Actual source code: snesgs.c
1: #include <../src/snes/impls/gs/gsimpl.h>
3: /*@
4: SNESNGSSetTolerances - Sets various parameters used in convergence tests for nonlinear Gauss-Seidel `SNESNCG`
6: Logically Collective
8: Input Parameters:
9: + snes - the `SNES` context
10: . abstol - absolute convergence tolerance
11: . rtol - relative convergence tolerance
12: . stol - convergence tolerance in terms of the norm of the change in the solution between steps, || delta x || < stol*|| x ||
13: - maxit - maximum number of iterations
15: Options Database Keys:
16: + -snes_ngs_atol <abstol> - Sets abstol
17: . -snes_ngs_rtol <rtol> - Sets rtol
18: . -snes_ngs_stol <stol> - Sets stol
19: - -snes_max_it <maxit> - Sets maxit
21: Level: intermediate
23: .seealso: [](ch_snes), `SNES`, `SNESNCG`, `SNESSetTrustRegionTolerance()`
24: @*/
25: PetscErrorCode SNESNGSSetTolerances(SNES snes, PetscReal abstol, PetscReal rtol, PetscReal stol, PetscInt maxit)
26: {
27: SNES_NGS *gs = (SNES_NGS *)snes->data;
29: PetscFunctionBegin;
32: if (abstol != (PetscReal)PETSC_DEFAULT) {
33: PetscCheck(abstol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Absolute tolerance %g must be non-negative", (double)abstol);
34: gs->abstol = abstol;
35: }
36: if (rtol != (PetscReal)PETSC_DEFAULT) {
37: PetscCheck(rtol >= 0.0 && rtol < 1.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Relative tolerance %g must be non-negative and less than 1.0", (double)rtol);
38: gs->rtol = rtol;
39: }
40: if (stol != (PetscReal)PETSC_DEFAULT) {
41: PetscCheck(stol >= 0.0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Step tolerance %g must be non-negative", (double)stol);
42: gs->stol = stol;
43: }
44: if (maxit != PETSC_DEFAULT) {
45: PetscCheck(maxit >= 0, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_OUTOFRANGE, "Maximum number of iterations %" PetscInt_FMT " must be non-negative", maxit);
46: gs->max_its = maxit;
47: }
48: PetscFunctionReturn(PETSC_SUCCESS);
49: }
51: /*@
52: SNESNGSGetTolerances - Gets various parameters used in convergence tests for nonlinear Gauss-Seidel `SNESNCG`
54: Not Collective
56: Input Parameters:
57: + snes - the `SNES` context
58: . atol - absolute convergence tolerance
59: . rtol - relative convergence tolerance
60: . stol - convergence tolerance in terms of the norm
61: of the change in the solution between steps
62: - maxit - maximum number of iterations
64: Level: intermediate
66: Note:
67: The user can specify `NULL` for any parameter that is not needed.
69: .seealso: [](ch_snes), `SNES`, `SNESNCG`, `SNESSetTolerances()`
70: @*/
71: PetscErrorCode SNESNGSGetTolerances(SNES snes, PetscReal *atol, PetscReal *rtol, PetscReal *stol, PetscInt *maxit)
72: {
73: SNES_NGS *gs = (SNES_NGS *)snes->data;
75: PetscFunctionBegin;
77: if (atol) *atol = gs->abstol;
78: if (rtol) *rtol = gs->rtol;
79: if (stol) *stol = gs->stol;
80: if (maxit) *maxit = gs->max_its;
81: PetscFunctionReturn(PETSC_SUCCESS);
82: }
84: /*@
85: SNESNGSSetSweeps - Sets the number of sweeps of nonlinear GS to use in `SNESNCG`
87: Logically Collective
89: Input Parameters:
90: + snes - the `SNES` context
91: - sweeps - the number of sweeps of nonlinear GS to perform.
93: Options Database Key:
94: . -snes_ngs_sweeps <n> - Number of sweeps of nonlinear GS to apply
96: Level: intermediate
98: .seealso: [](ch_snes), `SNES`, `SNESNCG`, `SNESSetNGS()`, `SNESGetNGS()`, `SNESSetNPC()`, `SNESNGSGetSweeps()`
99: @*/
100: PetscErrorCode SNESNGSSetSweeps(SNES snes, PetscInt sweeps)
101: {
102: SNES_NGS *gs = (SNES_NGS *)snes->data;
104: PetscFunctionBegin;
106: gs->sweeps = sweeps;
107: PetscFunctionReturn(PETSC_SUCCESS);
108: }
110: /*@
111: SNESNGSGetSweeps - Gets the number of sweeps nonlinear GS will use in `SNESNCG`
113: Input Parameter:
114: . snes - the `SNES` context
116: Output Parameter:
117: . sweeps - the number of sweeps of nonlinear GS to perform.
119: Level: intermediate
121: .seealso: [](ch_snes), `SNES`, `SNESNCG`, `SNESSetNGS()`, `SNESGetNGS()`, `SNESSetNPC()`, `SNESNGSSetSweeps()`
122: @*/
123: PetscErrorCode SNESNGSGetSweeps(SNES snes, PetscInt *sweeps)
124: {
125: SNES_NGS *gs = (SNES_NGS *)snes->data;
127: PetscFunctionBegin;
129: *sweeps = gs->sweeps;
130: PetscFunctionReturn(PETSC_SUCCESS);
131: }
133: static PetscErrorCode SNESReset_NGS(SNES snes)
134: {
135: SNES_NGS *gs = (SNES_NGS *)snes->data;
137: PetscFunctionBegin;
138: PetscCall(ISColoringDestroy(&gs->coloring));
139: PetscFunctionReturn(PETSC_SUCCESS);
140: }
142: static PetscErrorCode SNESDestroy_NGS(SNES snes)
143: {
144: PetscFunctionBegin;
145: PetscCall(SNESReset_NGS(snes));
146: PetscCall(PetscFree(snes->data));
147: PetscFunctionReturn(PETSC_SUCCESS);
148: }
150: static PetscErrorCode SNESSetUp_NGS(SNES snes)
151: {
152: PetscErrorCode (*f)(SNES, Vec, Vec, void *);
154: PetscFunctionBegin;
155: PetscCall(SNESGetNGS(snes, &f, NULL));
156: if (!f) PetscCall(SNESSetNGS(snes, SNESComputeNGSDefaultSecant, NULL));
157: PetscFunctionReturn(PETSC_SUCCESS);
158: }
160: static PetscErrorCode SNESSetFromOptions_NGS(SNES snes, PetscOptionItems *PetscOptionsObject)
161: {
162: SNES_NGS *gs = (SNES_NGS *)snes->data;
163: PetscInt sweeps, max_its = PETSC_DEFAULT;
164: PetscReal rtol = PETSC_DEFAULT, atol = PETSC_DEFAULT, stol = PETSC_DEFAULT;
165: PetscBool flg, flg1, flg2, flg3;
167: PetscFunctionBegin;
168: PetscOptionsHeadBegin(PetscOptionsObject, "SNES GS options");
169: /* GS Options */
170: PetscCall(PetscOptionsInt("-snes_ngs_sweeps", "Number of sweeps of GS to apply", "SNESComputeGS", gs->sweeps, &sweeps, &flg));
171: if (flg) PetscCall(SNESNGSSetSweeps(snes, sweeps));
172: PetscCall(PetscOptionsReal("-snes_ngs_atol", "Absolute residual tolerance for GS iteration", "SNESComputeGS", gs->abstol, &atol, &flg));
173: PetscCall(PetscOptionsReal("-snes_ngs_rtol", "Relative residual tolerance for GS iteration", "SNESComputeGS", gs->rtol, &rtol, &flg1));
174: PetscCall(PetscOptionsReal("-snes_ngs_stol", "Absolute update tolerance for GS iteration", "SNESComputeGS", gs->stol, &stol, &flg2));
175: PetscCall(PetscOptionsInt("-snes_ngs_max_it", "Maximum number of sweeps of GS to apply", "SNESComputeGS", gs->max_its, &max_its, &flg3));
176: if (flg || flg1 || flg2 || flg3) PetscCall(SNESNGSSetTolerances(snes, atol, rtol, stol, max_its));
177: flg = PETSC_FALSE;
178: PetscCall(PetscOptionsBool("-snes_ngs_secant", "Use finite difference secant approximation with coloring", "", flg, &flg, NULL));
179: if (flg) {
180: PetscCall(SNESSetNGS(snes, SNESComputeNGSDefaultSecant, NULL));
181: PetscCall(PetscInfo(snes, "Setting default finite difference secant approximation with coloring\n"));
182: }
183: PetscCall(PetscOptionsReal("-snes_ngs_secant_h", "Differencing parameter for secant search", "", gs->h, &gs->h, NULL));
184: PetscCall(PetscOptionsBool("-snes_ngs_secant_mat_coloring", "Use the graph coloring of the Jacobian for the secant GS", "", gs->secant_mat, &gs->secant_mat, &flg));
186: PetscOptionsHeadEnd();
187: PetscFunctionReturn(PETSC_SUCCESS);
188: }
190: static PetscErrorCode SNESView_NGS(SNES snes, PetscViewer viewer)
191: {
192: PetscErrorCode (*f)(SNES, Vec, Vec, void *);
193: SNES_NGS *gs = (SNES_NGS *)snes->data;
194: PetscBool iascii;
196: PetscFunctionBegin;
197: PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
198: if (iascii) {
199: PetscCall(DMSNESGetNGS(snes->dm, &f, NULL));
200: if (f == SNESComputeNGSDefaultSecant) PetscCall(PetscViewerASCIIPrintf(viewer, " Use finite difference secant approximation with coloring with h = %g \n", (double)gs->h));
201: }
202: PetscFunctionReturn(PETSC_SUCCESS);
203: }
205: static PetscErrorCode SNESSolve_NGS(SNES snes)
206: {
207: Vec F;
208: Vec X;
209: Vec B;
210: PetscInt i;
211: PetscReal fnorm;
212: SNESNormSchedule normschedule;
214: PetscFunctionBegin;
216: PetscCheck(!snes->xl && !snes->xu && !snes->ops->computevariablebounds, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONGSTATE, "SNES solver %s does not support bounds", ((PetscObject)snes)->type_name);
218: PetscCall(PetscCitationsRegister(SNESCitation, &SNEScite));
219: X = snes->vec_sol;
220: F = snes->vec_func;
221: B = snes->vec_rhs;
223: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
224: snes->iter = 0;
225: snes->norm = 0.;
226: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
227: snes->reason = SNES_CONVERGED_ITERATING;
229: PetscCall(SNESGetNormSchedule(snes, &normschedule));
230: if (normschedule == SNES_NORM_ALWAYS || normschedule == SNES_NORM_INITIAL_ONLY || normschedule == SNES_NORM_INITIAL_FINAL_ONLY) {
231: /* compute the initial function and preconditioned update delX */
232: if (!snes->vec_func_init_set) {
233: PetscCall(SNESComputeFunction(snes, X, F));
234: } else snes->vec_func_init_set = PETSC_FALSE;
236: PetscCall(VecNorm(F, NORM_2, &fnorm)); /* fnorm <- ||F|| */
237: SNESCheckFunctionNorm(snes, fnorm);
238: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
239: snes->iter = 0;
240: snes->norm = fnorm;
241: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
242: PetscCall(SNESLogConvergenceHistory(snes, snes->norm, 0));
244: /* test convergence */
245: PetscCall(SNESConverged(snes, 0, 0.0, 0.0, fnorm));
246: PetscCall(SNESMonitor(snes, 0, snes->norm));
247: if (snes->reason) PetscFunctionReturn(PETSC_SUCCESS);
248: } else {
249: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
250: PetscCall(SNESLogConvergenceHistory(snes, snes->norm, 0));
251: }
253: /* Call general purpose update function */
254: PetscTryTypeMethod(snes, update, snes->iter);
256: for (i = 0; i < snes->max_its; i++) {
257: PetscCall(SNESComputeNGS(snes, B, X));
258: /* only compute norms if requested or about to exit due to maximum iterations */
259: if (normschedule == SNES_NORM_ALWAYS || ((i == snes->max_its - 1) && (normschedule == SNES_NORM_INITIAL_FINAL_ONLY || normschedule == SNES_NORM_FINAL_ONLY))) {
260: PetscCall(SNESComputeFunction(snes, X, F));
261: PetscCall(VecNorm(F, NORM_2, &fnorm)); /* fnorm <- ||F|| */
262: SNESCheckFunctionNorm(snes, fnorm);
263: }
264: /* Monitor convergence */
265: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
266: snes->iter = i + 1;
267: snes->norm = fnorm;
268: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
269: PetscCall(SNESLogConvergenceHistory(snes, snes->norm, snes->iter));
270: /* Test for convergence */
271: PetscCall(SNESConverged(snes, snes->iter, 0.0, 0.0, fnorm));
272: PetscCall(SNESMonitor(snes, snes->iter, snes->norm));
273: if (snes->reason) PetscFunctionReturn(PETSC_SUCCESS);
274: /* Call general purpose update function */
275: PetscTryTypeMethod(snes, update, snes->iter);
276: }
277: PetscFunctionReturn(PETSC_SUCCESS);
278: }
280: /*MC
281: SNESNGS - Either calls the user-provided Gauss-Seidel solution routine provided with `SNESSetNGS()` or does a finite difference secant approximation
282: using coloring {cite}`bruneknepleysmithtu15`.
284: Level: advanced
286: Options Database Keys:
287: + -snes_ngs_sweeps <n> - Number of sweeps of nonlinear GS to apply
288: . -snes_ngs_atol <atol> - Absolute residual tolerance for nonlinear GS iteration
289: . -snes_ngs_rtol <rtol> - Relative residual tolerance for nonlinear GS iteration
290: . -snes_ngs_stol <stol> - Absolute update tolerance for nonlinear GS iteration
291: . -snes_ngs_max_it <maxit> - Maximum number of sweeps of nonlinea GS to apply
292: . -snes_ngs_secant - Use pointwise secant local Jacobian approximation with coloring instead of user provided Gauss-Seidel routine,
293: this is used by default if no user provided Gauss-Seidel routine is available.
294: Requires either that a `DM` that can compute a coloring
295: is available or a Jacobian sparse matrix is provided (from which to get the coloring).
296: . -snes_ngs_secant_h <h> - Differencing parameter for secant approximation
297: . -snes_ngs_secant_mat_coloring - Use the graph coloring of the Jacobian for the secant GS even if a `DM` is available.
298: - -snes_norm_schedule <none, always, initialonly, finalonly, initialfinalonly> - how often the residual norms are computed
300: Notes:
301: the Gauss-Seidel smoother is inherited through composition. If a solver has been created with `SNESGetNPC()`, it will have
302: its parent's Gauss-Seidel routine associated with it.
304: By default this routine computes the solution norm at each iteration, this can be time consuming, you can turn this off with `SNESSetNormSchedule()`
305: or -snes_norm_schedule none
307: .seealso: [](ch_snes), `SNESNCG`, `SNESCreate()`, `SNES`, `SNESSetType()`, `SNESSetNGS()`, `SNESType`, `SNESNGSSetSweeps()`, `SNESNGSSetTolerances()`,
308: `SNESSetNormSchedule()`, `SNESNGSGetTolerances()`, `SNESNGSSetSweeps()`
309: M*/
311: PETSC_EXTERN PetscErrorCode SNESCreate_NGS(SNES snes)
312: {
313: SNES_NGS *gs;
315: PetscFunctionBegin;
316: snes->ops->destroy = SNESDestroy_NGS;
317: snes->ops->setup = SNESSetUp_NGS;
318: snes->ops->setfromoptions = SNESSetFromOptions_NGS;
319: snes->ops->view = SNESView_NGS;
320: snes->ops->solve = SNESSolve_NGS;
321: snes->ops->reset = SNESReset_NGS;
323: snes->usesksp = PETSC_FALSE;
324: snes->usesnpc = PETSC_FALSE;
326: snes->alwayscomputesfinalresidual = PETSC_FALSE;
328: if (!snes->tolerancesset) {
329: snes->max_its = 10000;
330: snes->max_funcs = 10000;
331: }
333: PetscCall(PetscNew(&gs));
335: gs->sweeps = 1;
336: gs->rtol = 1e-5;
337: gs->abstol = PETSC_MACHINE_EPSILON;
338: gs->stol = 1000 * PETSC_MACHINE_EPSILON;
339: gs->max_its = 50;
340: gs->h = PETSC_SQRT_MACHINE_EPSILON;
342: snes->data = (void *)gs;
343: PetscFunctionReturn(PETSC_SUCCESS);
344: }