Actual source code: ilu.c

petsc-main 2021-04-20
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  2: /*
  3:    Defines a ILU factorization preconditioner for any Mat implementation
  4: */
  5: #include <../src/ksp/pc/impls/factor/ilu/ilu.h>

  7: PetscErrorCode  PCFactorReorderForNonzeroDiagonal_ILU(PC pc,PetscReal z)
  8: {
  9:   PC_ILU *ilu = (PC_ILU*)pc->data;

 12:   ilu->nonzerosalongdiagonal = PETSC_TRUE;
 13:   if (z == PETSC_DECIDE) ilu->nonzerosalongdiagonaltol = 1.e-10;
 14:   else ilu->nonzerosalongdiagonaltol = z;
 15:   return(0);
 16: }

 18: PetscErrorCode PCReset_ILU(PC pc)
 19: {
 20:   PC_ILU         *ilu = (PC_ILU*)pc->data;

 24:   if (!ilu->hdr.inplace) {MatDestroy(&((PC_Factor*)ilu)->fact);}
 25:   if (ilu->row && ilu->col && ilu->row != ilu->col) {ISDestroy(&ilu->row);}
 26:   ISDestroy(&ilu->col);
 27:   return(0);
 28: }

 30: PetscErrorCode  PCFactorSetDropTolerance_ILU(PC pc,PetscReal dt,PetscReal dtcol,PetscInt dtcount)
 31: {
 32:   PC_ILU *ilu = (PC_ILU*)pc->data;

 35:   if (pc->setupcalled && (((PC_Factor*)ilu)->info.dt != dt || ((PC_Factor*)ilu)->info.dtcol != dtcol || ((PC_Factor*)ilu)->info.dtcount != dtcount)) {
 36:     SETERRQ(PetscObjectComm((PetscObject)pc),PETSC_ERR_SUP,"Cannot change drop tolerance after using PC");
 37:   }
 38:   ((PC_Factor*)ilu)->info.dt      = dt;
 39:   ((PC_Factor*)ilu)->info.dtcol   = dtcol;
 40:   ((PC_Factor*)ilu)->info.dtcount = dtcount;
 41:   ((PC_Factor*)ilu)->info.usedt   = 1.0;
 42:   return(0);
 43: }

 45: static PetscErrorCode PCSetFromOptions_ILU(PetscOptionItems *PetscOptionsObject,PC pc)
 46: {
 48:   PetscInt       itmp;
 49:   PetscBool      flg,set;
 50:   PC_ILU         *ilu = (PC_ILU*)pc->data;
 51:   PetscReal      tol;

 54:   PetscOptionsHead(PetscOptionsObject,"ILU Options");
 55:   PCSetFromOptions_Factor(PetscOptionsObject,pc);

 57:   PetscOptionsInt("-pc_factor_levels","levels of fill","PCFactorSetLevels",(PetscInt)((PC_Factor*)ilu)->info.levels,&itmp,&flg);
 58:   if (flg) ((PC_Factor*)ilu)->info.levels = itmp;

 60:   PetscOptionsBool("-pc_factor_diagonal_fill","Allow fill into empty diagonal entry","PCFactorSetAllowDiagonalFill",((PC_Factor*)ilu)->info.diagonal_fill ? PETSC_TRUE : PETSC_FALSE,&flg,&set);
 61:   if (set) ((PC_Factor*)ilu)->info.diagonal_fill = (PetscReal) flg;
 62:   PetscOptionsName("-pc_factor_nonzeros_along_diagonal","Reorder to remove zeros from diagonal","PCFactorReorderForNonzeroDiagonal",&flg);
 63:   if (flg) {
 64:     tol  = PETSC_DECIDE;
 65:     PetscOptionsReal("-pc_factor_nonzeros_along_diagonal","Reorder to remove zeros from diagonal","PCFactorReorderForNonzeroDiagonal",ilu->nonzerosalongdiagonaltol,&tol,NULL);
 66:     PCFactorReorderForNonzeroDiagonal(pc,tol);
 67:   }

 69:   PetscOptionsTail();
 70:   return(0);
 71: }

 73: static PetscErrorCode PCSetUp_ILU(PC pc)
 74: {
 75:   PetscErrorCode         ierr;
 76:   PC_ILU                 *ilu = (PC_ILU*)pc->data;
 77:   MatInfo                info;
 78:   PetscBool              flg;
 79:   MatSolverType          stype;
 80:   MatFactorError         err;

 83:   pc->failedreason = PC_NOERROR;
 84:   /* ugly hack to change default, since it is not support by some matrix types */
 85:   if (((PC_Factor*)ilu)->info.shifttype == (PetscReal)MAT_SHIFT_NONZERO) {
 86:     PetscObjectTypeCompare((PetscObject)pc->pmat,MATSEQAIJ,&flg);
 87:     if (!flg) {
 88:       PetscObjectTypeCompare((PetscObject)pc->pmat,MATMPIAIJ,&flg);
 89:       if (!flg) {
 90:         ((PC_Factor*)ilu)->info.shifttype = (PetscReal)MAT_SHIFT_INBLOCKS;
 91:         PetscInfo(pc,"Changing shift type from NONZERO to INBLOCKS because block matrices do not support NONZERO\n");
 92:       }
 93:     }
 94:   }

 96:   MatSetErrorIfFailure(pc->pmat,pc->erroriffailure);
 97:   if (ilu->hdr.inplace) {
 98:     if (!pc->setupcalled) {

100:       /* In-place factorization only makes sense with the natural ordering,
101:          so we only need to get the ordering once, even if nonzero structure changes */
102:       /* Should not get the ordering if the factorization routine does not use it, but do not yet have access to the factor matrix */
103:       PCFactorSetDefaultOrdering_Factor(pc);
104:       MatDestroy(&((PC_Factor*)ilu)->fact);
105:       MatGetOrdering(pc->pmat,((PC_Factor*)ilu)->ordering,&ilu->row,&ilu->col);
106:       if (ilu->row) {PetscLogObjectParent((PetscObject)pc,(PetscObject)ilu->row);}
107:       if (ilu->col) {PetscLogObjectParent((PetscObject)pc,(PetscObject)ilu->col);}
108:     }

110:     /* In place ILU only makes sense with fill factor of 1.0 because
111:        cannot have levels of fill */
112:     ((PC_Factor*)ilu)->info.fill          = 1.0;
113:     ((PC_Factor*)ilu)->info.diagonal_fill = 0.0;

115:     MatILUFactor(pc->pmat,ilu->row,ilu->col,&((PC_Factor*)ilu)->info);
116:     MatFactorGetError(pc->pmat,&err);
117:     if (err) { /* Factor() fails */
118:       pc->failedreason = (PCFailedReason)err;
119:       return(0);
120:     }

122:     ((PC_Factor*)ilu)->fact = pc->pmat;
123:     /* must update the pc record of the matrix state or the PC will attempt to run PCSetUp() yet again */
124:     PetscObjectStateGet((PetscObject)pc->pmat,&pc->matstate);
125:   } else {
126:     if (!pc->setupcalled) {
127:       /* first time in so compute reordering and symbolic factorization */
128:       PetscBool canuseordering;
129:       if (!((PC_Factor*)ilu)->fact) {
130:         MatGetFactor(pc->pmat,((PC_Factor*)ilu)->solvertype,MAT_FACTOR_ILU,&((PC_Factor*)ilu)->fact);
131:         PetscLogObjectParent((PetscObject)pc,(PetscObject)((PC_Factor*)ilu)->fact);
132:       }
133:       MatFactorGetCanUseOrdering(((PC_Factor*)ilu)->fact,&canuseordering);
134:       if (canuseordering) {
135:         PCFactorSetDefaultOrdering_Factor(pc);
136:         MatGetOrdering(pc->pmat,((PC_Factor*)ilu)->ordering,&ilu->row,&ilu->col);
137:         PetscLogObjectParent((PetscObject)pc,(PetscObject)ilu->row);
138:         PetscLogObjectParent((PetscObject)pc,(PetscObject)ilu->col);
139:         /*  Remove zeros along diagonal?     */
140:         if (ilu->nonzerosalongdiagonal) {
141:           MatReorderForNonzeroDiagonal(pc->pmat,ilu->nonzerosalongdiagonaltol,ilu->row,ilu->col);
142:         }
143:       }
144:       MatILUFactorSymbolic(((PC_Factor*)ilu)->fact,pc->pmat,ilu->row,ilu->col,&((PC_Factor*)ilu)->info);
145:       MatGetInfo(((PC_Factor*)ilu)->fact,MAT_LOCAL,&info);
146:       ilu->hdr.actualfill = info.fill_ratio_needed;
147:     } else if (pc->flag != SAME_NONZERO_PATTERN) {
148:       if (!ilu->hdr.reuseordering) {
149:         PetscBool canuseordering;
150:         MatDestroy(&((PC_Factor*)ilu)->fact);
151:         MatGetFactor(pc->pmat,((PC_Factor*)ilu)->solvertype,MAT_FACTOR_ILU,&((PC_Factor*)ilu)->fact);
152:         PetscLogObjectParent((PetscObject)pc,(PetscObject)((PC_Factor*)ilu)->fact);
153:         MatFactorGetCanUseOrdering(((PC_Factor*)ilu)->fact,&canuseordering);
154:         if (canuseordering) {
155:           /* compute a new ordering for the ILU */
156:           ISDestroy(&ilu->row);
157:           ISDestroy(&ilu->col);
158:           PCFactorSetDefaultOrdering_Factor(pc);
159:           MatGetOrdering(pc->pmat,((PC_Factor*)ilu)->ordering,&ilu->row,&ilu->col);
160:           PetscLogObjectParent((PetscObject)pc,(PetscObject)ilu->row);
161:           PetscLogObjectParent((PetscObject)pc,(PetscObject)ilu->col);
162:           /*  Remove zeros along diagonal?     */
163:           if (ilu->nonzerosalongdiagonal) {
164:             MatReorderForNonzeroDiagonal(pc->pmat,ilu->nonzerosalongdiagonaltol,ilu->row,ilu->col);
165:           }
166:         }
167:       }
168:       MatILUFactorSymbolic(((PC_Factor*)ilu)->fact,pc->pmat,ilu->row,ilu->col,&((PC_Factor*)ilu)->info);
169:       MatGetInfo(((PC_Factor*)ilu)->fact,MAT_LOCAL,&info);
170:       ilu->hdr.actualfill = info.fill_ratio_needed;
171:     }
172:     MatFactorGetError(((PC_Factor*)ilu)->fact,&err);
173:     if (err) { /* FactorSymbolic() fails */
174:       pc->failedreason = (PCFailedReason)err;
175:       return(0);
176:     }

178:     MatLUFactorNumeric(((PC_Factor*)ilu)->fact,pc->pmat,&((PC_Factor*)ilu)->info);
179:     MatFactorGetError(((PC_Factor*)ilu)->fact,&err);
180:     if (err) { /* FactorNumeric() fails */
181:       pc->failedreason = (PCFailedReason)err;
182:     }
183:   }

185:   PCFactorGetMatSolverType(pc,&stype);
186:   if (!stype) {
187:     MatSolverType solverpackage;
188:     MatFactorGetSolverType(((PC_Factor*)ilu)->fact,&solverpackage);
189:     PCFactorSetMatSolverType(pc,solverpackage);
190:   }
191:   return(0);
192: }

194: static PetscErrorCode PCDestroy_ILU(PC pc)
195: {
196:   PC_ILU         *ilu = (PC_ILU*)pc->data;

200:   PCReset_ILU(pc);
201:   PetscFree(((PC_Factor*)ilu)->solvertype);
202:   PetscFree(((PC_Factor*)ilu)->ordering);
203:   PetscFree(pc->data);
204:   return(0);
205: }

207: static PetscErrorCode PCApply_ILU(PC pc,Vec x,Vec y)
208: {
209:   PC_ILU         *ilu = (PC_ILU*)pc->data;

213:   MatSolve(((PC_Factor*)ilu)->fact,x,y);
214:   return(0);
215: }

217: static PetscErrorCode PCMatApply_ILU(PC pc,Mat X,Mat Y)
218: {
219:   PC_ILU         *ilu = (PC_ILU*)pc->data;

223:   MatMatSolve(((PC_Factor*)ilu)->fact,X,Y);
224:   return(0);
225: }

227: static PetscErrorCode PCApplyTranspose_ILU(PC pc,Vec x,Vec y)
228: {
229:   PC_ILU         *ilu = (PC_ILU*)pc->data;

233:   MatSolveTranspose(((PC_Factor*)ilu)->fact,x,y);
234:   return(0);
235: }

237: static PetscErrorCode PCApplySymmetricLeft_ILU(PC pc,Vec x,Vec y)
238: {
240:   PC_ILU         *icc = (PC_ILU*)pc->data;

243:   MatForwardSolve(((PC_Factor*)icc)->fact,x,y);
244:   return(0);
245: }

247: static PetscErrorCode PCApplySymmetricRight_ILU(PC pc,Vec x,Vec y)
248: {
250:   PC_ILU         *icc = (PC_ILU*)pc->data;

253:   MatBackwardSolve(((PC_Factor*)icc)->fact,x,y);
254:   return(0);
255: }

257: /*MC
258:      PCILU - Incomplete factorization preconditioners.

260:    Options Database Keys:
261: +  -pc_factor_levels <k> - number of levels of fill for ILU(k)
262: .  -pc_factor_in_place - only for ILU(0) with natural ordering, reuses the space of the matrix for
263:                       its factorization (overwrites original matrix)
264: .  -pc_factor_diagonal_fill - fill in a zero diagonal even if levels of fill indicate it wouldn't be fill
265: .  -pc_factor_reuse_ordering - reuse ordering of factorized matrix from previous factorization
266: .  -pc_factor_fill <nfill> - expected amount of fill in factored matrix compared to original matrix, nfill > 1
267: .  -pc_factor_nonzeros_along_diagonal - reorder the matrix before factorization to remove zeros from the diagonal,
268:                                    this decreases the chance of getting a zero pivot
269: .  -pc_factor_mat_ordering_type <natural,nd,1wd,rcm,qmd> - set the row/column ordering of the factored matrix
270: -  -pc_factor_pivot_in_blocks - for block ILU(k) factorization, i.e. with BAIJ matrices with block size larger
271:                              than 1 the diagonal blocks are factored with partial pivoting (this increases the
272:                              stability of the ILU factorization

274:    Level: beginner

276:    Notes:
277:     Only implemented for some matrix formats. (for parallel see PCHYPRE for hypre's ILU)

279:           For BAIJ matrices this implements a point block ILU

281:           The "symmetric" application of this preconditioner is not actually symmetric since L is not transpose(U)
282:           even when the matrix is not symmetric since the U stores the diagonals of the factorization.

284:           If you are using MATSEQAIJCUSPARSE matrices (or MATMPIAIJCUSPARSE matrices with block Jacobi), factorization
285:           is never done on the GPU).

287:    References:
288: +  1. - T. Dupont, R. Kendall, and H. Rachford. An approximate factorization procedure for solving
289:    self adjoint elliptic difference equations. SIAM J. Numer. Anal., 5, 1968.
290: .  2. -  T.A. Oliphant. An implicit numerical method for solving two dimensional timedependent diffusion problems. Quart. Appl. Math., 19, 1961.
291: -  3. -  TONY F. CHAN AND HENK A. VAN DER VORST, APPROXIMATE AND INCOMPLETE FACTORIZATIONS,
292:       Chapter in Parallel Numerical
293:       Algorithms, edited by D. Keyes, A. Semah, V. Venkatakrishnan, ICASE/LaRC Interdisciplinary Series in
294:       Science and Engineering, Kluwer.


297: .seealso:  PCCreate(), PCSetType(), PCType (for list of available types), PC, PCSOR, MatOrderingType,
298:            PCFactorSetZeroPivot(), PCFactorSetShiftSetType(), PCFactorSetAmount(),
299:            PCFactorSetDropTolerance(),PCFactorSetFill(), PCFactorSetMatOrderingType(), PCFactorSetReuseOrdering(),
300:            PCFactorSetLevels(), PCFactorSetUseInPlace(), PCFactorSetAllowDiagonalFill(), PCFactorSetPivotInBlocks(),
301:            PCFactorGetAllowDiagonalFill(), PCFactorGetUseInPlace()

303: M*/

305: PETSC_EXTERN PetscErrorCode PCCreate_ILU(PC pc)
306: {
308:   PC_ILU         *ilu;

311:   PetscNewLog(pc,&ilu);
312:   pc->data = (void*)ilu;
313:   PCFactorInitialize(pc,MAT_FACTOR_ILU);

315:   ((PC_Factor*)ilu)->info.levels        = 0.;
316:   ((PC_Factor*)ilu)->info.fill          = 1.0;
317:   ilu->col                              = NULL;
318:   ilu->row                              = NULL;
319:   ((PC_Factor*)ilu)->info.dt            = PETSC_DEFAULT;
320:   ((PC_Factor*)ilu)->info.dtcount       = PETSC_DEFAULT;
321:   ((PC_Factor*)ilu)->info.dtcol         = PETSC_DEFAULT;

323:   pc->ops->reset               = PCReset_ILU;
324:   pc->ops->destroy             = PCDestroy_ILU;
325:   pc->ops->apply               = PCApply_ILU;
326:   pc->ops->matapply            = PCMatApply_ILU;
327:   pc->ops->applytranspose      = PCApplyTranspose_ILU;
328:   pc->ops->setup               = PCSetUp_ILU;
329:   pc->ops->setfromoptions      = PCSetFromOptions_ILU;
330:   pc->ops->view                = PCView_Factor;
331:   pc->ops->applysymmetricleft  = PCApplySymmetricLeft_ILU;
332:   pc->ops->applysymmetricright = PCApplySymmetricRight_ILU;
333:   pc->ops->applyrichardson     = NULL;
334:   PetscObjectComposeFunction((PetscObject)pc,"PCFactorSetDropTolerance_C",PCFactorSetDropTolerance_ILU);
335:   PetscObjectComposeFunction((PetscObject)pc,"PCFactorReorderForNonzeroDiagonal_C",PCFactorReorderForNonzeroDiagonal_ILU);
336:   return(0);
337: }