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: PetscReal norm;
12: PetscBool flg;
13: PCFailedReason pcreason;
15: PetscFunctionBegin;
16: if (!ksp->guess_zero) {
17: PetscCall(PetscObjectTypeCompareAny((PetscObject)ksp->pc, &flg, PCREDISTRIBUTE, PCMPI, ""));
18: PetscCheck(flg, 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");
19: }
20: ksp->its = 0;
21: if (ksp->numbermonitors) {
22: PetscCall(VecNorm(ksp->vec_rhs, NORM_2, &norm));
23: PetscCall(KSPMonitor(ksp, 0, norm));
24: }
25: PetscCall(KSP_PCApply(ksp, ksp->vec_rhs, ksp->vec_sol));
26: PetscCall(PCReduceFailedReason(ksp->pc));
27: PetscCall(PCGetFailedReason(ksp->pc, &pcreason));
28: PetscCall(VecFlag(ksp->vec_sol, pcreason));
29: if (pcreason) {
30: PetscCheck(!ksp->errorifnotconverged, PetscObjectComm((PetscObject)ksp), PETSC_ERR_NOT_CONVERGED, "KSPSolve has not converged with PCFailedReason %s", PCFailedReasons[pcreason]);
31: ksp->reason = KSP_DIVERGED_PC_FAILED;
32: } else {
33: ksp->its = 1;
34: ksp->reason = KSP_CONVERGED_ITS;
35: }
36: if (ksp->numbermonitors) {
37: Vec v;
38: Mat A;
40: PetscCall(VecDuplicate(ksp->vec_rhs, &v));
41: PetscCall(PCGetOperators(ksp->pc, &A, NULL));
42: PetscCall(KSP_MatMult(ksp, A, ksp->vec_sol, v));
43: PetscCall(VecAYPX(v, -1.0, ksp->vec_rhs));
44: PetscCall(VecNorm(v, NORM_2, &norm));
45: PetscCall(VecDestroy(&v));
46: PetscCall(KSPMonitor(ksp, 1, norm));
47: }
48: PetscFunctionReturn(PETSC_SUCCESS);
49: }
51: static PetscErrorCode KSPMatSolve_PREONLY(KSP ksp, Mat B, Mat X)
52: {
53: PCFailedReason pcreason;
55: PetscFunctionBegin;
56: 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");
57: ksp->its = 0;
58: PetscCall(KSP_PCMatApply(ksp, B, X));
59: PetscCall(PCGetFailedReason(ksp->pc, &pcreason));
60: /* 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 */
61: if (pcreason) {
62: PetscCall(MatSetInf(X));
63: ksp->reason = KSP_DIVERGED_PC_FAILED;
64: } else {
65: ksp->its = 1;
66: ksp->reason = KSP_CONVERGED_ITS;
67: }
68: PetscFunctionReturn(PETSC_SUCCESS);
69: }
71: /*MC
72: KSPNONE - An alias for `KSPPREONLY`
74: Options Database Key:
75: . -ksp_type none - use a single application of the preconditioner only
77: Level: beginner
79: Note:
80: See `KSPPREONLY` for more details
82: .seealso: [](ch_ksp), `KSPCreate()`, `KSPSetType()`, `KSPType`, `KSPPREONLY`, `KSP`, `KSPRICHARDSON`, `KSPCHEBYSHEV`, `KSPGetPC()`, `KSPSetInitialGuessNonzero()`,
83: `PCREDISTRIBUTE`, `PCRedistributeGetKSP()`
84: M*/
86: /*MC
87: KSPPREONLY - This implements a method that applies ONLY the preconditioner exactly once.
89: It is commonly used with the direct solver preconditioners like `PCLU` and `PCCHOLESKY`, but it may also be used when a single iteration of the
90: preconditioner is needed for smoothing in multigrid, `PCMG` or `PCGAMG` or within some other nested linear solve such as `PCFIELDSPLIT` or `PCBJACOBI`.
92: There is an alias of this with the name `KSPNONE`.
94: Options Database Key:
95: . -ksp_type preonly - use a single application of the preconditioner only
97: Level: beginner
99: Notes:
100: Since this does not involve an iteration the basic `KSP` parameters such as tolerances and maximum iteration counts
101: do not apply
103: To apply the preconditioner multiple times in a simple iteration use `KSPRICHARDSON`
105: This `KSPType` cannot be used with the flag `-ksp_initial_guess_nonzero` or the call `KSPSetInitialGuessNonzero()` since it simply applies
106: the preconditioner to the given right-hand side during `KSPSolve()`. Except when the
107: `PCType` is `PCREDISTRIBUTE`; in that situation pass the nonzero initial guess flag with `-ksp_initial_guess_nonzero` or `KSPSetInitialGuessNonzero()`
108: both to the outer `KSP` (which is `KSPPREONLY`) and the inner `KSP` object obtained with `KSPGetPC()` followed by `PCRedistributedGetKSP()`
109: followed by `KSPSetInitialGuessNonzero()` or the option `-redistribute_ksp_initial_guess_nonzero`.
111: Developer Note:
112: Even though this method does not use any norms, the user is allowed to set the `KSPNormType` to any value.
113: This is so the users does not have to change `KSPNormType` options when they switch from other `KSP` methods to this one.
115: .seealso: [](ch_ksp), `KSPCreate()`, `KSPSetType()`, `KSPType`, `KSP`, `KSPRICHARDSON`, `KSPCHEBYSHEV`, `KSPGetPC()`, `KSPSetInitialGuessNonzero()`,
116: `PCREDISTRIBUTE`, `PCRedistributeGetKSP()`, `KSPNONE`
117: M*/
119: PETSC_EXTERN PetscErrorCode KSPCreate_PREONLY(KSP ksp)
120: {
121: PetscFunctionBegin;
122: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_NONE, PC_LEFT, 3));
123: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_NONE, PC_RIGHT, 2));
124: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_PRECONDITIONED, PC_LEFT, 2));
125: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_PRECONDITIONED, PC_RIGHT, 2));
126: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_UNPRECONDITIONED, PC_LEFT, 2));
127: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_UNPRECONDITIONED, PC_RIGHT, 2));
128: PetscCall(KSPSetSupportedNorm(ksp, KSP_NORM_NATURAL, PC_LEFT, 2));
130: ksp->data = NULL;
131: ksp->ops->setup = KSPSetUp_PREONLY;
132: ksp->ops->solve = KSPSolve_PREONLY;
133: ksp->ops->matsolve = KSPMatSolve_PREONLY;
134: ksp->ops->destroy = KSPDestroyDefault;
135: ksp->ops->buildsolution = KSPBuildSolutionDefault;
136: ksp->ops->buildresidual = KSPBuildResidualDefault;
137: ksp->ops->setfromoptions = NULL;
138: ksp->ops->view = NULL;
139: 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
140: PetscFunctionReturn(PETSC_SUCCESS);
141: }