Actual source code: preonly.c
1: #include <petsc/private/kspimpl.h>
3: static PetscErrorCode KSPSetUp_PREONLY(KSP ksp)
4: {
5: PetscFunctionBegin;
6: PetscFunctionReturn(PETSC_SUCCESS);
7: }
9: static PetscErrorCode KSPSolve_PREONLY(KSP ksp)
10: {
11: PetscBool diagonalscale;
12: PCFailedReason pcreason;
14: PetscFunctionBegin;
15: PetscCall(PCGetDiagonalScale(ksp->pc, &diagonalscale));
16: PetscCheck(!diagonalscale, PetscObjectComm((PetscObject)ksp), PETSC_ERR_SUP, "Krylov method %s does not support diagonal scaling", ((PetscObject)ksp)->type_name);
17: if (!ksp->guess_zero) {
18: PetscBool red;
19: PetscCall(PetscObjectTypeCompare((PetscObject)ksp->pc, PCREDISTRIBUTE, &red));
20: PetscCheck(red, PetscObjectComm((PetscObject)ksp), PETSC_ERR_USER, "KSP of type preonly (application of preconditioner only) doesn't make sense with nonzero initial guess you probably want a KSP of type Richardson");
21: }
22: ksp->its = 0;
23: PetscCall(KSP_PCApply(ksp, ksp->vec_rhs, ksp->vec_sol));
25: PetscCall(PCReduceFailedReason(ksp->pc));
26: PetscCall(PCGetFailedReason(ksp->pc, &pcreason));
27: if (pcreason) {
28: PetscCheck(!ksp->errorifnotconverged, PetscObjectComm((PetscObject)ksp), PETSC_ERR_NOT_CONVERGED, "KSPSolve has not converged with PCFailedReason %s", PCFailedReasons[pcreason]);
29: PetscCall(VecSetInf(ksp->vec_sol));
30: ksp->reason = KSP_DIVERGED_PC_FAILED;
31: } else {
32: ksp->its = 1;
33: ksp->reason = KSP_CONVERGED_ITS;
34: }
36: if (ksp->numbermonitors) {
37: Vec v;
38: PetscReal norm;
39: Mat A;
41: PetscCall(VecNorm(ksp->vec_rhs, NORM_2, &norm));
42: PetscCall(KSPMonitor(ksp, 0, norm));
43: PetscCall(VecDuplicate(ksp->vec_rhs, &v));
44: PetscCall(PCGetOperators(ksp->pc, &A, NULL));
45: PetscCall(KSP_MatMult(ksp, A, ksp->vec_sol, v));
46: PetscCall(VecAYPX(v, -1.0, ksp->vec_rhs));
47: PetscCall(VecNorm(v, NORM_2, &norm));
48: PetscCall(VecDestroy(&v));
49: PetscCall(KSPMonitor(ksp, 1, norm));
50: }
51: PetscFunctionReturn(PETSC_SUCCESS);
52: }
54: static PetscErrorCode KSPMatSolve_PREONLY(KSP ksp, Mat B, Mat X)
55: {
56: PetscBool diagonalscale;
57: PCFailedReason pcreason;
59: PetscFunctionBegin;
60: PetscCall(PCGetDiagonalScale(ksp->pc, &diagonalscale));
61: PetscCheck(!diagonalscale, PetscObjectComm((PetscObject)ksp), PETSC_ERR_SUP, "Krylov method %s does not support diagonal scaling", ((PetscObject)ksp)->type_name);
62: PetscCheck(ksp->guess_zero, PetscObjectComm((PetscObject)ksp), PETSC_ERR_USER, "Running KSP of preonly doesn't make sense with nonzero initial guess you probably want a KSP type of Richardson");
63: ksp->its = 0;
64: PetscCall(KSP_PCMatApply(ksp, B, X));
65: PetscCall(PCGetFailedReason(ksp->pc, &pcreason));
66: /* Note: only some ranks may have this set; this may lead to problems if the caller assumes ksp->reason is set on all processes or just uses the result */
67: if (pcreason) {
68: PetscCall(MatSetInf(X));
69: ksp->reason = KSP_DIVERGED_PC_FAILED;
70: } else {
71: ksp->its = 1;
72: ksp->reason = KSP_CONVERGED_ITS;
73: }
74: PetscFunctionReturn(PETSC_SUCCESS);
75: }
77: /*MC
78: KSPNONE - An alias for `KSPPREONLY`
80: Options Database Key:
81: . -ksp_type none - use a single application of the preconditioner only
83: Level: beginner
85: Note:
86: See `KSPPREONLY` for more details
88: .seealso: [](ch_ksp), `KSPCreate()`, `KSPSetType()`, `KSPType`, `KSPPREONLY`, `KSP`, `KSPRICHARDSON`, `KSPCHEBYSHEV`, `KSPGetPC()`, `KSPSetInitialGuessNonzero()`,
89: `PCREDISTRIBUTE`, `PCRedistributeGetKSP()`, `KSPPREONLY`
90: M*/
92: /*MC
93: KSPPREONLY - This implements a method that applies ONLY the preconditioner exactly once.
95: This may be used in inner iterations, where it is desired to
96: allow multiple iterations as well as the "0-iteration" case. It is
97: commonly used with the direct solver preconditioners like `PCLU` and `PCCHOLESKY`.
98: There is an alias of this with the name `KSPNONE`.
100: Options Database Key:
101: . -ksp_type preonly - use a single application of the preconditioner only
103: Level: beginner
105: Notes:
106: Since this does not involve an iteration the basic `KSP` parameters such as tolerances and iteration counts
107: do not apply
109: To apply multiple preconditioners in a simple iteration use `KSPRICHARDSON`
111: This `KSPType` cannot be used with the flag `-ksp_initial_guess_nonzero` or the call `KSPSetInitialGuessNonzero()` since it simply applies
112: the preconditioner to the given right-hand side during `KSPSolve()`. Except when the
113: `PCType` is `PCREDISTRIBUTE`; in that situation pass the nonzero initial guess flag with `-ksp_initial_guess_nonzero` or `KSPSetInitialGuessNonzero()`
114: both to the outer `KSP` (which is `KSPPREONLY`) and the inner `KSP` object obtained with `KSPGetPC()` followed by `PCRedistributedGetKSP()`
115: followed by `KSPSetInitialGuessNonzero()` or the option `-redistribute_ksp_initial_guess_nonzero`.
117: Developer Note:
118: Even though this method does not use any norms, the user is allowed to set the `KSPNormType` to any value.
119: This is so the users does not have to change `KSPNormType` options when they switch from other `KSP` methods to this one.
121: .seealso: [](ch_ksp), `KSPCreate()`, `KSPSetType()`, `KSPType`, `KSP`, `KSPRICHARDSON`, `KSPCHEBYSHEV`, `KSPGetPC()`, `KSPSetInitialGuessNonzero()`,
122: `PCREDISTRIBUTE`, `PCRedistributeGetKSP()`, `KSPNONE`
123: M*/
125: PETSC_EXTERN PetscErrorCode KSPCreate_PREONLY(KSP ksp)
126: {
127: PetscFunctionBegin;
128: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_NONE, PC_LEFT, 3));
129: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_NONE, PC_RIGHT, 2));
130: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_PRECONDITIONED, PC_LEFT, 2));
131: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_PRECONDITIONED, PC_RIGHT, 2));
132: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_UNPRECONDITIONED, PC_LEFT, 2));
133: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_UNPRECONDITIONED, PC_RIGHT, 2));
134: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_NATURAL, PC_LEFT, 2));
136: ksp->data = NULL;
137: ksp->ops->setup = KSPSetUp_PREONLY;
138: ksp->ops->solve = KSPSolve_PREONLY;
139: ksp->ops->matsolve = KSPMatSolve_PREONLY;
140: ksp->ops->destroy = KSPDestroyDefault;
141: ksp->ops->buildsolution = KSPBuildSolutionDefault;
142: ksp->ops->buildresidual = KSPBuildResidualDefault;
143: ksp->ops->setfromoptions = NULL;
144: ksp->ops->view = NULL;
145: ksp->guess_not_read = PETSC_TRUE; // A KSP of preonly never needs to zero the input x since PC do not use an initial guess
146: PetscFunctionReturn(PETSC_SUCCESS);
147: }