xref: /petsc/src/snes/interface/snes.c (revision e135a767bf200774f58f781715da93cbdf84a07a)
1 
2 #include <petsc-private/snesimpl.h>      /*I "petscsnes.h"  I*/
3 #include <petscdmshell.h>
4 
5 PetscBool         SNESRegisterAllCalled = PETSC_FALSE;
6 PetscFunctionList SNESList              = NULL;
7 
8 /* Logging support */
9 PetscClassId  SNES_CLASSID, DMSNES_CLASSID;
10 PetscLogEvent SNES_Solve, SNES_FunctionEval, SNES_JacobianEval, SNES_GSEval, SNES_GSFuncEval, SNES_NPCSolve;
11 
12 #undef __FUNCT__
13 #define __FUNCT__ "SNESSetErrorIfNotConverged"
14 /*@
15    SNESSetErrorIfNotConverged - Causes SNESSolve() to generate an error if the solver has not converged.
16 
17    Logically Collective on SNES
18 
19    Input Parameters:
20 +  snes - iterative context obtained from SNESCreate()
21 -  flg - PETSC_TRUE indicates you want the error generated
22 
23    Options database keys:
24 .  -snes_error_if_not_converged : this takes an optional truth value (0/1/no/yes/true/false)
25 
26    Level: intermediate
27 
28    Notes:
29     Normally PETSc continues if a linear solver fails to converge, you can call SNESGetConvergedReason() after a SNESSolve()
30     to determine if it has converged.
31 
32 .keywords: SNES, set, initial guess, nonzero
33 
34 .seealso: SNESGetErrorIfNotConverged(), KSPGetErrorIfNotConverged(), KSPSetErrorIFNotConverged()
35 @*/
36 PetscErrorCode  SNESSetErrorIfNotConverged(SNES snes,PetscBool flg)
37 {
38   PetscFunctionBegin;
39   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
40   PetscValidLogicalCollectiveBool(snes,flg,2);
41   snes->errorifnotconverged = flg;
42   PetscFunctionReturn(0);
43 }
44 
45 #undef __FUNCT__
46 #define __FUNCT__ "SNESGetErrorIfNotConverged"
47 /*@
48    SNESGetErrorIfNotConverged - Will SNESSolve() generate an error if the solver does not converge?
49 
50    Not Collective
51 
52    Input Parameter:
53 .  snes - iterative context obtained from SNESCreate()
54 
55    Output Parameter:
56 .  flag - PETSC_TRUE if it will generate an error, else PETSC_FALSE
57 
58    Level: intermediate
59 
60 .keywords: SNES, set, initial guess, nonzero
61 
62 .seealso:  SNESSetErrorIfNotConverged(), KSPGetErrorIfNotConverged(), KSPSetErrorIFNotConverged()
63 @*/
64 PetscErrorCode  SNESGetErrorIfNotConverged(SNES snes,PetscBool  *flag)
65 {
66   PetscFunctionBegin;
67   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
68   PetscValidPointer(flag,2);
69   *flag = snes->errorifnotconverged;
70   PetscFunctionReturn(0);
71 }
72 
73 #undef __FUNCT__
74 #define __FUNCT__ "SNESSetFunctionDomainError"
75 /*@
76    SNESSetFunctionDomainError - tells SNES that the input vector to your SNESFunction is not
77      in the functions domain. For example, negative pressure.
78 
79    Logically Collective on SNES
80 
81    Input Parameters:
82 .  snes - the SNES context
83 
84    Level: advanced
85 
86 .keywords: SNES, view
87 
88 .seealso: SNESCreate(), SNESSetFunction(), SNESFunction
89 @*/
90 PetscErrorCode  SNESSetFunctionDomainError(SNES snes)
91 {
92   PetscFunctionBegin;
93   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
94   snes->domainerror = PETSC_TRUE;
95   PetscFunctionReturn(0);
96 }
97 
98 #undef __FUNCT__
99 #define __FUNCT__ "SNESGetFunctionDomainError"
100 /*@
101    SNESGetFunctionDomainError - Gets the status of the domain error after a call to SNESComputeFunction;
102 
103    Logically Collective on SNES
104 
105    Input Parameters:
106 .  snes - the SNES context
107 
108    Output Parameters:
109 .  domainerror - Set to PETSC_TRUE if there's a domain error; PETSC_FALSE otherwise.
110 
111    Level: advanced
112 
113 .keywords: SNES, view
114 
115 .seealso: SNESSetFunctionDomainError(), SNESComputeFunction()
116 @*/
117 PetscErrorCode  SNESGetFunctionDomainError(SNES snes, PetscBool *domainerror)
118 {
119   PetscFunctionBegin;
120   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
121   PetscValidPointer(domainerror, 2);
122   *domainerror = snes->domainerror;
123   PetscFunctionReturn(0);
124 }
125 
126 #undef __FUNCT__
127 #define __FUNCT__ "SNESLoad"
128 /*@C
129   SNESLoad - Loads a SNES that has been stored in binary  with SNESView().
130 
131   Collective on PetscViewer
132 
133   Input Parameters:
134 + newdm - the newly loaded SNES, this needs to have been created with SNESCreate() or
135            some related function before a call to SNESLoad().
136 - viewer - binary file viewer, obtained from PetscViewerBinaryOpen()
137 
138    Level: intermediate
139 
140   Notes:
141    The type is determined by the data in the file, any type set into the SNES before this call is ignored.
142 
143   Notes for advanced users:
144   Most users should not need to know the details of the binary storage
145   format, since SNESLoad() and TSView() completely hide these details.
146   But for anyone who's interested, the standard binary matrix storage
147   format is
148 .vb
149      has not yet been determined
150 .ve
151 
152 .seealso: PetscViewerBinaryOpen(), SNESView(), MatLoad(), VecLoad()
153 @*/
154 PetscErrorCode  SNESLoad(SNES snes, PetscViewer viewer)
155 {
156   PetscErrorCode ierr;
157   PetscBool      isbinary;
158   PetscInt       classid;
159   char           type[256];
160   KSP            ksp;
161   DM             dm;
162   DMSNES         dmsnes;
163 
164   PetscFunctionBegin;
165   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
166   PetscValidHeaderSpecific(viewer,PETSC_VIEWER_CLASSID,2);
167   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);CHKERRQ(ierr);
168   if (!isbinary) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONG,"Invalid viewer; open viewer with PetscViewerBinaryOpen()");
169 
170   ierr = PetscViewerBinaryRead(viewer,&classid,1,PETSC_INT);CHKERRQ(ierr);
171   if (classid != SNES_FILE_CLASSID) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONG,"Not SNES next in file");
172   ierr = PetscViewerBinaryRead(viewer,type,256,PETSC_CHAR);CHKERRQ(ierr);
173   ierr = SNESSetType(snes, type);CHKERRQ(ierr);
174   if (snes->ops->load) {
175     ierr = (*snes->ops->load)(snes,viewer);CHKERRQ(ierr);
176   }
177   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
178   ierr = DMGetDMSNES(dm,&dmsnes);CHKERRQ(ierr);
179   ierr = DMSNESLoad(dmsnes,viewer);CHKERRQ(ierr);
180   ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
181   ierr = KSPLoad(ksp,viewer);CHKERRQ(ierr);
182   PetscFunctionReturn(0);
183 }
184 
185 #include <petscdraw.h>
186 #if defined(PETSC_HAVE_AMS)
187 #include <petscviewerams.h>
188 #endif
189 #undef __FUNCT__
190 #define __FUNCT__ "SNESView"
191 /*@C
192    SNESView - Prints the SNES data structure.
193 
194    Collective on SNES
195 
196    Input Parameters:
197 +  SNES - the SNES context
198 -  viewer - visualization context
199 
200    Options Database Key:
201 .  -snes_view - Calls SNESView() at end of SNESSolve()
202 
203    Notes:
204    The available visualization contexts include
205 +     PETSC_VIEWER_STDOUT_SELF - standard output (default)
206 -     PETSC_VIEWER_STDOUT_WORLD - synchronized standard
207          output where only the first processor opens
208          the file.  All other processors send their
209          data to the first processor to print.
210 
211    The user can open an alternative visualization context with
212    PetscViewerASCIIOpen() - output to a specified file.
213 
214    Level: beginner
215 
216 .keywords: SNES, view
217 
218 .seealso: PetscViewerASCIIOpen()
219 @*/
220 PetscErrorCode  SNESView(SNES snes,PetscViewer viewer)
221 {
222   SNESKSPEW      *kctx;
223   PetscErrorCode ierr;
224   KSP            ksp;
225   SNESLineSearch linesearch;
226   PetscBool      iascii,isstring,isbinary,isdraw;
227   DMSNES         dmsnes;
228 #if defined(PETSC_HAVE_AMS)
229   PetscBool      isams;
230 #endif
231 
232   PetscFunctionBegin;
233   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
234   if (!viewer) {
235     ierr = PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&viewer);CHKERRQ(ierr);
236   }
237   PetscValidHeaderSpecific(viewer,PETSC_VIEWER_CLASSID,2);
238   PetscCheckSameComm(snes,1,viewer,2);
239 
240   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr);
241   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);CHKERRQ(ierr);
242   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);CHKERRQ(ierr);
243   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERDRAW,&isdraw);CHKERRQ(ierr);
244 #if defined(PETSC_HAVE_AMS)
245   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERAMS,&isams);CHKERRQ(ierr);
246 #endif
247   if (iascii) {
248     ierr = PetscObjectPrintClassNamePrefixType((PetscObject)snes,viewer);CHKERRQ(ierr);
249     if (!snes->setupcalled) {
250       ierr = PetscViewerASCIIPrintf(viewer,"  SNES has not been set up so information may be incomplete\n");CHKERRQ(ierr);
251     }
252     if (snes->ops->view) {
253       ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
254       ierr = (*snes->ops->view)(snes,viewer);CHKERRQ(ierr);
255       ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
256     }
257     ierr = PetscViewerASCIIPrintf(viewer,"  maximum iterations=%D, maximum function evaluations=%D\n",snes->max_its,snes->max_funcs);CHKERRQ(ierr);
258     ierr = PetscViewerASCIIPrintf(viewer,"  tolerances: relative=%G, absolute=%G, solution=%G\n",snes->rtol,snes->abstol,snes->stol);CHKERRQ(ierr);
259     ierr = PetscViewerASCIIPrintf(viewer,"  total number of linear solver iterations=%D\n",snes->linear_its);CHKERRQ(ierr);
260     ierr = PetscViewerASCIIPrintf(viewer,"  total number of function evaluations=%D\n",snes->nfuncs);CHKERRQ(ierr);
261     if (snes->gridsequence) {
262       ierr = PetscViewerASCIIPrintf(viewer,"  total number of grid sequence refinements=%D\n",snes->gridsequence);CHKERRQ(ierr);
263     }
264     if (snes->ksp_ewconv) {
265       kctx = (SNESKSPEW*)snes->kspconvctx;
266       if (kctx) {
267         ierr = PetscViewerASCIIPrintf(viewer,"  Eisenstat-Walker computation of KSP relative tolerance (version %D)\n",kctx->version);CHKERRQ(ierr);
268         ierr = PetscViewerASCIIPrintf(viewer,"    rtol_0=%G, rtol_max=%G, threshold=%G\n",kctx->rtol_0,kctx->rtol_max,kctx->threshold);CHKERRQ(ierr);
269         ierr = PetscViewerASCIIPrintf(viewer,"    gamma=%G, alpha=%G, alpha2=%G\n",kctx->gamma,kctx->alpha,kctx->alpha2);CHKERRQ(ierr);
270       }
271     }
272     if (snes->lagpreconditioner == -1) {
273       ierr = PetscViewerASCIIPrintf(viewer,"  Preconditioned is never rebuilt\n");CHKERRQ(ierr);
274     } else if (snes->lagpreconditioner > 1) {
275       ierr = PetscViewerASCIIPrintf(viewer,"  Preconditioned is rebuilt every %D new Jacobians\n",snes->lagpreconditioner);CHKERRQ(ierr);
276     }
277     if (snes->lagjacobian == -1) {
278       ierr = PetscViewerASCIIPrintf(viewer,"  Jacobian is never rebuilt\n");CHKERRQ(ierr);
279     } else if (snes->lagjacobian > 1) {
280       ierr = PetscViewerASCIIPrintf(viewer,"  Jacobian is rebuilt every %D SNES iterations\n",snes->lagjacobian);CHKERRQ(ierr);
281     }
282   } else if (isstring) {
283     const char *type;
284     ierr = SNESGetType(snes,&type);CHKERRQ(ierr);
285     ierr = PetscViewerStringSPrintf(viewer," %-3.3s",type);CHKERRQ(ierr);
286   } else if (isbinary) {
287     PetscInt    classid = SNES_FILE_CLASSID;
288     MPI_Comm    comm;
289     PetscMPIInt rank;
290     char        type[256];
291 
292     ierr = PetscObjectGetComm((PetscObject)snes,&comm);CHKERRQ(ierr);
293     ierr = MPI_Comm_rank(comm,&rank);CHKERRQ(ierr);
294     if (!rank) {
295       ierr = PetscViewerBinaryWrite(viewer,&classid,1,PETSC_INT,PETSC_FALSE);CHKERRQ(ierr);
296       ierr = PetscStrncpy(type,((PetscObject)snes)->type_name,256);CHKERRQ(ierr);
297       ierr = PetscViewerBinaryWrite(viewer,type,256,PETSC_CHAR,PETSC_FALSE);CHKERRQ(ierr);
298     }
299     if (snes->ops->view) {
300       ierr = (*snes->ops->view)(snes,viewer);CHKERRQ(ierr);
301     }
302   } else if (isdraw) {
303     PetscDraw draw;
304     char      str[36];
305     PetscReal x,y,bottom,h;
306 
307     ierr   = PetscViewerDrawGetDraw(viewer,0,&draw);CHKERRQ(ierr);
308     ierr   = PetscDrawGetCurrentPoint(draw,&x,&y);CHKERRQ(ierr);
309     ierr   = PetscStrcpy(str,"SNES: ");CHKERRQ(ierr);
310     ierr   = PetscStrcat(str,((PetscObject)snes)->type_name);CHKERRQ(ierr);
311     ierr   = PetscDrawBoxedString(draw,x,y,PETSC_DRAW_BLUE,PETSC_DRAW_BLACK,str,NULL,&h);CHKERRQ(ierr);
312     bottom = y - h;
313     ierr   = PetscDrawPushCurrentPoint(draw,x,bottom);CHKERRQ(ierr);
314     if (snes->ops->view) {
315       ierr = (*snes->ops->view)(snes,viewer);CHKERRQ(ierr);
316     }
317 #if defined(PETSC_HAVE_AMS)
318   } else if (isams) {
319     if (((PetscObject)snes)->amsmem == -1) {
320       ierr = PetscObjectViewAMS((PetscObject)snes,viewer);CHKERRQ(ierr);
321       PetscStackCallAMS(AMS_Memory_take_access,(((PetscObject)snes)->amsmem));
322       PetscStackCallAMS(AMS_Memory_add_field,(((PetscObject)snes)->amsmem,"its",&snes->iter,1,AMS_INT,AMS_READ,AMS_COMMON,AMS_REDUCT_UNDEF));
323       if (!snes->conv_hist) {
324         ierr = SNESSetConvergenceHistory(snes,NULL,NULL,PETSC_DECIDE,PETSC_FALSE);CHKERRQ(ierr);
325       }
326       PetscStackCallAMS(AMS_Memory_add_field,(((PetscObject)snes)->amsmem,"conv_hist",snes->conv_hist,10,AMS_DOUBLE,AMS_READ,AMS_COMMON,AMS_REDUCT_UNDEF));
327       PetscStackCallAMS(AMS_Memory_grant_access,(((PetscObject)snes)->amsmem));
328     }
329 #endif
330   }
331   if (snes->linesearch) {
332     ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
333     ierr = SNESGetLineSearch(snes, &linesearch);CHKERRQ(ierr);
334     ierr = SNESLineSearchView(linesearch, viewer);CHKERRQ(ierr);
335     ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
336   }
337   if (snes->pc && snes->usespc) {
338     ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
339     ierr = SNESView(snes->pc, viewer);CHKERRQ(ierr);
340     ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
341   }
342   ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
343   ierr = DMGetDMSNES(snes->dm,&dmsnes);CHKERRQ(ierr);
344   ierr = DMSNESView(dmsnes, viewer);CHKERRQ(ierr);
345   ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
346   if (snes->usesksp) {
347     ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
348     ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
349     ierr = KSPView(ksp,viewer);CHKERRQ(ierr);
350     ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
351   }
352   if (isdraw) {
353     PetscDraw draw;
354     ierr = PetscViewerDrawGetDraw(viewer,0,&draw);CHKERRQ(ierr);
355     ierr = PetscDrawPopCurrentPoint(draw);CHKERRQ(ierr);
356   }
357   PetscFunctionReturn(0);
358 }
359 
360 /*
361   We retain a list of functions that also take SNES command
362   line options. These are called at the end SNESSetFromOptions()
363 */
364 #define MAXSETFROMOPTIONS 5
365 static PetscInt numberofsetfromoptions;
366 static PetscErrorCode (*othersetfromoptions[MAXSETFROMOPTIONS])(SNES);
367 
368 #undef __FUNCT__
369 #define __FUNCT__ "SNESAddOptionsChecker"
370 /*@C
371   SNESAddOptionsChecker - Adds an additional function to check for SNES options.
372 
373   Not Collective
374 
375   Input Parameter:
376 . snescheck - function that checks for options
377 
378   Level: developer
379 
380 .seealso: SNESSetFromOptions()
381 @*/
382 PetscErrorCode  SNESAddOptionsChecker(PetscErrorCode (*snescheck)(SNES))
383 {
384   PetscFunctionBegin;
385   if (numberofsetfromoptions >= MAXSETFROMOPTIONS) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE, "Too many options checkers, only %D allowed", MAXSETFROMOPTIONS);
386   othersetfromoptions[numberofsetfromoptions++] = snescheck;
387   PetscFunctionReturn(0);
388 }
389 
390 extern PetscErrorCode  SNESDefaultMatrixFreeCreate2(SNES,Vec,Mat*);
391 
392 #undef __FUNCT__
393 #define __FUNCT__ "SNESSetUpMatrixFree_Private"
394 static PetscErrorCode SNESSetUpMatrixFree_Private(SNES snes, PetscBool hasOperator, PetscInt version)
395 {
396   Mat            J;
397   KSP            ksp;
398   PC             pc;
399   PetscBool      match;
400   PetscErrorCode ierr;
401 
402   PetscFunctionBegin;
403   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
404 
405   if (!snes->vec_func && (snes->jacobian || snes->jacobian_pre)) {
406     Mat A = snes->jacobian, B = snes->jacobian_pre;
407     ierr = MatGetVecs(A ? A : B, NULL,&snes->vec_func);CHKERRQ(ierr);
408   }
409 
410   if (version == 1) {
411     ierr = MatCreateSNESMF(snes,&J);CHKERRQ(ierr);
412     ierr = MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);CHKERRQ(ierr);
413     ierr = MatSetFromOptions(J);CHKERRQ(ierr);
414   } else if (version == 2) {
415     if (!snes->vec_func) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"SNESSetFunction() must be called first");
416 #if !defined(PETSC_USE_COMPLEX) && !defined(PETSC_USE_REAL_SINGLE) && !defined(PETSC_USE_REAL___FLOAT128)
417     ierr = SNESDefaultMatrixFreeCreate2(snes,snes->vec_func,&J);CHKERRQ(ierr);
418 #else
419     SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP, "matrix-free operator rutines (version 2)");
420 #endif
421   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE, "matrix-free operator rutines, only version 1 and 2");
422 
423   ierr = PetscInfo1(snes,"Setting default matrix-free operator routines (version %D)\n", version);CHKERRQ(ierr);
424   if (hasOperator) {
425 
426     /* This version replaces the user provided Jacobian matrix with a
427        matrix-free version but still employs the user-provided preconditioner matrix. */
428     ierr = SNESSetJacobian(snes,J,0,0,0);CHKERRQ(ierr);
429   } else {
430     /* This version replaces both the user-provided Jacobian and the user-
431      provided preconditioner Jacobian with the default matrix free version. */
432     if ((snes->pcside == PC_LEFT) && snes->pc) {
433       if (!snes->jacobian){ierr = SNESSetJacobian(snes,J,0,0,0);CHKERRQ(ierr);}
434     } else {
435       ierr = SNESSetJacobian(snes,J,J,MatMFFDComputeJacobian,0);CHKERRQ(ierr);
436     }
437     /* Force no preconditioner */
438     ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
439     ierr = KSPGetPC(ksp,&pc);CHKERRQ(ierr);
440     ierr = PetscObjectTypeCompare((PetscObject)pc,PCSHELL,&match);CHKERRQ(ierr);
441     if (!match) {
442       ierr = PetscInfo(snes,"Setting default matrix-free preconditioner routines\nThat is no preconditioner is being used\n");CHKERRQ(ierr);
443       ierr = PCSetType(pc,PCNONE);CHKERRQ(ierr);
444     }
445   }
446   ierr = MatDestroy(&J);CHKERRQ(ierr);
447   PetscFunctionReturn(0);
448 }
449 
450 #undef __FUNCT__
451 #define __FUNCT__ "DMRestrictHook_SNESVecSol"
452 static PetscErrorCode DMRestrictHook_SNESVecSol(DM dmfine,Mat Restrict,Vec Rscale,Mat Inject,DM dmcoarse,void *ctx)
453 {
454   SNES           snes = (SNES)ctx;
455   PetscErrorCode ierr;
456   Vec            Xfine,Xfine_named = NULL,Xcoarse;
457 
458   PetscFunctionBegin;
459   if (PetscLogPrintInfo) {
460     PetscInt finelevel,coarselevel,fineclevel,coarseclevel;
461     ierr = DMGetRefineLevel(dmfine,&finelevel);CHKERRQ(ierr);
462     ierr = DMGetCoarsenLevel(dmfine,&fineclevel);CHKERRQ(ierr);
463     ierr = DMGetRefineLevel(dmcoarse,&coarselevel);CHKERRQ(ierr);
464     ierr = DMGetCoarsenLevel(dmcoarse,&coarseclevel);CHKERRQ(ierr);
465     ierr = PetscInfo4(dmfine,"Restricting SNES solution vector from level %D-%D to level %D-%D\n",finelevel,fineclevel,coarselevel,coarseclevel);CHKERRQ(ierr);
466   }
467   if (dmfine == snes->dm) Xfine = snes->vec_sol;
468   else {
469     ierr  = DMGetNamedGlobalVector(dmfine,"SNESVecSol",&Xfine_named);CHKERRQ(ierr);
470     Xfine = Xfine_named;
471   }
472   ierr = DMGetNamedGlobalVector(dmcoarse,"SNESVecSol",&Xcoarse);CHKERRQ(ierr);
473   ierr = MatRestrict(Restrict,Xfine,Xcoarse);CHKERRQ(ierr);
474   ierr = VecPointwiseMult(Xcoarse,Xcoarse,Rscale);CHKERRQ(ierr);
475   ierr = DMRestoreNamedGlobalVector(dmcoarse,"SNESVecSol",&Xcoarse);CHKERRQ(ierr);
476   if (Xfine_named) {ierr = DMRestoreNamedGlobalVector(dmfine,"SNESVecSol",&Xfine_named);CHKERRQ(ierr);}
477   PetscFunctionReturn(0);
478 }
479 
480 #undef __FUNCT__
481 #define __FUNCT__ "DMCoarsenHook_SNESVecSol"
482 static PetscErrorCode DMCoarsenHook_SNESVecSol(DM dm,DM dmc,void *ctx)
483 {
484   PetscErrorCode ierr;
485 
486   PetscFunctionBegin;
487   ierr = DMCoarsenHookAdd(dmc,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,ctx);CHKERRQ(ierr);
488   PetscFunctionReturn(0);
489 }
490 
491 #undef __FUNCT__
492 #define __FUNCT__ "KSPComputeOperators_SNES"
493 /* This may be called to rediscretize the operator on levels of linear multigrid. The DM shuffle is so the user can
494  * safely call SNESGetDM() in their residual evaluation routine. */
495 static PetscErrorCode KSPComputeOperators_SNES(KSP ksp,Mat A,Mat B,MatStructure *mstruct,void *ctx)
496 {
497   SNES           snes = (SNES)ctx;
498   PetscErrorCode ierr;
499   Mat            Asave = A,Bsave = B;
500   Vec            X,Xnamed = NULL;
501   DM             dmsave;
502   void           *ctxsave;
503   PetscErrorCode (*jac)(SNES,Vec,Mat*,Mat*,MatStructure*,void*);
504 
505   PetscFunctionBegin;
506   dmsave = snes->dm;
507   ierr   = KSPGetDM(ksp,&snes->dm);CHKERRQ(ierr);
508   if (dmsave == snes->dm) X = snes->vec_sol; /* We are on the finest level */
509   else {                                     /* We are on a coarser level, this vec was initialized using a DM restrict hook */
510     ierr = DMGetNamedGlobalVector(snes->dm,"SNESVecSol",&Xnamed);CHKERRQ(ierr);
511     X    = Xnamed;
512     ierr = SNESGetJacobian(snes,NULL,NULL,&jac,&ctxsave);CHKERRQ(ierr);
513     /* If the DM's don't match up, the MatFDColoring context needed for the jacobian won't match up either -- fixit. */
514     if (jac == SNESComputeJacobianDefaultColor) {
515       ierr = SNESSetJacobian(snes,NULL,NULL,SNESComputeJacobianDefaultColor,0);CHKERRQ(ierr);
516     }
517   }
518   /* put the previous context back */
519 
520   ierr = SNESComputeJacobian(snes,X,&A,&B,mstruct);CHKERRQ(ierr);
521   if (snes->dm != dmsave && jac == SNESComputeJacobianDefaultColor) {
522     ierr = SNESSetJacobian(snes,NULL,NULL,jac,ctxsave);CHKERRQ(ierr);
523   }
524 
525   if (A != Asave || B != Bsave) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_SUP,"No support for changing matrices at this time");
526   if (Xnamed) {
527     ierr = DMRestoreNamedGlobalVector(snes->dm,"SNESVecSol",&Xnamed);CHKERRQ(ierr);
528   }
529   snes->dm = dmsave;
530   PetscFunctionReturn(0);
531 }
532 
533 #undef __FUNCT__
534 #define __FUNCT__ "SNESSetUpMatrices"
535 /*@
536    SNESSetUpMatrices - ensures that matrices are available for SNES, to be called by SNESSetUp_XXX()
537 
538    Collective
539 
540    Input Arguments:
541 .  snes - snes to configure
542 
543    Level: developer
544 
545 .seealso: SNESSetUp()
546 @*/
547 PetscErrorCode SNESSetUpMatrices(SNES snes)
548 {
549   PetscErrorCode ierr;
550   DM             dm;
551   DMSNES         sdm;
552 
553   PetscFunctionBegin;
554   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
555   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
556   if (!sdm->ops->computejacobian) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_PLIB,"DMSNES not properly configured");
557   else if (!snes->jacobian && snes->mf) {
558     Mat  J;
559     void *functx;
560     ierr = MatCreateSNESMF(snes,&J);CHKERRQ(ierr);
561     ierr = MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);CHKERRQ(ierr);
562     ierr = MatSetFromOptions(J);CHKERRQ(ierr);
563     ierr = SNESGetFunction(snes,NULL,NULL,&functx);CHKERRQ(ierr);
564     ierr = SNESSetJacobian(snes,J,J,0,0);CHKERRQ(ierr);
565     ierr = MatDestroy(&J);CHKERRQ(ierr);
566   } else if (snes->mf_operator && !snes->jacobian_pre && !snes->jacobian) {
567     Mat J,B;
568     ierr = MatCreateSNESMF(snes,&J);CHKERRQ(ierr);
569     ierr = MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);CHKERRQ(ierr);
570     ierr = MatSetFromOptions(J);CHKERRQ(ierr);
571     ierr = DMCreateMatrix(snes->dm,&B);CHKERRQ(ierr);
572     /* sdm->computejacobian was already set to reach here */
573     ierr = SNESSetJacobian(snes,J,B,NULL,NULL);CHKERRQ(ierr);
574     ierr = MatDestroy(&J);CHKERRQ(ierr);
575     ierr = MatDestroy(&B);CHKERRQ(ierr);
576   } else if (!snes->jacobian_pre) {
577     Mat J,B;
578     J    = snes->jacobian;
579     ierr = DMCreateMatrix(snes->dm,&B);CHKERRQ(ierr);
580     ierr = SNESSetJacobian(snes,J ? J : B,B,NULL,NULL);CHKERRQ(ierr);
581     ierr = MatDestroy(&B);CHKERRQ(ierr);
582   }
583   {
584     KSP ksp;
585     ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
586     ierr = KSPSetComputeOperators(ksp,KSPComputeOperators_SNES,snes);CHKERRQ(ierr);
587     ierr = DMCoarsenHookAdd(snes->dm,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,snes);CHKERRQ(ierr);
588   }
589   PetscFunctionReturn(0);
590 }
591 
592 #undef __FUNCT__
593 #define __FUNCT__ "SNESSetFromOptions"
594 /*@
595    SNESSetFromOptions - Sets various SNES and KSP parameters from user options.
596 
597    Collective on SNES
598 
599    Input Parameter:
600 .  snes - the SNES context
601 
602    Options Database Keys:
603 +  -snes_type <type> - ls, tr, ngmres, ncg, richardson, qn, vi, fas
604 .  -snes_stol - convergence tolerance in terms of the norm
605                 of the change in the solution between steps
606 .  -snes_atol <abstol> - absolute tolerance of residual norm
607 .  -snes_rtol <rtol> - relative decrease in tolerance norm from initial
608 .  -snes_max_it <max_it> - maximum number of iterations
609 .  -snes_max_funcs <max_funcs> - maximum number of function evaluations
610 .  -snes_max_fail <max_fail> - maximum number of line search failures allowed before stopping, default is none
611 .  -snes_max_linear_solve_fail - number of linear solver failures before SNESSolve() stops
612 .  -snes_lag_preconditioner <lag> - how often preconditioner is rebuilt (use -1 to never rebuild)
613 .  -snes_lag_jacobian <lag> - how often Jacobian is rebuilt (use -1 to never rebuild)
614 .  -snes_trtol <trtol> - trust region tolerance
615 .  -snes_no_convergence_test - skip convergence test in nonlinear
616                                solver; hence iterations will continue until max_it
617                                or some other criterion is reached. Saves expense
618                                of convergence test
619 .  -snes_monitor <optional filename> - prints residual norm at each iteration. if no
620                                        filename given prints to stdout
621 .  -snes_monitor_solution - plots solution at each iteration
622 .  -snes_monitor_residual - plots residual (not its norm) at each iteration
623 .  -snes_monitor_solution_update - plots update to solution at each iteration
624 .  -snes_monitor_lg_residualnorm - plots residual norm at each iteration
625 .  -snes_monitor_lg_range - plots residual norm at each iteration
626 .  -snes_fd - use finite differences to compute Jacobian; very slow, only for testing
627 .  -snes_fd_color - use finite differences with coloring to compute Jacobian
628 .  -snes_mf_ksp_monitor - if using matrix-free multiply then print h at each KSP iteration
629 -  -snes_converged_reason - print the reason for convergence/divergence after each solve
630 
631     Options Database for Eisenstat-Walker method:
632 +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
633 .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
634 .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
635 .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
636 .  -snes_ksp_ew_gamma <gamma> - Sets gamma
637 .  -snes_ksp_ew_alpha <alpha> - Sets alpha
638 .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
639 -  -snes_ksp_ew_threshold <threshold> - Sets threshold
640 
641    Notes:
642    To see all options, run your program with the -help option or consult
643    the <A href="../../docs/manual.pdf#nameddest=ch_snes">SNES chapter of the users manual</A>.
644 
645    Level: beginner
646 
647 .keywords: SNES, nonlinear, set, options, database
648 
649 .seealso: SNESSetOptionsPrefix()
650 @*/
651 PetscErrorCode  SNESSetFromOptions(SNES snes)
652 {
653   PetscBool      flg,pcset,persist;
654   PetscInt       i,indx,lag,grids;
655   MatStructure   matflag;
656   const char     *deft        = SNESNEWTONLS;
657   const char     *convtests[] = {"default","skip"};
658   SNESKSPEW      *kctx        = NULL;
659   char           type[256], monfilename[PETSC_MAX_PATH_LEN];
660   PetscViewer    monviewer;
661   PetscErrorCode ierr;
662   PCSide         pcside;
663   const char     *optionsprefix;
664 
665   PetscFunctionBegin;
666   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
667   if (!SNESRegisterAllCalled) {ierr = SNESRegisterAll();CHKERRQ(ierr);}
668   ierr = PetscObjectOptionsBegin((PetscObject)snes);CHKERRQ(ierr);
669   if (((PetscObject)snes)->type_name) deft = ((PetscObject)snes)->type_name;
670   ierr = PetscOptionsList("-snes_type","Nonlinear solver method","SNESSetType",SNESList,deft,type,256,&flg);CHKERRQ(ierr);
671   if (flg) {
672     ierr = SNESSetType(snes,type);CHKERRQ(ierr);
673   } else if (!((PetscObject)snes)->type_name) {
674     ierr = SNESSetType(snes,deft);CHKERRQ(ierr);
675   }
676   /* not used here, but called so will go into help messaage */
677   ierr = PetscOptionsName("-snes_view","Print detailed information on solver used","SNESView",0);CHKERRQ(ierr);
678 
679   ierr = PetscOptionsReal("-snes_stol","Stop if step length less than","SNESSetTolerances",snes->stol,&snes->stol,0);CHKERRQ(ierr);
680   ierr = PetscOptionsReal("-snes_atol","Stop if function norm less than","SNESSetTolerances",snes->abstol,&snes->abstol,0);CHKERRQ(ierr);
681 
682   ierr = PetscOptionsReal("-snes_rtol","Stop if decrease in function norm less than","SNESSetTolerances",snes->rtol,&snes->rtol,0);CHKERRQ(ierr);
683   ierr = PetscOptionsInt("-snes_max_it","Maximum iterations","SNESSetTolerances",snes->max_its,&snes->max_its,NULL);CHKERRQ(ierr);
684   ierr = PetscOptionsInt("-snes_max_funcs","Maximum function evaluations","SNESSetTolerances",snes->max_funcs,&snes->max_funcs,NULL);CHKERRQ(ierr);
685   ierr = PetscOptionsInt("-snes_max_fail","Maximum nonlinear step failures","SNESSetMaxNonlinearStepFailures",snes->maxFailures,&snes->maxFailures,NULL);CHKERRQ(ierr);
686   ierr = PetscOptionsInt("-snes_max_linear_solve_fail","Maximum failures in linear solves allowed","SNESSetMaxLinearSolveFailures",snes->maxLinearSolveFailures,&snes->maxLinearSolveFailures,NULL);CHKERRQ(ierr);
687   ierr = PetscOptionsBool("-snes_error_if_not_converged","Generate error if solver does not converge","SNESSetErrorIfNotConverged",snes->errorifnotconverged,&snes->errorifnotconverged,NULL);CHKERRQ(ierr);
688 
689   ierr = PetscOptionsInt("-snes_lag_preconditioner","How often to rebuild preconditioner","SNESSetLagPreconditioner",snes->lagpreconditioner,&lag,&flg);CHKERRQ(ierr);
690   if (flg) {
691     ierr = SNESSetLagPreconditioner(snes,lag);CHKERRQ(ierr);
692   }
693   ierr = PetscOptionsBool("-snes_lag_preconditioner_persists","Preconditioner lagging through multiple solves","SNESSetLagPreconditionerPersists",snes->lagjac_persist,&persist,&flg);CHKERRQ(ierr);
694   if (flg) {
695     ierr = SNESSetLagPreconditionerPersists(snes,persist);CHKERRQ(ierr);
696   }
697   ierr = PetscOptionsInt("-snes_lag_jacobian","How often to rebuild Jacobian","SNESSetLagJacobian",snes->lagjacobian,&lag,&flg);CHKERRQ(ierr);
698   if (flg) {
699     ierr = SNESSetLagJacobian(snes,lag);CHKERRQ(ierr);
700   }
701   ierr = PetscOptionsBool("-snes_lag_jacobian_persists","Jacobian lagging through multiple solves","SNESSetLagJacobianPersists",snes->lagjac_persist,&persist,&flg);CHKERRQ(ierr);
702   if (flg) {
703     ierr = SNESSetLagJacobianPersists(snes,persist);CHKERRQ(ierr);
704   }
705 
706   ierr = PetscOptionsInt("-snes_grid_sequence","Use grid sequencing to generate initial guess","SNESSetGridSequence",snes->gridsequence,&grids,&flg);CHKERRQ(ierr);
707   if (flg) {
708     ierr = SNESSetGridSequence(snes,grids);CHKERRQ(ierr);
709   }
710 
711   ierr = PetscOptionsEList("-snes_convergence_test","Convergence test","SNESSetConvergenceTest",convtests,2,"default",&indx,&flg);CHKERRQ(ierr);
712   if (flg) {
713     switch (indx) {
714     case 0: ierr = SNESSetConvergenceTest(snes,SNESConvergedDefault,NULL,NULL);CHKERRQ(ierr); break;
715     case 1: ierr = SNESSetConvergenceTest(snes,SNESConvergedSkip,NULL,NULL);CHKERRQ(ierr);    break;
716     }
717   }
718 
719   ierr = PetscOptionsBool("-snes_converged_reason","Print reason for converged or diverged","SNESSolve",snes->printreason,&snes->printreason,NULL);CHKERRQ(ierr);
720 
721   ierr = PetscOptionsEList("-snes_norm_schedule","SNES Norm schedule","SNESSetNormSchedule",SNESNormSchedules,5,"function",&indx,&flg);CHKERRQ(ierr);
722   if (flg) { ierr = SNESSetNormSchedule(snes,(SNESNormSchedule)indx);CHKERRQ(ierr); }
723 
724   ierr = PetscOptionsEList("-snes_function_type","SNES Norm schedule","SNESSetFunctionType",SNESFunctionTypes,2,"unpreconditioned",&indx,&flg);CHKERRQ(ierr);
725   if (flg) { ierr = SNESSetFunctionType(snes,(SNESFunctionType)indx);CHKERRQ(ierr); }
726 
727   kctx = (SNESKSPEW*)snes->kspconvctx;
728 
729   ierr = PetscOptionsBool("-snes_ksp_ew","Use Eisentat-Walker linear system convergence test","SNESKSPSetUseEW",snes->ksp_ewconv,&snes->ksp_ewconv,NULL);CHKERRQ(ierr);
730 
731   ierr = PetscOptionsInt("-snes_ksp_ew_version","Version 1, 2 or 3","SNESKSPSetParametersEW",kctx->version,&kctx->version,0);CHKERRQ(ierr);
732   ierr = PetscOptionsReal("-snes_ksp_ew_rtol0","0 <= rtol0 < 1","SNESKSPSetParametersEW",kctx->rtol_0,&kctx->rtol_0,0);CHKERRQ(ierr);
733   ierr = PetscOptionsReal("-snes_ksp_ew_rtolmax","0 <= rtolmax < 1","SNESKSPSetParametersEW",kctx->rtol_max,&kctx->rtol_max,0);CHKERRQ(ierr);
734   ierr = PetscOptionsReal("-snes_ksp_ew_gamma","0 <= gamma <= 1","SNESKSPSetParametersEW",kctx->gamma,&kctx->gamma,0);CHKERRQ(ierr);
735   ierr = PetscOptionsReal("-snes_ksp_ew_alpha","1 < alpha <= 2","SNESKSPSetParametersEW",kctx->alpha,&kctx->alpha,0);CHKERRQ(ierr);
736   ierr = PetscOptionsReal("-snes_ksp_ew_alpha2","alpha2","SNESKSPSetParametersEW",kctx->alpha2,&kctx->alpha2,0);CHKERRQ(ierr);
737   ierr = PetscOptionsReal("-snes_ksp_ew_threshold","0 < threshold < 1","SNESKSPSetParametersEW",kctx->threshold,&kctx->threshold,0);CHKERRQ(ierr);
738 
739   flg  = PETSC_FALSE;
740   ierr = PetscOptionsBool("-snes_check_jacobian","Check each Jacobian with a differenced one","SNESUpdateCheckJacobian",flg,&flg,NULL);CHKERRQ(ierr);
741   if (flg) {
742     ierr = SNESSetUpdate(snes,SNESUpdateCheckJacobian);CHKERRQ(ierr);
743   }
744 
745   flg  = PETSC_FALSE;
746   ierr = PetscOptionsBool("-snes_monitor_cancel","Remove all monitors","SNESMonitorCancel",flg,&flg,NULL);CHKERRQ(ierr);
747   if (flg) {ierr = SNESMonitorCancel(snes);CHKERRQ(ierr);}
748 
749   ierr = PetscOptionsString("-snes_monitor","Monitor norm of function","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
750   if (flg) {
751     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
752     ierr = SNESMonitorSet(snes,SNESMonitorDefault,monviewer,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
753   }
754 
755   ierr = PetscOptionsString("-snes_monitor_range","Monitor range of elements of function","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
756   if (flg) {
757     ierr = SNESMonitorSet(snes,SNESMonitorRange,0,0);CHKERRQ(ierr);
758   }
759 
760   ierr = PetscOptionsString("-snes_ratiomonitor","Monitor ratios of norms of function","SNESMonitorSetRatio","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
761   if (flg) {
762     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
763     ierr = SNESMonitorSetRatio(snes,monviewer);CHKERRQ(ierr);
764   }
765 
766   ierr = PetscOptionsString("-snes_monitor_short","Monitor norm of function (fewer digits)","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
767   if (flg) {
768     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
769     ierr = SNESMonitorSet(snes,SNESMonitorDefaultShort,monviewer,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
770   }
771 
772   ierr = PetscOptionsString("-snes_monitor_python","Use Python function","SNESMonitorSet",0,monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
773   if (flg) {ierr = PetscPythonMonitorSet((PetscObject)snes,monfilename);CHKERRQ(ierr);}
774 
775   flg  = PETSC_FALSE;
776   ierr = PetscOptionsBool("-snes_monitor_solution","Plot solution at each iteration","SNESMonitorSolution",flg,&flg,NULL);CHKERRQ(ierr);
777   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorSolution,0,0);CHKERRQ(ierr);}
778   flg  = PETSC_FALSE;
779   ierr = PetscOptionsBool("-snes_monitor_solution_update","Plot correction at each iteration","SNESMonitorSolutionUpdate",flg,&flg,NULL);CHKERRQ(ierr);
780   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorSolutionUpdate,0,0);CHKERRQ(ierr);}
781   flg  = PETSC_FALSE;
782   ierr = PetscOptionsBool("-snes_monitor_residual","Plot residual at each iteration","SNESMonitorResidual",flg,&flg,NULL);CHKERRQ(ierr);
783   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorResidual,0,0);CHKERRQ(ierr);}
784   flg  = PETSC_FALSE;
785   ierr = PetscOptionsBool("-snes_monitor_lg_residualnorm","Plot function norm at each iteration","SNESMonitorLGResidualNorm",flg,&flg,NULL);CHKERRQ(ierr);
786   if (flg) {
787     PetscDrawLG ctx;
788 
789     ierr = SNESMonitorLGCreate(0,0,PETSC_DECIDE,PETSC_DECIDE,300,300,&ctx);CHKERRQ(ierr);
790     ierr = SNESMonitorSet(snes,SNESMonitorLGResidualNorm,ctx,(PetscErrorCode (*)(void**))SNESMonitorLGDestroy);CHKERRQ(ierr);
791   }
792   flg  = PETSC_FALSE;
793   ierr = PetscOptionsBool("-snes_monitor_lg_range","Plot function range at each iteration","SNESMonitorLGRange",flg,&flg,NULL);CHKERRQ(ierr);
794   if (flg) {
795     PetscViewer ctx;
796 
797     ierr = PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),0,0,PETSC_DECIDE,PETSC_DECIDE,300,300,&ctx);CHKERRQ(ierr);
798     ierr = SNESMonitorSet(snes,SNESMonitorLGRange,ctx,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
799   }
800 
801   flg  = PETSC_FALSE;
802   ierr = PetscOptionsBool("-snes_monitor_jacupdate_spectrum","Print the change in the spectrum of the Jacobian","SNESMonitorJacUpdateSpectrum",flg,&flg,NULL);CHKERRQ(ierr);
803   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorJacUpdateSpectrum,0,0);CHKERRQ(ierr);}
804 
805   flg  = PETSC_FALSE;
806   ierr = PetscOptionsBool("-snes_fd","Use finite differences (slow) to compute Jacobian","SNESComputeJacobianDefault",flg,&flg,NULL);CHKERRQ(ierr);
807   if (flg) {
808     void *functx;
809     ierr = SNESGetFunction(snes,NULL,NULL,&functx);CHKERRQ(ierr);
810     ierr = SNESSetJacobian(snes,snes->jacobian,snes->jacobian_pre,SNESComputeJacobianDefault,functx);CHKERRQ(ierr);
811     ierr = PetscInfo(snes,"Setting default finite difference Jacobian matrix\n");CHKERRQ(ierr);
812   }
813 
814   flg  = PETSC_FALSE;
815   ierr = PetscOptionsBool("-snes_fd_function","Use finite differences (slow) to compute function from user objective","SNESObjectiveComputeFunctionDefaultFD",flg,&flg,NULL);CHKERRQ(ierr);
816   if (flg) {
817     ierr = SNESSetFunction(snes,NULL,SNESObjectiveComputeFunctionDefaultFD,NULL);CHKERRQ(ierr);
818   }
819 
820   flg  = PETSC_FALSE;
821   ierr = PetscOptionsBool("-snes_fd_color","Use finite differences with coloring to compute Jacobian","SNESComputeJacobianDefaultColor",flg,&flg,NULL);CHKERRQ(ierr);
822   if (flg) {
823     DM             dm;
824     DMSNES         sdm;
825     ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
826     ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
827     sdm->jacobianctx = NULL;
828     ierr = SNESSetJacobian(snes,snes->jacobian,snes->jacobian_pre,SNESComputeJacobianDefaultColor,0);CHKERRQ(ierr);
829     ierr = PetscInfo(snes,"Setting default finite difference coloring Jacobian matrix\n");CHKERRQ(ierr);
830   }
831 
832   flg  = PETSC_FALSE;
833   ierr = PetscOptionsBool("-snes_mf_operator","Use a Matrix-Free Jacobian with user-provided preconditioner matrix","MatCreateSNESMF",PETSC_FALSE,&snes->mf_operator,&flg);CHKERRQ(ierr);
834   if (flg && snes->mf_operator) {
835     snes->mf_operator = PETSC_TRUE;
836     snes->mf          = PETSC_TRUE;
837   }
838   flg  = PETSC_FALSE;
839   ierr = PetscOptionsBool("-snes_mf","Use a Matrix-Free Jacobian with no preconditioner matrix","MatCreateSNESMF",PETSC_FALSE,&snes->mf,&flg);CHKERRQ(ierr);
840   if (!flg && snes->mf_operator) snes->mf = PETSC_TRUE;
841   ierr = PetscOptionsInt("-snes_mf_version","Matrix-Free routines version 1 or 2","None",snes->mf_version,&snes->mf_version,0);CHKERRQ(ierr);
842 
843   flg  = PETSC_FALSE;
844   ierr = SNESGetPCSide(snes,&pcside);CHKERRQ(ierr);
845   ierr = PetscOptionsEnum("-snes_npc_side","SNES nonlinear preconditioner side","SNESSetPCSide",PCSides,(PetscEnum)pcside,(PetscEnum*)&pcside,&flg);CHKERRQ(ierr);
846   if (flg) {ierr = SNESSetPCSide(snes,pcside);CHKERRQ(ierr);}
847 
848 #if defined(PETSC_HAVE_AMS)
849   {
850   PetscBool set;
851   flg  = PETSC_FALSE;
852   ierr = PetscOptionsBool("-snes_ams_block","Block for AMS memory snooper at end of SNESSolve","PetscObjectAMSBlock",((PetscObject)snes)->amspublishblock,&flg,&set);CHKERRQ(ierr);
853   if (set) {
854     ierr = PetscObjectAMSSetBlock((PetscObject)snes,flg);CHKERRQ(ierr);
855   }
856   }
857 #endif
858 
859   for (i = 0; i < numberofsetfromoptions; i++) {
860     ierr = (*othersetfromoptions[i])(snes);CHKERRQ(ierr);
861   }
862 
863   if (snes->ops->setfromoptions) {
864     ierr = (*snes->ops->setfromoptions)(snes);CHKERRQ(ierr);
865   }
866 
867   /* process any options handlers added with PetscObjectAddOptionsHandler() */
868   ierr = PetscObjectProcessOptionsHandlers((PetscObject)snes);CHKERRQ(ierr);
869   ierr = PetscOptionsEnd();CHKERRQ(ierr);
870 
871   if (!snes->ksp) {ierr = SNESGetKSP(snes,&snes->ksp);CHKERRQ(ierr);}
872   ierr = KSPGetOperators(snes->ksp,NULL,NULL,&matflag);CHKERRQ(ierr);
873   ierr = KSPSetOperators(snes->ksp,snes->jacobian,snes->jacobian_pre,matflag);CHKERRQ(ierr);
874   ierr = KSPSetFromOptions(snes->ksp);CHKERRQ(ierr);
875 
876   if (!snes->linesearch) {
877     ierr = SNESGetLineSearch(snes, &snes->linesearch);CHKERRQ(ierr);
878   }
879   ierr = SNESLineSearchSetFromOptions(snes->linesearch);CHKERRQ(ierr);
880 
881   /* if someone has set the SNES PC type, create it. */
882   ierr = SNESGetOptionsPrefix(snes, &optionsprefix);CHKERRQ(ierr);
883   ierr = PetscOptionsHasName(optionsprefix, "-npc_snes_type", &pcset);CHKERRQ(ierr);
884   if (pcset && (!snes->pc)) {
885     ierr = SNESGetPC(snes, &snes->pc);CHKERRQ(ierr);
886   }
887   PetscFunctionReturn(0);
888 }
889 
890 #undef __FUNCT__
891 #define __FUNCT__ "SNESSetComputeApplicationContext"
892 /*@C
893    SNESSetComputeApplicationContext - Sets an optional function to compute a user-defined context for
894    the nonlinear solvers.
895 
896    Logically Collective on SNES
897 
898    Input Parameters:
899 +  snes - the SNES context
900 .  compute - function to compute the context
901 -  destroy - function to destroy the context
902 
903    Level: intermediate
904 
905    Notes:
906    This function is currently not available from Fortran.
907 
908 .keywords: SNES, nonlinear, set, application, context
909 
910 .seealso: SNESGetApplicationContext(), SNESSetComputeApplicationContext(), SNESGetApplicationContext()
911 @*/
912 PetscErrorCode  SNESSetComputeApplicationContext(SNES snes,PetscErrorCode (*compute)(SNES,void**),PetscErrorCode (*destroy)(void**))
913 {
914   PetscFunctionBegin;
915   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
916   snes->ops->usercompute = compute;
917   snes->ops->userdestroy = destroy;
918   PetscFunctionReturn(0);
919 }
920 
921 #undef __FUNCT__
922 #define __FUNCT__ "SNESSetApplicationContext"
923 /*@
924    SNESSetApplicationContext - Sets the optional user-defined context for
925    the nonlinear solvers.
926 
927    Logically Collective on SNES
928 
929    Input Parameters:
930 +  snes - the SNES context
931 -  usrP - optional user context
932 
933    Level: intermediate
934 
935 .keywords: SNES, nonlinear, set, application, context
936 
937 .seealso: SNESGetApplicationContext()
938 @*/
939 PetscErrorCode  SNESSetApplicationContext(SNES snes,void *usrP)
940 {
941   PetscErrorCode ierr;
942   KSP            ksp;
943 
944   PetscFunctionBegin;
945   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
946   ierr       = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
947   ierr       = KSPSetApplicationContext(ksp,usrP);CHKERRQ(ierr);
948   snes->user = usrP;
949   PetscFunctionReturn(0);
950 }
951 
952 #undef __FUNCT__
953 #define __FUNCT__ "SNESGetApplicationContext"
954 /*@
955    SNESGetApplicationContext - Gets the user-defined context for the
956    nonlinear solvers.
957 
958    Not Collective
959 
960    Input Parameter:
961 .  snes - SNES context
962 
963    Output Parameter:
964 .  usrP - user context
965 
966    Level: intermediate
967 
968 .keywords: SNES, nonlinear, get, application, context
969 
970 .seealso: SNESSetApplicationContext()
971 @*/
972 PetscErrorCode  SNESGetApplicationContext(SNES snes,void *usrP)
973 {
974   PetscFunctionBegin;
975   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
976   *(void**)usrP = snes->user;
977   PetscFunctionReturn(0);
978 }
979 
980 #undef __FUNCT__
981 #define __FUNCT__ "SNESGetIterationNumber"
982 /*@
983    SNESGetIterationNumber - Gets the number of nonlinear iterations completed
984    at this time.
985 
986    Not Collective
987 
988    Input Parameter:
989 .  snes - SNES context
990 
991    Output Parameter:
992 .  iter - iteration number
993 
994    Notes:
995    For example, during the computation of iteration 2 this would return 1.
996 
997    This is useful for using lagged Jacobians (where one does not recompute the
998    Jacobian at each SNES iteration). For example, the code
999 .vb
1000       ierr = SNESGetIterationNumber(snes,&it);
1001       if (!(it % 2)) {
1002         [compute Jacobian here]
1003       }
1004 .ve
1005    can be used in your ComputeJacobian() function to cause the Jacobian to be
1006    recomputed every second SNES iteration.
1007 
1008    Level: intermediate
1009 
1010 .keywords: SNES, nonlinear, get, iteration, number,
1011 
1012 .seealso:   SNESGetFunctionNorm(), SNESGetLinearSolveIterations()
1013 @*/
1014 PetscErrorCode  SNESGetIterationNumber(SNES snes,PetscInt *iter)
1015 {
1016   PetscFunctionBegin;
1017   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1018   PetscValidIntPointer(iter,2);
1019   *iter = snes->iter;
1020   PetscFunctionReturn(0);
1021 }
1022 
1023 #undef __FUNCT__
1024 #define __FUNCT__ "SNESSetIterationNumber"
1025 /*@
1026    SNESSetIterationNumber - Sets the current iteration number.
1027 
1028    Not Collective
1029 
1030    Input Parameter:
1031 .  snes - SNES context
1032 .  iter - iteration number
1033 
1034    Level: developer
1035 
1036 .keywords: SNES, nonlinear, set, iteration, number,
1037 
1038 .seealso:   SNESGetFunctionNorm(), SNESGetLinearSolveIterations()
1039 @*/
1040 PetscErrorCode  SNESSetIterationNumber(SNES snes,PetscInt iter)
1041 {
1042   PetscErrorCode ierr;
1043 
1044   PetscFunctionBegin;
1045   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1046   ierr       = PetscObjectAMSTakeAccess((PetscObject)snes);CHKERRQ(ierr);
1047   snes->iter = iter;
1048   ierr       = PetscObjectAMSGrantAccess((PetscObject)snes);CHKERRQ(ierr);
1049   PetscFunctionReturn(0);
1050 }
1051 
1052 #undef __FUNCT__
1053 #define __FUNCT__ "SNESGetFunctionNorm"
1054 /*@
1055    SNESGetFunctionNorm - Gets the norm of the current function that was set
1056    with SNESSSetFunction().
1057 
1058    Collective on SNES
1059 
1060    Input Parameter:
1061 .  snes - SNES context
1062 
1063    Output Parameter:
1064 .  fnorm - 2-norm of function
1065 
1066    Level: intermediate
1067 
1068 .keywords: SNES, nonlinear, get, function, norm
1069 
1070 .seealso: SNESGetFunction(), SNESGetIterationNumber(), SNESGetLinearSolveIterations()
1071 @*/
1072 PetscErrorCode  SNESGetFunctionNorm(SNES snes,PetscReal *fnorm)
1073 {
1074   PetscFunctionBegin;
1075   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1076   PetscValidScalarPointer(fnorm,2);
1077   *fnorm = snes->norm;
1078   PetscFunctionReturn(0);
1079 }
1080 
1081 
1082 #undef __FUNCT__
1083 #define __FUNCT__ "SNESSetFunctionNorm"
1084 /*@
1085    SNESSetFunctionNorm - Sets the 2-norm of the current function computed using VecNorm().
1086 
1087    Collective on SNES
1088 
1089    Input Parameter:
1090 .  snes - SNES context
1091 .  fnorm - 2-norm of function
1092 
1093    Level: developer
1094 
1095 .keywords: SNES, nonlinear, set, function, norm
1096 
1097 .seealso: SNESSetFunction(), SNESSetIterationNumber(), VecNorm().
1098 @*/
1099 PetscErrorCode  SNESSetFunctionNorm(SNES snes,PetscReal fnorm)
1100 {
1101 
1102   PetscErrorCode ierr;
1103 
1104   PetscFunctionBegin;
1105   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1106   ierr       = PetscObjectAMSTakeAccess((PetscObject)snes);CHKERRQ(ierr);
1107   snes->norm = fnorm;
1108   ierr       = PetscObjectAMSGrantAccess((PetscObject)snes);CHKERRQ(ierr);
1109   PetscFunctionReturn(0);
1110 }
1111 
1112 #undef __FUNCT__
1113 #define __FUNCT__ "SNESGetNonlinearStepFailures"
1114 /*@
1115    SNESGetNonlinearStepFailures - Gets the number of unsuccessful steps
1116    attempted by the nonlinear solver.
1117 
1118    Not Collective
1119 
1120    Input Parameter:
1121 .  snes - SNES context
1122 
1123    Output Parameter:
1124 .  nfails - number of unsuccessful steps attempted
1125 
1126    Notes:
1127    This counter is reset to zero for each successive call to SNESSolve().
1128 
1129    Level: intermediate
1130 
1131 .keywords: SNES, nonlinear, get, number, unsuccessful, steps
1132 
1133 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
1134           SNESSetMaxNonlinearStepFailures(), SNESGetMaxNonlinearStepFailures()
1135 @*/
1136 PetscErrorCode  SNESGetNonlinearStepFailures(SNES snes,PetscInt *nfails)
1137 {
1138   PetscFunctionBegin;
1139   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1140   PetscValidIntPointer(nfails,2);
1141   *nfails = snes->numFailures;
1142   PetscFunctionReturn(0);
1143 }
1144 
1145 #undef __FUNCT__
1146 #define __FUNCT__ "SNESSetMaxNonlinearStepFailures"
1147 /*@
1148    SNESSetMaxNonlinearStepFailures - Sets the maximum number of unsuccessful steps
1149    attempted by the nonlinear solver before it gives up.
1150 
1151    Not Collective
1152 
1153    Input Parameters:
1154 +  snes     - SNES context
1155 -  maxFails - maximum of unsuccessful steps
1156 
1157    Level: intermediate
1158 
1159 .keywords: SNES, nonlinear, set, maximum, unsuccessful, steps
1160 
1161 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
1162           SNESGetMaxNonlinearStepFailures(), SNESGetNonlinearStepFailures()
1163 @*/
1164 PetscErrorCode  SNESSetMaxNonlinearStepFailures(SNES snes, PetscInt maxFails)
1165 {
1166   PetscFunctionBegin;
1167   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1168   snes->maxFailures = maxFails;
1169   PetscFunctionReturn(0);
1170 }
1171 
1172 #undef __FUNCT__
1173 #define __FUNCT__ "SNESGetMaxNonlinearStepFailures"
1174 /*@
1175    SNESGetMaxNonlinearStepFailures - Gets the maximum number of unsuccessful steps
1176    attempted by the nonlinear solver before it gives up.
1177 
1178    Not Collective
1179 
1180    Input Parameter:
1181 .  snes     - SNES context
1182 
1183    Output Parameter:
1184 .  maxFails - maximum of unsuccessful steps
1185 
1186    Level: intermediate
1187 
1188 .keywords: SNES, nonlinear, get, maximum, unsuccessful, steps
1189 
1190 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
1191           SNESSetMaxNonlinearStepFailures(), SNESGetNonlinearStepFailures()
1192 
1193 @*/
1194 PetscErrorCode  SNESGetMaxNonlinearStepFailures(SNES snes, PetscInt *maxFails)
1195 {
1196   PetscFunctionBegin;
1197   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1198   PetscValidIntPointer(maxFails,2);
1199   *maxFails = snes->maxFailures;
1200   PetscFunctionReturn(0);
1201 }
1202 
1203 #undef __FUNCT__
1204 #define __FUNCT__ "SNESGetNumberFunctionEvals"
1205 /*@
1206    SNESGetNumberFunctionEvals - Gets the number of user provided function evaluations
1207      done by SNES.
1208 
1209    Not Collective
1210 
1211    Input Parameter:
1212 .  snes     - SNES context
1213 
1214    Output Parameter:
1215 .  nfuncs - number of evaluations
1216 
1217    Level: intermediate
1218 
1219    Notes: Reset every time SNESSolve is called unless SNESSetCountersReset() is used.
1220 
1221 .keywords: SNES, nonlinear, get, maximum, unsuccessful, steps
1222 
1223 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(), SNESSetCountersReset()
1224 @*/
1225 PetscErrorCode  SNESGetNumberFunctionEvals(SNES snes, PetscInt *nfuncs)
1226 {
1227   PetscFunctionBegin;
1228   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1229   PetscValidIntPointer(nfuncs,2);
1230   *nfuncs = snes->nfuncs;
1231   PetscFunctionReturn(0);
1232 }
1233 
1234 #undef __FUNCT__
1235 #define __FUNCT__ "SNESGetLinearSolveFailures"
1236 /*@
1237    SNESGetLinearSolveFailures - Gets the number of failed (non-converged)
1238    linear solvers.
1239 
1240    Not Collective
1241 
1242    Input Parameter:
1243 .  snes - SNES context
1244 
1245    Output Parameter:
1246 .  nfails - number of failed solves
1247 
1248    Notes:
1249    This counter is reset to zero for each successive call to SNESSolve().
1250 
1251    Level: intermediate
1252 
1253 .keywords: SNES, nonlinear, get, number, unsuccessful, steps
1254 
1255 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures()
1256 @*/
1257 PetscErrorCode  SNESGetLinearSolveFailures(SNES snes,PetscInt *nfails)
1258 {
1259   PetscFunctionBegin;
1260   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1261   PetscValidIntPointer(nfails,2);
1262   *nfails = snes->numLinearSolveFailures;
1263   PetscFunctionReturn(0);
1264 }
1265 
1266 #undef __FUNCT__
1267 #define __FUNCT__ "SNESSetMaxLinearSolveFailures"
1268 /*@
1269    SNESSetMaxLinearSolveFailures - the number of failed linear solve attempts
1270    allowed before SNES returns with a diverged reason of SNES_DIVERGED_LINEAR_SOLVE
1271 
1272    Logically Collective on SNES
1273 
1274    Input Parameters:
1275 +  snes     - SNES context
1276 -  maxFails - maximum allowed linear solve failures
1277 
1278    Level: intermediate
1279 
1280    Notes: By default this is 0; that is SNES returns on the first failed linear solve
1281 
1282 .keywords: SNES, nonlinear, set, maximum, unsuccessful, steps
1283 
1284 .seealso: SNESGetLinearSolveFailures(), SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations()
1285 @*/
1286 PetscErrorCode  SNESSetMaxLinearSolveFailures(SNES snes, PetscInt maxFails)
1287 {
1288   PetscFunctionBegin;
1289   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1290   PetscValidLogicalCollectiveInt(snes,maxFails,2);
1291   snes->maxLinearSolveFailures = maxFails;
1292   PetscFunctionReturn(0);
1293 }
1294 
1295 #undef __FUNCT__
1296 #define __FUNCT__ "SNESGetMaxLinearSolveFailures"
1297 /*@
1298    SNESGetMaxLinearSolveFailures - gets the maximum number of linear solve failures that
1299      are allowed before SNES terminates
1300 
1301    Not Collective
1302 
1303    Input Parameter:
1304 .  snes     - SNES context
1305 
1306    Output Parameter:
1307 .  maxFails - maximum of unsuccessful solves allowed
1308 
1309    Level: intermediate
1310 
1311    Notes: By default this is 1; that is SNES returns on the first failed linear solve
1312 
1313 .keywords: SNES, nonlinear, get, maximum, unsuccessful, steps
1314 
1315 .seealso: SNESGetLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(),
1316 @*/
1317 PetscErrorCode  SNESGetMaxLinearSolveFailures(SNES snes, PetscInt *maxFails)
1318 {
1319   PetscFunctionBegin;
1320   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1321   PetscValidIntPointer(maxFails,2);
1322   *maxFails = snes->maxLinearSolveFailures;
1323   PetscFunctionReturn(0);
1324 }
1325 
1326 #undef __FUNCT__
1327 #define __FUNCT__ "SNESGetLinearSolveIterations"
1328 /*@
1329    SNESGetLinearSolveIterations - Gets the total number of linear iterations
1330    used by the nonlinear solver.
1331 
1332    Not Collective
1333 
1334    Input Parameter:
1335 .  snes - SNES context
1336 
1337    Output Parameter:
1338 .  lits - number of linear iterations
1339 
1340    Notes:
1341    This counter is reset to zero for each successive call to SNESSolve() unless SNESSetCountersReset() is used.
1342 
1343    Level: intermediate
1344 
1345 .keywords: SNES, nonlinear, get, number, linear, iterations
1346 
1347 .seealso:  SNESGetIterationNumber(), SNESGetFunctionNorm(), SNESGetLinearSolveFailures(), SNESGetMaxLinearSolveFailures(), SNESSetCountersReset()
1348 @*/
1349 PetscErrorCode  SNESGetLinearSolveIterations(SNES snes,PetscInt *lits)
1350 {
1351   PetscFunctionBegin;
1352   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1353   PetscValidIntPointer(lits,2);
1354   *lits = snes->linear_its;
1355   PetscFunctionReturn(0);
1356 }
1357 
1358 #undef __FUNCT__
1359 #define __FUNCT__ "SNESSetCountersReset"
1360 /*@
1361    SNESSetCountersReset - Sets whether or not the counters for linear iterations and function evaluations
1362    are reset every time SNESSolve() is called.
1363 
1364    Logically Collective on SNES
1365 
1366    Input Parameter:
1367 +  snes - SNES context
1368 -  reset - whether to reset the counters or not
1369 
1370    Notes:
1371    This is automatically called with FALSE
1372 
1373    Level: developer
1374 
1375 .keywords: SNES, nonlinear, set, reset, number, linear, iterations
1376 
1377 .seealso:  SNESGetNumberFunctionEvals(), SNESGetNumberLinearSolveIterations(), SNESGetPC()
1378 @*/
1379 PetscErrorCode  SNESSetCountersReset(SNES snes,PetscBool reset)
1380 {
1381   PetscFunctionBegin;
1382   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1383   PetscValidLogicalCollectiveBool(snes,reset,2);
1384   snes->counters_reset = reset;
1385   PetscFunctionReturn(0);
1386 }
1387 
1388 
1389 #undef __FUNCT__
1390 #define __FUNCT__ "SNESSetKSP"
1391 /*@
1392    SNESSetKSP - Sets a KSP context for the SNES object to use
1393 
1394    Not Collective, but the SNES and KSP objects must live on the same MPI_Comm
1395 
1396    Input Parameters:
1397 +  snes - the SNES context
1398 -  ksp - the KSP context
1399 
1400    Notes:
1401    The SNES object already has its KSP object, you can obtain with SNESGetKSP()
1402    so this routine is rarely needed.
1403 
1404    The KSP object that is already in the SNES object has its reference count
1405    decreased by one.
1406 
1407    Level: developer
1408 
1409 .keywords: SNES, nonlinear, get, KSP, context
1410 
1411 .seealso: KSPGetPC(), SNESCreate(), KSPCreate(), SNESSetKSP()
1412 @*/
1413 PetscErrorCode  SNESSetKSP(SNES snes,KSP ksp)
1414 {
1415   PetscErrorCode ierr;
1416 
1417   PetscFunctionBegin;
1418   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1419   PetscValidHeaderSpecific(ksp,KSP_CLASSID,2);
1420   PetscCheckSameComm(snes,1,ksp,2);
1421   ierr = PetscObjectReference((PetscObject)ksp);CHKERRQ(ierr);
1422   if (snes->ksp) {ierr = PetscObjectDereference((PetscObject)snes->ksp);CHKERRQ(ierr);}
1423   snes->ksp = ksp;
1424   PetscFunctionReturn(0);
1425 }
1426 
1427 /* -----------------------------------------------------------*/
1428 #undef __FUNCT__
1429 #define __FUNCT__ "SNESCreate"
1430 /*@
1431    SNESCreate - Creates a nonlinear solver context.
1432 
1433    Collective on MPI_Comm
1434 
1435    Input Parameters:
1436 .  comm - MPI communicator
1437 
1438    Output Parameter:
1439 .  outsnes - the new SNES context
1440 
1441    Options Database Keys:
1442 +   -snes_mf - Activates default matrix-free Jacobian-vector products,
1443                and no preconditioning matrix
1444 .   -snes_mf_operator - Activates default matrix-free Jacobian-vector
1445                products, and a user-provided preconditioning matrix
1446                as set by SNESSetJacobian()
1447 -   -snes_fd - Uses (slow!) finite differences to compute Jacobian
1448 
1449    Level: beginner
1450 
1451 .keywords: SNES, nonlinear, create, context
1452 
1453 .seealso: SNESSolve(), SNESDestroy(), SNES, SNESSetLagPreconditioner()
1454 
1455 @*/
1456 PetscErrorCode  SNESCreate(MPI_Comm comm,SNES *outsnes)
1457 {
1458   PetscErrorCode ierr;
1459   SNES           snes;
1460   SNESKSPEW      *kctx;
1461 
1462   PetscFunctionBegin;
1463   PetscValidPointer(outsnes,2);
1464   *outsnes = NULL;
1465   ierr = SNESInitializePackage();CHKERRQ(ierr);
1466 
1467   ierr = PetscHeaderCreate(snes,_p_SNES,struct _SNESOps,SNES_CLASSID,"SNES","Nonlinear solver","SNES",comm,SNESDestroy,SNESView);CHKERRQ(ierr);
1468 
1469   snes->ops->converged    = SNESConvergedDefault;
1470   snes->usesksp           = PETSC_TRUE;
1471   snes->tolerancesset     = PETSC_FALSE;
1472   snes->max_its           = 50;
1473   snes->max_funcs         = 10000;
1474   snes->norm              = 0.0;
1475   snes->normschedule      = SNES_NORM_ALWAYS;
1476   snes->functype          = SNES_FUNCTION_DEFAULT;
1477   snes->rtol              = 1.e-8;
1478   snes->ttol              = 0.0;
1479   snes->abstol            = 1.e-50;
1480   snes->stol              = 1.e-8;
1481   snes->deltatol          = 1.e-12;
1482   snes->nfuncs            = 0;
1483   snes->numFailures       = 0;
1484   snes->maxFailures       = 1;
1485   snes->linear_its        = 0;
1486   snes->lagjacobian       = 1;
1487   snes->jac_iter          = 0;
1488   snes->lagjac_persist    = PETSC_FALSE;
1489   snes->lagpreconditioner = 1;
1490   snes->pre_iter          = 0;
1491   snes->lagpre_persist    = PETSC_FALSE;
1492   snes->numbermonitors    = 0;
1493   snes->data              = 0;
1494   snes->setupcalled       = PETSC_FALSE;
1495   snes->ksp_ewconv        = PETSC_FALSE;
1496   snes->nwork             = 0;
1497   snes->work              = 0;
1498   snes->nvwork            = 0;
1499   snes->vwork             = 0;
1500   snes->conv_hist_len     = 0;
1501   snes->conv_hist_max     = 0;
1502   snes->conv_hist         = NULL;
1503   snes->conv_hist_its     = NULL;
1504   snes->conv_hist_reset   = PETSC_TRUE;
1505   snes->counters_reset    = PETSC_TRUE;
1506   snes->vec_func_init_set = PETSC_FALSE;
1507   snes->reason            = SNES_CONVERGED_ITERATING;
1508   snes->pcside            = PC_RIGHT;
1509 
1510   snes->mf          = PETSC_FALSE;
1511   snes->mf_operator = PETSC_FALSE;
1512   snes->mf_version  = 1;
1513 
1514   snes->numLinearSolveFailures = 0;
1515   snes->maxLinearSolveFailures = 1;
1516 
1517   /* Create context to compute Eisenstat-Walker relative tolerance for KSP */
1518   ierr = PetscNewLog(snes,SNESKSPEW,&kctx);CHKERRQ(ierr);
1519 
1520   snes->kspconvctx  = (void*)kctx;
1521   kctx->version     = 2;
1522   kctx->rtol_0      = .3; /* Eisenstat and Walker suggest rtol_0=.5, but
1523                              this was too large for some test cases */
1524   kctx->rtol_last   = 0.0;
1525   kctx->rtol_max    = .9;
1526   kctx->gamma       = 1.0;
1527   kctx->alpha       = .5*(1.0 + PetscSqrtReal(5.0));
1528   kctx->alpha2      = kctx->alpha;
1529   kctx->threshold   = .1;
1530   kctx->lresid_last = 0.0;
1531   kctx->norm_last   = 0.0;
1532 
1533   *outsnes = snes;
1534   PetscFunctionReturn(0);
1535 }
1536 
1537 /*MC
1538     SNESFunction - functional form used to convey the nonlinear function to be solved by SNES
1539 
1540      Synopsis:
1541      #include "petscsnes.h"
1542      SNESFunction(SNES snes,Vec x,Vec f,void *ctx);
1543 
1544      Input Parameters:
1545 +     snes - the SNES context
1546 .     x    - state at which to evaluate residual
1547 -     ctx     - optional user-defined function context, passed in with SNESSetFunction()
1548 
1549      Output Parameter:
1550 .     f  - vector to put residual (function value)
1551 
1552    Level: intermediate
1553 
1554 .seealso:   SNESSetFunction(), SNESGetFunction()
1555 M*/
1556 
1557 #undef __FUNCT__
1558 #define __FUNCT__ "SNESSetFunction"
1559 /*@C
1560    SNESSetFunction - Sets the function evaluation routine and function
1561    vector for use by the SNES routines in solving systems of nonlinear
1562    equations.
1563 
1564    Logically Collective on SNES
1565 
1566    Input Parameters:
1567 +  snes - the SNES context
1568 .  r - vector to store function value
1569 .  SNESFunction - function evaluation routine
1570 -  ctx - [optional] user-defined context for private data for the
1571          function evaluation routine (may be NULL)
1572 
1573    Notes:
1574    The Newton-like methods typically solve linear systems of the form
1575 $      f'(x) x = -f(x),
1576    where f'(x) denotes the Jacobian matrix and f(x) is the function.
1577 
1578    Level: beginner
1579 
1580 .keywords: SNES, nonlinear, set, function
1581 
1582 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetPicard(), SNESFunction
1583 @*/
1584 PetscErrorCode  SNESSetFunction(SNES snes,Vec r,PetscErrorCode (*SNESFunction)(SNES,Vec,Vec,void*),void *ctx)
1585 {
1586   PetscErrorCode ierr;
1587   DM             dm;
1588 
1589   PetscFunctionBegin;
1590   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1591   if (r) {
1592     PetscValidHeaderSpecific(r,VEC_CLASSID,2);
1593     PetscCheckSameComm(snes,1,r,2);
1594     ierr = PetscObjectReference((PetscObject)r);CHKERRQ(ierr);
1595     ierr = VecDestroy(&snes->vec_func);CHKERRQ(ierr);
1596 
1597     snes->vec_func = r;
1598   }
1599   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1600   ierr = DMSNESSetFunction(dm,SNESFunction,ctx);CHKERRQ(ierr);
1601   PetscFunctionReturn(0);
1602 }
1603 
1604 
1605 #undef __FUNCT__
1606 #define __FUNCT__ "SNESSetInitialFunction"
1607 /*@C
1608    SNESSetInitialFunction - Sets the function vector to be used as the
1609    function norm at the initialization of the method.  In some
1610    instances, the user has precomputed the function before calling
1611    SNESSolve.  This function allows one to avoid a redundant call
1612    to SNESComputeFunction in that case.
1613 
1614    Logically Collective on SNES
1615 
1616    Input Parameters:
1617 +  snes - the SNES context
1618 -  f - vector to store function value
1619 
1620    Notes:
1621    This should not be modified during the solution procedure.
1622 
1623    This is used extensively in the SNESFAS hierarchy and in nonlinear preconditioning.
1624 
1625    Level: developer
1626 
1627 .keywords: SNES, nonlinear, set, function
1628 
1629 .seealso: SNESSetFunction(), SNESComputeFunction(), SNESSetInitialFunctionNorm()
1630 @*/
1631 PetscErrorCode  SNESSetInitialFunction(SNES snes, Vec f)
1632 {
1633   PetscErrorCode ierr;
1634   Vec            vec_func;
1635 
1636   PetscFunctionBegin;
1637   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1638   PetscValidHeaderSpecific(f,VEC_CLASSID,2);
1639   PetscCheckSameComm(snes,1,f,2);
1640   if (snes->pcside == PC_LEFT && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
1641     snes->vec_func_init_set = PETSC_FALSE;
1642     PetscFunctionReturn(0);
1643   }
1644   ierr = SNESGetFunction(snes,&vec_func,NULL,NULL);CHKERRQ(ierr);
1645   ierr = VecCopy(f, vec_func);CHKERRQ(ierr);
1646 
1647   snes->vec_func_init_set = PETSC_TRUE;
1648   PetscFunctionReturn(0);
1649 }
1650 
1651 #undef __FUNCT__
1652 #define __FUNCT__ "SNESSetNormSchedule"
1653 /*@
1654    SNESSetNormSchedule - Sets the SNESNormSchedule used in covergence and monitoring
1655    of the SNES method.
1656 
1657    Logically Collective on SNES
1658 
1659    Input Parameters:
1660 +  snes - the SNES context
1661 -  normschedule - the frequency of norm computation
1662 
1663    Notes:
1664    Only certain SNES methods support certain SNESNormSchedules.  Most require evaluation
1665    of the nonlinear function and the taking of its norm at every iteration to
1666    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
1667    (SNESGS) and the like do not require the norm of the function to be computed, and therfore
1668    may either be monitored for convergence or not.  As these are often used as nonlinear
1669    preconditioners, monitoring the norm of their error is not a useful enterprise within
1670    their solution.
1671 
1672    Level: developer
1673 
1674 .keywords: SNES, nonlinear, set, function, norm, type
1675 
1676 .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1677 @*/
1678 PetscErrorCode  SNESSetNormSchedule(SNES snes, SNESNormSchedule normschedule)
1679 {
1680   PetscFunctionBegin;
1681   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1682   snes->normschedule = normschedule;
1683   PetscFunctionReturn(0);
1684 }
1685 
1686 
1687 #undef __FUNCT__
1688 #define __FUNCT__ "SNESGetNormSchedule"
1689 /*@
1690    SNESGetNormSchedule - Gets the SNESNormSchedule used in covergence and monitoring
1691    of the SNES method.
1692 
1693    Logically Collective on SNES
1694 
1695    Input Parameters:
1696 +  snes - the SNES context
1697 -  normschedule - the type of the norm used
1698 
1699    Level: advanced
1700 
1701 .keywords: SNES, nonlinear, set, function, norm, type
1702 
1703 .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1704 @*/
1705 PetscErrorCode  SNESGetNormSchedule(SNES snes, SNESNormSchedule *normschedule)
1706 {
1707   PetscFunctionBegin;
1708   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1709   *normschedule = snes->normschedule;
1710   PetscFunctionReturn(0);
1711 }
1712 
1713 
1714 #undef __FUNCT__
1715 #define __FUNCT__ "SNESSetFunctionType"
1716 /*@C
1717    SNESSetFunctionType - Sets the SNESNormSchedule used in covergence and monitoring
1718    of the SNES method.
1719 
1720    Logically Collective on SNES
1721 
1722    Input Parameters:
1723 +  snes - the SNES context
1724 -  normschedule - the frequency of norm computation
1725 
1726    Notes:
1727    Only certain SNES methods support certain SNESNormSchedules.  Most require evaluation
1728    of the nonlinear function and the taking of its norm at every iteration to
1729    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
1730    (SNESGS) and the like do not require the norm of the function to be computed, and therfore
1731    may either be monitored for convergence or not.  As these are often used as nonlinear
1732    preconditioners, monitoring the norm of their error is not a useful enterprise within
1733    their solution.
1734 
1735    Level: developer
1736 
1737 .keywords: SNES, nonlinear, set, function, norm, type
1738 
1739 .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1740 @*/
1741 PetscErrorCode  SNESSetFunctionType(SNES snes, SNESFunctionType type)
1742 {
1743   PetscFunctionBegin;
1744   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1745   snes->functype = type;
1746   PetscFunctionReturn(0);
1747 }
1748 
1749 
1750 #undef __FUNCT__
1751 #define __FUNCT__ "SNESGetFunctionType"
1752 /*@C
1753    SNESGetFunctionType - Gets the SNESNormSchedule used in covergence and monitoring
1754    of the SNES method.
1755 
1756    Logically Collective on SNES
1757 
1758    Input Parameters:
1759 +  snes - the SNES context
1760 -  normschedule - the type of the norm used
1761 
1762    Level: advanced
1763 
1764 .keywords: SNES, nonlinear, set, function, norm, type
1765 
1766 .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1767 @*/
1768 PetscErrorCode  SNESGetFunctionType(SNES snes, SNESFunctionType *type)
1769 {
1770   PetscFunctionBegin;
1771   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1772   *type = snes->functype;
1773   PetscFunctionReturn(0);
1774 }
1775 
1776 /*MC
1777     SNESGSFunction - function used to convey a Gauss-Seidel sweep on the nonlinear function
1778 
1779      Synopsis:
1780      #include "petscsnes.h"
1781 $    SNESGSFunction(SNES snes,Vec x,Vec b,void *ctx);
1782 
1783 +  X   - solution vector
1784 .  B   - RHS vector
1785 -  ctx - optional user-defined Gauss-Seidel context
1786 
1787    Level: intermediate
1788 
1789 .seealso:   SNESSetGS(), SNESGetGS()
1790 M*/
1791 
1792 #undef __FUNCT__
1793 #define __FUNCT__ "SNESSetGS"
1794 /*@C
1795    SNESSetGS - Sets the user nonlinear Gauss-Seidel routine for
1796    use with composed nonlinear solvers.
1797 
1798    Input Parameters:
1799 +  snes   - the SNES context
1800 .  SNESGSFunction - function evaluation routine
1801 -  ctx    - [optional] user-defined context for private data for the
1802             smoother evaluation routine (may be NULL)
1803 
1804    Notes:
1805    The GS routines are used by the composed nonlinear solver to generate
1806     a problem appropriate update to the solution, particularly FAS.
1807 
1808    Level: intermediate
1809 
1810 .keywords: SNES, nonlinear, set, Gauss-Seidel
1811 
1812 .seealso: SNESGetFunction(), SNESComputeGS()
1813 @*/
1814 PetscErrorCode SNESSetGS(SNES snes,PetscErrorCode (*SNESGSFunction)(SNES,Vec,Vec,void*),void *ctx)
1815 {
1816   PetscErrorCode ierr;
1817   DM             dm;
1818 
1819   PetscFunctionBegin;
1820   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1821   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1822   ierr = DMSNESSetGS(dm,SNESGSFunction,ctx);CHKERRQ(ierr);
1823   PetscFunctionReturn(0);
1824 }
1825 
1826 #undef __FUNCT__
1827 #define __FUNCT__ "SNESPicardComputeFunction"
1828 PETSC_EXTERN PetscErrorCode SNESPicardComputeFunction(SNES snes,Vec x,Vec f,void *ctx)
1829 {
1830   PetscErrorCode ierr;
1831   DM             dm;
1832   DMSNES         sdm;
1833 
1834   PetscFunctionBegin;
1835   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1836   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
1837   /*  A(x)*x - b(x) */
1838   if (sdm->ops->computepfunction) {
1839     ierr = (*sdm->ops->computepfunction)(snes,x,f,sdm->pctx);CHKERRQ(ierr);
1840   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetPicard() to provide Picard function.");
1841 
1842   if (sdm->ops->computepjacobian) {
1843     ierr = (*sdm->ops->computepjacobian)(snes,x,&snes->jacobian,&snes->jacobian_pre,&snes->matstruct,sdm->pctx);CHKERRQ(ierr);
1844   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetPicard() to provide Picard matrix.");
1845   ierr = VecScale(f,-1.0);CHKERRQ(ierr);
1846   ierr = MatMultAdd(snes->jacobian,x,f,f);CHKERRQ(ierr);
1847   PetscFunctionReturn(0);
1848 }
1849 
1850 #undef __FUNCT__
1851 #define __FUNCT__ "SNESPicardComputeJacobian"
1852 PETSC_EXTERN PetscErrorCode SNESPicardComputeJacobian(SNES snes,Vec x1,Mat *J,Mat *B,MatStructure *flag,void *ctx)
1853 {
1854   PetscFunctionBegin;
1855   /* the jacobian matrix should be pre-filled in SNESPicardComputeFunction */
1856   *flag = snes->matstruct;
1857   PetscFunctionReturn(0);
1858 }
1859 
1860 #undef __FUNCT__
1861 #define __FUNCT__ "SNESSetPicard"
1862 /*@C
1863    SNESSetPicard - Use SNES to solve the semilinear-system A(x) x = b(x) via a Picard type iteration (Picard linearization)
1864 
1865    Logically Collective on SNES
1866 
1867    Input Parameters:
1868 +  snes - the SNES context
1869 .  r - vector to store function value
1870 .  SNESFunction - function evaluation routine
1871 .  Amat - matrix with which A(x) x - b(x) is to be computed
1872 .  Pmat - matrix from which preconditioner is computed (usually the same as Amat)
1873 .  SNESJacobianFunction  - function to compute matrix value
1874 -  ctx - [optional] user-defined context for private data for the
1875          function evaluation routine (may be NULL)
1876 
1877    Notes:
1878     We do not recomemend using this routine. It is far better to provide the nonlinear function F() and some approximation to the Jacobian and use
1879     an approximate Newton solver. This interface is provided to allow porting/testing a previous Picard based code in PETSc before converting it to approximate Newton.
1880 
1881     One can call SNESSetPicard() or SNESSetFunction() (and possibly SNESSetJacobian()) but cannot call both
1882 
1883 $     Solves the equation A(x) x = b(x) via the defect correction algorithm A(x^{n}) (x^{n+1} - x^{n}) = b(x^{n}) - A(x^{n})x^{n}
1884 $     Note that when an exact solver is used this corresponds to the "classic" Picard A(x^{n}) x^{n+1} = b(x^{n}) iteration.
1885 
1886      Run with -snes_mf_operator to solve the system with Newton's method using A(x^{n}) to construct the preconditioner.
1887 
1888    We implement the defect correction form of the Picard iteration because it converges much more generally when inexact linear solvers are used then
1889    the direct Picard iteration A(x^n) x^{n+1} = b(x^n)
1890 
1891    There is some controversity over the definition of a Picard iteration for nonlinear systems but almost everyone agrees that it involves a linear solve and some
1892    believe it is the iteration  A(x^{n}) x^{n+1} = b(x^{n}) hence we use the name Picard. If anyone has an authoritative  reference that defines the Picard iteration
1893    different please contact us at petsc-dev@mcs.anl.gov and we'll have an entirely new argument :-).
1894 
1895    Level: intermediate
1896 
1897 .keywords: SNES, nonlinear, set, function
1898 
1899 .seealso: SNESGetFunction(), SNESSetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESGetPicard(), SNESLineSearchPreCheckPicard()
1900 @*/
1901 PetscErrorCode  SNESSetPicard(SNES snes,Vec r,PetscErrorCode (*SNESFunction)(SNES,Vec,Vec,void*),Mat Amat, Mat Pmat, PetscErrorCode (*SNESJacobianFunction)(SNES,Vec,Mat*,Mat*,MatStructure*,void*),void *ctx)
1902 {
1903   PetscErrorCode ierr;
1904   DM             dm;
1905 
1906   PetscFunctionBegin;
1907   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1908   ierr = SNESGetDM(snes, &dm);CHKERRQ(ierr);
1909   ierr = DMSNESSetPicard(dm,SNESFunction,SNESJacobianFunction,ctx);CHKERRQ(ierr);
1910   ierr = SNESSetFunction(snes,r,SNESPicardComputeFunction,ctx);CHKERRQ(ierr);
1911   ierr = SNESSetJacobian(snes,Amat,Pmat,SNESPicardComputeJacobian,ctx);CHKERRQ(ierr);
1912   PetscFunctionReturn(0);
1913 }
1914 
1915 #undef __FUNCT__
1916 #define __FUNCT__ "SNESGetPicard"
1917 /*@C
1918    SNESGetPicard - Returns the context for the Picard iteration
1919 
1920    Not Collective, but Vec is parallel if SNES is parallel. Collective if Vec is requested, but has not been created yet.
1921 
1922    Input Parameter:
1923 .  snes - the SNES context
1924 
1925    Output Parameter:
1926 +  r - the function (or NULL)
1927 .  SNESFunction - the function (or NULL)
1928 .  Amat - the matrix used to defined the operation A(x) x - b(x) (or NULL)
1929 .  Pmat  - the matrix from which the preconditioner will be constructed (or NULL)
1930 .  SNESJacobianFunction - the function for matrix evaluation (or NULL)
1931 -  ctx - the function context (or NULL)
1932 
1933    Level: advanced
1934 
1935 .keywords: SNES, nonlinear, get, function
1936 
1937 .seealso: SNESSetPicard(), SNESGetFunction(), SNESGetJacobian(), SNESGetDM(), SNESFunction, SNESJacobianFunction
1938 @*/
1939 PetscErrorCode  SNESGetPicard(SNES snes,Vec *r,PetscErrorCode (**SNESFunction)(SNES,Vec,Vec,void*),Mat *Amat, Mat *Pmat, PetscErrorCode (**SNESJacobianFunction)(SNES,Vec,Mat*,Mat*,MatStructure*,void*),void **ctx)
1940 {
1941   PetscErrorCode ierr;
1942   DM             dm;
1943 
1944   PetscFunctionBegin;
1945   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1946   ierr = SNESGetFunction(snes,r,NULL,NULL);CHKERRQ(ierr);
1947   ierr = SNESGetJacobian(snes,Amat,Pmat,NULL,NULL);CHKERRQ(ierr);
1948   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1949   ierr = DMSNESGetPicard(dm,SNESFunction,SNESJacobianFunction,ctx);CHKERRQ(ierr);
1950   PetscFunctionReturn(0);
1951 }
1952 
1953 #undef __FUNCT__
1954 #define __FUNCT__ "SNESSetComputeInitialGuess"
1955 /*@C
1956    SNESSetComputeInitialGuess - Sets a routine used to compute an initial guess for the problem
1957 
1958    Logically Collective on SNES
1959 
1960    Input Parameters:
1961 +  snes - the SNES context
1962 .  func - function evaluation routine
1963 -  ctx - [optional] user-defined context for private data for the
1964          function evaluation routine (may be NULL)
1965 
1966    Calling sequence of func:
1967 $    func (SNES snes,Vec x,void *ctx);
1968 
1969 .  f - function vector
1970 -  ctx - optional user-defined function context
1971 
1972    Level: intermediate
1973 
1974 .keywords: SNES, nonlinear, set, function
1975 
1976 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian()
1977 @*/
1978 PetscErrorCode  SNESSetComputeInitialGuess(SNES snes,PetscErrorCode (*func)(SNES,Vec,void*),void *ctx)
1979 {
1980   PetscFunctionBegin;
1981   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1982   if (func) snes->ops->computeinitialguess = func;
1983   if (ctx)  snes->initialguessP            = ctx;
1984   PetscFunctionReturn(0);
1985 }
1986 
1987 /* --------------------------------------------------------------- */
1988 #undef __FUNCT__
1989 #define __FUNCT__ "SNESGetRhs"
1990 /*@C
1991    SNESGetRhs - Gets the vector for solving F(x) = rhs. If rhs is not set
1992    it assumes a zero right hand side.
1993 
1994    Logically Collective on SNES
1995 
1996    Input Parameter:
1997 .  snes - the SNES context
1998 
1999    Output Parameter:
2000 .  rhs - the right hand side vector or NULL if the right hand side vector is null
2001 
2002    Level: intermediate
2003 
2004 .keywords: SNES, nonlinear, get, function, right hand side
2005 
2006 .seealso: SNESGetSolution(), SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction()
2007 @*/
2008 PetscErrorCode  SNESGetRhs(SNES snes,Vec *rhs)
2009 {
2010   PetscFunctionBegin;
2011   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2012   PetscValidPointer(rhs,2);
2013   *rhs = snes->vec_rhs;
2014   PetscFunctionReturn(0);
2015 }
2016 
2017 #undef __FUNCT__
2018 #define __FUNCT__ "SNESComputeFunction"
2019 /*@
2020    SNESComputeFunction - Calls the function that has been set with SNESSetFunction().
2021 
2022    Collective on SNES
2023 
2024    Input Parameters:
2025 +  snes - the SNES context
2026 -  x - input vector
2027 
2028    Output Parameter:
2029 .  y - function vector, as set by SNESSetFunction()
2030 
2031    Notes:
2032    SNESComputeFunction() is typically used within nonlinear solvers
2033    implementations, so most users would not generally call this routine
2034    themselves.
2035 
2036    Level: developer
2037 
2038 .keywords: SNES, nonlinear, compute, function
2039 
2040 .seealso: SNESSetFunction(), SNESGetFunction()
2041 @*/
2042 PetscErrorCode  SNESComputeFunction(SNES snes,Vec x,Vec y)
2043 {
2044   PetscErrorCode ierr;
2045   DM             dm;
2046   DMSNES         sdm;
2047 
2048   PetscFunctionBegin;
2049   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2050   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
2051   PetscValidHeaderSpecific(y,VEC_CLASSID,3);
2052   PetscCheckSameComm(snes,1,x,2);
2053   PetscCheckSameComm(snes,1,y,3);
2054   ierr = VecValidValues(x,2,PETSC_TRUE);CHKERRQ(ierr);
2055 
2056   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2057   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2058   if (sdm->ops->computefunction) {
2059     ierr = PetscLogEventBegin(SNES_FunctionEval,snes,x,y,0);CHKERRQ(ierr);
2060     PetscStackPush("SNES user function");
2061     ierr = (*sdm->ops->computefunction)(snes,x,y,sdm->functionctx);CHKERRQ(ierr);
2062     PetscStackPop;
2063     ierr = PetscLogEventEnd(SNES_FunctionEval,snes,x,y,0);CHKERRQ(ierr);
2064   } else if (snes->vec_rhs) {
2065     ierr = MatMult(snes->jacobian, x, y);CHKERRQ(ierr);
2066   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetFunction() or SNESSetDM() before SNESComputeFunction(), likely called from SNESSolve().");
2067   if (snes->vec_rhs) {
2068     ierr = VecAXPY(y,-1.0,snes->vec_rhs);CHKERRQ(ierr);
2069   }
2070   snes->nfuncs++;
2071   ierr = VecValidValues(y,3,PETSC_FALSE);CHKERRQ(ierr);
2072   PetscFunctionReturn(0);
2073 }
2074 
2075 #undef __FUNCT__
2076 #define __FUNCT__ "SNESComputeGS"
2077 /*@
2078    SNESComputeGS - Calls the Gauss-Seidel function that has been set with  SNESSetGS().
2079 
2080    Collective on SNES
2081 
2082    Input Parameters:
2083 +  snes - the SNES context
2084 .  x - input vector
2085 -  b - rhs vector
2086 
2087    Output Parameter:
2088 .  x - new solution vector
2089 
2090    Notes:
2091    SNESComputeGS() is typically used within composed nonlinear solver
2092    implementations, so most users would not generally call this routine
2093    themselves.
2094 
2095    Level: developer
2096 
2097 .keywords: SNES, nonlinear, compute, function
2098 
2099 .seealso: SNESSetGS(), SNESComputeFunction()
2100 @*/
2101 PetscErrorCode  SNESComputeGS(SNES snes,Vec b,Vec x)
2102 {
2103   PetscErrorCode ierr;
2104   DM             dm;
2105   DMSNES         sdm;
2106 
2107   PetscFunctionBegin;
2108   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2109   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
2110   if (b) PetscValidHeaderSpecific(b,VEC_CLASSID,3);
2111   PetscCheckSameComm(snes,1,x,2);
2112   if (b) PetscCheckSameComm(snes,1,b,3);
2113   if (b) {ierr = VecValidValues(b,2,PETSC_TRUE);CHKERRQ(ierr);}
2114   ierr = PetscLogEventBegin(SNES_GSEval,snes,x,b,0);CHKERRQ(ierr);
2115   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2116   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2117   if (sdm->ops->computegs) {
2118     PetscStackPush("SNES user GS");
2119     ierr = (*sdm->ops->computegs)(snes,x,b,sdm->gsctx);CHKERRQ(ierr);
2120     PetscStackPop;
2121   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetGS() before SNESComputeGS(), likely called from SNESSolve().");
2122   ierr = PetscLogEventEnd(SNES_GSEval,snes,x,b,0);CHKERRQ(ierr);
2123   ierr = VecValidValues(x,3,PETSC_FALSE);CHKERRQ(ierr);
2124   PetscFunctionReturn(0);
2125 }
2126 
2127 #undef __FUNCT__
2128 #define __FUNCT__ "SNESComputeJacobian"
2129 /*@
2130    SNESComputeJacobian - Computes the Jacobian matrix that has been set with SNESSetJacobian().
2131 
2132    Collective on SNES and Mat
2133 
2134    Input Parameters:
2135 +  snes - the SNES context
2136 -  x - input vector
2137 
2138    Output Parameters:
2139 +  A - Jacobian matrix
2140 .  B - optional preconditioning matrix
2141 -  flag - flag indicating matrix structure (one of, SAME_NONZERO_PATTERN,DIFFERENT_NONZERO_PATTERN,SAME_PRECONDITIONER)
2142 
2143   Options Database Keys:
2144 +    -snes_lag_preconditioner <lag>
2145 .    -snes_lag_jacobian <lag>
2146 .    -snes_compare_explicit - Compare the computed Jacobian to the finite difference Jacobian and output the differences
2147 .    -snes_compare_explicit_draw  - Compare the computed Jacobian to the finite difference Jacobian and draw the result
2148 .    -snes_compare_explicit_contour  - Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
2149 .    -snes_compare_operator  - Make the comparison options above use the operator instead of the preconditioning matrix
2150 .    -snes_compare_coloring - Compute the finite differece Jacobian using coloring and display norms of difference
2151 .    -snes_compare_coloring_display - Compute the finite differece Jacobian using coloring and display verbose differences
2152 .    -snes_compare_coloring_threshold - Display only those matrix entries that differ by more than a given threshold
2153 .    -snes_compare_coloring_threshold_atol - Absolute tolerance for difference in matrix entries to be displayed by -snes_compare_coloring_threshold
2154 .    -snes_compare_coloring_threshold_rtol - Relative tolerance for difference in matrix entries to be displayed by -snes_compare_coloring_threshold
2155 .    -snes_compare_coloring_draw - Compute the finite differece Jacobian using coloring and draw differences
2156 -    -snes_compare_coloring_draw_contour - Compute the finite differece Jacobian using coloring and show contours of matrices and differences
2157 
2158 
2159    Notes:
2160    Most users should not need to explicitly call this routine, as it
2161    is used internally within the nonlinear solvers.
2162 
2163    See KSPSetOperators() for important information about setting the
2164    flag parameter.
2165 
2166    Level: developer
2167 
2168 .keywords: SNES, compute, Jacobian, matrix
2169 
2170 .seealso:  SNESSetJacobian(), KSPSetOperators(), MatStructure, SNESSetLagPreconditioner(), SNESSetLagJacobian()
2171 @*/
2172 PetscErrorCode  SNESComputeJacobian(SNES snes,Vec X,Mat *A,Mat *B,MatStructure *flg)
2173 {
2174   PetscErrorCode ierr;
2175   PetscBool      flag;
2176   DM             dm;
2177   DMSNES         sdm;
2178 
2179   PetscFunctionBegin;
2180   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2181   PetscValidHeaderSpecific(X,VEC_CLASSID,2);
2182   PetscValidPointer(flg,5);
2183   PetscCheckSameComm(snes,1,X,2);
2184   ierr = VecValidValues(X,2,PETSC_TRUE);CHKERRQ(ierr);
2185   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2186   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2187 
2188   if (!sdm->ops->computejacobian) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_USER,"Must call SNESSetJacobian(), DMSNESSetJacobian(), DMDASNESSetJacobianLocal(), etc");
2189 
2190   /* make sure that MatAssemblyBegin/End() is called on A matrix if it is matrix free */
2191 
2192   if (snes->lagjacobian == -2) {
2193     snes->lagjacobian = -1;
2194 
2195     ierr = PetscInfo(snes,"Recomputing Jacobian/preconditioner because lag is -2 (means compute Jacobian, but then never again) \n");CHKERRQ(ierr);
2196   } else if (snes->lagjacobian == -1) {
2197     *flg = SAME_PRECONDITIONER;
2198     ierr = PetscInfo(snes,"Reusing Jacobian/preconditioner because lag is -1\n");CHKERRQ(ierr);
2199     ierr = PetscObjectTypeCompare((PetscObject)*A,MATMFFD,&flag);CHKERRQ(ierr);
2200     if (flag) {
2201       ierr = MatAssemblyBegin(*A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2202       ierr = MatAssemblyEnd(*A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2203     }
2204     PetscFunctionReturn(0);
2205   } else if (snes->lagjacobian > 1 && (snes->iter + snes->jac_iter) % snes->lagjacobian) {
2206     *flg = SAME_PRECONDITIONER;
2207     ierr = PetscInfo2(snes,"Reusing Jacobian/preconditioner because lag is %D and SNES iteration is %D\n",snes->lagjacobian,snes->iter);CHKERRQ(ierr);
2208     ierr = PetscObjectTypeCompare((PetscObject)*A,MATMFFD,&flag);CHKERRQ(ierr);
2209     if (flag) {
2210       ierr = MatAssemblyBegin(*A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2211       ierr = MatAssemblyEnd(*A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2212     }
2213     PetscFunctionReturn(0);
2214   }
2215   if (snes->pc && snes->pcside == PC_LEFT) {
2216       ierr = MatAssemblyBegin(*A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2217       ierr = MatAssemblyEnd(*A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2218       PetscFunctionReturn(0);
2219   }
2220 
2221   *flg = DIFFERENT_NONZERO_PATTERN;
2222   ierr = PetscLogEventBegin(SNES_JacobianEval,snes,X,*A,*B);CHKERRQ(ierr);
2223 
2224   PetscStackPush("SNES user Jacobian function");
2225   ierr = (*sdm->ops->computejacobian)(snes,X,A,B,flg,sdm->jacobianctx);CHKERRQ(ierr);
2226   PetscStackPop;
2227 
2228   ierr = PetscLogEventEnd(SNES_JacobianEval,snes,X,*A,*B);CHKERRQ(ierr);
2229 
2230   if (snes->lagpreconditioner == -2) {
2231     ierr = PetscInfo(snes,"Rebuilding preconditioner exactly once since lag is -2\n");CHKERRQ(ierr);
2232 
2233     snes->lagpreconditioner = -1;
2234   } else if (snes->lagpreconditioner == -1) {
2235     *flg = SAME_PRECONDITIONER;
2236     ierr = PetscInfo(snes,"Reusing preconditioner because lag is -1\n");CHKERRQ(ierr);
2237   } else if (snes->lagpreconditioner > 1 && (snes->iter + snes->pre_iter) % snes->lagpreconditioner) {
2238     *flg = SAME_PRECONDITIONER;
2239     ierr = PetscInfo2(snes,"Reusing preconditioner because lag is %D and SNES iteration is %D\n",snes->lagpreconditioner,snes->iter);CHKERRQ(ierr);
2240   }
2241 
2242   /* make sure user returned a correct Jacobian and preconditioner */
2243   /* PetscValidHeaderSpecific(*A,MAT_CLASSID,3);
2244     PetscValidHeaderSpecific(*B,MAT_CLASSID,4);   */
2245   {
2246     PetscBool flag = PETSC_FALSE,flag_draw = PETSC_FALSE,flag_contour = PETSC_FALSE,flag_operator = PETSC_FALSE;
2247     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_explicit",&flag,NULL);CHKERRQ(ierr);
2248     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_explicit_draw",&flag_draw,NULL);CHKERRQ(ierr);
2249     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_explicit_draw_contour",&flag_contour,NULL);CHKERRQ(ierr);
2250     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_operator",&flag_operator,NULL);CHKERRQ(ierr);
2251     if (flag || flag_draw || flag_contour) {
2252       Mat          Bexp_mine = NULL,Bexp,FDexp;
2253       MatStructure mstruct;
2254       PetscViewer  vdraw,vstdout;
2255       PetscBool    flg;
2256       if (flag_operator) {
2257         ierr = MatComputeExplicitOperator(*A,&Bexp_mine);CHKERRQ(ierr);
2258         Bexp = Bexp_mine;
2259       } else {
2260         /* See if the preconditioning matrix can be viewed and added directly */
2261         ierr = PetscObjectTypeCompareAny((PetscObject)*B,&flg,MATSEQAIJ,MATMPIAIJ,MATSEQDENSE,MATMPIDENSE,MATSEQBAIJ,MATMPIBAIJ,MATSEQSBAIJ,MATMPIBAIJ,"");CHKERRQ(ierr);
2262         if (flg) Bexp = *B;
2263         else {
2264           /* If the "preconditioning" matrix is itself MATSHELL or some other type without direct support */
2265           ierr = MatComputeExplicitOperator(*B,&Bexp_mine);CHKERRQ(ierr);
2266           Bexp = Bexp_mine;
2267         }
2268       }
2269       ierr = MatConvert(Bexp,MATSAME,MAT_INITIAL_MATRIX,&FDexp);CHKERRQ(ierr);
2270       ierr = SNESComputeJacobianDefault(snes,X,&FDexp,&FDexp,&mstruct,NULL);CHKERRQ(ierr);
2271       ierr = PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&vstdout);CHKERRQ(ierr);
2272       if (flag_draw || flag_contour) {
2273         ierr = PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),0,"Explicit Jacobians",PETSC_DECIDE,PETSC_DECIDE,300,300,&vdraw);CHKERRQ(ierr);
2274         if (flag_contour) {ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);}
2275       } else vdraw = NULL;
2276       ierr = PetscViewerASCIIPrintf(vstdout,"Explicit %s\n",flag_operator ? "Jacobian" : "preconditioning Jacobian");CHKERRQ(ierr);
2277       if (flag) {ierr = MatView(Bexp,vstdout);CHKERRQ(ierr);}
2278       if (vdraw) {ierr = MatView(Bexp,vdraw);CHKERRQ(ierr);}
2279       ierr = PetscViewerASCIIPrintf(vstdout,"Finite difference Jacobian\n");CHKERRQ(ierr);
2280       if (flag) {ierr = MatView(FDexp,vstdout);CHKERRQ(ierr);}
2281       if (vdraw) {ierr = MatView(FDexp,vdraw);CHKERRQ(ierr);}
2282       ierr = MatAYPX(FDexp,-1.0,Bexp,SAME_NONZERO_PATTERN);CHKERRQ(ierr);
2283       ierr = PetscViewerASCIIPrintf(vstdout,"User-provided matrix minus finite difference Jacobian\n");CHKERRQ(ierr);
2284       if (flag) {ierr = MatView(FDexp,vstdout);CHKERRQ(ierr);}
2285       if (vdraw) {              /* Always use contour for the difference */
2286         ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);
2287         ierr = MatView(FDexp,vdraw);CHKERRQ(ierr);
2288         ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);
2289       }
2290       if (flag_contour) {ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);}
2291       ierr = PetscViewerDestroy(&vdraw);CHKERRQ(ierr);
2292       ierr = MatDestroy(&Bexp_mine);CHKERRQ(ierr);
2293       ierr = MatDestroy(&FDexp);CHKERRQ(ierr);
2294     }
2295   }
2296   {
2297     PetscBool flag = PETSC_FALSE,flag_display = PETSC_FALSE,flag_draw = PETSC_FALSE,flag_contour = PETSC_FALSE,flag_threshold = PETSC_FALSE;
2298     PetscReal threshold_atol = PETSC_SQRT_MACHINE_EPSILON,threshold_rtol = 10*PETSC_SQRT_MACHINE_EPSILON;
2299     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring",&flag,NULL);CHKERRQ(ierr);
2300     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_display",&flag_display,NULL);CHKERRQ(ierr);
2301     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_draw",&flag_draw,NULL);CHKERRQ(ierr);
2302     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_draw_contour",&flag_contour,NULL);CHKERRQ(ierr);
2303     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold",&flag_threshold,NULL);CHKERRQ(ierr);
2304     ierr = PetscOptionsGetReal(((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold_rtol",&threshold_rtol,NULL);CHKERRQ(ierr);
2305     ierr = PetscOptionsGetReal(((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold_atol",&threshold_atol,NULL);CHKERRQ(ierr);
2306     if (flag || flag_display || flag_draw || flag_contour || flag_threshold) {
2307       Mat            Bfd;
2308       MatStructure   mstruct;
2309       PetscViewer    vdraw,vstdout;
2310       MatColoring    coloring;
2311       ISColoring     iscoloring;
2312       MatFDColoring  matfdcoloring;
2313       PetscErrorCode (*func)(SNES,Vec,Vec,void*);
2314       void           *funcctx;
2315       PetscReal      norm1,norm2,normmax;
2316 
2317       ierr = MatDuplicate(*B,MAT_DO_NOT_COPY_VALUES,&Bfd);CHKERRQ(ierr);
2318       ierr = MatColoringCreate(Bfd,&coloring);CHKERRQ(ierr);
2319       ierr = MatColoringSetType(coloring,MATCOLORINGSL);CHKERRQ(ierr);
2320       ierr = MatColoringSetFromOptions(coloring);CHKERRQ(ierr);
2321       ierr = MatColoringApply(coloring,&iscoloring);CHKERRQ(ierr);
2322       ierr = MatColoringDestroy(&coloring);CHKERRQ(ierr);
2323       ierr = MatFDColoringCreate(Bfd,iscoloring,&matfdcoloring);CHKERRQ(ierr);
2324       ierr = ISColoringDestroy(&iscoloring);CHKERRQ(ierr);
2325 
2326       /* This method of getting the function is currently unreliable since it doesn't work for DM local functions. */
2327       ierr = SNESGetFunction(snes,NULL,&func,&funcctx);CHKERRQ(ierr);
2328       ierr = MatFDColoringSetFunction(matfdcoloring,(PetscErrorCode (*)(void))func,funcctx);CHKERRQ(ierr);
2329       ierr = PetscObjectSetOptionsPrefix((PetscObject)matfdcoloring,((PetscObject)snes)->prefix);CHKERRQ(ierr);
2330       ierr = PetscObjectAppendOptionsPrefix((PetscObject)matfdcoloring,"coloring_");CHKERRQ(ierr);
2331       ierr = MatFDColoringSetFromOptions(matfdcoloring);CHKERRQ(ierr);
2332       ierr = MatFDColoringApply(Bfd,matfdcoloring,X,&mstruct,snes);CHKERRQ(ierr);
2333       ierr = MatFDColoringDestroy(&matfdcoloring);CHKERRQ(ierr);
2334 
2335       ierr = PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&vstdout);CHKERRQ(ierr);
2336       if (flag_draw || flag_contour) {
2337         ierr = PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),0,"Colored Jacobians",PETSC_DECIDE,PETSC_DECIDE,300,300,&vdraw);CHKERRQ(ierr);
2338         if (flag_contour) {ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);}
2339       } else vdraw = NULL;
2340       ierr = PetscViewerASCIIPrintf(vstdout,"Explicit preconditioning Jacobian\n");CHKERRQ(ierr);
2341       if (flag_display) {ierr = MatView(*B,vstdout);CHKERRQ(ierr);}
2342       if (vdraw) {ierr = MatView(*B,vdraw);CHKERRQ(ierr);}
2343       ierr = PetscViewerASCIIPrintf(vstdout,"Colored Finite difference Jacobian\n");CHKERRQ(ierr);
2344       if (flag_display) {ierr = MatView(Bfd,vstdout);CHKERRQ(ierr);}
2345       if (vdraw) {ierr = MatView(Bfd,vdraw);CHKERRQ(ierr);}
2346       ierr = MatAYPX(Bfd,-1.0,*B,SAME_NONZERO_PATTERN);CHKERRQ(ierr);
2347       ierr = MatNorm(Bfd,NORM_1,&norm1);CHKERRQ(ierr);
2348       ierr = MatNorm(Bfd,NORM_FROBENIUS,&norm2);CHKERRQ(ierr);
2349       ierr = MatNorm(Bfd,NORM_MAX,&normmax);CHKERRQ(ierr);
2350       ierr = PetscViewerASCIIPrintf(vstdout,"User-provided matrix minus finite difference Jacobian, norm1=%G normFrob=%G normmax=%G\n",norm1,norm2,normmax);CHKERRQ(ierr);
2351       if (flag_display) {ierr = MatView(Bfd,vstdout);CHKERRQ(ierr);}
2352       if (vdraw) {              /* Always use contour for the difference */
2353         ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);
2354         ierr = MatView(Bfd,vdraw);CHKERRQ(ierr);
2355         ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);
2356       }
2357       if (flag_contour) {ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);}
2358 
2359       if (flag_threshold) {
2360         PetscInt bs,rstart,rend,i;
2361         ierr = MatGetBlockSize(*B,&bs);CHKERRQ(ierr);
2362         ierr = MatGetOwnershipRange(*B,&rstart,&rend);CHKERRQ(ierr);
2363         for (i=rstart; i<rend; i++) {
2364           const PetscScalar *ba,*ca;
2365           const PetscInt    *bj,*cj;
2366           PetscInt          bn,cn,j,maxentrycol = -1,maxdiffcol = -1,maxrdiffcol = -1;
2367           PetscReal         maxentry = 0,maxdiff = 0,maxrdiff = 0;
2368           ierr = MatGetRow(*B,i,&bn,&bj,&ba);CHKERRQ(ierr);
2369           ierr = MatGetRow(Bfd,i,&cn,&cj,&ca);CHKERRQ(ierr);
2370           if (bn != cn) SETERRQ(((PetscObject)*A)->comm,PETSC_ERR_PLIB,"Unexpected different nonzero pattern in -snes_compare_coloring_threshold");
2371           for (j=0; j<bn; j++) {
2372             PetscReal rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol*PetscAbsScalar(ba[j]));
2373             if (PetscAbsScalar(ba[j]) > PetscAbs(maxentry)) {
2374               maxentrycol = bj[j];
2375               maxentry    = PetscRealPart(ba[j]);
2376             }
2377             if (PetscAbsScalar(ca[j]) > PetscAbs(maxdiff)) {
2378               maxdiffcol = bj[j];
2379               maxdiff    = PetscRealPart(ca[j]);
2380             }
2381             if (rdiff > maxrdiff) {
2382               maxrdiffcol = bj[j];
2383               maxrdiff    = rdiff;
2384             }
2385           }
2386           if (maxrdiff > 1) {
2387             ierr = PetscViewerASCIIPrintf(vstdout,"row %D (maxentry=%G at %D, maxdiff=%G at %D, maxrdiff=%G at %D):",i,maxentry,maxentrycol,maxdiff,maxdiffcol,maxrdiff,maxrdiffcol);CHKERRQ(ierr);
2388             for (j=0; j<bn; j++) {
2389               PetscReal rdiff;
2390               rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol*PetscAbsScalar(ba[j]));
2391               if (rdiff > 1) {
2392                 ierr = PetscViewerASCIIPrintf(vstdout," (%D,%G:%G)",bj[j],PetscRealPart(ba[j]),PetscRealPart(ca[j]));CHKERRQ(ierr);
2393               }
2394             }
2395             ierr = PetscViewerASCIIPrintf(vstdout,"\n",i,maxentry,maxdiff,maxrdiff);CHKERRQ(ierr);
2396           }
2397           ierr = MatRestoreRow(*B,i,&bn,&bj,&ba);CHKERRQ(ierr);
2398           ierr = MatRestoreRow(Bfd,i,&cn,&cj,&ca);CHKERRQ(ierr);
2399         }
2400       }
2401       ierr = PetscViewerDestroy(&vdraw);CHKERRQ(ierr);
2402       ierr = MatDestroy(&Bfd);CHKERRQ(ierr);
2403     }
2404   }
2405   PetscFunctionReturn(0);
2406 }
2407 
2408 /*MC
2409     SNESJacobianFunction - function used to convey the nonlinear Jacobian of the function to be solved by SNES
2410 
2411      Synopsis:
2412      #include "petscsnes.h"
2413 $     SNESJacobianFunction(SNES snes,Vec x,Mat *Amat,Mat *Pmat,int *flag,void *ctx);
2414 
2415 +  x - input vector
2416 .  Amat - the matrix that defines the (approximate) Jacobian
2417 .  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.
2418 .  flag - flag indicating information about the preconditioner matrix
2419    structure (same as flag in KSPSetOperators()), one of SAME_NONZERO_PATTERN,DIFFERENT_NONZERO_PATTERN,SAME_PRECONDITIONER
2420 -  ctx - [optional] user-defined Jacobian context
2421 
2422    Level: intermediate
2423 
2424 .seealso:   SNESSetFunction(), SNESGetFunction(), SNESSetJacobian(), SNESGetJacobian()
2425 M*/
2426 
2427 #undef __FUNCT__
2428 #define __FUNCT__ "SNESSetJacobian"
2429 /*@C
2430    SNESSetJacobian - Sets the function to compute Jacobian as well as the
2431    location to store the matrix.
2432 
2433    Logically Collective on SNES and Mat
2434 
2435    Input Parameters:
2436 +  snes - the SNES context
2437 .  Amat - the matrix that defines the (approximate) Jacobian
2438 .  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.
2439 .  SNESJacobianFunction - Jacobian evaluation routine (if NULL then SNES retains any previously set value)
2440 -  ctx - [optional] user-defined context for private data for the
2441          Jacobian evaluation routine (may be NULL) (if NULL then SNES retains any previously set value)
2442 
2443    Notes:
2444    See KSPSetOperators() for important information about setting the flag
2445    output parameter in the routine func().  Be sure to read this information!
2446 
2447    The routine func() takes Mat * as the matrix arguments rather than Mat.
2448    This allows the Jacobian evaluation routine to replace A and/or B with a
2449    completely new new matrix structure (not just different matrix elements)
2450    when appropriate, for instance, if the nonzero structure is changing
2451    throughout the global iterations.
2452 
2453    If the Amat matrix and Pmat matrix are different you must call MatAssemblyBegin/End() on
2454    each matrix.
2455 
2456    If using SNESComputeJacobianDefaultColor() to assemble a Jacobian, the ctx argument
2457    must be a MatFDColoring.
2458 
2459    Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
2460    example is to use the "Picard linearization" which only differentiates through the highest order parts of each term.
2461 
2462    Level: beginner
2463 
2464 .keywords: SNES, nonlinear, set, Jacobian, matrix
2465 
2466 .seealso: KSPSetOperators(), SNESSetFunction(), MatMFFDComputeJacobian(), SNESComputeJacobianDefaultColor(), MatStructure, SNESJacobianFunction, SNESSetPicard()
2467 @*/
2468 PetscErrorCode  SNESSetJacobian(SNES snes,Mat Amat,Mat Pmat,PetscErrorCode (*SNESJacobianFunction)(SNES,Vec,Mat*,Mat*,MatStructure*,void*),void *ctx)
2469 {
2470   PetscErrorCode ierr;
2471   DM             dm;
2472 
2473   PetscFunctionBegin;
2474   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2475   if (Amat) PetscValidHeaderSpecific(Amat,MAT_CLASSID,2);
2476   if (Pmat) PetscValidHeaderSpecific(Pmat,MAT_CLASSID,3);
2477   if (Amat) PetscCheckSameComm(snes,1,Amat,2);
2478   if (Pmat) PetscCheckSameComm(snes,1,Pmat,3);
2479   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2480   ierr = DMSNESSetJacobian(dm,SNESJacobianFunction,ctx);CHKERRQ(ierr);
2481   if (Amat) {
2482     ierr = PetscObjectReference((PetscObject)Amat);CHKERRQ(ierr);
2483     ierr = MatDestroy(&snes->jacobian);CHKERRQ(ierr);
2484 
2485     snes->jacobian = Amat;
2486   }
2487   if (Pmat) {
2488     ierr = PetscObjectReference((PetscObject)Pmat);CHKERRQ(ierr);
2489     ierr = MatDestroy(&snes->jacobian_pre);CHKERRQ(ierr);
2490 
2491     snes->jacobian_pre = Pmat;
2492   }
2493   PetscFunctionReturn(0);
2494 }
2495 
2496 #undef __FUNCT__
2497 #define __FUNCT__ "SNESGetJacobian"
2498 /*@C
2499    SNESGetJacobian - Returns the Jacobian matrix and optionally the user
2500    provided context for evaluating the Jacobian.
2501 
2502    Not Collective, but Mat object will be parallel if SNES object is
2503 
2504    Input Parameter:
2505 .  snes - the nonlinear solver context
2506 
2507    Output Parameters:
2508 +  Amat - location to stash (approximate) Jacobian matrix (or NULL)
2509 .  Pmat - location to stash matrix used to compute the preconditioner (or NULL)
2510 .  SNESJacobianFunction - location to put Jacobian function (or NULL)
2511 -  ctx - location to stash Jacobian ctx (or NULL)
2512 
2513    Level: advanced
2514 
2515 .seealso: SNESSetJacobian(), SNESComputeJacobian()
2516 @*/
2517 PetscErrorCode SNESGetJacobian(SNES snes,Mat *Amat,Mat *Pmat,PetscErrorCode (**SNESJacobianFunction)(SNES,Vec,Mat*,Mat*,MatStructure*,void*),void **ctx)
2518 {
2519   PetscErrorCode ierr;
2520   DM             dm;
2521   DMSNES         sdm;
2522 
2523   PetscFunctionBegin;
2524   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2525   if (Amat) *Amat = snes->jacobian;
2526   if (Pmat) *Pmat = snes->jacobian_pre;
2527   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2528   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2529   if (SNESJacobianFunction) *SNESJacobianFunction = sdm->ops->computejacobian;
2530   if (ctx) *ctx = sdm->jacobianctx;
2531   PetscFunctionReturn(0);
2532 }
2533 
2534 #undef __FUNCT__
2535 #define __FUNCT__ "SNESSetUp"
2536 /*@
2537    SNESSetUp - Sets up the internal data structures for the later use
2538    of a nonlinear solver.
2539 
2540    Collective on SNES
2541 
2542    Input Parameters:
2543 .  snes - the SNES context
2544 
2545    Notes:
2546    For basic use of the SNES solvers the user need not explicitly call
2547    SNESSetUp(), since these actions will automatically occur during
2548    the call to SNESSolve().  However, if one wishes to control this
2549    phase separately, SNESSetUp() should be called after SNESCreate()
2550    and optional routines of the form SNESSetXXX(), but before SNESSolve().
2551 
2552    Level: advanced
2553 
2554 .keywords: SNES, nonlinear, setup
2555 
2556 .seealso: SNESCreate(), SNESSolve(), SNESDestroy()
2557 @*/
2558 PetscErrorCode  SNESSetUp(SNES snes)
2559 {
2560   PetscErrorCode ierr;
2561   DM             dm;
2562   DMSNES         sdm;
2563   SNESLineSearch linesearch, pclinesearch;
2564   void           *lsprectx,*lspostctx;
2565   PetscErrorCode (*precheck)(SNESLineSearch,Vec,Vec,PetscBool*,void*);
2566   PetscErrorCode (*postcheck)(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);
2567   PetscErrorCode (*func)(SNES,Vec,Vec,void*);
2568   Vec            f,fpc;
2569   void           *funcctx;
2570   PetscErrorCode (*jac)(SNES,Vec,Mat*,Mat*,MatStructure*,void*);
2571   void           *jacctx,*appctx;
2572 
2573   PetscFunctionBegin;
2574   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2575   if (snes->setupcalled) PetscFunctionReturn(0);
2576 
2577   if (!((PetscObject)snes)->type_name) {
2578     ierr = SNESSetType(snes,SNESNEWTONLS);CHKERRQ(ierr);
2579   }
2580 
2581   ierr = SNESGetFunction(snes,&snes->vec_func,NULL,NULL);CHKERRQ(ierr);
2582 
2583   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2584   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2585   if (!sdm->ops->computefunction) SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_ARG_WRONGSTATE,"Function never provided to SNES object");
2586   if (!sdm->ops->computejacobian) {
2587     ierr = DMSNESSetJacobian(dm,SNESComputeJacobianDefaultColor,NULL);CHKERRQ(ierr);
2588   }
2589   if (!snes->vec_func) {
2590     ierr = DMCreateGlobalVector(dm,&snes->vec_func);CHKERRQ(ierr);
2591   }
2592 
2593   if (!snes->ksp) {
2594     ierr = SNESGetKSP(snes, &snes->ksp);CHKERRQ(ierr);
2595   }
2596 
2597   if (!snes->linesearch) {
2598     ierr = SNESGetLineSearch(snes, &snes->linesearch);CHKERRQ(ierr);
2599   }
2600   ierr = SNESLineSearchSetFunction(snes->linesearch,SNESComputeFunction);CHKERRQ(ierr);
2601 
2602   if (snes->pc && (snes->pcside == PC_LEFT)) {
2603     snes->mf          = PETSC_TRUE;
2604     snes->mf_operator = PETSC_FALSE;
2605   }
2606 
2607   if (snes->mf) {
2608     ierr = SNESSetUpMatrixFree_Private(snes, snes->mf_operator, snes->mf_version);CHKERRQ(ierr);
2609   }
2610 
2611   if (snes->ops->usercompute && !snes->user) {
2612     ierr = (*snes->ops->usercompute)(snes,(void**)&snes->user);CHKERRQ(ierr);
2613   }
2614 
2615   if (snes->pc) {
2616     /* copy the DM over */
2617     ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2618     ierr = SNESSetDM(snes->pc,dm);CHKERRQ(ierr);
2619 
2620     ierr = SNESGetFunction(snes,&f,&func,&funcctx);CHKERRQ(ierr);
2621     ierr = VecDuplicate(f,&fpc);CHKERRQ(ierr);
2622     ierr = SNESSetFunction(snes->pc,fpc,func,funcctx);CHKERRQ(ierr);
2623     ierr = SNESGetJacobian(snes,NULL,NULL,&jac,&jacctx);CHKERRQ(ierr);
2624     ierr = SNESSetJacobian(snes->pc,NULL,NULL,jac,jacctx);CHKERRQ(ierr);
2625     ierr = SNESGetApplicationContext(snes,&appctx);CHKERRQ(ierr);
2626     ierr = SNESSetApplicationContext(snes->pc,appctx);CHKERRQ(ierr);
2627     ierr = VecDestroy(&fpc);CHKERRQ(ierr);
2628 
2629     /* copy the function pointers over */
2630     ierr = PetscObjectCopyFortranFunctionPointers((PetscObject)snes,(PetscObject)snes->pc);CHKERRQ(ierr);
2631 
2632     /* default to 1 iteration */
2633     ierr = SNESSetTolerances(snes->pc,0.0,0.0,0.0,1,snes->pc->max_funcs);CHKERRQ(ierr);
2634     if (snes->pcside==PC_RIGHT) {
2635       ierr = SNESSetNormSchedule(snes->pc,SNES_NORM_FINAL_ONLY);CHKERRQ(ierr);
2636     } else {
2637       ierr = SNESSetNormSchedule(snes->pc,SNES_NORM_NONE);CHKERRQ(ierr);
2638     }
2639     ierr = SNESSetFromOptions(snes->pc);CHKERRQ(ierr);
2640 
2641     /* copy the line search context over */
2642     ierr = SNESGetLineSearch(snes,&linesearch);CHKERRQ(ierr);
2643     ierr = SNESGetLineSearch(snes->pc,&pclinesearch);CHKERRQ(ierr);
2644     ierr = SNESLineSearchGetPreCheck(linesearch,&precheck,&lsprectx);CHKERRQ(ierr);
2645     ierr = SNESLineSearchGetPostCheck(linesearch,&postcheck,&lspostctx);CHKERRQ(ierr);
2646     ierr = SNESLineSearchSetPreCheck(pclinesearch,precheck,lsprectx);CHKERRQ(ierr);
2647     ierr = SNESLineSearchSetPostCheck(pclinesearch,postcheck,lspostctx);CHKERRQ(ierr);
2648     ierr = PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)pclinesearch);CHKERRQ(ierr);
2649   }
2650 
2651   snes->jac_iter = 0;
2652   snes->pre_iter = 0;
2653 
2654   if (snes->ops->setup) {
2655     ierr = (*snes->ops->setup)(snes);CHKERRQ(ierr);
2656   }
2657 
2658   if (snes->pc && (snes->pcside == PC_LEFT)) {
2659     if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
2660       ierr = SNESGetLineSearch(snes,&linesearch);CHKERRQ(ierr);
2661       ierr = SNESLineSearchSetFunction(linesearch,SNESComputeFunctionDefaultPC);CHKERRQ(ierr);
2662     }
2663   }
2664 
2665   snes->setupcalled = PETSC_TRUE;
2666   PetscFunctionReturn(0);
2667 }
2668 
2669 #undef __FUNCT__
2670 #define __FUNCT__ "SNESReset"
2671 /*@
2672    SNESReset - Resets a SNES context to the snessetupcalled = 0 state and removes any allocated Vecs and Mats
2673 
2674    Collective on SNES
2675 
2676    Input Parameter:
2677 .  snes - iterative context obtained from SNESCreate()
2678 
2679    Level: intermediate
2680 
2681    Notes: Also calls the application context destroy routine set with SNESSetComputeApplicationContext()
2682 
2683 .keywords: SNES, destroy
2684 
2685 .seealso: SNESCreate(), SNESSetUp(), SNESSolve()
2686 @*/
2687 PetscErrorCode  SNESReset(SNES snes)
2688 {
2689   PetscErrorCode ierr;
2690 
2691   PetscFunctionBegin;
2692   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2693   if (snes->ops->userdestroy && snes->user) {
2694     ierr       = (*snes->ops->userdestroy)((void**)&snes->user);CHKERRQ(ierr);
2695     snes->user = NULL;
2696   }
2697   if (snes->pc) {
2698     ierr = SNESReset(snes->pc);CHKERRQ(ierr);
2699   }
2700 
2701   if (snes->ops->reset) {
2702     ierr = (*snes->ops->reset)(snes);CHKERRQ(ierr);
2703   }
2704   if (snes->ksp) {
2705     ierr = KSPReset(snes->ksp);CHKERRQ(ierr);
2706   }
2707 
2708   if (snes->linesearch) {
2709     ierr = SNESLineSearchReset(snes->linesearch);CHKERRQ(ierr);
2710   }
2711 
2712   ierr = VecDestroy(&snes->vec_rhs);CHKERRQ(ierr);
2713   ierr = VecDestroy(&snes->vec_sol);CHKERRQ(ierr);
2714   ierr = VecDestroy(&snes->vec_sol_update);CHKERRQ(ierr);
2715   ierr = VecDestroy(&snes->vec_func);CHKERRQ(ierr);
2716   ierr = MatDestroy(&snes->jacobian);CHKERRQ(ierr);
2717   ierr = MatDestroy(&snes->jacobian_pre);CHKERRQ(ierr);
2718   ierr = VecDestroyVecs(snes->nwork,&snes->work);CHKERRQ(ierr);
2719   ierr = VecDestroyVecs(snes->nvwork,&snes->vwork);CHKERRQ(ierr);
2720 
2721   snes->nwork       = snes->nvwork = 0;
2722   snes->setupcalled = PETSC_FALSE;
2723   PetscFunctionReturn(0);
2724 }
2725 
2726 #undef __FUNCT__
2727 #define __FUNCT__ "SNESDestroy"
2728 /*@
2729    SNESDestroy - Destroys the nonlinear solver context that was created
2730    with SNESCreate().
2731 
2732    Collective on SNES
2733 
2734    Input Parameter:
2735 .  snes - the SNES context
2736 
2737    Level: beginner
2738 
2739 .keywords: SNES, nonlinear, destroy
2740 
2741 .seealso: SNESCreate(), SNESSolve()
2742 @*/
2743 PetscErrorCode  SNESDestroy(SNES *snes)
2744 {
2745   PetscErrorCode ierr;
2746 
2747   PetscFunctionBegin;
2748   if (!*snes) PetscFunctionReturn(0);
2749   PetscValidHeaderSpecific((*snes),SNES_CLASSID,1);
2750   if (--((PetscObject)(*snes))->refct > 0) {*snes = 0; PetscFunctionReturn(0);}
2751 
2752   ierr = SNESReset((*snes));CHKERRQ(ierr);
2753   ierr = SNESDestroy(&(*snes)->pc);CHKERRQ(ierr);
2754 
2755   /* if memory was published with AMS then destroy it */
2756   ierr = PetscObjectAMSViewOff((PetscObject)*snes);CHKERRQ(ierr);
2757   if ((*snes)->ops->destroy) {ierr = (*((*snes))->ops->destroy)((*snes));CHKERRQ(ierr);}
2758 
2759   ierr = DMDestroy(&(*snes)->dm);CHKERRQ(ierr);
2760   ierr = KSPDestroy(&(*snes)->ksp);CHKERRQ(ierr);
2761   ierr = SNESLineSearchDestroy(&(*snes)->linesearch);CHKERRQ(ierr);
2762 
2763   ierr = PetscFree((*snes)->kspconvctx);CHKERRQ(ierr);
2764   if ((*snes)->ops->convergeddestroy) {
2765     ierr = (*(*snes)->ops->convergeddestroy)((*snes)->cnvP);CHKERRQ(ierr);
2766   }
2767   if ((*snes)->conv_malloc) {
2768     ierr = PetscFree((*snes)->conv_hist);CHKERRQ(ierr);
2769     ierr = PetscFree((*snes)->conv_hist_its);CHKERRQ(ierr);
2770   }
2771   ierr = SNESMonitorCancel((*snes));CHKERRQ(ierr);
2772   ierr = PetscHeaderDestroy(snes);CHKERRQ(ierr);
2773   PetscFunctionReturn(0);
2774 }
2775 
2776 /* ----------- Routines to set solver parameters ---------- */
2777 
2778 #undef __FUNCT__
2779 #define __FUNCT__ "SNESSetLagPreconditioner"
2780 /*@
2781    SNESSetLagPreconditioner - Determines when the preconditioner is rebuilt in the nonlinear solve.
2782 
2783    Logically Collective on SNES
2784 
2785    Input Parameters:
2786 +  snes - the SNES context
2787 -  lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2788          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that
2789 
2790    Options Database Keys:
2791 .    -snes_lag_preconditioner <lag>
2792 
2793    Notes:
2794    The default is 1
2795    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2796    If  -1 is used before the very first nonlinear solve the preconditioner is still built because there is no previous preconditioner to use
2797 
2798    Level: intermediate
2799 
2800 .keywords: SNES, nonlinear, set, convergence, tolerances
2801 
2802 .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian()
2803 
2804 @*/
2805 PetscErrorCode  SNESSetLagPreconditioner(SNES snes,PetscInt lag)
2806 {
2807   PetscFunctionBegin;
2808   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2809   if (lag < -2) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag must be -2, -1, 1 or greater");
2810   if (!lag) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag cannot be 0");
2811   PetscValidLogicalCollectiveInt(snes,lag,2);
2812   snes->lagpreconditioner = lag;
2813   PetscFunctionReturn(0);
2814 }
2815 
2816 #undef __FUNCT__
2817 #define __FUNCT__ "SNESSetGridSequence"
2818 /*@
2819    SNESSetGridSequence - sets the number of steps of grid sequencing that SNES does
2820 
2821    Logically Collective on SNES
2822 
2823    Input Parameters:
2824 +  snes - the SNES context
2825 -  steps - the number of refinements to do, defaults to 0
2826 
2827    Options Database Keys:
2828 .    -snes_grid_sequence <steps>
2829 
2830    Level: intermediate
2831 
2832    Notes:
2833    Use SNESGetSolution() to extract the fine grid solution after grid sequencing.
2834 
2835 .keywords: SNES, nonlinear, set, convergence, tolerances
2836 
2837 .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian()
2838 
2839 @*/
2840 PetscErrorCode  SNESSetGridSequence(SNES snes,PetscInt steps)
2841 {
2842   PetscFunctionBegin;
2843   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2844   PetscValidLogicalCollectiveInt(snes,steps,2);
2845   snes->gridsequence = steps;
2846   PetscFunctionReturn(0);
2847 }
2848 
2849 #undef __FUNCT__
2850 #define __FUNCT__ "SNESGetLagPreconditioner"
2851 /*@
2852    SNESGetLagPreconditioner - Indicates how often the preconditioner is rebuilt
2853 
2854    Not Collective
2855 
2856    Input Parameter:
2857 .  snes - the SNES context
2858 
2859    Output Parameter:
2860 .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2861          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that
2862 
2863    Options Database Keys:
2864 .    -snes_lag_preconditioner <lag>
2865 
2866    Notes:
2867    The default is 1
2868    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2869 
2870    Level: intermediate
2871 
2872 .keywords: SNES, nonlinear, set, convergence, tolerances
2873 
2874 .seealso: SNESSetTrustRegionTolerance(), SNESSetLagPreconditioner()
2875 
2876 @*/
2877 PetscErrorCode  SNESGetLagPreconditioner(SNES snes,PetscInt *lag)
2878 {
2879   PetscFunctionBegin;
2880   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2881   *lag = snes->lagpreconditioner;
2882   PetscFunctionReturn(0);
2883 }
2884 
2885 #undef __FUNCT__
2886 #define __FUNCT__ "SNESSetLagJacobian"
2887 /*@
2888    SNESSetLagJacobian - Determines when the Jacobian is rebuilt in the nonlinear solve. See SNESSetLagPreconditioner() for determining how
2889      often the preconditioner is rebuilt.
2890 
2891    Logically Collective on SNES
2892 
2893    Input Parameters:
2894 +  snes - the SNES context
2895 -  lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2896          the Jacobian is built etc. -2 means rebuild at next chance but then never again
2897 
2898    Options Database Keys:
2899 .    -snes_lag_jacobian <lag>
2900 
2901    Notes:
2902    The default is 1
2903    The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2904    If  -1 is used before the very first nonlinear solve the CODE WILL FAIL! because no Jacobian is used, use -2 to indicate you want it recomputed
2905    at the next Newton step but never again (unless it is reset to another value)
2906 
2907    Level: intermediate
2908 
2909 .keywords: SNES, nonlinear, set, convergence, tolerances
2910 
2911 .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagPreconditioner(), SNESGetLagJacobian()
2912 
2913 @*/
2914 PetscErrorCode  SNESSetLagJacobian(SNES snes,PetscInt lag)
2915 {
2916   PetscFunctionBegin;
2917   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2918   if (lag < -2) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag must be -2, -1, 1 or greater");
2919   if (!lag) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag cannot be 0");
2920   PetscValidLogicalCollectiveInt(snes,lag,2);
2921   snes->lagjacobian = lag;
2922   PetscFunctionReturn(0);
2923 }
2924 
2925 #undef __FUNCT__
2926 #define __FUNCT__ "SNESGetLagJacobian"
2927 /*@
2928    SNESGetLagJacobian - Indicates how often the Jacobian is rebuilt. See SNESGetLagPreconditioner() to determine when the preconditioner is rebuilt
2929 
2930    Not Collective
2931 
2932    Input Parameter:
2933 .  snes - the SNES context
2934 
2935    Output Parameter:
2936 .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2937          the Jacobian is built etc.
2938 
2939    Options Database Keys:
2940 .    -snes_lag_jacobian <lag>
2941 
2942    Notes:
2943    The default is 1
2944    The jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2945 
2946    Level: intermediate
2947 
2948 .keywords: SNES, nonlinear, set, convergence, tolerances
2949 
2950 .seealso: SNESSetTrustRegionTolerance(), SNESSetLagJacobian(), SNESSetLagPreconditioner(), SNESGetLagPreconditioner()
2951 
2952 @*/
2953 PetscErrorCode  SNESGetLagJacobian(SNES snes,PetscInt *lag)
2954 {
2955   PetscFunctionBegin;
2956   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2957   *lag = snes->lagjacobian;
2958   PetscFunctionReturn(0);
2959 }
2960 
2961 #undef __FUNCT__
2962 #define __FUNCT__ "SNESSetLagJacobianPersists"
2963 /*@
2964    SNESSetLagJacobianPersists - Set whether or not the Jacobian lagging persists through multiple solves
2965 
2966    Logically collective on SNES
2967 
2968    Input Parameter:
2969 +  snes - the SNES context
2970 -   flg - jacobian lagging persists if true
2971 
2972    Options Database Keys:
2973 .    -snes_lag_jacobian_persists <flg>
2974 
2975    Notes: This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by
2976    several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several
2977    timesteps may present huge efficiency gains.
2978 
2979    Level: developer
2980 
2981 .keywords: SNES, nonlinear, lag, NPC
2982 
2983 .seealso: SNESSetLagPreconditionerPersists(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetPC()
2984 
2985 @*/
2986 PetscErrorCode  SNESSetLagJacobianPersists(SNES snes,PetscBool flg)
2987 {
2988   PetscFunctionBegin;
2989   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2990   PetscValidLogicalCollectiveBool(snes,flg,2);
2991   snes->lagjac_persist = flg;
2992   PetscFunctionReturn(0);
2993 }
2994 
2995 #undef __FUNCT__
2996 #define __FUNCT__ "SNESSetLagPreconditionerPersists"
2997 /*@
2998    SNESSetLagPreconditionerPersists - Set whether or not the preconditioner lagging persists through multiple solves
2999 
3000    Logically Collective on SNES
3001 
3002    Input Parameter:
3003 +  snes - the SNES context
3004 -   flg - preconditioner lagging persists if true
3005 
3006    Options Database Keys:
3007 .    -snes_lag_jacobian_persists <flg>
3008 
3009    Notes: This is useful both for nonlinear preconditioning, where it's appropriate to have the preconditioner be stale
3010    by several solves, and for implicit time-stepping, where preconditioner lagging in the inner nonlinear solve over
3011    several timesteps may present huge efficiency gains.
3012 
3013    Level: developer
3014 
3015 .keywords: SNES, nonlinear, lag, NPC
3016 
3017 .seealso: SNESSetLagJacobianPersists(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetPC()
3018 
3019 @*/
3020 PetscErrorCode  SNESSetLagPreconditionerPersists(SNES snes,PetscBool flg)
3021 {
3022   PetscFunctionBegin;
3023   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3024   PetscValidLogicalCollectiveBool(snes,flg,2);
3025   snes->lagpre_persist = flg;
3026   PetscFunctionReturn(0);
3027 }
3028 
3029 #undef __FUNCT__
3030 #define __FUNCT__ "SNESSetTolerances"
3031 /*@
3032    SNESSetTolerances - Sets various parameters used in convergence tests.
3033 
3034    Logically Collective on SNES
3035 
3036    Input Parameters:
3037 +  snes - the SNES context
3038 .  abstol - absolute convergence tolerance
3039 .  rtol - relative convergence tolerance
3040 .  stol -  convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
3041 .  maxit - maximum number of iterations
3042 -  maxf - maximum number of function evaluations
3043 
3044    Options Database Keys:
3045 +    -snes_atol <abstol> - Sets abstol
3046 .    -snes_rtol <rtol> - Sets rtol
3047 .    -snes_stol <stol> - Sets stol
3048 .    -snes_max_it <maxit> - Sets maxit
3049 -    -snes_max_funcs <maxf> - Sets maxf
3050 
3051    Notes:
3052    The default maximum number of iterations is 50.
3053    The default maximum number of function evaluations is 1000.
3054 
3055    Level: intermediate
3056 
3057 .keywords: SNES, nonlinear, set, convergence, tolerances
3058 
3059 .seealso: SNESSetTrustRegionTolerance()
3060 @*/
3061 PetscErrorCode  SNESSetTolerances(SNES snes,PetscReal abstol,PetscReal rtol,PetscReal stol,PetscInt maxit,PetscInt maxf)
3062 {
3063   PetscFunctionBegin;
3064   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3065   PetscValidLogicalCollectiveReal(snes,abstol,2);
3066   PetscValidLogicalCollectiveReal(snes,rtol,3);
3067   PetscValidLogicalCollectiveReal(snes,stol,4);
3068   PetscValidLogicalCollectiveInt(snes,maxit,5);
3069   PetscValidLogicalCollectiveInt(snes,maxf,6);
3070 
3071   if (abstol != PETSC_DEFAULT) {
3072     if (abstol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Absolute tolerance %G must be non-negative",abstol);
3073     snes->abstol = abstol;
3074   }
3075   if (rtol != PETSC_DEFAULT) {
3076     if (rtol < 0.0 || 1.0 <= rtol) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Relative tolerance %G must be non-negative and less than 1.0",rtol);
3077     snes->rtol = rtol;
3078   }
3079   if (stol != PETSC_DEFAULT) {
3080     if (stol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Step tolerance %G must be non-negative",stol);
3081     snes->stol = stol;
3082   }
3083   if (maxit != PETSC_DEFAULT) {
3084     if (maxit < 0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Maximum number of iterations %D must be non-negative",maxit);
3085     snes->max_its = maxit;
3086   }
3087   if (maxf != PETSC_DEFAULT) {
3088     if (maxf < 0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Maximum number of function evaluations %D must be non-negative",maxf);
3089     snes->max_funcs = maxf;
3090   }
3091   snes->tolerancesset = PETSC_TRUE;
3092   PetscFunctionReturn(0);
3093 }
3094 
3095 #undef __FUNCT__
3096 #define __FUNCT__ "SNESGetTolerances"
3097 /*@
3098    SNESGetTolerances - Gets various parameters used in convergence tests.
3099 
3100    Not Collective
3101 
3102    Input Parameters:
3103 +  snes - the SNES context
3104 .  atol - absolute convergence tolerance
3105 .  rtol - relative convergence tolerance
3106 .  stol -  convergence tolerance in terms of the norm
3107            of the change in the solution between steps
3108 .  maxit - maximum number of iterations
3109 -  maxf - maximum number of function evaluations
3110 
3111    Notes:
3112    The user can specify NULL for any parameter that is not needed.
3113 
3114    Level: intermediate
3115 
3116 .keywords: SNES, nonlinear, get, convergence, tolerances
3117 
3118 .seealso: SNESSetTolerances()
3119 @*/
3120 PetscErrorCode  SNESGetTolerances(SNES snes,PetscReal *atol,PetscReal *rtol,PetscReal *stol,PetscInt *maxit,PetscInt *maxf)
3121 {
3122   PetscFunctionBegin;
3123   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3124   if (atol)  *atol  = snes->abstol;
3125   if (rtol)  *rtol  = snes->rtol;
3126   if (stol)  *stol  = snes->stol;
3127   if (maxit) *maxit = snes->max_its;
3128   if (maxf)  *maxf  = snes->max_funcs;
3129   PetscFunctionReturn(0);
3130 }
3131 
3132 #undef __FUNCT__
3133 #define __FUNCT__ "SNESSetTrustRegionTolerance"
3134 /*@
3135    SNESSetTrustRegionTolerance - Sets the trust region parameter tolerance.
3136 
3137    Logically Collective on SNES
3138 
3139    Input Parameters:
3140 +  snes - the SNES context
3141 -  tol - tolerance
3142 
3143    Options Database Key:
3144 .  -snes_trtol <tol> - Sets tol
3145 
3146    Level: intermediate
3147 
3148 .keywords: SNES, nonlinear, set, trust region, tolerance
3149 
3150 .seealso: SNESSetTolerances()
3151 @*/
3152 PetscErrorCode  SNESSetTrustRegionTolerance(SNES snes,PetscReal tol)
3153 {
3154   PetscFunctionBegin;
3155   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3156   PetscValidLogicalCollectiveReal(snes,tol,2);
3157   snes->deltatol = tol;
3158   PetscFunctionReturn(0);
3159 }
3160 
3161 /*
3162    Duplicate the lg monitors for SNES from KSP; for some reason with
3163    dynamic libraries things don't work under Sun4 if we just use
3164    macros instead of functions
3165 */
3166 #undef __FUNCT__
3167 #define __FUNCT__ "SNESMonitorLGResidualNorm"
3168 PetscErrorCode  SNESMonitorLGResidualNorm(SNES snes,PetscInt it,PetscReal norm,void *ctx)
3169 {
3170   PetscErrorCode ierr;
3171 
3172   PetscFunctionBegin;
3173   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3174   ierr = KSPMonitorLGResidualNorm((KSP)snes,it,norm,ctx);CHKERRQ(ierr);
3175   PetscFunctionReturn(0);
3176 }
3177 
3178 #undef __FUNCT__
3179 #define __FUNCT__ "SNESMonitorLGCreate"
3180 PetscErrorCode  SNESMonitorLGCreate(const char host[],const char label[],int x,int y,int m,int n,PetscDrawLG *draw)
3181 {
3182   PetscErrorCode ierr;
3183 
3184   PetscFunctionBegin;
3185   ierr = KSPMonitorLGResidualNormCreate(host,label,x,y,m,n,draw);CHKERRQ(ierr);
3186   PetscFunctionReturn(0);
3187 }
3188 
3189 #undef __FUNCT__
3190 #define __FUNCT__ "SNESMonitorLGDestroy"
3191 PetscErrorCode  SNESMonitorLGDestroy(PetscDrawLG *draw)
3192 {
3193   PetscErrorCode ierr;
3194 
3195   PetscFunctionBegin;
3196   ierr = KSPMonitorLGResidualNormDestroy(draw);CHKERRQ(ierr);
3197   PetscFunctionReturn(0);
3198 }
3199 
3200 extern PetscErrorCode  SNESMonitorRange_Private(SNES,PetscInt,PetscReal*);
3201 #undef __FUNCT__
3202 #define __FUNCT__ "SNESMonitorLGRange"
3203 PetscErrorCode  SNESMonitorLGRange(SNES snes,PetscInt n,PetscReal rnorm,void *monctx)
3204 {
3205   PetscDrawLG      lg;
3206   PetscErrorCode   ierr;
3207   PetscReal        x,y,per;
3208   PetscViewer      v = (PetscViewer)monctx;
3209   static PetscReal prev; /* should be in the context */
3210   PetscDraw        draw;
3211 
3212   PetscFunctionBegin;
3213   ierr = PetscViewerDrawGetDrawLG(v,0,&lg);CHKERRQ(ierr);
3214   if (!n) {ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3215   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3216   ierr = PetscDrawSetTitle(draw,"Residual norm");CHKERRQ(ierr);
3217   x    = (PetscReal)n;
3218   if (rnorm > 0.0) y = log10(rnorm);
3219   else y = -15.0;
3220   ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3221   if (n < 20 || !(n % 5)) {
3222     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3223   }
3224 
3225   ierr = PetscViewerDrawGetDrawLG(v,1,&lg);CHKERRQ(ierr);
3226   if (!n) {ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3227   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3228   ierr = PetscDrawSetTitle(draw,"% elemts > .2*max elemt");CHKERRQ(ierr);
3229   ierr =  SNESMonitorRange_Private(snes,n,&per);CHKERRQ(ierr);
3230   x    = (PetscReal)n;
3231   y    = 100.0*per;
3232   ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3233   if (n < 20 || !(n % 5)) {
3234     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3235   }
3236 
3237   ierr = PetscViewerDrawGetDrawLG(v,2,&lg);CHKERRQ(ierr);
3238   if (!n) {prev = rnorm;ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3239   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3240   ierr = PetscDrawSetTitle(draw,"(norm -oldnorm)/oldnorm");CHKERRQ(ierr);
3241   x    = (PetscReal)n;
3242   y    = (prev - rnorm)/prev;
3243   ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3244   if (n < 20 || !(n % 5)) {
3245     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3246   }
3247 
3248   ierr = PetscViewerDrawGetDrawLG(v,3,&lg);CHKERRQ(ierr);
3249   if (!n) {ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3250   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3251   ierr = PetscDrawSetTitle(draw,"(norm -oldnorm)/oldnorm*(% > .2 max)");CHKERRQ(ierr);
3252   x    = (PetscReal)n;
3253   y    = (prev - rnorm)/(prev*per);
3254   if (n > 2) { /*skip initial crazy value */
3255     ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3256   }
3257   if (n < 20 || !(n % 5)) {
3258     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3259   }
3260   prev = rnorm;
3261   PetscFunctionReturn(0);
3262 }
3263 
3264 #undef __FUNCT__
3265 #define __FUNCT__ "SNESMonitor"
3266 /*@
3267    SNESMonitor - runs the user provided monitor routines, if they exist
3268 
3269    Collective on SNES
3270 
3271    Input Parameters:
3272 +  snes - nonlinear solver context obtained from SNESCreate()
3273 .  iter - iteration number
3274 -  rnorm - relative norm of the residual
3275 
3276    Notes:
3277    This routine is called by the SNES implementations.
3278    It does not typically need to be called by the user.
3279 
3280    Level: developer
3281 
3282 .seealso: SNESMonitorSet()
3283 @*/
3284 PetscErrorCode  SNESMonitor(SNES snes,PetscInt iter,PetscReal rnorm)
3285 {
3286   PetscErrorCode ierr;
3287   PetscInt       i,n = snes->numbermonitors;
3288 
3289   PetscFunctionBegin;
3290   for (i=0; i<n; i++) {
3291     ierr = (*snes->monitor[i])(snes,iter,rnorm,snes->monitorcontext[i]);CHKERRQ(ierr);
3292   }
3293   PetscFunctionReturn(0);
3294 }
3295 
3296 /* ------------ Routines to set performance monitoring options ----------- */
3297 
3298 /*MC
3299     SNESMonitorFunction - functional form passed to SNESMonitorSet() to monitor convergence of nonlinear solver
3300 
3301      Synopsis:
3302      #include "petscsnes.h"
3303 $    PetscErrorCode SNESMonitorFunction(SNES snes,PetscInt its, PetscReal norm,void *mctx)
3304 
3305 +    snes - the SNES context
3306 .    its - iteration number
3307 .    norm - 2-norm function value (may be estimated)
3308 -    mctx - [optional] monitoring context
3309 
3310    Level: advanced
3311 
3312 .seealso:   SNESMonitorSet(), SNESMonitorGet()
3313 M*/
3314 
3315 #undef __FUNCT__
3316 #define __FUNCT__ "SNESMonitorSet"
3317 /*@C
3318    SNESMonitorSet - Sets an ADDITIONAL function that is to be used at every
3319    iteration of the nonlinear solver to display the iteration's
3320    progress.
3321 
3322    Logically Collective on SNES
3323 
3324    Input Parameters:
3325 +  snes - the SNES context
3326 .  SNESMonitorFunction - monitoring routine
3327 .  mctx - [optional] user-defined context for private data for the
3328           monitor routine (use NULL if no context is desired)
3329 -  monitordestroy - [optional] routine that frees monitor context
3330           (may be NULL)
3331 
3332    Options Database Keys:
3333 +    -snes_monitor        - sets SNESMonitorDefault()
3334 .    -snes_monitor_lg_residualnorm    - sets line graph monitor,
3335                             uses SNESMonitorLGCreate()
3336 -    -snes_monitor_cancel - cancels all monitors that have
3337                             been hardwired into a code by
3338                             calls to SNESMonitorSet(), but
3339                             does not cancel those set via
3340                             the options database.
3341 
3342    Notes:
3343    Several different monitoring routines may be set by calling
3344    SNESMonitorSet() multiple times; all will be called in the
3345    order in which they were set.
3346 
3347    Fortran notes: Only a single monitor function can be set for each SNES object
3348 
3349    Level: intermediate
3350 
3351 .keywords: SNES, nonlinear, set, monitor
3352 
3353 .seealso: SNESMonitorDefault(), SNESMonitorCancel(), SNESMonitorFunction
3354 @*/
3355 PetscErrorCode  SNESMonitorSet(SNES snes,PetscErrorCode (*SNESMonitorFunction)(SNES,PetscInt,PetscReal,void*),void *mctx,PetscErrorCode (*monitordestroy)(void**))
3356 {
3357   PetscInt       i;
3358   PetscErrorCode ierr;
3359 
3360   PetscFunctionBegin;
3361   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3362   if (snes->numbermonitors >= MAXSNESMONITORS) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Too many monitors set");
3363   for (i=0; i<snes->numbermonitors;i++) {
3364     if (SNESMonitorFunction == snes->monitor[i] && monitordestroy == snes->monitordestroy[i] && mctx == snes->monitorcontext[i]) {
3365       if (monitordestroy) {
3366         ierr = (*monitordestroy)(&mctx);CHKERRQ(ierr);
3367       }
3368       PetscFunctionReturn(0);
3369     }
3370   }
3371   snes->monitor[snes->numbermonitors]          = SNESMonitorFunction;
3372   snes->monitordestroy[snes->numbermonitors]   = monitordestroy;
3373   snes->monitorcontext[snes->numbermonitors++] = (void*)mctx;
3374   PetscFunctionReturn(0);
3375 }
3376 
3377 #undef __FUNCT__
3378 #define __FUNCT__ "SNESMonitorCancel"
3379 /*@
3380    SNESMonitorCancel - Clears all the monitor functions for a SNES object.
3381 
3382    Logically Collective on SNES
3383 
3384    Input Parameters:
3385 .  snes - the SNES context
3386 
3387    Options Database Key:
3388 .  -snes_monitor_cancel - cancels all monitors that have been hardwired
3389     into a code by calls to SNESMonitorSet(), but does not cancel those
3390     set via the options database
3391 
3392    Notes:
3393    There is no way to clear one specific monitor from a SNES object.
3394 
3395    Level: intermediate
3396 
3397 .keywords: SNES, nonlinear, set, monitor
3398 
3399 .seealso: SNESMonitorDefault(), SNESMonitorSet()
3400 @*/
3401 PetscErrorCode  SNESMonitorCancel(SNES snes)
3402 {
3403   PetscErrorCode ierr;
3404   PetscInt       i;
3405 
3406   PetscFunctionBegin;
3407   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3408   for (i=0; i<snes->numbermonitors; i++) {
3409     if (snes->monitordestroy[i]) {
3410       ierr = (*snes->monitordestroy[i])(&snes->monitorcontext[i]);CHKERRQ(ierr);
3411     }
3412   }
3413   snes->numbermonitors = 0;
3414   PetscFunctionReturn(0);
3415 }
3416 
3417 /*MC
3418     SNESConvergenceTestFunction - functional form used for testing of convergence of nonlinear solver
3419 
3420      Synopsis:
3421      #include "petscsnes.h"
3422 $     PetscErrorCode SNESConvergenceTest(SNES snes,PetscInt it,PetscReal xnorm,PetscReal gnorm,PetscReal f,SNESConvergedReason *reason,void *cctx)
3423 
3424 +    snes - the SNES context
3425 .    it - current iteration (0 is the first and is before any Newton step)
3426 .    cctx - [optional] convergence context
3427 .    reason - reason for convergence/divergence
3428 .    xnorm - 2-norm of current iterate
3429 .    gnorm - 2-norm of current step
3430 -    f - 2-norm of function
3431 
3432    Level: intermediate
3433 
3434 .seealso:   SNESSetConvergenceTest(), SNESGetConvergenceTest()
3435 M*/
3436 
3437 #undef __FUNCT__
3438 #define __FUNCT__ "SNESSetConvergenceTest"
3439 /*@C
3440    SNESSetConvergenceTest - Sets the function that is to be used
3441    to test for convergence of the nonlinear iterative solution.
3442 
3443    Logically Collective on SNES
3444 
3445    Input Parameters:
3446 +  snes - the SNES context
3447 .  SNESConvergenceTestFunction - routine to test for convergence
3448 .  cctx - [optional] context for private data for the convergence routine  (may be NULL)
3449 -  destroy - [optional] destructor for the context (may be NULL; NULL_FUNCTION in Fortran)
3450 
3451    Level: advanced
3452 
3453 .keywords: SNES, nonlinear, set, convergence, test
3454 
3455 .seealso: SNESConvergedDefault(), SNESConvergedSkip(), SNESConvergenceTestFunction
3456 @*/
3457 PetscErrorCode  SNESSetConvergenceTest(SNES snes,PetscErrorCode (*SNESConvergenceTestFunction)(SNES,PetscInt,PetscReal,PetscReal,PetscReal,SNESConvergedReason*,void*),void *cctx,PetscErrorCode (*destroy)(void*))
3458 {
3459   PetscErrorCode ierr;
3460 
3461   PetscFunctionBegin;
3462   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3463   if (!SNESConvergenceTestFunction) SNESConvergenceTestFunction = SNESConvergedSkip;
3464   if (snes->ops->convergeddestroy) {
3465     ierr = (*snes->ops->convergeddestroy)(snes->cnvP);CHKERRQ(ierr);
3466   }
3467   snes->ops->converged        = SNESConvergenceTestFunction;
3468   snes->ops->convergeddestroy = destroy;
3469   snes->cnvP                  = cctx;
3470   PetscFunctionReturn(0);
3471 }
3472 
3473 #undef __FUNCT__
3474 #define __FUNCT__ "SNESGetConvergedReason"
3475 /*@
3476    SNESGetConvergedReason - Gets the reason the SNES iteration was stopped.
3477 
3478    Not Collective
3479 
3480    Input Parameter:
3481 .  snes - the SNES context
3482 
3483    Output Parameter:
3484 .  reason - negative value indicates diverged, positive value converged, see SNESConvergedReason or the
3485             manual pages for the individual convergence tests for complete lists
3486 
3487    Level: intermediate
3488 
3489    Notes: Can only be called after the call the SNESSolve() is complete.
3490 
3491 .keywords: SNES, nonlinear, set, convergence, test
3492 
3493 .seealso: SNESSetConvergenceTest(), SNESConvergedReason
3494 @*/
3495 PetscErrorCode  SNESGetConvergedReason(SNES snes,SNESConvergedReason *reason)
3496 {
3497   PetscFunctionBegin;
3498   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3499   PetscValidPointer(reason,2);
3500   *reason = snes->reason;
3501   PetscFunctionReturn(0);
3502 }
3503 
3504 #undef __FUNCT__
3505 #define __FUNCT__ "SNESSetConvergenceHistory"
3506 /*@
3507    SNESSetConvergenceHistory - Sets the array used to hold the convergence history.
3508 
3509    Logically Collective on SNES
3510 
3511    Input Parameters:
3512 +  snes - iterative context obtained from SNESCreate()
3513 .  a   - array to hold history, this array will contain the function norms computed at each step
3514 .  its - integer array holds the number of linear iterations for each solve.
3515 .  na  - size of a and its
3516 -  reset - PETSC_TRUE indicates each new nonlinear solve resets the history counter to zero,
3517            else it continues storing new values for new nonlinear solves after the old ones
3518 
3519    Notes:
3520    If 'a' and 'its' are NULL then space is allocated for the history. If 'na' PETSC_DECIDE or PETSC_DEFAULT then a
3521    default array of length 10000 is allocated.
3522 
3523    This routine is useful, e.g., when running a code for purposes
3524    of accurate performance monitoring, when no I/O should be done
3525    during the section of code that is being timed.
3526 
3527    Level: intermediate
3528 
3529 .keywords: SNES, set, convergence, history
3530 
3531 .seealso: SNESGetConvergenceHistory()
3532 
3533 @*/
3534 PetscErrorCode  SNESSetConvergenceHistory(SNES snes,PetscReal a[],PetscInt its[],PetscInt na,PetscBool reset)
3535 {
3536   PetscErrorCode ierr;
3537 
3538   PetscFunctionBegin;
3539   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3540   if (a) PetscValidScalarPointer(a,2);
3541   if (its) PetscValidIntPointer(its,3);
3542   if (!a) {
3543     if (na == PETSC_DECIDE || na == PETSC_DEFAULT) na = 1000;
3544     ierr = PetscMalloc(na*sizeof(PetscReal),&a);CHKERRQ(ierr);
3545     ierr = PetscMalloc(na*sizeof(PetscInt),&its);CHKERRQ(ierr);
3546 
3547     snes->conv_malloc = PETSC_TRUE;
3548   }
3549   snes->conv_hist       = a;
3550   snes->conv_hist_its   = its;
3551   snes->conv_hist_max   = na;
3552   snes->conv_hist_len   = 0;
3553   snes->conv_hist_reset = reset;
3554   PetscFunctionReturn(0);
3555 }
3556 
3557 #if defined(PETSC_HAVE_MATLAB_ENGINE)
3558 #include <engine.h>   /* MATLAB include file */
3559 #include <mex.h>      /* MATLAB include file */
3560 
3561 #undef __FUNCT__
3562 #define __FUNCT__ "SNESGetConvergenceHistoryMatlab"
3563 PETSC_EXTERN mxArray *SNESGetConvergenceHistoryMatlab(SNES snes)
3564 {
3565   mxArray   *mat;
3566   PetscInt  i;
3567   PetscReal *ar;
3568 
3569   PetscFunctionBegin;
3570   mat = mxCreateDoubleMatrix(snes->conv_hist_len,1,mxREAL);
3571   ar  = (PetscReal*) mxGetData(mat);
3572   for (i=0; i<snes->conv_hist_len; i++) ar[i] = snes->conv_hist[i];
3573   PetscFunctionReturn(mat);
3574 }
3575 #endif
3576 
3577 #undef __FUNCT__
3578 #define __FUNCT__ "SNESGetConvergenceHistory"
3579 /*@C
3580    SNESGetConvergenceHistory - Gets the array used to hold the convergence history.
3581 
3582    Not Collective
3583 
3584    Input Parameter:
3585 .  snes - iterative context obtained from SNESCreate()
3586 
3587    Output Parameters:
3588 .  a   - array to hold history
3589 .  its - integer array holds the number of linear iterations (or
3590          negative if not converged) for each solve.
3591 -  na  - size of a and its
3592 
3593    Notes:
3594     The calling sequence for this routine in Fortran is
3595 $   call SNESGetConvergenceHistory(SNES snes, integer na, integer ierr)
3596 
3597    This routine is useful, e.g., when running a code for purposes
3598    of accurate performance monitoring, when no I/O should be done
3599    during the section of code that is being timed.
3600 
3601    Level: intermediate
3602 
3603 .keywords: SNES, get, convergence, history
3604 
3605 .seealso: SNESSetConvergencHistory()
3606 
3607 @*/
3608 PetscErrorCode  SNESGetConvergenceHistory(SNES snes,PetscReal *a[],PetscInt *its[],PetscInt *na)
3609 {
3610   PetscFunctionBegin;
3611   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3612   if (a)   *a   = snes->conv_hist;
3613   if (its) *its = snes->conv_hist_its;
3614   if (na)  *na  = snes->conv_hist_len;
3615   PetscFunctionReturn(0);
3616 }
3617 
3618 #undef __FUNCT__
3619 #define __FUNCT__ "SNESSetUpdate"
3620 /*@C
3621   SNESSetUpdate - Sets the general-purpose update function called
3622   at the beginning of every iteration of the nonlinear solve. Specifically
3623   it is called just before the Jacobian is "evaluated".
3624 
3625   Logically Collective on SNES
3626 
3627   Input Parameters:
3628 . snes - The nonlinear solver context
3629 . func - The function
3630 
3631   Calling sequence of func:
3632 . func (SNES snes, PetscInt step);
3633 
3634 . step - The current step of the iteration
3635 
3636   Level: advanced
3637 
3638   Note: This is NOT what one uses to update the ghost points before a function evaluation, that should be done at the beginning of your FormFunction()
3639         This is not used by most users.
3640 
3641 .keywords: SNES, update
3642 
3643 .seealso SNESSetJacobian(), SNESSolve()
3644 @*/
3645 PetscErrorCode  SNESSetUpdate(SNES snes, PetscErrorCode (*func)(SNES, PetscInt))
3646 {
3647   PetscFunctionBegin;
3648   PetscValidHeaderSpecific(snes, SNES_CLASSID,1);
3649   snes->ops->update = func;
3650   PetscFunctionReturn(0);
3651 }
3652 
3653 #undef __FUNCT__
3654 #define __FUNCT__ "SNESScaleStep_Private"
3655 /*
3656    SNESScaleStep_Private - Scales a step so that its length is less than the
3657    positive parameter delta.
3658 
3659     Input Parameters:
3660 +   snes - the SNES context
3661 .   y - approximate solution of linear system
3662 .   fnorm - 2-norm of current function
3663 -   delta - trust region size
3664 
3665     Output Parameters:
3666 +   gpnorm - predicted function norm at the new point, assuming local
3667     linearization.  The value is zero if the step lies within the trust
3668     region, and exceeds zero otherwise.
3669 -   ynorm - 2-norm of the step
3670 
3671     Note:
3672     For non-trust region methods such as SNESNEWTONLS, the parameter delta
3673     is set to be the maximum allowable step size.
3674 
3675 .keywords: SNES, nonlinear, scale, step
3676 */
3677 PetscErrorCode SNESScaleStep_Private(SNES snes,Vec y,PetscReal *fnorm,PetscReal *delta,PetscReal *gpnorm,PetscReal *ynorm)
3678 {
3679   PetscReal      nrm;
3680   PetscScalar    cnorm;
3681   PetscErrorCode ierr;
3682 
3683   PetscFunctionBegin;
3684   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3685   PetscValidHeaderSpecific(y,VEC_CLASSID,2);
3686   PetscCheckSameComm(snes,1,y,2);
3687 
3688   ierr = VecNorm(y,NORM_2,&nrm);CHKERRQ(ierr);
3689   if (nrm > *delta) {
3690     nrm     = *delta/nrm;
3691     *gpnorm = (1.0 - nrm)*(*fnorm);
3692     cnorm   = nrm;
3693     ierr    = VecScale(y,cnorm);CHKERRQ(ierr);
3694     *ynorm  = *delta;
3695   } else {
3696     *gpnorm = 0.0;
3697     *ynorm  = nrm;
3698   }
3699   PetscFunctionReturn(0);
3700 }
3701 
3702 #undef __FUNCT__
3703 #define __FUNCT__ "SNESSolve"
3704 /*@C
3705    SNESSolve - Solves a nonlinear system F(x) = b.
3706    Call SNESSolve() after calling SNESCreate() and optional routines of the form SNESSetXXX().
3707 
3708    Collective on SNES
3709 
3710    Input Parameters:
3711 +  snes - the SNES context
3712 .  b - the constant part of the equation F(x) = b, or NULL to use zero.
3713 -  x - the solution vector.
3714 
3715    Notes:
3716    The user should initialize the vector,x, with the initial guess
3717    for the nonlinear solve prior to calling SNESSolve.  In particular,
3718    to employ an initial guess of zero, the user should explicitly set
3719    this vector to zero by calling VecSet().
3720 
3721    Level: beginner
3722 
3723 .keywords: SNES, nonlinear, solve
3724 
3725 .seealso: SNESCreate(), SNESDestroy(), SNESSetFunction(), SNESSetJacobian(), SNESSetGridSequence(), SNESGetSolution()
3726 @*/
3727 PetscErrorCode  SNESSolve(SNES snes,Vec b,Vec x)
3728 {
3729   PetscErrorCode    ierr;
3730   PetscBool         flg;
3731   PetscViewer       viewer;
3732   PetscInt          grid;
3733   Vec               xcreated = NULL;
3734   DM                dm;
3735   PetscViewerFormat format;
3736 
3737   PetscFunctionBegin;
3738   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3739   if (x) PetscValidHeaderSpecific(x,VEC_CLASSID,3);
3740   if (x) PetscCheckSameComm(snes,1,x,3);
3741   if (b) PetscValidHeaderSpecific(b,VEC_CLASSID,2);
3742   if (b) PetscCheckSameComm(snes,1,b,2);
3743 
3744   if (!x) {
3745     ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
3746     ierr = DMCreateGlobalVector(dm,&xcreated);CHKERRQ(ierr);
3747     x    = xcreated;
3748   }
3749 
3750   ierr = PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->prefix,"-snes_view_pre",&viewer,&format,&flg);CHKERRQ(ierr);
3751   if (flg && !PetscPreLoadingOn) {
3752     ierr = PetscViewerPushFormat(viewer,format);CHKERRQ(ierr);
3753     ierr = SNESView(snes,viewer);CHKERRQ(ierr);
3754     ierr = PetscViewerPopFormat(viewer);CHKERRQ(ierr);
3755     ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
3756   }
3757 
3758   for (grid=0; grid<snes->gridsequence; grid++) {ierr = PetscViewerASCIIPushTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)));CHKERRQ(ierr);}
3759   for (grid=0; grid<snes->gridsequence+1; grid++) {
3760 
3761     /* set solution vector */
3762     if (!grid) {ierr = PetscObjectReference((PetscObject)x);CHKERRQ(ierr);}
3763     ierr          = VecDestroy(&snes->vec_sol);CHKERRQ(ierr);
3764     snes->vec_sol = x;
3765     ierr          = SNESGetDM(snes,&dm);CHKERRQ(ierr);
3766 
3767     /* set affine vector if provided */
3768     if (b) { ierr = PetscObjectReference((PetscObject)b);CHKERRQ(ierr); }
3769     ierr          = VecDestroy(&snes->vec_rhs);CHKERRQ(ierr);
3770     snes->vec_rhs = b;
3771 
3772     if (snes->vec_func == snes->vec_sol) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_IDN,"Solution vector cannot be function vector");
3773     if (snes->vec_rhs  == snes->vec_sol) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_IDN,"Solution vector cannot be right hand side vector");
3774     if (!snes->vec_sol_update /* && snes->vec_sol */) {
3775       ierr = VecDuplicate(snes->vec_sol,&snes->vec_sol_update);CHKERRQ(ierr);
3776       ierr = PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->vec_sol_update);CHKERRQ(ierr);
3777     }
3778     ierr = DMShellSetGlobalVector(dm,snes->vec_sol);CHKERRQ(ierr);
3779     ierr = SNESSetUp(snes);CHKERRQ(ierr);
3780 
3781     if (!grid) {
3782       if (snes->ops->computeinitialguess) {
3783         ierr = (*snes->ops->computeinitialguess)(snes,snes->vec_sol,snes->initialguessP);CHKERRQ(ierr);
3784       }
3785     }
3786 
3787     if (snes->conv_hist_reset) snes->conv_hist_len = 0;
3788     if (snes->counters_reset) {snes->nfuncs = 0; snes->linear_its = 0; snes->numFailures = 0;}
3789 
3790     ierr = PetscLogEventBegin(SNES_Solve,snes,0,0,0);CHKERRQ(ierr);
3791     ierr = (*snes->ops->solve)(snes);CHKERRQ(ierr);
3792     ierr = PetscLogEventEnd(SNES_Solve,snes,0,0,0);CHKERRQ(ierr);
3793     if (snes->domainerror) {
3794       snes->reason      = SNES_DIVERGED_FUNCTION_DOMAIN;
3795       snes->domainerror = PETSC_FALSE;
3796     }
3797     if (!snes->reason) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Internal error, solver returned without setting converged reason");
3798 
3799     if (snes->lagjac_persist) snes->jac_iter += snes->iter;
3800     if (snes->lagpre_persist) snes->pre_iter += snes->iter;
3801 
3802     flg  = PETSC_FALSE;
3803     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_test_local_min",&flg,NULL);CHKERRQ(ierr);
3804     if (flg && !PetscPreLoadingOn) { ierr = SNESTestLocalMin(snes);CHKERRQ(ierr); }
3805     if (snes->printreason) {
3806       ierr = PetscViewerASCIIAddTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)),((PetscObject)snes)->tablevel);CHKERRQ(ierr);
3807       if (snes->reason > 0) {
3808         ierr = PetscViewerASCIIPrintf(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)),"Nonlinear solve converged due to %s iterations %D\n",SNESConvergedReasons[snes->reason],snes->iter);CHKERRQ(ierr);
3809       } else {
3810         ierr = PetscViewerASCIIPrintf(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)),"Nonlinear solve did not converge due to %s iterations %D\n",SNESConvergedReasons[snes->reason],snes->iter);CHKERRQ(ierr);
3811       }
3812       ierr = PetscViewerASCIISubtractTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)),((PetscObject)snes)->tablevel);CHKERRQ(ierr);
3813     }
3814 
3815     if (snes->errorifnotconverged && snes->reason < 0) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_NOT_CONVERGED,"SNESSolve has not converged");
3816     if (grid <  snes->gridsequence) {
3817       DM  fine;
3818       Vec xnew;
3819       Mat interp;
3820 
3821       ierr = DMRefine(snes->dm,PetscObjectComm((PetscObject)snes),&fine);CHKERRQ(ierr);
3822       if (!fine) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_INCOMP,"DMRefine() did not perform any refinement, cannot continue grid sequencing");
3823       ierr = DMCreateInterpolation(snes->dm,fine,&interp,NULL);CHKERRQ(ierr);
3824       ierr = DMCreateGlobalVector(fine,&xnew);CHKERRQ(ierr);
3825       ierr = MatInterpolate(interp,x,xnew);CHKERRQ(ierr);
3826       ierr = DMInterpolate(snes->dm,interp,fine);CHKERRQ(ierr);
3827       ierr = MatDestroy(&interp);CHKERRQ(ierr);
3828       x    = xnew;
3829 
3830       ierr = SNESReset(snes);CHKERRQ(ierr);
3831       ierr = SNESSetDM(snes,fine);CHKERRQ(ierr);
3832       ierr = DMDestroy(&fine);CHKERRQ(ierr);
3833       ierr = PetscViewerASCIIPopTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)));CHKERRQ(ierr);
3834     }
3835   }
3836   /* monitoring and viewing */
3837   ierr = PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->prefix,"-snes_view",&viewer,&format,&flg);CHKERRQ(ierr);
3838   if (flg && !PetscPreLoadingOn) {
3839     ierr = PetscViewerPushFormat(viewer,format);CHKERRQ(ierr);
3840     ierr = SNESView(snes,viewer);CHKERRQ(ierr);
3841     ierr = PetscViewerPopFormat(viewer);CHKERRQ(ierr);
3842     ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
3843   }
3844   ierr = VecViewFromOptions(snes->vec_sol,((PetscObject)snes)->prefix,"-snes_view_solution");CHKERRQ(ierr);
3845 
3846   ierr = VecDestroy(&xcreated);CHKERRQ(ierr);
3847   ierr = PetscObjectAMSBlock((PetscObject)snes);CHKERRQ(ierr);
3848   PetscFunctionReturn(0);
3849 }
3850 
3851 /* --------- Internal routines for SNES Package --------- */
3852 
3853 #undef __FUNCT__
3854 #define __FUNCT__ "SNESSetType"
3855 /*@C
3856    SNESSetType - Sets the method for the nonlinear solver.
3857 
3858    Collective on SNES
3859 
3860    Input Parameters:
3861 +  snes - the SNES context
3862 -  type - a known method
3863 
3864    Options Database Key:
3865 .  -snes_type <type> - Sets the method; use -help for a list
3866    of available methods (for instance, newtonls or newtontr)
3867 
3868    Notes:
3869    See "petsc/include/petscsnes.h" for available methods (for instance)
3870 +    SNESNEWTONLS - Newton's method with line search
3871      (systems of nonlinear equations)
3872 .    SNESNEWTONTR - Newton's method with trust region
3873      (systems of nonlinear equations)
3874 
3875   Normally, it is best to use the SNESSetFromOptions() command and then
3876   set the SNES solver type from the options database rather than by using
3877   this routine.  Using the options database provides the user with
3878   maximum flexibility in evaluating the many nonlinear solvers.
3879   The SNESSetType() routine is provided for those situations where it
3880   is necessary to set the nonlinear solver independently of the command
3881   line or options database.  This might be the case, for example, when
3882   the choice of solver changes during the execution of the program,
3883   and the user's application is taking responsibility for choosing the
3884   appropriate method.
3885 
3886     Developer Notes: SNESRegister() adds a constructor for a new SNESType to SNESList, SNESSetType() locates
3887     the constructor in that list and calls it to create the spexific object.
3888 
3889   Level: intermediate
3890 
3891 .keywords: SNES, set, type
3892 
3893 .seealso: SNESType, SNESCreate(), SNESDestroy(), SNESGetType(), SNESSetFromOptions()
3894 
3895 @*/
3896 PetscErrorCode  SNESSetType(SNES snes,SNESType type)
3897 {
3898   PetscErrorCode ierr,(*r)(SNES);
3899   PetscBool      match;
3900 
3901   PetscFunctionBegin;
3902   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3903   PetscValidCharPointer(type,2);
3904 
3905   ierr = PetscObjectTypeCompare((PetscObject)snes,type,&match);CHKERRQ(ierr);
3906   if (match) PetscFunctionReturn(0);
3907 
3908   ierr =  PetscFunctionListFind(SNESList,type,&r);CHKERRQ(ierr);
3909   if (!r) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_UNKNOWN_TYPE,"Unable to find requested SNES type %s",type);
3910   /* Destroy the previous private SNES context */
3911   if (snes->ops->destroy) {
3912     ierr               = (*(snes)->ops->destroy)(snes);CHKERRQ(ierr);
3913     snes->ops->destroy = NULL;
3914   }
3915   /* Reinitialize function pointers in SNESOps structure */
3916   snes->ops->setup          = 0;
3917   snes->ops->solve          = 0;
3918   snes->ops->view           = 0;
3919   snes->ops->setfromoptions = 0;
3920   snes->ops->destroy        = 0;
3921   /* Call the SNESCreate_XXX routine for this particular Nonlinear solver */
3922   snes->setupcalled = PETSC_FALSE;
3923 
3924   ierr = PetscObjectChangeTypeName((PetscObject)snes,type);CHKERRQ(ierr);
3925   ierr = (*r)(snes);CHKERRQ(ierr);
3926   PetscFunctionReturn(0);
3927 }
3928 
3929 #undef __FUNCT__
3930 #define __FUNCT__ "SNESGetType"
3931 /*@C
3932    SNESGetType - Gets the SNES method type and name (as a string).
3933 
3934    Not Collective
3935 
3936    Input Parameter:
3937 .  snes - nonlinear solver context
3938 
3939    Output Parameter:
3940 .  type - SNES method (a character string)
3941 
3942    Level: intermediate
3943 
3944 .keywords: SNES, nonlinear, get, type, name
3945 @*/
3946 PetscErrorCode  SNESGetType(SNES snes,SNESType *type)
3947 {
3948   PetscFunctionBegin;
3949   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3950   PetscValidPointer(type,2);
3951   *type = ((PetscObject)snes)->type_name;
3952   PetscFunctionReturn(0);
3953 }
3954 
3955 #undef __FUNCT__
3956 #define __FUNCT__ "SNESGetSolution"
3957 /*@
3958    SNESGetSolution - Returns the vector where the approximate solution is
3959    stored. This is the fine grid solution when using SNESSetGridSequence().
3960 
3961    Not Collective, but Vec is parallel if SNES is parallel
3962 
3963    Input Parameter:
3964 .  snes - the SNES context
3965 
3966    Output Parameter:
3967 .  x - the solution
3968 
3969    Level: intermediate
3970 
3971 .keywords: SNES, nonlinear, get, solution
3972 
3973 .seealso:  SNESGetSolutionUpdate(), SNESGetFunction()
3974 @*/
3975 PetscErrorCode  SNESGetSolution(SNES snes,Vec *x)
3976 {
3977   PetscFunctionBegin;
3978   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3979   PetscValidPointer(x,2);
3980   *x = snes->vec_sol;
3981   PetscFunctionReturn(0);
3982 }
3983 
3984 #undef __FUNCT__
3985 #define __FUNCT__ "SNESGetSolutionUpdate"
3986 /*@
3987    SNESGetSolutionUpdate - Returns the vector where the solution update is
3988    stored.
3989 
3990    Not Collective, but Vec is parallel if SNES is parallel
3991 
3992    Input Parameter:
3993 .  snes - the SNES context
3994 
3995    Output Parameter:
3996 .  x - the solution update
3997 
3998    Level: advanced
3999 
4000 .keywords: SNES, nonlinear, get, solution, update
4001 
4002 .seealso: SNESGetSolution(), SNESGetFunction()
4003 @*/
4004 PetscErrorCode  SNESGetSolutionUpdate(SNES snes,Vec *x)
4005 {
4006   PetscFunctionBegin;
4007   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4008   PetscValidPointer(x,2);
4009   *x = snes->vec_sol_update;
4010   PetscFunctionReturn(0);
4011 }
4012 
4013 #undef __FUNCT__
4014 #define __FUNCT__ "SNESGetFunction"
4015 /*@C
4016    SNESGetFunction - Returns the vector where the function is stored.
4017 
4018    Not Collective, but Vec is parallel if SNES is parallel. Collective if Vec is requested, but has not been created yet.
4019 
4020    Input Parameter:
4021 .  snes - the SNES context
4022 
4023    Output Parameter:
4024 +  r - the vector that is used to store residuals (or NULL if you don't want it)
4025 .  SNESFunction- the function (or NULL if you don't want it)
4026 -  ctx - the function context (or NULL if you don't want it)
4027 
4028    Level: advanced
4029 
4030 .keywords: SNES, nonlinear, get, function
4031 
4032 .seealso: SNESSetFunction(), SNESGetSolution(), SNESFunction
4033 @*/
4034 PetscErrorCode  SNESGetFunction(SNES snes,Vec *r,PetscErrorCode (**SNESFunction)(SNES,Vec,Vec,void*),void **ctx)
4035 {
4036   PetscErrorCode ierr;
4037   DM             dm;
4038 
4039   PetscFunctionBegin;
4040   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4041   if (r) {
4042     if (!snes->vec_func) {
4043       if (snes->vec_rhs) {
4044         ierr = VecDuplicate(snes->vec_rhs,&snes->vec_func);CHKERRQ(ierr);
4045       } else if (snes->vec_sol) {
4046         ierr = VecDuplicate(snes->vec_sol,&snes->vec_func);CHKERRQ(ierr);
4047       } else if (snes->dm) {
4048         ierr = DMCreateGlobalVector(snes->dm,&snes->vec_func);CHKERRQ(ierr);
4049       }
4050     }
4051     *r = snes->vec_func;
4052   }
4053   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
4054   ierr = DMSNESGetFunction(dm,SNESFunction,ctx);CHKERRQ(ierr);
4055   PetscFunctionReturn(0);
4056 }
4057 
4058 /*@C
4059    SNESGetGS - Returns the GS function and context.
4060 
4061    Input Parameter:
4062 .  snes - the SNES context
4063 
4064    Output Parameter:
4065 +  SNESGSFunction - the function (or NULL)
4066 -  ctx    - the function context (or NULL)
4067 
4068    Level: advanced
4069 
4070 .keywords: SNES, nonlinear, get, function
4071 
4072 .seealso: SNESSetGS(), SNESGetFunction()
4073 @*/
4074 
4075 #undef __FUNCT__
4076 #define __FUNCT__ "SNESGetGS"
4077 PetscErrorCode SNESGetGS (SNES snes, PetscErrorCode (**SNESGSFunction)(SNES, Vec, Vec, void*), void ** ctx)
4078 {
4079   PetscErrorCode ierr;
4080   DM             dm;
4081 
4082   PetscFunctionBegin;
4083   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4084   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
4085   ierr = DMSNESGetGS(dm,SNESGSFunction,ctx);CHKERRQ(ierr);
4086   PetscFunctionReturn(0);
4087 }
4088 
4089 #undef __FUNCT__
4090 #define __FUNCT__ "SNESSetOptionsPrefix"
4091 /*@C
4092    SNESSetOptionsPrefix - Sets the prefix used for searching for all
4093    SNES options in the database.
4094 
4095    Logically Collective on SNES
4096 
4097    Input Parameter:
4098 +  snes - the SNES context
4099 -  prefix - the prefix to prepend to all option names
4100 
4101    Notes:
4102    A hyphen (-) must NOT be given at the beginning of the prefix name.
4103    The first character of all runtime options is AUTOMATICALLY the hyphen.
4104 
4105    Level: advanced
4106 
4107 .keywords: SNES, set, options, prefix, database
4108 
4109 .seealso: SNESSetFromOptions()
4110 @*/
4111 PetscErrorCode  SNESSetOptionsPrefix(SNES snes,const char prefix[])
4112 {
4113   PetscErrorCode ierr;
4114 
4115   PetscFunctionBegin;
4116   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4117   ierr = PetscObjectSetOptionsPrefix((PetscObject)snes,prefix);CHKERRQ(ierr);
4118   if (!snes->ksp) {ierr = SNESGetKSP(snes,&snes->ksp);CHKERRQ(ierr);}
4119   if (snes->linesearch) {
4120     ierr = SNESGetLineSearch(snes,&snes->linesearch);CHKERRQ(ierr);
4121     ierr = PetscObjectSetOptionsPrefix((PetscObject)snes->linesearch,prefix);CHKERRQ(ierr);
4122   }
4123   ierr = KSPSetOptionsPrefix(snes->ksp,prefix);CHKERRQ(ierr);
4124   PetscFunctionReturn(0);
4125 }
4126 
4127 #undef __FUNCT__
4128 #define __FUNCT__ "SNESAppendOptionsPrefix"
4129 /*@C
4130    SNESAppendOptionsPrefix - Appends to the prefix used for searching for all
4131    SNES options in the database.
4132 
4133    Logically Collective on SNES
4134 
4135    Input Parameters:
4136 +  snes - the SNES context
4137 -  prefix - the prefix to prepend to all option names
4138 
4139    Notes:
4140    A hyphen (-) must NOT be given at the beginning of the prefix name.
4141    The first character of all runtime options is AUTOMATICALLY the hyphen.
4142 
4143    Level: advanced
4144 
4145 .keywords: SNES, append, options, prefix, database
4146 
4147 .seealso: SNESGetOptionsPrefix()
4148 @*/
4149 PetscErrorCode  SNESAppendOptionsPrefix(SNES snes,const char prefix[])
4150 {
4151   PetscErrorCode ierr;
4152 
4153   PetscFunctionBegin;
4154   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4155   ierr = PetscObjectAppendOptionsPrefix((PetscObject)snes,prefix);CHKERRQ(ierr);
4156   if (!snes->ksp) {ierr = SNESGetKSP(snes,&snes->ksp);CHKERRQ(ierr);}
4157   if (snes->linesearch) {
4158     ierr = SNESGetLineSearch(snes,&snes->linesearch);CHKERRQ(ierr);
4159     ierr = PetscObjectAppendOptionsPrefix((PetscObject)snes->linesearch,prefix);CHKERRQ(ierr);
4160   }
4161   ierr = KSPAppendOptionsPrefix(snes->ksp,prefix);CHKERRQ(ierr);
4162   PetscFunctionReturn(0);
4163 }
4164 
4165 #undef __FUNCT__
4166 #define __FUNCT__ "SNESGetOptionsPrefix"
4167 /*@C
4168    SNESGetOptionsPrefix - Sets the prefix used for searching for all
4169    SNES options in the database.
4170 
4171    Not Collective
4172 
4173    Input Parameter:
4174 .  snes - the SNES context
4175 
4176    Output Parameter:
4177 .  prefix - pointer to the prefix string used
4178 
4179    Notes: On the fortran side, the user should pass in a string 'prefix' of
4180    sufficient length to hold the prefix.
4181 
4182    Level: advanced
4183 
4184 .keywords: SNES, get, options, prefix, database
4185 
4186 .seealso: SNESAppendOptionsPrefix()
4187 @*/
4188 PetscErrorCode  SNESGetOptionsPrefix(SNES snes,const char *prefix[])
4189 {
4190   PetscErrorCode ierr;
4191 
4192   PetscFunctionBegin;
4193   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4194   ierr = PetscObjectGetOptionsPrefix((PetscObject)snes,prefix);CHKERRQ(ierr);
4195   PetscFunctionReturn(0);
4196 }
4197 
4198 
4199 #undef __FUNCT__
4200 #define __FUNCT__ "SNESRegister"
4201 /*@C
4202   SNESRegister - Adds a method to the nonlinear solver package.
4203 
4204    Not collective
4205 
4206    Input Parameters:
4207 +  name_solver - name of a new user-defined solver
4208 -  routine_create - routine to create method context
4209 
4210    Notes:
4211    SNESRegister() may be called multiple times to add several user-defined solvers.
4212 
4213    Sample usage:
4214 .vb
4215    SNESRegister("my_solver",MySolverCreate);
4216 .ve
4217 
4218    Then, your solver can be chosen with the procedural interface via
4219 $     SNESSetType(snes,"my_solver")
4220    or at runtime via the option
4221 $     -snes_type my_solver
4222 
4223    Level: advanced
4224 
4225     Note: If your function is not being put into a shared library then use SNESRegister() instead
4226 
4227 .keywords: SNES, nonlinear, register
4228 
4229 .seealso: SNESRegisterAll(), SNESRegisterDestroy()
4230 
4231   Level: advanced
4232 @*/
4233 PetscErrorCode  SNESRegister(const char sname[],PetscErrorCode (*function)(SNES))
4234 {
4235   PetscErrorCode ierr;
4236 
4237   PetscFunctionBegin;
4238   ierr = PetscFunctionListAdd(&SNESList,sname,function);CHKERRQ(ierr);
4239   PetscFunctionReturn(0);
4240 }
4241 
4242 #undef __FUNCT__
4243 #define __FUNCT__ "SNESTestLocalMin"
4244 PetscErrorCode  SNESTestLocalMin(SNES snes)
4245 {
4246   PetscErrorCode ierr;
4247   PetscInt       N,i,j;
4248   Vec            u,uh,fh;
4249   PetscScalar    value;
4250   PetscReal      norm;
4251 
4252   PetscFunctionBegin;
4253   ierr = SNESGetSolution(snes,&u);CHKERRQ(ierr);
4254   ierr = VecDuplicate(u,&uh);CHKERRQ(ierr);
4255   ierr = VecDuplicate(u,&fh);CHKERRQ(ierr);
4256 
4257   /* currently only works for sequential */
4258   ierr = PetscPrintf(PETSC_COMM_WORLD,"Testing FormFunction() for local min\n");CHKERRQ(ierr);
4259   ierr = VecGetSize(u,&N);CHKERRQ(ierr);
4260   for (i=0; i<N; i++) {
4261     ierr = VecCopy(u,uh);CHKERRQ(ierr);
4262     ierr = PetscPrintf(PETSC_COMM_WORLD,"i = %D\n",i);CHKERRQ(ierr);
4263     for (j=-10; j<11; j++) {
4264       value = PetscSign(j)*exp(PetscAbs(j)-10.0);
4265       ierr  = VecSetValue(uh,i,value,ADD_VALUES);CHKERRQ(ierr);
4266       ierr  = SNESComputeFunction(snes,uh,fh);CHKERRQ(ierr);
4267       ierr  = VecNorm(fh,NORM_2,&norm);CHKERRQ(ierr);
4268       ierr  = PetscPrintf(PETSC_COMM_WORLD,"       j norm %D %18.16e\n",j,norm);CHKERRQ(ierr);
4269       value = -value;
4270       ierr  = VecSetValue(uh,i,value,ADD_VALUES);CHKERRQ(ierr);
4271     }
4272   }
4273   ierr = VecDestroy(&uh);CHKERRQ(ierr);
4274   ierr = VecDestroy(&fh);CHKERRQ(ierr);
4275   PetscFunctionReturn(0);
4276 }
4277 
4278 #undef __FUNCT__
4279 #define __FUNCT__ "SNESKSPSetUseEW"
4280 /*@
4281    SNESKSPSetUseEW - Sets SNES use Eisenstat-Walker method for
4282    computing relative tolerance for linear solvers within an inexact
4283    Newton method.
4284 
4285    Logically Collective on SNES
4286 
4287    Input Parameters:
4288 +  snes - SNES context
4289 -  flag - PETSC_TRUE or PETSC_FALSE
4290 
4291     Options Database:
4292 +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
4293 .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
4294 .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
4295 .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
4296 .  -snes_ksp_ew_gamma <gamma> - Sets gamma
4297 .  -snes_ksp_ew_alpha <alpha> - Sets alpha
4298 .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
4299 -  -snes_ksp_ew_threshold <threshold> - Sets threshold
4300 
4301    Notes:
4302    Currently, the default is to use a constant relative tolerance for
4303    the inner linear solvers.  Alternatively, one can use the
4304    Eisenstat-Walker method, where the relative convergence tolerance
4305    is reset at each Newton iteration according progress of the nonlinear
4306    solver.
4307 
4308    Level: advanced
4309 
4310    Reference:
4311    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
4312    inexact Newton method", SISC 17 (1), pp.16-32, 1996.
4313 
4314 .keywords: SNES, KSP, Eisenstat, Walker, convergence, test, inexact, Newton
4315 
4316 .seealso: SNESKSPGetUseEW(), SNESKSPGetParametersEW(), SNESKSPSetParametersEW()
4317 @*/
4318 PetscErrorCode  SNESKSPSetUseEW(SNES snes,PetscBool flag)
4319 {
4320   PetscFunctionBegin;
4321   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4322   PetscValidLogicalCollectiveBool(snes,flag,2);
4323   snes->ksp_ewconv = flag;
4324   PetscFunctionReturn(0);
4325 }
4326 
4327 #undef __FUNCT__
4328 #define __FUNCT__ "SNESKSPGetUseEW"
4329 /*@
4330    SNESKSPGetUseEW - Gets if SNES is using Eisenstat-Walker method
4331    for computing relative tolerance for linear solvers within an
4332    inexact Newton method.
4333 
4334    Not Collective
4335 
4336    Input Parameter:
4337 .  snes - SNES context
4338 
4339    Output Parameter:
4340 .  flag - PETSC_TRUE or PETSC_FALSE
4341 
4342    Notes:
4343    Currently, the default is to use a constant relative tolerance for
4344    the inner linear solvers.  Alternatively, one can use the
4345    Eisenstat-Walker method, where the relative convergence tolerance
4346    is reset at each Newton iteration according progress of the nonlinear
4347    solver.
4348 
4349    Level: advanced
4350 
4351    Reference:
4352    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
4353    inexact Newton method", SISC 17 (1), pp.16-32, 1996.
4354 
4355 .keywords: SNES, KSP, Eisenstat, Walker, convergence, test, inexact, Newton
4356 
4357 .seealso: SNESKSPSetUseEW(), SNESKSPGetParametersEW(), SNESKSPSetParametersEW()
4358 @*/
4359 PetscErrorCode  SNESKSPGetUseEW(SNES snes, PetscBool  *flag)
4360 {
4361   PetscFunctionBegin;
4362   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4363   PetscValidPointer(flag,2);
4364   *flag = snes->ksp_ewconv;
4365   PetscFunctionReturn(0);
4366 }
4367 
4368 #undef __FUNCT__
4369 #define __FUNCT__ "SNESKSPSetParametersEW"
4370 /*@
4371    SNESKSPSetParametersEW - Sets parameters for Eisenstat-Walker
4372    convergence criteria for the linear solvers within an inexact
4373    Newton method.
4374 
4375    Logically Collective on SNES
4376 
4377    Input Parameters:
4378 +    snes - SNES context
4379 .    version - version 1, 2 (default is 2) or 3
4380 .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
4381 .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
4382 .    gamma - multiplicative factor for version 2 rtol computation
4383              (0 <= gamma2 <= 1)
4384 .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
4385 .    alpha2 - power for safeguard
4386 -    threshold - threshold for imposing safeguard (0 < threshold < 1)
4387 
4388    Note:
4389    Version 3 was contributed by Luis Chacon, June 2006.
4390 
4391    Use PETSC_DEFAULT to retain the default for any of the parameters.
4392 
4393    Level: advanced
4394 
4395    Reference:
4396    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
4397    inexact Newton method", Utah State University Math. Stat. Dept. Res.
4398    Report 6/94/75, June, 1994, to appear in SIAM J. Sci. Comput.
4399 
4400 .keywords: SNES, KSP, Eisenstat, Walker, set, parameters
4401 
4402 .seealso: SNESKSPSetUseEW(), SNESKSPGetUseEW(), SNESKSPGetParametersEW()
4403 @*/
4404 PetscErrorCode  SNESKSPSetParametersEW(SNES snes,PetscInt version,PetscReal rtol_0,PetscReal rtol_max,PetscReal gamma,PetscReal alpha,PetscReal alpha2,PetscReal threshold)
4405 {
4406   SNESKSPEW *kctx;
4407 
4408   PetscFunctionBegin;
4409   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4410   kctx = (SNESKSPEW*)snes->kspconvctx;
4411   if (!kctx) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"No Eisenstat-Walker context existing");
4412   PetscValidLogicalCollectiveInt(snes,version,2);
4413   PetscValidLogicalCollectiveReal(snes,rtol_0,3);
4414   PetscValidLogicalCollectiveReal(snes,rtol_max,4);
4415   PetscValidLogicalCollectiveReal(snes,gamma,5);
4416   PetscValidLogicalCollectiveReal(snes,alpha,6);
4417   PetscValidLogicalCollectiveReal(snes,alpha2,7);
4418   PetscValidLogicalCollectiveReal(snes,threshold,8);
4419 
4420   if (version != PETSC_DEFAULT)   kctx->version   = version;
4421   if (rtol_0 != PETSC_DEFAULT)    kctx->rtol_0    = rtol_0;
4422   if (rtol_max != PETSC_DEFAULT)  kctx->rtol_max  = rtol_max;
4423   if (gamma != PETSC_DEFAULT)     kctx->gamma     = gamma;
4424   if (alpha != PETSC_DEFAULT)     kctx->alpha     = alpha;
4425   if (alpha2 != PETSC_DEFAULT)    kctx->alpha2    = alpha2;
4426   if (threshold != PETSC_DEFAULT) kctx->threshold = threshold;
4427 
4428   if (kctx->version < 1 || kctx->version > 3) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Only versions 1, 2 and 3 are supported: %D",kctx->version);
4429   if (kctx->rtol_0 < 0.0 || kctx->rtol_0 >= 1.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"0.0 <= rtol_0 < 1.0: %G",kctx->rtol_0);
4430   if (kctx->rtol_max < 0.0 || kctx->rtol_max >= 1.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"0.0 <= rtol_max (%G) < 1.0\n",kctx->rtol_max);
4431   if (kctx->gamma < 0.0 || kctx->gamma > 1.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"0.0 <= gamma (%G) <= 1.0\n",kctx->gamma);
4432   if (kctx->alpha <= 1.0 || kctx->alpha > 2.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"1.0 < alpha (%G) <= 2.0\n",kctx->alpha);
4433   if (kctx->threshold <= 0.0 || kctx->threshold >= 1.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"0.0 < threshold (%G) < 1.0\n",kctx->threshold);
4434   PetscFunctionReturn(0);
4435 }
4436 
4437 #undef __FUNCT__
4438 #define __FUNCT__ "SNESKSPGetParametersEW"
4439 /*@
4440    SNESKSPGetParametersEW - Gets parameters for Eisenstat-Walker
4441    convergence criteria for the linear solvers within an inexact
4442    Newton method.
4443 
4444    Not Collective
4445 
4446    Input Parameters:
4447      snes - SNES context
4448 
4449    Output Parameters:
4450 +    version - version 1, 2 (default is 2) or 3
4451 .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
4452 .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
4453 .    gamma - multiplicative factor for version 2 rtol computation (0 <= gamma2 <= 1)
4454 .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
4455 .    alpha2 - power for safeguard
4456 -    threshold - threshold for imposing safeguard (0 < threshold < 1)
4457 
4458    Level: advanced
4459 
4460 .keywords: SNES, KSP, Eisenstat, Walker, get, parameters
4461 
4462 .seealso: SNESKSPSetUseEW(), SNESKSPGetUseEW(), SNESKSPSetParametersEW()
4463 @*/
4464 PetscErrorCode  SNESKSPGetParametersEW(SNES snes,PetscInt *version,PetscReal *rtol_0,PetscReal *rtol_max,PetscReal *gamma,PetscReal *alpha,PetscReal *alpha2,PetscReal *threshold)
4465 {
4466   SNESKSPEW *kctx;
4467 
4468   PetscFunctionBegin;
4469   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4470   kctx = (SNESKSPEW*)snes->kspconvctx;
4471   if (!kctx) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"No Eisenstat-Walker context existing");
4472   if (version)   *version   = kctx->version;
4473   if (rtol_0)    *rtol_0    = kctx->rtol_0;
4474   if (rtol_max)  *rtol_max  = kctx->rtol_max;
4475   if (gamma)     *gamma     = kctx->gamma;
4476   if (alpha)     *alpha     = kctx->alpha;
4477   if (alpha2)    *alpha2    = kctx->alpha2;
4478   if (threshold) *threshold = kctx->threshold;
4479   PetscFunctionReturn(0);
4480 }
4481 
4482 #undef __FUNCT__
4483 #define __FUNCT__ "KSPPreSolve_SNESEW"
4484  PetscErrorCode KSPPreSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
4485 {
4486   PetscErrorCode ierr;
4487   SNESKSPEW      *kctx = (SNESKSPEW*)snes->kspconvctx;
4488   PetscReal      rtol  = PETSC_DEFAULT,stol;
4489 
4490   PetscFunctionBegin;
4491   if (!snes->ksp_ewconv) PetscFunctionReturn(0);
4492   if (!snes->iter) {
4493     rtol = kctx->rtol_0; /* first time in, so use the original user rtol */
4494     ierr = VecNorm(snes->vec_func,NORM_2,&kctx->norm_first);CHKERRQ(ierr);
4495   }
4496   else {
4497     if (kctx->version == 1) {
4498       rtol = (snes->norm - kctx->lresid_last)/kctx->norm_last;
4499       if (rtol < 0.0) rtol = -rtol;
4500       stol = PetscPowReal(kctx->rtol_last,kctx->alpha2);
4501       if (stol > kctx->threshold) rtol = PetscMax(rtol,stol);
4502     } else if (kctx->version == 2) {
4503       rtol = kctx->gamma * PetscPowReal(snes->norm/kctx->norm_last,kctx->alpha);
4504       stol = kctx->gamma * PetscPowReal(kctx->rtol_last,kctx->alpha);
4505       if (stol > kctx->threshold) rtol = PetscMax(rtol,stol);
4506     } else if (kctx->version == 3) { /* contributed by Luis Chacon, June 2006. */
4507       rtol = kctx->gamma * PetscPowReal(snes->norm/kctx->norm_last,kctx->alpha);
4508       /* safeguard: avoid sharp decrease of rtol */
4509       stol = kctx->gamma*PetscPowReal(kctx->rtol_last,kctx->alpha);
4510       stol = PetscMax(rtol,stol);
4511       rtol = PetscMin(kctx->rtol_0,stol);
4512       /* safeguard: avoid oversolving */
4513       stol = kctx->gamma*(kctx->norm_first*snes->rtol)/snes->norm;
4514       stol = PetscMax(rtol,stol);
4515       rtol = PetscMin(kctx->rtol_0,stol);
4516     } else SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Only versions 1, 2 or 3 are supported: %D",kctx->version);
4517   }
4518   /* safeguard: avoid rtol greater than one */
4519   rtol = PetscMin(rtol,kctx->rtol_max);
4520   ierr = KSPSetTolerances(ksp,rtol,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);CHKERRQ(ierr);
4521   ierr = PetscInfo3(snes,"iter %D, Eisenstat-Walker (version %D) KSP rtol=%G\n",snes->iter,kctx->version,rtol);CHKERRQ(ierr);
4522   PetscFunctionReturn(0);
4523 }
4524 
4525 #undef __FUNCT__
4526 #define __FUNCT__ "KSPPostSolve_SNESEW"
4527 PetscErrorCode KSPPostSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
4528 {
4529   PetscErrorCode ierr;
4530   SNESKSPEW      *kctx = (SNESKSPEW*)snes->kspconvctx;
4531   PCSide         pcside;
4532   Vec            lres;
4533 
4534   PetscFunctionBegin;
4535   if (!snes->ksp_ewconv) PetscFunctionReturn(0);
4536   ierr = KSPGetTolerances(ksp,&kctx->rtol_last,0,0,0);CHKERRQ(ierr);
4537   ierr = SNESGetFunctionNorm(snes,&kctx->norm_last);CHKERRQ(ierr);
4538   if (kctx->version == 1) {
4539     ierr = KSPGetPCSide(ksp,&pcside);CHKERRQ(ierr);
4540     if (pcside == PC_RIGHT) { /* XXX Should we also test KSP_UNPRECONDITIONED_NORM ? */
4541       /* KSP residual is true linear residual */
4542       ierr = KSPGetResidualNorm(ksp,&kctx->lresid_last);CHKERRQ(ierr);
4543     } else {
4544       /* KSP residual is preconditioned residual */
4545       /* compute true linear residual norm */
4546       ierr = VecDuplicate(b,&lres);CHKERRQ(ierr);
4547       ierr = MatMult(snes->jacobian,x,lres);CHKERRQ(ierr);
4548       ierr = VecAYPX(lres,-1.0,b);CHKERRQ(ierr);
4549       ierr = VecNorm(lres,NORM_2,&kctx->lresid_last);CHKERRQ(ierr);
4550       ierr = VecDestroy(&lres);CHKERRQ(ierr);
4551     }
4552   }
4553   PetscFunctionReturn(0);
4554 }
4555 
4556 #undef __FUNCT__
4557 #define __FUNCT__ "SNESGetKSP"
4558 /*@
4559    SNESGetKSP - Returns the KSP context for a SNES solver.
4560 
4561    Not Collective, but if SNES object is parallel, then KSP object is parallel
4562 
4563    Input Parameter:
4564 .  snes - the SNES context
4565 
4566    Output Parameter:
4567 .  ksp - the KSP context
4568 
4569    Notes:
4570    The user can then directly manipulate the KSP context to set various
4571    options, etc.  Likewise, the user can then extract and manipulate the
4572    PC contexts as well.
4573 
4574    Level: beginner
4575 
4576 .keywords: SNES, nonlinear, get, KSP, context
4577 
4578 .seealso: KSPGetPC(), SNESCreate(), KSPCreate(), SNESSetKSP()
4579 @*/
4580 PetscErrorCode  SNESGetKSP(SNES snes,KSP *ksp)
4581 {
4582   PetscErrorCode ierr;
4583 
4584   PetscFunctionBegin;
4585   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4586   PetscValidPointer(ksp,2);
4587 
4588   if (!snes->ksp) {
4589     ierr = KSPCreate(PetscObjectComm((PetscObject)snes),&snes->ksp);CHKERRQ(ierr);
4590     ierr = PetscObjectIncrementTabLevel((PetscObject)snes->ksp,(PetscObject)snes,1);CHKERRQ(ierr);
4591     ierr = PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->ksp);CHKERRQ(ierr);
4592 
4593     ierr = KSPSetPreSolve(snes->ksp,(PetscErrorCode (*)(KSP,Vec,Vec,void*))KSPPreSolve_SNESEW,snes);CHKERRQ(ierr);
4594     ierr = KSPSetPostSolve(snes->ksp,(PetscErrorCode (*)(KSP,Vec,Vec,void*))KSPPostSolve_SNESEW,snes);CHKERRQ(ierr);
4595   }
4596   *ksp = snes->ksp;
4597   PetscFunctionReturn(0);
4598 }
4599 
4600 
4601 #include <petsc-private/dmimpl.h>
4602 #undef __FUNCT__
4603 #define __FUNCT__ "SNESSetDM"
4604 /*@
4605    SNESSetDM - Sets the DM that may be used by some preconditioners
4606 
4607    Logically Collective on SNES
4608 
4609    Input Parameters:
4610 +  snes - the preconditioner context
4611 -  dm - the dm
4612 
4613    Level: intermediate
4614 
4615 .seealso: SNESGetDM(), KSPSetDM(), KSPGetDM()
4616 @*/
4617 PetscErrorCode  SNESSetDM(SNES snes,DM dm)
4618 {
4619   PetscErrorCode ierr;
4620   KSP            ksp;
4621   DMSNES         sdm;
4622 
4623   PetscFunctionBegin;
4624   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4625   if (dm) {ierr = PetscObjectReference((PetscObject)dm);CHKERRQ(ierr);}
4626   if (snes->dm) {               /* Move the DMSNES context over to the new DM unless the new DM already has one */
4627     if (snes->dm->dmsnes && snes->dmAuto && !dm->dmsnes) {
4628       ierr = DMCopyDMSNES(snes->dm,dm);CHKERRQ(ierr);
4629       ierr = DMGetDMSNES(snes->dm,&sdm);CHKERRQ(ierr);
4630       if (sdm->originaldm == snes->dm) sdm->originaldm = dm; /* Grant write privileges to the replacement DM */
4631     }
4632     ierr = DMDestroy(&snes->dm);CHKERRQ(ierr);
4633   }
4634   snes->dm     = dm;
4635   snes->dmAuto = PETSC_FALSE;
4636 
4637   ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
4638   ierr = KSPSetDM(ksp,dm);CHKERRQ(ierr);
4639   ierr = KSPSetDMActive(ksp,PETSC_FALSE);CHKERRQ(ierr);
4640   if (snes->pc) {
4641     ierr = SNESSetDM(snes->pc, snes->dm);CHKERRQ(ierr);
4642     ierr = SNESSetPCSide(snes,snes->pcside);CHKERRQ(ierr);
4643   }
4644   PetscFunctionReturn(0);
4645 }
4646 
4647 #undef __FUNCT__
4648 #define __FUNCT__ "SNESGetDM"
4649 /*@
4650    SNESGetDM - Gets the DM that may be used by some preconditioners
4651 
4652    Not Collective but DM obtained is parallel on SNES
4653 
4654    Input Parameter:
4655 . snes - the preconditioner context
4656 
4657    Output Parameter:
4658 .  dm - the dm
4659 
4660    Level: intermediate
4661 
4662 .seealso: SNESSetDM(), KSPSetDM(), KSPGetDM()
4663 @*/
4664 PetscErrorCode  SNESGetDM(SNES snes,DM *dm)
4665 {
4666   PetscErrorCode ierr;
4667 
4668   PetscFunctionBegin;
4669   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4670   if (!snes->dm) {
4671     ierr         = DMShellCreate(PetscObjectComm((PetscObject)snes),&snes->dm);CHKERRQ(ierr);
4672     snes->dmAuto = PETSC_TRUE;
4673   }
4674   *dm = snes->dm;
4675   PetscFunctionReturn(0);
4676 }
4677 
4678 #undef __FUNCT__
4679 #define __FUNCT__ "SNESSetPC"
4680 /*@
4681   SNESSetPC - Sets the nonlinear preconditioner to be used.
4682 
4683   Collective on SNES
4684 
4685   Input Parameters:
4686 + snes - iterative context obtained from SNESCreate()
4687 - pc   - the preconditioner object
4688 
4689   Notes:
4690   Use SNESGetPC() to retrieve the preconditioner context (for example,
4691   to configure it using the API).
4692 
4693   Level: developer
4694 
4695 .keywords: SNES, set, precondition
4696 .seealso: SNESGetPC()
4697 @*/
4698 PetscErrorCode SNESSetPC(SNES snes, SNES pc)
4699 {
4700   PetscErrorCode ierr;
4701 
4702   PetscFunctionBegin;
4703   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4704   PetscValidHeaderSpecific(pc, SNES_CLASSID, 2);
4705   PetscCheckSameComm(snes, 1, pc, 2);
4706   ierr     = PetscObjectReference((PetscObject) pc);CHKERRQ(ierr);
4707   ierr     = SNESDestroy(&snes->pc);CHKERRQ(ierr);
4708   snes->pc = pc;
4709   ierr     = PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->pc);CHKERRQ(ierr);
4710   PetscFunctionReturn(0);
4711 }
4712 
4713 #undef __FUNCT__
4714 #define __FUNCT__ "SNESGetPC"
4715 /*@
4716   SNESGetPC - Returns a pointer to the nonlinear preconditioning context set with SNESSetPC().
4717 
4718   Not Collective
4719 
4720   Input Parameter:
4721 . snes - iterative context obtained from SNESCreate()
4722 
4723   Output Parameter:
4724 . pc - preconditioner context
4725 
4726   Level: developer
4727 
4728 .keywords: SNES, get, preconditioner
4729 .seealso: SNESSetPC()
4730 @*/
4731 PetscErrorCode SNESGetPC(SNES snes, SNES *pc)
4732 {
4733   PetscErrorCode ierr;
4734   const char     *optionsprefix;
4735 
4736   PetscFunctionBegin;
4737   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4738   PetscValidPointer(pc, 2);
4739   if (!snes->pc) {
4740     ierr = SNESCreate(PetscObjectComm((PetscObject)snes),&snes->pc);CHKERRQ(ierr);
4741     ierr = PetscObjectIncrementTabLevel((PetscObject)snes->pc,(PetscObject)snes,1);CHKERRQ(ierr);
4742     ierr = PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->pc);CHKERRQ(ierr);
4743     ierr = SNESGetOptionsPrefix(snes,&optionsprefix);CHKERRQ(ierr);
4744     ierr = SNESSetOptionsPrefix(snes->pc,optionsprefix);CHKERRQ(ierr);
4745     ierr = SNESAppendOptionsPrefix(snes->pc,"npc_");CHKERRQ(ierr);
4746     ierr = SNESSetCountersReset(snes->pc,PETSC_FALSE);CHKERRQ(ierr);
4747   }
4748   *pc = snes->pc;
4749   PetscFunctionReturn(0);
4750 }
4751 
4752 #undef __FUNCT__
4753 #define __FUNCT__ "SNESSetPCSide"
4754 /*@
4755     SNESSetPCSide - Sets the preconditioning side.
4756 
4757     Logically Collective on SNES
4758 
4759     Input Parameter:
4760 .   snes - iterative context obtained from SNESCreate()
4761 
4762     Output Parameter:
4763 .   side - the preconditioning side, where side is one of
4764 .vb
4765       PC_LEFT - left preconditioning (default)
4766       PC_RIGHT - right preconditioning
4767 .ve
4768 
4769     Options Database Keys:
4770 .   -snes_pc_side <right,left>
4771 
4772     Level: intermediate
4773 
4774 .keywords: SNES, set, right, left, side, preconditioner, flag
4775 
4776 .seealso: SNESGetPCSide(), KSPSetPCSide()
4777 @*/
4778 PetscErrorCode  SNESSetPCSide(SNES snes,PCSide side)
4779 {
4780   PetscFunctionBegin;
4781   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4782   PetscValidLogicalCollectiveEnum(snes,side,2);
4783   snes->pcside = side;
4784   PetscFunctionReturn(0);
4785 }
4786 
4787 #undef __FUNCT__
4788 #define __FUNCT__ "SNESGetPCSide"
4789 /*@
4790     SNESGetPCSide - Gets the preconditioning side.
4791 
4792     Not Collective
4793 
4794     Input Parameter:
4795 .   snes - iterative context obtained from SNESCreate()
4796 
4797     Output Parameter:
4798 .   side - the preconditioning side, where side is one of
4799 .vb
4800       PC_LEFT - left preconditioning (default)
4801       PC_RIGHT - right preconditioning
4802 .ve
4803 
4804     Level: intermediate
4805 
4806 .keywords: SNES, get, right, left, side, preconditioner, flag
4807 
4808 .seealso: SNESSetPCSide(), KSPGetPCSide()
4809 @*/
4810 PetscErrorCode  SNESGetPCSide(SNES snes,PCSide *side)
4811 {
4812   PetscFunctionBegin;
4813   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4814   PetscValidPointer(side,2);
4815   *side = snes->pcside;
4816   PetscFunctionReturn(0);
4817 }
4818 
4819 #undef __FUNCT__
4820 #define __FUNCT__ "SNESSetLineSearch"
4821 /*@
4822   SNESSetLineSearch - Sets the linesearch on the SNES instance.
4823 
4824   Collective on SNES
4825 
4826   Input Parameters:
4827 + snes - iterative context obtained from SNESCreate()
4828 - linesearch   - the linesearch object
4829 
4830   Notes:
4831   Use SNESGetLineSearch() to retrieve the preconditioner context (for example,
4832   to configure it using the API).
4833 
4834   Level: developer
4835 
4836 .keywords: SNES, set, linesearch
4837 .seealso: SNESGetLineSearch()
4838 @*/
4839 PetscErrorCode SNESSetLineSearch(SNES snes, SNESLineSearch linesearch)
4840 {
4841   PetscErrorCode ierr;
4842 
4843   PetscFunctionBegin;
4844   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4845   PetscValidHeaderSpecific(linesearch, SNESLINESEARCH_CLASSID, 2);
4846   PetscCheckSameComm(snes, 1, linesearch, 2);
4847   ierr = PetscObjectReference((PetscObject) linesearch);CHKERRQ(ierr);
4848   ierr = SNESLineSearchDestroy(&snes->linesearch);CHKERRQ(ierr);
4849 
4850   snes->linesearch = linesearch;
4851 
4852   ierr = PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->linesearch);CHKERRQ(ierr);
4853   PetscFunctionReturn(0);
4854 }
4855 
4856 #undef __FUNCT__
4857 #define __FUNCT__ "SNESGetLineSearch"
4858 /*@
4859   SNESGetLineSearch - Returns a pointer to the line search context set with SNESSetLineSearch()
4860   or creates a default line search instance associated with the SNES and returns it.
4861 
4862   Not Collective
4863 
4864   Input Parameter:
4865 . snes - iterative context obtained from SNESCreate()
4866 
4867   Output Parameter:
4868 . linesearch - linesearch context
4869 
4870   Level: developer
4871 
4872 .keywords: SNES, get, linesearch
4873 .seealso: SNESSetLineSearch()
4874 @*/
4875 PetscErrorCode SNESGetLineSearch(SNES snes, SNESLineSearch *linesearch)
4876 {
4877   PetscErrorCode ierr;
4878   const char     *optionsprefix;
4879 
4880   PetscFunctionBegin;
4881   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4882   PetscValidPointer(linesearch, 2);
4883   if (!snes->linesearch) {
4884     ierr = SNESGetOptionsPrefix(snes, &optionsprefix);CHKERRQ(ierr);
4885     ierr = SNESLineSearchCreate(PetscObjectComm((PetscObject)snes), &snes->linesearch);CHKERRQ(ierr);
4886     ierr = SNESLineSearchSetSNES(snes->linesearch, snes);CHKERRQ(ierr);
4887     ierr = SNESLineSearchAppendOptionsPrefix(snes->linesearch, optionsprefix);CHKERRQ(ierr);
4888     ierr = PetscObjectIncrementTabLevel((PetscObject) snes->linesearch, (PetscObject) snes, 1);CHKERRQ(ierr);
4889     ierr = PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->linesearch);CHKERRQ(ierr);
4890   }
4891   *linesearch = snes->linesearch;
4892   PetscFunctionReturn(0);
4893 }
4894 
4895 #if defined(PETSC_HAVE_MATLAB_ENGINE)
4896 #include <mex.h>
4897 
4898 typedef struct {char *funcname; mxArray *ctx;} SNESMatlabContext;
4899 
4900 #undef __FUNCT__
4901 #define __FUNCT__ "SNESComputeFunction_Matlab"
4902 /*
4903    SNESComputeFunction_Matlab - Calls the function that has been set with SNESSetFunctionMatlab().
4904 
4905    Collective on SNES
4906 
4907    Input Parameters:
4908 +  snes - the SNES context
4909 -  x - input vector
4910 
4911    Output Parameter:
4912 .  y - function vector, as set by SNESSetFunction()
4913 
4914    Notes:
4915    SNESComputeFunction() is typically used within nonlinear solvers
4916    implementations, so most users would not generally call this routine
4917    themselves.
4918 
4919    Level: developer
4920 
4921 .keywords: SNES, nonlinear, compute, function
4922 
4923 .seealso: SNESSetFunction(), SNESGetFunction()
4924 */
4925 PetscErrorCode  SNESComputeFunction_Matlab(SNES snes,Vec x,Vec y, void *ctx)
4926 {
4927   PetscErrorCode    ierr;
4928   SNESMatlabContext *sctx = (SNESMatlabContext*)ctx;
4929   int               nlhs  = 1,nrhs = 5;
4930   mxArray           *plhs[1],*prhs[5];
4931   long long int     lx = 0,ly = 0,ls = 0;
4932 
4933   PetscFunctionBegin;
4934   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4935   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
4936   PetscValidHeaderSpecific(y,VEC_CLASSID,3);
4937   PetscCheckSameComm(snes,1,x,2);
4938   PetscCheckSameComm(snes,1,y,3);
4939 
4940   /* call Matlab function in ctx with arguments x and y */
4941 
4942   ierr    = PetscMemcpy(&ls,&snes,sizeof(snes));CHKERRQ(ierr);
4943   ierr    = PetscMemcpy(&lx,&x,sizeof(x));CHKERRQ(ierr);
4944   ierr    = PetscMemcpy(&ly,&y,sizeof(x));CHKERRQ(ierr);
4945   prhs[0] = mxCreateDoubleScalar((double)ls);
4946   prhs[1] = mxCreateDoubleScalar((double)lx);
4947   prhs[2] = mxCreateDoubleScalar((double)ly);
4948   prhs[3] = mxCreateString(sctx->funcname);
4949   prhs[4] = sctx->ctx;
4950   ierr    = mexCallMATLAB(nlhs,plhs,nrhs,prhs,"PetscSNESComputeFunctionInternal");CHKERRQ(ierr);
4951   ierr    = mxGetScalar(plhs[0]);CHKERRQ(ierr);
4952   mxDestroyArray(prhs[0]);
4953   mxDestroyArray(prhs[1]);
4954   mxDestroyArray(prhs[2]);
4955   mxDestroyArray(prhs[3]);
4956   mxDestroyArray(plhs[0]);
4957   PetscFunctionReturn(0);
4958 }
4959 
4960 #undef __FUNCT__
4961 #define __FUNCT__ "SNESSetFunctionMatlab"
4962 /*
4963    SNESSetFunctionMatlab - Sets the function evaluation routine and function
4964    vector for use by the SNES routines in solving systems of nonlinear
4965    equations from MATLAB. Here the function is a string containing the name of a MATLAB function
4966 
4967    Logically Collective on SNES
4968 
4969    Input Parameters:
4970 +  snes - the SNES context
4971 .  r - vector to store function value
4972 -  SNESFunction - function evaluation routine
4973 
4974    Notes:
4975    The Newton-like methods typically solve linear systems of the form
4976 $      f'(x) x = -f(x),
4977    where f'(x) denotes the Jacobian matrix and f(x) is the function.
4978 
4979    Level: beginner
4980 
4981    Developer Note:  This bleeds the allocated memory SNESMatlabContext *sctx;
4982 
4983 .keywords: SNES, nonlinear, set, function
4984 
4985 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction()
4986 */
4987 PetscErrorCode  SNESSetFunctionMatlab(SNES snes,Vec r,const char *SNESFunction,mxArray *ctx)
4988 {
4989   PetscErrorCode    ierr;
4990   SNESMatlabContext *sctx;
4991 
4992   PetscFunctionBegin;
4993   /* currently sctx is memory bleed */
4994   ierr = PetscMalloc(sizeof(SNESMatlabContext),&sctx);CHKERRQ(ierr);
4995   ierr = PetscStrallocpy(SNESFunction,&sctx->funcname);CHKERRQ(ierr);
4996   /*
4997      This should work, but it doesn't
4998   sctx->ctx = ctx;
4999   mexMakeArrayPersistent(sctx->ctx);
5000   */
5001   sctx->ctx = mxDuplicateArray(ctx);
5002   ierr      = SNESSetFunction(snes,r,SNESComputeFunction_Matlab,sctx);CHKERRQ(ierr);
5003   PetscFunctionReturn(0);
5004 }
5005 
5006 #undef __FUNCT__
5007 #define __FUNCT__ "SNESComputeJacobian_Matlab"
5008 /*
5009    SNESComputeJacobian_Matlab - Calls the function that has been set with SNESSetJacobianMatlab().
5010 
5011    Collective on SNES
5012 
5013    Input Parameters:
5014 +  snes - the SNES context
5015 .  x - input vector
5016 .  A, B - the matrices
5017 -  ctx - user context
5018 
5019    Output Parameter:
5020 .  flag - structure of the matrix
5021 
5022    Level: developer
5023 
5024 .keywords: SNES, nonlinear, compute, function
5025 
5026 .seealso: SNESSetFunction(), SNESGetFunction()
5027 @*/
5028 PetscErrorCode  SNESComputeJacobian_Matlab(SNES snes,Vec x,Mat *A,Mat *B,MatStructure *flag, void *ctx)
5029 {
5030   PetscErrorCode    ierr;
5031   SNESMatlabContext *sctx = (SNESMatlabContext*)ctx;
5032   int               nlhs  = 2,nrhs = 6;
5033   mxArray           *plhs[2],*prhs[6];
5034   long long int     lx = 0,lA = 0,ls = 0, lB = 0;
5035 
5036   PetscFunctionBegin;
5037   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
5038   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
5039 
5040   /* call Matlab function in ctx with arguments x and y */
5041 
5042   ierr    = PetscMemcpy(&ls,&snes,sizeof(snes));CHKERRQ(ierr);
5043   ierr    = PetscMemcpy(&lx,&x,sizeof(x));CHKERRQ(ierr);
5044   ierr    = PetscMemcpy(&lA,A,sizeof(x));CHKERRQ(ierr);
5045   ierr    = PetscMemcpy(&lB,B,sizeof(x));CHKERRQ(ierr);
5046   prhs[0] = mxCreateDoubleScalar((double)ls);
5047   prhs[1] = mxCreateDoubleScalar((double)lx);
5048   prhs[2] = mxCreateDoubleScalar((double)lA);
5049   prhs[3] = mxCreateDoubleScalar((double)lB);
5050   prhs[4] = mxCreateString(sctx->funcname);
5051   prhs[5] = sctx->ctx;
5052   ierr    = mexCallMATLAB(nlhs,plhs,nrhs,prhs,"PetscSNESComputeJacobianInternal");CHKERRQ(ierr);
5053   ierr    = mxGetScalar(plhs[0]);CHKERRQ(ierr);
5054   *flag   = (MatStructure) mxGetScalar(plhs[1]);CHKERRQ(ierr);
5055   mxDestroyArray(prhs[0]);
5056   mxDestroyArray(prhs[1]);
5057   mxDestroyArray(prhs[2]);
5058   mxDestroyArray(prhs[3]);
5059   mxDestroyArray(prhs[4]);
5060   mxDestroyArray(plhs[0]);
5061   mxDestroyArray(plhs[1]);
5062   PetscFunctionReturn(0);
5063 }
5064 
5065 #undef __FUNCT__
5066 #define __FUNCT__ "SNESSetJacobianMatlab"
5067 /*
5068    SNESSetJacobianMatlab - Sets the Jacobian function evaluation routine and two empty Jacobian matrices
5069    vector for use by the SNES routines in solving systems of nonlinear
5070    equations from MATLAB. Here the function is a string containing the name of a MATLAB function
5071 
5072    Logically Collective on SNES
5073 
5074    Input Parameters:
5075 +  snes - the SNES context
5076 .  A,B - Jacobian matrices
5077 .  SNESJacobianFunction - function evaluation routine
5078 -  ctx - user context
5079 
5080    Level: developer
5081 
5082    Developer Note:  This bleeds the allocated memory SNESMatlabContext *sctx;
5083 
5084 .keywords: SNES, nonlinear, set, function
5085 
5086 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction(), SNESJacobianFunction
5087 */
5088 PetscErrorCode  SNESSetJacobianMatlab(SNES snes,Mat A,Mat B,const char *SNESJacobianFunction,mxArray *ctx)
5089 {
5090   PetscErrorCode    ierr;
5091   SNESMatlabContext *sctx;
5092 
5093   PetscFunctionBegin;
5094   /* currently sctx is memory bleed */
5095   ierr = PetscMalloc(sizeof(SNESMatlabContext),&sctx);CHKERRQ(ierr);
5096   ierr = PetscStrallocpy(SNESJacobianFunction,&sctx->funcname);CHKERRQ(ierr);
5097   /*
5098      This should work, but it doesn't
5099   sctx->ctx = ctx;
5100   mexMakeArrayPersistent(sctx->ctx);
5101   */
5102   sctx->ctx = mxDuplicateArray(ctx);
5103   ierr      = SNESSetJacobian(snes,A,B,SNESComputeJacobian_Matlab,sctx);CHKERRQ(ierr);
5104   PetscFunctionReturn(0);
5105 }
5106 
5107 #undef __FUNCT__
5108 #define __FUNCT__ "SNESMonitor_Matlab"
5109 /*
5110    SNESMonitor_Matlab - Calls the function that has been set with SNESMonitorSetMatlab().
5111 
5112    Collective on SNES
5113 
5114 .seealso: SNESSetFunction(), SNESGetFunction()
5115 @*/
5116 PetscErrorCode  SNESMonitor_Matlab(SNES snes,PetscInt it, PetscReal fnorm, void *ctx)
5117 {
5118   PetscErrorCode    ierr;
5119   SNESMatlabContext *sctx = (SNESMatlabContext*)ctx;
5120   int               nlhs  = 1,nrhs = 6;
5121   mxArray           *plhs[1],*prhs[6];
5122   long long int     lx = 0,ls = 0;
5123   Vec               x  = snes->vec_sol;
5124 
5125   PetscFunctionBegin;
5126   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
5127 
5128   ierr    = PetscMemcpy(&ls,&snes,sizeof(snes));CHKERRQ(ierr);
5129   ierr    = PetscMemcpy(&lx,&x,sizeof(x));CHKERRQ(ierr);
5130   prhs[0] = mxCreateDoubleScalar((double)ls);
5131   prhs[1] = mxCreateDoubleScalar((double)it);
5132   prhs[2] = mxCreateDoubleScalar((double)fnorm);
5133   prhs[3] = mxCreateDoubleScalar((double)lx);
5134   prhs[4] = mxCreateString(sctx->funcname);
5135   prhs[5] = sctx->ctx;
5136   ierr    = mexCallMATLAB(nlhs,plhs,nrhs,prhs,"PetscSNESMonitorInternal");CHKERRQ(ierr);
5137   ierr    = mxGetScalar(plhs[0]);CHKERRQ(ierr);
5138   mxDestroyArray(prhs[0]);
5139   mxDestroyArray(prhs[1]);
5140   mxDestroyArray(prhs[2]);
5141   mxDestroyArray(prhs[3]);
5142   mxDestroyArray(prhs[4]);
5143   mxDestroyArray(plhs[0]);
5144   PetscFunctionReturn(0);
5145 }
5146 
5147 #undef __FUNCT__
5148 #define __FUNCT__ "SNESMonitorSetMatlab"
5149 /*
5150    SNESMonitorSetMatlab - Sets the monitor function from MATLAB
5151 
5152    Level: developer
5153 
5154    Developer Note:  This bleeds the allocated memory SNESMatlabContext *sctx;
5155 
5156 .keywords: SNES, nonlinear, set, function
5157 
5158 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction()
5159 */
5160 PetscErrorCode  SNESMonitorSetMatlab(SNES snes,const char *SNESMonitorFunction,mxArray *ctx)
5161 {
5162   PetscErrorCode    ierr;
5163   SNESMatlabContext *sctx;
5164 
5165   PetscFunctionBegin;
5166   /* currently sctx is memory bleed */
5167   ierr = PetscMalloc(sizeof(SNESMatlabContext),&sctx);CHKERRQ(ierr);
5168   ierr = PetscStrallocpy(SNESMonitorFunction,&sctx->funcname);CHKERRQ(ierr);
5169   /*
5170      This should work, but it doesn't
5171   sctx->ctx = ctx;
5172   mexMakeArrayPersistent(sctx->ctx);
5173   */
5174   sctx->ctx = mxDuplicateArray(ctx);
5175   ierr      = SNESMonitorSet(snes,SNESMonitor_Matlab,sctx,NULL);CHKERRQ(ierr);
5176   PetscFunctionReturn(0);
5177 }
5178 
5179 #endif
5180