Actual source code: ms.c
1: #include <petsc/private/snesimpl.h>
3: static SNESMSType SNESMSDefault = SNESMSM62;
4: static PetscBool SNESMSRegisterAllCalled;
5: static PetscBool SNESMSPackageInitialized;
7: typedef struct _SNESMSTableau *SNESMSTableau;
8: struct _SNESMSTableau {
9: char *name;
10: PetscInt nstages; /* Number of stages */
11: PetscInt nregisters; /* Number of registers */
12: PetscReal stability; /* Scaled stability region */
13: PetscReal *gamma; /* Coefficients of 3S* method */
14: PetscReal *delta; /* Coefficients of 3S* method */
15: PetscReal *betasub; /* Subdiagonal of beta in Shu-Osher form */
16: };
18: typedef struct _SNESMSTableauLink *SNESMSTableauLink;
19: struct _SNESMSTableauLink {
20: struct _SNESMSTableau tab;
21: SNESMSTableauLink next;
22: };
23: static SNESMSTableauLink SNESMSTableauList;
25: typedef struct {
26: SNESMSTableau tableau; /* Tableau in low-storage form */
27: PetscReal damping; /* Damping parameter, like length of (pseudo) time step */
28: } SNES_MS;
30: /*@C
31: SNESMSRegisterAll - Registers all of the multi-stage methods in `SNESMS`
33: Logically Collective
35: Level: developer
37: .seealso: `SNES`, `SNESMS`, `SNESMSRegisterDestroy()`
38: @*/
39: PetscErrorCode SNESMSRegisterAll(void)
40: {
41: PetscFunctionBegin;
42: if (SNESMSRegisterAllCalled) PetscFunctionReturn(PETSC_SUCCESS);
43: SNESMSRegisterAllCalled = PETSC_TRUE;
45: {
46: PetscReal alpha[1] = {1.0};
47: PetscCall(SNESMSRegister(SNESMSEULER, 1, 1, 1.0, NULL, NULL, alpha));
48: }
50: {
51: PetscReal gamma[3][6] = {
52: {0.0000000000000000E+00, -7.0304722367110606E-01, -1.9836719667506464E-01, -1.6023843981863788E+00, 9.4483822882855284E-02, -1.4204296130641869E-01},
53: {1.0000000000000000E+00, 1.1111025767083920E+00, 5.6150921583923230E-01, 7.4151723494934041E-01, 3.1714538168600587E-01, 4.6479276238548706E-01 },
54: {0.0000000000000000E+00, 0.0000000000000000E+00, 0.0000000000000000E+00, 6.7968174970583317E-01, -4.1755042846051737E-03, -1.9115668129923846E-01}
55: };
56: PetscReal delta[6] = {1.0000000000000000E+00, 5.3275427433201750E-01, 6.0143544663985238E-01, 4.5874077053842177E-01, 2.7544386906104651E-01, 0.0000000000000000E+00};
57: PetscReal betasub[6] = {8.4753115429481929E-01, 7.4018896368655618E-01, 6.5963574086583309E-03, 4.6747795645517759E-01, 1.3314545813643919E-01, 5.3260800028018784E-01};
58: PetscCall(SNESMSRegister(SNESMSM62, 6, 3, 1.0, &gamma[0][0], delta, betasub));
59: }
61: { /* Jameson (1983) */
62: PetscReal alpha[4] = {0.25, 0.5, 0.55, 1.0};
63: PetscCall(SNESMSRegister(SNESMSJAMESON83, 4, 1, 1.0, NULL, NULL, alpha));
64: }
66: { /* Van Leer, Tai, and Powell (1989) 1 stage, order 1 */
67: PetscReal alpha[1] = {1.0};
68: PetscCall(SNESMSRegister(SNESMSVLTP11, 1, 1, 0.5, NULL, NULL, alpha));
69: }
70: { /* Van Leer, Tai, and Powell (1989) 2 stage, order 1 */
71: PetscReal alpha[2] = {0.3333, 1.0};
72: PetscCall(SNESMSRegister(SNESMSVLTP21, 2, 1, 1.0, NULL, NULL, alpha));
73: }
74: { /* Van Leer, Tai, and Powell (1989) 3 stage, order 1 */
75: PetscReal alpha[3] = {0.1481, 0.4000, 1.0};
76: PetscCall(SNESMSRegister(SNESMSVLTP31, 3, 1, 1.5, NULL, NULL, alpha));
77: }
78: { /* Van Leer, Tai, and Powell (1989) 4 stage, order 1 */
79: PetscReal alpha[4] = {0.0833, 0.2069, 0.4265, 1.0};
80: PetscCall(SNESMSRegister(SNESMSVLTP41, 4, 1, 2.0, NULL, NULL, alpha));
81: }
82: { /* Van Leer, Tai, and Powell (1989) 5 stage, order 1 */
83: PetscReal alpha[5] = {0.0533, 0.1263, 0.2375, 0.4414, 1.0};
84: PetscCall(SNESMSRegister(SNESMSVLTP51, 5, 1, 2.5, NULL, NULL, alpha));
85: }
86: { /* Van Leer, Tai, and Powell (1989) 6 stage, order 1 */
87: PetscReal alpha[6] = {0.0370, 0.0851, 0.1521, 0.2562, 0.4512, 1.0};
88: PetscCall(SNESMSRegister(SNESMSVLTP61, 6, 1, 3.0, NULL, NULL, alpha));
89: }
90: PetscFunctionReturn(PETSC_SUCCESS);
91: }
93: /*@C
94: SNESMSRegisterDestroy - Frees the list of schemes that were registered by `SNESMSRegister()`.
96: Not Collective
98: Level: developer
100: .seealso: `SNESMSRegister()`, `SNESMSRegisterAll()`
101: @*/
102: PetscErrorCode SNESMSRegisterDestroy(void)
103: {
104: SNESMSTableauLink link;
106: PetscFunctionBegin;
107: while ((link = SNESMSTableauList)) {
108: SNESMSTableau t = &link->tab;
109: SNESMSTableauList = link->next;
111: PetscCall(PetscFree(t->name));
112: PetscCall(PetscFree(t->gamma));
113: PetscCall(PetscFree(t->delta));
114: PetscCall(PetscFree(t->betasub));
115: PetscCall(PetscFree(link));
116: }
117: SNESMSRegisterAllCalled = PETSC_FALSE;
118: PetscFunctionReturn(PETSC_SUCCESS);
119: }
121: /*@C
122: SNESMSInitializePackage - This function initializes everything in the `SNESMS` package. It is called
123: from `SNESInitializePackage()`.
125: Level: developer
127: .seealso: `PetscInitialize()`
128: @*/
129: PetscErrorCode SNESMSInitializePackage(void)
130: {
131: PetscFunctionBegin;
132: if (SNESMSPackageInitialized) PetscFunctionReturn(PETSC_SUCCESS);
133: SNESMSPackageInitialized = PETSC_TRUE;
135: PetscCall(SNESMSRegisterAll());
136: PetscCall(PetscRegisterFinalize(SNESMSFinalizePackage));
137: PetscFunctionReturn(PETSC_SUCCESS);
138: }
140: /*@C
141: SNESMSFinalizePackage - This function destroys everything in the `SNESMS` package. It is
142: called from `PetscFinalize()`.
144: Level: developer
146: .seealso: `PetscFinalize()`
147: @*/
148: PetscErrorCode SNESMSFinalizePackage(void)
149: {
150: PetscFunctionBegin;
151: SNESMSPackageInitialized = PETSC_FALSE;
153: PetscCall(SNESMSRegisterDestroy());
154: PetscFunctionReturn(PETSC_SUCCESS);
155: }
157: /*@C
158: SNESMSRegister - register a multistage scheme for `SNESMS`
160: Logically Collective
162: Input Parameters:
163: + name - identifier for method
164: . nstages - number of stages
165: . nregisters - number of registers used by low-storage implementation
166: . stability - scaled stability region
167: . gamma - coefficients, see Ketcheson's paper
168: . delta - coefficients, see Ketcheson's paper
169: - betasub - subdiagonal of Shu-Osher form
171: Level: advanced
173: Notes:
174: The notation is described in Ketcheson (2010) Runge-Kutta methods with minimum storage implementations.
176: Many multistage schemes are of the form
177: $ X_0 = X^{(n)}
178: $ X_k = X_0 + \alpha_k * F(X_{k-1}), k = 1,\ldots,s
179: $ X^{(n+1)} = X_s
180: These methods can be registered with
181: .vb
182: SNESMSRegister("name",s,1,stability,NULL,NULL,alpha);
183: .ve
185: .seealso: `SNESMS`
186: @*/
187: PetscErrorCode SNESMSRegister(SNESMSType name, PetscInt nstages, PetscInt nregisters, PetscReal stability, const PetscReal gamma[], const PetscReal delta[], const PetscReal betasub[])
188: {
189: SNESMSTableauLink link;
190: SNESMSTableau t;
192: PetscFunctionBegin;
193: PetscAssertPointer(name, 1);
194: PetscCheck(nstages >= 1, PETSC_COMM_SELF, PETSC_ERR_ARG_OUTOFRANGE, "Must have at least one stage");
195: if (gamma || delta) {
196: PetscCheck(nregisters == 3, PETSC_COMM_SELF, PETSC_ERR_SUP, "Only support for methods written in 3-register form");
197: PetscAssertPointer(gamma, 5);
198: PetscAssertPointer(delta, 6);
199: } else {
200: PetscCheck(nregisters == 1, PETSC_COMM_SELF, PETSC_ERR_SUP, "Only support for methods written in 1-register form");
201: }
202: PetscAssertPointer(betasub, 7);
204: PetscCall(SNESMSInitializePackage());
205: PetscCall(PetscNew(&link));
206: t = &link->tab;
207: PetscCall(PetscStrallocpy(name, &t->name));
208: t->nstages = nstages;
209: t->nregisters = nregisters;
210: t->stability = stability;
212: if (gamma && delta) {
213: PetscCall(PetscMalloc1(nstages * nregisters, &t->gamma));
214: PetscCall(PetscMalloc1(nstages, &t->delta));
215: PetscCall(PetscArraycpy(t->gamma, gamma, nstages * nregisters));
216: PetscCall(PetscArraycpy(t->delta, delta, nstages));
217: }
218: PetscCall(PetscMalloc1(nstages, &t->betasub));
219: PetscCall(PetscArraycpy(t->betasub, betasub, nstages));
221: link->next = SNESMSTableauList;
222: SNESMSTableauList = link;
223: PetscFunctionReturn(PETSC_SUCCESS);
224: }
226: /*
227: X - initial state, updated in-place.
228: F - residual, computed at the initial X on input
229: */
230: static PetscErrorCode SNESMSStep_3Sstar(SNES snes, Vec X, Vec F)
231: {
232: SNES_MS *ms = (SNES_MS *)snes->data;
233: SNESMSTableau t = ms->tableau;
234: const PetscInt nstages = t->nstages;
235: const PetscReal *gamma = t->gamma, *delta = t->delta, *betasub = t->betasub;
236: Vec S1 = X, S2 = snes->work[1], S3 = snes->work[2], Y = snes->work[0], S1copy = snes->work[3];
238: PetscFunctionBegin;
239: PetscCall(VecZeroEntries(S2));
240: PetscCall(VecCopy(X, S3));
241: for (PetscInt i = 0; i < nstages; i++) {
242: Vec Ss[] = {S1copy, S2, S3, Y};
243: const PetscScalar scoeff[] = {gamma[0 * nstages + i] - 1, gamma[1 * nstages + i], gamma[2 * nstages + i], -betasub[i] * ms->damping};
245: PetscCall(VecAXPY(S2, delta[i], S1));
246: if (i > 0) PetscCall(SNESComputeFunction(snes, S1, F));
247: PetscCall(KSPSolve(snes->ksp, F, Y));
248: PetscCall(VecCopy(S1, S1copy));
249: PetscCall(VecMAXPY(S1, 4, scoeff, Ss));
250: }
251: PetscFunctionReturn(PETSC_SUCCESS);
252: }
254: /*
255: X - initial state, updated in-place.
256: F - residual, computed at the initial X on input
257: */
258: static PetscErrorCode SNESMSStep_Basic(SNES snes, Vec X, Vec F)
259: {
260: SNES_MS *ms = (SNES_MS *)snes->data;
261: SNESMSTableau tab = ms->tableau;
262: const PetscReal *alpha = tab->betasub, h = ms->damping;
263: PetscInt i, nstages = tab->nstages;
264: Vec X0 = snes->work[0];
266: PetscFunctionBegin;
267: PetscCall(VecCopy(X, X0));
268: for (i = 0; i < nstages; i++) {
269: if (i > 0) PetscCall(SNESComputeFunction(snes, X, F));
270: PetscCall(KSPSolve(snes->ksp, F, X));
271: PetscCall(VecAYPX(X, -alpha[i] * h, X0));
272: }
273: PetscFunctionReturn(PETSC_SUCCESS);
274: }
276: static PetscErrorCode SNESMSStep_Step(SNES snes, Vec X, Vec F)
277: {
278: SNES_MS *ms = (SNES_MS *)snes->data;
279: SNESMSTableau tab = ms->tableau;
281: PetscFunctionBegin;
282: if (tab->gamma && tab->delta) {
283: PetscCall(SNESMSStep_3Sstar(snes, X, F));
284: } else {
285: PetscCall(SNESMSStep_Basic(snes, X, F));
286: }
287: PetscFunctionReturn(PETSC_SUCCESS);
288: }
290: static PetscErrorCode SNESMSStep_Norms(SNES snes, PetscInt iter, Vec F)
291: {
292: PetscReal fnorm;
294: PetscFunctionBegin;
295: if (SNESNeedNorm_Private(snes, iter)) {
296: PetscCall(VecNorm(F, NORM_2, &fnorm)); /* fnorm <- ||F|| */
297: SNESCheckFunctionNorm(snes, fnorm);
298: /* Monitor convergence */
299: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
300: snes->iter = iter;
301: snes->norm = fnorm;
302: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
303: PetscCall(SNESLogConvergenceHistory(snes, snes->norm, 0));
304: /* Test for convergence */
305: PetscCall(SNESConverged(snes, snes->iter, 0.0, 0.0, fnorm));
306: PetscCall(SNESMonitor(snes, snes->iter, snes->norm));
307: } else if (iter > 0) {
308: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
309: snes->iter = iter;
310: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
311: }
312: PetscFunctionReturn(PETSC_SUCCESS);
313: }
315: static PetscErrorCode SNESSolve_MS(SNES snes)
316: {
317: Vec X = snes->vec_sol, F = snes->vec_func;
318: PetscInt i;
320: PetscFunctionBegin;
321: 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);
322: PetscCall(PetscCitationsRegister(SNESCitation, &SNEScite));
324: snes->reason = SNES_CONVERGED_ITERATING;
325: PetscCall(PetscObjectSAWsTakeAccess((PetscObject)snes));
326: snes->iter = 0;
327: snes->norm = 0;
328: PetscCall(PetscObjectSAWsGrantAccess((PetscObject)snes));
330: if (!snes->vec_func_init_set) {
331: PetscCall(SNESComputeFunction(snes, X, F));
332: } else snes->vec_func_init_set = PETSC_FALSE;
334: PetscCall(SNESMSStep_Norms(snes, 0, F));
335: if (snes->reason) PetscFunctionReturn(PETSC_SUCCESS);
337: for (i = 0; i < snes->max_its; i++) {
338: /* Call general purpose update function */
339: PetscTryTypeMethod(snes, update, snes->iter);
341: if (i == 0 && snes->jacobian) {
342: /* This method does not require a Jacobian, but it is usually preconditioned by PBJacobi */
343: PetscCall(SNESComputeJacobian(snes, snes->vec_sol, snes->jacobian, snes->jacobian_pre));
344: SNESCheckJacobianDomainerror(snes);
345: PetscCall(KSPSetOperators(snes->ksp, snes->jacobian, snes->jacobian_pre));
346: }
348: PetscCall(SNESMSStep_Step(snes, X, F));
350: if (i < snes->max_its - 1 || SNESNeedNorm_Private(snes, i + 1)) PetscCall(SNESComputeFunction(snes, X, F));
352: PetscCall(SNESMSStep_Norms(snes, i + 1, F));
353: if (snes->reason) PetscFunctionReturn(PETSC_SUCCESS);
354: }
355: PetscFunctionReturn(PETSC_SUCCESS);
356: }
358: static PetscErrorCode SNESSetUp_MS(SNES snes)
359: {
360: SNES_MS *ms = (SNES_MS *)snes->data;
361: SNESMSTableau tab = ms->tableau;
362: PetscInt nwork = tab->nregisters + 1; // +1 because VecMAXPY() in SNESMSStep_3Sstar()
363: // needs an extra work vec
365: PetscFunctionBegin;
366: PetscCall(SNESSetWorkVecs(snes, nwork));
367: PetscCall(SNESSetUpMatrices(snes));
368: PetscFunctionReturn(PETSC_SUCCESS);
369: }
371: static PetscErrorCode SNESReset_MS(SNES snes)
372: {
373: PetscFunctionBegin;
374: PetscFunctionReturn(PETSC_SUCCESS);
375: }
377: static PetscErrorCode SNESDestroy_MS(SNES snes)
378: {
379: PetscFunctionBegin;
380: PetscCall(SNESReset_MS(snes));
381: PetscCall(PetscFree(snes->data));
382: PetscCall(PetscObjectComposeFunction((PetscObject)snes, "SNESMSGetType_C", NULL));
383: PetscCall(PetscObjectComposeFunction((PetscObject)snes, "SNESMSSetType_C", NULL));
384: PetscCall(PetscObjectComposeFunction((PetscObject)snes, "SNESMSGetDamping_C", NULL));
385: PetscCall(PetscObjectComposeFunction((PetscObject)snes, "SNESMSSetDamping_C", NULL));
386: PetscFunctionReturn(PETSC_SUCCESS);
387: }
389: static PetscErrorCode SNESView_MS(SNES snes, PetscViewer viewer)
390: {
391: PetscBool iascii;
392: SNES_MS *ms = (SNES_MS *)snes->data;
393: SNESMSTableau tab = ms->tableau;
395: PetscFunctionBegin;
396: PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
397: if (iascii) PetscCall(PetscViewerASCIIPrintf(viewer, " multi-stage method type: %s\n", tab->name));
398: PetscFunctionReturn(PETSC_SUCCESS);
399: }
401: static PetscErrorCode SNESSetFromOptions_MS(SNES snes, PetscOptionItems *PetscOptionsObject)
402: {
403: PetscFunctionBegin;
404: PetscOptionsHeadBegin(PetscOptionsObject, "SNES MS options");
405: {
406: SNESMSTableauLink link;
407: PetscInt count, choice;
408: PetscBool flg;
409: const char **namelist;
410: SNESMSType mstype;
411: PetscReal damping;
412: PetscBool norms = PETSC_FALSE;
414: PetscCall(SNESMSGetType(snes, &mstype));
415: for (link = SNESMSTableauList, count = 0; link; link = link->next, count++)
416: ;
417: PetscCall(PetscMalloc1(count, (char ***)&namelist));
418: for (link = SNESMSTableauList, count = 0; link; link = link->next, count++) namelist[count] = link->tab.name;
419: PetscCall(PetscOptionsEList("-snes_ms_type", "Multistage smoother type", "SNESMSSetType", (const char *const *)namelist, count, mstype, &choice, &flg));
420: if (flg) PetscCall(SNESMSSetType(snes, namelist[choice]));
421: PetscCall(PetscFree(namelist));
422: PetscCall(SNESMSGetDamping(snes, &damping));
423: PetscCall(PetscOptionsReal("-snes_ms_damping", "Damping for multistage method", "SNESMSSetDamping", damping, &damping, &flg));
424: if (flg) PetscCall(SNESMSSetDamping(snes, damping));
426: /* deprecated option */
427: PetscCall(PetscOptionsDeprecated("-snes_ms_norms", NULL, "3.20", "Use -snes_norm_schedule always"));
428: PetscCall(PetscOptionsBool("-snes_ms_norms", NULL, NULL, norms, &norms, NULL));
429: if (norms) PetscCall(SNESSetNormSchedule(snes, SNES_NORM_ALWAYS));
430: }
431: PetscOptionsHeadEnd();
432: PetscFunctionReturn(PETSC_SUCCESS);
433: }
435: static PetscErrorCode SNESMSGetType_MS(SNES snes, SNESMSType *mstype)
436: {
437: SNES_MS *ms = (SNES_MS *)snes->data;
438: SNESMSTableau tab = ms->tableau;
440: PetscFunctionBegin;
441: *mstype = tab->name;
442: PetscFunctionReturn(PETSC_SUCCESS);
443: }
445: static PetscErrorCode SNESMSSetType_MS(SNES snes, SNESMSType mstype)
446: {
447: SNES_MS *ms = (SNES_MS *)snes->data;
448: SNESMSTableauLink link;
449: PetscBool match;
451: PetscFunctionBegin;
452: if (ms->tableau) {
453: PetscCall(PetscStrcmp(ms->tableau->name, mstype, &match));
454: if (match) PetscFunctionReturn(PETSC_SUCCESS);
455: }
456: for (link = SNESMSTableauList; link; link = link->next) {
457: PetscCall(PetscStrcmp(link->tab.name, mstype, &match));
458: if (match) {
459: if (snes->setupcalled) PetscCall(SNESReset_MS(snes));
460: ms->tableau = &link->tab;
461: if (snes->setupcalled) PetscCall(SNESSetUp_MS(snes));
462: PetscFunctionReturn(PETSC_SUCCESS);
463: }
464: }
465: SETERRQ(PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_UNKNOWN_TYPE, "Could not find '%s'", mstype);
466: }
468: /*@C
469: SNESMSGetType - Get the type of multistage smoother `SNESMS`
471: Not Collective
473: Input Parameter:
474: . snes - nonlinear solver context
476: Output Parameter:
477: . mstype - type of multistage method
479: Level: advanced
481: .seealso: `SNESMS`, `SNESMSSetType()`, `SNESMSType`
482: @*/
483: PetscErrorCode SNESMSGetType(SNES snes, SNESMSType *mstype)
484: {
485: PetscFunctionBegin;
487: PetscAssertPointer(mstype, 2);
488: PetscUseMethod(snes, "SNESMSGetType_C", (SNES, SNESMSType *), (snes, mstype));
489: PetscFunctionReturn(PETSC_SUCCESS);
490: }
492: /*@C
493: SNESMSSetType - Set the type of multistage smoother `SNESMS`
495: Logically Collective
497: Input Parameters:
498: + snes - nonlinear solver context
499: - mstype - type of multistage method
501: Level: advanced
503: .seealso: `SNESMS`, `SNESMSGetType()`, `SNESMSType`
504: @*/
505: PetscErrorCode SNESMSSetType(SNES snes, SNESMSType mstype)
506: {
507: PetscFunctionBegin;
509: PetscAssertPointer(mstype, 2);
510: PetscTryMethod(snes, "SNESMSSetType_C", (SNES, SNESMSType), (snes, mstype));
511: PetscFunctionReturn(PETSC_SUCCESS);
512: }
514: static PetscErrorCode SNESMSGetDamping_MS(SNES snes, PetscReal *damping)
515: {
516: SNES_MS *ms = (SNES_MS *)snes->data;
518: PetscFunctionBegin;
519: *damping = ms->damping;
520: PetscFunctionReturn(PETSC_SUCCESS);
521: }
523: static PetscErrorCode SNESMSSetDamping_MS(SNES snes, PetscReal damping)
524: {
525: SNES_MS *ms = (SNES_MS *)snes->data;
527: PetscFunctionBegin;
528: ms->damping = damping;
529: PetscFunctionReturn(PETSC_SUCCESS);
530: }
532: /*@C
533: SNESMSGetDamping - Get the damping parameter of `SNESMS` multistage scheme
535: Not Collective
537: Input Parameter:
538: . snes - nonlinear solver context
540: Output Parameter:
541: . damping - damping parameter
543: Level: advanced
545: .seealso: `SNESMSSetDamping()`, `SNESMS`
546: @*/
547: PetscErrorCode SNESMSGetDamping(SNES snes, PetscReal *damping)
548: {
549: PetscFunctionBegin;
551: PetscAssertPointer(damping, 2);
552: PetscUseMethod(snes, "SNESMSGetDamping_C", (SNES, PetscReal *), (snes, damping));
553: PetscFunctionReturn(PETSC_SUCCESS);
554: }
556: /*@C
557: SNESMSSetDamping - Set the damping parameter for a `SNESMS` multistage scheme
559: Logically Collective
561: Input Parameters:
562: + snes - nonlinear solver context
563: - damping - damping parameter
565: Level: advanced
567: .seealso: `SNESMSGetDamping()`, `SNESMS`
568: @*/
569: PetscErrorCode SNESMSSetDamping(SNES snes, PetscReal damping)
570: {
571: PetscFunctionBegin;
574: PetscTryMethod(snes, "SNESMSSetDamping_C", (SNES, PetscReal), (snes, damping));
575: PetscFunctionReturn(PETSC_SUCCESS);
576: }
578: /*MC
579: SNESMS - multi-stage smoothers
581: Options Database Keys:
582: + -snes_ms_type - type of multi-stage smoother
583: - -snes_ms_damping - damping for multi-stage method
585: Notes:
586: These multistage methods are explicit Runge-Kutta methods that are often used as smoothers for
587: FAS multigrid for transport problems. In the linear case, these are equivalent to polynomial smoothers (such as Chebyshev).
589: Multi-stage smoothers should usually be preconditioned by point-block Jacobi to ensure proper scaling and to normalize the wave speeds.
591: The methods are specified in low storage form (Ketcheson 2010). New methods can be registered with `SNESMSRegister()`.
593: References:
594: + * - Ketcheson (2010) Runge Kutta methods with minimum storage implementations (https://doi.org/10.1016/j.jcp.2009.11.006).
595: . * - Jameson (1983) Solution of the Euler equations for two dimensional transonic flow by a multigrid method (https://doi.org/10.1016/0096-3003(83)90019-X).
596: . * - Pierce and Giles (1997) Preconditioned multigrid methods for compressible flow calculations on stretched meshes (https://doi.org/10.1006/jcph.1997.5772).
597: - * - Van Leer, Tai, and Powell (1989) Design of optimally smoothing multi-stage schemes for the Euler equations (https://doi.org/10.2514/6.1989-1933).
599: Level: advanced
601: .seealso: `SNESCreate()`, `SNES`, `SNESSetType()`, `SNESMS`, `SNESFAS`, `KSPCHEBYSHEV`
603: M*/
604: PETSC_EXTERN PetscErrorCode SNESCreate_MS(SNES snes)
605: {
606: SNES_MS *ms;
608: PetscFunctionBegin;
609: PetscCall(SNESMSInitializePackage());
611: snes->ops->setup = SNESSetUp_MS;
612: snes->ops->solve = SNESSolve_MS;
613: snes->ops->destroy = SNESDestroy_MS;
614: snes->ops->setfromoptions = SNESSetFromOptions_MS;
615: snes->ops->view = SNESView_MS;
616: snes->ops->reset = SNESReset_MS;
618: snes->usesnpc = PETSC_FALSE;
619: snes->usesksp = PETSC_TRUE;
621: snes->alwayscomputesfinalresidual = PETSC_FALSE;
623: PetscCall(PetscNew(&ms));
624: snes->data = (void *)ms;
625: ms->damping = 0.9;
627: PetscCall(PetscObjectComposeFunction((PetscObject)snes, "SNESMSGetType_C", SNESMSGetType_MS));
628: PetscCall(PetscObjectComposeFunction((PetscObject)snes, "SNESMSSetType_C", SNESMSSetType_MS));
629: PetscCall(PetscObjectComposeFunction((PetscObject)snes, "SNESMSGetDamping_C", SNESMSGetDamping_MS));
630: PetscCall(PetscObjectComposeFunction((PetscObject)snes, "SNESMSSetDamping_C", SNESMSSetDamping_MS));
632: PetscCall(SNESMSSetType(snes, SNESMSDefault));
633: PetscFunctionReturn(PETSC_SUCCESS);
634: }