xref: /petsc/src/snes/interface/snes.c (revision d96771aa2042b1e5a719ecfb3af017e5d60f0562)
1 
2 #include <petsc/private/snesimpl.h>      /*I "petscsnes.h"  I*/
3 #include <petscdmshell.h>
4 #include <petscdraw.h>
5 
6 PetscBool         SNESRegisterAllCalled = PETSC_FALSE;
7 PetscFunctionList SNESList              = NULL;
8 
9 /* Logging support */
10 PetscClassId  SNES_CLASSID, DMSNES_CLASSID;
11 PetscLogEvent SNES_Solve, SNES_FunctionEval, SNES_JacobianEval, SNES_NGSEval, SNES_NGSFuncEval, SNES_NPCSolve, SNES_ObjectiveEval;
12 
13 #undef __FUNCT__
14 #define __FUNCT__ "SNESSetErrorIfNotConverged"
15 /*@
16    SNESSetErrorIfNotConverged - Causes SNESSolve() to generate an error if the solver has not converged.
17 
18    Logically Collective on SNES
19 
20    Input Parameters:
21 +  snes - iterative context obtained from SNESCreate()
22 -  flg - PETSC_TRUE indicates you want the error generated
23 
24    Options database keys:
25 .  -snes_error_if_not_converged : this takes an optional truth value (0/1/no/yes/true/false)
26 
27    Level: intermediate
28 
29    Notes:
30     Normally PETSc continues if a linear solver fails to converge, you can call SNESGetConvergedReason() after a SNESSolve()
31     to determine if it has converged.
32 
33 .keywords: SNES, set, initial guess, nonzero
34 
35 .seealso: SNESGetErrorIfNotConverged(), KSPGetErrorIfNotConverged(), KSPSetErrorIFNotConverged()
36 @*/
37 PetscErrorCode  SNESSetErrorIfNotConverged(SNES snes,PetscBool flg)
38 {
39   PetscFunctionBegin;
40   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
41   PetscValidLogicalCollectiveBool(snes,flg,2);
42   snes->errorifnotconverged = flg;
43   PetscFunctionReturn(0);
44 }
45 
46 #undef __FUNCT__
47 #define __FUNCT__ "SNESGetErrorIfNotConverged"
48 /*@
49    SNESGetErrorIfNotConverged - Will SNESSolve() generate an error if the solver does not converge?
50 
51    Not Collective
52 
53    Input Parameter:
54 .  snes - iterative context obtained from SNESCreate()
55 
56    Output Parameter:
57 .  flag - PETSC_TRUE if it will generate an error, else PETSC_FALSE
58 
59    Level: intermediate
60 
61 .keywords: SNES, set, initial guess, nonzero
62 
63 .seealso:  SNESSetErrorIfNotConverged(), KSPGetErrorIfNotConverged(), KSPSetErrorIFNotConverged()
64 @*/
65 PetscErrorCode  SNESGetErrorIfNotConverged(SNES snes,PetscBool  *flag)
66 {
67   PetscFunctionBegin;
68   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
69   PetscValidPointer(flag,2);
70   *flag = snes->errorifnotconverged;
71   PetscFunctionReturn(0);
72 }
73 
74 #undef __FUNCT__
75 #define __FUNCT__ "SNESSetFunctionDomainError"
76 /*@
77    SNESSetFunctionDomainError - tells SNES that the input vector to your SNESFunction is not
78      in the functions domain. For example, negative pressure.
79 
80    Logically Collective on SNES
81 
82    Input Parameters:
83 .  snes - the SNES context
84 
85    Level: advanced
86 
87 .keywords: SNES, view
88 
89 .seealso: SNESCreate(), SNESSetFunction(), SNESFunction
90 @*/
91 PetscErrorCode  SNESSetFunctionDomainError(SNES snes)
92 {
93   PetscFunctionBegin;
94   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
95   if (snes->errorifnotconverged) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"User code indicates input vector is not in the function domain");
96   snes->domainerror = PETSC_TRUE;
97   PetscFunctionReturn(0);
98 }
99 
100 #undef __FUNCT__
101 #define __FUNCT__ "SNESGetFunctionDomainError"
102 /*@
103    SNESGetFunctionDomainError - Gets the status of the domain error after a call to SNESComputeFunction;
104 
105    Logically Collective on SNES
106 
107    Input Parameters:
108 .  snes - the SNES context
109 
110    Output Parameters:
111 .  domainerror - Set to PETSC_TRUE if there's a domain error; PETSC_FALSE otherwise.
112 
113    Level: advanced
114 
115 .keywords: SNES, view
116 
117 .seealso: SNESSetFunctionDomainError(), SNESComputeFunction()
118 @*/
119 PetscErrorCode  SNESGetFunctionDomainError(SNES snes, PetscBool *domainerror)
120 {
121   PetscFunctionBegin;
122   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
123   PetscValidPointer(domainerror, 2);
124   *domainerror = snes->domainerror;
125   PetscFunctionReturn(0);
126 }
127 
128 #undef __FUNCT__
129 #define __FUNCT__ "SNESLoad"
130 /*@C
131   SNESLoad - Loads a SNES that has been stored in binary  with SNESView().
132 
133   Collective on PetscViewer
134 
135   Input Parameters:
136 + newdm - the newly loaded SNES, this needs to have been created with SNESCreate() or
137            some related function before a call to SNESLoad().
138 - viewer - binary file viewer, obtained from PetscViewerBinaryOpen()
139 
140    Level: intermediate
141 
142   Notes:
143    The type is determined by the data in the file, any type set into the SNES before this call is ignored.
144 
145   Notes for advanced users:
146   Most users should not need to know the details of the binary storage
147   format, since SNESLoad() and TSView() completely hide these details.
148   But for anyone who's interested, the standard binary matrix storage
149   format is
150 .vb
151      has not yet been determined
152 .ve
153 
154 .seealso: PetscViewerBinaryOpen(), SNESView(), MatLoad(), VecLoad()
155 @*/
156 PetscErrorCode  SNESLoad(SNES snes, PetscViewer viewer)
157 {
158   PetscErrorCode ierr;
159   PetscBool      isbinary;
160   PetscInt       classid;
161   char           type[256];
162   KSP            ksp;
163   DM             dm;
164   DMSNES         dmsnes;
165 
166   PetscFunctionBegin;
167   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
168   PetscValidHeaderSpecific(viewer,PETSC_VIEWER_CLASSID,2);
169   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);CHKERRQ(ierr);
170   if (!isbinary) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONG,"Invalid viewer; open viewer with PetscViewerBinaryOpen()");
171 
172   ierr = PetscViewerBinaryRead(viewer,&classid,1,NULL,PETSC_INT);CHKERRQ(ierr);
173   if (classid != SNES_FILE_CLASSID) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONG,"Not SNES next in file");
174   ierr = PetscViewerBinaryRead(viewer,type,256,NULL,PETSC_CHAR);CHKERRQ(ierr);
175   ierr = SNESSetType(snes, type);CHKERRQ(ierr);
176   if (snes->ops->load) {
177     ierr = (*snes->ops->load)(snes,viewer);CHKERRQ(ierr);
178   }
179   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
180   ierr = DMGetDMSNES(dm,&dmsnes);CHKERRQ(ierr);
181   ierr = DMSNESLoad(dmsnes,viewer);CHKERRQ(ierr);
182   ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
183   ierr = KSPLoad(ksp,viewer);CHKERRQ(ierr);
184   PetscFunctionReturn(0);
185 }
186 
187 #include <petscdraw.h>
188 #if defined(PETSC_HAVE_SAWS)
189 #include <petscviewersaws.h>
190 #endif
191 #undef __FUNCT__
192 #define __FUNCT__ "SNESView"
193 /*@C
194    SNESView - Prints the SNES data structure.
195 
196    Collective on SNES
197 
198    Input Parameters:
199 +  SNES - the SNES context
200 -  viewer - visualization context
201 
202    Options Database Key:
203 .  -snes_view - Calls SNESView() at end of SNESSolve()
204 
205    Notes:
206    The available visualization contexts include
207 +     PETSC_VIEWER_STDOUT_SELF - standard output (default)
208 -     PETSC_VIEWER_STDOUT_WORLD - synchronized standard
209          output where only the first processor opens
210          the file.  All other processors send their
211          data to the first processor to print.
212 
213    The user can open an alternative visualization context with
214    PetscViewerASCIIOpen() - output to a specified file.
215 
216    Level: beginner
217 
218 .keywords: SNES, view
219 
220 .seealso: PetscViewerASCIIOpen()
221 @*/
222 PetscErrorCode  SNESView(SNES snes,PetscViewer viewer)
223 {
224   SNESKSPEW      *kctx;
225   PetscErrorCode ierr;
226   KSP            ksp;
227   SNESLineSearch linesearch;
228   PetscBool      iascii,isstring,isbinary,isdraw;
229   DMSNES         dmsnes;
230 #if defined(PETSC_HAVE_SAWS)
231   PetscBool      issaws;
232 #endif
233 
234   PetscFunctionBegin;
235   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
236   if (!viewer) {
237     ierr = PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&viewer);CHKERRQ(ierr);
238   }
239   PetscValidHeaderSpecific(viewer,PETSC_VIEWER_CLASSID,2);
240   PetscCheckSameComm(snes,1,viewer,2);
241 
242   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr);
243   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);CHKERRQ(ierr);
244   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);CHKERRQ(ierr);
245   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERDRAW,&isdraw);CHKERRQ(ierr);
246 #if defined(PETSC_HAVE_SAWS)
247   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSAWS,&issaws);CHKERRQ(ierr);
248 #endif
249   if (iascii) {
250     SNESNormSchedule normschedule;
251 
252     ierr = PetscObjectPrintClassNamePrefixType((PetscObject)snes,viewer);CHKERRQ(ierr);
253     if (!snes->setupcalled) {
254       ierr = PetscViewerASCIIPrintf(viewer,"  SNES has not been set up so information may be incomplete\n");CHKERRQ(ierr);
255     }
256     if (snes->ops->view) {
257       ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
258       ierr = (*snes->ops->view)(snes,viewer);CHKERRQ(ierr);
259       ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
260     }
261     ierr = PetscViewerASCIIPrintf(viewer,"  maximum iterations=%D, maximum function evaluations=%D\n",snes->max_its,snes->max_funcs);CHKERRQ(ierr);
262     ierr = PetscViewerASCIIPrintf(viewer,"  tolerances: relative=%g, absolute=%g, solution=%g\n",(double)snes->rtol,(double)snes->abstol,(double)snes->stol);CHKERRQ(ierr);
263     ierr = PetscViewerASCIIPrintf(viewer,"  total number of linear solver iterations=%D\n",snes->linear_its);CHKERRQ(ierr);
264     ierr = PetscViewerASCIIPrintf(viewer,"  total number of function evaluations=%D\n",snes->nfuncs);CHKERRQ(ierr);
265     ierr = SNESGetNormSchedule(snes, &normschedule);CHKERRQ(ierr);
266     if (normschedule > 0) {ierr = PetscViewerASCIIPrintf(viewer,"  norm schedule %s\n",SNESNormSchedules[normschedule]);CHKERRQ(ierr);}
267     if (snes->gridsequence) {
268       ierr = PetscViewerASCIIPrintf(viewer,"  total number of grid sequence refinements=%D\n",snes->gridsequence);CHKERRQ(ierr);
269     }
270     if (snes->ksp_ewconv) {
271       kctx = (SNESKSPEW*)snes->kspconvctx;
272       if (kctx) {
273         ierr = PetscViewerASCIIPrintf(viewer,"  Eisenstat-Walker computation of KSP relative tolerance (version %D)\n",kctx->version);CHKERRQ(ierr);
274         ierr = PetscViewerASCIIPrintf(viewer,"    rtol_0=%g, rtol_max=%g, threshold=%g\n",(double)kctx->rtol_0,(double)kctx->rtol_max,(double)kctx->threshold);CHKERRQ(ierr);
275         ierr = PetscViewerASCIIPrintf(viewer,"    gamma=%g, alpha=%g, alpha2=%g\n",(double)kctx->gamma,(double)kctx->alpha,(double)kctx->alpha2);CHKERRQ(ierr);
276       }
277     }
278     if (snes->lagpreconditioner == -1) {
279       ierr = PetscViewerASCIIPrintf(viewer,"  Preconditioned is never rebuilt\n");CHKERRQ(ierr);
280     } else if (snes->lagpreconditioner > 1) {
281       ierr = PetscViewerASCIIPrintf(viewer,"  Preconditioned is rebuilt every %D new Jacobians\n",snes->lagpreconditioner);CHKERRQ(ierr);
282     }
283     if (snes->lagjacobian == -1) {
284       ierr = PetscViewerASCIIPrintf(viewer,"  Jacobian is never rebuilt\n");CHKERRQ(ierr);
285     } else if (snes->lagjacobian > 1) {
286       ierr = PetscViewerASCIIPrintf(viewer,"  Jacobian is rebuilt every %D SNES iterations\n",snes->lagjacobian);CHKERRQ(ierr);
287     }
288   } else if (isstring) {
289     const char *type;
290     ierr = SNESGetType(snes,&type);CHKERRQ(ierr);
291     ierr = PetscViewerStringSPrintf(viewer," %-3.3s",type);CHKERRQ(ierr);
292   } else if (isbinary) {
293     PetscInt    classid = SNES_FILE_CLASSID;
294     MPI_Comm    comm;
295     PetscMPIInt rank;
296     char        type[256];
297 
298     ierr = PetscObjectGetComm((PetscObject)snes,&comm);CHKERRQ(ierr);
299     ierr = MPI_Comm_rank(comm,&rank);CHKERRQ(ierr);
300     if (!rank) {
301       ierr = PetscViewerBinaryWrite(viewer,&classid,1,PETSC_INT,PETSC_FALSE);CHKERRQ(ierr);
302       ierr = PetscStrncpy(type,((PetscObject)snes)->type_name,sizeof(type));CHKERRQ(ierr);
303       ierr = PetscViewerBinaryWrite(viewer,type,sizeof(type),PETSC_CHAR,PETSC_FALSE);CHKERRQ(ierr);
304     }
305     if (snes->ops->view) {
306       ierr = (*snes->ops->view)(snes,viewer);CHKERRQ(ierr);
307     }
308   } else if (isdraw) {
309     PetscDraw draw;
310     char      str[36];
311     PetscReal x,y,bottom,h;
312 
313     ierr   = PetscViewerDrawGetDraw(viewer,0,&draw);CHKERRQ(ierr);
314     ierr   = PetscDrawGetCurrentPoint(draw,&x,&y);CHKERRQ(ierr);
315     ierr   = PetscStrcpy(str,"SNES: ");CHKERRQ(ierr);
316     ierr   = PetscStrcat(str,((PetscObject)snes)->type_name);CHKERRQ(ierr);
317     ierr   = PetscDrawStringBoxed(draw,x,y,PETSC_DRAW_BLUE,PETSC_DRAW_BLACK,str,NULL,&h);CHKERRQ(ierr);
318     bottom = y - h;
319     ierr   = PetscDrawPushCurrentPoint(draw,x,bottom);CHKERRQ(ierr);
320     if (snes->ops->view) {
321       ierr = (*snes->ops->view)(snes,viewer);CHKERRQ(ierr);
322     }
323 #if defined(PETSC_HAVE_SAWS)
324   } else if (issaws) {
325     PetscMPIInt rank;
326     const char *name;
327 
328     ierr = PetscObjectGetName((PetscObject)snes,&name);CHKERRQ(ierr);
329     ierr = MPI_Comm_rank(PETSC_COMM_WORLD,&rank);CHKERRQ(ierr);
330     if (!((PetscObject)snes)->amsmem && !rank) {
331       char       dir[1024];
332 
333       ierr = PetscObjectViewSAWs((PetscObject)snes,viewer);CHKERRQ(ierr);
334       ierr = PetscSNPrintf(dir,1024,"/PETSc/Objects/%s/its",name);CHKERRQ(ierr);
335       PetscStackCallSAWs(SAWs_Register,(dir,&snes->iter,1,SAWs_READ,SAWs_INT));
336       if (!snes->conv_hist) {
337         ierr = SNESSetConvergenceHistory(snes,NULL,NULL,PETSC_DECIDE,PETSC_TRUE);CHKERRQ(ierr);
338       }
339       ierr = PetscSNPrintf(dir,1024,"/PETSc/Objects/%s/conv_hist",name);CHKERRQ(ierr);
340       PetscStackCallSAWs(SAWs_Register,(dir,snes->conv_hist,10,SAWs_READ,SAWs_DOUBLE));
341     }
342 #endif
343   }
344   if (snes->linesearch) {
345     ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
346     ierr = SNESGetLineSearch(snes, &linesearch);CHKERRQ(ierr);
347     ierr = SNESLineSearchView(linesearch, viewer);CHKERRQ(ierr);
348     ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
349   }
350   if (snes->pc && snes->usespc) {
351     ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
352     ierr = SNESView(snes->pc, viewer);CHKERRQ(ierr);
353     ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
354   }
355   ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
356   ierr = DMGetDMSNES(snes->dm,&dmsnes);CHKERRQ(ierr);
357   ierr = DMSNESView(dmsnes, viewer);CHKERRQ(ierr);
358   ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
359   if (snes->usesksp) {
360     ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
361     ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
362     ierr = KSPView(ksp,viewer);CHKERRQ(ierr);
363     ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
364   }
365   if (isdraw) {
366     PetscDraw draw;
367     ierr = PetscViewerDrawGetDraw(viewer,0,&draw);CHKERRQ(ierr);
368     ierr = PetscDrawPopCurrentPoint(draw);CHKERRQ(ierr);
369   }
370   PetscFunctionReturn(0);
371 }
372 
373 /*
374   We retain a list of functions that also take SNES command
375   line options. These are called at the end SNESSetFromOptions()
376 */
377 #define MAXSETFROMOPTIONS 5
378 static PetscInt numberofsetfromoptions;
379 static PetscErrorCode (*othersetfromoptions[MAXSETFROMOPTIONS])(SNES);
380 
381 #undef __FUNCT__
382 #define __FUNCT__ "SNESAddOptionsChecker"
383 /*@C
384   SNESAddOptionsChecker - Adds an additional function to check for SNES options.
385 
386   Not Collective
387 
388   Input Parameter:
389 . snescheck - function that checks for options
390 
391   Level: developer
392 
393 .seealso: SNESSetFromOptions()
394 @*/
395 PetscErrorCode  SNESAddOptionsChecker(PetscErrorCode (*snescheck)(SNES))
396 {
397   PetscFunctionBegin;
398   if (numberofsetfromoptions >= MAXSETFROMOPTIONS) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE, "Too many options checkers, only %D allowed", MAXSETFROMOPTIONS);
399   othersetfromoptions[numberofsetfromoptions++] = snescheck;
400   PetscFunctionReturn(0);
401 }
402 
403 extern PetscErrorCode  SNESDefaultMatrixFreeCreate2(SNES,Vec,Mat*);
404 
405 #undef __FUNCT__
406 #define __FUNCT__ "SNESSetUpMatrixFree_Private"
407 static PetscErrorCode SNESSetUpMatrixFree_Private(SNES snes, PetscBool hasOperator, PetscInt version)
408 {
409   Mat            J;
410   KSP            ksp;
411   PC             pc;
412   PetscBool      match;
413   PetscErrorCode ierr;
414   MatNullSpace   nullsp;
415 
416   PetscFunctionBegin;
417   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
418 
419   if (!snes->vec_func && (snes->jacobian || snes->jacobian_pre)) {
420     Mat A = snes->jacobian, B = snes->jacobian_pre;
421     ierr = MatCreateVecs(A ? A : B, NULL,&snes->vec_func);CHKERRQ(ierr);
422   }
423 
424   if (version == 1) {
425     ierr = MatCreateSNESMF(snes,&J);CHKERRQ(ierr);
426     ierr = MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);CHKERRQ(ierr);
427     ierr = MatSetFromOptions(J);CHKERRQ(ierr);
428   } else if (version == 2) {
429     if (!snes->vec_func) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"SNESSetFunction() must be called first");
430 #if !defined(PETSC_USE_COMPLEX) && !defined(PETSC_USE_REAL_SINGLE) && !defined(PETSC_USE_REAL___FLOAT128)
431     ierr = SNESDefaultMatrixFreeCreate2(snes,snes->vec_func,&J);CHKERRQ(ierr);
432 #else
433     SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP, "matrix-free operator rutines (version 2)");
434 #endif
435   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE, "matrix-free operator rutines, only version 1 and 2");
436 
437   /* attach any user provided null space that was on Amat to the newly created matrix free matrix */
438   if (snes->jacobian) {
439     ierr = MatGetNullSpace(snes->jacobian,&nullsp);CHKERRQ(ierr);
440     if (nullsp) {
441       ierr = MatSetNullSpace(J,nullsp);CHKERRQ(ierr);
442     }
443   }
444 
445   ierr = PetscInfo1(snes,"Setting default matrix-free operator routines (version %D)\n", version);CHKERRQ(ierr);
446   if (hasOperator) {
447 
448     /* This version replaces the user provided Jacobian matrix with a
449        matrix-free version but still employs the user-provided preconditioner matrix. */
450     ierr = SNESSetJacobian(snes,J,0,0,0);CHKERRQ(ierr);
451   } else {
452     /* This version replaces both the user-provided Jacobian and the user-
453      provided preconditioner Jacobian with the default matrix free version. */
454     if ((snes->pcside == PC_LEFT) && snes->pc) {
455       if (!snes->jacobian){ierr = SNESSetJacobian(snes,J,0,0,0);CHKERRQ(ierr);}
456     } else {
457       ierr = SNESSetJacobian(snes,J,J,MatMFFDComputeJacobian,0);CHKERRQ(ierr);
458     }
459     /* Force no preconditioner */
460     ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
461     ierr = KSPGetPC(ksp,&pc);CHKERRQ(ierr);
462     ierr = PetscObjectTypeCompare((PetscObject)pc,PCSHELL,&match);CHKERRQ(ierr);
463     if (!match) {
464       ierr = PetscInfo(snes,"Setting default matrix-free preconditioner routines\nThat is no preconditioner is being used\n");CHKERRQ(ierr);
465       ierr = PCSetType(pc,PCNONE);CHKERRQ(ierr);
466     }
467   }
468   ierr = MatDestroy(&J);CHKERRQ(ierr);
469   PetscFunctionReturn(0);
470 }
471 
472 #undef __FUNCT__
473 #define __FUNCT__ "DMRestrictHook_SNESVecSol"
474 static PetscErrorCode DMRestrictHook_SNESVecSol(DM dmfine,Mat Restrict,Vec Rscale,Mat Inject,DM dmcoarse,void *ctx)
475 {
476   SNES           snes = (SNES)ctx;
477   PetscErrorCode ierr;
478   Vec            Xfine,Xfine_named = NULL,Xcoarse;
479 
480   PetscFunctionBegin;
481   if (PetscLogPrintInfo) {
482     PetscInt finelevel,coarselevel,fineclevel,coarseclevel;
483     ierr = DMGetRefineLevel(dmfine,&finelevel);CHKERRQ(ierr);
484     ierr = DMGetCoarsenLevel(dmfine,&fineclevel);CHKERRQ(ierr);
485     ierr = DMGetRefineLevel(dmcoarse,&coarselevel);CHKERRQ(ierr);
486     ierr = DMGetCoarsenLevel(dmcoarse,&coarseclevel);CHKERRQ(ierr);
487     ierr = PetscInfo4(dmfine,"Restricting SNES solution vector from level %D-%D to level %D-%D\n",finelevel,fineclevel,coarselevel,coarseclevel);CHKERRQ(ierr);
488   }
489   if (dmfine == snes->dm) Xfine = snes->vec_sol;
490   else {
491     ierr  = DMGetNamedGlobalVector(dmfine,"SNESVecSol",&Xfine_named);CHKERRQ(ierr);
492     Xfine = Xfine_named;
493   }
494   ierr = DMGetNamedGlobalVector(dmcoarse,"SNESVecSol",&Xcoarse);CHKERRQ(ierr);
495   if (Inject) {
496     ierr = MatRestrict(Inject,Xfine,Xcoarse);CHKERRQ(ierr);
497   } else {
498     ierr = MatRestrict(Restrict,Xfine,Xcoarse);CHKERRQ(ierr);
499     ierr = VecPointwiseMult(Xcoarse,Xcoarse,Rscale);CHKERRQ(ierr);
500   }
501   ierr = DMRestoreNamedGlobalVector(dmcoarse,"SNESVecSol",&Xcoarse);CHKERRQ(ierr);
502   if (Xfine_named) {ierr = DMRestoreNamedGlobalVector(dmfine,"SNESVecSol",&Xfine_named);CHKERRQ(ierr);}
503   PetscFunctionReturn(0);
504 }
505 
506 #undef __FUNCT__
507 #define __FUNCT__ "DMCoarsenHook_SNESVecSol"
508 static PetscErrorCode DMCoarsenHook_SNESVecSol(DM dm,DM dmc,void *ctx)
509 {
510   PetscErrorCode ierr;
511 
512   PetscFunctionBegin;
513   ierr = DMCoarsenHookAdd(dmc,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,ctx);CHKERRQ(ierr);
514   PetscFunctionReturn(0);
515 }
516 
517 #undef __FUNCT__
518 #define __FUNCT__ "KSPComputeOperators_SNES"
519 /* This may be called to rediscretize the operator on levels of linear multigrid. The DM shuffle is so the user can
520  * safely call SNESGetDM() in their residual evaluation routine. */
521 static PetscErrorCode KSPComputeOperators_SNES(KSP ksp,Mat A,Mat B,void *ctx)
522 {
523   SNES           snes = (SNES)ctx;
524   PetscErrorCode ierr;
525   Mat            Asave = A,Bsave = B;
526   Vec            X,Xnamed = NULL;
527   DM             dmsave;
528   void           *ctxsave;
529   PetscErrorCode (*jac)(SNES,Vec,Mat,Mat,void*);
530 
531   PetscFunctionBegin;
532   dmsave = snes->dm;
533   ierr   = KSPGetDM(ksp,&snes->dm);CHKERRQ(ierr);
534   if (dmsave == snes->dm) X = snes->vec_sol; /* We are on the finest level */
535   else {                                     /* We are on a coarser level, this vec was initialized using a DM restrict hook */
536     ierr = DMGetNamedGlobalVector(snes->dm,"SNESVecSol",&Xnamed);CHKERRQ(ierr);
537     X    = Xnamed;
538     ierr = SNESGetJacobian(snes,NULL,NULL,&jac,&ctxsave);CHKERRQ(ierr);
539     /* If the DM's don't match up, the MatFDColoring context needed for the jacobian won't match up either -- fixit. */
540     if (jac == SNESComputeJacobianDefaultColor) {
541       ierr = SNESSetJacobian(snes,NULL,NULL,SNESComputeJacobianDefaultColor,0);CHKERRQ(ierr);
542     }
543   }
544   /* put the previous context back */
545 
546   ierr = SNESComputeJacobian(snes,X,A,B);CHKERRQ(ierr);
547   if (snes->dm != dmsave && jac == SNESComputeJacobianDefaultColor) {
548     ierr = SNESSetJacobian(snes,NULL,NULL,jac,ctxsave);CHKERRQ(ierr);
549   }
550 
551   if (A != Asave || B != Bsave) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_SUP,"No support for changing matrices at this time");
552   if (Xnamed) {
553     ierr = DMRestoreNamedGlobalVector(snes->dm,"SNESVecSol",&Xnamed);CHKERRQ(ierr);
554   }
555   snes->dm = dmsave;
556   PetscFunctionReturn(0);
557 }
558 
559 #undef __FUNCT__
560 #define __FUNCT__ "SNESSetUpMatrices"
561 /*@
562    SNESSetUpMatrices - ensures that matrices are available for SNES, to be called by SNESSetUp_XXX()
563 
564    Collective
565 
566    Input Arguments:
567 .  snes - snes to configure
568 
569    Level: developer
570 
571 .seealso: SNESSetUp()
572 @*/
573 PetscErrorCode SNESSetUpMatrices(SNES snes)
574 {
575   PetscErrorCode ierr;
576   DM             dm;
577   DMSNES         sdm;
578 
579   PetscFunctionBegin;
580   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
581   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
582   if (!sdm->ops->computejacobian) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_PLIB,"DMSNES not properly configured");
583   else if (!snes->jacobian && snes->mf) {
584     Mat  J;
585     void *functx;
586     ierr = MatCreateSNESMF(snes,&J);CHKERRQ(ierr);
587     ierr = MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);CHKERRQ(ierr);
588     ierr = MatSetFromOptions(J);CHKERRQ(ierr);
589     ierr = SNESGetFunction(snes,NULL,NULL,&functx);CHKERRQ(ierr);
590     ierr = SNESSetJacobian(snes,J,J,0,0);CHKERRQ(ierr);
591     ierr = MatDestroy(&J);CHKERRQ(ierr);
592   } else if (snes->mf_operator && !snes->jacobian_pre && !snes->jacobian) {
593     Mat J,B;
594     ierr = MatCreateSNESMF(snes,&J);CHKERRQ(ierr);
595     ierr = MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);CHKERRQ(ierr);
596     ierr = MatSetFromOptions(J);CHKERRQ(ierr);
597     ierr = DMCreateMatrix(snes->dm,&B);CHKERRQ(ierr);
598     /* sdm->computejacobian was already set to reach here */
599     ierr = SNESSetJacobian(snes,J,B,NULL,NULL);CHKERRQ(ierr);
600     ierr = MatDestroy(&J);CHKERRQ(ierr);
601     ierr = MatDestroy(&B);CHKERRQ(ierr);
602   } else if (!snes->jacobian_pre) {
603     Mat J,B;
604     J    = snes->jacobian;
605     ierr = DMCreateMatrix(snes->dm,&B);CHKERRQ(ierr);
606     ierr = SNESSetJacobian(snes,J ? J : B,B,NULL,NULL);CHKERRQ(ierr);
607     ierr = MatDestroy(&B);CHKERRQ(ierr);
608   }
609   {
610     KSP ksp;
611     ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
612     ierr = KSPSetComputeOperators(ksp,KSPComputeOperators_SNES,snes);CHKERRQ(ierr);
613     ierr = DMCoarsenHookAdd(snes->dm,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,snes);CHKERRQ(ierr);
614   }
615   PetscFunctionReturn(0);
616 }
617 
618 #undef __FUNCT__
619 #define __FUNCT__ "SNESSetFromOptions"
620 /*@
621    SNESSetFromOptions - Sets various SNES and KSP parameters from user options.
622 
623    Collective on SNES
624 
625    Input Parameter:
626 .  snes - the SNES context
627 
628    Options Database Keys:
629 +  -snes_type <type> - newtonls, newtontr, ngmres, ncg, nrichardson, qn, vi, fas, SNESType for complete list
630 .  -snes_stol - convergence tolerance in terms of the norm
631                 of the change in the solution between steps
632 .  -snes_atol <abstol> - absolute tolerance of residual norm
633 .  -snes_rtol <rtol> - relative decrease in tolerance norm from initial
634 .  -snes_max_it <max_it> - maximum number of iterations
635 .  -snes_max_funcs <max_funcs> - maximum number of function evaluations
636 .  -snes_max_fail <max_fail> - maximum number of line search failures allowed before stopping, default is none
637 .  -snes_max_linear_solve_fail - number of linear solver failures before SNESSolve() stops
638 .  -snes_lag_preconditioner <lag> - how often preconditioner is rebuilt (use -1 to never rebuild)
639 .  -snes_lag_jacobian <lag> - how often Jacobian is rebuilt (use -1 to never rebuild)
640 .  -snes_trtol <trtol> - trust region tolerance
641 .  -snes_no_convergence_test - skip convergence test in nonlinear
642                                solver; hence iterations will continue until max_it
643                                or some other criterion is reached. Saves expense
644                                of convergence test
645 .  -snes_monitor <optional filename> - prints residual norm at each iteration. if no
646                                        filename given prints to stdout
647 .  -snes_monitor_solution - plots solution at each iteration
648 .  -snes_monitor_residual - plots residual (not its norm) at each iteration
649 .  -snes_monitor_solution_update - plots update to solution at each iteration
650 .  -snes_monitor_lg_residualnorm - plots residual norm at each iteration
651 .  -snes_monitor_lg_range - plots residual norm at each iteration
652 .  -snes_fd - use finite differences to compute Jacobian; very slow, only for testing
653 .  -snes_fd_color - use finite differences with coloring to compute Jacobian
654 .  -snes_mf_ksp_monitor - if using matrix-free multiply then print h at each KSP iteration
655 -  -snes_converged_reason - print the reason for convergence/divergence after each solve
656 
657     Options Database for Eisenstat-Walker method:
658 +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
659 .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
660 .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
661 .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
662 .  -snes_ksp_ew_gamma <gamma> - Sets gamma
663 .  -snes_ksp_ew_alpha <alpha> - Sets alpha
664 .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
665 -  -snes_ksp_ew_threshold <threshold> - Sets threshold
666 
667    Notes:
668    To see all options, run your program with the -help option or consult
669    Users-Manual: ch_snes
670 
671    Level: beginner
672 
673 .keywords: SNES, nonlinear, set, options, database
674 
675 .seealso: SNESSetOptionsPrefix()
676 @*/
677 PetscErrorCode  SNESSetFromOptions(SNES snes)
678 {
679   PetscBool      flg,pcset,persist,set;
680   PetscInt       i,indx,lag,grids;
681   const char     *deft        = SNESNEWTONLS;
682   const char     *convtests[] = {"default","skip"};
683   SNESKSPEW      *kctx        = NULL;
684   char           type[256], monfilename[PETSC_MAX_PATH_LEN];
685   PetscViewer    monviewer;
686   PetscErrorCode ierr;
687   PCSide         pcside;
688   const char     *optionsprefix;
689 
690   PetscFunctionBegin;
691   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
692   ierr = SNESRegisterAll();CHKERRQ(ierr);
693   ierr = PetscObjectOptionsBegin((PetscObject)snes);CHKERRQ(ierr);
694   if (((PetscObject)snes)->type_name) deft = ((PetscObject)snes)->type_name;
695   ierr = PetscOptionsFList("-snes_type","Nonlinear solver method","SNESSetType",SNESList,deft,type,256,&flg);CHKERRQ(ierr);
696   if (flg) {
697     ierr = SNESSetType(snes,type);CHKERRQ(ierr);
698   } else if (!((PetscObject)snes)->type_name) {
699     ierr = SNESSetType(snes,deft);CHKERRQ(ierr);
700   }
701   ierr = PetscOptionsReal("-snes_stol","Stop if step length less than","SNESSetTolerances",snes->stol,&snes->stol,NULL);CHKERRQ(ierr);
702   ierr = PetscOptionsReal("-snes_atol","Stop if function norm less than","SNESSetTolerances",snes->abstol,&snes->abstol,NULL);CHKERRQ(ierr);
703 
704   ierr = PetscOptionsReal("-snes_rtol","Stop if decrease in function norm less than","SNESSetTolerances",snes->rtol,&snes->rtol,NULL);CHKERRQ(ierr);
705   ierr = PetscOptionsInt("-snes_max_it","Maximum iterations","SNESSetTolerances",snes->max_its,&snes->max_its,NULL);CHKERRQ(ierr);
706   ierr = PetscOptionsInt("-snes_max_funcs","Maximum function evaluations","SNESSetTolerances",snes->max_funcs,&snes->max_funcs,NULL);CHKERRQ(ierr);
707   ierr = PetscOptionsInt("-snes_max_fail","Maximum nonlinear step failures","SNESSetMaxNonlinearStepFailures",snes->maxFailures,&snes->maxFailures,NULL);CHKERRQ(ierr);
708   ierr = PetscOptionsInt("-snes_max_linear_solve_fail","Maximum failures in linear solves allowed","SNESSetMaxLinearSolveFailures",snes->maxLinearSolveFailures,&snes->maxLinearSolveFailures,NULL);CHKERRQ(ierr);
709   ierr = PetscOptionsBool("-snes_error_if_not_converged","Generate error if solver does not converge","SNESSetErrorIfNotConverged",snes->errorifnotconverged,&snes->errorifnotconverged,NULL);CHKERRQ(ierr);
710 
711   ierr = PetscOptionsInt("-snes_lag_preconditioner","How often to rebuild preconditioner","SNESSetLagPreconditioner",snes->lagpreconditioner,&lag,&flg);CHKERRQ(ierr);
712   if (flg) {
713     ierr = SNESSetLagPreconditioner(snes,lag);CHKERRQ(ierr);
714   }
715   ierr = PetscOptionsBool("-snes_lag_preconditioner_persists","Preconditioner lagging through multiple solves","SNESSetLagPreconditionerPersists",snes->lagjac_persist,&persist,&flg);CHKERRQ(ierr);
716   if (flg) {
717     ierr = SNESSetLagPreconditionerPersists(snes,persist);CHKERRQ(ierr);
718   }
719   ierr = PetscOptionsInt("-snes_lag_jacobian","How often to rebuild Jacobian","SNESSetLagJacobian",snes->lagjacobian,&lag,&flg);CHKERRQ(ierr);
720   if (flg) {
721     ierr = SNESSetLagJacobian(snes,lag);CHKERRQ(ierr);
722   }
723   ierr = PetscOptionsBool("-snes_lag_jacobian_persists","Jacobian lagging through multiple solves","SNESSetLagJacobianPersists",snes->lagjac_persist,&persist,&flg);CHKERRQ(ierr);
724   if (flg) {
725     ierr = SNESSetLagJacobianPersists(snes,persist);CHKERRQ(ierr);
726   }
727 
728   ierr = PetscOptionsInt("-snes_grid_sequence","Use grid sequencing to generate initial guess","SNESSetGridSequence",snes->gridsequence,&grids,&flg);CHKERRQ(ierr);
729   if (flg) {
730     ierr = SNESSetGridSequence(snes,grids);CHKERRQ(ierr);
731   }
732 
733   ierr = PetscOptionsEList("-snes_convergence_test","Convergence test","SNESSetConvergenceTest",convtests,2,"default",&indx,&flg);CHKERRQ(ierr);
734   if (flg) {
735     switch (indx) {
736     case 0: ierr = SNESSetConvergenceTest(snes,SNESConvergedDefault,NULL,NULL);CHKERRQ(ierr); break;
737     case 1: ierr = SNESSetConvergenceTest(snes,SNESConvergedSkip,NULL,NULL);CHKERRQ(ierr);    break;
738     }
739   }
740 
741   ierr = PetscOptionsEList("-snes_norm_schedule","SNES Norm schedule","SNESSetNormSchedule",SNESNormSchedules,5,"function",&indx,&flg);CHKERRQ(ierr);
742   if (flg) { ierr = SNESSetNormSchedule(snes,(SNESNormSchedule)indx);CHKERRQ(ierr); }
743 
744   ierr = PetscOptionsEList("-snes_function_type","SNES Norm schedule","SNESSetFunctionType",SNESFunctionTypes,2,"unpreconditioned",&indx,&flg);CHKERRQ(ierr);
745   if (flg) { ierr = SNESSetFunctionType(snes,(SNESFunctionType)indx);CHKERRQ(ierr); }
746 
747   kctx = (SNESKSPEW*)snes->kspconvctx;
748 
749   ierr = PetscOptionsBool("-snes_ksp_ew","Use Eisentat-Walker linear system convergence test","SNESKSPSetUseEW",snes->ksp_ewconv,&snes->ksp_ewconv,NULL);CHKERRQ(ierr);
750 
751   ierr = PetscOptionsInt("-snes_ksp_ew_version","Version 1, 2 or 3","SNESKSPSetParametersEW",kctx->version,&kctx->version,NULL);CHKERRQ(ierr);
752   ierr = PetscOptionsReal("-snes_ksp_ew_rtol0","0 <= rtol0 < 1","SNESKSPSetParametersEW",kctx->rtol_0,&kctx->rtol_0,NULL);CHKERRQ(ierr);
753   ierr = PetscOptionsReal("-snes_ksp_ew_rtolmax","0 <= rtolmax < 1","SNESKSPSetParametersEW",kctx->rtol_max,&kctx->rtol_max,NULL);CHKERRQ(ierr);
754   ierr = PetscOptionsReal("-snes_ksp_ew_gamma","0 <= gamma <= 1","SNESKSPSetParametersEW",kctx->gamma,&kctx->gamma,NULL);CHKERRQ(ierr);
755   ierr = PetscOptionsReal("-snes_ksp_ew_alpha","1 < alpha <= 2","SNESKSPSetParametersEW",kctx->alpha,&kctx->alpha,NULL);CHKERRQ(ierr);
756   ierr = PetscOptionsReal("-snes_ksp_ew_alpha2","alpha2","SNESKSPSetParametersEW",kctx->alpha2,&kctx->alpha2,NULL);CHKERRQ(ierr);
757   ierr = PetscOptionsReal("-snes_ksp_ew_threshold","0 < threshold < 1","SNESKSPSetParametersEW",kctx->threshold,&kctx->threshold,NULL);CHKERRQ(ierr);
758 
759   flg  = PETSC_FALSE;
760   ierr = PetscOptionsBool("-snes_check_jacobian","Check each Jacobian with a differenced one","SNESUpdateCheckJacobian",flg,&flg,&set);CHKERRQ(ierr);
761   if (set && flg) {
762     ierr = SNESSetUpdate(snes,SNESUpdateCheckJacobian);CHKERRQ(ierr);
763   }
764 
765   flg  = PETSC_FALSE;
766   ierr = PetscOptionsBool("-snes_monitor_cancel","Remove all monitors","SNESMonitorCancel",flg,&flg,&set);CHKERRQ(ierr);
767   if (set && flg) {ierr = SNESMonitorCancel(snes);CHKERRQ(ierr);}
768 
769   ierr = PetscOptionsString("-snes_monitor","Monitor norm of function","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
770   if (flg) {
771     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
772     ierr = SNESMonitorSet(snes,SNESMonitorDefault,monviewer,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
773   }
774 
775   ierr = PetscOptionsString("-snes_monitor_range","Monitor range of elements of function","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
776   if (flg) {
777     ierr = SNESMonitorSet(snes,SNESMonitorRange,0,0);CHKERRQ(ierr);
778   }
779 
780   ierr = PetscOptionsString("-snes_ratiomonitor","Monitor ratios of norms of function","SNESMonitorSetRatio","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
781   if (flg) {
782     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
783     ierr = SNESMonitorSetRatio(snes,monviewer);CHKERRQ(ierr);
784   }
785 
786   ierr = PetscOptionsString("-snes_monitor_short","Monitor norm of function (fewer digits)","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
787   if (flg) {
788     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
789     ierr = SNESMonitorSet(snes,SNESMonitorDefaultShort,monviewer,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
790   }
791 
792   ierr = PetscOptionsString("-snes_monitor_field","Monitor norm of function (split into fields)","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
793   if (flg) {
794     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
795     ierr = SNESMonitorSet(snes,SNESMonitorDefaultField,monviewer,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
796   }
797 
798   ierr = PetscOptionsString("-snes_monitor_python","Use Python function","SNESMonitorSet",0,monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
799   if (flg) {ierr = PetscPythonMonitorSet((PetscObject)snes,monfilename);CHKERRQ(ierr);}
800 
801   flg  = PETSC_FALSE;
802   ierr = PetscOptionsBool("-snes_monitor_solution","Plot solution at each iteration","SNESMonitorSolution",flg,&flg,NULL);CHKERRQ(ierr);
803   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorSolution,0,0);CHKERRQ(ierr);}
804   flg  = PETSC_FALSE;
805   ierr = PetscOptionsBool("-snes_monitor_solution_update","Plot correction at each iteration","SNESMonitorSolutionUpdate",flg,&flg,NULL);CHKERRQ(ierr);
806   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorSolutionUpdate,0,0);CHKERRQ(ierr);}
807   flg  = PETSC_FALSE;
808   ierr = PetscOptionsBool("-snes_monitor_residual","Plot residual at each iteration","SNESMonitorResidual",flg,&flg,NULL);CHKERRQ(ierr);
809   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorResidual,0,0);CHKERRQ(ierr);}
810   flg  = PETSC_FALSE;
811   ierr = PetscOptionsBool("-snes_monitor_lg_residualnorm","Plot function norm at each iteration","SNESMonitorLGResidualNorm",flg,&flg,NULL);CHKERRQ(ierr);
812   if (flg) {
813     PetscDrawLG ctx;
814 
815     ierr = SNESMonitorLGCreate(PetscObjectComm((PetscObject)snes),NULL,NULL,PETSC_DECIDE,PETSC_DECIDE,300,300,&ctx);CHKERRQ(ierr);
816     ierr = SNESMonitorSet(snes,SNESMonitorLGResidualNorm,ctx,(PetscErrorCode (*)(void**))PetscDrawLGDestroy);CHKERRQ(ierr);
817   }
818   flg  = PETSC_FALSE;
819   ierr = PetscOptionsBool("-snes_monitor_lg_range","Plot function range at each iteration","SNESMonitorLGRange",flg,&flg,NULL);CHKERRQ(ierr);
820   if (flg) {
821     PetscViewer ctx;
822 
823     ierr = PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),0,0,PETSC_DECIDE,PETSC_DECIDE,300,300,&ctx);CHKERRQ(ierr);
824     ierr = SNESMonitorSet(snes,SNESMonitorLGRange,ctx,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
825   }
826 
827   flg  = PETSC_FALSE;
828   ierr = PetscOptionsBool("-snes_monitor_jacupdate_spectrum","Print the change in the spectrum of the Jacobian","SNESMonitorJacUpdateSpectrum",flg,&flg,NULL);CHKERRQ(ierr);
829   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorJacUpdateSpectrum,0,0);CHKERRQ(ierr);}
830 
831 
832   ierr = PetscOptionsString("-snes_monitor_fields","Monitor norm of function per field","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
833   if (flg) {
834     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
835     ierr = SNESMonitorSet(snes,SNESMonitorFields,monviewer,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
836   }
837 
838   flg  = PETSC_FALSE;
839   ierr = PetscOptionsBool("-snes_fd","Use finite differences (slow) to compute Jacobian","SNESComputeJacobianDefault",flg,&flg,NULL);CHKERRQ(ierr);
840   if (flg) {
841     void *functx;
842     ierr = SNESGetFunction(snes,NULL,NULL,&functx);CHKERRQ(ierr);
843     ierr = SNESSetJacobian(snes,snes->jacobian,snes->jacobian_pre,SNESComputeJacobianDefault,functx);CHKERRQ(ierr);
844     ierr = PetscInfo(snes,"Setting default finite difference Jacobian matrix\n");CHKERRQ(ierr);
845   }
846 
847   flg  = PETSC_FALSE;
848   ierr = PetscOptionsBool("-snes_fd_function","Use finite differences (slow) to compute function from user objective","SNESObjectiveComputeFunctionDefaultFD",flg,&flg,NULL);CHKERRQ(ierr);
849   if (flg) {
850     ierr = SNESSetFunction(snes,NULL,SNESObjectiveComputeFunctionDefaultFD,NULL);CHKERRQ(ierr);
851   }
852 
853   flg  = PETSC_FALSE;
854   ierr = PetscOptionsBool("-snes_fd_color","Use finite differences with coloring to compute Jacobian","SNESComputeJacobianDefaultColor",flg,&flg,NULL);CHKERRQ(ierr);
855   if (flg) {
856     DM             dm;
857     DMSNES         sdm;
858     ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
859     ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
860     sdm->jacobianctx = NULL;
861     ierr = SNESSetJacobian(snes,snes->jacobian,snes->jacobian_pre,SNESComputeJacobianDefaultColor,0);CHKERRQ(ierr);
862     ierr = PetscInfo(snes,"Setting default finite difference coloring Jacobian matrix\n");CHKERRQ(ierr);
863   }
864 
865   flg  = PETSC_FALSE;
866   ierr = PetscOptionsBool("-snes_mf_operator","Use a Matrix-Free Jacobian with user-provided preconditioner matrix","MatCreateSNESMF",PETSC_FALSE,&snes->mf_operator,&flg);CHKERRQ(ierr);
867   if (flg && snes->mf_operator) {
868     snes->mf_operator = PETSC_TRUE;
869     snes->mf          = PETSC_TRUE;
870   }
871   flg  = PETSC_FALSE;
872   ierr = PetscOptionsBool("-snes_mf","Use a Matrix-Free Jacobian with no preconditioner matrix","MatCreateSNESMF",PETSC_FALSE,&snes->mf,&flg);CHKERRQ(ierr);
873   if (!flg && snes->mf_operator) snes->mf = PETSC_TRUE;
874   ierr = PetscOptionsInt("-snes_mf_version","Matrix-Free routines version 1 or 2","None",snes->mf_version,&snes->mf_version,0);CHKERRQ(ierr);
875 
876   flg  = PETSC_FALSE;
877   ierr = SNESGetNPCSide(snes,&pcside);CHKERRQ(ierr);
878   ierr = PetscOptionsEnum("-snes_npc_side","SNES nonlinear preconditioner side","SNESSetNPCSide",PCSides,(PetscEnum)pcside,(PetscEnum*)&pcside,&flg);CHKERRQ(ierr);
879   if (flg) {ierr = SNESSetNPCSide(snes,pcside);CHKERRQ(ierr);}
880 
881 #if defined(PETSC_HAVE_SAWS)
882   /*
883     Publish convergence information using SAWs
884   */
885   flg  = PETSC_FALSE;
886   ierr = PetscOptionsBool("-snes_monitor_saws","Publish SNES progress using SAWs","SNESMonitorSet",flg,&flg,NULL);CHKERRQ(ierr);
887   if (flg) {
888     void *ctx;
889     ierr = SNESMonitorSAWsCreate(snes,&ctx);CHKERRQ(ierr);
890     ierr = SNESMonitorSet(snes,SNESMonitorSAWs,ctx,SNESMonitorSAWsDestroy);CHKERRQ(ierr);
891   }
892 #endif
893 #if defined(PETSC_HAVE_SAWS)
894   {
895   PetscBool set;
896   flg  = PETSC_FALSE;
897   ierr = PetscOptionsBool("-snes_saws_block","Block for SAWs at end of SNESSolve","PetscObjectSAWsBlock",((PetscObject)snes)->amspublishblock,&flg,&set);CHKERRQ(ierr);
898   if (set) {
899     ierr = PetscObjectSAWsSetBlock((PetscObject)snes,flg);CHKERRQ(ierr);
900   }
901   }
902 #endif
903 
904   for (i = 0; i < numberofsetfromoptions; i++) {
905     ierr = (*othersetfromoptions[i])(snes);CHKERRQ(ierr);
906   }
907 
908   if (snes->ops->setfromoptions) {
909     ierr = (*snes->ops->setfromoptions)(PetscOptionsObject,snes);CHKERRQ(ierr);
910   }
911 
912   /* process any options handlers added with PetscObjectAddOptionsHandler() */
913   ierr = PetscObjectProcessOptionsHandlers((PetscObject)snes);CHKERRQ(ierr);
914   ierr = PetscOptionsEnd();CHKERRQ(ierr);
915 
916   if (!snes->linesearch) {
917     ierr = SNESGetLineSearch(snes, &snes->linesearch);CHKERRQ(ierr);
918   }
919   ierr = SNESLineSearchSetFromOptions(snes->linesearch);CHKERRQ(ierr);
920 
921   if (!snes->ksp) {ierr = SNESGetKSP(snes,&snes->ksp);CHKERRQ(ierr);}
922   ierr = KSPSetOperators(snes->ksp,snes->jacobian,snes->jacobian_pre);CHKERRQ(ierr);
923   ierr = KSPSetFromOptions(snes->ksp);CHKERRQ(ierr);
924 
925   /* if someone has set the SNES NPC type, create it. */
926   ierr = SNESGetOptionsPrefix(snes, &optionsprefix);CHKERRQ(ierr);
927   ierr = PetscOptionsHasName(optionsprefix, "-npc_snes_type", &pcset);CHKERRQ(ierr);
928   if (pcset && (!snes->pc)) {
929     ierr = SNESGetNPC(snes, &snes->pc);CHKERRQ(ierr);
930   }
931   PetscFunctionReturn(0);
932 }
933 
934 #undef __FUNCT__
935 #define __FUNCT__ "SNESSetComputeApplicationContext"
936 /*@C
937    SNESSetComputeApplicationContext - Sets an optional function to compute a user-defined context for
938    the nonlinear solvers.
939 
940    Logically Collective on SNES
941 
942    Input Parameters:
943 +  snes - the SNES context
944 .  compute - function to compute the context
945 -  destroy - function to destroy the context
946 
947    Level: intermediate
948 
949    Notes:
950    This function is currently not available from Fortran.
951 
952 .keywords: SNES, nonlinear, set, application, context
953 
954 .seealso: SNESGetApplicationContext(), SNESSetComputeApplicationContext(), SNESGetApplicationContext()
955 @*/
956 PetscErrorCode  SNESSetComputeApplicationContext(SNES snes,PetscErrorCode (*compute)(SNES,void**),PetscErrorCode (*destroy)(void**))
957 {
958   PetscFunctionBegin;
959   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
960   snes->ops->usercompute = compute;
961   snes->ops->userdestroy = destroy;
962   PetscFunctionReturn(0);
963 }
964 
965 #undef __FUNCT__
966 #define __FUNCT__ "SNESSetApplicationContext"
967 /*@
968    SNESSetApplicationContext - Sets the optional user-defined context for
969    the nonlinear solvers.
970 
971    Logically Collective on SNES
972 
973    Input Parameters:
974 +  snes - the SNES context
975 -  usrP - optional user context
976 
977    Level: intermediate
978 
979 .keywords: SNES, nonlinear, set, application, context
980 
981 .seealso: SNESGetApplicationContext()
982 @*/
983 PetscErrorCode  SNESSetApplicationContext(SNES snes,void *usrP)
984 {
985   PetscErrorCode ierr;
986   KSP            ksp;
987 
988   PetscFunctionBegin;
989   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
990   ierr       = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
991   ierr       = KSPSetApplicationContext(ksp,usrP);CHKERRQ(ierr);
992   snes->user = usrP;
993   PetscFunctionReturn(0);
994 }
995 
996 #undef __FUNCT__
997 #define __FUNCT__ "SNESGetApplicationContext"
998 /*@
999    SNESGetApplicationContext - Gets the user-defined context for the
1000    nonlinear solvers.
1001 
1002    Not Collective
1003 
1004    Input Parameter:
1005 .  snes - SNES context
1006 
1007    Output Parameter:
1008 .  usrP - user context
1009 
1010    Level: intermediate
1011 
1012 .keywords: SNES, nonlinear, get, application, context
1013 
1014 .seealso: SNESSetApplicationContext()
1015 @*/
1016 PetscErrorCode  SNESGetApplicationContext(SNES snes,void *usrP)
1017 {
1018   PetscFunctionBegin;
1019   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1020   *(void**)usrP = snes->user;
1021   PetscFunctionReturn(0);
1022 }
1023 
1024 #undef __FUNCT__
1025 #define __FUNCT__ "SNESGetIterationNumber"
1026 /*@
1027    SNESGetIterationNumber - Gets the number of nonlinear iterations completed
1028    at this time.
1029 
1030    Not Collective
1031 
1032    Input Parameter:
1033 .  snes - SNES context
1034 
1035    Output Parameter:
1036 .  iter - iteration number
1037 
1038    Notes:
1039    For example, during the computation of iteration 2 this would return 1.
1040 
1041    This is useful for using lagged Jacobians (where one does not recompute the
1042    Jacobian at each SNES iteration). For example, the code
1043 .vb
1044       ierr = SNESGetIterationNumber(snes,&it);
1045       if (!(it % 2)) {
1046         [compute Jacobian here]
1047       }
1048 .ve
1049    can be used in your ComputeJacobian() function to cause the Jacobian to be
1050    recomputed every second SNES iteration.
1051 
1052    Level: intermediate
1053 
1054 .keywords: SNES, nonlinear, get, iteration, number,
1055 
1056 .seealso:   SNESGetLinearSolveIterations()
1057 @*/
1058 PetscErrorCode  SNESGetIterationNumber(SNES snes,PetscInt *iter)
1059 {
1060   PetscFunctionBegin;
1061   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1062   PetscValidIntPointer(iter,2);
1063   *iter = snes->iter;
1064   PetscFunctionReturn(0);
1065 }
1066 
1067 #undef __FUNCT__
1068 #define __FUNCT__ "SNESSetIterationNumber"
1069 /*@
1070    SNESSetIterationNumber - Sets the current iteration number.
1071 
1072    Not Collective
1073 
1074    Input Parameter:
1075 .  snes - SNES context
1076 .  iter - iteration number
1077 
1078    Level: developer
1079 
1080 .keywords: SNES, nonlinear, set, iteration, number,
1081 
1082 .seealso:   SNESGetLinearSolveIterations()
1083 @*/
1084 PetscErrorCode  SNESSetIterationNumber(SNES snes,PetscInt iter)
1085 {
1086   PetscErrorCode ierr;
1087 
1088   PetscFunctionBegin;
1089   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1090   ierr       = PetscObjectSAWsTakeAccess((PetscObject)snes);CHKERRQ(ierr);
1091   snes->iter = iter;
1092   ierr       = PetscObjectSAWsGrantAccess((PetscObject)snes);CHKERRQ(ierr);
1093   PetscFunctionReturn(0);
1094 }
1095 
1096 #undef __FUNCT__
1097 #define __FUNCT__ "SNESGetNonlinearStepFailures"
1098 /*@
1099    SNESGetNonlinearStepFailures - Gets the number of unsuccessful steps
1100    attempted by the nonlinear solver.
1101 
1102    Not Collective
1103 
1104    Input Parameter:
1105 .  snes - SNES context
1106 
1107    Output Parameter:
1108 .  nfails - number of unsuccessful steps attempted
1109 
1110    Notes:
1111    This counter is reset to zero for each successive call to SNESSolve().
1112 
1113    Level: intermediate
1114 
1115 .keywords: SNES, nonlinear, get, number, unsuccessful, steps
1116 
1117 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
1118           SNESSetMaxNonlinearStepFailures(), SNESGetMaxNonlinearStepFailures()
1119 @*/
1120 PetscErrorCode  SNESGetNonlinearStepFailures(SNES snes,PetscInt *nfails)
1121 {
1122   PetscFunctionBegin;
1123   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1124   PetscValidIntPointer(nfails,2);
1125   *nfails = snes->numFailures;
1126   PetscFunctionReturn(0);
1127 }
1128 
1129 #undef __FUNCT__
1130 #define __FUNCT__ "SNESSetMaxNonlinearStepFailures"
1131 /*@
1132    SNESSetMaxNonlinearStepFailures - Sets the maximum number of unsuccessful steps
1133    attempted by the nonlinear solver before it gives up.
1134 
1135    Not Collective
1136 
1137    Input Parameters:
1138 +  snes     - SNES context
1139 -  maxFails - maximum of unsuccessful steps
1140 
1141    Level: intermediate
1142 
1143 .keywords: SNES, nonlinear, set, maximum, unsuccessful, steps
1144 
1145 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
1146           SNESGetMaxNonlinearStepFailures(), SNESGetNonlinearStepFailures()
1147 @*/
1148 PetscErrorCode  SNESSetMaxNonlinearStepFailures(SNES snes, PetscInt maxFails)
1149 {
1150   PetscFunctionBegin;
1151   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1152   snes->maxFailures = maxFails;
1153   PetscFunctionReturn(0);
1154 }
1155 
1156 #undef __FUNCT__
1157 #define __FUNCT__ "SNESGetMaxNonlinearStepFailures"
1158 /*@
1159    SNESGetMaxNonlinearStepFailures - Gets the maximum number of unsuccessful steps
1160    attempted by the nonlinear solver before it gives up.
1161 
1162    Not Collective
1163 
1164    Input Parameter:
1165 .  snes     - SNES context
1166 
1167    Output Parameter:
1168 .  maxFails - maximum of unsuccessful steps
1169 
1170    Level: intermediate
1171 
1172 .keywords: SNES, nonlinear, get, maximum, unsuccessful, steps
1173 
1174 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
1175           SNESSetMaxNonlinearStepFailures(), SNESGetNonlinearStepFailures()
1176 
1177 @*/
1178 PetscErrorCode  SNESGetMaxNonlinearStepFailures(SNES snes, PetscInt *maxFails)
1179 {
1180   PetscFunctionBegin;
1181   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1182   PetscValidIntPointer(maxFails,2);
1183   *maxFails = snes->maxFailures;
1184   PetscFunctionReturn(0);
1185 }
1186 
1187 #undef __FUNCT__
1188 #define __FUNCT__ "SNESGetNumberFunctionEvals"
1189 /*@
1190    SNESGetNumberFunctionEvals - Gets the number of user provided function evaluations
1191      done by SNES.
1192 
1193    Not Collective
1194 
1195    Input Parameter:
1196 .  snes     - SNES context
1197 
1198    Output Parameter:
1199 .  nfuncs - number of evaluations
1200 
1201    Level: intermediate
1202 
1203    Notes: Reset every time SNESSolve is called unless SNESSetCountersReset() is used.
1204 
1205 .keywords: SNES, nonlinear, get, maximum, unsuccessful, steps
1206 
1207 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(), SNESSetCountersReset()
1208 @*/
1209 PetscErrorCode  SNESGetNumberFunctionEvals(SNES snes, PetscInt *nfuncs)
1210 {
1211   PetscFunctionBegin;
1212   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1213   PetscValidIntPointer(nfuncs,2);
1214   *nfuncs = snes->nfuncs;
1215   PetscFunctionReturn(0);
1216 }
1217 
1218 #undef __FUNCT__
1219 #define __FUNCT__ "SNESGetLinearSolveFailures"
1220 /*@
1221    SNESGetLinearSolveFailures - Gets the number of failed (non-converged)
1222    linear solvers.
1223 
1224    Not Collective
1225 
1226    Input Parameter:
1227 .  snes - SNES context
1228 
1229    Output Parameter:
1230 .  nfails - number of failed solves
1231 
1232    Level: intermediate
1233 
1234    Options Database Keys:
1235 . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated
1236 
1237    Notes:
1238    This counter is reset to zero for each successive call to SNESSolve().
1239 
1240 .keywords: SNES, nonlinear, get, number, unsuccessful, steps
1241 
1242 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures()
1243 @*/
1244 PetscErrorCode  SNESGetLinearSolveFailures(SNES snes,PetscInt *nfails)
1245 {
1246   PetscFunctionBegin;
1247   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1248   PetscValidIntPointer(nfails,2);
1249   *nfails = snes->numLinearSolveFailures;
1250   PetscFunctionReturn(0);
1251 }
1252 
1253 #undef __FUNCT__
1254 #define __FUNCT__ "SNESSetMaxLinearSolveFailures"
1255 /*@
1256    SNESSetMaxLinearSolveFailures - the number of failed linear solve attempts
1257    allowed before SNES returns with a diverged reason of SNES_DIVERGED_LINEAR_SOLVE
1258 
1259    Logically Collective on SNES
1260 
1261    Input Parameters:
1262 +  snes     - SNES context
1263 -  maxFails - maximum allowed linear solve failures
1264 
1265    Level: intermediate
1266 
1267    Options Database Keys:
1268 . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated
1269 
1270    Notes: By default this is 0; that is SNES returns on the first failed linear solve
1271 
1272 .keywords: SNES, nonlinear, set, maximum, unsuccessful, steps
1273 
1274 .seealso: SNESGetLinearSolveFailures(), SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations()
1275 @*/
1276 PetscErrorCode  SNESSetMaxLinearSolveFailures(SNES snes, PetscInt maxFails)
1277 {
1278   PetscFunctionBegin;
1279   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1280   PetscValidLogicalCollectiveInt(snes,maxFails,2);
1281   snes->maxLinearSolveFailures = maxFails;
1282   PetscFunctionReturn(0);
1283 }
1284 
1285 #undef __FUNCT__
1286 #define __FUNCT__ "SNESGetMaxLinearSolveFailures"
1287 /*@
1288    SNESGetMaxLinearSolveFailures - gets the maximum number of linear solve failures that
1289      are allowed before SNES terminates
1290 
1291    Not Collective
1292 
1293    Input Parameter:
1294 .  snes     - SNES context
1295 
1296    Output Parameter:
1297 .  maxFails - maximum of unsuccessful solves allowed
1298 
1299    Level: intermediate
1300 
1301    Notes: By default this is 1; that is SNES returns on the first failed linear solve
1302 
1303 .keywords: SNES, nonlinear, get, maximum, unsuccessful, steps
1304 
1305 .seealso: SNESGetLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(),
1306 @*/
1307 PetscErrorCode  SNESGetMaxLinearSolveFailures(SNES snes, PetscInt *maxFails)
1308 {
1309   PetscFunctionBegin;
1310   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1311   PetscValidIntPointer(maxFails,2);
1312   *maxFails = snes->maxLinearSolveFailures;
1313   PetscFunctionReturn(0);
1314 }
1315 
1316 #undef __FUNCT__
1317 #define __FUNCT__ "SNESGetLinearSolveIterations"
1318 /*@
1319    SNESGetLinearSolveIterations - Gets the total number of linear iterations
1320    used by the nonlinear solver.
1321 
1322    Not Collective
1323 
1324    Input Parameter:
1325 .  snes - SNES context
1326 
1327    Output Parameter:
1328 .  lits - number of linear iterations
1329 
1330    Notes:
1331    This counter is reset to zero for each successive call to SNESSolve() unless SNESSetCountersReset() is used.
1332 
1333    Level: intermediate
1334 
1335 .keywords: SNES, nonlinear, get, number, linear, iterations
1336 
1337 .seealso:  SNESGetIterationNumber(), SNESGetLinearSolveFailures(), SNESGetMaxLinearSolveFailures(), SNESSetCountersReset()
1338 @*/
1339 PetscErrorCode  SNESGetLinearSolveIterations(SNES snes,PetscInt *lits)
1340 {
1341   PetscFunctionBegin;
1342   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1343   PetscValidIntPointer(lits,2);
1344   *lits = snes->linear_its;
1345   PetscFunctionReturn(0);
1346 }
1347 
1348 #undef __FUNCT__
1349 #define __FUNCT__ "SNESSetCountersReset"
1350 /*@
1351    SNESSetCountersReset - Sets whether or not the counters for linear iterations and function evaluations
1352    are reset every time SNESSolve() is called.
1353 
1354    Logically Collective on SNES
1355 
1356    Input Parameter:
1357 +  snes - SNES context
1358 -  reset - whether to reset the counters or not
1359 
1360    Notes:
1361    This defaults to PETSC_TRUE
1362 
1363    Level: developer
1364 
1365 .keywords: SNES, nonlinear, set, reset, number, linear, iterations
1366 
1367 .seealso:  SNESGetNumberFunctionEvals(), SNESGetLinearSolveIterations(), SNESGetNPC()
1368 @*/
1369 PetscErrorCode  SNESSetCountersReset(SNES snes,PetscBool reset)
1370 {
1371   PetscFunctionBegin;
1372   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1373   PetscValidLogicalCollectiveBool(snes,reset,2);
1374   snes->counters_reset = reset;
1375   PetscFunctionReturn(0);
1376 }
1377 
1378 
1379 #undef __FUNCT__
1380 #define __FUNCT__ "SNESSetKSP"
1381 /*@
1382    SNESSetKSP - Sets a KSP context for the SNES object to use
1383 
1384    Not Collective, but the SNES and KSP objects must live on the same MPI_Comm
1385 
1386    Input Parameters:
1387 +  snes - the SNES context
1388 -  ksp - the KSP context
1389 
1390    Notes:
1391    The SNES object already has its KSP object, you can obtain with SNESGetKSP()
1392    so this routine is rarely needed.
1393 
1394    The KSP object that is already in the SNES object has its reference count
1395    decreased by one.
1396 
1397    Level: developer
1398 
1399 .keywords: SNES, nonlinear, get, KSP, context
1400 
1401 .seealso: KSPGetPC(), SNESCreate(), KSPCreate(), SNESSetKSP()
1402 @*/
1403 PetscErrorCode  SNESSetKSP(SNES snes,KSP ksp)
1404 {
1405   PetscErrorCode ierr;
1406 
1407   PetscFunctionBegin;
1408   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1409   PetscValidHeaderSpecific(ksp,KSP_CLASSID,2);
1410   PetscCheckSameComm(snes,1,ksp,2);
1411   ierr = PetscObjectReference((PetscObject)ksp);CHKERRQ(ierr);
1412   if (snes->ksp) {ierr = PetscObjectDereference((PetscObject)snes->ksp);CHKERRQ(ierr);}
1413   snes->ksp = ksp;
1414   PetscFunctionReturn(0);
1415 }
1416 
1417 /* -----------------------------------------------------------*/
1418 #undef __FUNCT__
1419 #define __FUNCT__ "SNESCreate"
1420 /*@
1421    SNESCreate - Creates a nonlinear solver context.
1422 
1423    Collective on MPI_Comm
1424 
1425    Input Parameters:
1426 .  comm - MPI communicator
1427 
1428    Output Parameter:
1429 .  outsnes - the new SNES context
1430 
1431    Options Database Keys:
1432 +   -snes_mf - Activates default matrix-free Jacobian-vector products,
1433                and no preconditioning matrix
1434 .   -snes_mf_operator - Activates default matrix-free Jacobian-vector
1435                products, and a user-provided preconditioning matrix
1436                as set by SNESSetJacobian()
1437 -   -snes_fd - Uses (slow!) finite differences to compute Jacobian
1438 
1439    Level: beginner
1440 
1441 .keywords: SNES, nonlinear, create, context
1442 
1443 .seealso: SNESSolve(), SNESDestroy(), SNES, SNESSetLagPreconditioner()
1444 
1445 @*/
1446 PetscErrorCode  SNESCreate(MPI_Comm comm,SNES *outsnes)
1447 {
1448   PetscErrorCode ierr;
1449   SNES           snes;
1450   SNESKSPEW      *kctx;
1451 
1452   PetscFunctionBegin;
1453   PetscValidPointer(outsnes,2);
1454   *outsnes = NULL;
1455   ierr = SNESInitializePackage();CHKERRQ(ierr);
1456 
1457   ierr = PetscHeaderCreate(snes,SNES_CLASSID,"SNES","Nonlinear solver","SNES",comm,SNESDestroy,SNESView);CHKERRQ(ierr);
1458 
1459   snes->ops->converged    = SNESConvergedDefault;
1460   snes->usesksp           = PETSC_TRUE;
1461   snes->tolerancesset     = PETSC_FALSE;
1462   snes->max_its           = 50;
1463   snes->max_funcs         = 10000;
1464   snes->norm              = 0.0;
1465   snes->normschedule      = SNES_NORM_ALWAYS;
1466   snes->functype          = SNES_FUNCTION_DEFAULT;
1467 #if defined(PETSC_USE_REAL_SINGLE)
1468   snes->rtol              = 1.e-5;
1469 #else
1470   snes->rtol              = 1.e-8;
1471 #endif
1472   snes->ttol              = 0.0;
1473 #if defined(PETSC_USE_REAL_SINGLE)
1474   snes->abstol            = 1.e-25;
1475 #else
1476   snes->abstol            = 1.e-50;
1477 #endif
1478   snes->stol              = 1.e-8;
1479 #if defined(PETSC_USE_REAL_SINGLE)
1480   snes->deltatol          = 1.e-6;
1481 #else
1482   snes->deltatol          = 1.e-12;
1483 #endif
1484   snes->nfuncs            = 0;
1485   snes->numFailures       = 0;
1486   snes->maxFailures       = 1;
1487   snes->linear_its        = 0;
1488   snes->lagjacobian       = 1;
1489   snes->jac_iter          = 0;
1490   snes->lagjac_persist    = PETSC_FALSE;
1491   snes->lagpreconditioner = 1;
1492   snes->pre_iter          = 0;
1493   snes->lagpre_persist    = PETSC_FALSE;
1494   snes->numbermonitors    = 0;
1495   snes->data              = 0;
1496   snes->setupcalled       = PETSC_FALSE;
1497   snes->ksp_ewconv        = PETSC_FALSE;
1498   snes->nwork             = 0;
1499   snes->work              = 0;
1500   snes->nvwork            = 0;
1501   snes->vwork             = 0;
1502   snes->conv_hist_len     = 0;
1503   snes->conv_hist_max     = 0;
1504   snes->conv_hist         = NULL;
1505   snes->conv_hist_its     = NULL;
1506   snes->conv_hist_reset   = PETSC_TRUE;
1507   snes->counters_reset    = PETSC_TRUE;
1508   snes->vec_func_init_set = PETSC_FALSE;
1509   snes->reason            = SNES_CONVERGED_ITERATING;
1510   snes->pcside            = PC_RIGHT;
1511 
1512   snes->mf          = PETSC_FALSE;
1513   snes->mf_operator = PETSC_FALSE;
1514   snes->mf_version  = 1;
1515 
1516   snes->numLinearSolveFailures = 0;
1517   snes->maxLinearSolveFailures = 1;
1518 
1519   snes->vizerotolerance = 1.e-8;
1520 
1521   /* Create context to compute Eisenstat-Walker relative tolerance for KSP */
1522   ierr = PetscNewLog(snes,&kctx);CHKERRQ(ierr);
1523 
1524   snes->kspconvctx  = (void*)kctx;
1525   kctx->version     = 2;
1526   kctx->rtol_0      = .3; /* Eisenstat and Walker suggest rtol_0=.5, but
1527                              this was too large for some test cases */
1528   kctx->rtol_last   = 0.0;
1529   kctx->rtol_max    = .9;
1530   kctx->gamma       = 1.0;
1531   kctx->alpha       = .5*(1.0 + PetscSqrtReal(5.0));
1532   kctx->alpha2      = kctx->alpha;
1533   kctx->threshold   = .1;
1534   kctx->lresid_last = 0.0;
1535   kctx->norm_last   = 0.0;
1536 
1537   *outsnes = snes;
1538   PetscFunctionReturn(0);
1539 }
1540 
1541 /*MC
1542     SNESFunction - Functional form used to convey the nonlinear function to be solved by SNES
1543 
1544      Synopsis:
1545      #include "petscsnes.h"
1546      PetscErrorCode SNESFunction(SNES snes,Vec x,Vec f,void *ctx);
1547 
1548      Input Parameters:
1549 +     snes - the SNES context
1550 .     x    - state at which to evaluate residual
1551 -     ctx     - optional user-defined function context, passed in with SNESSetFunction()
1552 
1553      Output Parameter:
1554 .     f  - vector to put residual (function value)
1555 
1556    Level: intermediate
1557 
1558 .seealso:   SNESSetFunction(), SNESGetFunction()
1559 M*/
1560 
1561 #undef __FUNCT__
1562 #define __FUNCT__ "SNESSetFunction"
1563 /*@C
1564    SNESSetFunction - Sets the function evaluation routine and function
1565    vector for use by the SNES routines in solving systems of nonlinear
1566    equations.
1567 
1568    Logically Collective on SNES
1569 
1570    Input Parameters:
1571 +  snes - the SNES context
1572 .  r - vector to store function value
1573 .  f - function evaluation routine; see SNESFunction for calling sequence details
1574 -  ctx - [optional] user-defined context for private data for the
1575          function evaluation routine (may be NULL)
1576 
1577    Notes:
1578    The Newton-like methods typically solve linear systems of the form
1579 $      f'(x) x = -f(x),
1580    where f'(x) denotes the Jacobian matrix and f(x) is the function.
1581 
1582    Level: beginner
1583 
1584 .keywords: SNES, nonlinear, set, function
1585 
1586 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetPicard(), SNESFunction
1587 @*/
1588 PetscErrorCode  SNESSetFunction(SNES snes,Vec r,PetscErrorCode (*f)(SNES,Vec,Vec,void*),void *ctx)
1589 {
1590   PetscErrorCode ierr;
1591   DM             dm;
1592 
1593   PetscFunctionBegin;
1594   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1595   if (r) {
1596     PetscValidHeaderSpecific(r,VEC_CLASSID,2);
1597     PetscCheckSameComm(snes,1,r,2);
1598     ierr = PetscObjectReference((PetscObject)r);CHKERRQ(ierr);
1599     ierr = VecDestroy(&snes->vec_func);CHKERRQ(ierr);
1600 
1601     snes->vec_func = r;
1602   }
1603   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1604   ierr = DMSNESSetFunction(dm,f,ctx);CHKERRQ(ierr);
1605   PetscFunctionReturn(0);
1606 }
1607 
1608 
1609 #undef __FUNCT__
1610 #define __FUNCT__ "SNESSetInitialFunction"
1611 /*@C
1612    SNESSetInitialFunction - Sets the function vector to be used as the
1613    function norm at the initialization of the method.  In some
1614    instances, the user has precomputed the function before calling
1615    SNESSolve.  This function allows one to avoid a redundant call
1616    to SNESComputeFunction in that case.
1617 
1618    Logically Collective on SNES
1619 
1620    Input Parameters:
1621 +  snes - the SNES context
1622 -  f - vector to store function value
1623 
1624    Notes:
1625    This should not be modified during the solution procedure.
1626 
1627    This is used extensively in the SNESFAS hierarchy and in nonlinear preconditioning.
1628 
1629    Level: developer
1630 
1631 .keywords: SNES, nonlinear, set, function
1632 
1633 .seealso: SNESSetFunction(), SNESComputeFunction(), SNESSetInitialFunctionNorm()
1634 @*/
1635 PetscErrorCode  SNESSetInitialFunction(SNES snes, Vec f)
1636 {
1637   PetscErrorCode ierr;
1638   Vec            vec_func;
1639 
1640   PetscFunctionBegin;
1641   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1642   PetscValidHeaderSpecific(f,VEC_CLASSID,2);
1643   PetscCheckSameComm(snes,1,f,2);
1644   if (snes->pcside == PC_LEFT && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
1645     snes->vec_func_init_set = PETSC_FALSE;
1646     PetscFunctionReturn(0);
1647   }
1648   ierr = SNESGetFunction(snes,&vec_func,NULL,NULL);CHKERRQ(ierr);
1649   ierr = VecCopy(f, vec_func);CHKERRQ(ierr);
1650 
1651   snes->vec_func_init_set = PETSC_TRUE;
1652   PetscFunctionReturn(0);
1653 }
1654 
1655 #undef __FUNCT__
1656 #define __FUNCT__ "SNESSetNormSchedule"
1657 /*@
1658    SNESSetNormSchedule - Sets the SNESNormSchedule used in covergence and monitoring
1659    of the SNES method.
1660 
1661    Logically Collective on SNES
1662 
1663    Input Parameters:
1664 +  snes - the SNES context
1665 -  normschedule - the frequency of norm computation
1666 
1667    Options Database Key:
1668 .  -snes_norm_schedule <none, always, initialonly, finalonly, initalfinalonly>
1669 
1670    Notes:
1671    Only certain SNES methods support certain SNESNormSchedules.  Most require evaluation
1672    of the nonlinear function and the taking of its norm at every iteration to
1673    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
1674    (SNESNGS) and the like do not require the norm of the function to be computed, and therfore
1675    may either be monitored for convergence or not.  As these are often used as nonlinear
1676    preconditioners, monitoring the norm of their error is not a useful enterprise within
1677    their solution.
1678 
1679    Level: developer
1680 
1681 .keywords: SNES, nonlinear, set, function, norm, type
1682 
1683 .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1684 @*/
1685 PetscErrorCode  SNESSetNormSchedule(SNES snes, SNESNormSchedule normschedule)
1686 {
1687   PetscFunctionBegin;
1688   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1689   snes->normschedule = normschedule;
1690   PetscFunctionReturn(0);
1691 }
1692 
1693 
1694 #undef __FUNCT__
1695 #define __FUNCT__ "SNESGetNormSchedule"
1696 /*@
1697    SNESGetNormSchedule - Gets the SNESNormSchedule used in covergence and monitoring
1698    of the SNES method.
1699 
1700    Logically Collective on SNES
1701 
1702    Input Parameters:
1703 +  snes - the SNES context
1704 -  normschedule - the type of the norm used
1705 
1706    Level: advanced
1707 
1708 .keywords: SNES, nonlinear, set, function, norm, type
1709 
1710 .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1711 @*/
1712 PetscErrorCode  SNESGetNormSchedule(SNES snes, SNESNormSchedule *normschedule)
1713 {
1714   PetscFunctionBegin;
1715   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1716   *normschedule = snes->normschedule;
1717   PetscFunctionReturn(0);
1718 }
1719 
1720 
1721 #undef __FUNCT__
1722 #define __FUNCT__ "SNESSetFunctionType"
1723 /*@C
1724    SNESSetFunctionType - Sets the SNESNormSchedule used in covergence and monitoring
1725    of the SNES method.
1726 
1727    Logically Collective on SNES
1728 
1729    Input Parameters:
1730 +  snes - the SNES context
1731 -  normschedule - the frequency of norm computation
1732 
1733    Notes:
1734    Only certain SNES methods support certain SNESNormSchedules.  Most require evaluation
1735    of the nonlinear function and the taking of its norm at every iteration to
1736    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
1737    (SNESNGS) and the like do not require the norm of the function to be computed, and therfore
1738    may either be monitored for convergence or not.  As these are often used as nonlinear
1739    preconditioners, monitoring the norm of their error is not a useful enterprise within
1740    their solution.
1741 
1742    Level: developer
1743 
1744 .keywords: SNES, nonlinear, set, function, norm, type
1745 
1746 .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1747 @*/
1748 PetscErrorCode  SNESSetFunctionType(SNES snes, SNESFunctionType type)
1749 {
1750   PetscFunctionBegin;
1751   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1752   snes->functype = type;
1753   PetscFunctionReturn(0);
1754 }
1755 
1756 
1757 #undef __FUNCT__
1758 #define __FUNCT__ "SNESGetFunctionType"
1759 /*@C
1760    SNESGetFunctionType - Gets the SNESNormSchedule used in covergence and monitoring
1761    of the SNES method.
1762 
1763    Logically Collective on SNES
1764 
1765    Input Parameters:
1766 +  snes - the SNES context
1767 -  normschedule - the type of the norm used
1768 
1769    Level: advanced
1770 
1771 .keywords: SNES, nonlinear, set, function, norm, type
1772 
1773 .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1774 @*/
1775 PetscErrorCode  SNESGetFunctionType(SNES snes, SNESFunctionType *type)
1776 {
1777   PetscFunctionBegin;
1778   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1779   *type = snes->functype;
1780   PetscFunctionReturn(0);
1781 }
1782 
1783 /*MC
1784     SNESNGSFunction - function used to convey a Gauss-Seidel sweep on the nonlinear function
1785 
1786      Synopsis:
1787      #include <petscsnes.h>
1788 $    SNESNGSFunction(SNES snes,Vec x,Vec b,void *ctx);
1789 
1790 +  X   - solution vector
1791 .  B   - RHS vector
1792 -  ctx - optional user-defined Gauss-Seidel context
1793 
1794    Level: intermediate
1795 
1796 .seealso:   SNESSetNGS(), SNESGetNGS()
1797 M*/
1798 
1799 #undef __FUNCT__
1800 #define __FUNCT__ "SNESSetNGS"
1801 /*@C
1802    SNESSetNGS - Sets the user nonlinear Gauss-Seidel routine for
1803    use with composed nonlinear solvers.
1804 
1805    Input Parameters:
1806 +  snes   - the SNES context
1807 .  f - function evaluation routine to apply Gauss-Seidel see SNESNGSFunction
1808 -  ctx    - [optional] user-defined context for private data for the
1809             smoother evaluation routine (may be NULL)
1810 
1811    Notes:
1812    The NGS routines are used by the composed nonlinear solver to generate
1813     a problem appropriate update to the solution, particularly FAS.
1814 
1815    Level: intermediate
1816 
1817 .keywords: SNES, nonlinear, set, Gauss-Seidel
1818 
1819 .seealso: SNESGetFunction(), SNESComputeNGS()
1820 @*/
1821 PetscErrorCode SNESSetNGS(SNES snes,PetscErrorCode (*f)(SNES,Vec,Vec,void*),void *ctx)
1822 {
1823   PetscErrorCode ierr;
1824   DM             dm;
1825 
1826   PetscFunctionBegin;
1827   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1828   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1829   ierr = DMSNESSetNGS(dm,f,ctx);CHKERRQ(ierr);
1830   PetscFunctionReturn(0);
1831 }
1832 
1833 #undef __FUNCT__
1834 #define __FUNCT__ "SNESPicardComputeFunction"
1835 PETSC_EXTERN PetscErrorCode SNESPicardComputeFunction(SNES snes,Vec x,Vec f,void *ctx)
1836 {
1837   PetscErrorCode ierr;
1838   DM             dm;
1839   DMSNES         sdm;
1840 
1841   PetscFunctionBegin;
1842   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1843   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
1844   /*  A(x)*x - b(x) */
1845   if (sdm->ops->computepfunction) {
1846     ierr = (*sdm->ops->computepfunction)(snes,x,f,sdm->pctx);CHKERRQ(ierr);
1847   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetPicard() to provide Picard function.");
1848 
1849   if (sdm->ops->computepjacobian) {
1850     ierr = (*sdm->ops->computepjacobian)(snes,x,snes->jacobian,snes->jacobian_pre,sdm->pctx);CHKERRQ(ierr);
1851   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetPicard() to provide Picard matrix.");
1852   ierr = VecScale(f,-1.0);CHKERRQ(ierr);
1853   ierr = MatMultAdd(snes->jacobian,x,f,f);CHKERRQ(ierr);
1854   PetscFunctionReturn(0);
1855 }
1856 
1857 #undef __FUNCT__
1858 #define __FUNCT__ "SNESPicardComputeJacobian"
1859 PETSC_EXTERN PetscErrorCode SNESPicardComputeJacobian(SNES snes,Vec x1,Mat J,Mat B,void *ctx)
1860 {
1861   PetscFunctionBegin;
1862   /* the jacobian matrix should be pre-filled in SNESPicardComputeFunction */
1863   PetscFunctionReturn(0);
1864 }
1865 
1866 #undef __FUNCT__
1867 #define __FUNCT__ "SNESSetPicard"
1868 /*@C
1869    SNESSetPicard - Use SNES to solve the semilinear-system A(x) x = b(x) via a Picard type iteration (Picard linearization)
1870 
1871    Logically Collective on SNES
1872 
1873    Input Parameters:
1874 +  snes - the SNES context
1875 .  r - vector to store function value
1876 .  b - function evaluation routine
1877 .  Amat - matrix with which A(x) x - b(x) is to be computed
1878 .  Pmat - matrix from which preconditioner is computed (usually the same as Amat)
1879 .  J  - function to compute matrix value, see SNESJacobianFunction for details on its calling sequence
1880 -  ctx - [optional] user-defined context for private data for the
1881          function evaluation routine (may be NULL)
1882 
1883    Notes:
1884     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
1885     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.
1886 
1887     One can call SNESSetPicard() or SNESSetFunction() (and possibly SNESSetJacobian()) but cannot call both
1888 
1889 $     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}
1890 $     Note that when an exact solver is used this corresponds to the "classic" Picard A(x^{n}) x^{n+1} = b(x^{n}) iteration.
1891 
1892      Run with -snes_mf_operator to solve the system with Newton's method using A(x^{n}) to construct the preconditioner.
1893 
1894    We implement the defect correction form of the Picard iteration because it converges much more generally when inexact linear solvers are used then
1895    the direct Picard iteration A(x^n) x^{n+1} = b(x^n)
1896 
1897    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
1898    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
1899    different please contact us at petsc-dev@mcs.anl.gov and we'll have an entirely new argument :-).
1900 
1901    Level: intermediate
1902 
1903 .keywords: SNES, nonlinear, set, function
1904 
1905 .seealso: SNESGetFunction(), SNESSetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESGetPicard(), SNESLineSearchPreCheckPicard(), SNESJacobianFunction
1906 @*/
1907 PetscErrorCode  SNESSetPicard(SNES snes,Vec r,PetscErrorCode (*b)(SNES,Vec,Vec,void*),Mat Amat, Mat Pmat, PetscErrorCode (*J)(SNES,Vec,Mat,Mat,void*),void *ctx)
1908 {
1909   PetscErrorCode ierr;
1910   DM             dm;
1911 
1912   PetscFunctionBegin;
1913   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1914   ierr = SNESGetDM(snes, &dm);CHKERRQ(ierr);
1915   ierr = DMSNESSetPicard(dm,b,J,ctx);CHKERRQ(ierr);
1916   ierr = SNESSetFunction(snes,r,SNESPicardComputeFunction,ctx);CHKERRQ(ierr);
1917   ierr = SNESSetJacobian(snes,Amat,Pmat,SNESPicardComputeJacobian,ctx);CHKERRQ(ierr);
1918   PetscFunctionReturn(0);
1919 }
1920 
1921 #undef __FUNCT__
1922 #define __FUNCT__ "SNESGetPicard"
1923 /*@C
1924    SNESGetPicard - Returns the context for the Picard iteration
1925 
1926    Not Collective, but Vec is parallel if SNES is parallel. Collective if Vec is requested, but has not been created yet.
1927 
1928    Input Parameter:
1929 .  snes - the SNES context
1930 
1931    Output Parameter:
1932 +  r - the function (or NULL)
1933 .  f - the function (or NULL); see SNESFunction for calling sequence details
1934 .  Amat - the matrix used to defined the operation A(x) x - b(x) (or NULL)
1935 .  Pmat  - the matrix from which the preconditioner will be constructed (or NULL)
1936 .  J - the function for matrix evaluation (or NULL); see SNESJacobianFunction for calling sequence details
1937 -  ctx - the function context (or NULL)
1938 
1939    Level: advanced
1940 
1941 .keywords: SNES, nonlinear, get, function
1942 
1943 .seealso: SNESSetPicard(), SNESGetFunction(), SNESGetJacobian(), SNESGetDM(), SNESFunction, SNESJacobianFunction
1944 @*/
1945 PetscErrorCode  SNESGetPicard(SNES snes,Vec *r,PetscErrorCode (**f)(SNES,Vec,Vec,void*),Mat *Amat, Mat *Pmat, PetscErrorCode (**J)(SNES,Vec,Mat,Mat,void*),void **ctx)
1946 {
1947   PetscErrorCode ierr;
1948   DM             dm;
1949 
1950   PetscFunctionBegin;
1951   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1952   ierr = SNESGetFunction(snes,r,NULL,NULL);CHKERRQ(ierr);
1953   ierr = SNESGetJacobian(snes,Amat,Pmat,NULL,NULL);CHKERRQ(ierr);
1954   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1955   ierr = DMSNESGetPicard(dm,f,J,ctx);CHKERRQ(ierr);
1956   PetscFunctionReturn(0);
1957 }
1958 
1959 #undef __FUNCT__
1960 #define __FUNCT__ "SNESSetComputeInitialGuess"
1961 /*@C
1962    SNESSetComputeInitialGuess - Sets a routine used to compute an initial guess for the problem
1963 
1964    Logically Collective on SNES
1965 
1966    Input Parameters:
1967 +  snes - the SNES context
1968 .  func - function evaluation routine
1969 -  ctx - [optional] user-defined context for private data for the
1970          function evaluation routine (may be NULL)
1971 
1972    Calling sequence of func:
1973 $    func (SNES snes,Vec x,void *ctx);
1974 
1975 .  f - function vector
1976 -  ctx - optional user-defined function context
1977 
1978    Level: intermediate
1979 
1980 .keywords: SNES, nonlinear, set, function
1981 
1982 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian()
1983 @*/
1984 PetscErrorCode  SNESSetComputeInitialGuess(SNES snes,PetscErrorCode (*func)(SNES,Vec,void*),void *ctx)
1985 {
1986   PetscFunctionBegin;
1987   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1988   if (func) snes->ops->computeinitialguess = func;
1989   if (ctx)  snes->initialguessP            = ctx;
1990   PetscFunctionReturn(0);
1991 }
1992 
1993 /* --------------------------------------------------------------- */
1994 #undef __FUNCT__
1995 #define __FUNCT__ "SNESGetRhs"
1996 /*@C
1997    SNESGetRhs - Gets the vector for solving F(x) = rhs. If rhs is not set
1998    it assumes a zero right hand side.
1999 
2000    Logically Collective on SNES
2001 
2002    Input Parameter:
2003 .  snes - the SNES context
2004 
2005    Output Parameter:
2006 .  rhs - the right hand side vector or NULL if the right hand side vector is null
2007 
2008    Level: intermediate
2009 
2010 .keywords: SNES, nonlinear, get, function, right hand side
2011 
2012 .seealso: SNESGetSolution(), SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction()
2013 @*/
2014 PetscErrorCode  SNESGetRhs(SNES snes,Vec *rhs)
2015 {
2016   PetscFunctionBegin;
2017   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2018   PetscValidPointer(rhs,2);
2019   *rhs = snes->vec_rhs;
2020   PetscFunctionReturn(0);
2021 }
2022 
2023 #undef __FUNCT__
2024 #define __FUNCT__ "SNESComputeFunction"
2025 /*@
2026    SNESComputeFunction - Calls the function that has been set with SNESSetFunction().
2027 
2028    Collective on SNES
2029 
2030    Input Parameters:
2031 +  snes - the SNES context
2032 -  x - input vector
2033 
2034    Output Parameter:
2035 .  y - function vector, as set by SNESSetFunction()
2036 
2037    Notes:
2038    SNESComputeFunction() is typically used within nonlinear solvers
2039    implementations, so most users would not generally call this routine
2040    themselves.
2041 
2042    Level: developer
2043 
2044 .keywords: SNES, nonlinear, compute, function
2045 
2046 .seealso: SNESSetFunction(), SNESGetFunction()
2047 @*/
2048 PetscErrorCode  SNESComputeFunction(SNES snes,Vec x,Vec y)
2049 {
2050   PetscErrorCode ierr;
2051   DM             dm;
2052   DMSNES         sdm;
2053 
2054   PetscFunctionBegin;
2055   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2056   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
2057   PetscValidHeaderSpecific(y,VEC_CLASSID,3);
2058   PetscCheckSameComm(snes,1,x,2);
2059   PetscCheckSameComm(snes,1,y,3);
2060   ierr = VecValidValues(x,2,PETSC_TRUE);CHKERRQ(ierr);
2061 
2062   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2063   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2064   if (sdm->ops->computefunction) {
2065     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) {
2066       ierr = PetscLogEventBegin(SNES_FunctionEval,snes,x,y,0);CHKERRQ(ierr);
2067     }
2068     ierr = VecLockPush(x);CHKERRQ(ierr);
2069     PetscStackPush("SNES user function");
2070     ierr = (*sdm->ops->computefunction)(snes,x,y,sdm->functionctx);CHKERRQ(ierr);
2071     PetscStackPop;
2072     ierr = VecLockPop(x);CHKERRQ(ierr);
2073     if (sdm->ops->computefunction != SNESObjectiveComputeFunctionDefaultFD) {
2074       ierr = PetscLogEventEnd(SNES_FunctionEval,snes,x,y,0);CHKERRQ(ierr);
2075     }
2076   } else if (snes->vec_rhs) {
2077     ierr = MatMult(snes->jacobian, x, y);CHKERRQ(ierr);
2078   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetFunction() or SNESSetDM() before SNESComputeFunction(), likely called from SNESSolve().");
2079   if (snes->vec_rhs) {
2080     ierr = VecAXPY(y,-1.0,snes->vec_rhs);CHKERRQ(ierr);
2081   }
2082   snes->nfuncs++;
2083   /*
2084      domainerror might not be set on all processes; so we tag vector locally with Inf and the next inner product or norm will
2085      propagate the value to all processes
2086   */
2087   if (snes->domainerror) {
2088     ierr = VecSetInf(y);CHKERRQ(ierr);
2089   }
2090   PetscFunctionReturn(0);
2091 }
2092 
2093 #undef __FUNCT__
2094 #define __FUNCT__ "SNESComputeNGS"
2095 /*@
2096    SNESComputeNGS - Calls the Gauss-Seidel function that has been set with  SNESSetNGS().
2097 
2098    Collective on SNES
2099 
2100    Input Parameters:
2101 +  snes - the SNES context
2102 .  x - input vector
2103 -  b - rhs vector
2104 
2105    Output Parameter:
2106 .  x - new solution vector
2107 
2108    Notes:
2109    SNESComputeNGS() is typically used within composed nonlinear solver
2110    implementations, so most users would not generally call this routine
2111    themselves.
2112 
2113    Level: developer
2114 
2115 .keywords: SNES, nonlinear, compute, function
2116 
2117 .seealso: SNESSetNGS(), SNESComputeFunction()
2118 @*/
2119 PetscErrorCode  SNESComputeNGS(SNES snes,Vec b,Vec x)
2120 {
2121   PetscErrorCode ierr;
2122   DM             dm;
2123   DMSNES         sdm;
2124 
2125   PetscFunctionBegin;
2126   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2127   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
2128   if (b) PetscValidHeaderSpecific(b,VEC_CLASSID,3);
2129   PetscCheckSameComm(snes,1,x,2);
2130   if (b) PetscCheckSameComm(snes,1,b,3);
2131   if (b) {ierr = VecValidValues(b,2,PETSC_TRUE);CHKERRQ(ierr);}
2132   ierr = PetscLogEventBegin(SNES_NGSEval,snes,x,b,0);CHKERRQ(ierr);
2133   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2134   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2135   if (sdm->ops->computegs) {
2136     if (b) {ierr = VecLockPush(b);CHKERRQ(ierr);}
2137     PetscStackPush("SNES user NGS");
2138     ierr = (*sdm->ops->computegs)(snes,x,b,sdm->gsctx);CHKERRQ(ierr);
2139     PetscStackPop;
2140     if (b) {ierr = VecLockPop(b);CHKERRQ(ierr);}
2141   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetNGS() before SNESComputeNGS(), likely called from SNESSolve().");
2142   ierr = PetscLogEventEnd(SNES_NGSEval,snes,x,b,0);CHKERRQ(ierr);
2143   PetscFunctionReturn(0);
2144 }
2145 
2146 #undef __FUNCT__
2147 #define __FUNCT__ "SNESComputeJacobian"
2148 /*@
2149    SNESComputeJacobian - Computes the Jacobian matrix that has been set with SNESSetJacobian().
2150 
2151    Collective on SNES and Mat
2152 
2153    Input Parameters:
2154 +  snes - the SNES context
2155 -  x - input vector
2156 
2157    Output Parameters:
2158 +  A - Jacobian matrix
2159 -  B - optional preconditioning matrix
2160 
2161   Options Database Keys:
2162 +    -snes_lag_preconditioner <lag>
2163 .    -snes_lag_jacobian <lag>
2164 .    -snes_compare_explicit - Compare the computed Jacobian to the finite difference Jacobian and output the differences
2165 .    -snes_compare_explicit_draw  - Compare the computed Jacobian to the finite difference Jacobian and draw the result
2166 .    -snes_compare_explicit_contour  - Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
2167 .    -snes_compare_operator  - Make the comparison options above use the operator instead of the preconditioning matrix
2168 .    -snes_compare_coloring - Compute the finite differece Jacobian using coloring and display norms of difference
2169 .    -snes_compare_coloring_display - Compute the finite differece Jacobian using coloring and display verbose differences
2170 .    -snes_compare_coloring_threshold - Display only those matrix entries that differ by more than a given threshold
2171 .    -snes_compare_coloring_threshold_atol - Absolute tolerance for difference in matrix entries to be displayed by -snes_compare_coloring_threshold
2172 .    -snes_compare_coloring_threshold_rtol - Relative tolerance for difference in matrix entries to be displayed by -snes_compare_coloring_threshold
2173 .    -snes_compare_coloring_draw - Compute the finite differece Jacobian using coloring and draw differences
2174 -    -snes_compare_coloring_draw_contour - Compute the finite differece Jacobian using coloring and show contours of matrices and differences
2175 
2176 
2177    Notes:
2178    Most users should not need to explicitly call this routine, as it
2179    is used internally within the nonlinear solvers.
2180 
2181    Level: developer
2182 
2183 .keywords: SNES, compute, Jacobian, matrix
2184 
2185 .seealso:  SNESSetJacobian(), KSPSetOperators(), MatStructure, SNESSetLagPreconditioner(), SNESSetLagJacobian()
2186 @*/
2187 PetscErrorCode  SNESComputeJacobian(SNES snes,Vec X,Mat A,Mat B)
2188 {
2189   PetscErrorCode ierr;
2190   PetscBool      flag;
2191   DM             dm;
2192   DMSNES         sdm;
2193   KSP            ksp;
2194 
2195   PetscFunctionBegin;
2196   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2197   PetscValidHeaderSpecific(X,VEC_CLASSID,2);
2198   PetscCheckSameComm(snes,1,X,2);
2199   ierr = VecValidValues(X,2,PETSC_TRUE);CHKERRQ(ierr);
2200   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2201   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2202 
2203   if (!sdm->ops->computejacobian) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_USER,"Must call SNESSetJacobian(), DMSNESSetJacobian(), DMDASNESSetJacobianLocal(), etc");
2204 
2205   /* make sure that MatAssemblyBegin/End() is called on A matrix if it is matrix free */
2206 
2207   if (snes->lagjacobian == -2) {
2208     snes->lagjacobian = -1;
2209 
2210     ierr = PetscInfo(snes,"Recomputing Jacobian/preconditioner because lag is -2 (means compute Jacobian, but then never again) \n");CHKERRQ(ierr);
2211   } else if (snes->lagjacobian == -1) {
2212     ierr = PetscInfo(snes,"Reusing Jacobian/preconditioner because lag is -1\n");CHKERRQ(ierr);
2213     ierr = PetscObjectTypeCompare((PetscObject)A,MATMFFD,&flag);CHKERRQ(ierr);
2214     if (flag) {
2215       ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2216       ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2217     }
2218     PetscFunctionReturn(0);
2219   } else if (snes->lagjacobian > 1 && (snes->iter + snes->jac_iter) % snes->lagjacobian) {
2220     ierr = PetscInfo2(snes,"Reusing Jacobian/preconditioner because lag is %D and SNES iteration is %D\n",snes->lagjacobian,snes->iter);CHKERRQ(ierr);
2221     ierr = PetscObjectTypeCompare((PetscObject)A,MATMFFD,&flag);CHKERRQ(ierr);
2222     if (flag) {
2223       ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2224       ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2225     }
2226     PetscFunctionReturn(0);
2227   }
2228   if (snes->pc && snes->pcside == PC_LEFT) {
2229       ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2230       ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2231       PetscFunctionReturn(0);
2232   }
2233 
2234   ierr = PetscLogEventBegin(SNES_JacobianEval,snes,X,A,B);CHKERRQ(ierr);
2235   ierr = VecLockPush(X);CHKERRQ(ierr);
2236   PetscStackPush("SNES user Jacobian function");
2237   ierr = (*sdm->ops->computejacobian)(snes,X,A,B,sdm->jacobianctx);CHKERRQ(ierr);
2238   PetscStackPop;
2239   ierr = VecLockPop(X);CHKERRQ(ierr);
2240   ierr = PetscLogEventEnd(SNES_JacobianEval,snes,X,A,B);CHKERRQ(ierr);
2241 
2242   /* the next line ensures that snes->ksp exists */
2243   ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
2244   if (snes->lagpreconditioner == -2) {
2245     ierr = PetscInfo(snes,"Rebuilding preconditioner exactly once since lag is -2\n");CHKERRQ(ierr);
2246     ierr = KSPSetReusePreconditioner(snes->ksp,PETSC_FALSE);CHKERRQ(ierr);
2247     snes->lagpreconditioner = -1;
2248   } else if (snes->lagpreconditioner == -1) {
2249     ierr = PetscInfo(snes,"Reusing preconditioner because lag is -1\n");CHKERRQ(ierr);
2250     ierr = KSPSetReusePreconditioner(snes->ksp,PETSC_TRUE);CHKERRQ(ierr);
2251   } else if (snes->lagpreconditioner > 1 && (snes->iter + snes->pre_iter) % snes->lagpreconditioner) {
2252     ierr = PetscInfo2(snes,"Reusing preconditioner because lag is %D and SNES iteration is %D\n",snes->lagpreconditioner,snes->iter);CHKERRQ(ierr);
2253     ierr = KSPSetReusePreconditioner(snes->ksp,PETSC_TRUE);CHKERRQ(ierr);
2254   } else {
2255     ierr = PetscInfo(snes,"Rebuilding preconditioner\n");CHKERRQ(ierr);
2256     ierr = KSPSetReusePreconditioner(snes->ksp,PETSC_FALSE);CHKERRQ(ierr);
2257   }
2258 
2259   /* make sure user returned a correct Jacobian and preconditioner */
2260   /* PetscValidHeaderSpecific(A,MAT_CLASSID,3);
2261     PetscValidHeaderSpecific(B,MAT_CLASSID,4);   */
2262   {
2263     PetscBool flag = PETSC_FALSE,flag_draw = PETSC_FALSE,flag_contour = PETSC_FALSE,flag_operator = PETSC_FALSE;
2264     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_explicit",&flag,NULL);CHKERRQ(ierr);
2265     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_explicit_draw",&flag_draw,NULL);CHKERRQ(ierr);
2266     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_explicit_draw_contour",&flag_contour,NULL);CHKERRQ(ierr);
2267     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_operator",&flag_operator,NULL);CHKERRQ(ierr);
2268     if (flag || flag_draw || flag_contour) {
2269       Mat          Bexp_mine = NULL,Bexp,FDexp;
2270       PetscViewer  vdraw,vstdout;
2271       PetscBool    flg;
2272       if (flag_operator) {
2273         ierr = MatComputeExplicitOperator(A,&Bexp_mine);CHKERRQ(ierr);
2274         Bexp = Bexp_mine;
2275       } else {
2276         /* See if the preconditioning matrix can be viewed and added directly */
2277         ierr = PetscObjectTypeCompareAny((PetscObject)B,&flg,MATSEQAIJ,MATMPIAIJ,MATSEQDENSE,MATMPIDENSE,MATSEQBAIJ,MATMPIBAIJ,MATSEQSBAIJ,MATMPIBAIJ,"");CHKERRQ(ierr);
2278         if (flg) Bexp = B;
2279         else {
2280           /* If the "preconditioning" matrix is itself MATSHELL or some other type without direct support */
2281           ierr = MatComputeExplicitOperator(B,&Bexp_mine);CHKERRQ(ierr);
2282           Bexp = Bexp_mine;
2283         }
2284       }
2285       ierr = MatConvert(Bexp,MATSAME,MAT_INITIAL_MATRIX,&FDexp);CHKERRQ(ierr);
2286       ierr = SNESComputeJacobianDefault(snes,X,FDexp,FDexp,NULL);CHKERRQ(ierr);
2287       ierr = PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&vstdout);CHKERRQ(ierr);
2288       if (flag_draw || flag_contour) {
2289         ierr = PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),0,"Explicit Jacobians",PETSC_DECIDE,PETSC_DECIDE,300,300,&vdraw);CHKERRQ(ierr);
2290         if (flag_contour) {ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);}
2291       } else vdraw = NULL;
2292       ierr = PetscViewerASCIIPrintf(vstdout,"Explicit %s\n",flag_operator ? "Jacobian" : "preconditioning Jacobian");CHKERRQ(ierr);
2293       if (flag) {ierr = MatView(Bexp,vstdout);CHKERRQ(ierr);}
2294       if (vdraw) {ierr = MatView(Bexp,vdraw);CHKERRQ(ierr);}
2295       ierr = PetscViewerASCIIPrintf(vstdout,"Finite difference Jacobian\n");CHKERRQ(ierr);
2296       if (flag) {ierr = MatView(FDexp,vstdout);CHKERRQ(ierr);}
2297       if (vdraw) {ierr = MatView(FDexp,vdraw);CHKERRQ(ierr);}
2298       ierr = MatAYPX(FDexp,-1.0,Bexp,SAME_NONZERO_PATTERN);CHKERRQ(ierr);
2299       ierr = PetscViewerASCIIPrintf(vstdout,"User-provided matrix minus finite difference Jacobian\n");CHKERRQ(ierr);
2300       if (flag) {ierr = MatView(FDexp,vstdout);CHKERRQ(ierr);}
2301       if (vdraw) {              /* Always use contour for the difference */
2302         ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);
2303         ierr = MatView(FDexp,vdraw);CHKERRQ(ierr);
2304         ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);
2305       }
2306       if (flag_contour) {ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);}
2307       ierr = PetscViewerDestroy(&vdraw);CHKERRQ(ierr);
2308       ierr = MatDestroy(&Bexp_mine);CHKERRQ(ierr);
2309       ierr = MatDestroy(&FDexp);CHKERRQ(ierr);
2310     }
2311   }
2312   {
2313     PetscBool flag = PETSC_FALSE,flag_display = PETSC_FALSE,flag_draw = PETSC_FALSE,flag_contour = PETSC_FALSE,flag_threshold = PETSC_FALSE;
2314     PetscReal threshold_atol = PETSC_SQRT_MACHINE_EPSILON,threshold_rtol = 10*PETSC_SQRT_MACHINE_EPSILON;
2315     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring",&flag,NULL);CHKERRQ(ierr);
2316     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_display",&flag_display,NULL);CHKERRQ(ierr);
2317     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_draw",&flag_draw,NULL);CHKERRQ(ierr);
2318     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_draw_contour",&flag_contour,NULL);CHKERRQ(ierr);
2319     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold",&flag_threshold,NULL);CHKERRQ(ierr);
2320     ierr = PetscOptionsGetReal(((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold_rtol",&threshold_rtol,NULL);CHKERRQ(ierr);
2321     ierr = PetscOptionsGetReal(((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold_atol",&threshold_atol,NULL);CHKERRQ(ierr);
2322     if (flag || flag_display || flag_draw || flag_contour || flag_threshold) {
2323       Mat            Bfd;
2324       PetscViewer    vdraw,vstdout;
2325       MatColoring    coloring;
2326       ISColoring     iscoloring;
2327       MatFDColoring  matfdcoloring;
2328       PetscErrorCode (*func)(SNES,Vec,Vec,void*);
2329       void           *funcctx;
2330       PetscReal      norm1,norm2,normmax;
2331 
2332       ierr = MatDuplicate(B,MAT_DO_NOT_COPY_VALUES,&Bfd);CHKERRQ(ierr);
2333       ierr = MatColoringCreate(Bfd,&coloring);CHKERRQ(ierr);
2334       ierr = MatColoringSetType(coloring,MATCOLORINGSL);CHKERRQ(ierr);
2335       ierr = MatColoringSetFromOptions(coloring);CHKERRQ(ierr);
2336       ierr = MatColoringApply(coloring,&iscoloring);CHKERRQ(ierr);
2337       ierr = MatColoringDestroy(&coloring);CHKERRQ(ierr);
2338       ierr = MatFDColoringCreate(Bfd,iscoloring,&matfdcoloring);CHKERRQ(ierr);
2339       ierr = MatFDColoringSetFromOptions(matfdcoloring);CHKERRQ(ierr);
2340       ierr = MatFDColoringSetUp(Bfd,iscoloring,matfdcoloring);CHKERRQ(ierr);
2341       ierr = ISColoringDestroy(&iscoloring);CHKERRQ(ierr);
2342 
2343       /* This method of getting the function is currently unreliable since it doesn't work for DM local functions. */
2344       ierr = SNESGetFunction(snes,NULL,&func,&funcctx);CHKERRQ(ierr);
2345       ierr = MatFDColoringSetFunction(matfdcoloring,(PetscErrorCode (*)(void))func,funcctx);CHKERRQ(ierr);
2346       ierr = PetscObjectSetOptionsPrefix((PetscObject)matfdcoloring,((PetscObject)snes)->prefix);CHKERRQ(ierr);
2347       ierr = PetscObjectAppendOptionsPrefix((PetscObject)matfdcoloring,"coloring_");CHKERRQ(ierr);
2348       ierr = MatFDColoringSetFromOptions(matfdcoloring);CHKERRQ(ierr);
2349       ierr = MatFDColoringApply(Bfd,matfdcoloring,X,snes);CHKERRQ(ierr);
2350       ierr = MatFDColoringDestroy(&matfdcoloring);CHKERRQ(ierr);
2351 
2352       ierr = PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&vstdout);CHKERRQ(ierr);
2353       if (flag_draw || flag_contour) {
2354         ierr = PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),0,"Colored Jacobians",PETSC_DECIDE,PETSC_DECIDE,300,300,&vdraw);CHKERRQ(ierr);
2355         if (flag_contour) {ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);}
2356       } else vdraw = NULL;
2357       ierr = PetscViewerASCIIPrintf(vstdout,"Explicit preconditioning Jacobian\n");CHKERRQ(ierr);
2358       if (flag_display) {ierr = MatView(B,vstdout);CHKERRQ(ierr);}
2359       if (vdraw) {ierr = MatView(B,vdraw);CHKERRQ(ierr);}
2360       ierr = PetscViewerASCIIPrintf(vstdout,"Colored Finite difference Jacobian\n");CHKERRQ(ierr);
2361       if (flag_display) {ierr = MatView(Bfd,vstdout);CHKERRQ(ierr);}
2362       if (vdraw) {ierr = MatView(Bfd,vdraw);CHKERRQ(ierr);}
2363       ierr = MatAYPX(Bfd,-1.0,B,SAME_NONZERO_PATTERN);CHKERRQ(ierr);
2364       ierr = MatNorm(Bfd,NORM_1,&norm1);CHKERRQ(ierr);
2365       ierr = MatNorm(Bfd,NORM_FROBENIUS,&norm2);CHKERRQ(ierr);
2366       ierr = MatNorm(Bfd,NORM_MAX,&normmax);CHKERRQ(ierr);
2367       ierr = PetscViewerASCIIPrintf(vstdout,"User-provided matrix minus finite difference Jacobian, norm1=%g normFrob=%g normmax=%g\n",(double)norm1,(double)norm2,(double)normmax);CHKERRQ(ierr);
2368       if (flag_display) {ierr = MatView(Bfd,vstdout);CHKERRQ(ierr);}
2369       if (vdraw) {              /* Always use contour for the difference */
2370         ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);
2371         ierr = MatView(Bfd,vdraw);CHKERRQ(ierr);
2372         ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);
2373       }
2374       if (flag_contour) {ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);}
2375 
2376       if (flag_threshold) {
2377         PetscInt bs,rstart,rend,i;
2378         ierr = MatGetBlockSize(B,&bs);CHKERRQ(ierr);
2379         ierr = MatGetOwnershipRange(B,&rstart,&rend);CHKERRQ(ierr);
2380         for (i=rstart; i<rend; i++) {
2381           const PetscScalar *ba,*ca;
2382           const PetscInt    *bj,*cj;
2383           PetscInt          bn,cn,j,maxentrycol = -1,maxdiffcol = -1,maxrdiffcol = -1;
2384           PetscReal         maxentry = 0,maxdiff = 0,maxrdiff = 0;
2385           ierr = MatGetRow(B,i,&bn,&bj,&ba);CHKERRQ(ierr);
2386           ierr = MatGetRow(Bfd,i,&cn,&cj,&ca);CHKERRQ(ierr);
2387           if (bn != cn) SETERRQ(((PetscObject)A)->comm,PETSC_ERR_PLIB,"Unexpected different nonzero pattern in -snes_compare_coloring_threshold");
2388           for (j=0; j<bn; j++) {
2389             PetscReal rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol*PetscAbsScalar(ba[j]));
2390             if (PetscAbsScalar(ba[j]) > PetscAbs(maxentry)) {
2391               maxentrycol = bj[j];
2392               maxentry    = PetscRealPart(ba[j]);
2393             }
2394             if (PetscAbsScalar(ca[j]) > PetscAbs(maxdiff)) {
2395               maxdiffcol = bj[j];
2396               maxdiff    = PetscRealPart(ca[j]);
2397             }
2398             if (rdiff > maxrdiff) {
2399               maxrdiffcol = bj[j];
2400               maxrdiff    = rdiff;
2401             }
2402           }
2403           if (maxrdiff > 1) {
2404             ierr = PetscViewerASCIIPrintf(vstdout,"row %D (maxentry=%g at %D, maxdiff=%g at %D, maxrdiff=%g at %D):",i,(double)maxentry,maxentrycol,(double)maxdiff,maxdiffcol,(double)maxrdiff,maxrdiffcol);CHKERRQ(ierr);
2405             for (j=0; j<bn; j++) {
2406               PetscReal rdiff;
2407               rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol*PetscAbsScalar(ba[j]));
2408               if (rdiff > 1) {
2409                 ierr = PetscViewerASCIIPrintf(vstdout," (%D,%g:%g)",bj[j],(double)PetscRealPart(ba[j]),(double)PetscRealPart(ca[j]));CHKERRQ(ierr);
2410               }
2411             }
2412             ierr = PetscViewerASCIIPrintf(vstdout,"\n",i,maxentry,maxdiff,maxrdiff);CHKERRQ(ierr);
2413           }
2414           ierr = MatRestoreRow(B,i,&bn,&bj,&ba);CHKERRQ(ierr);
2415           ierr = MatRestoreRow(Bfd,i,&cn,&cj,&ca);CHKERRQ(ierr);
2416         }
2417       }
2418       ierr = PetscViewerDestroy(&vdraw);CHKERRQ(ierr);
2419       ierr = MatDestroy(&Bfd);CHKERRQ(ierr);
2420     }
2421   }
2422   PetscFunctionReturn(0);
2423 }
2424 
2425 /*MC
2426     SNESJacobianFunction - Function used to convey the nonlinear Jacobian of the function to be solved by SNES
2427 
2428      Synopsis:
2429      #include "petscsnes.h"
2430      PetscErrorCode SNESJacobianFunction(SNES snes,Vec x,Mat Amat,Mat Pmat,void *ctx);
2431 
2432 +  x - input vector
2433 .  Amat - the matrix that defines the (approximate) Jacobian
2434 .  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.
2435 -  ctx - [optional] user-defined Jacobian context
2436 
2437    Level: intermediate
2438 
2439 .seealso:   SNESSetFunction(), SNESGetFunction(), SNESSetJacobian(), SNESGetJacobian()
2440 M*/
2441 
2442 #undef __FUNCT__
2443 #define __FUNCT__ "SNESSetJacobian"
2444 /*@C
2445    SNESSetJacobian - Sets the function to compute Jacobian as well as the
2446    location to store the matrix.
2447 
2448    Logically Collective on SNES and Mat
2449 
2450    Input Parameters:
2451 +  snes - the SNES context
2452 .  Amat - the matrix that defines the (approximate) Jacobian
2453 .  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.
2454 .  J - Jacobian evaluation routine (if NULL then SNES retains any previously set value), see SNESJacobianFunction for details
2455 -  ctx - [optional] user-defined context for private data for the
2456          Jacobian evaluation routine (may be NULL) (if NULL then SNES retains any previously set value)
2457 
2458    Notes:
2459    If the Amat matrix and Pmat matrix are different you must call MatAssemblyBegin/End() on
2460    each matrix.
2461 
2462    If you know the operator Amat has a null space you can use MatSetNullSpace() and MatSetTransposeNullSpace() to supply the null
2463    space to Amat and the KSP solvers will automatically use that null space as needed during the solution process.
2464 
2465    If using SNESComputeJacobianDefaultColor() to assemble a Jacobian, the ctx argument
2466    must be a MatFDColoring.
2467 
2468    Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
2469    example is to use the "Picard linearization" which only differentiates through the highest order parts of each term.
2470 
2471    Level: beginner
2472 
2473 .keywords: SNES, nonlinear, set, Jacobian, matrix
2474 
2475 .seealso: KSPSetOperators(), SNESSetFunction(), MatMFFDComputeJacobian(), SNESComputeJacobianDefaultColor(), MatStructure, J,
2476           SNESSetPicard(), SNESJacobianFunction
2477 @*/
2478 PetscErrorCode  SNESSetJacobian(SNES snes,Mat Amat,Mat Pmat,PetscErrorCode (*J)(SNES,Vec,Mat,Mat,void*),void *ctx)
2479 {
2480   PetscErrorCode ierr;
2481   DM             dm;
2482 
2483   PetscFunctionBegin;
2484   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2485   if (Amat) PetscValidHeaderSpecific(Amat,MAT_CLASSID,2);
2486   if (Pmat) PetscValidHeaderSpecific(Pmat,MAT_CLASSID,3);
2487   if (Amat) PetscCheckSameComm(snes,1,Amat,2);
2488   if (Pmat) PetscCheckSameComm(snes,1,Pmat,3);
2489   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2490   ierr = DMSNESSetJacobian(dm,J,ctx);CHKERRQ(ierr);
2491   if (Amat) {
2492     ierr = PetscObjectReference((PetscObject)Amat);CHKERRQ(ierr);
2493     ierr = MatDestroy(&snes->jacobian);CHKERRQ(ierr);
2494 
2495     snes->jacobian = Amat;
2496   }
2497   if (Pmat) {
2498     ierr = PetscObjectReference((PetscObject)Pmat);CHKERRQ(ierr);
2499     ierr = MatDestroy(&snes->jacobian_pre);CHKERRQ(ierr);
2500 
2501     snes->jacobian_pre = Pmat;
2502   }
2503   PetscFunctionReturn(0);
2504 }
2505 
2506 #undef __FUNCT__
2507 #define __FUNCT__ "SNESGetJacobian"
2508 /*@C
2509    SNESGetJacobian - Returns the Jacobian matrix and optionally the user
2510    provided context for evaluating the Jacobian.
2511 
2512    Not Collective, but Mat object will be parallel if SNES object is
2513 
2514    Input Parameter:
2515 .  snes - the nonlinear solver context
2516 
2517    Output Parameters:
2518 +  Amat - location to stash (approximate) Jacobian matrix (or NULL)
2519 .  Pmat - location to stash matrix used to compute the preconditioner (or NULL)
2520 .  J - location to put Jacobian function (or NULL), see SNESJacobianFunction for details on its calling sequence
2521 -  ctx - location to stash Jacobian ctx (or NULL)
2522 
2523    Level: advanced
2524 
2525 .seealso: SNESSetJacobian(), SNESComputeJacobian(), SNESJacobianFunction, SNESGetFunction()
2526 @*/
2527 PetscErrorCode SNESGetJacobian(SNES snes,Mat *Amat,Mat *Pmat,PetscErrorCode (**J)(SNES,Vec,Mat,Mat,void*),void **ctx)
2528 {
2529   PetscErrorCode ierr;
2530   DM             dm;
2531   DMSNES         sdm;
2532 
2533   PetscFunctionBegin;
2534   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2535   if (Amat) *Amat = snes->jacobian;
2536   if (Pmat) *Pmat = snes->jacobian_pre;
2537   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2538   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2539   if (J) *J = sdm->ops->computejacobian;
2540   if (ctx) *ctx = sdm->jacobianctx;
2541   PetscFunctionReturn(0);
2542 }
2543 
2544 #undef __FUNCT__
2545 #define __FUNCT__ "SNESSetUp"
2546 /*@
2547    SNESSetUp - Sets up the internal data structures for the later use
2548    of a nonlinear solver.
2549 
2550    Collective on SNES
2551 
2552    Input Parameters:
2553 .  snes - the SNES context
2554 
2555    Notes:
2556    For basic use of the SNES solvers the user need not explicitly call
2557    SNESSetUp(), since these actions will automatically occur during
2558    the call to SNESSolve().  However, if one wishes to control this
2559    phase separately, SNESSetUp() should be called after SNESCreate()
2560    and optional routines of the form SNESSetXXX(), but before SNESSolve().
2561 
2562    Level: advanced
2563 
2564 .keywords: SNES, nonlinear, setup
2565 
2566 .seealso: SNESCreate(), SNESSolve(), SNESDestroy()
2567 @*/
2568 PetscErrorCode  SNESSetUp(SNES snes)
2569 {
2570   PetscErrorCode ierr;
2571   DM             dm;
2572   DMSNES         sdm;
2573   SNESLineSearch linesearch, pclinesearch;
2574   void           *lsprectx,*lspostctx;
2575   PetscErrorCode (*precheck)(SNESLineSearch,Vec,Vec,PetscBool*,void*);
2576   PetscErrorCode (*postcheck)(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);
2577   PetscErrorCode (*func)(SNES,Vec,Vec,void*);
2578   Vec            f,fpc;
2579   void           *funcctx;
2580   PetscErrorCode (*jac)(SNES,Vec,Mat,Mat,void*);
2581   void           *jacctx,*appctx;
2582   Mat            j,jpre;
2583 
2584   PetscFunctionBegin;
2585   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2586   if (snes->setupcalled) PetscFunctionReturn(0);
2587 
2588   if (!((PetscObject)snes)->type_name) {
2589     ierr = SNESSetType(snes,SNESNEWTONLS);CHKERRQ(ierr);
2590   }
2591 
2592   ierr = SNESGetFunction(snes,&snes->vec_func,NULL,NULL);CHKERRQ(ierr);
2593 
2594   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2595   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2596   if (!sdm->ops->computefunction) SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_ARG_WRONGSTATE,"Function never provided to SNES object");
2597   if (!sdm->ops->computejacobian) {
2598     ierr = DMSNESSetJacobian(dm,SNESComputeJacobianDefaultColor,NULL);CHKERRQ(ierr);
2599   }
2600   if (!snes->vec_func) {
2601     ierr = DMCreateGlobalVector(dm,&snes->vec_func);CHKERRQ(ierr);
2602   }
2603 
2604   if (!snes->ksp) {
2605     ierr = SNESGetKSP(snes, &snes->ksp);CHKERRQ(ierr);
2606   }
2607 
2608   if (!snes->linesearch) {
2609     ierr = SNESGetLineSearch(snes, &snes->linesearch);CHKERRQ(ierr);
2610   }
2611   ierr = SNESLineSearchSetFunction(snes->linesearch,SNESComputeFunction);CHKERRQ(ierr);
2612 
2613   if (snes->pc && (snes->pcside == PC_LEFT)) {
2614     snes->mf          = PETSC_TRUE;
2615     snes->mf_operator = PETSC_FALSE;
2616   }
2617 
2618   if (snes->pc) {
2619     /* copy the DM over */
2620     ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2621     ierr = SNESSetDM(snes->pc,dm);CHKERRQ(ierr);
2622 
2623     ierr = SNESGetFunction(snes,&f,&func,&funcctx);CHKERRQ(ierr);
2624     ierr = VecDuplicate(f,&fpc);CHKERRQ(ierr);
2625     ierr = SNESSetFunction(snes->pc,fpc,func,funcctx);CHKERRQ(ierr);
2626     ierr = SNESGetJacobian(snes,&j,&jpre,&jac,&jacctx);CHKERRQ(ierr);
2627     ierr = SNESSetJacobian(snes->pc,j,jpre,jac,jacctx);CHKERRQ(ierr);
2628     ierr = SNESGetApplicationContext(snes,&appctx);CHKERRQ(ierr);
2629     ierr = SNESSetApplicationContext(snes->pc,appctx);CHKERRQ(ierr);
2630     ierr = VecDestroy(&fpc);CHKERRQ(ierr);
2631 
2632     /* copy the function pointers over */
2633     ierr = PetscObjectCopyFortranFunctionPointers((PetscObject)snes,(PetscObject)snes->pc);CHKERRQ(ierr);
2634 
2635     /* default to 1 iteration */
2636     ierr = SNESSetTolerances(snes->pc,0.0,0.0,0.0,1,snes->pc->max_funcs);CHKERRQ(ierr);
2637     if (snes->pcside==PC_RIGHT) {
2638       ierr = SNESSetNormSchedule(snes->pc,SNES_NORM_FINAL_ONLY);CHKERRQ(ierr);
2639     } else {
2640       ierr = SNESSetNormSchedule(snes->pc,SNES_NORM_NONE);CHKERRQ(ierr);
2641     }
2642     ierr = SNESSetFromOptions(snes->pc);CHKERRQ(ierr);
2643 
2644     /* copy the line search context over */
2645     ierr = SNESGetLineSearch(snes,&linesearch);CHKERRQ(ierr);
2646     ierr = SNESGetLineSearch(snes->pc,&pclinesearch);CHKERRQ(ierr);
2647     ierr = SNESLineSearchGetPreCheck(linesearch,&precheck,&lsprectx);CHKERRQ(ierr);
2648     ierr = SNESLineSearchGetPostCheck(linesearch,&postcheck,&lspostctx);CHKERRQ(ierr);
2649     ierr = SNESLineSearchSetPreCheck(pclinesearch,precheck,lsprectx);CHKERRQ(ierr);
2650     ierr = SNESLineSearchSetPostCheck(pclinesearch,postcheck,lspostctx);CHKERRQ(ierr);
2651     ierr = PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)pclinesearch);CHKERRQ(ierr);
2652   }
2653   if (snes->mf) {
2654     ierr = SNESSetUpMatrixFree_Private(snes, snes->mf_operator, snes->mf_version);CHKERRQ(ierr);
2655   }
2656   if (snes->ops->usercompute && !snes->user) {
2657     ierr = (*snes->ops->usercompute)(snes,(void**)&snes->user);CHKERRQ(ierr);
2658   }
2659 
2660   snes->jac_iter = 0;
2661   snes->pre_iter = 0;
2662 
2663   if (snes->ops->setup) {
2664     ierr = (*snes->ops->setup)(snes);CHKERRQ(ierr);
2665   }
2666 
2667   if (snes->pc && (snes->pcside == PC_LEFT)) {
2668     if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
2669       ierr = SNESGetLineSearch(snes,&linesearch);CHKERRQ(ierr);
2670       ierr = SNESLineSearchSetFunction(linesearch,SNESComputeFunctionDefaultNPC);CHKERRQ(ierr);
2671     }
2672   }
2673 
2674   snes->setupcalled = PETSC_TRUE;
2675   PetscFunctionReturn(0);
2676 }
2677 
2678 #undef __FUNCT__
2679 #define __FUNCT__ "SNESReset"
2680 /*@
2681    SNESReset - Resets a SNES context to the snessetupcalled = 0 state and removes any allocated Vecs and Mats
2682 
2683    Collective on SNES
2684 
2685    Input Parameter:
2686 .  snes - iterative context obtained from SNESCreate()
2687 
2688    Level: intermediate
2689 
2690    Notes: Also calls the application context destroy routine set with SNESSetComputeApplicationContext()
2691 
2692 .keywords: SNES, destroy
2693 
2694 .seealso: SNESCreate(), SNESSetUp(), SNESSolve()
2695 @*/
2696 PetscErrorCode  SNESReset(SNES snes)
2697 {
2698   PetscErrorCode ierr;
2699 
2700   PetscFunctionBegin;
2701   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2702   if (snes->ops->userdestroy && snes->user) {
2703     ierr       = (*snes->ops->userdestroy)((void**)&snes->user);CHKERRQ(ierr);
2704     snes->user = NULL;
2705   }
2706   if (snes->pc) {
2707     ierr = SNESReset(snes->pc);CHKERRQ(ierr);
2708   }
2709 
2710   if (snes->ops->reset) {
2711     ierr = (*snes->ops->reset)(snes);CHKERRQ(ierr);
2712   }
2713   if (snes->ksp) {
2714     ierr = KSPReset(snes->ksp);CHKERRQ(ierr);
2715   }
2716 
2717   if (snes->linesearch) {
2718     ierr = SNESLineSearchReset(snes->linesearch);CHKERRQ(ierr);
2719   }
2720 
2721   ierr = VecDestroy(&snes->vec_rhs);CHKERRQ(ierr);
2722   ierr = VecDestroy(&snes->vec_sol);CHKERRQ(ierr);
2723   ierr = VecDestroy(&snes->vec_sol_update);CHKERRQ(ierr);
2724   ierr = VecDestroy(&snes->vec_func);CHKERRQ(ierr);
2725   ierr = MatDestroy(&snes->jacobian);CHKERRQ(ierr);
2726   ierr = MatDestroy(&snes->jacobian_pre);CHKERRQ(ierr);
2727   ierr = VecDestroyVecs(snes->nwork,&snes->work);CHKERRQ(ierr);
2728   ierr = VecDestroyVecs(snes->nvwork,&snes->vwork);CHKERRQ(ierr);
2729 
2730   snes->nwork       = snes->nvwork = 0;
2731   snes->setupcalled = PETSC_FALSE;
2732   PetscFunctionReturn(0);
2733 }
2734 
2735 #undef __FUNCT__
2736 #define __FUNCT__ "SNESDestroy"
2737 /*@
2738    SNESDestroy - Destroys the nonlinear solver context that was created
2739    with SNESCreate().
2740 
2741    Collective on SNES
2742 
2743    Input Parameter:
2744 .  snes - the SNES context
2745 
2746    Level: beginner
2747 
2748 .keywords: SNES, nonlinear, destroy
2749 
2750 .seealso: SNESCreate(), SNESSolve()
2751 @*/
2752 PetscErrorCode  SNESDestroy(SNES *snes)
2753 {
2754   PetscErrorCode ierr;
2755 
2756   PetscFunctionBegin;
2757   if (!*snes) PetscFunctionReturn(0);
2758   PetscValidHeaderSpecific((*snes),SNES_CLASSID,1);
2759   if (--((PetscObject)(*snes))->refct > 0) {*snes = 0; PetscFunctionReturn(0);}
2760 
2761   ierr = SNESReset((*snes));CHKERRQ(ierr);
2762   ierr = SNESDestroy(&(*snes)->pc);CHKERRQ(ierr);
2763 
2764   /* if memory was published with SAWs then destroy it */
2765   ierr = PetscObjectSAWsViewOff((PetscObject)*snes);CHKERRQ(ierr);
2766   if ((*snes)->ops->destroy) {ierr = (*((*snes))->ops->destroy)((*snes));CHKERRQ(ierr);}
2767 
2768   ierr = DMDestroy(&(*snes)->dm);CHKERRQ(ierr);
2769   ierr = KSPDestroy(&(*snes)->ksp);CHKERRQ(ierr);
2770   ierr = SNESLineSearchDestroy(&(*snes)->linesearch);CHKERRQ(ierr);
2771 
2772   ierr = PetscFree((*snes)->kspconvctx);CHKERRQ(ierr);
2773   if ((*snes)->ops->convergeddestroy) {
2774     ierr = (*(*snes)->ops->convergeddestroy)((*snes)->cnvP);CHKERRQ(ierr);
2775   }
2776   if ((*snes)->conv_malloc) {
2777     ierr = PetscFree((*snes)->conv_hist);CHKERRQ(ierr);
2778     ierr = PetscFree((*snes)->conv_hist_its);CHKERRQ(ierr);
2779   }
2780   ierr = SNESMonitorCancel((*snes));CHKERRQ(ierr);
2781   ierr = PetscHeaderDestroy(snes);CHKERRQ(ierr);
2782   PetscFunctionReturn(0);
2783 }
2784 
2785 /* ----------- Routines to set solver parameters ---------- */
2786 
2787 #undef __FUNCT__
2788 #define __FUNCT__ "SNESSetLagPreconditioner"
2789 /*@
2790    SNESSetLagPreconditioner - Determines when the preconditioner is rebuilt in the nonlinear solve.
2791 
2792    Logically Collective on SNES
2793 
2794    Input Parameters:
2795 +  snes - the SNES context
2796 -  lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2797          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that
2798 
2799    Options Database Keys:
2800 .    -snes_lag_preconditioner <lag>
2801 
2802    Notes:
2803    The default is 1
2804    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2805    If  -1 is used before the very first nonlinear solve the preconditioner is still built because there is no previous preconditioner to use
2806 
2807    Level: intermediate
2808 
2809 .keywords: SNES, nonlinear, set, convergence, tolerances
2810 
2811 .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian()
2812 
2813 @*/
2814 PetscErrorCode  SNESSetLagPreconditioner(SNES snes,PetscInt lag)
2815 {
2816   PetscFunctionBegin;
2817   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2818   if (lag < -2) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag must be -2, -1, 1 or greater");
2819   if (!lag) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag cannot be 0");
2820   PetscValidLogicalCollectiveInt(snes,lag,2);
2821   snes->lagpreconditioner = lag;
2822   PetscFunctionReturn(0);
2823 }
2824 
2825 #undef __FUNCT__
2826 #define __FUNCT__ "SNESSetGridSequence"
2827 /*@
2828    SNESSetGridSequence - sets the number of steps of grid sequencing that SNES does
2829 
2830    Logically Collective on SNES
2831 
2832    Input Parameters:
2833 +  snes - the SNES context
2834 -  steps - the number of refinements to do, defaults to 0
2835 
2836    Options Database Keys:
2837 .    -snes_grid_sequence <steps>
2838 
2839    Level: intermediate
2840 
2841    Notes:
2842    Use SNESGetSolution() to extract the fine grid solution after grid sequencing.
2843 
2844 .keywords: SNES, nonlinear, set, convergence, tolerances
2845 
2846 .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetGridSequence()
2847 
2848 @*/
2849 PetscErrorCode  SNESSetGridSequence(SNES snes,PetscInt steps)
2850 {
2851   PetscFunctionBegin;
2852   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2853   PetscValidLogicalCollectiveInt(snes,steps,2);
2854   snes->gridsequence = steps;
2855   PetscFunctionReturn(0);
2856 }
2857 
2858 #undef __FUNCT__
2859 #define __FUNCT__ "SNESGetGridSequence"
2860 /*@
2861    SNESGetGridSequence - gets the number of steps of grid sequencing that SNES does
2862 
2863    Logically Collective on SNES
2864 
2865    Input Parameter:
2866 .  snes - the SNES context
2867 
2868    Output Parameter:
2869 .  steps - the number of refinements to do, defaults to 0
2870 
2871    Options Database Keys:
2872 .    -snes_grid_sequence <steps>
2873 
2874    Level: intermediate
2875 
2876    Notes:
2877    Use SNESGetSolution() to extract the fine grid solution after grid sequencing.
2878 
2879 .keywords: SNES, nonlinear, set, convergence, tolerances
2880 
2881 .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESSetGridSequence()
2882 
2883 @*/
2884 PetscErrorCode  SNESGetGridSequence(SNES snes,PetscInt *steps)
2885 {
2886   PetscFunctionBegin;
2887   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2888   *steps = snes->gridsequence;
2889   PetscFunctionReturn(0);
2890 }
2891 
2892 #undef __FUNCT__
2893 #define __FUNCT__ "SNESGetLagPreconditioner"
2894 /*@
2895    SNESGetLagPreconditioner - Indicates how often the preconditioner is rebuilt
2896 
2897    Not Collective
2898 
2899    Input Parameter:
2900 .  snes - the SNES context
2901 
2902    Output Parameter:
2903 .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2904          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that
2905 
2906    Options Database Keys:
2907 .    -snes_lag_preconditioner <lag>
2908 
2909    Notes:
2910    The default is 1
2911    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2912 
2913    Level: intermediate
2914 
2915 .keywords: SNES, nonlinear, set, convergence, tolerances
2916 
2917 .seealso: SNESSetTrustRegionTolerance(), SNESSetLagPreconditioner()
2918 
2919 @*/
2920 PetscErrorCode  SNESGetLagPreconditioner(SNES snes,PetscInt *lag)
2921 {
2922   PetscFunctionBegin;
2923   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2924   *lag = snes->lagpreconditioner;
2925   PetscFunctionReturn(0);
2926 }
2927 
2928 #undef __FUNCT__
2929 #define __FUNCT__ "SNESSetLagJacobian"
2930 /*@
2931    SNESSetLagJacobian - Determines when the Jacobian is rebuilt in the nonlinear solve. See SNESSetLagPreconditioner() for determining how
2932      often the preconditioner is rebuilt.
2933 
2934    Logically Collective on SNES
2935 
2936    Input Parameters:
2937 +  snes - the SNES context
2938 -  lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2939          the Jacobian is built etc. -2 means rebuild at next chance but then never again
2940 
2941    Options Database Keys:
2942 .    -snes_lag_jacobian <lag>
2943 
2944    Notes:
2945    The default is 1
2946    The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2947    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
2948    at the next Newton step but never again (unless it is reset to another value)
2949 
2950    Level: intermediate
2951 
2952 .keywords: SNES, nonlinear, set, convergence, tolerances
2953 
2954 .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagPreconditioner(), SNESGetLagJacobian()
2955 
2956 @*/
2957 PetscErrorCode  SNESSetLagJacobian(SNES snes,PetscInt lag)
2958 {
2959   PetscFunctionBegin;
2960   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2961   if (lag < -2) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag must be -2, -1, 1 or greater");
2962   if (!lag) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag cannot be 0");
2963   PetscValidLogicalCollectiveInt(snes,lag,2);
2964   snes->lagjacobian = lag;
2965   PetscFunctionReturn(0);
2966 }
2967 
2968 #undef __FUNCT__
2969 #define __FUNCT__ "SNESGetLagJacobian"
2970 /*@
2971    SNESGetLagJacobian - Indicates how often the Jacobian is rebuilt. See SNESGetLagPreconditioner() to determine when the preconditioner is rebuilt
2972 
2973    Not Collective
2974 
2975    Input Parameter:
2976 .  snes - the SNES context
2977 
2978    Output Parameter:
2979 .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2980          the Jacobian is built etc.
2981 
2982    Options Database Keys:
2983 .    -snes_lag_jacobian <lag>
2984 
2985    Notes:
2986    The default is 1
2987    The jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2988 
2989    Level: intermediate
2990 
2991 .keywords: SNES, nonlinear, set, convergence, tolerances
2992 
2993 .seealso: SNESSetTrustRegionTolerance(), SNESSetLagJacobian(), SNESSetLagPreconditioner(), SNESGetLagPreconditioner()
2994 
2995 @*/
2996 PetscErrorCode  SNESGetLagJacobian(SNES snes,PetscInt *lag)
2997 {
2998   PetscFunctionBegin;
2999   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3000   *lag = snes->lagjacobian;
3001   PetscFunctionReturn(0);
3002 }
3003 
3004 #undef __FUNCT__
3005 #define __FUNCT__ "SNESSetLagJacobianPersists"
3006 /*@
3007    SNESSetLagJacobianPersists - Set whether or not the Jacobian lagging persists through multiple solves
3008 
3009    Logically collective on SNES
3010 
3011    Input Parameter:
3012 +  snes - the SNES context
3013 -   flg - jacobian lagging persists if true
3014 
3015    Options Database Keys:
3016 .    -snes_lag_jacobian_persists <flg>
3017 
3018    Notes: This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by
3019    several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several
3020    timesteps may present huge efficiency gains.
3021 
3022    Level: developer
3023 
3024 .keywords: SNES, nonlinear, lag
3025 
3026 .seealso: SNESSetLagPreconditionerPersists(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetNPC()
3027 
3028 @*/
3029 PetscErrorCode  SNESSetLagJacobianPersists(SNES snes,PetscBool flg)
3030 {
3031   PetscFunctionBegin;
3032   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3033   PetscValidLogicalCollectiveBool(snes,flg,2);
3034   snes->lagjac_persist = flg;
3035   PetscFunctionReturn(0);
3036 }
3037 
3038 #undef __FUNCT__
3039 #define __FUNCT__ "SNESSetLagPreconditionerPersists"
3040 /*@
3041    SNESSetLagPreconditionerPersists - Set whether or not the preconditioner lagging persists through multiple solves
3042 
3043    Logically Collective on SNES
3044 
3045    Input Parameter:
3046 +  snes - the SNES context
3047 -   flg - preconditioner lagging persists if true
3048 
3049    Options Database Keys:
3050 .    -snes_lag_jacobian_persists <flg>
3051 
3052    Notes: This is useful both for nonlinear preconditioning, where it's appropriate to have the preconditioner be stale
3053    by several solves, and for implicit time-stepping, where preconditioner lagging in the inner nonlinear solve over
3054    several timesteps may present huge efficiency gains.
3055 
3056    Level: developer
3057 
3058 .keywords: SNES, nonlinear, lag
3059 
3060 .seealso: SNESSetLagJacobianPersists(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetNPC()
3061 
3062 @*/
3063 PetscErrorCode  SNESSetLagPreconditionerPersists(SNES snes,PetscBool flg)
3064 {
3065   PetscFunctionBegin;
3066   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3067   PetscValidLogicalCollectiveBool(snes,flg,2);
3068   snes->lagpre_persist = flg;
3069   PetscFunctionReturn(0);
3070 }
3071 
3072 #undef __FUNCT__
3073 #define __FUNCT__ "SNESSetTolerances"
3074 /*@
3075    SNESSetTolerances - Sets various parameters used in convergence tests.
3076 
3077    Logically Collective on SNES
3078 
3079    Input Parameters:
3080 +  snes - the SNES context
3081 .  abstol - absolute convergence tolerance
3082 .  rtol - relative convergence tolerance
3083 .  stol -  convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
3084 .  maxit - maximum number of iterations
3085 -  maxf - maximum number of function evaluations
3086 
3087    Options Database Keys:
3088 +    -snes_atol <abstol> - Sets abstol
3089 .    -snes_rtol <rtol> - Sets rtol
3090 .    -snes_stol <stol> - Sets stol
3091 .    -snes_max_it <maxit> - Sets maxit
3092 -    -snes_max_funcs <maxf> - Sets maxf
3093 
3094    Notes:
3095    The default maximum number of iterations is 50.
3096    The default maximum number of function evaluations is 1000.
3097 
3098    Level: intermediate
3099 
3100 .keywords: SNES, nonlinear, set, convergence, tolerances
3101 
3102 .seealso: SNESSetTrustRegionTolerance()
3103 @*/
3104 PetscErrorCode  SNESSetTolerances(SNES snes,PetscReal abstol,PetscReal rtol,PetscReal stol,PetscInt maxit,PetscInt maxf)
3105 {
3106   PetscFunctionBegin;
3107   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3108   PetscValidLogicalCollectiveReal(snes,abstol,2);
3109   PetscValidLogicalCollectiveReal(snes,rtol,3);
3110   PetscValidLogicalCollectiveReal(snes,stol,4);
3111   PetscValidLogicalCollectiveInt(snes,maxit,5);
3112   PetscValidLogicalCollectiveInt(snes,maxf,6);
3113 
3114   if (abstol != PETSC_DEFAULT) {
3115     if (abstol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Absolute tolerance %g must be non-negative",(double)abstol);
3116     snes->abstol = abstol;
3117   }
3118   if (rtol != PETSC_DEFAULT) {
3119     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",(double)rtol);
3120     snes->rtol = rtol;
3121   }
3122   if (stol != PETSC_DEFAULT) {
3123     if (stol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Step tolerance %g must be non-negative",(double)stol);
3124     snes->stol = stol;
3125   }
3126   if (maxit != PETSC_DEFAULT) {
3127     if (maxit < 0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Maximum number of iterations %D must be non-negative",maxit);
3128     snes->max_its = maxit;
3129   }
3130   if (maxf != PETSC_DEFAULT) {
3131     if (maxf < 0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Maximum number of function evaluations %D must be non-negative",maxf);
3132     snes->max_funcs = maxf;
3133   }
3134   snes->tolerancesset = PETSC_TRUE;
3135   PetscFunctionReturn(0);
3136 }
3137 
3138 #undef __FUNCT__
3139 #define __FUNCT__ "SNESGetTolerances"
3140 /*@
3141    SNESGetTolerances - Gets various parameters used in convergence tests.
3142 
3143    Not Collective
3144 
3145    Input Parameters:
3146 +  snes - the SNES context
3147 .  atol - absolute convergence tolerance
3148 .  rtol - relative convergence tolerance
3149 .  stol -  convergence tolerance in terms of the norm
3150            of the change in the solution between steps
3151 .  maxit - maximum number of iterations
3152 -  maxf - maximum number of function evaluations
3153 
3154    Notes:
3155    The user can specify NULL for any parameter that is not needed.
3156 
3157    Level: intermediate
3158 
3159 .keywords: SNES, nonlinear, get, convergence, tolerances
3160 
3161 .seealso: SNESSetTolerances()
3162 @*/
3163 PetscErrorCode  SNESGetTolerances(SNES snes,PetscReal *atol,PetscReal *rtol,PetscReal *stol,PetscInt *maxit,PetscInt *maxf)
3164 {
3165   PetscFunctionBegin;
3166   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3167   if (atol)  *atol  = snes->abstol;
3168   if (rtol)  *rtol  = snes->rtol;
3169   if (stol)  *stol  = snes->stol;
3170   if (maxit) *maxit = snes->max_its;
3171   if (maxf)  *maxf  = snes->max_funcs;
3172   PetscFunctionReturn(0);
3173 }
3174 
3175 #undef __FUNCT__
3176 #define __FUNCT__ "SNESSetTrustRegionTolerance"
3177 /*@
3178    SNESSetTrustRegionTolerance - Sets the trust region parameter tolerance.
3179 
3180    Logically Collective on SNES
3181 
3182    Input Parameters:
3183 +  snes - the SNES context
3184 -  tol - tolerance
3185 
3186    Options Database Key:
3187 .  -snes_trtol <tol> - Sets tol
3188 
3189    Level: intermediate
3190 
3191 .keywords: SNES, nonlinear, set, trust region, tolerance
3192 
3193 .seealso: SNESSetTolerances()
3194 @*/
3195 PetscErrorCode  SNESSetTrustRegionTolerance(SNES snes,PetscReal tol)
3196 {
3197   PetscFunctionBegin;
3198   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3199   PetscValidLogicalCollectiveReal(snes,tol,2);
3200   snes->deltatol = tol;
3201   PetscFunctionReturn(0);
3202 }
3203 
3204 /*
3205    Duplicate the lg monitors for SNES from KSP; for some reason with
3206    dynamic libraries things don't work under Sun4 if we just use
3207    macros instead of functions
3208 */
3209 #undef __FUNCT__
3210 #define __FUNCT__ "SNESMonitorLGResidualNorm"
3211 PetscErrorCode  SNESMonitorLGResidualNorm(SNES snes,PetscInt it,PetscReal norm,void *ctx)
3212 {
3213   PetscErrorCode ierr;
3214 
3215   PetscFunctionBegin;
3216   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3217   ierr = KSPMonitorLGResidualNorm((KSP)snes,it,norm,ctx);CHKERRQ(ierr);
3218   PetscFunctionReturn(0);
3219 }
3220 
3221 #undef __FUNCT__
3222 #define __FUNCT__ "SNESMonitorLGCreate"
3223 PetscErrorCode  SNESMonitorLGCreate(MPI_Comm comm,const char host[],const char label[],int x,int y,int m,int n,PetscDrawLG *lgctx)
3224 {
3225   PetscErrorCode ierr;
3226 
3227   PetscFunctionBegin;
3228   ierr = KSPMonitorLGResidualNormCreate(comm,host,label,x,y,m,n,lgctx);CHKERRQ(ierr);
3229   PetscFunctionReturn(0);
3230 }
3231 
3232 extern PetscErrorCode  SNESMonitorRange_Private(SNES,PetscInt,PetscReal*);
3233 #undef __FUNCT__
3234 #define __FUNCT__ "SNESMonitorLGRange"
3235 PetscErrorCode  SNESMonitorLGRange(SNES snes,PetscInt n,PetscReal rnorm,void *monctx)
3236 {
3237   PetscDrawLG      lg;
3238   PetscErrorCode   ierr;
3239   PetscReal        x,y,per;
3240   PetscViewer      v = (PetscViewer)monctx;
3241   static PetscReal prev; /* should be in the context */
3242   PetscDraw        draw;
3243 
3244   PetscFunctionBegin;
3245   PetscValidHeaderSpecific(v,PETSC_VIEWER_CLASSID,4);
3246   ierr = PetscViewerDrawGetDrawLG(v,0,&lg);CHKERRQ(ierr);
3247   if (!n) {ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3248   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3249   ierr = PetscDrawSetTitle(draw,"Residual norm");CHKERRQ(ierr);
3250   x    = (PetscReal)n;
3251   if (rnorm > 0.0) y = PetscLog10Real(rnorm);
3252   else y = -15.0;
3253   ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3254   if (n < 20 || !(n % 5)) {
3255     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3256   }
3257 
3258   ierr = PetscViewerDrawGetDrawLG(v,1,&lg);CHKERRQ(ierr);
3259   if (!n) {ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3260   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3261   ierr = PetscDrawSetTitle(draw,"% elemts > .2*max elemt");CHKERRQ(ierr);
3262   ierr =  SNESMonitorRange_Private(snes,n,&per);CHKERRQ(ierr);
3263   x    = (PetscReal)n;
3264   y    = 100.0*per;
3265   ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3266   if (n < 20 || !(n % 5)) {
3267     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3268   }
3269 
3270   ierr = PetscViewerDrawGetDrawLG(v,2,&lg);CHKERRQ(ierr);
3271   if (!n) {prev = rnorm;ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3272   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3273   ierr = PetscDrawSetTitle(draw,"(norm -oldnorm)/oldnorm");CHKERRQ(ierr);
3274   x    = (PetscReal)n;
3275   y    = (prev - rnorm)/prev;
3276   ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3277   if (n < 20 || !(n % 5)) {
3278     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3279   }
3280 
3281   ierr = PetscViewerDrawGetDrawLG(v,3,&lg);CHKERRQ(ierr);
3282   if (!n) {ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3283   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3284   ierr = PetscDrawSetTitle(draw,"(norm -oldnorm)/oldnorm*(% > .2 max)");CHKERRQ(ierr);
3285   x    = (PetscReal)n;
3286   y    = (prev - rnorm)/(prev*per);
3287   if (n > 2) { /*skip initial crazy value */
3288     ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3289   }
3290   if (n < 20 || !(n % 5)) {
3291     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3292   }
3293   prev = rnorm;
3294   PetscFunctionReturn(0);
3295 }
3296 
3297 #undef __FUNCT__
3298 #define __FUNCT__ "SNESMonitor"
3299 /*@
3300    SNESMonitor - runs the user provided monitor routines, if they exist
3301 
3302    Collective on SNES
3303 
3304    Input Parameters:
3305 +  snes - nonlinear solver context obtained from SNESCreate()
3306 .  iter - iteration number
3307 -  rnorm - relative norm of the residual
3308 
3309    Notes:
3310    This routine is called by the SNES implementations.
3311    It does not typically need to be called by the user.
3312 
3313    Level: developer
3314 
3315 .seealso: SNESMonitorSet()
3316 @*/
3317 PetscErrorCode  SNESMonitor(SNES snes,PetscInt iter,PetscReal rnorm)
3318 {
3319   PetscErrorCode ierr;
3320   PetscInt       i,n = snes->numbermonitors;
3321 
3322   PetscFunctionBegin;
3323   ierr = VecLockPush(snes->vec_sol);CHKERRQ(ierr);
3324   for (i=0; i<n; i++) {
3325     ierr = (*snes->monitor[i])(snes,iter,rnorm,snes->monitorcontext[i]);CHKERRQ(ierr);
3326   }
3327   ierr = VecLockPop(snes->vec_sol);CHKERRQ(ierr);
3328   PetscFunctionReturn(0);
3329 }
3330 
3331 /* ------------ Routines to set performance monitoring options ----------- */
3332 
3333 /*MC
3334     SNESMonitorFunction - functional form passed to SNESMonitorSet() to monitor convergence of nonlinear solver
3335 
3336      Synopsis:
3337      #include <petscsnes.h>
3338 $    PetscErrorCode SNESMonitorFunction(SNES snes,PetscInt its, PetscReal norm,void *mctx)
3339 
3340 +    snes - the SNES context
3341 .    its - iteration number
3342 .    norm - 2-norm function value (may be estimated)
3343 -    mctx - [optional] monitoring context
3344 
3345    Level: advanced
3346 
3347 .seealso:   SNESMonitorSet(), SNESMonitorGet()
3348 M*/
3349 
3350 #undef __FUNCT__
3351 #define __FUNCT__ "SNESMonitorSet"
3352 /*@C
3353    SNESMonitorSet - Sets an ADDITIONAL function that is to be used at every
3354    iteration of the nonlinear solver to display the iteration's
3355    progress.
3356 
3357    Logically Collective on SNES
3358 
3359    Input Parameters:
3360 +  snes - the SNES context
3361 .  f - the monitor function, see SNESMonitorFunction for the calling sequence
3362 .  mctx - [optional] user-defined context for private data for the
3363           monitor routine (use NULL if no context is desired)
3364 -  monitordestroy - [optional] routine that frees monitor context
3365           (may be NULL)
3366 
3367    Options Database Keys:
3368 +    -snes_monitor        - sets SNESMonitorDefault()
3369 .    -snes_monitor_lg_residualnorm    - sets line graph monitor,
3370                             uses SNESMonitorLGCreate()
3371 -    -snes_monitor_cancel - cancels all monitors that have
3372                             been hardwired into a code by
3373                             calls to SNESMonitorSet(), but
3374                             does not cancel those set via
3375                             the options database.
3376 
3377    Notes:
3378    Several different monitoring routines may be set by calling
3379    SNESMonitorSet() multiple times; all will be called in the
3380    order in which they were set.
3381 
3382    Fortran notes: Only a single monitor function can be set for each SNES object
3383 
3384    Level: intermediate
3385 
3386 .keywords: SNES, nonlinear, set, monitor
3387 
3388 .seealso: SNESMonitorDefault(), SNESMonitorCancel(), SNESMonitorFunction
3389 @*/
3390 PetscErrorCode  SNESMonitorSet(SNES snes,PetscErrorCode (*f)(SNES,PetscInt,PetscReal,void*),void *mctx,PetscErrorCode (*monitordestroy)(void**))
3391 {
3392   PetscInt       i;
3393   PetscErrorCode ierr;
3394 
3395   PetscFunctionBegin;
3396   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3397   if (snes->numbermonitors >= MAXSNESMONITORS) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Too many monitors set");
3398   for (i=0; i<snes->numbermonitors;i++) {
3399     if (f == snes->monitor[i] && monitordestroy == snes->monitordestroy[i] && mctx == snes->monitorcontext[i]) {
3400       if (monitordestroy) {
3401         ierr = (*monitordestroy)(&mctx);CHKERRQ(ierr);
3402       }
3403       PetscFunctionReturn(0);
3404     }
3405   }
3406   snes->monitor[snes->numbermonitors]          = f;
3407   snes->monitordestroy[snes->numbermonitors]   = monitordestroy;
3408   snes->monitorcontext[snes->numbermonitors++] = (void*)mctx;
3409   PetscFunctionReturn(0);
3410 }
3411 
3412 #undef __FUNCT__
3413 #define __FUNCT__ "SNESMonitorCancel"
3414 /*@
3415    SNESMonitorCancel - Clears all the monitor functions for a SNES object.
3416 
3417    Logically Collective on SNES
3418 
3419    Input Parameters:
3420 .  snes - the SNES context
3421 
3422    Options Database Key:
3423 .  -snes_monitor_cancel - cancels all monitors that have been hardwired
3424     into a code by calls to SNESMonitorSet(), but does not cancel those
3425     set via the options database
3426 
3427    Notes:
3428    There is no way to clear one specific monitor from a SNES object.
3429 
3430    Level: intermediate
3431 
3432 .keywords: SNES, nonlinear, set, monitor
3433 
3434 .seealso: SNESMonitorDefault(), SNESMonitorSet()
3435 @*/
3436 PetscErrorCode  SNESMonitorCancel(SNES snes)
3437 {
3438   PetscErrorCode ierr;
3439   PetscInt       i;
3440 
3441   PetscFunctionBegin;
3442   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3443   for (i=0; i<snes->numbermonitors; i++) {
3444     if (snes->monitordestroy[i]) {
3445       ierr = (*snes->monitordestroy[i])(&snes->monitorcontext[i]);CHKERRQ(ierr);
3446     }
3447   }
3448   snes->numbermonitors = 0;
3449   PetscFunctionReturn(0);
3450 }
3451 
3452 /*MC
3453     SNESConvergenceTestFunction - functional form used for testing of convergence of nonlinear solver
3454 
3455      Synopsis:
3456      #include <petscsnes.h>
3457 $     PetscErrorCode SNESConvergenceTest(SNES snes,PetscInt it,PetscReal xnorm,PetscReal gnorm,PetscReal f,SNESConvergedReason *reason,void *cctx)
3458 
3459 +    snes - the SNES context
3460 .    it - current iteration (0 is the first and is before any Newton step)
3461 .    cctx - [optional] convergence context
3462 .    reason - reason for convergence/divergence
3463 .    xnorm - 2-norm of current iterate
3464 .    gnorm - 2-norm of current step
3465 -    f - 2-norm of function
3466 
3467    Level: intermediate
3468 
3469 .seealso:   SNESSetConvergenceTest(), SNESGetConvergenceTest()
3470 M*/
3471 
3472 #undef __FUNCT__
3473 #define __FUNCT__ "SNESSetConvergenceTest"
3474 /*@C
3475    SNESSetConvergenceTest - Sets the function that is to be used
3476    to test for convergence of the nonlinear iterative solution.
3477 
3478    Logically Collective on SNES
3479 
3480    Input Parameters:
3481 +  snes - the SNES context
3482 .  SNESConvergenceTestFunction - routine to test for convergence
3483 .  cctx - [optional] context for private data for the convergence routine  (may be NULL)
3484 -  destroy - [optional] destructor for the context (may be NULL; NULL_FUNCTION in Fortran)
3485 
3486    Level: advanced
3487 
3488 .keywords: SNES, nonlinear, set, convergence, test
3489 
3490 .seealso: SNESConvergedDefault(), SNESConvergedSkip(), SNESConvergenceTestFunction
3491 @*/
3492 PetscErrorCode  SNESSetConvergenceTest(SNES snes,PetscErrorCode (*SNESConvergenceTestFunction)(SNES,PetscInt,PetscReal,PetscReal,PetscReal,SNESConvergedReason*,void*),void *cctx,PetscErrorCode (*destroy)(void*))
3493 {
3494   PetscErrorCode ierr;
3495 
3496   PetscFunctionBegin;
3497   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3498   if (!SNESConvergenceTestFunction) SNESConvergenceTestFunction = SNESConvergedSkip;
3499   if (snes->ops->convergeddestroy) {
3500     ierr = (*snes->ops->convergeddestroy)(snes->cnvP);CHKERRQ(ierr);
3501   }
3502   snes->ops->converged        = SNESConvergenceTestFunction;
3503   snes->ops->convergeddestroy = destroy;
3504   snes->cnvP                  = cctx;
3505   PetscFunctionReturn(0);
3506 }
3507 
3508 #undef __FUNCT__
3509 #define __FUNCT__ "SNESGetConvergedReason"
3510 /*@
3511    SNESGetConvergedReason - Gets the reason the SNES iteration was stopped.
3512 
3513    Not Collective
3514 
3515    Input Parameter:
3516 .  snes - the SNES context
3517 
3518    Output Parameter:
3519 .  reason - negative value indicates diverged, positive value converged, see SNESConvergedReason or the
3520             manual pages for the individual convergence tests for complete lists
3521 
3522    Level: intermediate
3523 
3524    Notes: Can only be called after the call the SNESSolve() is complete.
3525 
3526 .keywords: SNES, nonlinear, set, convergence, test
3527 
3528 .seealso: SNESSetConvergenceTest(), SNESConvergedReason
3529 @*/
3530 PetscErrorCode  SNESGetConvergedReason(SNES snes,SNESConvergedReason *reason)
3531 {
3532   PetscFunctionBegin;
3533   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3534   PetscValidPointer(reason,2);
3535   *reason = snes->reason;
3536   PetscFunctionReturn(0);
3537 }
3538 
3539 #undef __FUNCT__
3540 #define __FUNCT__ "SNESSetConvergenceHistory"
3541 /*@
3542    SNESSetConvergenceHistory - Sets the array used to hold the convergence history.
3543 
3544    Logically Collective on SNES
3545 
3546    Input Parameters:
3547 +  snes - iterative context obtained from SNESCreate()
3548 .  a   - array to hold history, this array will contain the function norms computed at each step
3549 .  its - integer array holds the number of linear iterations for each solve.
3550 .  na  - size of a and its
3551 -  reset - PETSC_TRUE indicates each new nonlinear solve resets the history counter to zero,
3552            else it continues storing new values for new nonlinear solves after the old ones
3553 
3554    Notes:
3555    If 'a' and 'its' are NULL then space is allocated for the history. If 'na' PETSC_DECIDE or PETSC_DEFAULT then a
3556    default array of length 10000 is allocated.
3557 
3558    This routine is useful, e.g., when running a code for purposes
3559    of accurate performance monitoring, when no I/O should be done
3560    during the section of code that is being timed.
3561 
3562    Level: intermediate
3563 
3564 .keywords: SNES, set, convergence, history
3565 
3566 .seealso: SNESGetConvergenceHistory()
3567 
3568 @*/
3569 PetscErrorCode  SNESSetConvergenceHistory(SNES snes,PetscReal a[],PetscInt its[],PetscInt na,PetscBool reset)
3570 {
3571   PetscErrorCode ierr;
3572 
3573   PetscFunctionBegin;
3574   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3575   if (a) PetscValidScalarPointer(a,2);
3576   if (its) PetscValidIntPointer(its,3);
3577   if (!a) {
3578     if (na == PETSC_DECIDE || na == PETSC_DEFAULT) na = 1000;
3579     ierr = PetscCalloc1(na,&a);CHKERRQ(ierr);
3580     ierr = PetscCalloc1(na,&its);CHKERRQ(ierr);
3581 
3582     snes->conv_malloc = PETSC_TRUE;
3583   }
3584   snes->conv_hist       = a;
3585   snes->conv_hist_its   = its;
3586   snes->conv_hist_max   = na;
3587   snes->conv_hist_len   = 0;
3588   snes->conv_hist_reset = reset;
3589   PetscFunctionReturn(0);
3590 }
3591 
3592 #if defined(PETSC_HAVE_MATLAB_ENGINE)
3593 #include <engine.h>   /* MATLAB include file */
3594 #include <mex.h>      /* MATLAB include file */
3595 
3596 #undef __FUNCT__
3597 #define __FUNCT__ "SNESGetConvergenceHistoryMatlab"
3598 PETSC_EXTERN mxArray *SNESGetConvergenceHistoryMatlab(SNES snes)
3599 {
3600   mxArray   *mat;
3601   PetscInt  i;
3602   PetscReal *ar;
3603 
3604   PetscFunctionBegin;
3605   mat = mxCreateDoubleMatrix(snes->conv_hist_len,1,mxREAL);
3606   ar  = (PetscReal*) mxGetData(mat);
3607   for (i=0; i<snes->conv_hist_len; i++) ar[i] = snes->conv_hist[i];
3608   PetscFunctionReturn(mat);
3609 }
3610 #endif
3611 
3612 #undef __FUNCT__
3613 #define __FUNCT__ "SNESGetConvergenceHistory"
3614 /*@C
3615    SNESGetConvergenceHistory - Gets the array used to hold the convergence history.
3616 
3617    Not Collective
3618 
3619    Input Parameter:
3620 .  snes - iterative context obtained from SNESCreate()
3621 
3622    Output Parameters:
3623 .  a   - array to hold history
3624 .  its - integer array holds the number of linear iterations (or
3625          negative if not converged) for each solve.
3626 -  na  - size of a and its
3627 
3628    Notes:
3629     The calling sequence for this routine in Fortran is
3630 $   call SNESGetConvergenceHistory(SNES snes, integer na, integer ierr)
3631 
3632    This routine is useful, e.g., when running a code for purposes
3633    of accurate performance monitoring, when no I/O should be done
3634    during the section of code that is being timed.
3635 
3636    Level: intermediate
3637 
3638 .keywords: SNES, get, convergence, history
3639 
3640 .seealso: SNESSetConvergencHistory()
3641 
3642 @*/
3643 PetscErrorCode  SNESGetConvergenceHistory(SNES snes,PetscReal *a[],PetscInt *its[],PetscInt *na)
3644 {
3645   PetscFunctionBegin;
3646   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3647   if (a)   *a   = snes->conv_hist;
3648   if (its) *its = snes->conv_hist_its;
3649   if (na)  *na  = snes->conv_hist_len;
3650   PetscFunctionReturn(0);
3651 }
3652 
3653 #undef __FUNCT__
3654 #define __FUNCT__ "SNESSetUpdate"
3655 /*@C
3656   SNESSetUpdate - Sets the general-purpose update function called
3657   at the beginning of every iteration of the nonlinear solve. Specifically
3658   it is called just before the Jacobian is "evaluated".
3659 
3660   Logically Collective on SNES
3661 
3662   Input Parameters:
3663 . snes - The nonlinear solver context
3664 . func - The function
3665 
3666   Calling sequence of func:
3667 . func (SNES snes, PetscInt step);
3668 
3669 . step - The current step of the iteration
3670 
3671   Level: advanced
3672 
3673   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()
3674         This is not used by most users.
3675 
3676 .keywords: SNES, update
3677 
3678 .seealso SNESSetJacobian(), SNESSolve()
3679 @*/
3680 PetscErrorCode  SNESSetUpdate(SNES snes, PetscErrorCode (*func)(SNES, PetscInt))
3681 {
3682   PetscFunctionBegin;
3683   PetscValidHeaderSpecific(snes, SNES_CLASSID,1);
3684   snes->ops->update = func;
3685   PetscFunctionReturn(0);
3686 }
3687 
3688 #undef __FUNCT__
3689 #define __FUNCT__ "SNESScaleStep_Private"
3690 /*
3691    SNESScaleStep_Private - Scales a step so that its length is less than the
3692    positive parameter delta.
3693 
3694     Input Parameters:
3695 +   snes - the SNES context
3696 .   y - approximate solution of linear system
3697 .   fnorm - 2-norm of current function
3698 -   delta - trust region size
3699 
3700     Output Parameters:
3701 +   gpnorm - predicted function norm at the new point, assuming local
3702     linearization.  The value is zero if the step lies within the trust
3703     region, and exceeds zero otherwise.
3704 -   ynorm - 2-norm of the step
3705 
3706     Note:
3707     For non-trust region methods such as SNESNEWTONLS, the parameter delta
3708     is set to be the maximum allowable step size.
3709 
3710 .keywords: SNES, nonlinear, scale, step
3711 */
3712 PetscErrorCode SNESScaleStep_Private(SNES snes,Vec y,PetscReal *fnorm,PetscReal *delta,PetscReal *gpnorm,PetscReal *ynorm)
3713 {
3714   PetscReal      nrm;
3715   PetscScalar    cnorm;
3716   PetscErrorCode ierr;
3717 
3718   PetscFunctionBegin;
3719   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3720   PetscValidHeaderSpecific(y,VEC_CLASSID,2);
3721   PetscCheckSameComm(snes,1,y,2);
3722 
3723   ierr = VecNorm(y,NORM_2,&nrm);CHKERRQ(ierr);
3724   if (nrm > *delta) {
3725     nrm     = *delta/nrm;
3726     *gpnorm = (1.0 - nrm)*(*fnorm);
3727     cnorm   = nrm;
3728     ierr    = VecScale(y,cnorm);CHKERRQ(ierr);
3729     *ynorm  = *delta;
3730   } else {
3731     *gpnorm = 0.0;
3732     *ynorm  = nrm;
3733   }
3734   PetscFunctionReturn(0);
3735 }
3736 
3737 #undef __FUNCT__
3738 #define __FUNCT__ "SNESReasonView"
3739 /*@
3740    SNESReasonView - Displays the reason a SNES solve converged or diverged to a viewer
3741 
3742    Collective on SNES
3743 
3744    Parameter:
3745 +  snes - iterative context obtained from SNESCreate()
3746 -  viewer - the viewer to display the reason
3747 
3748 
3749    Options Database Keys:
3750 .  -snes_converged_reason - print reason for converged or diverged, also prints number of iterations
3751 
3752    Level: beginner
3753 
3754 .keywords: SNES, solve, linear system
3755 
3756 .seealso: SNESCreate(), SNESSetUp(), SNESDestroy(), SNESSetTolerances(), SNESConvergedDefault()
3757 
3758 @*/
3759 PetscErrorCode  SNESReasonView(SNES snes,PetscViewer viewer)
3760 {
3761   PetscErrorCode ierr;
3762   PetscBool      isAscii;
3763 
3764   PetscFunctionBegin;
3765   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&isAscii);CHKERRQ(ierr);
3766   if (isAscii) {
3767     ierr = PetscViewerASCIIAddTab(viewer,((PetscObject)snes)->tablevel);CHKERRQ(ierr);
3768     if (snes->reason > 0) {
3769       if (((PetscObject) snes)->prefix) {
3770         ierr = PetscViewerASCIIPrintf(viewer,"Nonlinear %s solve converged due to %s iterations %D\n",((PetscObject) snes)->prefix,SNESConvergedReasons[snes->reason],snes->iter);CHKERRQ(ierr);
3771       } else {
3772         ierr = PetscViewerASCIIPrintf(viewer,"Nonlinear solve converged due to %s iterations %D\n",SNESConvergedReasons[snes->reason],snes->iter);CHKERRQ(ierr);
3773       }
3774     } else {
3775       if (((PetscObject) snes)->prefix) {
3776         ierr = PetscViewerASCIIPrintf(viewer,"Nonlinear %s solve did not converge due to %s iterations %D\n",((PetscObject) snes)->prefix,SNESConvergedReasons[snes->reason],snes->iter);CHKERRQ(ierr);
3777       } else {
3778         ierr = PetscViewerASCIIPrintf(viewer,"Nonlinear solve did not converge due to %s iterations %D\n",SNESConvergedReasons[snes->reason],snes->iter);CHKERRQ(ierr);
3779       }
3780     }
3781     ierr = PetscViewerASCIISubtractTab(viewer,((PetscObject)snes)->tablevel);CHKERRQ(ierr);
3782   }
3783   PetscFunctionReturn(0);
3784 }
3785 
3786 #undef __FUNCT__
3787 #define __FUNCT__ "SNESReasonViewFromOptions"
3788 /*@C
3789   SNESReasonViewFromOptions - Processes command line options to determine if/how a SNESReason is to be viewed.
3790 
3791   Collective on SNES
3792 
3793   Input Parameters:
3794 . snes   - the SNES object
3795 
3796   Level: intermediate
3797 
3798 @*/
3799 PetscErrorCode SNESReasonViewFromOptions(SNES snes)
3800 {
3801   PetscErrorCode    ierr;
3802   PetscViewer       viewer;
3803   PetscBool         flg;
3804   static PetscBool  incall = PETSC_FALSE;
3805   PetscViewerFormat format;
3806 
3807   PetscFunctionBegin;
3808   if (incall) PetscFunctionReturn(0);
3809   incall = PETSC_TRUE;
3810   ierr   = PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->prefix,"-snes_converged_reason",&viewer,&format,&flg);CHKERRQ(ierr);
3811   if (flg) {
3812     ierr = PetscViewerPushFormat(viewer,format);CHKERRQ(ierr);
3813     ierr = SNESReasonView(snes,viewer);CHKERRQ(ierr);
3814     ierr = PetscViewerPopFormat(viewer);CHKERRQ(ierr);
3815     ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
3816   }
3817   incall = PETSC_FALSE;
3818   PetscFunctionReturn(0);
3819 }
3820 
3821 #undef __FUNCT__
3822 #define __FUNCT__ "SNESSolve"
3823 /*@C
3824    SNESSolve - Solves a nonlinear system F(x) = b.
3825    Call SNESSolve() after calling SNESCreate() and optional routines of the form SNESSetXXX().
3826 
3827    Collective on SNES
3828 
3829    Input Parameters:
3830 +  snes - the SNES context
3831 .  b - the constant part of the equation F(x) = b, or NULL to use zero.
3832 -  x - the solution vector.
3833 
3834    Notes:
3835    The user should initialize the vector,x, with the initial guess
3836    for the nonlinear solve prior to calling SNESSolve.  In particular,
3837    to employ an initial guess of zero, the user should explicitly set
3838    this vector to zero by calling VecSet().
3839 
3840    Level: beginner
3841 
3842 .keywords: SNES, nonlinear, solve
3843 
3844 .seealso: SNESCreate(), SNESDestroy(), SNESSetFunction(), SNESSetJacobian(), SNESSetGridSequence(), SNESGetSolution()
3845 @*/
3846 PetscErrorCode  SNESSolve(SNES snes,Vec b,Vec x)
3847 {
3848   PetscErrorCode    ierr;
3849   PetscBool         flg;
3850   PetscInt          grid;
3851   Vec               xcreated = NULL;
3852   DM                dm;
3853 
3854   PetscFunctionBegin;
3855   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3856   if (x) PetscValidHeaderSpecific(x,VEC_CLASSID,3);
3857   if (x) PetscCheckSameComm(snes,1,x,3);
3858   if (b) PetscValidHeaderSpecific(b,VEC_CLASSID,2);
3859   if (b) PetscCheckSameComm(snes,1,b,2);
3860 
3861   if (!x) {
3862     ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
3863     ierr = DMCreateGlobalVector(dm,&xcreated);CHKERRQ(ierr);
3864     x    = xcreated;
3865   }
3866   ierr = SNESViewFromOptions(snes,NULL,"-snes_view_pre");CHKERRQ(ierr);
3867 
3868   for (grid=0; grid<snes->gridsequence; grid++) {ierr = PetscViewerASCIIPushTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)));CHKERRQ(ierr);}
3869   for (grid=0; grid<snes->gridsequence+1; grid++) {
3870 
3871     /* set solution vector */
3872     if (!grid) {ierr = PetscObjectReference((PetscObject)x);CHKERRQ(ierr);}
3873     ierr          = VecDestroy(&snes->vec_sol);CHKERRQ(ierr);
3874     snes->vec_sol = x;
3875     ierr          = SNESGetDM(snes,&dm);CHKERRQ(ierr);
3876 
3877     /* set affine vector if provided */
3878     if (b) { ierr = PetscObjectReference((PetscObject)b);CHKERRQ(ierr); }
3879     ierr          = VecDestroy(&snes->vec_rhs);CHKERRQ(ierr);
3880     snes->vec_rhs = b;
3881 
3882     if (snes->vec_func == snes->vec_sol) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_IDN,"Solution vector cannot be function vector");
3883     if (snes->vec_rhs  == snes->vec_sol) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_IDN,"Solution vector cannot be right hand side vector");
3884     if (!snes->vec_sol_update /* && snes->vec_sol */) {
3885       ierr = VecDuplicate(snes->vec_sol,&snes->vec_sol_update);CHKERRQ(ierr);
3886       ierr = PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->vec_sol_update);CHKERRQ(ierr);
3887     }
3888     ierr = DMShellSetGlobalVector(dm,snes->vec_sol);CHKERRQ(ierr);
3889     ierr = SNESSetUp(snes);CHKERRQ(ierr);
3890 
3891     if (!grid) {
3892       if (snes->ops->computeinitialguess) {
3893         ierr = (*snes->ops->computeinitialguess)(snes,snes->vec_sol,snes->initialguessP);CHKERRQ(ierr);
3894       }
3895     }
3896 
3897     if (snes->conv_hist_reset) snes->conv_hist_len = 0;
3898     if (snes->counters_reset) {snes->nfuncs = 0; snes->linear_its = 0; snes->numFailures = 0;}
3899 
3900     ierr = PetscLogEventBegin(SNES_Solve,snes,0,0,0);CHKERRQ(ierr);
3901     ierr = (*snes->ops->solve)(snes);CHKERRQ(ierr);
3902     ierr = PetscLogEventEnd(SNES_Solve,snes,0,0,0);CHKERRQ(ierr);
3903     if (!snes->reason) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Internal error, solver returned without setting converged reason");
3904     snes->domainerror = PETSC_FALSE; /* clear the flag if it has been set */
3905 
3906     if (snes->lagjac_persist) snes->jac_iter += snes->iter;
3907     if (snes->lagpre_persist) snes->pre_iter += snes->iter;
3908 
3909     flg  = PETSC_FALSE;
3910     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_test_local_min",&flg,NULL);CHKERRQ(ierr);
3911     if (flg && !PetscPreLoadingOn) { ierr = SNESTestLocalMin(snes);CHKERRQ(ierr); }
3912     ierr = SNESReasonViewFromOptions(snes);CHKERRQ(ierr);
3913 
3914     if (snes->errorifnotconverged && snes->reason < 0) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_NOT_CONVERGED,"SNESSolve has not converged");
3915     if (snes->reason < 0) break;
3916     if (grid <  snes->gridsequence) {
3917       DM  fine;
3918       Vec xnew;
3919       Mat interp;
3920 
3921       ierr = DMRefine(snes->dm,PetscObjectComm((PetscObject)snes),&fine);CHKERRQ(ierr);
3922       if (!fine) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_INCOMP,"DMRefine() did not perform any refinement, cannot continue grid sequencing");
3923       ierr = DMCreateInterpolation(snes->dm,fine,&interp,NULL);CHKERRQ(ierr);
3924       ierr = DMCreateGlobalVector(fine,&xnew);CHKERRQ(ierr);
3925       ierr = MatInterpolate(interp,x,xnew);CHKERRQ(ierr);
3926       ierr = DMInterpolate(snes->dm,interp,fine);CHKERRQ(ierr);
3927       ierr = MatDestroy(&interp);CHKERRQ(ierr);
3928       x    = xnew;
3929 
3930       ierr = SNESReset(snes);CHKERRQ(ierr);
3931       ierr = SNESSetDM(snes,fine);CHKERRQ(ierr);
3932       ierr = DMDestroy(&fine);CHKERRQ(ierr);
3933       ierr = PetscViewerASCIIPopTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)));CHKERRQ(ierr);
3934     }
3935   }
3936   ierr = SNESViewFromOptions(snes,NULL,"-snes_view");CHKERRQ(ierr);
3937   ierr = VecViewFromOptions(snes->vec_sol,(PetscObject)snes,"-snes_view_solution");CHKERRQ(ierr);
3938 
3939   ierr = VecDestroy(&xcreated);CHKERRQ(ierr);
3940   ierr = PetscObjectSAWsBlock((PetscObject)snes);CHKERRQ(ierr);
3941   PetscFunctionReturn(0);
3942 }
3943 
3944 /* --------- Internal routines for SNES Package --------- */
3945 
3946 #undef __FUNCT__
3947 #define __FUNCT__ "SNESSetType"
3948 /*@C
3949    SNESSetType - Sets the method for the nonlinear solver.
3950 
3951    Collective on SNES
3952 
3953    Input Parameters:
3954 +  snes - the SNES context
3955 -  type - a known method
3956 
3957    Options Database Key:
3958 .  -snes_type <type> - Sets the method; use -help for a list
3959    of available methods (for instance, newtonls or newtontr)
3960 
3961    Notes:
3962    See "petsc/include/petscsnes.h" for available methods (for instance)
3963 +    SNESNEWTONLS - Newton's method with line search
3964      (systems of nonlinear equations)
3965 .    SNESNEWTONTR - Newton's method with trust region
3966      (systems of nonlinear equations)
3967 
3968   Normally, it is best to use the SNESSetFromOptions() command and then
3969   set the SNES solver type from the options database rather than by using
3970   this routine.  Using the options database provides the user with
3971   maximum flexibility in evaluating the many nonlinear solvers.
3972   The SNESSetType() routine is provided for those situations where it
3973   is necessary to set the nonlinear solver independently of the command
3974   line or options database.  This might be the case, for example, when
3975   the choice of solver changes during the execution of the program,
3976   and the user's application is taking responsibility for choosing the
3977   appropriate method.
3978 
3979     Developer Notes: SNESRegister() adds a constructor for a new SNESType to SNESList, SNESSetType() locates
3980     the constructor in that list and calls it to create the spexific object.
3981 
3982   Level: intermediate
3983 
3984 .keywords: SNES, set, type
3985 
3986 .seealso: SNESType, SNESCreate(), SNESDestroy(), SNESGetType(), SNESSetFromOptions()
3987 
3988 @*/
3989 PetscErrorCode  SNESSetType(SNES snes,SNESType type)
3990 {
3991   PetscErrorCode ierr,(*r)(SNES);
3992   PetscBool      match;
3993 
3994   PetscFunctionBegin;
3995   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3996   PetscValidCharPointer(type,2);
3997 
3998   ierr = PetscObjectTypeCompare((PetscObject)snes,type,&match);CHKERRQ(ierr);
3999   if (match) PetscFunctionReturn(0);
4000 
4001   ierr =  PetscFunctionListFind(SNESList,type,&r);CHKERRQ(ierr);
4002   if (!r) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_UNKNOWN_TYPE,"Unable to find requested SNES type %s",type);
4003   /* Destroy the previous private SNES context */
4004   if (snes->ops->destroy) {
4005     ierr               = (*(snes)->ops->destroy)(snes);CHKERRQ(ierr);
4006     snes->ops->destroy = NULL;
4007   }
4008   /* Reinitialize function pointers in SNESOps structure */
4009   snes->ops->setup          = 0;
4010   snes->ops->solve          = 0;
4011   snes->ops->view           = 0;
4012   snes->ops->setfromoptions = 0;
4013   snes->ops->destroy        = 0;
4014   /* Call the SNESCreate_XXX routine for this particular Nonlinear solver */
4015   snes->setupcalled = PETSC_FALSE;
4016 
4017   ierr = PetscObjectChangeTypeName((PetscObject)snes,type);CHKERRQ(ierr);
4018   ierr = (*r)(snes);CHKERRQ(ierr);
4019   PetscFunctionReturn(0);
4020 }
4021 
4022 #undef __FUNCT__
4023 #define __FUNCT__ "SNESGetType"
4024 /*@C
4025    SNESGetType - Gets the SNES method type and name (as a string).
4026 
4027    Not Collective
4028 
4029    Input Parameter:
4030 .  snes - nonlinear solver context
4031 
4032    Output Parameter:
4033 .  type - SNES method (a character string)
4034 
4035    Level: intermediate
4036 
4037 .keywords: SNES, nonlinear, get, type, name
4038 @*/
4039 PetscErrorCode  SNESGetType(SNES snes,SNESType *type)
4040 {
4041   PetscFunctionBegin;
4042   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4043   PetscValidPointer(type,2);
4044   *type = ((PetscObject)snes)->type_name;
4045   PetscFunctionReturn(0);
4046 }
4047 
4048 #undef __FUNCT__
4049 #define __FUNCT__ "SNESSetSolution"
4050 /*@
4051   SNESSetSolution - Sets the solution vector for use by the SNES routines.
4052 
4053   Logically Collective on SNES and Vec
4054 
4055   Input Parameters:
4056 + snes - the SNES context obtained from SNESCreate()
4057 - u    - the solution vector
4058 
4059   Level: beginner
4060 
4061 .keywords: SNES, set, solution
4062 @*/
4063 PetscErrorCode SNESSetSolution(SNES snes, Vec u)
4064 {
4065   DM             dm;
4066   PetscErrorCode ierr;
4067 
4068   PetscFunctionBegin;
4069   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4070   PetscValidHeaderSpecific(u, VEC_CLASSID, 2);
4071   ierr = PetscObjectReference((PetscObject) u);CHKERRQ(ierr);
4072   ierr = VecDestroy(&snes->vec_sol);CHKERRQ(ierr);
4073 
4074   snes->vec_sol = u;
4075 
4076   ierr = SNESGetDM(snes, &dm);CHKERRQ(ierr);
4077   ierr = DMShellSetGlobalVector(dm, u);CHKERRQ(ierr);
4078   PetscFunctionReturn(0);
4079 }
4080 
4081 #undef __FUNCT__
4082 #define __FUNCT__ "SNESGetSolution"
4083 /*@
4084    SNESGetSolution - Returns the vector where the approximate solution is
4085    stored. This is the fine grid solution when using SNESSetGridSequence().
4086 
4087    Not Collective, but Vec is parallel if SNES is parallel
4088 
4089    Input Parameter:
4090 .  snes - the SNES context
4091 
4092    Output Parameter:
4093 .  x - the solution
4094 
4095    Level: intermediate
4096 
4097 .keywords: SNES, nonlinear, get, solution
4098 
4099 .seealso:  SNESGetSolutionUpdate(), SNESGetFunction()
4100 @*/
4101 PetscErrorCode  SNESGetSolution(SNES snes,Vec *x)
4102 {
4103   PetscFunctionBegin;
4104   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4105   PetscValidPointer(x,2);
4106   *x = snes->vec_sol;
4107   PetscFunctionReturn(0);
4108 }
4109 
4110 #undef __FUNCT__
4111 #define __FUNCT__ "SNESGetSolutionUpdate"
4112 /*@
4113    SNESGetSolutionUpdate - Returns the vector where the solution update is
4114    stored.
4115 
4116    Not Collective, but Vec is parallel if SNES is parallel
4117 
4118    Input Parameter:
4119 .  snes - the SNES context
4120 
4121    Output Parameter:
4122 .  x - the solution update
4123 
4124    Level: advanced
4125 
4126 .keywords: SNES, nonlinear, get, solution, update
4127 
4128 .seealso: SNESGetSolution(), SNESGetFunction()
4129 @*/
4130 PetscErrorCode  SNESGetSolutionUpdate(SNES snes,Vec *x)
4131 {
4132   PetscFunctionBegin;
4133   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4134   PetscValidPointer(x,2);
4135   *x = snes->vec_sol_update;
4136   PetscFunctionReturn(0);
4137 }
4138 
4139 #undef __FUNCT__
4140 #define __FUNCT__ "SNESGetFunction"
4141 /*@C
4142    SNESGetFunction - Returns the vector where the function is stored.
4143 
4144    Not Collective, but Vec is parallel if SNES is parallel. Collective if Vec is requested, but has not been created yet.
4145 
4146    Input Parameter:
4147 .  snes - the SNES context
4148 
4149    Output Parameter:
4150 +  r - the vector that is used to store residuals (or NULL if you don't want it)
4151 .  f - the function (or NULL if you don't want it); see SNESFunction for calling sequence details
4152 -  ctx - the function context (or NULL if you don't want it)
4153 
4154    Level: advanced
4155 
4156 .keywords: SNES, nonlinear, get, function
4157 
4158 .seealso: SNESSetFunction(), SNESGetSolution(), SNESFunction
4159 @*/
4160 PetscErrorCode  SNESGetFunction(SNES snes,Vec *r,PetscErrorCode (**f)(SNES,Vec,Vec,void*),void **ctx)
4161 {
4162   PetscErrorCode ierr;
4163   DM             dm;
4164 
4165   PetscFunctionBegin;
4166   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4167   if (r) {
4168     if (!snes->vec_func) {
4169       if (snes->vec_rhs) {
4170         ierr = VecDuplicate(snes->vec_rhs,&snes->vec_func);CHKERRQ(ierr);
4171       } else if (snes->vec_sol) {
4172         ierr = VecDuplicate(snes->vec_sol,&snes->vec_func);CHKERRQ(ierr);
4173       } else if (snes->dm) {
4174         ierr = DMCreateGlobalVector(snes->dm,&snes->vec_func);CHKERRQ(ierr);
4175       }
4176     }
4177     *r = snes->vec_func;
4178   }
4179   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
4180   ierr = DMSNESGetFunction(dm,f,ctx);CHKERRQ(ierr);
4181   PetscFunctionReturn(0);
4182 }
4183 
4184 /*@C
4185    SNESGetNGS - Returns the NGS function and context.
4186 
4187    Input Parameter:
4188 .  snes - the SNES context
4189 
4190    Output Parameter:
4191 +  f - the function (or NULL) see SNESNGSFunction for details
4192 -  ctx    - the function context (or NULL)
4193 
4194    Level: advanced
4195 
4196 .keywords: SNES, nonlinear, get, function
4197 
4198 .seealso: SNESSetNGS(), SNESGetFunction()
4199 @*/
4200 
4201 #undef __FUNCT__
4202 #define __FUNCT__ "SNESGetNGS"
4203 PetscErrorCode SNESGetNGS (SNES snes, PetscErrorCode (**f)(SNES, Vec, Vec, void*), void ** ctx)
4204 {
4205   PetscErrorCode ierr;
4206   DM             dm;
4207 
4208   PetscFunctionBegin;
4209   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4210   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
4211   ierr = DMSNESGetNGS(dm,f,ctx);CHKERRQ(ierr);
4212   PetscFunctionReturn(0);
4213 }
4214 
4215 #undef __FUNCT__
4216 #define __FUNCT__ "SNESSetOptionsPrefix"
4217 /*@C
4218    SNESSetOptionsPrefix - Sets the prefix used for searching for all
4219    SNES options in the database.
4220 
4221    Logically Collective on SNES
4222 
4223    Input Parameter:
4224 +  snes - the SNES context
4225 -  prefix - the prefix to prepend to all option names
4226 
4227    Notes:
4228    A hyphen (-) must NOT be given at the beginning of the prefix name.
4229    The first character of all runtime options is AUTOMATICALLY the hyphen.
4230 
4231    Level: advanced
4232 
4233 .keywords: SNES, set, options, prefix, database
4234 
4235 .seealso: SNESSetFromOptions()
4236 @*/
4237 PetscErrorCode  SNESSetOptionsPrefix(SNES snes,const char prefix[])
4238 {
4239   PetscErrorCode ierr;
4240 
4241   PetscFunctionBegin;
4242   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4243   ierr = PetscObjectSetOptionsPrefix((PetscObject)snes,prefix);CHKERRQ(ierr);
4244   if (!snes->ksp) {ierr = SNESGetKSP(snes,&snes->ksp);CHKERRQ(ierr);}
4245   if (snes->linesearch) {
4246     ierr = SNESGetLineSearch(snes,&snes->linesearch);CHKERRQ(ierr);
4247     ierr = PetscObjectSetOptionsPrefix((PetscObject)snes->linesearch,prefix);CHKERRQ(ierr);
4248   }
4249   ierr = KSPSetOptionsPrefix(snes->ksp,prefix);CHKERRQ(ierr);
4250   PetscFunctionReturn(0);
4251 }
4252 
4253 #undef __FUNCT__
4254 #define __FUNCT__ "SNESAppendOptionsPrefix"
4255 /*@C
4256    SNESAppendOptionsPrefix - Appends to the prefix used for searching for all
4257    SNES options in the database.
4258 
4259    Logically Collective on SNES
4260 
4261    Input Parameters:
4262 +  snes - the SNES context
4263 -  prefix - the prefix to prepend to all option names
4264 
4265    Notes:
4266    A hyphen (-) must NOT be given at the beginning of the prefix name.
4267    The first character of all runtime options is AUTOMATICALLY the hyphen.
4268 
4269    Level: advanced
4270 
4271 .keywords: SNES, append, options, prefix, database
4272 
4273 .seealso: SNESGetOptionsPrefix()
4274 @*/
4275 PetscErrorCode  SNESAppendOptionsPrefix(SNES snes,const char prefix[])
4276 {
4277   PetscErrorCode ierr;
4278 
4279   PetscFunctionBegin;
4280   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4281   ierr = PetscObjectAppendOptionsPrefix((PetscObject)snes,prefix);CHKERRQ(ierr);
4282   if (!snes->ksp) {ierr = SNESGetKSP(snes,&snes->ksp);CHKERRQ(ierr);}
4283   if (snes->linesearch) {
4284     ierr = SNESGetLineSearch(snes,&snes->linesearch);CHKERRQ(ierr);
4285     ierr = PetscObjectAppendOptionsPrefix((PetscObject)snes->linesearch,prefix);CHKERRQ(ierr);
4286   }
4287   ierr = KSPAppendOptionsPrefix(snes->ksp,prefix);CHKERRQ(ierr);
4288   PetscFunctionReturn(0);
4289 }
4290 
4291 #undef __FUNCT__
4292 #define __FUNCT__ "SNESGetOptionsPrefix"
4293 /*@C
4294    SNESGetOptionsPrefix - Sets the prefix used for searching for all
4295    SNES options in the database.
4296 
4297    Not Collective
4298 
4299    Input Parameter:
4300 .  snes - the SNES context
4301 
4302    Output Parameter:
4303 .  prefix - pointer to the prefix string used
4304 
4305    Notes: On the fortran side, the user should pass in a string 'prefix' of
4306    sufficient length to hold the prefix.
4307 
4308    Level: advanced
4309 
4310 .keywords: SNES, get, options, prefix, database
4311 
4312 .seealso: SNESAppendOptionsPrefix()
4313 @*/
4314 PetscErrorCode  SNESGetOptionsPrefix(SNES snes,const char *prefix[])
4315 {
4316   PetscErrorCode ierr;
4317 
4318   PetscFunctionBegin;
4319   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4320   ierr = PetscObjectGetOptionsPrefix((PetscObject)snes,prefix);CHKERRQ(ierr);
4321   PetscFunctionReturn(0);
4322 }
4323 
4324 
4325 #undef __FUNCT__
4326 #define __FUNCT__ "SNESRegister"
4327 /*@C
4328   SNESRegister - Adds a method to the nonlinear solver package.
4329 
4330    Not collective
4331 
4332    Input Parameters:
4333 +  name_solver - name of a new user-defined solver
4334 -  routine_create - routine to create method context
4335 
4336    Notes:
4337    SNESRegister() may be called multiple times to add several user-defined solvers.
4338 
4339    Sample usage:
4340 .vb
4341    SNESRegister("my_solver",MySolverCreate);
4342 .ve
4343 
4344    Then, your solver can be chosen with the procedural interface via
4345 $     SNESSetType(snes,"my_solver")
4346    or at runtime via the option
4347 $     -snes_type my_solver
4348 
4349    Level: advanced
4350 
4351     Note: If your function is not being put into a shared library then use SNESRegister() instead
4352 
4353 .keywords: SNES, nonlinear, register
4354 
4355 .seealso: SNESRegisterAll(), SNESRegisterDestroy()
4356 
4357   Level: advanced
4358 @*/
4359 PetscErrorCode  SNESRegister(const char sname[],PetscErrorCode (*function)(SNES))
4360 {
4361   PetscErrorCode ierr;
4362 
4363   PetscFunctionBegin;
4364   ierr = PetscFunctionListAdd(&SNESList,sname,function);CHKERRQ(ierr);
4365   PetscFunctionReturn(0);
4366 }
4367 
4368 #undef __FUNCT__
4369 #define __FUNCT__ "SNESTestLocalMin"
4370 PetscErrorCode  SNESTestLocalMin(SNES snes)
4371 {
4372   PetscErrorCode ierr;
4373   PetscInt       N,i,j;
4374   Vec            u,uh,fh;
4375   PetscScalar    value;
4376   PetscReal      norm;
4377 
4378   PetscFunctionBegin;
4379   ierr = SNESGetSolution(snes,&u);CHKERRQ(ierr);
4380   ierr = VecDuplicate(u,&uh);CHKERRQ(ierr);
4381   ierr = VecDuplicate(u,&fh);CHKERRQ(ierr);
4382 
4383   /* currently only works for sequential */
4384   ierr = PetscPrintf(PETSC_COMM_WORLD,"Testing FormFunction() for local min\n");CHKERRQ(ierr);
4385   ierr = VecGetSize(u,&N);CHKERRQ(ierr);
4386   for (i=0; i<N; i++) {
4387     ierr = VecCopy(u,uh);CHKERRQ(ierr);
4388     ierr = PetscPrintf(PETSC_COMM_WORLD,"i = %D\n",i);CHKERRQ(ierr);
4389     for (j=-10; j<11; j++) {
4390       value = PetscSign(j)*PetscExpReal(PetscAbs(j)-10.0);
4391       ierr  = VecSetValue(uh,i,value,ADD_VALUES);CHKERRQ(ierr);
4392       ierr  = SNESComputeFunction(snes,uh,fh);CHKERRQ(ierr);
4393       ierr  = VecNorm(fh,NORM_2,&norm);CHKERRQ(ierr);
4394       ierr  = PetscPrintf(PETSC_COMM_WORLD,"       j norm %D %18.16e\n",j,norm);CHKERRQ(ierr);
4395       value = -value;
4396       ierr  = VecSetValue(uh,i,value,ADD_VALUES);CHKERRQ(ierr);
4397     }
4398   }
4399   ierr = VecDestroy(&uh);CHKERRQ(ierr);
4400   ierr = VecDestroy(&fh);CHKERRQ(ierr);
4401   PetscFunctionReturn(0);
4402 }
4403 
4404 #undef __FUNCT__
4405 #define __FUNCT__ "SNESKSPSetUseEW"
4406 /*@
4407    SNESKSPSetUseEW - Sets SNES use Eisenstat-Walker method for
4408    computing relative tolerance for linear solvers within an inexact
4409    Newton method.
4410 
4411    Logically Collective on SNES
4412 
4413    Input Parameters:
4414 +  snes - SNES context
4415 -  flag - PETSC_TRUE or PETSC_FALSE
4416 
4417     Options Database:
4418 +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
4419 .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
4420 .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
4421 .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
4422 .  -snes_ksp_ew_gamma <gamma> - Sets gamma
4423 .  -snes_ksp_ew_alpha <alpha> - Sets alpha
4424 .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
4425 -  -snes_ksp_ew_threshold <threshold> - Sets threshold
4426 
4427    Notes:
4428    Currently, the default is to use a constant relative tolerance for
4429    the inner linear solvers.  Alternatively, one can use the
4430    Eisenstat-Walker method, where the relative convergence tolerance
4431    is reset at each Newton iteration according progress of the nonlinear
4432    solver.
4433 
4434    Level: advanced
4435 
4436    Reference:
4437    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
4438    inexact Newton method", SISC 17 (1), pp.16-32, 1996.
4439 
4440 .keywords: SNES, KSP, Eisenstat, Walker, convergence, test, inexact, Newton
4441 
4442 .seealso: SNESKSPGetUseEW(), SNESKSPGetParametersEW(), SNESKSPSetParametersEW()
4443 @*/
4444 PetscErrorCode  SNESKSPSetUseEW(SNES snes,PetscBool flag)
4445 {
4446   PetscFunctionBegin;
4447   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4448   PetscValidLogicalCollectiveBool(snes,flag,2);
4449   snes->ksp_ewconv = flag;
4450   PetscFunctionReturn(0);
4451 }
4452 
4453 #undef __FUNCT__
4454 #define __FUNCT__ "SNESKSPGetUseEW"
4455 /*@
4456    SNESKSPGetUseEW - Gets if SNES is using Eisenstat-Walker method
4457    for computing relative tolerance for linear solvers within an
4458    inexact Newton method.
4459 
4460    Not Collective
4461 
4462    Input Parameter:
4463 .  snes - SNES context
4464 
4465    Output Parameter:
4466 .  flag - PETSC_TRUE or PETSC_FALSE
4467 
4468    Notes:
4469    Currently, the default is to use a constant relative tolerance for
4470    the inner linear solvers.  Alternatively, one can use the
4471    Eisenstat-Walker method, where the relative convergence tolerance
4472    is reset at each Newton iteration according progress of the nonlinear
4473    solver.
4474 
4475    Level: advanced
4476 
4477    Reference:
4478    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
4479    inexact Newton method", SISC 17 (1), pp.16-32, 1996.
4480 
4481 .keywords: SNES, KSP, Eisenstat, Walker, convergence, test, inexact, Newton
4482 
4483 .seealso: SNESKSPSetUseEW(), SNESKSPGetParametersEW(), SNESKSPSetParametersEW()
4484 @*/
4485 PetscErrorCode  SNESKSPGetUseEW(SNES snes, PetscBool  *flag)
4486 {
4487   PetscFunctionBegin;
4488   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4489   PetscValidPointer(flag,2);
4490   *flag = snes->ksp_ewconv;
4491   PetscFunctionReturn(0);
4492 }
4493 
4494 #undef __FUNCT__
4495 #define __FUNCT__ "SNESKSPSetParametersEW"
4496 /*@
4497    SNESKSPSetParametersEW - Sets parameters for Eisenstat-Walker
4498    convergence criteria for the linear solvers within an inexact
4499    Newton method.
4500 
4501    Logically Collective on SNES
4502 
4503    Input Parameters:
4504 +    snes - SNES context
4505 .    version - version 1, 2 (default is 2) or 3
4506 .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
4507 .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
4508 .    gamma - multiplicative factor for version 2 rtol computation
4509              (0 <= gamma2 <= 1)
4510 .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
4511 .    alpha2 - power for safeguard
4512 -    threshold - threshold for imposing safeguard (0 < threshold < 1)
4513 
4514    Note:
4515    Version 3 was contributed by Luis Chacon, June 2006.
4516 
4517    Use PETSC_DEFAULT to retain the default for any of the parameters.
4518 
4519    Level: advanced
4520 
4521    Reference:
4522    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
4523    inexact Newton method", Utah State University Math. Stat. Dept. Res.
4524    Report 6/94/75, June, 1994, to appear in SIAM J. Sci. Comput.
4525 
4526 .keywords: SNES, KSP, Eisenstat, Walker, set, parameters
4527 
4528 .seealso: SNESKSPSetUseEW(), SNESKSPGetUseEW(), SNESKSPGetParametersEW()
4529 @*/
4530 PetscErrorCode  SNESKSPSetParametersEW(SNES snes,PetscInt version,PetscReal rtol_0,PetscReal rtol_max,PetscReal gamma,PetscReal alpha,PetscReal alpha2,PetscReal threshold)
4531 {
4532   SNESKSPEW *kctx;
4533 
4534   PetscFunctionBegin;
4535   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4536   kctx = (SNESKSPEW*)snes->kspconvctx;
4537   if (!kctx) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"No Eisenstat-Walker context existing");
4538   PetscValidLogicalCollectiveInt(snes,version,2);
4539   PetscValidLogicalCollectiveReal(snes,rtol_0,3);
4540   PetscValidLogicalCollectiveReal(snes,rtol_max,4);
4541   PetscValidLogicalCollectiveReal(snes,gamma,5);
4542   PetscValidLogicalCollectiveReal(snes,alpha,6);
4543   PetscValidLogicalCollectiveReal(snes,alpha2,7);
4544   PetscValidLogicalCollectiveReal(snes,threshold,8);
4545 
4546   if (version != PETSC_DEFAULT)   kctx->version   = version;
4547   if (rtol_0 != PETSC_DEFAULT)    kctx->rtol_0    = rtol_0;
4548   if (rtol_max != PETSC_DEFAULT)  kctx->rtol_max  = rtol_max;
4549   if (gamma != PETSC_DEFAULT)     kctx->gamma     = gamma;
4550   if (alpha != PETSC_DEFAULT)     kctx->alpha     = alpha;
4551   if (alpha2 != PETSC_DEFAULT)    kctx->alpha2    = alpha2;
4552   if (threshold != PETSC_DEFAULT) kctx->threshold = threshold;
4553 
4554   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);
4555   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",(double)kctx->rtol_0);
4556   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",(double)kctx->rtol_max);
4557   if (kctx->gamma < 0.0 || kctx->gamma > 1.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"0.0 <= gamma (%g) <= 1.0\n",(double)kctx->gamma);
4558   if (kctx->alpha <= 1.0 || kctx->alpha > 2.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"1.0 < alpha (%g) <= 2.0\n",(double)kctx->alpha);
4559   if (kctx->threshold <= 0.0 || kctx->threshold >= 1.0) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"0.0 < threshold (%g) < 1.0\n",(double)kctx->threshold);
4560   PetscFunctionReturn(0);
4561 }
4562 
4563 #undef __FUNCT__
4564 #define __FUNCT__ "SNESKSPGetParametersEW"
4565 /*@
4566    SNESKSPGetParametersEW - Gets parameters for Eisenstat-Walker
4567    convergence criteria for the linear solvers within an inexact
4568    Newton method.
4569 
4570    Not Collective
4571 
4572    Input Parameters:
4573      snes - SNES context
4574 
4575    Output Parameters:
4576 +    version - version 1, 2 (default is 2) or 3
4577 .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
4578 .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
4579 .    gamma - multiplicative factor for version 2 rtol computation (0 <= gamma2 <= 1)
4580 .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
4581 .    alpha2 - power for safeguard
4582 -    threshold - threshold for imposing safeguard (0 < threshold < 1)
4583 
4584    Level: advanced
4585 
4586 .keywords: SNES, KSP, Eisenstat, Walker, get, parameters
4587 
4588 .seealso: SNESKSPSetUseEW(), SNESKSPGetUseEW(), SNESKSPSetParametersEW()
4589 @*/
4590 PetscErrorCode  SNESKSPGetParametersEW(SNES snes,PetscInt *version,PetscReal *rtol_0,PetscReal *rtol_max,PetscReal *gamma,PetscReal *alpha,PetscReal *alpha2,PetscReal *threshold)
4591 {
4592   SNESKSPEW *kctx;
4593 
4594   PetscFunctionBegin;
4595   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4596   kctx = (SNESKSPEW*)snes->kspconvctx;
4597   if (!kctx) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"No Eisenstat-Walker context existing");
4598   if (version)   *version   = kctx->version;
4599   if (rtol_0)    *rtol_0    = kctx->rtol_0;
4600   if (rtol_max)  *rtol_max  = kctx->rtol_max;
4601   if (gamma)     *gamma     = kctx->gamma;
4602   if (alpha)     *alpha     = kctx->alpha;
4603   if (alpha2)    *alpha2    = kctx->alpha2;
4604   if (threshold) *threshold = kctx->threshold;
4605   PetscFunctionReturn(0);
4606 }
4607 
4608 #undef __FUNCT__
4609 #define __FUNCT__ "KSPPreSolve_SNESEW"
4610  PetscErrorCode KSPPreSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
4611 {
4612   PetscErrorCode ierr;
4613   SNESKSPEW      *kctx = (SNESKSPEW*)snes->kspconvctx;
4614   PetscReal      rtol  = PETSC_DEFAULT,stol;
4615 
4616   PetscFunctionBegin;
4617   if (!snes->ksp_ewconv) PetscFunctionReturn(0);
4618   if (!snes->iter) {
4619     rtol = kctx->rtol_0; /* first time in, so use the original user rtol */
4620     ierr = VecNorm(snes->vec_func,NORM_2,&kctx->norm_first);CHKERRQ(ierr);
4621   }
4622   else {
4623     if (kctx->version == 1) {
4624       rtol = (snes->norm - kctx->lresid_last)/kctx->norm_last;
4625       if (rtol < 0.0) rtol = -rtol;
4626       stol = PetscPowReal(kctx->rtol_last,kctx->alpha2);
4627       if (stol > kctx->threshold) rtol = PetscMax(rtol,stol);
4628     } else if (kctx->version == 2) {
4629       rtol = kctx->gamma * PetscPowReal(snes->norm/kctx->norm_last,kctx->alpha);
4630       stol = kctx->gamma * PetscPowReal(kctx->rtol_last,kctx->alpha);
4631       if (stol > kctx->threshold) rtol = PetscMax(rtol,stol);
4632     } else if (kctx->version == 3) { /* contributed by Luis Chacon, June 2006. */
4633       rtol = kctx->gamma * PetscPowReal(snes->norm/kctx->norm_last,kctx->alpha);
4634       /* safeguard: avoid sharp decrease of rtol */
4635       stol = kctx->gamma*PetscPowReal(kctx->rtol_last,kctx->alpha);
4636       stol = PetscMax(rtol,stol);
4637       rtol = PetscMin(kctx->rtol_0,stol);
4638       /* safeguard: avoid oversolving */
4639       stol = kctx->gamma*(kctx->norm_first*snes->rtol)/snes->norm;
4640       stol = PetscMax(rtol,stol);
4641       rtol = PetscMin(kctx->rtol_0,stol);
4642     } else SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Only versions 1, 2 or 3 are supported: %D",kctx->version);
4643   }
4644   /* safeguard: avoid rtol greater than one */
4645   rtol = PetscMin(rtol,kctx->rtol_max);
4646   ierr = KSPSetTolerances(ksp,rtol,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);CHKERRQ(ierr);
4647   ierr = PetscInfo3(snes,"iter %D, Eisenstat-Walker (version %D) KSP rtol=%g\n",snes->iter,kctx->version,(double)rtol);CHKERRQ(ierr);
4648   PetscFunctionReturn(0);
4649 }
4650 
4651 #undef __FUNCT__
4652 #define __FUNCT__ "KSPPostSolve_SNESEW"
4653 PetscErrorCode KSPPostSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
4654 {
4655   PetscErrorCode ierr;
4656   SNESKSPEW      *kctx = (SNESKSPEW*)snes->kspconvctx;
4657   PCSide         pcside;
4658   Vec            lres;
4659 
4660   PetscFunctionBegin;
4661   if (!snes->ksp_ewconv) PetscFunctionReturn(0);
4662   ierr = KSPGetTolerances(ksp,&kctx->rtol_last,0,0,0);CHKERRQ(ierr);
4663   kctx->norm_last = snes->norm;
4664   if (kctx->version == 1) {
4665     PC        pc;
4666     PetscBool isNone;
4667 
4668     ierr = KSPGetPC(ksp, &pc);CHKERRQ(ierr);
4669     ierr = PetscObjectTypeCompare((PetscObject) pc, PCNONE, &isNone);CHKERRQ(ierr);
4670     ierr = KSPGetPCSide(ksp,&pcside);CHKERRQ(ierr);
4671      if (pcside == PC_RIGHT || isNone) { /* XXX Should we also test KSP_UNPRECONDITIONED_NORM ? */
4672       /* KSP residual is true linear residual */
4673       ierr = KSPGetResidualNorm(ksp,&kctx->lresid_last);CHKERRQ(ierr);
4674     } else {
4675       /* KSP residual is preconditioned residual */
4676       /* compute true linear residual norm */
4677       ierr = VecDuplicate(b,&lres);CHKERRQ(ierr);
4678       ierr = MatMult(snes->jacobian,x,lres);CHKERRQ(ierr);
4679       ierr = VecAYPX(lres,-1.0,b);CHKERRQ(ierr);
4680       ierr = VecNorm(lres,NORM_2,&kctx->lresid_last);CHKERRQ(ierr);
4681       ierr = VecDestroy(&lres);CHKERRQ(ierr);
4682     }
4683   }
4684   PetscFunctionReturn(0);
4685 }
4686 
4687 #undef __FUNCT__
4688 #define __FUNCT__ "SNESGetKSP"
4689 /*@
4690    SNESGetKSP - Returns the KSP context for a SNES solver.
4691 
4692    Not Collective, but if SNES object is parallel, then KSP object is parallel
4693 
4694    Input Parameter:
4695 .  snes - the SNES context
4696 
4697    Output Parameter:
4698 .  ksp - the KSP context
4699 
4700    Notes:
4701    The user can then directly manipulate the KSP context to set various
4702    options, etc.  Likewise, the user can then extract and manipulate the
4703    PC contexts as well.
4704 
4705    Level: beginner
4706 
4707 .keywords: SNES, nonlinear, get, KSP, context
4708 
4709 .seealso: KSPGetPC(), SNESCreate(), KSPCreate(), SNESSetKSP()
4710 @*/
4711 PetscErrorCode  SNESGetKSP(SNES snes,KSP *ksp)
4712 {
4713   PetscErrorCode ierr;
4714 
4715   PetscFunctionBegin;
4716   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4717   PetscValidPointer(ksp,2);
4718 
4719   if (!snes->ksp) {
4720     PetscBool monitor = PETSC_FALSE;
4721 
4722     ierr = KSPCreate(PetscObjectComm((PetscObject)snes),&snes->ksp);CHKERRQ(ierr);
4723     ierr = PetscObjectIncrementTabLevel((PetscObject)snes->ksp,(PetscObject)snes,1);CHKERRQ(ierr);
4724     ierr = PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->ksp);CHKERRQ(ierr);
4725 
4726     ierr = KSPSetPreSolve(snes->ksp,(PetscErrorCode (*)(KSP,Vec,Vec,void*))KSPPreSolve_SNESEW,snes);CHKERRQ(ierr);
4727     ierr = KSPSetPostSolve(snes->ksp,(PetscErrorCode (*)(KSP,Vec,Vec,void*))KSPPostSolve_SNESEW,snes);CHKERRQ(ierr);
4728 
4729     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-ksp_monitor_snes",&monitor,NULL);CHKERRQ(ierr);
4730     if (monitor) {
4731       ierr = KSPMonitorSet(snes->ksp,KSPMonitorSNES,snes,NULL);CHKERRQ(ierr);
4732     }
4733     monitor = PETSC_FALSE;
4734     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-ksp_monitor_snes_lg",&monitor,NULL);CHKERRQ(ierr);
4735     if (monitor) {
4736       PetscObject *objs;
4737       ierr = KSPMonitorSNESLGResidualNormCreate(PetscObjectComm((PetscObject)snes),NULL,NULL,PETSC_DECIDE,PETSC_DECIDE,600,600,&objs);CHKERRQ(ierr);
4738       objs[0] = (PetscObject) snes;
4739       ierr = KSPMonitorSet(snes->ksp,(PetscErrorCode (*)(KSP,PetscInt,PetscReal,void*))KSPMonitorSNESLGResidualNorm,objs,(PetscErrorCode (*)(void**))KSPMonitorSNESLGResidualNormDestroy);CHKERRQ(ierr);
4740     }
4741   }
4742   *ksp = snes->ksp;
4743   PetscFunctionReturn(0);
4744 }
4745 
4746 
4747 #include <petsc/private/dmimpl.h>
4748 #undef __FUNCT__
4749 #define __FUNCT__ "SNESSetDM"
4750 /*@
4751    SNESSetDM - Sets the DM that may be used by some preconditioners
4752 
4753    Logically Collective on SNES
4754 
4755    Input Parameters:
4756 +  snes - the preconditioner context
4757 -  dm - the dm
4758 
4759    Level: intermediate
4760 
4761 .seealso: SNESGetDM(), KSPSetDM(), KSPGetDM()
4762 @*/
4763 PetscErrorCode  SNESSetDM(SNES snes,DM dm)
4764 {
4765   PetscErrorCode ierr;
4766   KSP            ksp;
4767   DMSNES         sdm;
4768 
4769   PetscFunctionBegin;
4770   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4771   if (dm) {ierr = PetscObjectReference((PetscObject)dm);CHKERRQ(ierr);}
4772   if (snes->dm) {               /* Move the DMSNES context over to the new DM unless the new DM already has one */
4773     if (snes->dm->dmsnes && snes->dmAuto && !dm->dmsnes) {
4774       ierr = DMCopyDMSNES(snes->dm,dm);CHKERRQ(ierr);
4775       ierr = DMGetDMSNES(snes->dm,&sdm);CHKERRQ(ierr);
4776       if (sdm->originaldm == snes->dm) sdm->originaldm = dm; /* Grant write privileges to the replacement DM */
4777     }
4778     ierr = DMDestroy(&snes->dm);CHKERRQ(ierr);
4779   }
4780   snes->dm     = dm;
4781   snes->dmAuto = PETSC_FALSE;
4782 
4783   ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
4784   ierr = KSPSetDM(ksp,dm);CHKERRQ(ierr);
4785   ierr = KSPSetDMActive(ksp,PETSC_FALSE);CHKERRQ(ierr);
4786   if (snes->pc) {
4787     ierr = SNESSetDM(snes->pc, snes->dm);CHKERRQ(ierr);
4788     ierr = SNESSetNPCSide(snes,snes->pcside);CHKERRQ(ierr);
4789   }
4790   PetscFunctionReturn(0);
4791 }
4792 
4793 #undef __FUNCT__
4794 #define __FUNCT__ "SNESGetDM"
4795 /*@
4796    SNESGetDM - Gets the DM that may be used by some preconditioners
4797 
4798    Not Collective but DM obtained is parallel on SNES
4799 
4800    Input Parameter:
4801 . snes - the preconditioner context
4802 
4803    Output Parameter:
4804 .  dm - the dm
4805 
4806    Level: intermediate
4807 
4808 .seealso: SNESSetDM(), KSPSetDM(), KSPGetDM()
4809 @*/
4810 PetscErrorCode  SNESGetDM(SNES snes,DM *dm)
4811 {
4812   PetscErrorCode ierr;
4813 
4814   PetscFunctionBegin;
4815   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4816   if (!snes->dm) {
4817     ierr         = DMShellCreate(PetscObjectComm((PetscObject)snes),&snes->dm);CHKERRQ(ierr);
4818     snes->dmAuto = PETSC_TRUE;
4819   }
4820   *dm = snes->dm;
4821   PetscFunctionReturn(0);
4822 }
4823 
4824 #undef __FUNCT__
4825 #define __FUNCT__ "SNESSetNPC"
4826 /*@
4827   SNESSetNPC - Sets the nonlinear preconditioner to be used.
4828 
4829   Collective on SNES
4830 
4831   Input Parameters:
4832 + snes - iterative context obtained from SNESCreate()
4833 - pc   - the preconditioner object
4834 
4835   Notes:
4836   Use SNESGetNPC() to retrieve the preconditioner context (for example,
4837   to configure it using the API).
4838 
4839   Level: developer
4840 
4841 .keywords: SNES, set, precondition
4842 .seealso: SNESGetNPC(), SNESHasNPC()
4843 @*/
4844 PetscErrorCode SNESSetNPC(SNES snes, SNES pc)
4845 {
4846   PetscErrorCode ierr;
4847 
4848   PetscFunctionBegin;
4849   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4850   PetscValidHeaderSpecific(pc, SNES_CLASSID, 2);
4851   PetscCheckSameComm(snes, 1, pc, 2);
4852   ierr     = PetscObjectReference((PetscObject) pc);CHKERRQ(ierr);
4853   ierr     = SNESDestroy(&snes->pc);CHKERRQ(ierr);
4854   snes->pc = pc;
4855   ierr     = PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->pc);CHKERRQ(ierr);
4856   PetscFunctionReturn(0);
4857 }
4858 
4859 #undef __FUNCT__
4860 #define __FUNCT__ "SNESGetNPC"
4861 /*@
4862   SNESGetNPC - Creates a nonlinear preconditioning solver (SNES) to be used to precondition the nonlinear solver.
4863 
4864   Not Collective
4865 
4866   Input Parameter:
4867 . snes - iterative context obtained from SNESCreate()
4868 
4869   Output Parameter:
4870 . pc - preconditioner context
4871 
4872   Notes: If a SNES was previously set with SNESSetNPC() then that SNES is returned.
4873 
4874   Level: developer
4875 
4876 .keywords: SNES, get, preconditioner
4877 .seealso: SNESSetNPC(), SNESHasNPC()
4878 @*/
4879 PetscErrorCode SNESGetNPC(SNES snes, SNES *pc)
4880 {
4881   PetscErrorCode ierr;
4882   const char     *optionsprefix;
4883 
4884   PetscFunctionBegin;
4885   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4886   PetscValidPointer(pc, 2);
4887   if (!snes->pc) {
4888     ierr = SNESCreate(PetscObjectComm((PetscObject)snes),&snes->pc);CHKERRQ(ierr);
4889     ierr = PetscObjectIncrementTabLevel((PetscObject)snes->pc,(PetscObject)snes,1);CHKERRQ(ierr);
4890     ierr = PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->pc);CHKERRQ(ierr);
4891     ierr = SNESGetOptionsPrefix(snes,&optionsprefix);CHKERRQ(ierr);
4892     ierr = SNESSetOptionsPrefix(snes->pc,optionsprefix);CHKERRQ(ierr);
4893     ierr = SNESAppendOptionsPrefix(snes->pc,"npc_");CHKERRQ(ierr);
4894     ierr = SNESSetCountersReset(snes->pc,PETSC_FALSE);CHKERRQ(ierr);
4895   }
4896   *pc = snes->pc;
4897   PetscFunctionReturn(0);
4898 }
4899 
4900 #undef __FUNCT__
4901 #define __FUNCT__ "SNESHasNPC"
4902 /*@
4903   SNESHasNPC - Returns whether a nonlinear preconditioner exists
4904 
4905   Not Collective
4906 
4907   Input Parameter:
4908 . snes - iterative context obtained from SNESCreate()
4909 
4910   Output Parameter:
4911 . has_npc - whether the SNES has an NPC or not
4912 
4913   Level: developer
4914 
4915 .keywords: SNES, has, preconditioner
4916 .seealso: SNESSetNPC(), SNESGetNPC()
4917 @*/
4918 PetscErrorCode SNESHasNPC(SNES snes, PetscBool *has_npc)
4919 {
4920   PetscFunctionBegin;
4921   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4922   *has_npc = (PetscBool) (snes->pc != NULL);
4923   PetscFunctionReturn(0);
4924 }
4925 
4926 #undef __FUNCT__
4927 #define __FUNCT__ "SNESSetNPCSide"
4928 /*@
4929     SNESSetNPCSide - Sets the preconditioning side.
4930 
4931     Logically Collective on SNES
4932 
4933     Input Parameter:
4934 .   snes - iterative context obtained from SNESCreate()
4935 
4936     Output Parameter:
4937 .   side - the preconditioning side, where side is one of
4938 .vb
4939       PC_LEFT - left preconditioning (default)
4940       PC_RIGHT - right preconditioning
4941 .ve
4942 
4943     Options Database Keys:
4944 .   -snes_pc_side <right,left>
4945 
4946     Level: intermediate
4947 
4948 .keywords: SNES, set, right, left, side, preconditioner, flag
4949 
4950 .seealso: SNESGetNPCSide(), KSPSetPCSide()
4951 @*/
4952 PetscErrorCode  SNESSetNPCSide(SNES snes,PCSide side)
4953 {
4954   PetscFunctionBegin;
4955   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4956   PetscValidLogicalCollectiveEnum(snes,side,2);
4957   snes->pcside = side;
4958   PetscFunctionReturn(0);
4959 }
4960 
4961 #undef __FUNCT__
4962 #define __FUNCT__ "SNESGetNPCSide"
4963 /*@
4964     SNESGetNPCSide - Gets the preconditioning side.
4965 
4966     Not Collective
4967 
4968     Input Parameter:
4969 .   snes - iterative context obtained from SNESCreate()
4970 
4971     Output Parameter:
4972 .   side - the preconditioning side, where side is one of
4973 .vb
4974       PC_LEFT - left preconditioning (default)
4975       PC_RIGHT - right preconditioning
4976 .ve
4977 
4978     Level: intermediate
4979 
4980 .keywords: SNES, get, right, left, side, preconditioner, flag
4981 
4982 .seealso: SNESSetNPCSide(), KSPGetPCSide()
4983 @*/
4984 PetscErrorCode  SNESGetNPCSide(SNES snes,PCSide *side)
4985 {
4986   PetscFunctionBegin;
4987   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4988   PetscValidPointer(side,2);
4989   *side = snes->pcside;
4990   PetscFunctionReturn(0);
4991 }
4992 
4993 #undef __FUNCT__
4994 #define __FUNCT__ "SNESSetLineSearch"
4995 /*@
4996   SNESSetLineSearch - Sets the linesearch on the SNES instance.
4997 
4998   Collective on SNES
4999 
5000   Input Parameters:
5001 + snes - iterative context obtained from SNESCreate()
5002 - linesearch   - the linesearch object
5003 
5004   Notes:
5005   Use SNESGetLineSearch() to retrieve the preconditioner context (for example,
5006   to configure it using the API).
5007 
5008   Level: developer
5009 
5010 .keywords: SNES, set, linesearch
5011 .seealso: SNESGetLineSearch()
5012 @*/
5013 PetscErrorCode SNESSetLineSearch(SNES snes, SNESLineSearch linesearch)
5014 {
5015   PetscErrorCode ierr;
5016 
5017   PetscFunctionBegin;
5018   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
5019   PetscValidHeaderSpecific(linesearch, SNESLINESEARCH_CLASSID, 2);
5020   PetscCheckSameComm(snes, 1, linesearch, 2);
5021   ierr = PetscObjectReference((PetscObject) linesearch);CHKERRQ(ierr);
5022   ierr = SNESLineSearchDestroy(&snes->linesearch);CHKERRQ(ierr);
5023 
5024   snes->linesearch = linesearch;
5025 
5026   ierr = PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->linesearch);CHKERRQ(ierr);
5027   PetscFunctionReturn(0);
5028 }
5029 
5030 #undef __FUNCT__
5031 #define __FUNCT__ "SNESGetLineSearch"
5032 /*@
5033   SNESGetLineSearch - Returns a pointer to the line search context set with SNESSetLineSearch()
5034   or creates a default line search instance associated with the SNES and returns it.
5035 
5036   Not Collective
5037 
5038   Input Parameter:
5039 . snes - iterative context obtained from SNESCreate()
5040 
5041   Output Parameter:
5042 . linesearch - linesearch context
5043 
5044   Level: beginner
5045 
5046 .keywords: SNES, get, linesearch
5047 .seealso: SNESSetLineSearch(), SNESLineSearchCreate()
5048 @*/
5049 PetscErrorCode SNESGetLineSearch(SNES snes, SNESLineSearch *linesearch)
5050 {
5051   PetscErrorCode ierr;
5052   const char     *optionsprefix;
5053 
5054   PetscFunctionBegin;
5055   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
5056   PetscValidPointer(linesearch, 2);
5057   if (!snes->linesearch) {
5058     ierr = SNESGetOptionsPrefix(snes, &optionsprefix);CHKERRQ(ierr);
5059     ierr = SNESLineSearchCreate(PetscObjectComm((PetscObject)snes), &snes->linesearch);CHKERRQ(ierr);
5060     ierr = SNESLineSearchSetSNES(snes->linesearch, snes);CHKERRQ(ierr);
5061     ierr = SNESLineSearchAppendOptionsPrefix(snes->linesearch, optionsprefix);CHKERRQ(ierr);
5062     ierr = PetscObjectIncrementTabLevel((PetscObject) snes->linesearch, (PetscObject) snes, 1);CHKERRQ(ierr);
5063     ierr = PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->linesearch);CHKERRQ(ierr);
5064   }
5065   *linesearch = snes->linesearch;
5066   PetscFunctionReturn(0);
5067 }
5068 
5069 #if defined(PETSC_HAVE_MATLAB_ENGINE)
5070 #include <mex.h>
5071 
5072 typedef struct {char *funcname; mxArray *ctx;} SNESMatlabContext;
5073 
5074 #undef __FUNCT__
5075 #define __FUNCT__ "SNESComputeFunction_Matlab"
5076 /*
5077    SNESComputeFunction_Matlab - Calls the function that has been set with SNESSetFunctionMatlab().
5078 
5079    Collective on SNES
5080 
5081    Input Parameters:
5082 +  snes - the SNES context
5083 -  x - input vector
5084 
5085    Output Parameter:
5086 .  y - function vector, as set by SNESSetFunction()
5087 
5088    Notes:
5089    SNESComputeFunction() is typically used within nonlinear solvers
5090    implementations, so most users would not generally call this routine
5091    themselves.
5092 
5093    Level: developer
5094 
5095 .keywords: SNES, nonlinear, compute, function
5096 
5097 .seealso: SNESSetFunction(), SNESGetFunction()
5098 */
5099 PetscErrorCode  SNESComputeFunction_Matlab(SNES snes,Vec x,Vec y, void *ctx)
5100 {
5101   PetscErrorCode    ierr;
5102   SNESMatlabContext *sctx = (SNESMatlabContext*)ctx;
5103   int               nlhs  = 1,nrhs = 5;
5104   mxArray           *plhs[1],*prhs[5];
5105   long long int     lx = 0,ly = 0,ls = 0;
5106 
5107   PetscFunctionBegin;
5108   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
5109   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
5110   PetscValidHeaderSpecific(y,VEC_CLASSID,3);
5111   PetscCheckSameComm(snes,1,x,2);
5112   PetscCheckSameComm(snes,1,y,3);
5113 
5114   /* call Matlab function in ctx with arguments x and y */
5115 
5116   ierr    = PetscMemcpy(&ls,&snes,sizeof(snes));CHKERRQ(ierr);
5117   ierr    = PetscMemcpy(&lx,&x,sizeof(x));CHKERRQ(ierr);
5118   ierr    = PetscMemcpy(&ly,&y,sizeof(x));CHKERRQ(ierr);
5119   prhs[0] = mxCreateDoubleScalar((double)ls);
5120   prhs[1] = mxCreateDoubleScalar((double)lx);
5121   prhs[2] = mxCreateDoubleScalar((double)ly);
5122   prhs[3] = mxCreateString(sctx->funcname);
5123   prhs[4] = sctx->ctx;
5124   ierr    = mexCallMATLAB(nlhs,plhs,nrhs,prhs,"PetscSNESComputeFunctionInternal");CHKERRQ(ierr);
5125   ierr    = mxGetScalar(plhs[0]);CHKERRQ(ierr);
5126   mxDestroyArray(prhs[0]);
5127   mxDestroyArray(prhs[1]);
5128   mxDestroyArray(prhs[2]);
5129   mxDestroyArray(prhs[3]);
5130   mxDestroyArray(plhs[0]);
5131   PetscFunctionReturn(0);
5132 }
5133 
5134 #undef __FUNCT__
5135 #define __FUNCT__ "SNESSetFunctionMatlab"
5136 /*
5137    SNESSetFunctionMatlab - Sets the function evaluation routine and function
5138    vector for use by the SNES routines in solving systems of nonlinear
5139    equations from MATLAB. Here the function is a string containing the name of a MATLAB function
5140 
5141    Logically Collective on SNES
5142 
5143    Input Parameters:
5144 +  snes - the SNES context
5145 .  r - vector to store function value
5146 -  f - function evaluation routine
5147 
5148    Notes:
5149    The Newton-like methods typically solve linear systems of the form
5150 $      f'(x) x = -f(x),
5151    where f'(x) denotes the Jacobian matrix and f(x) is the function.
5152 
5153    Level: beginner
5154 
5155    Developer Note:  This bleeds the allocated memory SNESMatlabContext *sctx;
5156 
5157 .keywords: SNES, nonlinear, set, function
5158 
5159 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction()
5160 */
5161 PetscErrorCode  SNESSetFunctionMatlab(SNES snes,Vec r,const char *f,mxArray *ctx)
5162 {
5163   PetscErrorCode    ierr;
5164   SNESMatlabContext *sctx;
5165 
5166   PetscFunctionBegin;
5167   /* currently sctx is memory bleed */
5168   ierr = PetscNew(&sctx);CHKERRQ(ierr);
5169   ierr = PetscStrallocpy(f,&sctx->funcname);CHKERRQ(ierr);
5170   /*
5171      This should work, but it doesn't
5172   sctx->ctx = ctx;
5173   mexMakeArrayPersistent(sctx->ctx);
5174   */
5175   sctx->ctx = mxDuplicateArray(ctx);
5176   ierr      = SNESSetFunction(snes,r,SNESComputeFunction_Matlab,sctx);CHKERRQ(ierr);
5177   PetscFunctionReturn(0);
5178 }
5179 
5180 #undef __FUNCT__
5181 #define __FUNCT__ "SNESComputeJacobian_Matlab"
5182 /*
5183    SNESComputeJacobian_Matlab - Calls the function that has been set with SNESSetJacobianMatlab().
5184 
5185    Collective on SNES
5186 
5187    Input Parameters:
5188 +  snes - the SNES context
5189 .  x - input vector
5190 .  A, B - the matrices
5191 -  ctx - user context
5192 
5193    Level: developer
5194 
5195 .keywords: SNES, nonlinear, compute, function
5196 
5197 .seealso: SNESSetFunction(), SNESGetFunction()
5198 @*/
5199 PetscErrorCode  SNESComputeJacobian_Matlab(SNES snes,Vec x,Mat A,Mat B,void *ctx)
5200 {
5201   PetscErrorCode    ierr;
5202   SNESMatlabContext *sctx = (SNESMatlabContext*)ctx;
5203   int               nlhs  = 2,nrhs = 6;
5204   mxArray           *plhs[2],*prhs[6];
5205   long long int     lx = 0,lA = 0,ls = 0, lB = 0;
5206 
5207   PetscFunctionBegin;
5208   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
5209   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
5210 
5211   /* call Matlab function in ctx with arguments x and y */
5212 
5213   ierr    = PetscMemcpy(&ls,&snes,sizeof(snes));CHKERRQ(ierr);
5214   ierr    = PetscMemcpy(&lx,&x,sizeof(x));CHKERRQ(ierr);
5215   ierr    = PetscMemcpy(&lA,A,sizeof(x));CHKERRQ(ierr);
5216   ierr    = PetscMemcpy(&lB,B,sizeof(x));CHKERRQ(ierr);
5217   prhs[0] = mxCreateDoubleScalar((double)ls);
5218   prhs[1] = mxCreateDoubleScalar((double)lx);
5219   prhs[2] = mxCreateDoubleScalar((double)lA);
5220   prhs[3] = mxCreateDoubleScalar((double)lB);
5221   prhs[4] = mxCreateString(sctx->funcname);
5222   prhs[5] = sctx->ctx;
5223   ierr    = mexCallMATLAB(nlhs,plhs,nrhs,prhs,"PetscSNESComputeJacobianInternal");CHKERRQ(ierr);
5224   ierr    = mxGetScalar(plhs[0]);CHKERRQ(ierr);
5225   mxDestroyArray(prhs[0]);
5226   mxDestroyArray(prhs[1]);
5227   mxDestroyArray(prhs[2]);
5228   mxDestroyArray(prhs[3]);
5229   mxDestroyArray(prhs[4]);
5230   mxDestroyArray(plhs[0]);
5231   mxDestroyArray(plhs[1]);
5232   PetscFunctionReturn(0);
5233 }
5234 
5235 #undef __FUNCT__
5236 #define __FUNCT__ "SNESSetJacobianMatlab"
5237 /*
5238    SNESSetJacobianMatlab - Sets the Jacobian function evaluation routine and two empty Jacobian matrices
5239    vector for use by the SNES routines in solving systems of nonlinear
5240    equations from MATLAB. Here the function is a string containing the name of a MATLAB function
5241 
5242    Logically Collective on SNES
5243 
5244    Input Parameters:
5245 +  snes - the SNES context
5246 .  A,B - Jacobian matrices
5247 .  J - function evaluation routine
5248 -  ctx - user context
5249 
5250    Level: developer
5251 
5252    Developer Note:  This bleeds the allocated memory SNESMatlabContext *sctx;
5253 
5254 .keywords: SNES, nonlinear, set, function
5255 
5256 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction(), J
5257 */
5258 PetscErrorCode  SNESSetJacobianMatlab(SNES snes,Mat A,Mat B,const char *J,mxArray *ctx)
5259 {
5260   PetscErrorCode    ierr;
5261   SNESMatlabContext *sctx;
5262 
5263   PetscFunctionBegin;
5264   /* currently sctx is memory bleed */
5265   ierr = PetscNew(&sctx);CHKERRQ(ierr);
5266   ierr = PetscStrallocpy(J,&sctx->funcname);CHKERRQ(ierr);
5267   /*
5268      This should work, but it doesn't
5269   sctx->ctx = ctx;
5270   mexMakeArrayPersistent(sctx->ctx);
5271   */
5272   sctx->ctx = mxDuplicateArray(ctx);
5273   ierr      = SNESSetJacobian(snes,A,B,SNESComputeJacobian_Matlab,sctx);CHKERRQ(ierr);
5274   PetscFunctionReturn(0);
5275 }
5276 
5277 #undef __FUNCT__
5278 #define __FUNCT__ "SNESMonitor_Matlab"
5279 /*
5280    SNESMonitor_Matlab - Calls the function that has been set with SNESMonitorSetMatlab().
5281 
5282    Collective on SNES
5283 
5284 .seealso: SNESSetFunction(), SNESGetFunction()
5285 @*/
5286 PetscErrorCode  SNESMonitor_Matlab(SNES snes,PetscInt it, PetscReal fnorm, void *ctx)
5287 {
5288   PetscErrorCode    ierr;
5289   SNESMatlabContext *sctx = (SNESMatlabContext*)ctx;
5290   int               nlhs  = 1,nrhs = 6;
5291   mxArray           *plhs[1],*prhs[6];
5292   long long int     lx = 0,ls = 0;
5293   Vec               x  = snes->vec_sol;
5294 
5295   PetscFunctionBegin;
5296   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
5297 
5298   ierr    = PetscMemcpy(&ls,&snes,sizeof(snes));CHKERRQ(ierr);
5299   ierr    = PetscMemcpy(&lx,&x,sizeof(x));CHKERRQ(ierr);
5300   prhs[0] = mxCreateDoubleScalar((double)ls);
5301   prhs[1] = mxCreateDoubleScalar((double)it);
5302   prhs[2] = mxCreateDoubleScalar((double)fnorm);
5303   prhs[3] = mxCreateDoubleScalar((double)lx);
5304   prhs[4] = mxCreateString(sctx->funcname);
5305   prhs[5] = sctx->ctx;
5306   ierr    = mexCallMATLAB(nlhs,plhs,nrhs,prhs,"PetscSNESMonitorInternal");CHKERRQ(ierr);
5307   ierr    = mxGetScalar(plhs[0]);CHKERRQ(ierr);
5308   mxDestroyArray(prhs[0]);
5309   mxDestroyArray(prhs[1]);
5310   mxDestroyArray(prhs[2]);
5311   mxDestroyArray(prhs[3]);
5312   mxDestroyArray(prhs[4]);
5313   mxDestroyArray(plhs[0]);
5314   PetscFunctionReturn(0);
5315 }
5316 
5317 #undef __FUNCT__
5318 #define __FUNCT__ "SNESMonitorSetMatlab"
5319 /*
5320    SNESMonitorSetMatlab - Sets the monitor function from MATLAB
5321 
5322    Level: developer
5323 
5324    Developer Note:  This bleeds the allocated memory SNESMatlabContext *sctx;
5325 
5326 .keywords: SNES, nonlinear, set, function
5327 
5328 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction()
5329 */
5330 PetscErrorCode  SNESMonitorSetMatlab(SNES snes,const char *f,mxArray *ctx)
5331 {
5332   PetscErrorCode    ierr;
5333   SNESMatlabContext *sctx;
5334 
5335   PetscFunctionBegin;
5336   /* currently sctx is memory bleed */
5337   ierr = PetscNew(&sctx);CHKERRQ(ierr);
5338   ierr = PetscStrallocpy(f,&sctx->funcname);CHKERRQ(ierr);
5339   /*
5340      This should work, but it doesn't
5341   sctx->ctx = ctx;
5342   mexMakeArrayPersistent(sctx->ctx);
5343   */
5344   sctx->ctx = mxDuplicateArray(ctx);
5345   ierr      = SNESMonitorSet(snes,SNESMonitor_Matlab,sctx,NULL);CHKERRQ(ierr);
5346   PetscFunctionReturn(0);
5347 }
5348 
5349 #endif
5350