP
330:     SOR_LOCAL_FORWARD_SWEEP
331:     SOR_LOCAL_BACKWARD_SWEEP
332:     SOR_LOCAL_SYMMETRIC_SWEEP
333: .ve

335:    Options Database Keys:
336: +  -pc_sor_symmetric - Activates symmetric version
337: .  -pc_sor_backward - Activates backward version
338: .  -pc_sor_local_forward - Activates local forward version
339: .  -pc_sor_local_symmetric - Activates local symmetric version
340: -  -pc_sor_local_backward - Activates local backward version

342:    Notes:
343:    To use the Eisenstat trick with SSOR, employ the PCEISENSTAT preconditioner,
344:    which can be chosen with the option
345: .  -pc_type eisenstat - Activates Eisenstat trick

347:    Level: intermediate

349: .keywords: PC, SOR, SSOR, set, relaxation, sweep, forward, backward, symmetric

351: .seealso: PCEisenstatSetOmega(), PCSORSetIterations(), PCSORSetOmega()
352: @*/
353: PetscErrorCode  PCSORSetSymmetric(PC pc,MatSORType flag)
354: {

360:   PetscTryMethod(pc,"PCSORSetSymmetric_C",(PC,MatSORType),(pc,flag));
361:   return(0);
362: }

366: /*@
367:    PCSORSetOmega - Sets the SOR relaxation coefficient, omega
368:    (where omega = 1.0 by default).

370:    Logically Collective on PC

372:    Input Parameters:
373: +  pc - the preconditioner context
374: -  omega - relaxation coefficient (0 < omega < 2).

376:    Options Database Key:
377: .  -pc_sor_omega <omega> - Sets omega

379:    Level: intermediate

381: .keywords: PC, SOR, SSOR, set, relaxation, omega

383: .seealso: PCSORSetSymmetric(), PCSORSetIterations(), PCEisenstatSetOmega()
384: @*/
385: PetscErrorCode  PCSORSetOmega(PC pc,PetscReal omega)
386: {

392:   PetscTryMethod(pc,"PCSORSetOmega_C",(PC,PetscReal),(pc,omega));
393:   return(0);
394: }

398: /*@
399:    PCSORSetIterations - Sets the number of inner iterations to
400:    be used by the SOR preconditioner. The default is 1.

402:    Logically Collective on PC

404:    Input Parameters:
405: +  pc - the preconditioner context
406: .  lits - number of local iterations, smoothings over just variables on processor
407: -  its - number of parallel iterations to use; each parallel iteration has lits local iterations

409:    Options Database Key:
410: +  -pc_sor_its <its> - Sets number of iterations
411: -  -pc_sor_lits <lits> - Sets number of local iterations

413:    Level: intermediate

415:    Notes: When run on one processor the number of smoothings is lits*its

417: .keywords: PC, SOR, SSOR, set, iterations

419: .seealso: PCSORSetOmega(), PCSORSetSymmetric()
420: @*/
421: PetscErrorCode  PCSORSetIterations(PC pc,PetscInt its,PetscInt lits)
422: {

428:   PetscTryMethod(pc,"PCSORSetIterations_C",(PC,PetscInt,PetscInt),(pc,its,lits));
429:   return(0);
430: }

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

435:    Options Database Keys:
436: +  -pc_sor_symmetric - Activates symmetric version
437: .  -pc_sor_backward - Activates backward version
438: .  -pc_sor_forward - Activates forward version
439: .  -pc_sor_local_forward - Activates local forward version
440: .  -pc_sor_local_symmetric - Activates local symmetric version  (default version)
441: .  -pc_sor_local_backward - Activates local backward version
442: .  -pc_sor_omega <omega> - Sets omega
443: .  -pc_sor_diagonal_shift <shift> - shift the diagonal entries; useful if the matrix has zeros on the diagonal
444: .  -pc_sor_its <its> - Sets number of iterations   (default 1)
445: -  -pc_sor_lits <lits> - Sets number of local iterations  (default 1)

447:    Level: beginner

449:   Concepts: SOR, preconditioners, Gauss-Seidel

451:    Notes: Only implemented for the AIJ  and SeqBAIJ matrix formats.
452:           Not a true parallel SOR, in parallel this implementation corresponds to block
453:           Jacobi with SOR on each block.

455:           For AIJ matrix if a diagonal entry is zero (and the diagonal shift is zero) then by default the inverse of that
456:           zero will be used and hence the KSPSolve() will terminate with KSP_DIVERGED_NANORIF. If the option
457:           KSPSetErrorIfNotConverged() or -ksp_error_if_not_converged the code will terminate as soon as it detects the 
458:           zero pivot.

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

462:           For SeqBAIJ the diagonal blocks are inverted using dense LU with partial pivoting. If a zero pivot is detected 
463:           the computation is stopped with an error

465: .seealso:  PCCreate(), PCSetType(), PCType (for list of available types), PC,
466:            PCSORSetIterations(), PCSORSetSymmetric(), PCSORSetOmega(), PCEISENSTAT
467: M*/

471: PETSC_EXTERN PetscErrorCode PCCreate_SOR(PC pc)
472: {
474:   PC_SOR         *jac;

477:   PetscNewLog(pc,&jac);

479:   pc->ops->apply           = PCApply_SOR;
480:   pc->ops->applyrichardson = PCApplyRichardson_SOR;
481:   pc->ops->setfromoptions  = PCSetFromOptions_SOR;
482:   pc->ops->setup           = 0;
483:   pc->ops->view            = PCView_SOR;
484:   pc->ops->destroy         = PCDestroy_SOR;
485:   pc->data                 = (void*)jac;
486:   jac->sym                 = SOR_LOCAL_SYMMETRIC_SWEEP;
487:   jac->omega               = 1.0;
488:   jac->fshift              = 0.0;
489:   jac->its                 = 1;
490:   jac->lits                = 1;

492:   PetscObjectComposeFunction((PetscObject)pc,"PCSORSetSymmetric_C",PCSORSetSymmetric_SOR);
493:   PetscObjectComposeFunction((PetscObject)pc,"PCSORSetOmega_C",PCSORSetOmega_SOR);
494:   PetscObjectComposeFunction((PetscObject)pc,"PCSORSetIterations_C",PCSORSetIterations_SOR);
495:   PetscObjectComposeFunction((PetscObject)pc,"PCSORGetSymmetric_C",PCSORGetSymmetric_SOR);
496:   PetscObjectComposeFunction((PetscObject)pc,"PCSORGetOmega_C",PCSORGetOmega_SOR);
497:   PetscObjectComposeFunction((PetscObject)pc,"PCSORGetIterations_C",PCSORGetIterations_SOR);
498:   return(0);
499: }