xref: /petsc/src/snes/interface/snes.c (revision 460c5f81cfdc5b4c06ddbb0232be5fd33ccb813f)
1 
2 #include <petsc/private/snesimpl.h>      /*I "petscsnes.h"  I*/
3 #include <petscdmshell.h>
4 
5 PetscBool         SNESRegisterAllCalled = PETSC_FALSE;
6 PetscFunctionList SNESList              = NULL;
7 
8 /* Logging support */
9 PetscClassId  SNES_CLASSID, DMSNES_CLASSID;
10 PetscLogEvent SNES_Solve, SNES_FunctionEval, SNES_JacobianEval, SNES_NGSEval, SNES_NGSFuncEval, SNES_NPCSolve;
11 
12 #undef __FUNCT__
13 #define __FUNCT__ "SNESSetErrorIfNotConverged"
14 /*@
15    SNESSetErrorIfNotConverged - Causes SNESSolve() to generate an error if the solver has not converged.
16 
17    Logically Collective on SNES
18 
19    Input Parameters:
20 +  snes - iterative context obtained from SNESCreate()
21 -  flg - PETSC_TRUE indicates you want the error generated
22 
23    Options database keys:
24 .  -snes_error_if_not_converged : this takes an optional truth value (0/1/no/yes/true/false)
25 
26    Level: intermediate
27 
28    Notes:
29     Normally PETSc continues if a linear solver fails to converge, you can call SNESGetConvergedReason() after a SNESSolve()
30     to determine if it has converged.
31 
32 .keywords: SNES, set, initial guess, nonzero
33 
34 .seealso: SNESGetErrorIfNotConverged(), KSPGetErrorIfNotConverged(), KSPSetErrorIFNotConverged()
35 @*/
36 PetscErrorCode  SNESSetErrorIfNotConverged(SNES snes,PetscBool flg)
37 {
38   PetscFunctionBegin;
39   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
40   PetscValidLogicalCollectiveBool(snes,flg,2);
41   snes->errorifnotconverged = flg;
42   PetscFunctionReturn(0);
43 }
44 
45 #undef __FUNCT__
46 #define __FUNCT__ "SNESGetErrorIfNotConverged"
47 /*@
48    SNESGetErrorIfNotConverged - Will SNESSolve() generate an error if the solver does not converge?
49 
50    Not Collective
51 
52    Input Parameter:
53 .  snes - iterative context obtained from SNESCreate()
54 
55    Output Parameter:
56 .  flag - PETSC_TRUE if it will generate an error, else PETSC_FALSE
57 
58    Level: intermediate
59 
60 .keywords: SNES, set, initial guess, nonzero
61 
62 .seealso:  SNESSetErrorIfNotConverged(), KSPGetErrorIfNotConverged(), KSPSetErrorIFNotConverged()
63 @*/
64 PetscErrorCode  SNESGetErrorIfNotConverged(SNES snes,PetscBool  *flag)
65 {
66   PetscFunctionBegin;
67   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
68   PetscValidPointer(flag,2);
69   *flag = snes->errorifnotconverged;
70   PetscFunctionReturn(0);
71 }
72 
73 #undef __FUNCT__
74 #define __FUNCT__ "SNESSetFunctionDomainError"
75 /*@
76    SNESSetFunctionDomainError - tells SNES that the input vector to your SNESFunction is not
77      in the functions domain. For example, negative pressure.
78 
79    Logically Collective on SNES
80 
81    Input Parameters:
82 .  snes - the SNES context
83 
84    Level: advanced
85 
86 .keywords: SNES, view
87 
88 .seealso: SNESCreate(), SNESSetFunction(), SNESFunction
89 @*/
90 PetscErrorCode  SNESSetFunctionDomainError(SNES snes)
91 {
92   PetscFunctionBegin;
93   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
94   snes->domainerror = PETSC_TRUE;
95   PetscFunctionReturn(0);
96 }
97 
98 #undef __FUNCT__
99 #define __FUNCT__ "SNESGetFunctionDomainError"
100 /*@
101    SNESGetFunctionDomainError - Gets the status of the domain error after a call to SNESComputeFunction;
102 
103    Logically Collective on SNES
104 
105    Input Parameters:
106 .  snes - the SNES context
107 
108    Output Parameters:
109 .  domainerror - Set to PETSC_TRUE if there's a domain error; PETSC_FALSE otherwise.
110 
111    Level: advanced
112 
113 .keywords: SNES, view
114 
115 .seealso: SNESSetFunctionDomainError(), SNESComputeFunction()
116 @*/
117 PetscErrorCode  SNESGetFunctionDomainError(SNES snes, PetscBool *domainerror)
118 {
119   PetscFunctionBegin;
120   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
121   PetscValidPointer(domainerror, 2);
122   *domainerror = snes->domainerror;
123   PetscFunctionReturn(0);
124 }
125 
126 #undef __FUNCT__
127 #define __FUNCT__ "SNESLoad"
128 /*@C
129   SNESLoad - Loads a SNES that has been stored in binary  with SNESView().
130 
131   Collective on PetscViewer
132 
133   Input Parameters:
134 + newdm - the newly loaded SNES, this needs to have been created with SNESCreate() or
135            some related function before a call to SNESLoad().
136 - viewer - binary file viewer, obtained from PetscViewerBinaryOpen()
137 
138    Level: intermediate
139 
140   Notes:
141    The type is determined by the data in the file, any type set into the SNES before this call is ignored.
142 
143   Notes for advanced users:
144   Most users should not need to know the details of the binary storage
145   format, since SNESLoad() and TSView() completely hide these details.
146   But for anyone who's interested, the standard binary matrix storage
147   format is
148 .vb
149      has not yet been determined
150 .ve
151 
152 .seealso: PetscViewerBinaryOpen(), SNESView(), MatLoad(), VecLoad()
153 @*/
154 PetscErrorCode  SNESLoad(SNES snes, PetscViewer viewer)
155 {
156   PetscErrorCode ierr;
157   PetscBool      isbinary;
158   PetscInt       classid;
159   char           type[256];
160   KSP            ksp;
161   DM             dm;
162   DMSNES         dmsnes;
163 
164   PetscFunctionBegin;
165   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
166   PetscValidHeaderSpecific(viewer,PETSC_VIEWER_CLASSID,2);
167   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);CHKERRQ(ierr);
168   if (!isbinary) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONG,"Invalid viewer; open viewer with PetscViewerBinaryOpen()");
169 
170   ierr = PetscViewerBinaryRead(viewer,&classid,1,NULL,PETSC_INT);CHKERRQ(ierr);
171   if (classid != SNES_FILE_CLASSID) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_WRONG,"Not SNES next in file");
172   ierr = PetscViewerBinaryRead(viewer,type,256,NULL,PETSC_CHAR);CHKERRQ(ierr);
173   ierr = SNESSetType(snes, type);CHKERRQ(ierr);
174   if (snes->ops->load) {
175     ierr = (*snes->ops->load)(snes,viewer);CHKERRQ(ierr);
176   }
177   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
178   ierr = DMGetDMSNES(dm,&dmsnes);CHKERRQ(ierr);
179   ierr = DMSNESLoad(dmsnes,viewer);CHKERRQ(ierr);
180   ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
181   ierr = KSPLoad(ksp,viewer);CHKERRQ(ierr);
182   PetscFunctionReturn(0);
183 }
184 
185 #include <petscdraw.h>
186 #if defined(PETSC_HAVE_SAWS)
187 #include <petscviewersaws.h>
188 #endif
189 #undef __FUNCT__
190 #define __FUNCT__ "SNESView"
191 /*@C
192    SNESView - Prints the SNES data structure.
193 
194    Collective on SNES
195 
196    Input Parameters:
197 +  SNES - the SNES context
198 -  viewer - visualization context
199 
200    Options Database Key:
201 .  -snes_view - Calls SNESView() at end of SNESSolve()
202 
203    Notes:
204    The available visualization contexts include
205 +     PETSC_VIEWER_STDOUT_SELF - standard output (default)
206 -     PETSC_VIEWER_STDOUT_WORLD - synchronized standard
207          output where only the first processor opens
208          the file.  All other processors send their
209          data to the first processor to print.
210 
211    The user can open an alternative visualization context with
212    PetscViewerASCIIOpen() - output to a specified file.
213 
214    Level: beginner
215 
216 .keywords: SNES, view
217 
218 .seealso: PetscViewerASCIIOpen()
219 @*/
220 PetscErrorCode  SNESView(SNES snes,PetscViewer viewer)
221 {
222   SNESKSPEW      *kctx;
223   PetscErrorCode ierr;
224   KSP            ksp;
225   SNESLineSearch linesearch;
226   PetscBool      iascii,isstring,isbinary,isdraw;
227   DMSNES         dmsnes;
228 #if defined(PETSC_HAVE_SAWS)
229   PetscBool      issaws;
230 #endif
231 
232   PetscFunctionBegin;
233   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
234   if (!viewer) {
235     ierr = PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&viewer);CHKERRQ(ierr);
236   }
237   PetscValidHeaderSpecific(viewer,PETSC_VIEWER_CLASSID,2);
238   PetscCheckSameComm(snes,1,viewer,2);
239 
240   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&iascii);CHKERRQ(ierr);
241   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSTRING,&isstring);CHKERRQ(ierr);
242   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERBINARY,&isbinary);CHKERRQ(ierr);
243   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERDRAW,&isdraw);CHKERRQ(ierr);
244 #if defined(PETSC_HAVE_SAWS)
245   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERSAWS,&issaws);CHKERRQ(ierr);
246 #endif
247   if (iascii) {
248     SNESNormSchedule normschedule;
249 
250     ierr = PetscObjectPrintClassNamePrefixType((PetscObject)snes,viewer);CHKERRQ(ierr);
251     if (!snes->setupcalled) {
252       ierr = PetscViewerASCIIPrintf(viewer,"  SNES has not been set up so information may be incomplete\n");CHKERRQ(ierr);
253     }
254     if (snes->ops->view) {
255       ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
256       ierr = (*snes->ops->view)(snes,viewer);CHKERRQ(ierr);
257       ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
258     }
259     ierr = PetscViewerASCIIPrintf(viewer,"  maximum iterations=%D, maximum function evaluations=%D\n",snes->max_its,snes->max_funcs);CHKERRQ(ierr);
260     ierr = PetscViewerASCIIPrintf(viewer,"  tolerances: relative=%g, absolute=%g, solution=%g\n",(double)snes->rtol,(double)snes->abstol,(double)snes->stol);CHKERRQ(ierr);
261     ierr = PetscViewerASCIIPrintf(viewer,"  total number of linear solver iterations=%D\n",snes->linear_its);CHKERRQ(ierr);
262     ierr = PetscViewerASCIIPrintf(viewer,"  total number of function evaluations=%D\n",snes->nfuncs);CHKERRQ(ierr);
263     ierr = SNESGetNormSchedule(snes, &normschedule);CHKERRQ(ierr);
264     if (normschedule > 0) {ierr = PetscViewerASCIIPrintf(viewer,"  norm schedule %s\n",SNESNormSchedules[normschedule]);CHKERRQ(ierr);}
265     if (snes->gridsequence) {
266       ierr = PetscViewerASCIIPrintf(viewer,"  total number of grid sequence refinements=%D\n",snes->gridsequence);CHKERRQ(ierr);
267     }
268     if (snes->ksp_ewconv) {
269       kctx = (SNESKSPEW*)snes->kspconvctx;
270       if (kctx) {
271         ierr = PetscViewerASCIIPrintf(viewer,"  Eisenstat-Walker computation of KSP relative tolerance (version %D)\n",kctx->version);CHKERRQ(ierr);
272         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);
273         ierr = PetscViewerASCIIPrintf(viewer,"    gamma=%g, alpha=%g, alpha2=%g\n",(double)kctx->gamma,(double)kctx->alpha,(double)kctx->alpha2);CHKERRQ(ierr);
274       }
275     }
276     if (snes->lagpreconditioner == -1) {
277       ierr = PetscViewerASCIIPrintf(viewer,"  Preconditioned is never rebuilt\n");CHKERRQ(ierr);
278     } else if (snes->lagpreconditioner > 1) {
279       ierr = PetscViewerASCIIPrintf(viewer,"  Preconditioned is rebuilt every %D new Jacobians\n",snes->lagpreconditioner);CHKERRQ(ierr);
280     }
281     if (snes->lagjacobian == -1) {
282       ierr = PetscViewerASCIIPrintf(viewer,"  Jacobian is never rebuilt\n");CHKERRQ(ierr);
283     } else if (snes->lagjacobian > 1) {
284       ierr = PetscViewerASCIIPrintf(viewer,"  Jacobian is rebuilt every %D SNES iterations\n",snes->lagjacobian);CHKERRQ(ierr);
285     }
286   } else if (isstring) {
287     const char *type;
288     ierr = SNESGetType(snes,&type);CHKERRQ(ierr);
289     ierr = PetscViewerStringSPrintf(viewer," %-3.3s",type);CHKERRQ(ierr);
290   } else if (isbinary) {
291     PetscInt    classid = SNES_FILE_CLASSID;
292     MPI_Comm    comm;
293     PetscMPIInt rank;
294     char        type[256];
295 
296     ierr = PetscObjectGetComm((PetscObject)snes,&comm);CHKERRQ(ierr);
297     ierr = MPI_Comm_rank(comm,&rank);CHKERRQ(ierr);
298     if (!rank) {
299       ierr = PetscViewerBinaryWrite(viewer,&classid,1,PETSC_INT,PETSC_FALSE);CHKERRQ(ierr);
300       ierr = PetscStrncpy(type,((PetscObject)snes)->type_name,sizeof(type));CHKERRQ(ierr);
301       ierr = PetscViewerBinaryWrite(viewer,type,sizeof(type),PETSC_CHAR,PETSC_FALSE);CHKERRQ(ierr);
302     }
303     if (snes->ops->view) {
304       ierr = (*snes->ops->view)(snes,viewer);CHKERRQ(ierr);
305     }
306   } else if (isdraw) {
307     PetscDraw draw;
308     char      str[36];
309     PetscReal x,y,bottom,h;
310 
311     ierr   = PetscViewerDrawGetDraw(viewer,0,&draw);CHKERRQ(ierr);
312     ierr   = PetscDrawGetCurrentPoint(draw,&x,&y);CHKERRQ(ierr);
313     ierr   = PetscStrcpy(str,"SNES: ");CHKERRQ(ierr);
314     ierr   = PetscStrcat(str,((PetscObject)snes)->type_name);CHKERRQ(ierr);
315     ierr   = PetscDrawStringBoxed(draw,x,y,PETSC_DRAW_BLUE,PETSC_DRAW_BLACK,str,NULL,&h);CHKERRQ(ierr);
316     bottom = y - h;
317     ierr   = PetscDrawPushCurrentPoint(draw,x,bottom);CHKERRQ(ierr);
318     if (snes->ops->view) {
319       ierr = (*snes->ops->view)(snes,viewer);CHKERRQ(ierr);
320     }
321 #if defined(PETSC_HAVE_SAWS)
322   } else if (issaws) {
323     PetscMPIInt rank;
324     const char *name;
325 
326     ierr = PetscObjectGetName((PetscObject)snes,&name);CHKERRQ(ierr);
327     ierr = MPI_Comm_rank(PETSC_COMM_WORLD,&rank);CHKERRQ(ierr);
328     if (!((PetscObject)snes)->amsmem && !rank) {
329       char       dir[1024];
330 
331       ierr = PetscObjectViewSAWs((PetscObject)snes,viewer);CHKERRQ(ierr);
332       ierr = PetscSNPrintf(dir,1024,"/PETSc/Objects/%s/its",name);CHKERRQ(ierr);
333       PetscStackCallSAWs(SAWs_Register,(dir,&snes->iter,1,SAWs_READ,SAWs_INT));
334       if (!snes->conv_hist) {
335         ierr = SNESSetConvergenceHistory(snes,NULL,NULL,PETSC_DECIDE,PETSC_TRUE);CHKERRQ(ierr);
336       }
337       ierr = PetscSNPrintf(dir,1024,"/PETSc/Objects/%s/conv_hist",name);CHKERRQ(ierr);
338       PetscStackCallSAWs(SAWs_Register,(dir,snes->conv_hist,10,SAWs_READ,SAWs_DOUBLE));
339     }
340 #endif
341   }
342   if (snes->linesearch) {
343     ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
344     ierr = SNESGetLineSearch(snes, &linesearch);CHKERRQ(ierr);
345     ierr = SNESLineSearchView(linesearch, viewer);CHKERRQ(ierr);
346     ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
347   }
348   if (snes->pc && snes->usespc) {
349     ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
350     ierr = SNESView(snes->pc, viewer);CHKERRQ(ierr);
351     ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
352   }
353   ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
354   ierr = DMGetDMSNES(snes->dm,&dmsnes);CHKERRQ(ierr);
355   ierr = DMSNESView(dmsnes, viewer);CHKERRQ(ierr);
356   ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
357   if (snes->usesksp) {
358     ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
359     ierr = PetscViewerASCIIPushTab(viewer);CHKERRQ(ierr);
360     ierr = KSPView(ksp,viewer);CHKERRQ(ierr);
361     ierr = PetscViewerASCIIPopTab(viewer);CHKERRQ(ierr);
362   }
363   if (isdraw) {
364     PetscDraw draw;
365     ierr = PetscViewerDrawGetDraw(viewer,0,&draw);CHKERRQ(ierr);
366     ierr = PetscDrawPopCurrentPoint(draw);CHKERRQ(ierr);
367   }
368   PetscFunctionReturn(0);
369 }
370 
371 /*
372   We retain a list of functions that also take SNES command
373   line options. These are called at the end SNESSetFromOptions()
374 */
375 #define MAXSETFROMOPTIONS 5
376 static PetscInt numberofsetfromoptions;
377 static PetscErrorCode (*othersetfromoptions[MAXSETFROMOPTIONS])(SNES);
378 
379 #undef __FUNCT__
380 #define __FUNCT__ "SNESAddOptionsChecker"
381 /*@C
382   SNESAddOptionsChecker - Adds an additional function to check for SNES options.
383 
384   Not Collective
385 
386   Input Parameter:
387 . snescheck - function that checks for options
388 
389   Level: developer
390 
391 .seealso: SNESSetFromOptions()
392 @*/
393 PetscErrorCode  SNESAddOptionsChecker(PetscErrorCode (*snescheck)(SNES))
394 {
395   PetscFunctionBegin;
396   if (numberofsetfromoptions >= MAXSETFROMOPTIONS) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE, "Too many options checkers, only %D allowed", MAXSETFROMOPTIONS);
397   othersetfromoptions[numberofsetfromoptions++] = snescheck;
398   PetscFunctionReturn(0);
399 }
400 
401 extern PetscErrorCode  SNESDefaultMatrixFreeCreate2(SNES,Vec,Mat*);
402 
403 #undef __FUNCT__
404 #define __FUNCT__ "SNESSetUpMatrixFree_Private"
405 static PetscErrorCode SNESSetUpMatrixFree_Private(SNES snes, PetscBool hasOperator, PetscInt version)
406 {
407   Mat            J;
408   KSP            ksp;
409   PC             pc;
410   PetscBool      match;
411   PetscErrorCode ierr;
412 
413   PetscFunctionBegin;
414   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
415 
416   if (!snes->vec_func && (snes->jacobian || snes->jacobian_pre)) {
417     Mat A = snes->jacobian, B = snes->jacobian_pre;
418     ierr = MatCreateVecs(A ? A : B, NULL,&snes->vec_func);CHKERRQ(ierr);
419   }
420 
421   if (version == 1) {
422     ierr = MatCreateSNESMF(snes,&J);CHKERRQ(ierr);
423     ierr = MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);CHKERRQ(ierr);
424     ierr = MatSetFromOptions(J);CHKERRQ(ierr);
425   } else if (version == 2) {
426     if (!snes->vec_func) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"SNESSetFunction() must be called first");
427 #if !defined(PETSC_USE_COMPLEX) && !defined(PETSC_USE_REAL_SINGLE) && !defined(PETSC_USE_REAL___FLOAT128)
428     ierr = SNESDefaultMatrixFreeCreate2(snes,snes->vec_func,&J);CHKERRQ(ierr);
429 #else
430     SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP, "matrix-free operator rutines (version 2)");
431 #endif
432   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE, "matrix-free operator rutines, only version 1 and 2");
433 
434   ierr = PetscInfo1(snes,"Setting default matrix-free operator routines (version %D)\n", version);CHKERRQ(ierr);
435   if (hasOperator) {
436 
437     /* This version replaces the user provided Jacobian matrix with a
438        matrix-free version but still employs the user-provided preconditioner matrix. */
439     ierr = SNESSetJacobian(snes,J,0,0,0);CHKERRQ(ierr);
440   } else {
441     /* This version replaces both the user-provided Jacobian and the user-
442      provided preconditioner Jacobian with the default matrix free version. */
443     if ((snes->pcside == PC_LEFT) && snes->pc) {
444       if (!snes->jacobian){ierr = SNESSetJacobian(snes,J,0,0,0);CHKERRQ(ierr);}
445     } else {
446       ierr = SNESSetJacobian(snes,J,J,MatMFFDComputeJacobian,0);CHKERRQ(ierr);
447     }
448     /* Force no preconditioner */
449     ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
450     ierr = KSPGetPC(ksp,&pc);CHKERRQ(ierr);
451     ierr = PetscObjectTypeCompare((PetscObject)pc,PCSHELL,&match);CHKERRQ(ierr);
452     if (!match) {
453       ierr = PetscInfo(snes,"Setting default matrix-free preconditioner routines\nThat is no preconditioner is being used\n");CHKERRQ(ierr);
454       ierr = PCSetType(pc,PCNONE);CHKERRQ(ierr);
455     }
456   }
457   ierr = MatDestroy(&J);CHKERRQ(ierr);
458   PetscFunctionReturn(0);
459 }
460 
461 #undef __FUNCT__
462 #define __FUNCT__ "DMRestrictHook_SNESVecSol"
463 static PetscErrorCode DMRestrictHook_SNESVecSol(DM dmfine,Mat Restrict,Vec Rscale,Mat Inject,DM dmcoarse,void *ctx)
464 {
465   SNES           snes = (SNES)ctx;
466   PetscErrorCode ierr;
467   Vec            Xfine,Xfine_named = NULL,Xcoarse;
468 
469   PetscFunctionBegin;
470   if (PetscLogPrintInfo) {
471     PetscInt finelevel,coarselevel,fineclevel,coarseclevel;
472     ierr = DMGetRefineLevel(dmfine,&finelevel);CHKERRQ(ierr);
473     ierr = DMGetCoarsenLevel(dmfine,&fineclevel);CHKERRQ(ierr);
474     ierr = DMGetRefineLevel(dmcoarse,&coarselevel);CHKERRQ(ierr);
475     ierr = DMGetCoarsenLevel(dmcoarse,&coarseclevel);CHKERRQ(ierr);
476     ierr = PetscInfo4(dmfine,"Restricting SNES solution vector from level %D-%D to level %D-%D\n",finelevel,fineclevel,coarselevel,coarseclevel);CHKERRQ(ierr);
477   }
478   if (dmfine == snes->dm) Xfine = snes->vec_sol;
479   else {
480     ierr  = DMGetNamedGlobalVector(dmfine,"SNESVecSol",&Xfine_named);CHKERRQ(ierr);
481     Xfine = Xfine_named;
482   }
483   ierr = DMGetNamedGlobalVector(dmcoarse,"SNESVecSol",&Xcoarse);CHKERRQ(ierr);
484   if (Inject) {
485     ierr = MatRestrict(Inject,Xfine,Xcoarse);CHKERRQ(ierr);
486   } else {
487     ierr = MatRestrict(Restrict,Xfine,Xcoarse);CHKERRQ(ierr);
488     ierr = VecPointwiseMult(Xcoarse,Xcoarse,Rscale);CHKERRQ(ierr);
489   }
490   ierr = DMRestoreNamedGlobalVector(dmcoarse,"SNESVecSol",&Xcoarse);CHKERRQ(ierr);
491   if (Xfine_named) {ierr = DMRestoreNamedGlobalVector(dmfine,"SNESVecSol",&Xfine_named);CHKERRQ(ierr);}
492   PetscFunctionReturn(0);
493 }
494 
495 #undef __FUNCT__
496 #define __FUNCT__ "DMCoarsenHook_SNESVecSol"
497 static PetscErrorCode DMCoarsenHook_SNESVecSol(DM dm,DM dmc,void *ctx)
498 {
499   PetscErrorCode ierr;
500 
501   PetscFunctionBegin;
502   ierr = DMCoarsenHookAdd(dmc,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,ctx);CHKERRQ(ierr);
503   PetscFunctionReturn(0);
504 }
505 
506 #undef __FUNCT__
507 #define __FUNCT__ "KSPComputeOperators_SNES"
508 /* This may be called to rediscretize the operator on levels of linear multigrid. The DM shuffle is so the user can
509  * safely call SNESGetDM() in their residual evaluation routine. */
510 static PetscErrorCode KSPComputeOperators_SNES(KSP ksp,Mat A,Mat B,void *ctx)
511 {
512   SNES           snes = (SNES)ctx;
513   PetscErrorCode ierr;
514   Mat            Asave = A,Bsave = B;
515   Vec            X,Xnamed = NULL;
516   DM             dmsave;
517   void           *ctxsave;
518   PetscErrorCode (*jac)(SNES,Vec,Mat,Mat,void*);
519 
520   PetscFunctionBegin;
521   dmsave = snes->dm;
522   ierr   = KSPGetDM(ksp,&snes->dm);CHKERRQ(ierr);
523   if (dmsave == snes->dm) X = snes->vec_sol; /* We are on the finest level */
524   else {                                     /* We are on a coarser level, this vec was initialized using a DM restrict hook */
525     ierr = DMGetNamedGlobalVector(snes->dm,"SNESVecSol",&Xnamed);CHKERRQ(ierr);
526     X    = Xnamed;
527     ierr = SNESGetJacobian(snes,NULL,NULL,&jac,&ctxsave);CHKERRQ(ierr);
528     /* If the DM's don't match up, the MatFDColoring context needed for the jacobian won't match up either -- fixit. */
529     if (jac == SNESComputeJacobianDefaultColor) {
530       ierr = SNESSetJacobian(snes,NULL,NULL,SNESComputeJacobianDefaultColor,0);CHKERRQ(ierr);
531     }
532   }
533   /* put the previous context back */
534 
535   ierr = SNESComputeJacobian(snes,X,A,B);CHKERRQ(ierr);
536   if (snes->dm != dmsave && jac == SNESComputeJacobianDefaultColor) {
537     ierr = SNESSetJacobian(snes,NULL,NULL,jac,ctxsave);CHKERRQ(ierr);
538   }
539 
540   if (A != Asave || B != Bsave) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_SUP,"No support for changing matrices at this time");
541   if (Xnamed) {
542     ierr = DMRestoreNamedGlobalVector(snes->dm,"SNESVecSol",&Xnamed);CHKERRQ(ierr);
543   }
544   snes->dm = dmsave;
545   PetscFunctionReturn(0);
546 }
547 
548 #undef __FUNCT__
549 #define __FUNCT__ "SNESSetUpMatrices"
550 /*@
551    SNESSetUpMatrices - ensures that matrices are available for SNES, to be called by SNESSetUp_XXX()
552 
553    Collective
554 
555    Input Arguments:
556 .  snes - snes to configure
557 
558    Level: developer
559 
560 .seealso: SNESSetUp()
561 @*/
562 PetscErrorCode SNESSetUpMatrices(SNES snes)
563 {
564   PetscErrorCode ierr;
565   DM             dm;
566   DMSNES         sdm;
567 
568   PetscFunctionBegin;
569   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
570   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
571   if (!sdm->ops->computejacobian) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_PLIB,"DMSNES not properly configured");
572   else if (!snes->jacobian && snes->mf) {
573     Mat  J;
574     void *functx;
575     ierr = MatCreateSNESMF(snes,&J);CHKERRQ(ierr);
576     ierr = MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);CHKERRQ(ierr);
577     ierr = MatSetFromOptions(J);CHKERRQ(ierr);
578     ierr = SNESGetFunction(snes,NULL,NULL,&functx);CHKERRQ(ierr);
579     ierr = SNESSetJacobian(snes,J,J,0,0);CHKERRQ(ierr);
580     ierr = MatDestroy(&J);CHKERRQ(ierr);
581   } else if (snes->mf_operator && !snes->jacobian_pre && !snes->jacobian) {
582     Mat J,B;
583     ierr = MatCreateSNESMF(snes,&J);CHKERRQ(ierr);
584     ierr = MatMFFDSetOptionsPrefix(J,((PetscObject)snes)->prefix);CHKERRQ(ierr);
585     ierr = MatSetFromOptions(J);CHKERRQ(ierr);
586     ierr = DMCreateMatrix(snes->dm,&B);CHKERRQ(ierr);
587     /* sdm->computejacobian was already set to reach here */
588     ierr = SNESSetJacobian(snes,J,B,NULL,NULL);CHKERRQ(ierr);
589     ierr = MatDestroy(&J);CHKERRQ(ierr);
590     ierr = MatDestroy(&B);CHKERRQ(ierr);
591   } else if (!snes->jacobian_pre) {
592     Mat J,B;
593     J    = snes->jacobian;
594     ierr = DMCreateMatrix(snes->dm,&B);CHKERRQ(ierr);
595     ierr = SNESSetJacobian(snes,J ? J : B,B,NULL,NULL);CHKERRQ(ierr);
596     ierr = MatDestroy(&B);CHKERRQ(ierr);
597   }
598   {
599     KSP ksp;
600     ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
601     ierr = KSPSetComputeOperators(ksp,KSPComputeOperators_SNES,snes);CHKERRQ(ierr);
602     ierr = DMCoarsenHookAdd(snes->dm,DMCoarsenHook_SNESVecSol,DMRestrictHook_SNESVecSol,snes);CHKERRQ(ierr);
603   }
604   PetscFunctionReturn(0);
605 }
606 
607 #undef __FUNCT__
608 #define __FUNCT__ "SNESSetFromOptions"
609 /*@
610    SNESSetFromOptions - Sets various SNES and KSP parameters from user options.
611 
612    Collective on SNES
613 
614    Input Parameter:
615 .  snes - the SNES context
616 
617    Options Database Keys:
618 +  -snes_type <type> - newtonls, newtontr, ngmres, ncg, nrichardson, qn, vi, fas, SNESType for complete list
619 .  -snes_stol - convergence tolerance in terms of the norm
620                 of the change in the solution between steps
621 .  -snes_atol <abstol> - absolute tolerance of residual norm
622 .  -snes_rtol <rtol> - relative decrease in tolerance norm from initial
623 .  -snes_max_it <max_it> - maximum number of iterations
624 .  -snes_max_funcs <max_funcs> - maximum number of function evaluations
625 .  -snes_max_fail <max_fail> - maximum number of line search failures allowed before stopping, default is none
626 .  -snes_max_linear_solve_fail - number of linear solver failures before SNESSolve() stops
627 .  -snes_lag_preconditioner <lag> - how often preconditioner is rebuilt (use -1 to never rebuild)
628 .  -snes_lag_jacobian <lag> - how often Jacobian is rebuilt (use -1 to never rebuild)
629 .  -snes_trtol <trtol> - trust region tolerance
630 .  -snes_no_convergence_test - skip convergence test in nonlinear
631                                solver; hence iterations will continue until max_it
632                                or some other criterion is reached. Saves expense
633                                of convergence test
634 .  -snes_monitor <optional filename> - prints residual norm at each iteration. if no
635                                        filename given prints to stdout
636 .  -snes_monitor_solution - plots solution at each iteration
637 .  -snes_monitor_residual - plots residual (not its norm) at each iteration
638 .  -snes_monitor_solution_update - plots update to solution at each iteration
639 .  -snes_monitor_lg_residualnorm - plots residual norm at each iteration
640 .  -snes_monitor_lg_range - plots residual norm at each iteration
641 .  -snes_fd - use finite differences to compute Jacobian; very slow, only for testing
642 .  -snes_fd_color - use finite differences with coloring to compute Jacobian
643 .  -snes_mf_ksp_monitor - if using matrix-free multiply then print h at each KSP iteration
644 -  -snes_converged_reason - print the reason for convergence/divergence after each solve
645 
646     Options Database for Eisenstat-Walker method:
647 +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
648 .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
649 .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
650 .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
651 .  -snes_ksp_ew_gamma <gamma> - Sets gamma
652 .  -snes_ksp_ew_alpha <alpha> - Sets alpha
653 .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
654 -  -snes_ksp_ew_threshold <threshold> - Sets threshold
655 
656    Notes:
657    To see all options, run your program with the -help option or consult
658    Users-Manual: ch_snes
659 
660    Level: beginner
661 
662 .keywords: SNES, nonlinear, set, options, database
663 
664 .seealso: SNESSetOptionsPrefix()
665 @*/
666 PetscErrorCode  SNESSetFromOptions(SNES snes)
667 {
668   PetscBool      flg,pcset,persist,set;
669   PetscInt       i,indx,lag,grids;
670   const char     *deft        = SNESNEWTONLS;
671   const char     *convtests[] = {"default","skip"};
672   SNESKSPEW      *kctx        = NULL;
673   char           type[256], monfilename[PETSC_MAX_PATH_LEN];
674   PetscViewer    monviewer;
675   PetscErrorCode ierr;
676   PCSide         pcside;
677   const char     *optionsprefix;
678 
679   PetscFunctionBegin;
680   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
681   ierr = SNESRegisterAll();CHKERRQ(ierr);
682   ierr = PetscObjectOptionsBegin((PetscObject)snes);CHKERRQ(ierr);
683   if (((PetscObject)snes)->type_name) deft = ((PetscObject)snes)->type_name;
684   ierr = PetscOptionsFList("-snes_type","Nonlinear solver method","SNESSetType",SNESList,deft,type,256,&flg);CHKERRQ(ierr);
685   if (flg) {
686     ierr = SNESSetType(snes,type);CHKERRQ(ierr);
687   } else if (!((PetscObject)snes)->type_name) {
688     ierr = SNESSetType(snes,deft);CHKERRQ(ierr);
689   }
690   ierr = PetscOptionsReal("-snes_stol","Stop if step length less than","SNESSetTolerances",snes->stol,&snes->stol,NULL);CHKERRQ(ierr);
691   ierr = PetscOptionsReal("-snes_atol","Stop if function norm less than","SNESSetTolerances",snes->abstol,&snes->abstol,NULL);CHKERRQ(ierr);
692 
693   ierr = PetscOptionsReal("-snes_rtol","Stop if decrease in function norm less than","SNESSetTolerances",snes->rtol,&snes->rtol,NULL);CHKERRQ(ierr);
694   ierr = PetscOptionsInt("-snes_max_it","Maximum iterations","SNESSetTolerances",snes->max_its,&snes->max_its,NULL);CHKERRQ(ierr);
695   ierr = PetscOptionsInt("-snes_max_funcs","Maximum function evaluations","SNESSetTolerances",snes->max_funcs,&snes->max_funcs,NULL);CHKERRQ(ierr);
696   ierr = PetscOptionsInt("-snes_max_fail","Maximum nonlinear step failures","SNESSetMaxNonlinearStepFailures",snes->maxFailures,&snes->maxFailures,NULL);CHKERRQ(ierr);
697   ierr = PetscOptionsInt("-snes_max_linear_solve_fail","Maximum failures in linear solves allowed","SNESSetMaxLinearSolveFailures",snes->maxLinearSolveFailures,&snes->maxLinearSolveFailures,NULL);CHKERRQ(ierr);
698   ierr = PetscOptionsBool("-snes_error_if_not_converged","Generate error if solver does not converge","SNESSetErrorIfNotConverged",snes->errorifnotconverged,&snes->errorifnotconverged,NULL);CHKERRQ(ierr);
699 
700   ierr = PetscOptionsInt("-snes_lag_preconditioner","How often to rebuild preconditioner","SNESSetLagPreconditioner",snes->lagpreconditioner,&lag,&flg);CHKERRQ(ierr);
701   if (flg) {
702     ierr = SNESSetLagPreconditioner(snes,lag);CHKERRQ(ierr);
703   }
704   ierr = PetscOptionsBool("-snes_lag_preconditioner_persists","Preconditioner lagging through multiple solves","SNESSetLagPreconditionerPersists",snes->lagjac_persist,&persist,&flg);CHKERRQ(ierr);
705   if (flg) {
706     ierr = SNESSetLagPreconditionerPersists(snes,persist);CHKERRQ(ierr);
707   }
708   ierr = PetscOptionsInt("-snes_lag_jacobian","How often to rebuild Jacobian","SNESSetLagJacobian",snes->lagjacobian,&lag,&flg);CHKERRQ(ierr);
709   if (flg) {
710     ierr = SNESSetLagJacobian(snes,lag);CHKERRQ(ierr);
711   }
712   ierr = PetscOptionsBool("-snes_lag_jacobian_persists","Jacobian lagging through multiple solves","SNESSetLagJacobianPersists",snes->lagjac_persist,&persist,&flg);CHKERRQ(ierr);
713   if (flg) {
714     ierr = SNESSetLagJacobianPersists(snes,persist);CHKERRQ(ierr);
715   }
716 
717   ierr = PetscOptionsInt("-snes_grid_sequence","Use grid sequencing to generate initial guess","SNESSetGridSequence",snes->gridsequence,&grids,&flg);CHKERRQ(ierr);
718   if (flg) {
719     ierr = SNESSetGridSequence(snes,grids);CHKERRQ(ierr);
720   }
721 
722   ierr = PetscOptionsEList("-snes_convergence_test","Convergence test","SNESSetConvergenceTest",convtests,2,"default",&indx,&flg);CHKERRQ(ierr);
723   if (flg) {
724     switch (indx) {
725     case 0: ierr = SNESSetConvergenceTest(snes,SNESConvergedDefault,NULL,NULL);CHKERRQ(ierr); break;
726     case 1: ierr = SNESSetConvergenceTest(snes,SNESConvergedSkip,NULL,NULL);CHKERRQ(ierr);    break;
727     }
728   }
729 
730   ierr = PetscOptionsEList("-snes_norm_schedule","SNES Norm schedule","SNESSetNormSchedule",SNESNormSchedules,5,"function",&indx,&flg);CHKERRQ(ierr);
731   if (flg) { ierr = SNESSetNormSchedule(snes,(SNESNormSchedule)indx);CHKERRQ(ierr); }
732 
733   ierr = PetscOptionsEList("-snes_function_type","SNES Norm schedule","SNESSetFunctionType",SNESFunctionTypes,2,"unpreconditioned",&indx,&flg);CHKERRQ(ierr);
734   if (flg) { ierr = SNESSetFunctionType(snes,(SNESFunctionType)indx);CHKERRQ(ierr); }
735 
736   kctx = (SNESKSPEW*)snes->kspconvctx;
737 
738   ierr = PetscOptionsBool("-snes_ksp_ew","Use Eisentat-Walker linear system convergence test","SNESKSPSetUseEW",snes->ksp_ewconv,&snes->ksp_ewconv,NULL);CHKERRQ(ierr);
739 
740   ierr = PetscOptionsInt("-snes_ksp_ew_version","Version 1, 2 or 3","SNESKSPSetParametersEW",kctx->version,&kctx->version,NULL);CHKERRQ(ierr);
741   ierr = PetscOptionsReal("-snes_ksp_ew_rtol0","0 <= rtol0 < 1","SNESKSPSetParametersEW",kctx->rtol_0,&kctx->rtol_0,NULL);CHKERRQ(ierr);
742   ierr = PetscOptionsReal("-snes_ksp_ew_rtolmax","0 <= rtolmax < 1","SNESKSPSetParametersEW",kctx->rtol_max,&kctx->rtol_max,NULL);CHKERRQ(ierr);
743   ierr = PetscOptionsReal("-snes_ksp_ew_gamma","0 <= gamma <= 1","SNESKSPSetParametersEW",kctx->gamma,&kctx->gamma,NULL);CHKERRQ(ierr);
744   ierr = PetscOptionsReal("-snes_ksp_ew_alpha","1 < alpha <= 2","SNESKSPSetParametersEW",kctx->alpha,&kctx->alpha,NULL);CHKERRQ(ierr);
745   ierr = PetscOptionsReal("-snes_ksp_ew_alpha2","alpha2","SNESKSPSetParametersEW",kctx->alpha2,&kctx->alpha2,NULL);CHKERRQ(ierr);
746   ierr = PetscOptionsReal("-snes_ksp_ew_threshold","0 < threshold < 1","SNESKSPSetParametersEW",kctx->threshold,&kctx->threshold,NULL);CHKERRQ(ierr);
747 
748   flg  = PETSC_FALSE;
749   ierr = PetscOptionsBool("-snes_check_jacobian","Check each Jacobian with a differenced one","SNESUpdateCheckJacobian",flg,&flg,&set);CHKERRQ(ierr);
750   if (set && flg) {
751     ierr = SNESSetUpdate(snes,SNESUpdateCheckJacobian);CHKERRQ(ierr);
752   }
753 
754   flg  = PETSC_FALSE;
755   ierr = PetscOptionsBool("-snes_monitor_cancel","Remove all monitors","SNESMonitorCancel",flg,&flg,&set);CHKERRQ(ierr);
756   if (set && flg) {ierr = SNESMonitorCancel(snes);CHKERRQ(ierr);}
757 
758   ierr = PetscOptionsString("-snes_monitor","Monitor norm of function","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
759   if (flg) {
760     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
761     ierr = SNESMonitorSet(snes,SNESMonitorDefault,monviewer,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
762   }
763 
764   ierr = PetscOptionsString("-snes_monitor_range","Monitor range of elements of function","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
765   if (flg) {
766     ierr = SNESMonitorSet(snes,SNESMonitorRange,0,0);CHKERRQ(ierr);
767   }
768 
769   ierr = PetscOptionsString("-snes_ratiomonitor","Monitor ratios of norms of function","SNESMonitorSetRatio","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
770   if (flg) {
771     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
772     ierr = SNESMonitorSetRatio(snes,monviewer);CHKERRQ(ierr);
773   }
774 
775   ierr = PetscOptionsString("-snes_monitor_short","Monitor norm of function (fewer digits)","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
776   if (flg) {
777     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
778     ierr = SNESMonitorSet(snes,SNESMonitorDefaultShort,monviewer,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
779   }
780 
781   ierr = PetscOptionsString("-snes_monitor_field","Monitor norm of function (split into fields)","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
782   if (flg) {
783     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
784     ierr = SNESMonitorSet(snes,SNESMonitorDefaultField,monviewer,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
785   }
786 
787   ierr = PetscOptionsString("-snes_monitor_python","Use Python function","SNESMonitorSet",0,monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
788   if (flg) {ierr = PetscPythonMonitorSet((PetscObject)snes,monfilename);CHKERRQ(ierr);}
789 
790   flg  = PETSC_FALSE;
791   ierr = PetscOptionsBool("-snes_monitor_solution","Plot solution at each iteration","SNESMonitorSolution",flg,&flg,NULL);CHKERRQ(ierr);
792   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorSolution,0,0);CHKERRQ(ierr);}
793   flg  = PETSC_FALSE;
794   ierr = PetscOptionsBool("-snes_monitor_solution_update","Plot correction at each iteration","SNESMonitorSolutionUpdate",flg,&flg,NULL);CHKERRQ(ierr);
795   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorSolutionUpdate,0,0);CHKERRQ(ierr);}
796   flg  = PETSC_FALSE;
797   ierr = PetscOptionsBool("-snes_monitor_residual","Plot residual at each iteration","SNESMonitorResidual",flg,&flg,NULL);CHKERRQ(ierr);
798   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorResidual,0,0);CHKERRQ(ierr);}
799   flg  = PETSC_FALSE;
800   ierr = PetscOptionsBool("-snes_monitor_lg_residualnorm","Plot function norm at each iteration","SNESMonitorLGResidualNorm",flg,&flg,NULL);CHKERRQ(ierr);
801   if (flg) {
802     PetscObject *objs;
803 
804     ierr = SNESMonitorLGCreate(0,0,PETSC_DECIDE,PETSC_DECIDE,300,300,&objs);CHKERRQ(ierr);
805     ierr = SNESMonitorSet(snes,(PetscErrorCode (*)(SNES,PetscInt,PetscReal,void*))SNESMonitorLGResidualNorm,objs,(PetscErrorCode (*)(void**))SNESMonitorLGDestroy);CHKERRQ(ierr);
806   }
807   flg  = PETSC_FALSE;
808   ierr = PetscOptionsBool("-snes_monitor_lg_range","Plot function range at each iteration","SNESMonitorLGRange",flg,&flg,NULL);CHKERRQ(ierr);
809   if (flg) {
810     PetscViewer ctx;
811 
812     ierr = PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),0,0,PETSC_DECIDE,PETSC_DECIDE,300,300,&ctx);CHKERRQ(ierr);
813     ierr = SNESMonitorSet(snes,SNESMonitorLGRange,ctx,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
814   }
815 
816   flg  = PETSC_FALSE;
817   ierr = PetscOptionsBool("-snes_monitor_jacupdate_spectrum","Print the change in the spectrum of the Jacobian","SNESMonitorJacUpdateSpectrum",flg,&flg,NULL);CHKERRQ(ierr);
818   if (flg) {ierr = SNESMonitorSet(snes,SNESMonitorJacUpdateSpectrum,0,0);CHKERRQ(ierr);}
819 
820 
821   ierr = PetscOptionsString("-snes_monitor_fields","Monitor norm of function per field","SNESMonitorSet","stdout",monfilename,PETSC_MAX_PATH_LEN,&flg);CHKERRQ(ierr);
822   if (flg) {
823     ierr = PetscViewerASCIIOpen(PetscObjectComm((PetscObject)snes),monfilename,&monviewer);CHKERRQ(ierr);
824     ierr = SNESMonitorSet(snes,SNESMonitorFields,monviewer,(PetscErrorCode (*)(void**))PetscViewerDestroy);CHKERRQ(ierr);
825   }
826 
827   flg  = PETSC_FALSE;
828   ierr = PetscOptionsBool("-snes_fd","Use finite differences (slow) to compute Jacobian","SNESComputeJacobianDefault",flg,&flg,NULL);CHKERRQ(ierr);
829   if (flg) {
830     void *functx;
831     ierr = SNESGetFunction(snes,NULL,NULL,&functx);CHKERRQ(ierr);
832     ierr = SNESSetJacobian(snes,snes->jacobian,snes->jacobian_pre,SNESComputeJacobianDefault,functx);CHKERRQ(ierr);
833     ierr = PetscInfo(snes,"Setting default finite difference Jacobian matrix\n");CHKERRQ(ierr);
834   }
835 
836   flg  = PETSC_FALSE;
837   ierr = PetscOptionsBool("-snes_fd_function","Use finite differences (slow) to compute function from user objective","SNESObjectiveComputeFunctionDefaultFD",flg,&flg,NULL);CHKERRQ(ierr);
838   if (flg) {
839     ierr = SNESSetFunction(snes,NULL,SNESObjectiveComputeFunctionDefaultFD,NULL);CHKERRQ(ierr);
840   }
841 
842   flg  = PETSC_FALSE;
843   ierr = PetscOptionsBool("-snes_fd_color","Use finite differences with coloring to compute Jacobian","SNESComputeJacobianDefaultColor",flg,&flg,NULL);CHKERRQ(ierr);
844   if (flg) {
845     DM             dm;
846     DMSNES         sdm;
847     ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
848     ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
849     sdm->jacobianctx = NULL;
850     ierr = SNESSetJacobian(snes,snes->jacobian,snes->jacobian_pre,SNESComputeJacobianDefaultColor,0);CHKERRQ(ierr);
851     ierr = PetscInfo(snes,"Setting default finite difference coloring Jacobian matrix\n");CHKERRQ(ierr);
852   }
853 
854   flg  = PETSC_FALSE;
855   ierr = PetscOptionsBool("-snes_mf_operator","Use a Matrix-Free Jacobian with user-provided preconditioner matrix","MatCreateSNESMF",PETSC_FALSE,&snes->mf_operator,&flg);CHKERRQ(ierr);
856   if (flg && snes->mf_operator) {
857     snes->mf_operator = PETSC_TRUE;
858     snes->mf          = PETSC_TRUE;
859   }
860   flg  = PETSC_FALSE;
861   ierr = PetscOptionsBool("-snes_mf","Use a Matrix-Free Jacobian with no preconditioner matrix","MatCreateSNESMF",PETSC_FALSE,&snes->mf,&flg);CHKERRQ(ierr);
862   if (!flg && snes->mf_operator) snes->mf = PETSC_TRUE;
863   ierr = PetscOptionsInt("-snes_mf_version","Matrix-Free routines version 1 or 2","None",snes->mf_version,&snes->mf_version,0);CHKERRQ(ierr);
864 
865   flg  = PETSC_FALSE;
866   ierr = SNESGetNPCSide(snes,&pcside);CHKERRQ(ierr);
867   ierr = PetscOptionsEnum("-snes_npc_side","SNES nonlinear preconditioner side","SNESSetNPCSide",PCSides,(PetscEnum)pcside,(PetscEnum*)&pcside,&flg);CHKERRQ(ierr);
868   if (flg) {ierr = SNESSetNPCSide(snes,pcside);CHKERRQ(ierr);}
869 
870 #if defined(PETSC_HAVE_SAWS)
871   /*
872     Publish convergence information using SAWs
873   */
874   flg  = PETSC_FALSE;
875   ierr = PetscOptionsBool("-snes_monitor_saws","Publish SNES progress using SAWs","SNESMonitorSet",flg,&flg,NULL);CHKERRQ(ierr);
876   if (flg) {
877     void *ctx;
878     ierr = SNESMonitorSAWsCreate(snes,&ctx);CHKERRQ(ierr);
879     ierr = SNESMonitorSet(snes,SNESMonitorSAWs,ctx,SNESMonitorSAWsDestroy);CHKERRQ(ierr);
880   }
881 #endif
882 #if defined(PETSC_HAVE_SAWS)
883   {
884   PetscBool set;
885   flg  = PETSC_FALSE;
886   ierr = PetscOptionsBool("-snes_saws_block","Block for SAWs at end of SNESSolve","PetscObjectSAWsBlock",((PetscObject)snes)->amspublishblock,&flg,&set);CHKERRQ(ierr);
887   if (set) {
888     ierr = PetscObjectSAWsSetBlock((PetscObject)snes,flg);CHKERRQ(ierr);
889   }
890   }
891 #endif
892 
893   for (i = 0; i < numberofsetfromoptions; i++) {
894     ierr = (*othersetfromoptions[i])(snes);CHKERRQ(ierr);
895   }
896 
897   if (snes->ops->setfromoptions) {
898     ierr = (*snes->ops->setfromoptions)(PetscOptionsObject,snes);CHKERRQ(ierr);
899   }
900 
901   /* process any options handlers added with PetscObjectAddOptionsHandler() */
902   ierr = PetscObjectProcessOptionsHandlers((PetscObject)snes);CHKERRQ(ierr);
903   ierr = PetscOptionsEnd();CHKERRQ(ierr);
904 
905   if (!snes->linesearch) {
906     ierr = SNESGetLineSearch(snes, &snes->linesearch);CHKERRQ(ierr);
907   }
908   ierr = SNESLineSearchSetFromOptions(snes->linesearch);CHKERRQ(ierr);
909 
910   if (!snes->ksp) {ierr = SNESGetKSP(snes,&snes->ksp);CHKERRQ(ierr);}
911   ierr = KSPSetOperators(snes->ksp,snes->jacobian,snes->jacobian_pre);CHKERRQ(ierr);
912   ierr = KSPSetFromOptions(snes->ksp);CHKERRQ(ierr);
913 
914   /* if someone has set the SNES NPC type, create it. */
915   ierr = SNESGetOptionsPrefix(snes, &optionsprefix);CHKERRQ(ierr);
916   ierr = PetscOptionsHasName(optionsprefix, "-npc_snes_type", &pcset);CHKERRQ(ierr);
917   if (pcset && (!snes->pc)) {
918     ierr = SNESGetNPC(snes, &snes->pc);CHKERRQ(ierr);
919   }
920   PetscFunctionReturn(0);
921 }
922 
923 #undef __FUNCT__
924 #define __FUNCT__ "SNESSetComputeApplicationContext"
925 /*@C
926    SNESSetComputeApplicationContext - Sets an optional function to compute a user-defined context for
927    the nonlinear solvers.
928 
929    Logically Collective on SNES
930 
931    Input Parameters:
932 +  snes - the SNES context
933 .  compute - function to compute the context
934 -  destroy - function to destroy the context
935 
936    Level: intermediate
937 
938    Notes:
939    This function is currently not available from Fortran.
940 
941 .keywords: SNES, nonlinear, set, application, context
942 
943 .seealso: SNESGetApplicationContext(), SNESSetComputeApplicationContext(), SNESGetApplicationContext()
944 @*/
945 PetscErrorCode  SNESSetComputeApplicationContext(SNES snes,PetscErrorCode (*compute)(SNES,void**),PetscErrorCode (*destroy)(void**))
946 {
947   PetscFunctionBegin;
948   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
949   snes->ops->usercompute = compute;
950   snes->ops->userdestroy = destroy;
951   PetscFunctionReturn(0);
952 }
953 
954 #undef __FUNCT__
955 #define __FUNCT__ "SNESSetApplicationContext"
956 /*@
957    SNESSetApplicationContext - Sets the optional user-defined context for
958    the nonlinear solvers.
959 
960    Logically Collective on SNES
961 
962    Input Parameters:
963 +  snes - the SNES context
964 -  usrP - optional user context
965 
966    Level: intermediate
967 
968 .keywords: SNES, nonlinear, set, application, context
969 
970 .seealso: SNESGetApplicationContext()
971 @*/
972 PetscErrorCode  SNESSetApplicationContext(SNES snes,void *usrP)
973 {
974   PetscErrorCode ierr;
975   KSP            ksp;
976 
977   PetscFunctionBegin;
978   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
979   ierr       = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
980   ierr       = KSPSetApplicationContext(ksp,usrP);CHKERRQ(ierr);
981   snes->user = usrP;
982   PetscFunctionReturn(0);
983 }
984 
985 #undef __FUNCT__
986 #define __FUNCT__ "SNESGetApplicationContext"
987 /*@
988    SNESGetApplicationContext - Gets the user-defined context for the
989    nonlinear solvers.
990 
991    Not Collective
992 
993    Input Parameter:
994 .  snes - SNES context
995 
996    Output Parameter:
997 .  usrP - user context
998 
999    Level: intermediate
1000 
1001 .keywords: SNES, nonlinear, get, application, context
1002 
1003 .seealso: SNESSetApplicationContext()
1004 @*/
1005 PetscErrorCode  SNESGetApplicationContext(SNES snes,void *usrP)
1006 {
1007   PetscFunctionBegin;
1008   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1009   *(void**)usrP = snes->user;
1010   PetscFunctionReturn(0);
1011 }
1012 
1013 #undef __FUNCT__
1014 #define __FUNCT__ "SNESGetIterationNumber"
1015 /*@
1016    SNESGetIterationNumber - Gets the number of nonlinear iterations completed
1017    at this time.
1018 
1019    Not Collective
1020 
1021    Input Parameter:
1022 .  snes - SNES context
1023 
1024    Output Parameter:
1025 .  iter - iteration number
1026 
1027    Notes:
1028    For example, during the computation of iteration 2 this would return 1.
1029 
1030    This is useful for using lagged Jacobians (where one does not recompute the
1031    Jacobian at each SNES iteration). For example, the code
1032 .vb
1033       ierr = SNESGetIterationNumber(snes,&it);
1034       if (!(it % 2)) {
1035         [compute Jacobian here]
1036       }
1037 .ve
1038    can be used in your ComputeJacobian() function to cause the Jacobian to be
1039    recomputed every second SNES iteration.
1040 
1041    Level: intermediate
1042 
1043 .keywords: SNES, nonlinear, get, iteration, number,
1044 
1045 .seealso:   SNESGetLinearSolveIterations()
1046 @*/
1047 PetscErrorCode  SNESGetIterationNumber(SNES snes,PetscInt *iter)
1048 {
1049   PetscFunctionBegin;
1050   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1051   PetscValidIntPointer(iter,2);
1052   *iter = snes->iter;
1053   PetscFunctionReturn(0);
1054 }
1055 
1056 #undef __FUNCT__
1057 #define __FUNCT__ "SNESSetIterationNumber"
1058 /*@
1059    SNESSetIterationNumber - Sets the current iteration number.
1060 
1061    Not Collective
1062 
1063    Input Parameter:
1064 .  snes - SNES context
1065 .  iter - iteration number
1066 
1067    Level: developer
1068 
1069 .keywords: SNES, nonlinear, set, iteration, number,
1070 
1071 .seealso:   SNESGetLinearSolveIterations()
1072 @*/
1073 PetscErrorCode  SNESSetIterationNumber(SNES snes,PetscInt iter)
1074 {
1075   PetscErrorCode ierr;
1076 
1077   PetscFunctionBegin;
1078   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1079   ierr       = PetscObjectSAWsTakeAccess((PetscObject)snes);CHKERRQ(ierr);
1080   snes->iter = iter;
1081   ierr       = PetscObjectSAWsGrantAccess((PetscObject)snes);CHKERRQ(ierr);
1082   PetscFunctionReturn(0);
1083 }
1084 
1085 #undef __FUNCT__
1086 #define __FUNCT__ "SNESGetNonlinearStepFailures"
1087 /*@
1088    SNESGetNonlinearStepFailures - Gets the number of unsuccessful steps
1089    attempted by the nonlinear solver.
1090 
1091    Not Collective
1092 
1093    Input Parameter:
1094 .  snes - SNES context
1095 
1096    Output Parameter:
1097 .  nfails - number of unsuccessful steps attempted
1098 
1099    Notes:
1100    This counter is reset to zero for each successive call to SNESSolve().
1101 
1102    Level: intermediate
1103 
1104 .keywords: SNES, nonlinear, get, number, unsuccessful, steps
1105 
1106 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
1107           SNESSetMaxNonlinearStepFailures(), SNESGetMaxNonlinearStepFailures()
1108 @*/
1109 PetscErrorCode  SNESGetNonlinearStepFailures(SNES snes,PetscInt *nfails)
1110 {
1111   PetscFunctionBegin;
1112   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1113   PetscValidIntPointer(nfails,2);
1114   *nfails = snes->numFailures;
1115   PetscFunctionReturn(0);
1116 }
1117 
1118 #undef __FUNCT__
1119 #define __FUNCT__ "SNESSetMaxNonlinearStepFailures"
1120 /*@
1121    SNESSetMaxNonlinearStepFailures - Sets the maximum number of unsuccessful steps
1122    attempted by the nonlinear solver before it gives up.
1123 
1124    Not Collective
1125 
1126    Input Parameters:
1127 +  snes     - SNES context
1128 -  maxFails - maximum of unsuccessful steps
1129 
1130    Level: intermediate
1131 
1132 .keywords: SNES, nonlinear, set, maximum, unsuccessful, steps
1133 
1134 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
1135           SNESGetMaxNonlinearStepFailures(), SNESGetNonlinearStepFailures()
1136 @*/
1137 PetscErrorCode  SNESSetMaxNonlinearStepFailures(SNES snes, PetscInt maxFails)
1138 {
1139   PetscFunctionBegin;
1140   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1141   snes->maxFailures = maxFails;
1142   PetscFunctionReturn(0);
1143 }
1144 
1145 #undef __FUNCT__
1146 #define __FUNCT__ "SNESGetMaxNonlinearStepFailures"
1147 /*@
1148    SNESGetMaxNonlinearStepFailures - Gets the maximum number of unsuccessful steps
1149    attempted by the nonlinear solver before it gives up.
1150 
1151    Not Collective
1152 
1153    Input Parameter:
1154 .  snes     - SNES context
1155 
1156    Output Parameter:
1157 .  maxFails - maximum of unsuccessful steps
1158 
1159    Level: intermediate
1160 
1161 .keywords: SNES, nonlinear, get, maximum, unsuccessful, steps
1162 
1163 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(),
1164           SNESSetMaxNonlinearStepFailures(), SNESGetNonlinearStepFailures()
1165 
1166 @*/
1167 PetscErrorCode  SNESGetMaxNonlinearStepFailures(SNES snes, PetscInt *maxFails)
1168 {
1169   PetscFunctionBegin;
1170   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1171   PetscValidIntPointer(maxFails,2);
1172   *maxFails = snes->maxFailures;
1173   PetscFunctionReturn(0);
1174 }
1175 
1176 #undef __FUNCT__
1177 #define __FUNCT__ "SNESGetNumberFunctionEvals"
1178 /*@
1179    SNESGetNumberFunctionEvals - Gets the number of user provided function evaluations
1180      done by SNES.
1181 
1182    Not Collective
1183 
1184    Input Parameter:
1185 .  snes     - SNES context
1186 
1187    Output Parameter:
1188 .  nfuncs - number of evaluations
1189 
1190    Level: intermediate
1191 
1192    Notes: Reset every time SNESSolve is called unless SNESSetCountersReset() is used.
1193 
1194 .keywords: SNES, nonlinear, get, maximum, unsuccessful, steps
1195 
1196 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(), SNESGetLinearSolveFailures(), SNESSetCountersReset()
1197 @*/
1198 PetscErrorCode  SNESGetNumberFunctionEvals(SNES snes, PetscInt *nfuncs)
1199 {
1200   PetscFunctionBegin;
1201   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1202   PetscValidIntPointer(nfuncs,2);
1203   *nfuncs = snes->nfuncs;
1204   PetscFunctionReturn(0);
1205 }
1206 
1207 #undef __FUNCT__
1208 #define __FUNCT__ "SNESGetLinearSolveFailures"
1209 /*@
1210    SNESGetLinearSolveFailures - Gets the number of failed (non-converged)
1211    linear solvers.
1212 
1213    Not Collective
1214 
1215    Input Parameter:
1216 .  snes - SNES context
1217 
1218    Output Parameter:
1219 .  nfails - number of failed solves
1220 
1221    Level: intermediate
1222 
1223    Options Database Keys:
1224 . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated
1225 
1226    Notes:
1227    This counter is reset to zero for each successive call to SNESSolve().
1228 
1229 .keywords: SNES, nonlinear, get, number, unsuccessful, steps
1230 
1231 .seealso: SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures()
1232 @*/
1233 PetscErrorCode  SNESGetLinearSolveFailures(SNES snes,PetscInt *nfails)
1234 {
1235   PetscFunctionBegin;
1236   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1237   PetscValidIntPointer(nfails,2);
1238   *nfails = snes->numLinearSolveFailures;
1239   PetscFunctionReturn(0);
1240 }
1241 
1242 #undef __FUNCT__
1243 #define __FUNCT__ "SNESSetMaxLinearSolveFailures"
1244 /*@
1245    SNESSetMaxLinearSolveFailures - the number of failed linear solve attempts
1246    allowed before SNES returns with a diverged reason of SNES_DIVERGED_LINEAR_SOLVE
1247 
1248    Logically Collective on SNES
1249 
1250    Input Parameters:
1251 +  snes     - SNES context
1252 -  maxFails - maximum allowed linear solve failures
1253 
1254    Level: intermediate
1255 
1256    Options Database Keys:
1257 . -snes_max_linear_solve_fail <num> - The number of failures before the solve is terminated
1258 
1259    Notes: By default this is 0; that is SNES returns on the first failed linear solve
1260 
1261 .keywords: SNES, nonlinear, set, maximum, unsuccessful, steps
1262 
1263 .seealso: SNESGetLinearSolveFailures(), SNESGetMaxLinearSolveFailures(), SNESGetLinearSolveIterations()
1264 @*/
1265 PetscErrorCode  SNESSetMaxLinearSolveFailures(SNES snes, PetscInt maxFails)
1266 {
1267   PetscFunctionBegin;
1268   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1269   PetscValidLogicalCollectiveInt(snes,maxFails,2);
1270   snes->maxLinearSolveFailures = maxFails;
1271   PetscFunctionReturn(0);
1272 }
1273 
1274 #undef __FUNCT__
1275 #define __FUNCT__ "SNESGetMaxLinearSolveFailures"
1276 /*@
1277    SNESGetMaxLinearSolveFailures - gets the maximum number of linear solve failures that
1278      are allowed before SNES terminates
1279 
1280    Not Collective
1281 
1282    Input Parameter:
1283 .  snes     - SNES context
1284 
1285    Output Parameter:
1286 .  maxFails - maximum of unsuccessful solves allowed
1287 
1288    Level: intermediate
1289 
1290    Notes: By default this is 1; that is SNES returns on the first failed linear solve
1291 
1292 .keywords: SNES, nonlinear, get, maximum, unsuccessful, steps
1293 
1294 .seealso: SNESGetLinearSolveFailures(), SNESGetLinearSolveIterations(), SNESSetMaxLinearSolveFailures(),
1295 @*/
1296 PetscErrorCode  SNESGetMaxLinearSolveFailures(SNES snes, PetscInt *maxFails)
1297 {
1298   PetscFunctionBegin;
1299   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1300   PetscValidIntPointer(maxFails,2);
1301   *maxFails = snes->maxLinearSolveFailures;
1302   PetscFunctionReturn(0);
1303 }
1304 
1305 #undef __FUNCT__
1306 #define __FUNCT__ "SNESGetLinearSolveIterations"
1307 /*@
1308    SNESGetLinearSolveIterations - Gets the total number of linear iterations
1309    used by the nonlinear solver.
1310 
1311    Not Collective
1312 
1313    Input Parameter:
1314 .  snes - SNES context
1315 
1316    Output Parameter:
1317 .  lits - number of linear iterations
1318 
1319    Notes:
1320    This counter is reset to zero for each successive call to SNESSolve() unless SNESSetCountersReset() is used.
1321 
1322    Level: intermediate
1323 
1324 .keywords: SNES, nonlinear, get, number, linear, iterations
1325 
1326 .seealso:  SNESGetIterationNumber(), SNESGetLinearSolveFailures(), SNESGetMaxLinearSolveFailures(), SNESSetCountersReset()
1327 @*/
1328 PetscErrorCode  SNESGetLinearSolveIterations(SNES snes,PetscInt *lits)
1329 {
1330   PetscFunctionBegin;
1331   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1332   PetscValidIntPointer(lits,2);
1333   *lits = snes->linear_its;
1334   PetscFunctionReturn(0);
1335 }
1336 
1337 #undef __FUNCT__
1338 #define __FUNCT__ "SNESSetCountersReset"
1339 /*@
1340    SNESSetCountersReset - Sets whether or not the counters for linear iterations and function evaluations
1341    are reset every time SNESSolve() is called.
1342 
1343    Logically Collective on SNES
1344 
1345    Input Parameter:
1346 +  snes - SNES context
1347 -  reset - whether to reset the counters or not
1348 
1349    Notes:
1350    This is automatically called with FALSE
1351 
1352    Level: developer
1353 
1354 .keywords: SNES, nonlinear, set, reset, number, linear, iterations
1355 
1356 .seealso:  SNESGetNumberFunctionEvals(), SNESGetNumberLinearSolveIterations(), SNESGetNPC()
1357 @*/
1358 PetscErrorCode  SNESSetCountersReset(SNES snes,PetscBool reset)
1359 {
1360   PetscFunctionBegin;
1361   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1362   PetscValidLogicalCollectiveBool(snes,reset,2);
1363   snes->counters_reset = reset;
1364   PetscFunctionReturn(0);
1365 }
1366 
1367 
1368 #undef __FUNCT__
1369 #define __FUNCT__ "SNESSetKSP"
1370 /*@
1371    SNESSetKSP - Sets a KSP context for the SNES object to use
1372 
1373    Not Collective, but the SNES and KSP objects must live on the same MPI_Comm
1374 
1375    Input Parameters:
1376 +  snes - the SNES context
1377 -  ksp - the KSP context
1378 
1379    Notes:
1380    The SNES object already has its KSP object, you can obtain with SNESGetKSP()
1381    so this routine is rarely needed.
1382 
1383    The KSP object that is already in the SNES object has its reference count
1384    decreased by one.
1385 
1386    Level: developer
1387 
1388 .keywords: SNES, nonlinear, get, KSP, context
1389 
1390 .seealso: KSPGetPC(), SNESCreate(), KSPCreate(), SNESSetKSP()
1391 @*/
1392 PetscErrorCode  SNESSetKSP(SNES snes,KSP ksp)
1393 {
1394   PetscErrorCode ierr;
1395 
1396   PetscFunctionBegin;
1397   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1398   PetscValidHeaderSpecific(ksp,KSP_CLASSID,2);
1399   PetscCheckSameComm(snes,1,ksp,2);
1400   ierr = PetscObjectReference((PetscObject)ksp);CHKERRQ(ierr);
1401   if (snes->ksp) {ierr = PetscObjectDereference((PetscObject)snes->ksp);CHKERRQ(ierr);}
1402   snes->ksp = ksp;
1403   PetscFunctionReturn(0);
1404 }
1405 
1406 /* -----------------------------------------------------------*/
1407 #undef __FUNCT__
1408 #define __FUNCT__ "SNESCreate"
1409 /*@
1410    SNESCreate - Creates a nonlinear solver context.
1411 
1412    Collective on MPI_Comm
1413 
1414    Input Parameters:
1415 .  comm - MPI communicator
1416 
1417    Output Parameter:
1418 .  outsnes - the new SNES context
1419 
1420    Options Database Keys:
1421 +   -snes_mf - Activates default matrix-free Jacobian-vector products,
1422                and no preconditioning matrix
1423 .   -snes_mf_operator - Activates default matrix-free Jacobian-vector
1424                products, and a user-provided preconditioning matrix
1425                as set by SNESSetJacobian()
1426 -   -snes_fd - Uses (slow!) finite differences to compute Jacobian
1427 
1428    Level: beginner
1429 
1430 .keywords: SNES, nonlinear, create, context
1431 
1432 .seealso: SNESSolve(), SNESDestroy(), SNES, SNESSetLagPreconditioner()
1433 
1434 @*/
1435 PetscErrorCode  SNESCreate(MPI_Comm comm,SNES *outsnes)
1436 {
1437   PetscErrorCode ierr;
1438   SNES           snes;
1439   SNESKSPEW      *kctx;
1440 
1441   PetscFunctionBegin;
1442   PetscValidPointer(outsnes,2);
1443   *outsnes = NULL;
1444   ierr = SNESInitializePackage();CHKERRQ(ierr);
1445 
1446   ierr = PetscHeaderCreate(snes,SNES_CLASSID,"SNES","Nonlinear solver","SNES",comm,SNESDestroy,SNESView);CHKERRQ(ierr);
1447 
1448   snes->ops->converged    = SNESConvergedDefault;
1449   snes->usesksp           = PETSC_TRUE;
1450   snes->tolerancesset     = PETSC_FALSE;
1451   snes->max_its           = 50;
1452   snes->max_funcs         = 10000;
1453   snes->norm              = 0.0;
1454   snes->normschedule      = SNES_NORM_ALWAYS;
1455   snes->functype          = SNES_FUNCTION_DEFAULT;
1456 #if defined(PETSC_USE_REAL_SINGLE)
1457   snes->rtol              = 1.e-5;
1458 #else
1459   snes->rtol              = 1.e-8;
1460 #endif
1461   snes->ttol              = 0.0;
1462 #if defined(PETSC_USE_REAL_SINGLE)
1463   snes->abstol            = 1.e-25;
1464 #else
1465   snes->abstol            = 1.e-50;
1466 #endif
1467   snes->stol              = 1.e-8;
1468 #if defined(PETSC_USE_REAL_SINGLE)
1469   snes->deltatol          = 1.e-6;
1470 #else
1471   snes->deltatol          = 1.e-12;
1472 #endif
1473   snes->nfuncs            = 0;
1474   snes->numFailures       = 0;
1475   snes->maxFailures       = 1;
1476   snes->linear_its        = 0;
1477   snes->lagjacobian       = 1;
1478   snes->jac_iter          = 0;
1479   snes->lagjac_persist    = PETSC_FALSE;
1480   snes->lagpreconditioner = 1;
1481   snes->pre_iter          = 0;
1482   snes->lagpre_persist    = PETSC_FALSE;
1483   snes->numbermonitors    = 0;
1484   snes->data              = 0;
1485   snes->setupcalled       = PETSC_FALSE;
1486   snes->ksp_ewconv        = PETSC_FALSE;
1487   snes->nwork             = 0;
1488   snes->work              = 0;
1489   snes->nvwork            = 0;
1490   snes->vwork             = 0;
1491   snes->conv_hist_len     = 0;
1492   snes->conv_hist_max     = 0;
1493   snes->conv_hist         = NULL;
1494   snes->conv_hist_its     = NULL;
1495   snes->conv_hist_reset   = PETSC_TRUE;
1496   snes->counters_reset    = PETSC_TRUE;
1497   snes->vec_func_init_set = PETSC_FALSE;
1498   snes->reason            = SNES_CONVERGED_ITERATING;
1499   snes->pcside            = PC_RIGHT;
1500 
1501   snes->mf          = PETSC_FALSE;
1502   snes->mf_operator = PETSC_FALSE;
1503   snes->mf_version  = 1;
1504 
1505   snes->numLinearSolveFailures = 0;
1506   snes->maxLinearSolveFailures = 1;
1507 
1508   /* Create context to compute Eisenstat-Walker relative tolerance for KSP */
1509   ierr = PetscNewLog(snes,&kctx);CHKERRQ(ierr);
1510 
1511   snes->kspconvctx  = (void*)kctx;
1512   kctx->version     = 2;
1513   kctx->rtol_0      = .3; /* Eisenstat and Walker suggest rtol_0=.5, but
1514                              this was too large for some test cases */
1515   kctx->rtol_last   = 0.0;
1516   kctx->rtol_max    = .9;
1517   kctx->gamma       = 1.0;
1518   kctx->alpha       = .5*(1.0 + PetscSqrtReal(5.0));
1519   kctx->alpha2      = kctx->alpha;
1520   kctx->threshold   = .1;
1521   kctx->lresid_last = 0.0;
1522   kctx->norm_last   = 0.0;
1523 
1524   *outsnes = snes;
1525   PetscFunctionReturn(0);
1526 }
1527 
1528 /*MC
1529     SNESFunction - Functional form used to convey the nonlinear function to be solved by SNES
1530 
1531      Synopsis:
1532      #include "petscsnes.h"
1533      PetscErrorCode SNESFunction(SNES snes,Vec x,Vec f,void *ctx);
1534 
1535      Input Parameters:
1536 +     snes - the SNES context
1537 .     x    - state at which to evaluate residual
1538 -     ctx     - optional user-defined function context, passed in with SNESSetFunction()
1539 
1540      Output Parameter:
1541 .     f  - vector to put residual (function value)
1542 
1543    Level: intermediate
1544 
1545 .seealso:   SNESSetFunction(), SNESGetFunction()
1546 M*/
1547 
1548 #undef __FUNCT__
1549 #define __FUNCT__ "SNESSetFunction"
1550 /*@C
1551    SNESSetFunction - Sets the function evaluation routine and function
1552    vector for use by the SNES routines in solving systems of nonlinear
1553    equations.
1554 
1555    Logically Collective on SNES
1556 
1557    Input Parameters:
1558 +  snes - the SNES context
1559 .  r - vector to store function value
1560 .  f - function evaluation routine; see SNESFunction for calling sequence details
1561 -  ctx - [optional] user-defined context for private data for the
1562          function evaluation routine (may be NULL)
1563 
1564    Notes:
1565    The Newton-like methods typically solve linear systems of the form
1566 $      f'(x) x = -f(x),
1567    where f'(x) denotes the Jacobian matrix and f(x) is the function.
1568 
1569    Level: beginner
1570 
1571 .keywords: SNES, nonlinear, set, function
1572 
1573 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetPicard(), SNESFunction
1574 @*/
1575 PetscErrorCode  SNESSetFunction(SNES snes,Vec r,PetscErrorCode (*f)(SNES,Vec,Vec,void*),void *ctx)
1576 {
1577   PetscErrorCode ierr;
1578   DM             dm;
1579 
1580   PetscFunctionBegin;
1581   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1582   if (r) {
1583     PetscValidHeaderSpecific(r,VEC_CLASSID,2);
1584     PetscCheckSameComm(snes,1,r,2);
1585     ierr = PetscObjectReference((PetscObject)r);CHKERRQ(ierr);
1586     ierr = VecDestroy(&snes->vec_func);CHKERRQ(ierr);
1587 
1588     snes->vec_func = r;
1589   }
1590   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1591   ierr = DMSNESSetFunction(dm,f,ctx);CHKERRQ(ierr);
1592   PetscFunctionReturn(0);
1593 }
1594 
1595 
1596 #undef __FUNCT__
1597 #define __FUNCT__ "SNESSetInitialFunction"
1598 /*@C
1599    SNESSetInitialFunction - Sets the function vector to be used as the
1600    function norm at the initialization of the method.  In some
1601    instances, the user has precomputed the function before calling
1602    SNESSolve.  This function allows one to avoid a redundant call
1603    to SNESComputeFunction in that case.
1604 
1605    Logically Collective on SNES
1606 
1607    Input Parameters:
1608 +  snes - the SNES context
1609 -  f - vector to store function value
1610 
1611    Notes:
1612    This should not be modified during the solution procedure.
1613 
1614    This is used extensively in the SNESFAS hierarchy and in nonlinear preconditioning.
1615 
1616    Level: developer
1617 
1618 .keywords: SNES, nonlinear, set, function
1619 
1620 .seealso: SNESSetFunction(), SNESComputeFunction(), SNESSetInitialFunctionNorm()
1621 @*/
1622 PetscErrorCode  SNESSetInitialFunction(SNES snes, Vec f)
1623 {
1624   PetscErrorCode ierr;
1625   Vec            vec_func;
1626 
1627   PetscFunctionBegin;
1628   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1629   PetscValidHeaderSpecific(f,VEC_CLASSID,2);
1630   PetscCheckSameComm(snes,1,f,2);
1631   if (snes->pcside == PC_LEFT && snes->functype == SNES_FUNCTION_PRECONDITIONED) {
1632     snes->vec_func_init_set = PETSC_FALSE;
1633     PetscFunctionReturn(0);
1634   }
1635   ierr = SNESGetFunction(snes,&vec_func,NULL,NULL);CHKERRQ(ierr);
1636   ierr = VecCopy(f, vec_func);CHKERRQ(ierr);
1637 
1638   snes->vec_func_init_set = PETSC_TRUE;
1639   PetscFunctionReturn(0);
1640 }
1641 
1642 #undef __FUNCT__
1643 #define __FUNCT__ "SNESSetNormSchedule"
1644 /*@
1645    SNESSetNormSchedule - Sets the SNESNormSchedule used in covergence and monitoring
1646    of the SNES method.
1647 
1648    Logically Collective on SNES
1649 
1650    Input Parameters:
1651 +  snes - the SNES context
1652 -  normschedule - the frequency of norm computation
1653 
1654    Options Database Key:
1655 .  -snes_norm_schedule <none, always, initialonly, finalonly, initalfinalonly>
1656 
1657    Notes:
1658    Only certain SNES methods support certain SNESNormSchedules.  Most require evaluation
1659    of the nonlinear function and the taking of its norm at every iteration to
1660    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
1661    (SNESNGS) and the like do not require the norm of the function to be computed, and therfore
1662    may either be monitored for convergence or not.  As these are often used as nonlinear
1663    preconditioners, monitoring the norm of their error is not a useful enterprise within
1664    their solution.
1665 
1666    Level: developer
1667 
1668 .keywords: SNES, nonlinear, set, function, norm, type
1669 
1670 .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1671 @*/
1672 PetscErrorCode  SNESSetNormSchedule(SNES snes, SNESNormSchedule normschedule)
1673 {
1674   PetscFunctionBegin;
1675   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1676   snes->normschedule = normschedule;
1677   PetscFunctionReturn(0);
1678 }
1679 
1680 
1681 #undef __FUNCT__
1682 #define __FUNCT__ "SNESGetNormSchedule"
1683 /*@
1684    SNESGetNormSchedule - Gets the SNESNormSchedule used in covergence and monitoring
1685    of the SNES method.
1686 
1687    Logically Collective on SNES
1688 
1689    Input Parameters:
1690 +  snes - the SNES context
1691 -  normschedule - the type of the norm used
1692 
1693    Level: advanced
1694 
1695 .keywords: SNES, nonlinear, set, function, norm, type
1696 
1697 .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1698 @*/
1699 PetscErrorCode  SNESGetNormSchedule(SNES snes, SNESNormSchedule *normschedule)
1700 {
1701   PetscFunctionBegin;
1702   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1703   *normschedule = snes->normschedule;
1704   PetscFunctionReturn(0);
1705 }
1706 
1707 
1708 #undef __FUNCT__
1709 #define __FUNCT__ "SNESSetFunctionType"
1710 /*@C
1711    SNESSetFunctionType - Sets the SNESNormSchedule used in covergence and monitoring
1712    of the SNES method.
1713 
1714    Logically Collective on SNES
1715 
1716    Input Parameters:
1717 +  snes - the SNES context
1718 -  normschedule - the frequency of norm computation
1719 
1720    Notes:
1721    Only certain SNES methods support certain SNESNormSchedules.  Most require evaluation
1722    of the nonlinear function and the taking of its norm at every iteration to
1723    even ensure convergence at all.  However, methods such as custom Gauss-Seidel methods
1724    (SNESNGS) and the like do not require the norm of the function to be computed, and therfore
1725    may either be monitored for convergence or not.  As these are often used as nonlinear
1726    preconditioners, monitoring the norm of their error is not a useful enterprise within
1727    their solution.
1728 
1729    Level: developer
1730 
1731 .keywords: SNES, nonlinear, set, function, norm, type
1732 
1733 .seealso: SNESGetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1734 @*/
1735 PetscErrorCode  SNESSetFunctionType(SNES snes, SNESFunctionType type)
1736 {
1737   PetscFunctionBegin;
1738   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1739   snes->functype = type;
1740   PetscFunctionReturn(0);
1741 }
1742 
1743 
1744 #undef __FUNCT__
1745 #define __FUNCT__ "SNESGetFunctionType"
1746 /*@C
1747    SNESGetFunctionType - Gets the SNESNormSchedule used in covergence and monitoring
1748    of the SNES method.
1749 
1750    Logically Collective on SNES
1751 
1752    Input Parameters:
1753 +  snes - the SNES context
1754 -  normschedule - the type of the norm used
1755 
1756    Level: advanced
1757 
1758 .keywords: SNES, nonlinear, set, function, norm, type
1759 
1760 .seealso: SNESSetNormSchedule(), SNESComputeFunction(), VecNorm(), SNESSetFunction(), SNESSetInitialFunction(), SNESNormSchedule
1761 @*/
1762 PetscErrorCode  SNESGetFunctionType(SNES snes, SNESFunctionType *type)
1763 {
1764   PetscFunctionBegin;
1765   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1766   *type = snes->functype;
1767   PetscFunctionReturn(0);
1768 }
1769 
1770 /*MC
1771     SNESNGSFunction - function used to convey a Gauss-Seidel sweep on the nonlinear function
1772 
1773      Synopsis:
1774      #include <petscsnes.h>
1775 $    SNESNGSFunction(SNES snes,Vec x,Vec b,void *ctx);
1776 
1777 +  X   - solution vector
1778 .  B   - RHS vector
1779 -  ctx - optional user-defined Gauss-Seidel context
1780 
1781    Level: intermediate
1782 
1783 .seealso:   SNESSetNGS(), SNESGetNGS()
1784 M*/
1785 
1786 #undef __FUNCT__
1787 #define __FUNCT__ "SNESSetNGS"
1788 /*@C
1789    SNESSetNGS - Sets the user nonlinear Gauss-Seidel routine for
1790    use with composed nonlinear solvers.
1791 
1792    Input Parameters:
1793 +  snes   - the SNES context
1794 .  f - function evaluation routine to apply Gauss-Seidel see SNESNGSFunction
1795 -  ctx    - [optional] user-defined context for private data for the
1796             smoother evaluation routine (may be NULL)
1797 
1798    Notes:
1799    The NGS routines are used by the composed nonlinear solver to generate
1800     a problem appropriate update to the solution, particularly FAS.
1801 
1802    Level: intermediate
1803 
1804 .keywords: SNES, nonlinear, set, Gauss-Seidel
1805 
1806 .seealso: SNESGetFunction(), SNESComputeNGS()
1807 @*/
1808 PetscErrorCode SNESSetNGS(SNES snes,PetscErrorCode (*f)(SNES,Vec,Vec,void*),void *ctx)
1809 {
1810   PetscErrorCode ierr;
1811   DM             dm;
1812 
1813   PetscFunctionBegin;
1814   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1815   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1816   ierr = DMSNESSetNGS(dm,f,ctx);CHKERRQ(ierr);
1817   PetscFunctionReturn(0);
1818 }
1819 
1820 #undef __FUNCT__
1821 #define __FUNCT__ "SNESPicardComputeFunction"
1822 PETSC_EXTERN PetscErrorCode SNESPicardComputeFunction(SNES snes,Vec x,Vec f,void *ctx)
1823 {
1824   PetscErrorCode ierr;
1825   DM             dm;
1826   DMSNES         sdm;
1827 
1828   PetscFunctionBegin;
1829   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1830   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
1831   /*  A(x)*x - b(x) */
1832   if (sdm->ops->computepfunction) {
1833     ierr = (*sdm->ops->computepfunction)(snes,x,f,sdm->pctx);CHKERRQ(ierr);
1834   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetPicard() to provide Picard function.");
1835 
1836   if (sdm->ops->computepjacobian) {
1837     ierr = (*sdm->ops->computepjacobian)(snes,x,snes->jacobian,snes->jacobian_pre,sdm->pctx);CHKERRQ(ierr);
1838   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetPicard() to provide Picard matrix.");
1839   ierr = VecScale(f,-1.0);CHKERRQ(ierr);
1840   ierr = MatMultAdd(snes->jacobian,x,f,f);CHKERRQ(ierr);
1841   PetscFunctionReturn(0);
1842 }
1843 
1844 #undef __FUNCT__
1845 #define __FUNCT__ "SNESPicardComputeJacobian"
1846 PETSC_EXTERN PetscErrorCode SNESPicardComputeJacobian(SNES snes,Vec x1,Mat J,Mat B,void *ctx)
1847 {
1848   PetscFunctionBegin;
1849   /* the jacobian matrix should be pre-filled in SNESPicardComputeFunction */
1850   PetscFunctionReturn(0);
1851 }
1852 
1853 #undef __FUNCT__
1854 #define __FUNCT__ "SNESSetPicard"
1855 /*@C
1856    SNESSetPicard - Use SNES to solve the semilinear-system A(x) x = b(x) via a Picard type iteration (Picard linearization)
1857 
1858    Logically Collective on SNES
1859 
1860    Input Parameters:
1861 +  snes - the SNES context
1862 .  r - vector to store function value
1863 .  b - function evaluation routine
1864 .  Amat - matrix with which A(x) x - b(x) is to be computed
1865 .  Pmat - matrix from which preconditioner is computed (usually the same as Amat)
1866 .  J  - function to compute matrix value, see SNESJacobianFunction for details on its calling sequence
1867 -  ctx - [optional] user-defined context for private data for the
1868          function evaluation routine (may be NULL)
1869 
1870    Notes:
1871     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
1872     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.
1873 
1874     One can call SNESSetPicard() or SNESSetFunction() (and possibly SNESSetJacobian()) but cannot call both
1875 
1876 $     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}
1877 $     Note that when an exact solver is used this corresponds to the "classic" Picard A(x^{n}) x^{n+1} = b(x^{n}) iteration.
1878 
1879      Run with -snes_mf_operator to solve the system with Newton's method using A(x^{n}) to construct the preconditioner.
1880 
1881    We implement the defect correction form of the Picard iteration because it converges much more generally when inexact linear solvers are used then
1882    the direct Picard iteration A(x^n) x^{n+1} = b(x^n)
1883 
1884    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
1885    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
1886    different please contact us at petsc-dev@mcs.anl.gov and we'll have an entirely new argument :-).
1887 
1888    Level: intermediate
1889 
1890 .keywords: SNES, nonlinear, set, function
1891 
1892 .seealso: SNESGetFunction(), SNESSetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESGetPicard(), SNESLineSearchPreCheckPicard(), SNESJacobianFunction
1893 @*/
1894 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)
1895 {
1896   PetscErrorCode ierr;
1897   DM             dm;
1898 
1899   PetscFunctionBegin;
1900   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1901   ierr = SNESGetDM(snes, &dm);CHKERRQ(ierr);
1902   ierr = DMSNESSetPicard(dm,b,J,ctx);CHKERRQ(ierr);
1903   ierr = SNESSetFunction(snes,r,SNESPicardComputeFunction,ctx);CHKERRQ(ierr);
1904   ierr = SNESSetJacobian(snes,Amat,Pmat,SNESPicardComputeJacobian,ctx);CHKERRQ(ierr);
1905   PetscFunctionReturn(0);
1906 }
1907 
1908 #undef __FUNCT__
1909 #define __FUNCT__ "SNESGetPicard"
1910 /*@C
1911    SNESGetPicard - Returns the context for the Picard iteration
1912 
1913    Not Collective, but Vec is parallel if SNES is parallel. Collective if Vec is requested, but has not been created yet.
1914 
1915    Input Parameter:
1916 .  snes - the SNES context
1917 
1918    Output Parameter:
1919 +  r - the function (or NULL)
1920 .  f - the function (or NULL); see SNESFunction for calling sequence details
1921 .  Amat - the matrix used to defined the operation A(x) x - b(x) (or NULL)
1922 .  Pmat  - the matrix from which the preconditioner will be constructed (or NULL)
1923 .  J - the function for matrix evaluation (or NULL); see SNESJacobianFunction for calling sequence details
1924 -  ctx - the function context (or NULL)
1925 
1926    Level: advanced
1927 
1928 .keywords: SNES, nonlinear, get, function
1929 
1930 .seealso: SNESSetPicard(), SNESGetFunction(), SNESGetJacobian(), SNESGetDM(), SNESFunction, SNESJacobianFunction
1931 @*/
1932 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)
1933 {
1934   PetscErrorCode ierr;
1935   DM             dm;
1936 
1937   PetscFunctionBegin;
1938   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1939   ierr = SNESGetFunction(snes,r,NULL,NULL);CHKERRQ(ierr);
1940   ierr = SNESGetJacobian(snes,Amat,Pmat,NULL,NULL);CHKERRQ(ierr);
1941   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
1942   ierr = DMSNESGetPicard(dm,f,J,ctx);CHKERRQ(ierr);
1943   PetscFunctionReturn(0);
1944 }
1945 
1946 #undef __FUNCT__
1947 #define __FUNCT__ "SNESSetComputeInitialGuess"
1948 /*@C
1949    SNESSetComputeInitialGuess - Sets a routine used to compute an initial guess for the problem
1950 
1951    Logically Collective on SNES
1952 
1953    Input Parameters:
1954 +  snes - the SNES context
1955 .  func - function evaluation routine
1956 -  ctx - [optional] user-defined context for private data for the
1957          function evaluation routine (may be NULL)
1958 
1959    Calling sequence of func:
1960 $    func (SNES snes,Vec x,void *ctx);
1961 
1962 .  f - function vector
1963 -  ctx - optional user-defined function context
1964 
1965    Level: intermediate
1966 
1967 .keywords: SNES, nonlinear, set, function
1968 
1969 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian()
1970 @*/
1971 PetscErrorCode  SNESSetComputeInitialGuess(SNES snes,PetscErrorCode (*func)(SNES,Vec,void*),void *ctx)
1972 {
1973   PetscFunctionBegin;
1974   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
1975   if (func) snes->ops->computeinitialguess = func;
1976   if (ctx)  snes->initialguessP            = ctx;
1977   PetscFunctionReturn(0);
1978 }
1979 
1980 /* --------------------------------------------------------------- */
1981 #undef __FUNCT__
1982 #define __FUNCT__ "SNESGetRhs"
1983 /*@C
1984    SNESGetRhs - Gets the vector for solving F(x) = rhs. If rhs is not set
1985    it assumes a zero right hand side.
1986 
1987    Logically Collective on SNES
1988 
1989    Input Parameter:
1990 .  snes - the SNES context
1991 
1992    Output Parameter:
1993 .  rhs - the right hand side vector or NULL if the right hand side vector is null
1994 
1995    Level: intermediate
1996 
1997 .keywords: SNES, nonlinear, get, function, right hand side
1998 
1999 .seealso: SNESGetSolution(), SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction()
2000 @*/
2001 PetscErrorCode  SNESGetRhs(SNES snes,Vec *rhs)
2002 {
2003   PetscFunctionBegin;
2004   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2005   PetscValidPointer(rhs,2);
2006   *rhs = snes->vec_rhs;
2007   PetscFunctionReturn(0);
2008 }
2009 
2010 #undef __FUNCT__
2011 #define __FUNCT__ "SNESComputeFunction"
2012 /*@
2013    SNESComputeFunction - Calls the function that has been set with SNESSetFunction().
2014 
2015    Collective on SNES
2016 
2017    Input Parameters:
2018 +  snes - the SNES context
2019 -  x - input vector
2020 
2021    Output Parameter:
2022 .  y - function vector, as set by SNESSetFunction()
2023 
2024    Notes:
2025    SNESComputeFunction() is typically used within nonlinear solvers
2026    implementations, so most users would not generally call this routine
2027    themselves.
2028 
2029    Level: developer
2030 
2031 .keywords: SNES, nonlinear, compute, function
2032 
2033 .seealso: SNESSetFunction(), SNESGetFunction()
2034 @*/
2035 PetscErrorCode  SNESComputeFunction(SNES snes,Vec x,Vec y)
2036 {
2037   PetscErrorCode ierr;
2038   DM             dm;
2039   DMSNES         sdm;
2040 
2041   PetscFunctionBegin;
2042   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2043   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
2044   PetscValidHeaderSpecific(y,VEC_CLASSID,3);
2045   PetscCheckSameComm(snes,1,x,2);
2046   PetscCheckSameComm(snes,1,y,3);
2047   ierr = VecValidValues(x,2,PETSC_TRUE);CHKERRQ(ierr);
2048 
2049   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2050   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2051   if (sdm->ops->computefunction) {
2052     ierr = PetscLogEventBegin(SNES_FunctionEval,snes,x,y,0);CHKERRQ(ierr);
2053     ierr = VecLockPush(x);CHKERRQ(ierr);
2054     PetscStackPush("SNES user function");
2055     ierr = (*sdm->ops->computefunction)(snes,x,y,sdm->functionctx);CHKERRQ(ierr);
2056     PetscStackPop;
2057     ierr = VecLockPop(x);CHKERRQ(ierr);
2058     ierr = PetscLogEventEnd(SNES_FunctionEval,snes,x,y,0);CHKERRQ(ierr);
2059   } else if (snes->vec_rhs) {
2060     ierr = MatMult(snes->jacobian, x, y);CHKERRQ(ierr);
2061   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetFunction() or SNESSetDM() before SNESComputeFunction(), likely called from SNESSolve().");
2062   if (snes->vec_rhs) {
2063     ierr = VecAXPY(y,-1.0,snes->vec_rhs);CHKERRQ(ierr);
2064   }
2065   snes->nfuncs++;
2066   PetscFunctionReturn(0);
2067 }
2068 
2069 #undef __FUNCT__
2070 #define __FUNCT__ "SNESComputeNGS"
2071 /*@
2072    SNESComputeNGS - Calls the Gauss-Seidel function that has been set with  SNESSetNGS().
2073 
2074    Collective on SNES
2075 
2076    Input Parameters:
2077 +  snes - the SNES context
2078 .  x - input vector
2079 -  b - rhs vector
2080 
2081    Output Parameter:
2082 .  x - new solution vector
2083 
2084    Notes:
2085    SNESComputeNGS() is typically used within composed nonlinear solver
2086    implementations, so most users would not generally call this routine
2087    themselves.
2088 
2089    Level: developer
2090 
2091 .keywords: SNES, nonlinear, compute, function
2092 
2093 .seealso: SNESSetNGS(), SNESComputeFunction()
2094 @*/
2095 PetscErrorCode  SNESComputeNGS(SNES snes,Vec b,Vec x)
2096 {
2097   PetscErrorCode ierr;
2098   DM             dm;
2099   DMSNES         sdm;
2100 
2101   PetscFunctionBegin;
2102   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2103   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
2104   if (b) PetscValidHeaderSpecific(b,VEC_CLASSID,3);
2105   PetscCheckSameComm(snes,1,x,2);
2106   if (b) PetscCheckSameComm(snes,1,b,3);
2107   if (b) {ierr = VecValidValues(b,2,PETSC_TRUE);CHKERRQ(ierr);}
2108   ierr = PetscLogEventBegin(SNES_NGSEval,snes,x,b,0);CHKERRQ(ierr);
2109   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2110   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2111   if (sdm->ops->computegs) {
2112     if (b) {ierr = VecLockPush(b);CHKERRQ(ierr);}
2113     PetscStackPush("SNES user NGS");
2114     ierr = (*sdm->ops->computegs)(snes,x,b,sdm->gsctx);CHKERRQ(ierr);
2115     PetscStackPop;
2116     if (b) {ierr = VecLockPop(b);CHKERRQ(ierr);}
2117   } else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE, "Must call SNESSetNGS() before SNESComputeNGS(), likely called from SNESSolve().");
2118   ierr = PetscLogEventEnd(SNES_NGSEval,snes,x,b,0);CHKERRQ(ierr);
2119   PetscFunctionReturn(0);
2120 }
2121 
2122 #undef __FUNCT__
2123 #define __FUNCT__ "SNESComputeJacobian"
2124 /*@
2125    SNESComputeJacobian - Computes the Jacobian matrix that has been set with SNESSetJacobian().
2126 
2127    Collective on SNES and Mat
2128 
2129    Input Parameters:
2130 +  snes - the SNES context
2131 -  x - input vector
2132 
2133    Output Parameters:
2134 +  A - Jacobian matrix
2135 -  B - optional preconditioning matrix
2136 
2137   Options Database Keys:
2138 +    -snes_lag_preconditioner <lag>
2139 .    -snes_lag_jacobian <lag>
2140 .    -snes_compare_explicit - Compare the computed Jacobian to the finite difference Jacobian and output the differences
2141 .    -snes_compare_explicit_draw  - Compare the computed Jacobian to the finite difference Jacobian and draw the result
2142 .    -snes_compare_explicit_contour  - Compare the computed Jacobian to the finite difference Jacobian and draw a contour plot with the result
2143 .    -snes_compare_operator  - Make the comparison options above use the operator instead of the preconditioning matrix
2144 .    -snes_compare_coloring - Compute the finite differece Jacobian using coloring and display norms of difference
2145 .    -snes_compare_coloring_display - Compute the finite differece Jacobian using coloring and display verbose differences
2146 .    -snes_compare_coloring_threshold - Display only those matrix entries that differ by more than a given threshold
2147 .    -snes_compare_coloring_threshold_atol - Absolute tolerance for difference in matrix entries to be displayed by -snes_compare_coloring_threshold
2148 .    -snes_compare_coloring_threshold_rtol - Relative tolerance for difference in matrix entries to be displayed by -snes_compare_coloring_threshold
2149 .    -snes_compare_coloring_draw - Compute the finite differece Jacobian using coloring and draw differences
2150 -    -snes_compare_coloring_draw_contour - Compute the finite differece Jacobian using coloring and show contours of matrices and differences
2151 
2152 
2153    Notes:
2154    Most users should not need to explicitly call this routine, as it
2155    is used internally within the nonlinear solvers.
2156 
2157    Level: developer
2158 
2159 .keywords: SNES, compute, Jacobian, matrix
2160 
2161 .seealso:  SNESSetJacobian(), KSPSetOperators(), MatStructure, SNESSetLagPreconditioner(), SNESSetLagJacobian()
2162 @*/
2163 PetscErrorCode  SNESComputeJacobian(SNES snes,Vec X,Mat A,Mat B)
2164 {
2165   PetscErrorCode ierr;
2166   PetscBool      flag;
2167   DM             dm;
2168   DMSNES         sdm;
2169   KSP            ksp;
2170 
2171   PetscFunctionBegin;
2172   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2173   PetscValidHeaderSpecific(X,VEC_CLASSID,2);
2174   PetscCheckSameComm(snes,1,X,2);
2175   ierr = VecValidValues(X,2,PETSC_TRUE);CHKERRQ(ierr);
2176   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2177   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2178 
2179   if (!sdm->ops->computejacobian) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_USER,"Must call SNESSetJacobian(), DMSNESSetJacobian(), DMDASNESSetJacobianLocal(), etc");
2180 
2181   /* make sure that MatAssemblyBegin/End() is called on A matrix if it is matrix free */
2182 
2183   if (snes->lagjacobian == -2) {
2184     snes->lagjacobian = -1;
2185 
2186     ierr = PetscInfo(snes,"Recomputing Jacobian/preconditioner because lag is -2 (means compute Jacobian, but then never again) \n");CHKERRQ(ierr);
2187   } else if (snes->lagjacobian == -1) {
2188     ierr = PetscInfo(snes,"Reusing Jacobian/preconditioner because lag is -1\n");CHKERRQ(ierr);
2189     ierr = PetscObjectTypeCompare((PetscObject)A,MATMFFD,&flag);CHKERRQ(ierr);
2190     if (flag) {
2191       ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2192       ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2193     }
2194     PetscFunctionReturn(0);
2195   } else if (snes->lagjacobian > 1 && (snes->iter + snes->jac_iter) % snes->lagjacobian) {
2196     ierr = PetscInfo2(snes,"Reusing Jacobian/preconditioner because lag is %D and SNES iteration is %D\n",snes->lagjacobian,snes->iter);CHKERRQ(ierr);
2197     ierr = PetscObjectTypeCompare((PetscObject)A,MATMFFD,&flag);CHKERRQ(ierr);
2198     if (flag) {
2199       ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2200       ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2201     }
2202     PetscFunctionReturn(0);
2203   }
2204   if (snes->pc && snes->pcside == PC_LEFT) {
2205       ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2206       ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
2207       PetscFunctionReturn(0);
2208   }
2209 
2210   ierr = PetscLogEventBegin(SNES_JacobianEval,snes,X,A,B);CHKERRQ(ierr);
2211   ierr = VecLockPush(X);CHKERRQ(ierr);
2212   PetscStackPush("SNES user Jacobian function");
2213   ierr = (*sdm->ops->computejacobian)(snes,X,A,B,sdm->jacobianctx);CHKERRQ(ierr);
2214   PetscStackPop;
2215   ierr = VecLockPop(X);CHKERRQ(ierr);
2216   ierr = PetscLogEventEnd(SNES_JacobianEval,snes,X,A,B);CHKERRQ(ierr);
2217 
2218   /* the next line ensures that snes->ksp exists */
2219   ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
2220   if (snes->lagpreconditioner == -2) {
2221     ierr = PetscInfo(snes,"Rebuilding preconditioner exactly once since lag is -2\n");CHKERRQ(ierr);
2222     ierr = KSPSetReusePreconditioner(snes->ksp,PETSC_FALSE);CHKERRQ(ierr);
2223     snes->lagpreconditioner = -1;
2224   } else if (snes->lagpreconditioner == -1) {
2225     ierr = PetscInfo(snes,"Reusing preconditioner because lag is -1\n");CHKERRQ(ierr);
2226     ierr = KSPSetReusePreconditioner(snes->ksp,PETSC_TRUE);CHKERRQ(ierr);
2227   } else if (snes->lagpreconditioner > 1 && (snes->iter + snes->pre_iter) % snes->lagpreconditioner) {
2228     ierr = PetscInfo2(snes,"Reusing preconditioner because lag is %D and SNES iteration is %D\n",snes->lagpreconditioner,snes->iter);CHKERRQ(ierr);
2229     ierr = KSPSetReusePreconditioner(snes->ksp,PETSC_TRUE);CHKERRQ(ierr);
2230   } else {
2231     ierr = PetscInfo(snes,"Rebuilding preconditioner\n");CHKERRQ(ierr);
2232     ierr = KSPSetReusePreconditioner(snes->ksp,PETSC_FALSE);CHKERRQ(ierr);
2233   }
2234 
2235   /* make sure user returned a correct Jacobian and preconditioner */
2236   /* PetscValidHeaderSpecific(A,MAT_CLASSID,3);
2237     PetscValidHeaderSpecific(B,MAT_CLASSID,4);   */
2238   {
2239     PetscBool flag = PETSC_FALSE,flag_draw = PETSC_FALSE,flag_contour = PETSC_FALSE,flag_operator = PETSC_FALSE;
2240     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_explicit",&flag,NULL);CHKERRQ(ierr);
2241     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_explicit_draw",&flag_draw,NULL);CHKERRQ(ierr);
2242     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_explicit_draw_contour",&flag_contour,NULL);CHKERRQ(ierr);
2243     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_operator",&flag_operator,NULL);CHKERRQ(ierr);
2244     if (flag || flag_draw || flag_contour) {
2245       Mat          Bexp_mine = NULL,Bexp,FDexp;
2246       PetscViewer  vdraw,vstdout;
2247       PetscBool    flg;
2248       if (flag_operator) {
2249         ierr = MatComputeExplicitOperator(A,&Bexp_mine);CHKERRQ(ierr);
2250         Bexp = Bexp_mine;
2251       } else {
2252         /* See if the preconditioning matrix can be viewed and added directly */
2253         ierr = PetscObjectTypeCompareAny((PetscObject)B,&flg,MATSEQAIJ,MATMPIAIJ,MATSEQDENSE,MATMPIDENSE,MATSEQBAIJ,MATMPIBAIJ,MATSEQSBAIJ,MATMPIBAIJ,"");CHKERRQ(ierr);
2254         if (flg) Bexp = B;
2255         else {
2256           /* If the "preconditioning" matrix is itself MATSHELL or some other type without direct support */
2257           ierr = MatComputeExplicitOperator(B,&Bexp_mine);CHKERRQ(ierr);
2258           Bexp = Bexp_mine;
2259         }
2260       }
2261       ierr = MatConvert(Bexp,MATSAME,MAT_INITIAL_MATRIX,&FDexp);CHKERRQ(ierr);
2262       ierr = SNESComputeJacobianDefault(snes,X,FDexp,FDexp,NULL);CHKERRQ(ierr);
2263       ierr = PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&vstdout);CHKERRQ(ierr);
2264       if (flag_draw || flag_contour) {
2265         ierr = PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),0,"Explicit Jacobians",PETSC_DECIDE,PETSC_DECIDE,300,300,&vdraw);CHKERRQ(ierr);
2266         if (flag_contour) {ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);}
2267       } else vdraw = NULL;
2268       ierr = PetscViewerASCIIPrintf(vstdout,"Explicit %s\n",flag_operator ? "Jacobian" : "preconditioning Jacobian");CHKERRQ(ierr);
2269       if (flag) {ierr = MatView(Bexp,vstdout);CHKERRQ(ierr);}
2270       if (vdraw) {ierr = MatView(Bexp,vdraw);CHKERRQ(ierr);}
2271       ierr = PetscViewerASCIIPrintf(vstdout,"Finite difference Jacobian\n");CHKERRQ(ierr);
2272       if (flag) {ierr = MatView(FDexp,vstdout);CHKERRQ(ierr);}
2273       if (vdraw) {ierr = MatView(FDexp,vdraw);CHKERRQ(ierr);}
2274       ierr = MatAYPX(FDexp,-1.0,Bexp,SAME_NONZERO_PATTERN);CHKERRQ(ierr);
2275       ierr = PetscViewerASCIIPrintf(vstdout,"User-provided matrix minus finite difference Jacobian\n");CHKERRQ(ierr);
2276       if (flag) {ierr = MatView(FDexp,vstdout);CHKERRQ(ierr);}
2277       if (vdraw) {              /* Always use contour for the difference */
2278         ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);
2279         ierr = MatView(FDexp,vdraw);CHKERRQ(ierr);
2280         ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);
2281       }
2282       if (flag_contour) {ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);}
2283       ierr = PetscViewerDestroy(&vdraw);CHKERRQ(ierr);
2284       ierr = MatDestroy(&Bexp_mine);CHKERRQ(ierr);
2285       ierr = MatDestroy(&FDexp);CHKERRQ(ierr);
2286     }
2287   }
2288   {
2289     PetscBool flag = PETSC_FALSE,flag_display = PETSC_FALSE,flag_draw = PETSC_FALSE,flag_contour = PETSC_FALSE,flag_threshold = PETSC_FALSE;
2290     PetscReal threshold_atol = PETSC_SQRT_MACHINE_EPSILON,threshold_rtol = 10*PETSC_SQRT_MACHINE_EPSILON;
2291     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring",&flag,NULL);CHKERRQ(ierr);
2292     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_display",&flag_display,NULL);CHKERRQ(ierr);
2293     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_draw",&flag_draw,NULL);CHKERRQ(ierr);
2294     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_draw_contour",&flag_contour,NULL);CHKERRQ(ierr);
2295     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold",&flag_threshold,NULL);CHKERRQ(ierr);
2296     ierr = PetscOptionsGetReal(((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold_rtol",&threshold_rtol,NULL);CHKERRQ(ierr);
2297     ierr = PetscOptionsGetReal(((PetscObject)snes)->prefix,"-snes_compare_coloring_threshold_atol",&threshold_atol,NULL);CHKERRQ(ierr);
2298     if (flag || flag_display || flag_draw || flag_contour || flag_threshold) {
2299       Mat            Bfd;
2300       PetscViewer    vdraw,vstdout;
2301       MatColoring    coloring;
2302       ISColoring     iscoloring;
2303       MatFDColoring  matfdcoloring;
2304       PetscErrorCode (*func)(SNES,Vec,Vec,void*);
2305       void           *funcctx;
2306       PetscReal      norm1,norm2,normmax;
2307 
2308       ierr = MatDuplicate(B,MAT_DO_NOT_COPY_VALUES,&Bfd);CHKERRQ(ierr);
2309       ierr = MatColoringCreate(Bfd,&coloring);CHKERRQ(ierr);
2310       ierr = MatColoringSetType(coloring,MATCOLORINGSL);CHKERRQ(ierr);
2311       ierr = MatColoringSetFromOptions(coloring);CHKERRQ(ierr);
2312       ierr = MatColoringApply(coloring,&iscoloring);CHKERRQ(ierr);
2313       ierr = MatColoringDestroy(&coloring);CHKERRQ(ierr);
2314       ierr = MatFDColoringCreate(Bfd,iscoloring,&matfdcoloring);CHKERRQ(ierr);
2315       ierr = MatFDColoringSetFromOptions(matfdcoloring);CHKERRQ(ierr);
2316       ierr = MatFDColoringSetUp(Bfd,iscoloring,matfdcoloring);CHKERRQ(ierr);
2317       ierr = ISColoringDestroy(&iscoloring);CHKERRQ(ierr);
2318 
2319       /* This method of getting the function is currently unreliable since it doesn't work for DM local functions. */
2320       ierr = SNESGetFunction(snes,NULL,&func,&funcctx);CHKERRQ(ierr);
2321       ierr = MatFDColoringSetFunction(matfdcoloring,(PetscErrorCode (*)(void))func,funcctx);CHKERRQ(ierr);
2322       ierr = PetscObjectSetOptionsPrefix((PetscObject)matfdcoloring,((PetscObject)snes)->prefix);CHKERRQ(ierr);
2323       ierr = PetscObjectAppendOptionsPrefix((PetscObject)matfdcoloring,"coloring_");CHKERRQ(ierr);
2324       ierr = MatFDColoringSetFromOptions(matfdcoloring);CHKERRQ(ierr);
2325       ierr = MatFDColoringApply(Bfd,matfdcoloring,X,snes);CHKERRQ(ierr);
2326       ierr = MatFDColoringDestroy(&matfdcoloring);CHKERRQ(ierr);
2327 
2328       ierr = PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)snes),&vstdout);CHKERRQ(ierr);
2329       if (flag_draw || flag_contour) {
2330         ierr = PetscViewerDrawOpen(PetscObjectComm((PetscObject)snes),0,"Colored Jacobians",PETSC_DECIDE,PETSC_DECIDE,300,300,&vdraw);CHKERRQ(ierr);
2331         if (flag_contour) {ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);}
2332       } else vdraw = NULL;
2333       ierr = PetscViewerASCIIPrintf(vstdout,"Explicit preconditioning Jacobian\n");CHKERRQ(ierr);
2334       if (flag_display) {ierr = MatView(B,vstdout);CHKERRQ(ierr);}
2335       if (vdraw) {ierr = MatView(B,vdraw);CHKERRQ(ierr);}
2336       ierr = PetscViewerASCIIPrintf(vstdout,"Colored Finite difference Jacobian\n");CHKERRQ(ierr);
2337       if (flag_display) {ierr = MatView(Bfd,vstdout);CHKERRQ(ierr);}
2338       if (vdraw) {ierr = MatView(Bfd,vdraw);CHKERRQ(ierr);}
2339       ierr = MatAYPX(Bfd,-1.0,B,SAME_NONZERO_PATTERN);CHKERRQ(ierr);
2340       ierr = MatNorm(Bfd,NORM_1,&norm1);CHKERRQ(ierr);
2341       ierr = MatNorm(Bfd,NORM_FROBENIUS,&norm2);CHKERRQ(ierr);
2342       ierr = MatNorm(Bfd,NORM_MAX,&normmax);CHKERRQ(ierr);
2343       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);
2344       if (flag_display) {ierr = MatView(Bfd,vstdout);CHKERRQ(ierr);}
2345       if (vdraw) {              /* Always use contour for the difference */
2346         ierr = PetscViewerPushFormat(vdraw,PETSC_VIEWER_DRAW_CONTOUR);CHKERRQ(ierr);
2347         ierr = MatView(Bfd,vdraw);CHKERRQ(ierr);
2348         ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);
2349       }
2350       if (flag_contour) {ierr = PetscViewerPopFormat(vdraw);CHKERRQ(ierr);}
2351 
2352       if (flag_threshold) {
2353         PetscInt bs,rstart,rend,i;
2354         ierr = MatGetBlockSize(B,&bs);CHKERRQ(ierr);
2355         ierr = MatGetOwnershipRange(B,&rstart,&rend);CHKERRQ(ierr);
2356         for (i=rstart; i<rend; i++) {
2357           const PetscScalar *ba,*ca;
2358           const PetscInt    *bj,*cj;
2359           PetscInt          bn,cn,j,maxentrycol = -1,maxdiffcol = -1,maxrdiffcol = -1;
2360           PetscReal         maxentry = 0,maxdiff = 0,maxrdiff = 0;
2361           ierr = MatGetRow(B,i,&bn,&bj,&ba);CHKERRQ(ierr);
2362           ierr = MatGetRow(Bfd,i,&cn,&cj,&ca);CHKERRQ(ierr);
2363           if (bn != cn) SETERRQ(((PetscObject)A)->comm,PETSC_ERR_PLIB,"Unexpected different nonzero pattern in -snes_compare_coloring_threshold");
2364           for (j=0; j<bn; j++) {
2365             PetscReal rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol*PetscAbsScalar(ba[j]));
2366             if (PetscAbsScalar(ba[j]) > PetscAbs(maxentry)) {
2367               maxentrycol = bj[j];
2368               maxentry    = PetscRealPart(ba[j]);
2369             }
2370             if (PetscAbsScalar(ca[j]) > PetscAbs(maxdiff)) {
2371               maxdiffcol = bj[j];
2372               maxdiff    = PetscRealPart(ca[j]);
2373             }
2374             if (rdiff > maxrdiff) {
2375               maxrdiffcol = bj[j];
2376               maxrdiff    = rdiff;
2377             }
2378           }
2379           if (maxrdiff > 1) {
2380             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);
2381             for (j=0; j<bn; j++) {
2382               PetscReal rdiff;
2383               rdiff = PetscAbsScalar(ca[j]) / (threshold_atol + threshold_rtol*PetscAbsScalar(ba[j]));
2384               if (rdiff > 1) {
2385                 ierr = PetscViewerASCIIPrintf(vstdout," (%D,%g:%g)",bj[j],(double)PetscRealPart(ba[j]),(double)PetscRealPart(ca[j]));CHKERRQ(ierr);
2386               }
2387             }
2388             ierr = PetscViewerASCIIPrintf(vstdout,"\n",i,maxentry,maxdiff,maxrdiff);CHKERRQ(ierr);
2389           }
2390           ierr = MatRestoreRow(B,i,&bn,&bj,&ba);CHKERRQ(ierr);
2391           ierr = MatRestoreRow(Bfd,i,&cn,&cj,&ca);CHKERRQ(ierr);
2392         }
2393       }
2394       ierr = PetscViewerDestroy(&vdraw);CHKERRQ(ierr);
2395       ierr = MatDestroy(&Bfd);CHKERRQ(ierr);
2396     }
2397   }
2398   PetscFunctionReturn(0);
2399 }
2400 
2401 /*MC
2402     SNESJacobianFunction - Function used to convey the nonlinear Jacobian of the function to be solved by SNES
2403 
2404      Synopsis:
2405      #include "petscsnes.h"
2406      PetscErrorCode SNESJacobianFunction(SNES snes,Vec x,Mat Amat,Mat Pmat,void *ctx);
2407 
2408 +  x - input vector
2409 .  Amat - the matrix that defines the (approximate) Jacobian
2410 .  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.
2411 -  ctx - [optional] user-defined Jacobian context
2412 
2413    Level: intermediate
2414 
2415 .seealso:   SNESSetFunction(), SNESGetFunction(), SNESSetJacobian(), SNESGetJacobian()
2416 M*/
2417 
2418 #undef __FUNCT__
2419 #define __FUNCT__ "SNESSetJacobian"
2420 /*@C
2421    SNESSetJacobian - Sets the function to compute Jacobian as well as the
2422    location to store the matrix.
2423 
2424    Logically Collective on SNES and Mat
2425 
2426    Input Parameters:
2427 +  snes - the SNES context
2428 .  Amat - the matrix that defines the (approximate) Jacobian
2429 .  Pmat - the matrix to be used in constructing the preconditioner, usually the same as Amat.
2430 .  J - Jacobian evaluation routine (if NULL then SNES retains any previously set value), see SNESJacobianFunction for details
2431 -  ctx - [optional] user-defined context for private data for the
2432          Jacobian evaluation routine (may be NULL) (if NULL then SNES retains any previously set value)
2433 
2434    Notes:
2435    If the Amat matrix and Pmat matrix are different you must call MatAssemblyBegin/End() on
2436    each matrix.
2437 
2438    If using SNESComputeJacobianDefaultColor() to assemble a Jacobian, the ctx argument
2439    must be a MatFDColoring.
2440 
2441    Other defect-correction schemes can be used by computing a different matrix in place of the Jacobian.  One common
2442    example is to use the "Picard linearization" which only differentiates through the highest order parts of each term.
2443 
2444    Level: beginner
2445 
2446 .keywords: SNES, nonlinear, set, Jacobian, matrix
2447 
2448 .seealso: KSPSetOperators(), SNESSetFunction(), MatMFFDComputeJacobian(), SNESComputeJacobianDefaultColor(), MatStructure, J,
2449           SNESSetPicard(), SNESJacobianFunction
2450 @*/
2451 PetscErrorCode  SNESSetJacobian(SNES snes,Mat Amat,Mat Pmat,PetscErrorCode (*J)(SNES,Vec,Mat,Mat,void*),void *ctx)
2452 {
2453   PetscErrorCode ierr;
2454   DM             dm;
2455 
2456   PetscFunctionBegin;
2457   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2458   if (Amat) PetscValidHeaderSpecific(Amat,MAT_CLASSID,2);
2459   if (Pmat) PetscValidHeaderSpecific(Pmat,MAT_CLASSID,3);
2460   if (Amat) PetscCheckSameComm(snes,1,Amat,2);
2461   if (Pmat) PetscCheckSameComm(snes,1,Pmat,3);
2462   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2463   ierr = DMSNESSetJacobian(dm,J,ctx);CHKERRQ(ierr);
2464   if (Amat) {
2465     ierr = PetscObjectReference((PetscObject)Amat);CHKERRQ(ierr);
2466     ierr = MatDestroy(&snes->jacobian);CHKERRQ(ierr);
2467 
2468     snes->jacobian = Amat;
2469   }
2470   if (Pmat) {
2471     ierr = PetscObjectReference((PetscObject)Pmat);CHKERRQ(ierr);
2472     ierr = MatDestroy(&snes->jacobian_pre);CHKERRQ(ierr);
2473 
2474     snes->jacobian_pre = Pmat;
2475   }
2476   PetscFunctionReturn(0);
2477 }
2478 
2479 #undef __FUNCT__
2480 #define __FUNCT__ "SNESGetJacobian"
2481 /*@C
2482    SNESGetJacobian - Returns the Jacobian matrix and optionally the user
2483    provided context for evaluating the Jacobian.
2484 
2485    Not Collective, but Mat object will be parallel if SNES object is
2486 
2487    Input Parameter:
2488 .  snes - the nonlinear solver context
2489 
2490    Output Parameters:
2491 +  Amat - location to stash (approximate) Jacobian matrix (or NULL)
2492 .  Pmat - location to stash matrix used to compute the preconditioner (or NULL)
2493 .  J - location to put Jacobian function (or NULL), see SNESJacobianFunction for details on its calling sequence
2494 -  ctx - location to stash Jacobian ctx (or NULL)
2495 
2496    Level: advanced
2497 
2498 .seealso: SNESSetJacobian(), SNESComputeJacobian(), SNESJacobianFunction, SNESGetFunction()
2499 @*/
2500 PetscErrorCode SNESGetJacobian(SNES snes,Mat *Amat,Mat *Pmat,PetscErrorCode (**J)(SNES,Vec,Mat,Mat,void*),void **ctx)
2501 {
2502   PetscErrorCode ierr;
2503   DM             dm;
2504   DMSNES         sdm;
2505 
2506   PetscFunctionBegin;
2507   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2508   if (Amat) *Amat = snes->jacobian;
2509   if (Pmat) *Pmat = snes->jacobian_pre;
2510   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2511   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2512   if (J) *J = sdm->ops->computejacobian;
2513   if (ctx) *ctx = sdm->jacobianctx;
2514   PetscFunctionReturn(0);
2515 }
2516 
2517 #undef __FUNCT__
2518 #define __FUNCT__ "SNESSetUp"
2519 /*@
2520    SNESSetUp - Sets up the internal data structures for the later use
2521    of a nonlinear solver.
2522 
2523    Collective on SNES
2524 
2525    Input Parameters:
2526 .  snes - the SNES context
2527 
2528    Notes:
2529    For basic use of the SNES solvers the user need not explicitly call
2530    SNESSetUp(), since these actions will automatically occur during
2531    the call to SNESSolve().  However, if one wishes to control this
2532    phase separately, SNESSetUp() should be called after SNESCreate()
2533    and optional routines of the form SNESSetXXX(), but before SNESSolve().
2534 
2535    Level: advanced
2536 
2537 .keywords: SNES, nonlinear, setup
2538 
2539 .seealso: SNESCreate(), SNESSolve(), SNESDestroy()
2540 @*/
2541 PetscErrorCode  SNESSetUp(SNES snes)
2542 {
2543   PetscErrorCode ierr;
2544   DM             dm;
2545   DMSNES         sdm;
2546   SNESLineSearch linesearch, pclinesearch;
2547   void           *lsprectx,*lspostctx;
2548   PetscErrorCode (*precheck)(SNESLineSearch,Vec,Vec,PetscBool*,void*);
2549   PetscErrorCode (*postcheck)(SNESLineSearch,Vec,Vec,Vec,PetscBool*,PetscBool*,void*);
2550   PetscErrorCode (*func)(SNES,Vec,Vec,void*);
2551   Vec            f,fpc;
2552   void           *funcctx;
2553   PetscErrorCode (*jac)(SNES,Vec,Mat,Mat,void*);
2554   void           *jacctx,*appctx;
2555   Mat            j,jpre;
2556 
2557   PetscFunctionBegin;
2558   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2559   if (snes->setupcalled) PetscFunctionReturn(0);
2560 
2561   if (!((PetscObject)snes)->type_name) {
2562     ierr = SNESSetType(snes,SNESNEWTONLS);CHKERRQ(ierr);
2563   }
2564 
2565   ierr = SNESGetFunction(snes,&snes->vec_func,NULL,NULL);CHKERRQ(ierr);
2566 
2567   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2568   ierr = DMGetDMSNES(dm,&sdm);CHKERRQ(ierr);
2569   if (!sdm->ops->computefunction) SETERRQ(PetscObjectComm((PetscObject)dm),PETSC_ERR_ARG_WRONGSTATE,"Function never provided to SNES object");
2570   if (!sdm->ops->computejacobian) {
2571     ierr = DMSNESSetJacobian(dm,SNESComputeJacobianDefaultColor,NULL);CHKERRQ(ierr);
2572   }
2573   if (!snes->vec_func) {
2574     ierr = DMCreateGlobalVector(dm,&snes->vec_func);CHKERRQ(ierr);
2575   }
2576 
2577   if (!snes->ksp) {
2578     ierr = SNESGetKSP(snes, &snes->ksp);CHKERRQ(ierr);
2579   }
2580 
2581   if (!snes->linesearch) {
2582     ierr = SNESGetLineSearch(snes, &snes->linesearch);CHKERRQ(ierr);
2583   }
2584   ierr = SNESLineSearchSetFunction(snes->linesearch,SNESComputeFunction);CHKERRQ(ierr);
2585 
2586   if (snes->pc && (snes->pcside == PC_LEFT)) {
2587     snes->mf          = PETSC_TRUE;
2588     snes->mf_operator = PETSC_FALSE;
2589   }
2590 
2591   if (snes->pc) {
2592     /* copy the DM over */
2593     ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
2594     ierr = SNESSetDM(snes->pc,dm);CHKERRQ(ierr);
2595 
2596     ierr = SNESGetFunction(snes,&f,&func,&funcctx);CHKERRQ(ierr);
2597     ierr = VecDuplicate(f,&fpc);CHKERRQ(ierr);
2598     ierr = SNESSetFunction(snes->pc,fpc,func,funcctx);CHKERRQ(ierr);
2599     ierr = SNESGetJacobian(snes,&j,&jpre,&jac,&jacctx);CHKERRQ(ierr);
2600     ierr = SNESSetJacobian(snes->pc,j,jpre,jac,jacctx);CHKERRQ(ierr);
2601     ierr = SNESGetApplicationContext(snes,&appctx);CHKERRQ(ierr);
2602     ierr = SNESSetApplicationContext(snes->pc,appctx);CHKERRQ(ierr);
2603     ierr = VecDestroy(&fpc);CHKERRQ(ierr);
2604 
2605     /* copy the function pointers over */
2606     ierr = PetscObjectCopyFortranFunctionPointers((PetscObject)snes,(PetscObject)snes->pc);CHKERRQ(ierr);
2607 
2608     /* default to 1 iteration */
2609     ierr = SNESSetTolerances(snes->pc,0.0,0.0,0.0,1,snes->pc->max_funcs);CHKERRQ(ierr);
2610     if (snes->pcside==PC_RIGHT) {
2611       ierr = SNESSetNormSchedule(snes->pc,SNES_NORM_FINAL_ONLY);CHKERRQ(ierr);
2612     } else {
2613       ierr = SNESSetNormSchedule(snes->pc,SNES_NORM_NONE);CHKERRQ(ierr);
2614     }
2615     ierr = SNESSetFromOptions(snes->pc);CHKERRQ(ierr);
2616 
2617     /* copy the line search context over */
2618     ierr = SNESGetLineSearch(snes,&linesearch);CHKERRQ(ierr);
2619     ierr = SNESGetLineSearch(snes->pc,&pclinesearch);CHKERRQ(ierr);
2620     ierr = SNESLineSearchGetPreCheck(linesearch,&precheck,&lsprectx);CHKERRQ(ierr);
2621     ierr = SNESLineSearchGetPostCheck(linesearch,&postcheck,&lspostctx);CHKERRQ(ierr);
2622     ierr = SNESLineSearchSetPreCheck(pclinesearch,precheck,lsprectx);CHKERRQ(ierr);
2623     ierr = SNESLineSearchSetPostCheck(pclinesearch,postcheck,lspostctx);CHKERRQ(ierr);
2624     ierr = PetscObjectCopyFortranFunctionPointers((PetscObject)linesearch, (PetscObject)pclinesearch);CHKERRQ(ierr);
2625   }
2626   if (snes->mf) {
2627     ierr = SNESSetUpMatrixFree_Private(snes, snes->mf_operator, snes->mf_version);CHKERRQ(ierr);
2628   }
2629   if (snes->ops->usercompute && !snes->user) {
2630     ierr = (*snes->ops->usercompute)(snes,(void**)&snes->user);CHKERRQ(ierr);
2631   }
2632 
2633   snes->jac_iter = 0;
2634   snes->pre_iter = 0;
2635 
2636   if (snes->ops->setup) {
2637     ierr = (*snes->ops->setup)(snes);CHKERRQ(ierr);
2638   }
2639 
2640   if (snes->pc && (snes->pcside == PC_LEFT)) {
2641     if (snes->functype == SNES_FUNCTION_PRECONDITIONED) {
2642       ierr = SNESGetLineSearch(snes,&linesearch);CHKERRQ(ierr);
2643       ierr = SNESLineSearchSetFunction(linesearch,SNESComputeFunctionDefaultNPC);CHKERRQ(ierr);
2644     }
2645   }
2646 
2647   snes->setupcalled = PETSC_TRUE;
2648   PetscFunctionReturn(0);
2649 }
2650 
2651 #undef __FUNCT__
2652 #define __FUNCT__ "SNESReset"
2653 /*@
2654    SNESReset - Resets a SNES context to the snessetupcalled = 0 state and removes any allocated Vecs and Mats
2655 
2656    Collective on SNES
2657 
2658    Input Parameter:
2659 .  snes - iterative context obtained from SNESCreate()
2660 
2661    Level: intermediate
2662 
2663    Notes: Also calls the application context destroy routine set with SNESSetComputeApplicationContext()
2664 
2665 .keywords: SNES, destroy
2666 
2667 .seealso: SNESCreate(), SNESSetUp(), SNESSolve()
2668 @*/
2669 PetscErrorCode  SNESReset(SNES snes)
2670 {
2671   PetscErrorCode ierr;
2672 
2673   PetscFunctionBegin;
2674   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2675   if (snes->ops->userdestroy && snes->user) {
2676     ierr       = (*snes->ops->userdestroy)((void**)&snes->user);CHKERRQ(ierr);
2677     snes->user = NULL;
2678   }
2679   if (snes->pc) {
2680     ierr = SNESReset(snes->pc);CHKERRQ(ierr);
2681   }
2682 
2683   if (snes->ops->reset) {
2684     ierr = (*snes->ops->reset)(snes);CHKERRQ(ierr);
2685   }
2686   if (snes->ksp) {
2687     ierr = KSPReset(snes->ksp);CHKERRQ(ierr);
2688   }
2689 
2690   if (snes->linesearch) {
2691     ierr = SNESLineSearchReset(snes->linesearch);CHKERRQ(ierr);
2692   }
2693 
2694   ierr = VecDestroy(&snes->vec_rhs);CHKERRQ(ierr);
2695   ierr = VecDestroy(&snes->vec_sol);CHKERRQ(ierr);
2696   ierr = VecDestroy(&snes->vec_sol_update);CHKERRQ(ierr);
2697   ierr = VecDestroy(&snes->vec_func);CHKERRQ(ierr);
2698   ierr = MatDestroy(&snes->jacobian);CHKERRQ(ierr);
2699   ierr = MatDestroy(&snes->jacobian_pre);CHKERRQ(ierr);
2700   ierr = VecDestroyVecs(snes->nwork,&snes->work);CHKERRQ(ierr);
2701   ierr = VecDestroyVecs(snes->nvwork,&snes->vwork);CHKERRQ(ierr);
2702 
2703   snes->nwork       = snes->nvwork = 0;
2704   snes->setupcalled = PETSC_FALSE;
2705   PetscFunctionReturn(0);
2706 }
2707 
2708 #undef __FUNCT__
2709 #define __FUNCT__ "SNESDestroy"
2710 /*@
2711    SNESDestroy - Destroys the nonlinear solver context that was created
2712    with SNESCreate().
2713 
2714    Collective on SNES
2715 
2716    Input Parameter:
2717 .  snes - the SNES context
2718 
2719    Level: beginner
2720 
2721 .keywords: SNES, nonlinear, destroy
2722 
2723 .seealso: SNESCreate(), SNESSolve()
2724 @*/
2725 PetscErrorCode  SNESDestroy(SNES *snes)
2726 {
2727   PetscErrorCode ierr;
2728 
2729   PetscFunctionBegin;
2730   if (!*snes) PetscFunctionReturn(0);
2731   PetscValidHeaderSpecific((*snes),SNES_CLASSID,1);
2732   if (--((PetscObject)(*snes))->refct > 0) {*snes = 0; PetscFunctionReturn(0);}
2733 
2734   ierr = SNESReset((*snes));CHKERRQ(ierr);
2735   ierr = SNESDestroy(&(*snes)->pc);CHKERRQ(ierr);
2736 
2737   /* if memory was published with SAWs then destroy it */
2738   ierr = PetscObjectSAWsViewOff((PetscObject)*snes);CHKERRQ(ierr);
2739   if ((*snes)->ops->destroy) {ierr = (*((*snes))->ops->destroy)((*snes));CHKERRQ(ierr);}
2740 
2741   ierr = DMDestroy(&(*snes)->dm);CHKERRQ(ierr);
2742   ierr = KSPDestroy(&(*snes)->ksp);CHKERRQ(ierr);
2743   ierr = SNESLineSearchDestroy(&(*snes)->linesearch);CHKERRQ(ierr);
2744 
2745   ierr = PetscFree((*snes)->kspconvctx);CHKERRQ(ierr);
2746   if ((*snes)->ops->convergeddestroy) {
2747     ierr = (*(*snes)->ops->convergeddestroy)((*snes)->cnvP);CHKERRQ(ierr);
2748   }
2749   if ((*snes)->conv_malloc) {
2750     ierr = PetscFree((*snes)->conv_hist);CHKERRQ(ierr);
2751     ierr = PetscFree((*snes)->conv_hist_its);CHKERRQ(ierr);
2752   }
2753   ierr = SNESMonitorCancel((*snes));CHKERRQ(ierr);
2754   ierr = PetscHeaderDestroy(snes);CHKERRQ(ierr);
2755   PetscFunctionReturn(0);
2756 }
2757 
2758 /* ----------- Routines to set solver parameters ---------- */
2759 
2760 #undef __FUNCT__
2761 #define __FUNCT__ "SNESSetLagPreconditioner"
2762 /*@
2763    SNESSetLagPreconditioner - Determines when the preconditioner is rebuilt in the nonlinear solve.
2764 
2765    Logically Collective on SNES
2766 
2767    Input Parameters:
2768 +  snes - the SNES context
2769 -  lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2770          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that
2771 
2772    Options Database Keys:
2773 .    -snes_lag_preconditioner <lag>
2774 
2775    Notes:
2776    The default is 1
2777    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2778    If  -1 is used before the very first nonlinear solve the preconditioner is still built because there is no previous preconditioner to use
2779 
2780    Level: intermediate
2781 
2782 .keywords: SNES, nonlinear, set, convergence, tolerances
2783 
2784 .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian()
2785 
2786 @*/
2787 PetscErrorCode  SNESSetLagPreconditioner(SNES snes,PetscInt lag)
2788 {
2789   PetscFunctionBegin;
2790   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2791   if (lag < -2) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag must be -2, -1, 1 or greater");
2792   if (!lag) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag cannot be 0");
2793   PetscValidLogicalCollectiveInt(snes,lag,2);
2794   snes->lagpreconditioner = lag;
2795   PetscFunctionReturn(0);
2796 }
2797 
2798 #undef __FUNCT__
2799 #define __FUNCT__ "SNESSetGridSequence"
2800 /*@
2801    SNESSetGridSequence - sets the number of steps of grid sequencing that SNES does
2802 
2803    Logically Collective on SNES
2804 
2805    Input Parameters:
2806 +  snes - the SNES context
2807 -  steps - the number of refinements to do, defaults to 0
2808 
2809    Options Database Keys:
2810 .    -snes_grid_sequence <steps>
2811 
2812    Level: intermediate
2813 
2814    Notes:
2815    Use SNESGetSolution() to extract the fine grid solution after grid sequencing.
2816 
2817 .keywords: SNES, nonlinear, set, convergence, tolerances
2818 
2819 .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagJacobian(), SNESGetLagJacobian()
2820 
2821 @*/
2822 PetscErrorCode  SNESSetGridSequence(SNES snes,PetscInt steps)
2823 {
2824   PetscFunctionBegin;
2825   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2826   PetscValidLogicalCollectiveInt(snes,steps,2);
2827   snes->gridsequence = steps;
2828   PetscFunctionReturn(0);
2829 }
2830 
2831 #undef __FUNCT__
2832 #define __FUNCT__ "SNESGetLagPreconditioner"
2833 /*@
2834    SNESGetLagPreconditioner - Indicates how often the preconditioner is rebuilt
2835 
2836    Not Collective
2837 
2838    Input Parameter:
2839 .  snes - the SNES context
2840 
2841    Output Parameter:
2842 .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2843          the Jacobian is built etc. -2 indicates rebuild preconditioner at next chance but then never rebuild after that
2844 
2845    Options Database Keys:
2846 .    -snes_lag_preconditioner <lag>
2847 
2848    Notes:
2849    The default is 1
2850    The preconditioner is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2851 
2852    Level: intermediate
2853 
2854 .keywords: SNES, nonlinear, set, convergence, tolerances
2855 
2856 .seealso: SNESSetTrustRegionTolerance(), SNESSetLagPreconditioner()
2857 
2858 @*/
2859 PetscErrorCode  SNESGetLagPreconditioner(SNES snes,PetscInt *lag)
2860 {
2861   PetscFunctionBegin;
2862   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2863   *lag = snes->lagpreconditioner;
2864   PetscFunctionReturn(0);
2865 }
2866 
2867 #undef __FUNCT__
2868 #define __FUNCT__ "SNESSetLagJacobian"
2869 /*@
2870    SNESSetLagJacobian - Determines when the Jacobian is rebuilt in the nonlinear solve. See SNESSetLagPreconditioner() for determining how
2871      often the preconditioner is rebuilt.
2872 
2873    Logically Collective on SNES
2874 
2875    Input Parameters:
2876 +  snes - the SNES context
2877 -  lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2878          the Jacobian is built etc. -2 means rebuild at next chance but then never again
2879 
2880    Options Database Keys:
2881 .    -snes_lag_jacobian <lag>
2882 
2883    Notes:
2884    The default is 1
2885    The Jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2886    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
2887    at the next Newton step but never again (unless it is reset to another value)
2888 
2889    Level: intermediate
2890 
2891 .keywords: SNES, nonlinear, set, convergence, tolerances
2892 
2893 .seealso: SNESSetTrustRegionTolerance(), SNESGetLagPreconditioner(), SNESSetLagPreconditioner(), SNESGetLagJacobian()
2894 
2895 @*/
2896 PetscErrorCode  SNESSetLagJacobian(SNES snes,PetscInt lag)
2897 {
2898   PetscFunctionBegin;
2899   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2900   if (lag < -2) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag must be -2, -1, 1 or greater");
2901   if (!lag) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Lag cannot be 0");
2902   PetscValidLogicalCollectiveInt(snes,lag,2);
2903   snes->lagjacobian = lag;
2904   PetscFunctionReturn(0);
2905 }
2906 
2907 #undef __FUNCT__
2908 #define __FUNCT__ "SNESGetLagJacobian"
2909 /*@
2910    SNESGetLagJacobian - Indicates how often the Jacobian is rebuilt. See SNESGetLagPreconditioner() to determine when the preconditioner is rebuilt
2911 
2912    Not Collective
2913 
2914    Input Parameter:
2915 .  snes - the SNES context
2916 
2917    Output Parameter:
2918 .   lag - -1 indicates NEVER rebuild, 1 means rebuild every time the Jacobian is computed within a single nonlinear solve, 2 means every second time
2919          the Jacobian is built etc.
2920 
2921    Options Database Keys:
2922 .    -snes_lag_jacobian <lag>
2923 
2924    Notes:
2925    The default is 1
2926    The jacobian is ALWAYS built in the first iteration of a nonlinear solve unless lag is -1
2927 
2928    Level: intermediate
2929 
2930 .keywords: SNES, nonlinear, set, convergence, tolerances
2931 
2932 .seealso: SNESSetTrustRegionTolerance(), SNESSetLagJacobian(), SNESSetLagPreconditioner(), SNESGetLagPreconditioner()
2933 
2934 @*/
2935 PetscErrorCode  SNESGetLagJacobian(SNES snes,PetscInt *lag)
2936 {
2937   PetscFunctionBegin;
2938   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2939   *lag = snes->lagjacobian;
2940   PetscFunctionReturn(0);
2941 }
2942 
2943 #undef __FUNCT__
2944 #define __FUNCT__ "SNESSetLagJacobianPersists"
2945 /*@
2946    SNESSetLagJacobianPersists - Set whether or not the Jacobian lagging persists through multiple solves
2947 
2948    Logically collective on SNES
2949 
2950    Input Parameter:
2951 +  snes - the SNES context
2952 -   flg - jacobian lagging persists if true
2953 
2954    Options Database Keys:
2955 .    -snes_lag_jacobian_persists <flg>
2956 
2957    Notes: This is useful both for nonlinear preconditioning, where it's appropriate to have the Jacobian be stale by
2958    several solves, and for implicit time-stepping, where Jacobian lagging in the inner nonlinear solve over several
2959    timesteps may present huge efficiency gains.
2960 
2961    Level: developer
2962 
2963 .keywords: SNES, nonlinear, lag
2964 
2965 .seealso: SNESSetLagPreconditionerPersists(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetNPC()
2966 
2967 @*/
2968 PetscErrorCode  SNESSetLagJacobianPersists(SNES snes,PetscBool flg)
2969 {
2970   PetscFunctionBegin;
2971   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
2972   PetscValidLogicalCollectiveBool(snes,flg,2);
2973   snes->lagjac_persist = flg;
2974   PetscFunctionReturn(0);
2975 }
2976 
2977 #undef __FUNCT__
2978 #define __FUNCT__ "SNESSetLagPreconditionerPersists"
2979 /*@
2980    SNESSetLagPreconditionerPersists - Set whether or not the preconditioner lagging persists through multiple solves
2981 
2982    Logically Collective on SNES
2983 
2984    Input Parameter:
2985 +  snes - the SNES context
2986 -   flg - preconditioner lagging persists if true
2987 
2988    Options Database Keys:
2989 .    -snes_lag_jacobian_persists <flg>
2990 
2991    Notes: This is useful both for nonlinear preconditioning, where it's appropriate to have the preconditioner be stale
2992    by several solves, and for implicit time-stepping, where preconditioner lagging in the inner nonlinear solve over
2993    several timesteps may present huge efficiency gains.
2994 
2995    Level: developer
2996 
2997 .keywords: SNES, nonlinear, lag
2998 
2999 .seealso: SNESSetLagJacobianPersists(), SNESSetLagJacobian(), SNESGetLagJacobian(), SNESGetNPC()
3000 
3001 @*/
3002 PetscErrorCode  SNESSetLagPreconditionerPersists(SNES snes,PetscBool flg)
3003 {
3004   PetscFunctionBegin;
3005   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3006   PetscValidLogicalCollectiveBool(snes,flg,2);
3007   snes->lagpre_persist = flg;
3008   PetscFunctionReturn(0);
3009 }
3010 
3011 #undef __FUNCT__
3012 #define __FUNCT__ "SNESSetTolerances"
3013 /*@
3014    SNESSetTolerances - Sets various parameters used in convergence tests.
3015 
3016    Logically Collective on SNES
3017 
3018    Input Parameters:
3019 +  snes - the SNES context
3020 .  abstol - absolute convergence tolerance
3021 .  rtol - relative convergence tolerance
3022 .  stol -  convergence tolerance in terms of the norm of the change in the solution between steps,  || delta x || < stol*|| x ||
3023 .  maxit - maximum number of iterations
3024 -  maxf - maximum number of function evaluations
3025 
3026    Options Database Keys:
3027 +    -snes_atol <abstol> - Sets abstol
3028 .    -snes_rtol <rtol> - Sets rtol
3029 .    -snes_stol <stol> - Sets stol
3030 .    -snes_max_it <maxit> - Sets maxit
3031 -    -snes_max_funcs <maxf> - Sets maxf
3032 
3033    Notes:
3034    The default maximum number of iterations is 50.
3035    The default maximum number of function evaluations is 1000.
3036 
3037    Level: intermediate
3038 
3039 .keywords: SNES, nonlinear, set, convergence, tolerances
3040 
3041 .seealso: SNESSetTrustRegionTolerance()
3042 @*/
3043 PetscErrorCode  SNESSetTolerances(SNES snes,PetscReal abstol,PetscReal rtol,PetscReal stol,PetscInt maxit,PetscInt maxf)
3044 {
3045   PetscFunctionBegin;
3046   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3047   PetscValidLogicalCollectiveReal(snes,abstol,2);
3048   PetscValidLogicalCollectiveReal(snes,rtol,3);
3049   PetscValidLogicalCollectiveReal(snes,stol,4);
3050   PetscValidLogicalCollectiveInt(snes,maxit,5);
3051   PetscValidLogicalCollectiveInt(snes,maxf,6);
3052 
3053   if (abstol != PETSC_DEFAULT) {
3054     if (abstol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Absolute tolerance %g must be non-negative",(double)abstol);
3055     snes->abstol = abstol;
3056   }
3057   if (rtol != PETSC_DEFAULT) {
3058     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);
3059     snes->rtol = rtol;
3060   }
3061   if (stol != PETSC_DEFAULT) {
3062     if (stol < 0.0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Step tolerance %g must be non-negative",(double)stol);
3063     snes->stol = stol;
3064   }
3065   if (maxit != PETSC_DEFAULT) {
3066     if (maxit < 0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Maximum number of iterations %D must be non-negative",maxit);
3067     snes->max_its = maxit;
3068   }
3069   if (maxf != PETSC_DEFAULT) {
3070     if (maxf < 0) SETERRQ1(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_OUTOFRANGE,"Maximum number of function evaluations %D must be non-negative",maxf);
3071     snes->max_funcs = maxf;
3072   }
3073   snes->tolerancesset = PETSC_TRUE;
3074   PetscFunctionReturn(0);
3075 }
3076 
3077 #undef __FUNCT__
3078 #define __FUNCT__ "SNESGetTolerances"
3079 /*@
3080    SNESGetTolerances - Gets various parameters used in convergence tests.
3081 
3082    Not Collective
3083 
3084    Input Parameters:
3085 +  snes - the SNES context
3086 .  atol - absolute convergence tolerance
3087 .  rtol - relative convergence tolerance
3088 .  stol -  convergence tolerance in terms of the norm
3089            of the change in the solution between steps
3090 .  maxit - maximum number of iterations
3091 -  maxf - maximum number of function evaluations
3092 
3093    Notes:
3094    The user can specify NULL for any parameter that is not needed.
3095 
3096    Level: intermediate
3097 
3098 .keywords: SNES, nonlinear, get, convergence, tolerances
3099 
3100 .seealso: SNESSetTolerances()
3101 @*/
3102 PetscErrorCode  SNESGetTolerances(SNES snes,PetscReal *atol,PetscReal *rtol,PetscReal *stol,PetscInt *maxit,PetscInt *maxf)
3103 {
3104   PetscFunctionBegin;
3105   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3106   if (atol)  *atol  = snes->abstol;
3107   if (rtol)  *rtol  = snes->rtol;
3108   if (stol)  *stol  = snes->stol;
3109   if (maxit) *maxit = snes->max_its;
3110   if (maxf)  *maxf  = snes->max_funcs;
3111   PetscFunctionReturn(0);
3112 }
3113 
3114 #undef __FUNCT__
3115 #define __FUNCT__ "SNESSetTrustRegionTolerance"
3116 /*@
3117    SNESSetTrustRegionTolerance - Sets the trust region parameter tolerance.
3118 
3119    Logically Collective on SNES
3120 
3121    Input Parameters:
3122 +  snes - the SNES context
3123 -  tol - tolerance
3124 
3125    Options Database Key:
3126 .  -snes_trtol <tol> - Sets tol
3127 
3128    Level: intermediate
3129 
3130 .keywords: SNES, nonlinear, set, trust region, tolerance
3131 
3132 .seealso: SNESSetTolerances()
3133 @*/
3134 PetscErrorCode  SNESSetTrustRegionTolerance(SNES snes,PetscReal tol)
3135 {
3136   PetscFunctionBegin;
3137   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3138   PetscValidLogicalCollectiveReal(snes,tol,2);
3139   snes->deltatol = tol;
3140   PetscFunctionReturn(0);
3141 }
3142 
3143 /*
3144    Duplicate the lg monitors for SNES from KSP; for some reason with
3145    dynamic libraries things don't work under Sun4 if we just use
3146    macros instead of functions
3147 */
3148 #undef __FUNCT__
3149 #define __FUNCT__ "SNESMonitorLGResidualNorm"
3150 PetscErrorCode  SNESMonitorLGResidualNorm(SNES snes,PetscInt it,PetscReal norm,PetscObject *objs)
3151 {
3152   PetscErrorCode ierr;
3153 
3154   PetscFunctionBegin;
3155   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3156   ierr = KSPMonitorLGResidualNorm((KSP)snes,it,norm,objs);CHKERRQ(ierr);
3157   PetscFunctionReturn(0);
3158 }
3159 
3160 #undef __FUNCT__
3161 #define __FUNCT__ "SNESMonitorLGCreate"
3162 PetscErrorCode  SNESMonitorLGCreate(const char host[],const char label[],int x,int y,int m,int n,PetscObject **draw)
3163 {
3164   PetscErrorCode ierr;
3165 
3166   PetscFunctionBegin;
3167   ierr = KSPMonitorLGResidualNormCreate(host,label,x,y,m,n,draw);CHKERRQ(ierr);
3168   PetscFunctionReturn(0);
3169 }
3170 
3171 #undef __FUNCT__
3172 #define __FUNCT__ "SNESMonitorLGDestroy"
3173 PetscErrorCode  SNESMonitorLGDestroy(PetscObject **objs)
3174 {
3175   PetscErrorCode ierr;
3176 
3177   PetscFunctionBegin;
3178   ierr = KSPMonitorLGResidualNormDestroy(objs);CHKERRQ(ierr);
3179   PetscFunctionReturn(0);
3180 }
3181 
3182 extern PetscErrorCode  SNESMonitorRange_Private(SNES,PetscInt,PetscReal*);
3183 #undef __FUNCT__
3184 #define __FUNCT__ "SNESMonitorLGRange"
3185 PetscErrorCode  SNESMonitorLGRange(SNES snes,PetscInt n,PetscReal rnorm,void *monctx)
3186 {
3187   PetscDrawLG      lg;
3188   PetscErrorCode   ierr;
3189   PetscReal        x,y,per;
3190   PetscViewer      v = (PetscViewer)monctx;
3191   static PetscReal prev; /* should be in the context */
3192   PetscDraw        draw;
3193 
3194   PetscFunctionBegin;
3195   ierr = PetscViewerDrawGetDrawLG(v,0,&lg);CHKERRQ(ierr);
3196   if (!n) {ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3197   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3198   ierr = PetscDrawSetTitle(draw,"Residual norm");CHKERRQ(ierr);
3199   x    = (PetscReal)n;
3200   if (rnorm > 0.0) y = PetscLog10Real(rnorm);
3201   else y = -15.0;
3202   ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3203   if (n < 20 || !(n % 5)) {
3204     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3205   }
3206 
3207   ierr = PetscViewerDrawGetDrawLG(v,1,&lg);CHKERRQ(ierr);
3208   if (!n) {ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3209   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3210   ierr = PetscDrawSetTitle(draw,"% elemts > .2*max elemt");CHKERRQ(ierr);
3211   ierr =  SNESMonitorRange_Private(snes,n,&per);CHKERRQ(ierr);
3212   x    = (PetscReal)n;
3213   y    = 100.0*per;
3214   ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3215   if (n < 20 || !(n % 5)) {
3216     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3217   }
3218 
3219   ierr = PetscViewerDrawGetDrawLG(v,2,&lg);CHKERRQ(ierr);
3220   if (!n) {prev = rnorm;ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3221   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3222   ierr = PetscDrawSetTitle(draw,"(norm -oldnorm)/oldnorm");CHKERRQ(ierr);
3223   x    = (PetscReal)n;
3224   y    = (prev - rnorm)/prev;
3225   ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3226   if (n < 20 || !(n % 5)) {
3227     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3228   }
3229 
3230   ierr = PetscViewerDrawGetDrawLG(v,3,&lg);CHKERRQ(ierr);
3231   if (!n) {ierr = PetscDrawLGReset(lg);CHKERRQ(ierr);}
3232   ierr = PetscDrawLGGetDraw(lg,&draw);CHKERRQ(ierr);
3233   ierr = PetscDrawSetTitle(draw,"(norm -oldnorm)/oldnorm*(% > .2 max)");CHKERRQ(ierr);
3234   x    = (PetscReal)n;
3235   y    = (prev - rnorm)/(prev*per);
3236   if (n > 2) { /*skip initial crazy value */
3237     ierr = PetscDrawLGAddPoint(lg,&x,&y);CHKERRQ(ierr);
3238   }
3239   if (n < 20 || !(n % 5)) {
3240     ierr = PetscDrawLGDraw(lg);CHKERRQ(ierr);
3241   }
3242   prev = rnorm;
3243   PetscFunctionReturn(0);
3244 }
3245 
3246 #undef __FUNCT__
3247 #define __FUNCT__ "SNESMonitor"
3248 /*@
3249    SNESMonitor - runs the user provided monitor routines, if they exist
3250 
3251    Collective on SNES
3252 
3253    Input Parameters:
3254 +  snes - nonlinear solver context obtained from SNESCreate()
3255 .  iter - iteration number
3256 -  rnorm - relative norm of the residual
3257 
3258    Notes:
3259    This routine is called by the SNES implementations.
3260    It does not typically need to be called by the user.
3261 
3262    Level: developer
3263 
3264 .seealso: SNESMonitorSet()
3265 @*/
3266 PetscErrorCode  SNESMonitor(SNES snes,PetscInt iter,PetscReal rnorm)
3267 {
3268   PetscErrorCode ierr;
3269   PetscInt       i,n = snes->numbermonitors;
3270 
3271   PetscFunctionBegin;
3272   ierr = VecLockPush(snes->vec_sol);CHKERRQ(ierr);
3273   for (i=0; i<n; i++) {
3274     ierr = (*snes->monitor[i])(snes,iter,rnorm,snes->monitorcontext[i]);CHKERRQ(ierr);
3275   }
3276   ierr = VecLockPop(snes->vec_sol);CHKERRQ(ierr);
3277   PetscFunctionReturn(0);
3278 }
3279 
3280 /* ------------ Routines to set performance monitoring options ----------- */
3281 
3282 /*MC
3283     SNESMonitorFunction - functional form passed to SNESMonitorSet() to monitor convergence of nonlinear solver
3284 
3285      Synopsis:
3286      #include <petscsnes.h>
3287 $    PetscErrorCode SNESMonitorFunction(SNES snes,PetscInt its, PetscReal norm,void *mctx)
3288 
3289 +    snes - the SNES context
3290 .    its - iteration number
3291 .    norm - 2-norm function value (may be estimated)
3292 -    mctx - [optional] monitoring context
3293 
3294    Level: advanced
3295 
3296 .seealso:   SNESMonitorSet(), SNESMonitorGet()
3297 M*/
3298 
3299 #undef __FUNCT__
3300 #define __FUNCT__ "SNESMonitorSet"
3301 /*@C
3302    SNESMonitorSet - Sets an ADDITIONAL function that is to be used at every
3303    iteration of the nonlinear solver to display the iteration's
3304    progress.
3305 
3306    Logically Collective on SNES
3307 
3308    Input Parameters:
3309 +  snes - the SNES context
3310 .  f - the monitor function, see SNESMonitorFunction for the calling sequence
3311 .  mctx - [optional] user-defined context for private data for the
3312           monitor routine (use NULL if no context is desired)
3313 -  monitordestroy - [optional] routine that frees monitor context
3314           (may be NULL)
3315 
3316    Options Database Keys:
3317 +    -snes_monitor        - sets SNESMonitorDefault()
3318 .    -snes_monitor_lg_residualnorm    - sets line graph monitor,
3319                             uses SNESMonitorLGCreate()
3320 -    -snes_monitor_cancel - cancels all monitors that have
3321                             been hardwired into a code by
3322                             calls to SNESMonitorSet(), but
3323                             does not cancel those set via
3324                             the options database.
3325 
3326    Notes:
3327    Several different monitoring routines may be set by calling
3328    SNESMonitorSet() multiple times; all will be called in the
3329    order in which they were set.
3330 
3331    Fortran notes: Only a single monitor function can be set for each SNES object
3332 
3333    Level: intermediate
3334 
3335 .keywords: SNES, nonlinear, set, monitor
3336 
3337 .seealso: SNESMonitorDefault(), SNESMonitorCancel(), SNESMonitorFunction
3338 @*/
3339 PetscErrorCode  SNESMonitorSet(SNES snes,PetscErrorCode (*f)(SNES,PetscInt,PetscReal,void*),void *mctx,PetscErrorCode (*monitordestroy)(void**))
3340 {
3341   PetscInt       i;
3342   PetscErrorCode ierr;
3343 
3344   PetscFunctionBegin;
3345   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3346   if (snes->numbermonitors >= MAXSNESMONITORS) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Too many monitors set");
3347   for (i=0; i<snes->numbermonitors;i++) {
3348     if (f == snes->monitor[i] && monitordestroy == snes->monitordestroy[i] && mctx == snes->monitorcontext[i]) {
3349       if (monitordestroy) {
3350         ierr = (*monitordestroy)(&mctx);CHKERRQ(ierr);
3351       }
3352       PetscFunctionReturn(0);
3353     }
3354   }
3355   snes->monitor[snes->numbermonitors]          = f;
3356   snes->monitordestroy[snes->numbermonitors]   = monitordestroy;
3357   snes->monitorcontext[snes->numbermonitors++] = (void*)mctx;
3358   PetscFunctionReturn(0);
3359 }
3360 
3361 #undef __FUNCT__
3362 #define __FUNCT__ "SNESMonitorCancel"
3363 /*@
3364    SNESMonitorCancel - Clears all the monitor functions for a SNES object.
3365 
3366    Logically Collective on SNES
3367 
3368    Input Parameters:
3369 .  snes - the SNES context
3370 
3371    Options Database Key:
3372 .  -snes_monitor_cancel - cancels all monitors that have been hardwired
3373     into a code by calls to SNESMonitorSet(), but does not cancel those
3374     set via the options database
3375 
3376    Notes:
3377    There is no way to clear one specific monitor from a SNES object.
3378 
3379    Level: intermediate
3380 
3381 .keywords: SNES, nonlinear, set, monitor
3382 
3383 .seealso: SNESMonitorDefault(), SNESMonitorSet()
3384 @*/
3385 PetscErrorCode  SNESMonitorCancel(SNES snes)
3386 {
3387   PetscErrorCode ierr;
3388   PetscInt       i;
3389 
3390   PetscFunctionBegin;
3391   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3392   for (i=0; i<snes->numbermonitors; i++) {
3393     if (snes->monitordestroy[i]) {
3394       ierr = (*snes->monitordestroy[i])(&snes->monitorcontext[i]);CHKERRQ(ierr);
3395     }
3396   }
3397   snes->numbermonitors = 0;
3398   PetscFunctionReturn(0);
3399 }
3400 
3401 /*MC
3402     SNESConvergenceTestFunction - functional form used for testing of convergence of nonlinear solver
3403 
3404      Synopsis:
3405      #include <petscsnes.h>
3406 $     PetscErrorCode SNESConvergenceTest(SNES snes,PetscInt it,PetscReal xnorm,PetscReal gnorm,PetscReal f,SNESConvergedReason *reason,void *cctx)
3407 
3408 +    snes - the SNES context
3409 .    it - current iteration (0 is the first and is before any Newton step)
3410 .    cctx - [optional] convergence context
3411 .    reason - reason for convergence/divergence
3412 .    xnorm - 2-norm of current iterate
3413 .    gnorm - 2-norm of current step
3414 -    f - 2-norm of function
3415 
3416    Level: intermediate
3417 
3418 .seealso:   SNESSetConvergenceTest(), SNESGetConvergenceTest()
3419 M*/
3420 
3421 #undef __FUNCT__
3422 #define __FUNCT__ "SNESSetConvergenceTest"
3423 /*@C
3424    SNESSetConvergenceTest - Sets the function that is to be used
3425    to test for convergence of the nonlinear iterative solution.
3426 
3427    Logically Collective on SNES
3428 
3429    Input Parameters:
3430 +  snes - the SNES context
3431 .  SNESConvergenceTestFunction - routine to test for convergence
3432 .  cctx - [optional] context for private data for the convergence routine  (may be NULL)
3433 -  destroy - [optional] destructor for the context (may be NULL; NULL_FUNCTION in Fortran)
3434 
3435    Level: advanced
3436 
3437 .keywords: SNES, nonlinear, set, convergence, test
3438 
3439 .seealso: SNESConvergedDefault(), SNESConvergedSkip(), SNESConvergenceTestFunction
3440 @*/
3441 PetscErrorCode  SNESSetConvergenceTest(SNES snes,PetscErrorCode (*SNESConvergenceTestFunction)(SNES,PetscInt,PetscReal,PetscReal,PetscReal,SNESConvergedReason*,void*),void *cctx,PetscErrorCode (*destroy)(void*))
3442 {
3443   PetscErrorCode ierr;
3444 
3445   PetscFunctionBegin;
3446   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3447   if (!SNESConvergenceTestFunction) SNESConvergenceTestFunction = SNESConvergedSkip;
3448   if (snes->ops->convergeddestroy) {
3449     ierr = (*snes->ops->convergeddestroy)(snes->cnvP);CHKERRQ(ierr);
3450   }
3451   snes->ops->converged        = SNESConvergenceTestFunction;
3452   snes->ops->convergeddestroy = destroy;
3453   snes->cnvP                  = cctx;
3454   PetscFunctionReturn(0);
3455 }
3456 
3457 #undef __FUNCT__
3458 #define __FUNCT__ "SNESGetConvergedReason"
3459 /*@
3460    SNESGetConvergedReason - Gets the reason the SNES iteration was stopped.
3461 
3462    Not Collective
3463 
3464    Input Parameter:
3465 .  snes - the SNES context
3466 
3467    Output Parameter:
3468 .  reason - negative value indicates diverged, positive value converged, see SNESConvergedReason or the
3469             manual pages for the individual convergence tests for complete lists
3470 
3471    Level: intermediate
3472 
3473    Notes: Can only be called after the call the SNESSolve() is complete.
3474 
3475 .keywords: SNES, nonlinear, set, convergence, test
3476 
3477 .seealso: SNESSetConvergenceTest(), SNESConvergedReason
3478 @*/
3479 PetscErrorCode  SNESGetConvergedReason(SNES snes,SNESConvergedReason *reason)
3480 {
3481   PetscFunctionBegin;
3482   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3483   PetscValidPointer(reason,2);
3484   *reason = snes->reason;
3485   PetscFunctionReturn(0);
3486 }
3487 
3488 #undef __FUNCT__
3489 #define __FUNCT__ "SNESSetConvergenceHistory"
3490 /*@
3491    SNESSetConvergenceHistory - Sets the array used to hold the convergence history.
3492 
3493    Logically Collective on SNES
3494 
3495    Input Parameters:
3496 +  snes - iterative context obtained from SNESCreate()
3497 .  a   - array to hold history, this array will contain the function norms computed at each step
3498 .  its - integer array holds the number of linear iterations for each solve.
3499 .  na  - size of a and its
3500 -  reset - PETSC_TRUE indicates each new nonlinear solve resets the history counter to zero,
3501            else it continues storing new values for new nonlinear solves after the old ones
3502 
3503    Notes:
3504    If 'a' and 'its' are NULL then space is allocated for the history. If 'na' PETSC_DECIDE or PETSC_DEFAULT then a
3505    default array of length 10000 is allocated.
3506 
3507    This routine is useful, e.g., when running a code for purposes
3508    of accurate performance monitoring, when no I/O should be done
3509    during the section of code that is being timed.
3510 
3511    Level: intermediate
3512 
3513 .keywords: SNES, set, convergence, history
3514 
3515 .seealso: SNESGetConvergenceHistory()
3516 
3517 @*/
3518 PetscErrorCode  SNESSetConvergenceHistory(SNES snes,PetscReal a[],PetscInt its[],PetscInt na,PetscBool reset)
3519 {
3520   PetscErrorCode ierr;
3521 
3522   PetscFunctionBegin;
3523   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3524   if (a) PetscValidScalarPointer(a,2);
3525   if (its) PetscValidIntPointer(its,3);
3526   if (!a) {
3527     if (na == PETSC_DECIDE || na == PETSC_DEFAULT) na = 1000;
3528     ierr = PetscCalloc1(na,&a);CHKERRQ(ierr);
3529     ierr = PetscCalloc1(na,&its);CHKERRQ(ierr);
3530 
3531     snes->conv_malloc = PETSC_TRUE;
3532   }
3533   snes->conv_hist       = a;
3534   snes->conv_hist_its   = its;
3535   snes->conv_hist_max   = na;
3536   snes->conv_hist_len   = 0;
3537   snes->conv_hist_reset = reset;
3538   PetscFunctionReturn(0);
3539 }
3540 
3541 #if defined(PETSC_HAVE_MATLAB_ENGINE)
3542 #include <engine.h>   /* MATLAB include file */
3543 #include <mex.h>      /* MATLAB include file */
3544 
3545 #undef __FUNCT__
3546 #define __FUNCT__ "SNESGetConvergenceHistoryMatlab"
3547 PETSC_EXTERN mxArray *SNESGetConvergenceHistoryMatlab(SNES snes)
3548 {
3549   mxArray   *mat;
3550   PetscInt  i;
3551   PetscReal *ar;
3552 
3553   PetscFunctionBegin;
3554   mat = mxCreateDoubleMatrix(snes->conv_hist_len,1,mxREAL);
3555   ar  = (PetscReal*) mxGetData(mat);
3556   for (i=0; i<snes->conv_hist_len; i++) ar[i] = snes->conv_hist[i];
3557   PetscFunctionReturn(mat);
3558 }
3559 #endif
3560 
3561 #undef __FUNCT__
3562 #define __FUNCT__ "SNESGetConvergenceHistory"
3563 /*@C
3564    SNESGetConvergenceHistory - Gets the array used to hold the convergence history.
3565 
3566    Not Collective
3567 
3568    Input Parameter:
3569 .  snes - iterative context obtained from SNESCreate()
3570 
3571    Output Parameters:
3572 .  a   - array to hold history
3573 .  its - integer array holds the number of linear iterations (or
3574          negative if not converged) for each solve.
3575 -  na  - size of a and its
3576 
3577    Notes:
3578     The calling sequence for this routine in Fortran is
3579 $   call SNESGetConvergenceHistory(SNES snes, integer na, integer ierr)
3580 
3581    This routine is useful, e.g., when running a code for purposes
3582    of accurate performance monitoring, when no I/O should be done
3583    during the section of code that is being timed.
3584 
3585    Level: intermediate
3586 
3587 .keywords: SNES, get, convergence, history
3588 
3589 .seealso: SNESSetConvergencHistory()
3590 
3591 @*/
3592 PetscErrorCode  SNESGetConvergenceHistory(SNES snes,PetscReal *a[],PetscInt *its[],PetscInt *na)
3593 {
3594   PetscFunctionBegin;
3595   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3596   if (a)   *a   = snes->conv_hist;
3597   if (its) *its = snes->conv_hist_its;
3598   if (na)  *na  = snes->conv_hist_len;
3599   PetscFunctionReturn(0);
3600 }
3601 
3602 #undef __FUNCT__
3603 #define __FUNCT__ "SNESSetUpdate"
3604 /*@C
3605   SNESSetUpdate - Sets the general-purpose update function called
3606   at the beginning of every iteration of the nonlinear solve. Specifically
3607   it is called just before the Jacobian is "evaluated".
3608 
3609   Logically Collective on SNES
3610 
3611   Input Parameters:
3612 . snes - The nonlinear solver context
3613 . func - The function
3614 
3615   Calling sequence of func:
3616 . func (SNES snes, PetscInt step);
3617 
3618 . step - The current step of the iteration
3619 
3620   Level: advanced
3621 
3622   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()
3623         This is not used by most users.
3624 
3625 .keywords: SNES, update
3626 
3627 .seealso SNESSetJacobian(), SNESSolve()
3628 @*/
3629 PetscErrorCode  SNESSetUpdate(SNES snes, PetscErrorCode (*func)(SNES, PetscInt))
3630 {
3631   PetscFunctionBegin;
3632   PetscValidHeaderSpecific(snes, SNES_CLASSID,1);
3633   snes->ops->update = func;
3634   PetscFunctionReturn(0);
3635 }
3636 
3637 #undef __FUNCT__
3638 #define __FUNCT__ "SNESScaleStep_Private"
3639 /*
3640    SNESScaleStep_Private - Scales a step so that its length is less than the
3641    positive parameter delta.
3642 
3643     Input Parameters:
3644 +   snes - the SNES context
3645 .   y - approximate solution of linear system
3646 .   fnorm - 2-norm of current function
3647 -   delta - trust region size
3648 
3649     Output Parameters:
3650 +   gpnorm - predicted function norm at the new point, assuming local
3651     linearization.  The value is zero if the step lies within the trust
3652     region, and exceeds zero otherwise.
3653 -   ynorm - 2-norm of the step
3654 
3655     Note:
3656     For non-trust region methods such as SNESNEWTONLS, the parameter delta
3657     is set to be the maximum allowable step size.
3658 
3659 .keywords: SNES, nonlinear, scale, step
3660 */
3661 PetscErrorCode SNESScaleStep_Private(SNES snes,Vec y,PetscReal *fnorm,PetscReal *delta,PetscReal *gpnorm,PetscReal *ynorm)
3662 {
3663   PetscReal      nrm;
3664   PetscScalar    cnorm;
3665   PetscErrorCode ierr;
3666 
3667   PetscFunctionBegin;
3668   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3669   PetscValidHeaderSpecific(y,VEC_CLASSID,2);
3670   PetscCheckSameComm(snes,1,y,2);
3671 
3672   ierr = VecNorm(y,NORM_2,&nrm);CHKERRQ(ierr);
3673   if (nrm > *delta) {
3674     nrm     = *delta/nrm;
3675     *gpnorm = (1.0 - nrm)*(*fnorm);
3676     cnorm   = nrm;
3677     ierr    = VecScale(y,cnorm);CHKERRQ(ierr);
3678     *ynorm  = *delta;
3679   } else {
3680     *gpnorm = 0.0;
3681     *ynorm  = nrm;
3682   }
3683   PetscFunctionReturn(0);
3684 }
3685 
3686 #undef __FUNCT__
3687 #define __FUNCT__ "SNESReasonView"
3688 /*@
3689    SNESReasonView - Displays the reason a SNES solve converged or diverged to a viewer
3690 
3691    Collective on SNES
3692 
3693    Parameter:
3694 +  snes - iterative context obtained from SNESCreate()
3695 -  viewer - the viewer to display the reason
3696 
3697 
3698    Options Database Keys:
3699 .  -snes_converged_reason - print reason for converged or diverged, also prints number of iterations
3700 
3701    Level: beginner
3702 
3703 .keywords: SNES, solve, linear system
3704 
3705 .seealso: SNESCreate(), SNESSetUp(), SNESDestroy(), SNESSetTolerances(), SNESConvergedDefault()
3706 
3707 @*/
3708 PetscErrorCode  SNESReasonView(SNES snes,PetscViewer viewer)
3709 {
3710   PetscErrorCode ierr;
3711   PetscBool      isAscii;
3712 
3713   PetscFunctionBegin;
3714   ierr = PetscObjectTypeCompare((PetscObject)viewer,PETSCVIEWERASCII,&isAscii);CHKERRQ(ierr);
3715   if (isAscii) {
3716     ierr = PetscViewerASCIIAddTab(viewer,((PetscObject)snes)->tablevel);CHKERRQ(ierr);
3717     if (snes->reason > 0) {
3718       if (((PetscObject) snes)->prefix) {
3719         ierr = PetscViewerASCIIPrintf(viewer,"Nonlinear %s solve converged due to %s iterations %D\n",((PetscObject) snes)->prefix,SNESConvergedReasons[snes->reason],snes->iter);CHKERRQ(ierr);
3720       } else {
3721         ierr = PetscViewerASCIIPrintf(viewer,"Nonlinear solve converged due to %s iterations %D\n",SNESConvergedReasons[snes->reason],snes->iter);CHKERRQ(ierr);
3722       }
3723     } else {
3724       if (((PetscObject) snes)->prefix) {
3725         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);
3726       } else {
3727         ierr = PetscViewerASCIIPrintf(viewer,"Nonlinear solve did not converge due to %s iterations %D\n",SNESConvergedReasons[snes->reason],snes->iter);CHKERRQ(ierr);
3728       }
3729     }
3730     ierr = PetscViewerASCIISubtractTab(viewer,((PetscObject)snes)->tablevel);CHKERRQ(ierr);
3731   }
3732   PetscFunctionReturn(0);
3733 }
3734 
3735 #undef __FUNCT__
3736 #define __FUNCT__ "SNESReasonViewFromOptions"
3737 /*@C
3738   SNESReasonViewFromOptions - Processes command line options to determine if/how a SNESReason is to be viewed.
3739 
3740   Collective on SNES
3741 
3742   Input Parameters:
3743 . snes   - the SNES object
3744 
3745   Level: intermediate
3746 
3747 @*/
3748 PetscErrorCode SNESReasonViewFromOptions(SNES snes)
3749 {
3750   PetscErrorCode    ierr;
3751   PetscViewer       viewer;
3752   PetscBool         flg;
3753   static PetscBool  incall = PETSC_FALSE;
3754   PetscViewerFormat format;
3755 
3756   PetscFunctionBegin;
3757   if (incall) PetscFunctionReturn(0);
3758   incall = PETSC_TRUE;
3759   ierr   = PetscOptionsGetViewer(PetscObjectComm((PetscObject)snes),((PetscObject)snes)->prefix,"-snes_converged_reason",&viewer,&format,&flg);CHKERRQ(ierr);
3760   if (flg) {
3761     ierr = PetscViewerPushFormat(viewer,format);CHKERRQ(ierr);
3762     ierr = SNESReasonView(snes,viewer);CHKERRQ(ierr);
3763     ierr = PetscViewerPopFormat(viewer);CHKERRQ(ierr);
3764     ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
3765   }
3766   incall = PETSC_FALSE;
3767   PetscFunctionReturn(0);
3768 }
3769 
3770 #undef __FUNCT__
3771 #define __FUNCT__ "SNESSolve"
3772 /*@C
3773    SNESSolve - Solves a nonlinear system F(x) = b.
3774    Call SNESSolve() after calling SNESCreate() and optional routines of the form SNESSetXXX().
3775 
3776    Collective on SNES
3777 
3778    Input Parameters:
3779 +  snes - the SNES context
3780 .  b - the constant part of the equation F(x) = b, or NULL to use zero.
3781 -  x - the solution vector.
3782 
3783    Notes:
3784    The user should initialize the vector,x, with the initial guess
3785    for the nonlinear solve prior to calling SNESSolve.  In particular,
3786    to employ an initial guess of zero, the user should explicitly set
3787    this vector to zero by calling VecSet().
3788 
3789    Level: beginner
3790 
3791 .keywords: SNES, nonlinear, solve
3792 
3793 .seealso: SNESCreate(), SNESDestroy(), SNESSetFunction(), SNESSetJacobian(), SNESSetGridSequence(), SNESGetSolution()
3794 @*/
3795 PetscErrorCode  SNESSolve(SNES snes,Vec b,Vec x)
3796 {
3797   PetscErrorCode    ierr;
3798   PetscBool         flg;
3799   PetscInt          grid;
3800   Vec               xcreated = NULL;
3801   DM                dm;
3802 
3803   PetscFunctionBegin;
3804   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3805   if (x) PetscValidHeaderSpecific(x,VEC_CLASSID,3);
3806   if (x) PetscCheckSameComm(snes,1,x,3);
3807   if (b) PetscValidHeaderSpecific(b,VEC_CLASSID,2);
3808   if (b) PetscCheckSameComm(snes,1,b,2);
3809 
3810   if (!x) {
3811     ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
3812     ierr = DMCreateGlobalVector(dm,&xcreated);CHKERRQ(ierr);
3813     x    = xcreated;
3814   }
3815   ierr = SNESViewFromOptions(snes,NULL,"-snes_view_pre");CHKERRQ(ierr);
3816 
3817   for (grid=0; grid<snes->gridsequence; grid++) {ierr = PetscViewerASCIIPushTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)));CHKERRQ(ierr);}
3818   for (grid=0; grid<snes->gridsequence+1; grid++) {
3819 
3820     /* set solution vector */
3821     if (!grid) {ierr = PetscObjectReference((PetscObject)x);CHKERRQ(ierr);}
3822     ierr          = VecDestroy(&snes->vec_sol);CHKERRQ(ierr);
3823     snes->vec_sol = x;
3824     ierr          = SNESGetDM(snes,&dm);CHKERRQ(ierr);
3825 
3826     /* set affine vector if provided */
3827     if (b) { ierr = PetscObjectReference((PetscObject)b);CHKERRQ(ierr); }
3828     ierr          = VecDestroy(&snes->vec_rhs);CHKERRQ(ierr);
3829     snes->vec_rhs = b;
3830 
3831     if (snes->vec_func == snes->vec_sol) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_IDN,"Solution vector cannot be function vector");
3832     if (snes->vec_rhs  == snes->vec_sol) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_IDN,"Solution vector cannot be right hand side vector");
3833     if (!snes->vec_sol_update /* && snes->vec_sol */) {
3834       ierr = VecDuplicate(snes->vec_sol,&snes->vec_sol_update);CHKERRQ(ierr);
3835       ierr = PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->vec_sol_update);CHKERRQ(ierr);
3836     }
3837     ierr = DMShellSetGlobalVector(dm,snes->vec_sol);CHKERRQ(ierr);
3838     ierr = SNESSetUp(snes);CHKERRQ(ierr);
3839 
3840     if (!grid) {
3841       if (snes->ops->computeinitialguess) {
3842         ierr = (*snes->ops->computeinitialguess)(snes,snes->vec_sol,snes->initialguessP);CHKERRQ(ierr);
3843       }
3844     }
3845 
3846     if (snes->conv_hist_reset) snes->conv_hist_len = 0;
3847     if (snes->counters_reset) {snes->nfuncs = 0; snes->linear_its = 0; snes->numFailures = 0;}
3848 
3849     ierr = PetscLogEventBegin(SNES_Solve,snes,0,0,0);CHKERRQ(ierr);
3850     ierr = (*snes->ops->solve)(snes);CHKERRQ(ierr);
3851     ierr = PetscLogEventEnd(SNES_Solve,snes,0,0,0);CHKERRQ(ierr);
3852     if (snes->domainerror) {
3853       snes->reason      = SNES_DIVERGED_FUNCTION_DOMAIN;
3854       snes->domainerror = PETSC_FALSE;
3855     }
3856     if (!snes->reason) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_PLIB,"Internal error, solver returned without setting converged reason");
3857 
3858     if (snes->lagjac_persist) snes->jac_iter += snes->iter;
3859     if (snes->lagpre_persist) snes->pre_iter += snes->iter;
3860 
3861     flg  = PETSC_FALSE;
3862     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-snes_test_local_min",&flg,NULL);CHKERRQ(ierr);
3863     if (flg && !PetscPreLoadingOn) { ierr = SNESTestLocalMin(snes);CHKERRQ(ierr); }
3864     ierr = SNESReasonViewFromOptions(snes);CHKERRQ(ierr);
3865 
3866     if (snes->errorifnotconverged && snes->reason < 0) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_NOT_CONVERGED,"SNESSolve has not converged");
3867     if (grid <  snes->gridsequence) {
3868       DM  fine;
3869       Vec xnew;
3870       Mat interp;
3871 
3872       ierr = DMRefine(snes->dm,PetscObjectComm((PetscObject)snes),&fine);CHKERRQ(ierr);
3873       if (!fine) SETERRQ(PetscObjectComm((PetscObject)snes),PETSC_ERR_ARG_INCOMP,"DMRefine() did not perform any refinement, cannot continue grid sequencing");
3874       ierr = DMCreateInterpolation(snes->dm,fine,&interp,NULL);CHKERRQ(ierr);
3875       ierr = DMCreateGlobalVector(fine,&xnew);CHKERRQ(ierr);
3876       ierr = MatInterpolate(interp,x,xnew);CHKERRQ(ierr);
3877       ierr = DMInterpolate(snes->dm,interp,fine);CHKERRQ(ierr);
3878       ierr = MatDestroy(&interp);CHKERRQ(ierr);
3879       x    = xnew;
3880 
3881       ierr = SNESReset(snes);CHKERRQ(ierr);
3882       ierr = SNESSetDM(snes,fine);CHKERRQ(ierr);
3883       ierr = DMDestroy(&fine);CHKERRQ(ierr);
3884       ierr = PetscViewerASCIIPopTab(PETSC_VIEWER_STDOUT_(PetscObjectComm((PetscObject)snes)));CHKERRQ(ierr);
3885     }
3886   }
3887   ierr = SNESViewFromOptions(snes,NULL,"-snes_view");CHKERRQ(ierr);
3888   ierr = VecViewFromOptions(snes->vec_sol,((PetscObject)snes)->prefix,"-snes_view_solution");CHKERRQ(ierr);
3889 
3890   ierr = VecDestroy(&xcreated);CHKERRQ(ierr);
3891   ierr = PetscObjectSAWsBlock((PetscObject)snes);CHKERRQ(ierr);
3892   PetscFunctionReturn(0);
3893 }
3894 
3895 /* --------- Internal routines for SNES Package --------- */
3896 
3897 #undef __FUNCT__
3898 #define __FUNCT__ "SNESSetType"
3899 /*@C
3900    SNESSetType - Sets the method for the nonlinear solver.
3901 
3902    Collective on SNES
3903 
3904    Input Parameters:
3905 +  snes - the SNES context
3906 -  type - a known method
3907 
3908    Options Database Key:
3909 .  -snes_type <type> - Sets the method; use -help for a list
3910    of available methods (for instance, newtonls or newtontr)
3911 
3912    Notes:
3913    See "petsc/include/petscsnes.h" for available methods (for instance)
3914 +    SNESNEWTONLS - Newton's method with line search
3915      (systems of nonlinear equations)
3916 .    SNESNEWTONTR - Newton's method with trust region
3917      (systems of nonlinear equations)
3918 
3919   Normally, it is best to use the SNESSetFromOptions() command and then
3920   set the SNES solver type from the options database rather than by using
3921   this routine.  Using the options database provides the user with
3922   maximum flexibility in evaluating the many nonlinear solvers.
3923   The SNESSetType() routine is provided for those situations where it
3924   is necessary to set the nonlinear solver independently of the command
3925   line or options database.  This might be the case, for example, when
3926   the choice of solver changes during the execution of the program,
3927   and the user's application is taking responsibility for choosing the
3928   appropriate method.
3929 
3930     Developer Notes: SNESRegister() adds a constructor for a new SNESType to SNESList, SNESSetType() locates
3931     the constructor in that list and calls it to create the spexific object.
3932 
3933   Level: intermediate
3934 
3935 .keywords: SNES, set, type
3936 
3937 .seealso: SNESType, SNESCreate(), SNESDestroy(), SNESGetType(), SNESSetFromOptions()
3938 
3939 @*/
3940 PetscErrorCode  SNESSetType(SNES snes,SNESType type)
3941 {
3942   PetscErrorCode ierr,(*r)(SNES);
3943   PetscBool      match;
3944 
3945   PetscFunctionBegin;
3946   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3947   PetscValidCharPointer(type,2);
3948 
3949   ierr = PetscObjectTypeCompare((PetscObject)snes,type,&match);CHKERRQ(ierr);
3950   if (match) PetscFunctionReturn(0);
3951 
3952   ierr =  PetscFunctionListFind(SNESList,type,&r);CHKERRQ(ierr);
3953   if (!r) SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_UNKNOWN_TYPE,"Unable to find requested SNES type %s",type);
3954   /* Destroy the previous private SNES context */
3955   if (snes->ops->destroy) {
3956     ierr               = (*(snes)->ops->destroy)(snes);CHKERRQ(ierr);
3957     snes->ops->destroy = NULL;
3958   }
3959   /* Reinitialize function pointers in SNESOps structure */
3960   snes->ops->setup          = 0;
3961   snes->ops->solve          = 0;
3962   snes->ops->view           = 0;
3963   snes->ops->setfromoptions = 0;
3964   snes->ops->destroy        = 0;
3965   /* Call the SNESCreate_XXX routine for this particular Nonlinear solver */
3966   snes->setupcalled = PETSC_FALSE;
3967 
3968   ierr = PetscObjectChangeTypeName((PetscObject)snes,type);CHKERRQ(ierr);
3969   ierr = (*r)(snes);CHKERRQ(ierr);
3970   PetscFunctionReturn(0);
3971 }
3972 
3973 #undef __FUNCT__
3974 #define __FUNCT__ "SNESGetType"
3975 /*@C
3976    SNESGetType - Gets the SNES method type and name (as a string).
3977 
3978    Not Collective
3979 
3980    Input Parameter:
3981 .  snes - nonlinear solver context
3982 
3983    Output Parameter:
3984 .  type - SNES method (a character string)
3985 
3986    Level: intermediate
3987 
3988 .keywords: SNES, nonlinear, get, type, name
3989 @*/
3990 PetscErrorCode  SNESGetType(SNES snes,SNESType *type)
3991 {
3992   PetscFunctionBegin;
3993   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
3994   PetscValidPointer(type,2);
3995   *type = ((PetscObject)snes)->type_name;
3996   PetscFunctionReturn(0);
3997 }
3998 
3999 #undef __FUNCT__
4000 #define __FUNCT__ "SNESSetSolution"
4001 /*@
4002   SNESSetSolution - Sets the solution vector for use by the SNES routines.
4003 
4004   Logically Collective on SNES and Vec
4005 
4006   Input Parameters:
4007 + snes - the SNES context obtained from SNESCreate()
4008 - u    - the solution vector
4009 
4010   Level: beginner
4011 
4012 .keywords: SNES, set, solution
4013 @*/
4014 PetscErrorCode SNESSetSolution(SNES snes, Vec u)
4015 {
4016   DM             dm;
4017   PetscErrorCode ierr;
4018 
4019   PetscFunctionBegin;
4020   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4021   PetscValidHeaderSpecific(u, VEC_CLASSID, 2);
4022   ierr = PetscObjectReference((PetscObject) u);CHKERRQ(ierr);
4023   ierr = VecDestroy(&snes->vec_sol);CHKERRQ(ierr);
4024 
4025   snes->vec_sol = u;
4026 
4027   ierr = SNESGetDM(snes, &dm);CHKERRQ(ierr);
4028   ierr = DMShellSetGlobalVector(dm, u);CHKERRQ(ierr);
4029   PetscFunctionReturn(0);
4030 }
4031 
4032 #undef __FUNCT__
4033 #define __FUNCT__ "SNESGetSolution"
4034 /*@
4035    SNESGetSolution - Returns the vector where the approximate solution is
4036    stored. This is the fine grid solution when using SNESSetGridSequence().
4037 
4038    Not Collective, but Vec is parallel if SNES is parallel
4039 
4040    Input Parameter:
4041 .  snes - the SNES context
4042 
4043    Output Parameter:
4044 .  x - the solution
4045 
4046    Level: intermediate
4047 
4048 .keywords: SNES, nonlinear, get, solution
4049 
4050 .seealso:  SNESGetSolutionUpdate(), SNESGetFunction()
4051 @*/
4052 PetscErrorCode  SNESGetSolution(SNES snes,Vec *x)
4053 {
4054   PetscFunctionBegin;
4055   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4056   PetscValidPointer(x,2);
4057   *x = snes->vec_sol;
4058   PetscFunctionReturn(0);
4059 }
4060 
4061 #undef __FUNCT__
4062 #define __FUNCT__ "SNESGetSolutionUpdate"
4063 /*@
4064    SNESGetSolutionUpdate - Returns the vector where the solution update is
4065    stored.
4066 
4067    Not Collective, but Vec is parallel if SNES is parallel
4068 
4069    Input Parameter:
4070 .  snes - the SNES context
4071 
4072    Output Parameter:
4073 .  x - the solution update
4074 
4075    Level: advanced
4076 
4077 .keywords: SNES, nonlinear, get, solution, update
4078 
4079 .seealso: SNESGetSolution(), SNESGetFunction()
4080 @*/
4081 PetscErrorCode  SNESGetSolutionUpdate(SNES snes,Vec *x)
4082 {
4083   PetscFunctionBegin;
4084   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4085   PetscValidPointer(x,2);
4086   *x = snes->vec_sol_update;
4087   PetscFunctionReturn(0);
4088 }
4089 
4090 #undef __FUNCT__
4091 #define __FUNCT__ "SNESGetFunction"
4092 /*@C
4093    SNESGetFunction - Returns the vector where the function is stored.
4094 
4095    Not Collective, but Vec is parallel if SNES is parallel. Collective if Vec is requested, but has not been created yet.
4096 
4097    Input Parameter:
4098 .  snes - the SNES context
4099 
4100    Output Parameter:
4101 +  r - the vector that is used to store residuals (or NULL if you don't want it)
4102 .  f - the function (or NULL if you don't want it); see SNESFunction for calling sequence details
4103 -  ctx - the function context (or NULL if you don't want it)
4104 
4105    Level: advanced
4106 
4107 .keywords: SNES, nonlinear, get, function
4108 
4109 .seealso: SNESSetFunction(), SNESGetSolution(), SNESFunction
4110 @*/
4111 PetscErrorCode  SNESGetFunction(SNES snes,Vec *r,PetscErrorCode (**f)(SNES,Vec,Vec,void*),void **ctx)
4112 {
4113   PetscErrorCode ierr;
4114   DM             dm;
4115 
4116   PetscFunctionBegin;
4117   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4118   if (r) {
4119     if (!snes->vec_func) {
4120       if (snes->vec_rhs) {
4121         ierr = VecDuplicate(snes->vec_rhs,&snes->vec_func);CHKERRQ(ierr);
4122       } else if (snes->vec_sol) {
4123         ierr = VecDuplicate(snes->vec_sol,&snes->vec_func);CHKERRQ(ierr);
4124       } else if (snes->dm) {
4125         ierr = DMCreateGlobalVector(snes->dm,&snes->vec_func);CHKERRQ(ierr);
4126       }
4127     }
4128     *r = snes->vec_func;
4129   }
4130   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
4131   ierr = DMSNESGetFunction(dm,f,ctx);CHKERRQ(ierr);
4132   PetscFunctionReturn(0);
4133 }
4134 
4135 /*@C
4136    SNESGetNGS - Returns the NGS function and context.
4137 
4138    Input Parameter:
4139 .  snes - the SNES context
4140 
4141    Output Parameter:
4142 +  f - the function (or NULL) see SNESNGSFunction for details
4143 -  ctx    - the function context (or NULL)
4144 
4145    Level: advanced
4146 
4147 .keywords: SNES, nonlinear, get, function
4148 
4149 .seealso: SNESSetNGS(), SNESGetFunction()
4150 @*/
4151 
4152 #undef __FUNCT__
4153 #define __FUNCT__ "SNESGetNGS"
4154 PetscErrorCode SNESGetNGS (SNES snes, PetscErrorCode (**f)(SNES, Vec, Vec, void*), void ** ctx)
4155 {
4156   PetscErrorCode ierr;
4157   DM             dm;
4158 
4159   PetscFunctionBegin;
4160   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4161   ierr = SNESGetDM(snes,&dm);CHKERRQ(ierr);
4162   ierr = DMSNESGetNGS(dm,f,ctx);CHKERRQ(ierr);
4163   PetscFunctionReturn(0);
4164 }
4165 
4166 #undef __FUNCT__
4167 #define __FUNCT__ "SNESSetOptionsPrefix"
4168 /*@C
4169    SNESSetOptionsPrefix - Sets the prefix used for searching for all
4170    SNES options in the database.
4171 
4172    Logically Collective on SNES
4173 
4174    Input Parameter:
4175 +  snes - the SNES context
4176 -  prefix - the prefix to prepend to all option names
4177 
4178    Notes:
4179    A hyphen (-) must NOT be given at the beginning of the prefix name.
4180    The first character of all runtime options is AUTOMATICALLY the hyphen.
4181 
4182    Level: advanced
4183 
4184 .keywords: SNES, set, options, prefix, database
4185 
4186 .seealso: SNESSetFromOptions()
4187 @*/
4188 PetscErrorCode  SNESSetOptionsPrefix(SNES snes,const char prefix[])
4189 {
4190   PetscErrorCode ierr;
4191 
4192   PetscFunctionBegin;
4193   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4194   ierr = PetscObjectSetOptionsPrefix((PetscObject)snes,prefix);CHKERRQ(ierr);
4195   if (!snes->ksp) {ierr = SNESGetKSP(snes,&snes->ksp);CHKERRQ(ierr);}
4196   if (snes->linesearch) {
4197     ierr = SNESGetLineSearch(snes,&snes->linesearch);CHKERRQ(ierr);
4198     ierr = PetscObjectSetOptionsPrefix((PetscObject)snes->linesearch,prefix);CHKERRQ(ierr);
4199   }
4200   ierr = KSPSetOptionsPrefix(snes->ksp,prefix);CHKERRQ(ierr);
4201   PetscFunctionReturn(0);
4202 }
4203 
4204 #undef __FUNCT__
4205 #define __FUNCT__ "SNESAppendOptionsPrefix"
4206 /*@C
4207    SNESAppendOptionsPrefix - Appends to the prefix used for searching for all
4208    SNES options in the database.
4209 
4210    Logically Collective on SNES
4211 
4212    Input Parameters:
4213 +  snes - the SNES context
4214 -  prefix - the prefix to prepend to all option names
4215 
4216    Notes:
4217    A hyphen (-) must NOT be given at the beginning of the prefix name.
4218    The first character of all runtime options is AUTOMATICALLY the hyphen.
4219 
4220    Level: advanced
4221 
4222 .keywords: SNES, append, options, prefix, database
4223 
4224 .seealso: SNESGetOptionsPrefix()
4225 @*/
4226 PetscErrorCode  SNESAppendOptionsPrefix(SNES snes,const char prefix[])
4227 {
4228   PetscErrorCode ierr;
4229 
4230   PetscFunctionBegin;
4231   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4232   ierr = PetscObjectAppendOptionsPrefix((PetscObject)snes,prefix);CHKERRQ(ierr);
4233   if (!snes->ksp) {ierr = SNESGetKSP(snes,&snes->ksp);CHKERRQ(ierr);}
4234   if (snes->linesearch) {
4235     ierr = SNESGetLineSearch(snes,&snes->linesearch);CHKERRQ(ierr);
4236     ierr = PetscObjectAppendOptionsPrefix((PetscObject)snes->linesearch,prefix);CHKERRQ(ierr);
4237   }
4238   ierr = KSPAppendOptionsPrefix(snes->ksp,prefix);CHKERRQ(ierr);
4239   PetscFunctionReturn(0);
4240 }
4241 
4242 #undef __FUNCT__
4243 #define __FUNCT__ "SNESGetOptionsPrefix"
4244 /*@C
4245    SNESGetOptionsPrefix - Sets the prefix used for searching for all
4246    SNES options in the database.
4247 
4248    Not Collective
4249 
4250    Input Parameter:
4251 .  snes - the SNES context
4252 
4253    Output Parameter:
4254 .  prefix - pointer to the prefix string used
4255 
4256    Notes: On the fortran side, the user should pass in a string 'prefix' of
4257    sufficient length to hold the prefix.
4258 
4259    Level: advanced
4260 
4261 .keywords: SNES, get, options, prefix, database
4262 
4263 .seealso: SNESAppendOptionsPrefix()
4264 @*/
4265 PetscErrorCode  SNESGetOptionsPrefix(SNES snes,const char *prefix[])
4266 {
4267   PetscErrorCode ierr;
4268 
4269   PetscFunctionBegin;
4270   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4271   ierr = PetscObjectGetOptionsPrefix((PetscObject)snes,prefix);CHKERRQ(ierr);
4272   PetscFunctionReturn(0);
4273 }
4274 
4275 
4276 #undef __FUNCT__
4277 #define __FUNCT__ "SNESRegister"
4278 /*@C
4279   SNESRegister - Adds a method to the nonlinear solver package.
4280 
4281    Not collective
4282 
4283    Input Parameters:
4284 +  name_solver - name of a new user-defined solver
4285 -  routine_create - routine to create method context
4286 
4287    Notes:
4288    SNESRegister() may be called multiple times to add several user-defined solvers.
4289 
4290    Sample usage:
4291 .vb
4292    SNESRegister("my_solver",MySolverCreate);
4293 .ve
4294 
4295    Then, your solver can be chosen with the procedural interface via
4296 $     SNESSetType(snes,"my_solver")
4297    or at runtime via the option
4298 $     -snes_type my_solver
4299 
4300    Level: advanced
4301 
4302     Note: If your function is not being put into a shared library then use SNESRegister() instead
4303 
4304 .keywords: SNES, nonlinear, register
4305 
4306 .seealso: SNESRegisterAll(), SNESRegisterDestroy()
4307 
4308   Level: advanced
4309 @*/
4310 PetscErrorCode  SNESRegister(const char sname[],PetscErrorCode (*function)(SNES))
4311 {
4312   PetscErrorCode ierr;
4313 
4314   PetscFunctionBegin;
4315   ierr = PetscFunctionListAdd(&SNESList,sname,function);CHKERRQ(ierr);
4316   PetscFunctionReturn(0);
4317 }
4318 
4319 #undef __FUNCT__
4320 #define __FUNCT__ "SNESTestLocalMin"
4321 PetscErrorCode  SNESTestLocalMin(SNES snes)
4322 {
4323   PetscErrorCode ierr;
4324   PetscInt       N,i,j;
4325   Vec            u,uh,fh;
4326   PetscScalar    value;
4327   PetscReal      norm;
4328 
4329   PetscFunctionBegin;
4330   ierr = SNESGetSolution(snes,&u);CHKERRQ(ierr);
4331   ierr = VecDuplicate(u,&uh);CHKERRQ(ierr);
4332   ierr = VecDuplicate(u,&fh);CHKERRQ(ierr);
4333 
4334   /* currently only works for sequential */
4335   ierr = PetscPrintf(PETSC_COMM_WORLD,"Testing FormFunction() for local min\n");CHKERRQ(ierr);
4336   ierr = VecGetSize(u,&N);CHKERRQ(ierr);
4337   for (i=0; i<N; i++) {
4338     ierr = VecCopy(u,uh);CHKERRQ(ierr);
4339     ierr = PetscPrintf(PETSC_COMM_WORLD,"i = %D\n",i);CHKERRQ(ierr);
4340     for (j=-10; j<11; j++) {
4341       value = PetscSign(j)*PetscExpReal(PetscAbs(j)-10.0);
4342       ierr  = VecSetValue(uh,i,value,ADD_VALUES);CHKERRQ(ierr);
4343       ierr  = SNESComputeFunction(snes,uh,fh);CHKERRQ(ierr);
4344       ierr  = VecNorm(fh,NORM_2,&norm);CHKERRQ(ierr);
4345       ierr  = PetscPrintf(PETSC_COMM_WORLD,"       j norm %D %18.16e\n",j,norm);CHKERRQ(ierr);
4346       value = -value;
4347       ierr  = VecSetValue(uh,i,value,ADD_VALUES);CHKERRQ(ierr);
4348     }
4349   }
4350   ierr = VecDestroy(&uh);CHKERRQ(ierr);
4351   ierr = VecDestroy(&fh);CHKERRQ(ierr);
4352   PetscFunctionReturn(0);
4353 }
4354 
4355 #undef __FUNCT__
4356 #define __FUNCT__ "SNESKSPSetUseEW"
4357 /*@
4358    SNESKSPSetUseEW - Sets SNES use Eisenstat-Walker method for
4359    computing relative tolerance for linear solvers within an inexact
4360    Newton method.
4361 
4362    Logically Collective on SNES
4363 
4364    Input Parameters:
4365 +  snes - SNES context
4366 -  flag - PETSC_TRUE or PETSC_FALSE
4367 
4368     Options Database:
4369 +  -snes_ksp_ew - use Eisenstat-Walker method for determining linear system convergence
4370 .  -snes_ksp_ew_version ver - version of  Eisenstat-Walker method
4371 .  -snes_ksp_ew_rtol0 <rtol0> - Sets rtol0
4372 .  -snes_ksp_ew_rtolmax <rtolmax> - Sets rtolmax
4373 .  -snes_ksp_ew_gamma <gamma> - Sets gamma
4374 .  -snes_ksp_ew_alpha <alpha> - Sets alpha
4375 .  -snes_ksp_ew_alpha2 <alpha2> - Sets alpha2
4376 -  -snes_ksp_ew_threshold <threshold> - Sets threshold
4377 
4378    Notes:
4379    Currently, the default is to use a constant relative tolerance for
4380    the inner linear solvers.  Alternatively, one can use the
4381    Eisenstat-Walker method, where the relative convergence tolerance
4382    is reset at each Newton iteration according progress of the nonlinear
4383    solver.
4384 
4385    Level: advanced
4386 
4387    Reference:
4388    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
4389    inexact Newton method", SISC 17 (1), pp.16-32, 1996.
4390 
4391 .keywords: SNES, KSP, Eisenstat, Walker, convergence, test, inexact, Newton
4392 
4393 .seealso: SNESKSPGetUseEW(), SNESKSPGetParametersEW(), SNESKSPSetParametersEW()
4394 @*/
4395 PetscErrorCode  SNESKSPSetUseEW(SNES snes,PetscBool flag)
4396 {
4397   PetscFunctionBegin;
4398   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4399   PetscValidLogicalCollectiveBool(snes,flag,2);
4400   snes->ksp_ewconv = flag;
4401   PetscFunctionReturn(0);
4402 }
4403 
4404 #undef __FUNCT__
4405 #define __FUNCT__ "SNESKSPGetUseEW"
4406 /*@
4407    SNESKSPGetUseEW - Gets if SNES is using Eisenstat-Walker method
4408    for computing relative tolerance for linear solvers within an
4409    inexact Newton method.
4410 
4411    Not Collective
4412 
4413    Input Parameter:
4414 .  snes - SNES context
4415 
4416    Output Parameter:
4417 .  flag - PETSC_TRUE or PETSC_FALSE
4418 
4419    Notes:
4420    Currently, the default is to use a constant relative tolerance for
4421    the inner linear solvers.  Alternatively, one can use the
4422    Eisenstat-Walker method, where the relative convergence tolerance
4423    is reset at each Newton iteration according progress of the nonlinear
4424    solver.
4425 
4426    Level: advanced
4427 
4428    Reference:
4429    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
4430    inexact Newton method", SISC 17 (1), pp.16-32, 1996.
4431 
4432 .keywords: SNES, KSP, Eisenstat, Walker, convergence, test, inexact, Newton
4433 
4434 .seealso: SNESKSPSetUseEW(), SNESKSPGetParametersEW(), SNESKSPSetParametersEW()
4435 @*/
4436 PetscErrorCode  SNESKSPGetUseEW(SNES snes, PetscBool  *flag)
4437 {
4438   PetscFunctionBegin;
4439   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4440   PetscValidPointer(flag,2);
4441   *flag = snes->ksp_ewconv;
4442   PetscFunctionReturn(0);
4443 }
4444 
4445 #undef __FUNCT__
4446 #define __FUNCT__ "SNESKSPSetParametersEW"
4447 /*@
4448    SNESKSPSetParametersEW - Sets parameters for Eisenstat-Walker
4449    convergence criteria for the linear solvers within an inexact
4450    Newton method.
4451 
4452    Logically Collective on SNES
4453 
4454    Input Parameters:
4455 +    snes - SNES context
4456 .    version - version 1, 2 (default is 2) or 3
4457 .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
4458 .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
4459 .    gamma - multiplicative factor for version 2 rtol computation
4460              (0 <= gamma2 <= 1)
4461 .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
4462 .    alpha2 - power for safeguard
4463 -    threshold - threshold for imposing safeguard (0 < threshold < 1)
4464 
4465    Note:
4466    Version 3 was contributed by Luis Chacon, June 2006.
4467 
4468    Use PETSC_DEFAULT to retain the default for any of the parameters.
4469 
4470    Level: advanced
4471 
4472    Reference:
4473    S. C. Eisenstat and H. F. Walker, "Choosing the forcing terms in an
4474    inexact Newton method", Utah State University Math. Stat. Dept. Res.
4475    Report 6/94/75, June, 1994, to appear in SIAM J. Sci. Comput.
4476 
4477 .keywords: SNES, KSP, Eisenstat, Walker, set, parameters
4478 
4479 .seealso: SNESKSPSetUseEW(), SNESKSPGetUseEW(), SNESKSPGetParametersEW()
4480 @*/
4481 PetscErrorCode  SNESKSPSetParametersEW(SNES snes,PetscInt version,PetscReal rtol_0,PetscReal rtol_max,PetscReal gamma,PetscReal alpha,PetscReal alpha2,PetscReal threshold)
4482 {
4483   SNESKSPEW *kctx;
4484 
4485   PetscFunctionBegin;
4486   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4487   kctx = (SNESKSPEW*)snes->kspconvctx;
4488   if (!kctx) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"No Eisenstat-Walker context existing");
4489   PetscValidLogicalCollectiveInt(snes,version,2);
4490   PetscValidLogicalCollectiveReal(snes,rtol_0,3);
4491   PetscValidLogicalCollectiveReal(snes,rtol_max,4);
4492   PetscValidLogicalCollectiveReal(snes,gamma,5);
4493   PetscValidLogicalCollectiveReal(snes,alpha,6);
4494   PetscValidLogicalCollectiveReal(snes,alpha2,7);
4495   PetscValidLogicalCollectiveReal(snes,threshold,8);
4496 
4497   if (version != PETSC_DEFAULT)   kctx->version   = version;
4498   if (rtol_0 != PETSC_DEFAULT)    kctx->rtol_0    = rtol_0;
4499   if (rtol_max != PETSC_DEFAULT)  kctx->rtol_max  = rtol_max;
4500   if (gamma != PETSC_DEFAULT)     kctx->gamma     = gamma;
4501   if (alpha != PETSC_DEFAULT)     kctx->alpha     = alpha;
4502   if (alpha2 != PETSC_DEFAULT)    kctx->alpha2    = alpha2;
4503   if (threshold != PETSC_DEFAULT) kctx->threshold = threshold;
4504 
4505   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);
4506   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);
4507   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);
4508   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);
4509   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);
4510   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);
4511   PetscFunctionReturn(0);
4512 }
4513 
4514 #undef __FUNCT__
4515 #define __FUNCT__ "SNESKSPGetParametersEW"
4516 /*@
4517    SNESKSPGetParametersEW - Gets parameters for Eisenstat-Walker
4518    convergence criteria for the linear solvers within an inexact
4519    Newton method.
4520 
4521    Not Collective
4522 
4523    Input Parameters:
4524      snes - SNES context
4525 
4526    Output Parameters:
4527 +    version - version 1, 2 (default is 2) or 3
4528 .    rtol_0 - initial relative tolerance (0 <= rtol_0 < 1)
4529 .    rtol_max - maximum relative tolerance (0 <= rtol_max < 1)
4530 .    gamma - multiplicative factor for version 2 rtol computation (0 <= gamma2 <= 1)
4531 .    alpha - power for version 2 rtol computation (1 < alpha <= 2)
4532 .    alpha2 - power for safeguard
4533 -    threshold - threshold for imposing safeguard (0 < threshold < 1)
4534 
4535    Level: advanced
4536 
4537 .keywords: SNES, KSP, Eisenstat, Walker, get, parameters
4538 
4539 .seealso: SNESKSPSetUseEW(), SNESKSPGetUseEW(), SNESKSPSetParametersEW()
4540 @*/
4541 PetscErrorCode  SNESKSPGetParametersEW(SNES snes,PetscInt *version,PetscReal *rtol_0,PetscReal *rtol_max,PetscReal *gamma,PetscReal *alpha,PetscReal *alpha2,PetscReal *threshold)
4542 {
4543   SNESKSPEW *kctx;
4544 
4545   PetscFunctionBegin;
4546   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4547   kctx = (SNESKSPEW*)snes->kspconvctx;
4548   if (!kctx) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_WRONGSTATE,"No Eisenstat-Walker context existing");
4549   if (version)   *version   = kctx->version;
4550   if (rtol_0)    *rtol_0    = kctx->rtol_0;
4551   if (rtol_max)  *rtol_max  = kctx->rtol_max;
4552   if (gamma)     *gamma     = kctx->gamma;
4553   if (alpha)     *alpha     = kctx->alpha;
4554   if (alpha2)    *alpha2    = kctx->alpha2;
4555   if (threshold) *threshold = kctx->threshold;
4556   PetscFunctionReturn(0);
4557 }
4558 
4559 #undef __FUNCT__
4560 #define __FUNCT__ "KSPPreSolve_SNESEW"
4561  PetscErrorCode KSPPreSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
4562 {
4563   PetscErrorCode ierr;
4564   SNESKSPEW      *kctx = (SNESKSPEW*)snes->kspconvctx;
4565   PetscReal      rtol  = PETSC_DEFAULT,stol;
4566 
4567   PetscFunctionBegin;
4568   if (!snes->ksp_ewconv) PetscFunctionReturn(0);
4569   if (!snes->iter) {
4570     rtol = kctx->rtol_0; /* first time in, so use the original user rtol */
4571     ierr = VecNorm(snes->vec_func,NORM_2,&kctx->norm_first);CHKERRQ(ierr);
4572   }
4573   else {
4574     if (kctx->version == 1) {
4575       rtol = (snes->norm - kctx->lresid_last)/kctx->norm_last;
4576       if (rtol < 0.0) rtol = -rtol;
4577       stol = PetscPowReal(kctx->rtol_last,kctx->alpha2);
4578       if (stol > kctx->threshold) rtol = PetscMax(rtol,stol);
4579     } else if (kctx->version == 2) {
4580       rtol = kctx->gamma * PetscPowReal(snes->norm/kctx->norm_last,kctx->alpha);
4581       stol = kctx->gamma * PetscPowReal(kctx->rtol_last,kctx->alpha);
4582       if (stol > kctx->threshold) rtol = PetscMax(rtol,stol);
4583     } else if (kctx->version == 3) { /* contributed by Luis Chacon, June 2006. */
4584       rtol = kctx->gamma * PetscPowReal(snes->norm/kctx->norm_last,kctx->alpha);
4585       /* safeguard: avoid sharp decrease of rtol */
4586       stol = kctx->gamma*PetscPowReal(kctx->rtol_last,kctx->alpha);
4587       stol = PetscMax(rtol,stol);
4588       rtol = PetscMin(kctx->rtol_0,stol);
4589       /* safeguard: avoid oversolving */
4590       stol = kctx->gamma*(kctx->norm_first*snes->rtol)/snes->norm;
4591       stol = PetscMax(rtol,stol);
4592       rtol = PetscMin(kctx->rtol_0,stol);
4593     } else SETERRQ1(PETSC_COMM_SELF,PETSC_ERR_ARG_OUTOFRANGE,"Only versions 1, 2 or 3 are supported: %D",kctx->version);
4594   }
4595   /* safeguard: avoid rtol greater than one */
4596   rtol = PetscMin(rtol,kctx->rtol_max);
4597   ierr = KSPSetTolerances(ksp,rtol,PETSC_DEFAULT,PETSC_DEFAULT,PETSC_DEFAULT);CHKERRQ(ierr);
4598   ierr = PetscInfo3(snes,"iter %D, Eisenstat-Walker (version %D) KSP rtol=%g\n",snes->iter,kctx->version,(double)rtol);CHKERRQ(ierr);
4599   PetscFunctionReturn(0);
4600 }
4601 
4602 #undef __FUNCT__
4603 #define __FUNCT__ "KSPPostSolve_SNESEW"
4604 PetscErrorCode KSPPostSolve_SNESEW(KSP ksp, Vec b, Vec x, SNES snes)
4605 {
4606   PetscErrorCode ierr;
4607   SNESKSPEW      *kctx = (SNESKSPEW*)snes->kspconvctx;
4608   PCSide         pcside;
4609   Vec            lres;
4610 
4611   PetscFunctionBegin;
4612   if (!snes->ksp_ewconv) PetscFunctionReturn(0);
4613   ierr = KSPGetTolerances(ksp,&kctx->rtol_last,0,0,0);CHKERRQ(ierr);
4614   kctx->norm_last = snes->norm;
4615   if (kctx->version == 1) {
4616     PC        pc;
4617     PetscBool isNone;
4618 
4619     ierr = KSPGetPC(ksp, &pc);CHKERRQ(ierr);
4620     ierr = PetscObjectTypeCompare((PetscObject) pc, PCNONE, &isNone);CHKERRQ(ierr);
4621     ierr = KSPGetPCSide(ksp,&pcside);CHKERRQ(ierr);
4622      if (pcside == PC_RIGHT || isNone) { /* XXX Should we also test KSP_UNPRECONDITIONED_NORM ? */
4623       /* KSP residual is true linear residual */
4624       ierr = KSPGetResidualNorm(ksp,&kctx->lresid_last);CHKERRQ(ierr);
4625     } else {
4626       /* KSP residual is preconditioned residual */
4627       /* compute true linear residual norm */
4628       ierr = VecDuplicate(b,&lres);CHKERRQ(ierr);
4629       ierr = MatMult(snes->jacobian,x,lres);CHKERRQ(ierr);
4630       ierr = VecAYPX(lres,-1.0,b);CHKERRQ(ierr);
4631       ierr = VecNorm(lres,NORM_2,&kctx->lresid_last);CHKERRQ(ierr);
4632       ierr = VecDestroy(&lres);CHKERRQ(ierr);
4633     }
4634   }
4635   PetscFunctionReturn(0);
4636 }
4637 
4638 #undef __FUNCT__
4639 #define __FUNCT__ "SNESGetKSP"
4640 /*@
4641    SNESGetKSP - Returns the KSP context for a SNES solver.
4642 
4643    Not Collective, but if SNES object is parallel, then KSP object is parallel
4644 
4645    Input Parameter:
4646 .  snes - the SNES context
4647 
4648    Output Parameter:
4649 .  ksp - the KSP context
4650 
4651    Notes:
4652    The user can then directly manipulate the KSP context to set various
4653    options, etc.  Likewise, the user can then extract and manipulate the
4654    PC contexts as well.
4655 
4656    Level: beginner
4657 
4658 .keywords: SNES, nonlinear, get, KSP, context
4659 
4660 .seealso: KSPGetPC(), SNESCreate(), KSPCreate(), SNESSetKSP()
4661 @*/
4662 PetscErrorCode  SNESGetKSP(SNES snes,KSP *ksp)
4663 {
4664   PetscErrorCode ierr;
4665 
4666   PetscFunctionBegin;
4667   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4668   PetscValidPointer(ksp,2);
4669 
4670   if (!snes->ksp) {
4671     PetscBool monitor = PETSC_FALSE;
4672 
4673     ierr = KSPCreate(PetscObjectComm((PetscObject)snes),&snes->ksp);CHKERRQ(ierr);
4674     ierr = PetscObjectIncrementTabLevel((PetscObject)snes->ksp,(PetscObject)snes,1);CHKERRQ(ierr);
4675     ierr = PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->ksp);CHKERRQ(ierr);
4676 
4677     ierr = KSPSetPreSolve(snes->ksp,(PetscErrorCode (*)(KSP,Vec,Vec,void*))KSPPreSolve_SNESEW,snes);CHKERRQ(ierr);
4678     ierr = KSPSetPostSolve(snes->ksp,(PetscErrorCode (*)(KSP,Vec,Vec,void*))KSPPostSolve_SNESEW,snes);CHKERRQ(ierr);
4679 
4680     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-ksp_monitor_snes",&monitor,NULL);CHKERRQ(ierr);
4681     if (monitor) {
4682       ierr = KSPMonitorSet(snes->ksp,KSPMonitorSNES,snes,NULL);CHKERRQ(ierr);
4683     }
4684     monitor = PETSC_FALSE;
4685     ierr = PetscOptionsGetBool(((PetscObject)snes)->prefix,"-ksp_monitor_snes_lg",&monitor,NULL);CHKERRQ(ierr);
4686     if (monitor) {
4687       PetscObject *objs;
4688       ierr = KSPMonitorSNESLGResidualNormCreate(0,0,PETSC_DECIDE,PETSC_DECIDE,600,600,&objs);CHKERRQ(ierr);
4689       objs[0] = (PetscObject) snes;
4690       ierr = KSPMonitorSet(snes->ksp,(PetscErrorCode (*)(KSP,PetscInt,PetscReal,void*))KSPMonitorSNESLGResidualNorm,objs,(PetscErrorCode (*)(void**))KSPMonitorSNESLGResidualNormDestroy);CHKERRQ(ierr);
4691     }
4692   }
4693   *ksp = snes->ksp;
4694   PetscFunctionReturn(0);
4695 }
4696 
4697 
4698 #include <petsc/private/dmimpl.h>
4699 #undef __FUNCT__
4700 #define __FUNCT__ "SNESSetDM"
4701 /*@
4702    SNESSetDM - Sets the DM that may be used by some preconditioners
4703 
4704    Logically Collective on SNES
4705 
4706    Input Parameters:
4707 +  snes - the preconditioner context
4708 -  dm - the dm
4709 
4710    Level: intermediate
4711 
4712 .seealso: SNESGetDM(), KSPSetDM(), KSPGetDM()
4713 @*/
4714 PetscErrorCode  SNESSetDM(SNES snes,DM dm)
4715 {
4716   PetscErrorCode ierr;
4717   KSP            ksp;
4718   DMSNES         sdm;
4719 
4720   PetscFunctionBegin;
4721   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4722   if (dm) {ierr = PetscObjectReference((PetscObject)dm);CHKERRQ(ierr);}
4723   if (snes->dm) {               /* Move the DMSNES context over to the new DM unless the new DM already has one */
4724     if (snes->dm->dmsnes && snes->dmAuto && !dm->dmsnes) {
4725       ierr = DMCopyDMSNES(snes->dm,dm);CHKERRQ(ierr);
4726       ierr = DMGetDMSNES(snes->dm,&sdm);CHKERRQ(ierr);
4727       if (sdm->originaldm == snes->dm) sdm->originaldm = dm; /* Grant write privileges to the replacement DM */
4728     }
4729     ierr = DMDestroy(&snes->dm);CHKERRQ(ierr);
4730   }
4731   snes->dm     = dm;
4732   snes->dmAuto = PETSC_FALSE;
4733 
4734   ierr = SNESGetKSP(snes,&ksp);CHKERRQ(ierr);
4735   ierr = KSPSetDM(ksp,dm);CHKERRQ(ierr);
4736   ierr = KSPSetDMActive(ksp,PETSC_FALSE);CHKERRQ(ierr);
4737   if (snes->pc) {
4738     ierr = SNESSetDM(snes->pc, snes->dm);CHKERRQ(ierr);
4739     ierr = SNESSetNPCSide(snes,snes->pcside);CHKERRQ(ierr);
4740   }
4741   PetscFunctionReturn(0);
4742 }
4743 
4744 #undef __FUNCT__
4745 #define __FUNCT__ "SNESGetDM"
4746 /*@
4747    SNESGetDM - Gets the DM that may be used by some preconditioners
4748 
4749    Not Collective but DM obtained is parallel on SNES
4750 
4751    Input Parameter:
4752 . snes - the preconditioner context
4753 
4754    Output Parameter:
4755 .  dm - the dm
4756 
4757    Level: intermediate
4758 
4759 .seealso: SNESSetDM(), KSPSetDM(), KSPGetDM()
4760 @*/
4761 PetscErrorCode  SNESGetDM(SNES snes,DM *dm)
4762 {
4763   PetscErrorCode ierr;
4764 
4765   PetscFunctionBegin;
4766   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4767   if (!snes->dm) {
4768     ierr         = DMShellCreate(PetscObjectComm((PetscObject)snes),&snes->dm);CHKERRQ(ierr);
4769     snes->dmAuto = PETSC_TRUE;
4770   }
4771   *dm = snes->dm;
4772   PetscFunctionReturn(0);
4773 }
4774 
4775 #undef __FUNCT__
4776 #define __FUNCT__ "SNESSetNPC"
4777 /*@
4778   SNESSetNPC - Sets the nonlinear preconditioner to be used.
4779 
4780   Collective on SNES
4781 
4782   Input Parameters:
4783 + snes - iterative context obtained from SNESCreate()
4784 - pc   - the preconditioner object
4785 
4786   Notes:
4787   Use SNESGetNPC() to retrieve the preconditioner context (for example,
4788   to configure it using the API).
4789 
4790   Level: developer
4791 
4792 .keywords: SNES, set, precondition
4793 .seealso: SNESGetNPC(), SNESHasNPC()
4794 @*/
4795 PetscErrorCode SNESSetNPC(SNES snes, SNES pc)
4796 {
4797   PetscErrorCode ierr;
4798 
4799   PetscFunctionBegin;
4800   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4801   PetscValidHeaderSpecific(pc, SNES_CLASSID, 2);
4802   PetscCheckSameComm(snes, 1, pc, 2);
4803   ierr     = PetscObjectReference((PetscObject) pc);CHKERRQ(ierr);
4804   ierr     = SNESDestroy(&snes->pc);CHKERRQ(ierr);
4805   snes->pc = pc;
4806   ierr     = PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->pc);CHKERRQ(ierr);
4807   PetscFunctionReturn(0);
4808 }
4809 
4810 #undef __FUNCT__
4811 #define __FUNCT__ "SNESGetNPC"
4812 /*@
4813   SNESGetNPC - Creates a nonlinear preconditioning solver (SNES) to be used to precondition the nonlinear solver.
4814 
4815   Not Collective
4816 
4817   Input Parameter:
4818 . snes - iterative context obtained from SNESCreate()
4819 
4820   Output Parameter:
4821 . pc - preconditioner context
4822 
4823   Notes: If a SNES was previously set with SNESSetNPC() then that SNES is returned.
4824 
4825   Level: developer
4826 
4827 .keywords: SNES, get, preconditioner
4828 .seealso: SNESSetNPC(), SNESHasNPC()
4829 @*/
4830 PetscErrorCode SNESGetNPC(SNES snes, SNES *pc)
4831 {
4832   PetscErrorCode ierr;
4833   const char     *optionsprefix;
4834 
4835   PetscFunctionBegin;
4836   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4837   PetscValidPointer(pc, 2);
4838   if (!snes->pc) {
4839     ierr = SNESCreate(PetscObjectComm((PetscObject)snes),&snes->pc);CHKERRQ(ierr);
4840     ierr = PetscObjectIncrementTabLevel((PetscObject)snes->pc,(PetscObject)snes,1);CHKERRQ(ierr);
4841     ierr = PetscLogObjectParent((PetscObject)snes,(PetscObject)snes->pc);CHKERRQ(ierr);
4842     ierr = SNESGetOptionsPrefix(snes,&optionsprefix);CHKERRQ(ierr);
4843     ierr = SNESSetOptionsPrefix(snes->pc,optionsprefix);CHKERRQ(ierr);
4844     ierr = SNESAppendOptionsPrefix(snes->pc,"npc_");CHKERRQ(ierr);
4845     ierr = SNESSetCountersReset(snes->pc,PETSC_FALSE);CHKERRQ(ierr);
4846   }
4847   *pc = snes->pc;
4848   PetscFunctionReturn(0);
4849 }
4850 
4851 #undef __FUNCT__
4852 #define __FUNCT__ "SNESHasNPC"
4853 /*@
4854   SNESHasNPC - Returns whether a nonlinear preconditioner exists
4855 
4856   Not Collective
4857 
4858   Input Parameter:
4859 . snes - iterative context obtained from SNESCreate()
4860 
4861   Output Parameter:
4862 . has_npc - whether the SNES has an NPC or not
4863 
4864   Level: developer
4865 
4866 .keywords: SNES, has, preconditioner
4867 .seealso: SNESSetNPC(), SNESGetNPC()
4868 @*/
4869 PetscErrorCode SNESHasNPC(SNES snes, PetscBool *has_npc)
4870 {
4871   PetscFunctionBegin;
4872   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4873   *has_npc = (PetscBool) (snes->pc != NULL);
4874   PetscFunctionReturn(0);
4875 }
4876 
4877 #undef __FUNCT__
4878 #define __FUNCT__ "SNESSetNPCSide"
4879 /*@
4880     SNESSetNPCSide - Sets the preconditioning side.
4881 
4882     Logically Collective on SNES
4883 
4884     Input Parameter:
4885 .   snes - iterative context obtained from SNESCreate()
4886 
4887     Output Parameter:
4888 .   side - the preconditioning side, where side is one of
4889 .vb
4890       PC_LEFT - left preconditioning (default)
4891       PC_RIGHT - right preconditioning
4892 .ve
4893 
4894     Options Database Keys:
4895 .   -snes_pc_side <right,left>
4896 
4897     Level: intermediate
4898 
4899 .keywords: SNES, set, right, left, side, preconditioner, flag
4900 
4901 .seealso: SNESGetNPCSide(), KSPSetPCSide()
4902 @*/
4903 PetscErrorCode  SNESSetNPCSide(SNES snes,PCSide side)
4904 {
4905   PetscFunctionBegin;
4906   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4907   PetscValidLogicalCollectiveEnum(snes,side,2);
4908   snes->pcside = side;
4909   PetscFunctionReturn(0);
4910 }
4911 
4912 #undef __FUNCT__
4913 #define __FUNCT__ "SNESGetNPCSide"
4914 /*@
4915     SNESGetNPCSide - Gets the preconditioning side.
4916 
4917     Not Collective
4918 
4919     Input Parameter:
4920 .   snes - iterative context obtained from SNESCreate()
4921 
4922     Output Parameter:
4923 .   side - the preconditioning side, where side is one of
4924 .vb
4925       PC_LEFT - left preconditioning (default)
4926       PC_RIGHT - right preconditioning
4927 .ve
4928 
4929     Level: intermediate
4930 
4931 .keywords: SNES, get, right, left, side, preconditioner, flag
4932 
4933 .seealso: SNESSetNPCSide(), KSPGetPCSide()
4934 @*/
4935 PetscErrorCode  SNESGetNPCSide(SNES snes,PCSide *side)
4936 {
4937   PetscFunctionBegin;
4938   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
4939   PetscValidPointer(side,2);
4940   *side = snes->pcside;
4941   PetscFunctionReturn(0);
4942 }
4943 
4944 #undef __FUNCT__
4945 #define __FUNCT__ "SNESSetLineSearch"
4946 /*@
4947   SNESSetLineSearch - Sets the linesearch on the SNES instance.
4948 
4949   Collective on SNES
4950 
4951   Input Parameters:
4952 + snes - iterative context obtained from SNESCreate()
4953 - linesearch   - the linesearch object
4954 
4955   Notes:
4956   Use SNESGetLineSearch() to retrieve the preconditioner context (for example,
4957   to configure it using the API).
4958 
4959   Level: developer
4960 
4961 .keywords: SNES, set, linesearch
4962 .seealso: SNESGetLineSearch()
4963 @*/
4964 PetscErrorCode SNESSetLineSearch(SNES snes, SNESLineSearch linesearch)
4965 {
4966   PetscErrorCode ierr;
4967 
4968   PetscFunctionBegin;
4969   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
4970   PetscValidHeaderSpecific(linesearch, SNESLINESEARCH_CLASSID, 2);
4971   PetscCheckSameComm(snes, 1, linesearch, 2);
4972   ierr = PetscObjectReference((PetscObject) linesearch);CHKERRQ(ierr);
4973   ierr = SNESLineSearchDestroy(&snes->linesearch);CHKERRQ(ierr);
4974 
4975   snes->linesearch = linesearch;
4976 
4977   ierr = PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->linesearch);CHKERRQ(ierr);
4978   PetscFunctionReturn(0);
4979 }
4980 
4981 #undef __FUNCT__
4982 #define __FUNCT__ "SNESGetLineSearch"
4983 /*@
4984   SNESGetLineSearch - Returns a pointer to the line search context set with SNESSetLineSearch()
4985   or creates a default line search instance associated with the SNES and returns it.
4986 
4987   Not Collective
4988 
4989   Input Parameter:
4990 . snes - iterative context obtained from SNESCreate()
4991 
4992   Output Parameter:
4993 . linesearch - linesearch context
4994 
4995   Level: beginner
4996 
4997 .keywords: SNES, get, linesearch
4998 .seealso: SNESSetLineSearch(), SNESLineSearchCreate()
4999 @*/
5000 PetscErrorCode SNESGetLineSearch(SNES snes, SNESLineSearch *linesearch)
5001 {
5002   PetscErrorCode ierr;
5003   const char     *optionsprefix;
5004 
5005   PetscFunctionBegin;
5006   PetscValidHeaderSpecific(snes, SNES_CLASSID, 1);
5007   PetscValidPointer(linesearch, 2);
5008   if (!snes->linesearch) {
5009     ierr = SNESGetOptionsPrefix(snes, &optionsprefix);CHKERRQ(ierr);
5010     ierr = SNESLineSearchCreate(PetscObjectComm((PetscObject)snes), &snes->linesearch);CHKERRQ(ierr);
5011     ierr = SNESLineSearchSetSNES(snes->linesearch, snes);CHKERRQ(ierr);
5012     ierr = SNESLineSearchAppendOptionsPrefix(snes->linesearch, optionsprefix);CHKERRQ(ierr);
5013     ierr = PetscObjectIncrementTabLevel((PetscObject) snes->linesearch, (PetscObject) snes, 1);CHKERRQ(ierr);
5014     ierr = PetscLogObjectParent((PetscObject)snes, (PetscObject)snes->linesearch);CHKERRQ(ierr);
5015   }
5016   *linesearch = snes->linesearch;
5017   PetscFunctionReturn(0);
5018 }
5019 
5020 #if defined(PETSC_HAVE_MATLAB_ENGINE)
5021 #include <mex.h>
5022 
5023 typedef struct {char *funcname; mxArray *ctx;} SNESMatlabContext;
5024 
5025 #undef __FUNCT__
5026 #define __FUNCT__ "SNESComputeFunction_Matlab"
5027 /*
5028    SNESComputeFunction_Matlab - Calls the function that has been set with SNESSetFunctionMatlab().
5029 
5030    Collective on SNES
5031 
5032    Input Parameters:
5033 +  snes - the SNES context
5034 -  x - input vector
5035 
5036    Output Parameter:
5037 .  y - function vector, as set by SNESSetFunction()
5038 
5039    Notes:
5040    SNESComputeFunction() is typically used within nonlinear solvers
5041    implementations, so most users would not generally call this routine
5042    themselves.
5043 
5044    Level: developer
5045 
5046 .keywords: SNES, nonlinear, compute, function
5047 
5048 .seealso: SNESSetFunction(), SNESGetFunction()
5049 */
5050 PetscErrorCode  SNESComputeFunction_Matlab(SNES snes,Vec x,Vec y, void *ctx)
5051 {
5052   PetscErrorCode    ierr;
5053   SNESMatlabContext *sctx = (SNESMatlabContext*)ctx;
5054   int               nlhs  = 1,nrhs = 5;
5055   mxArray           *plhs[1],*prhs[5];
5056   long long int     lx = 0,ly = 0,ls = 0;
5057 
5058   PetscFunctionBegin;
5059   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
5060   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
5061   PetscValidHeaderSpecific(y,VEC_CLASSID,3);
5062   PetscCheckSameComm(snes,1,x,2);
5063   PetscCheckSameComm(snes,1,y,3);
5064 
5065   /* call Matlab function in ctx with arguments x and y */
5066 
5067   ierr    = PetscMemcpy(&ls,&snes,sizeof(snes));CHKERRQ(ierr);
5068   ierr    = PetscMemcpy(&lx,&x,sizeof(x));CHKERRQ(ierr);
5069   ierr    = PetscMemcpy(&ly,&y,sizeof(x));CHKERRQ(ierr);
5070   prhs[0] = mxCreateDoubleScalar((double)ls);
5071   prhs[1] = mxCreateDoubleScalar((double)lx);
5072   prhs[2] = mxCreateDoubleScalar((double)ly);
5073   prhs[3] = mxCreateString(sctx->funcname);
5074   prhs[4] = sctx->ctx;
5075   ierr    = mexCallMATLAB(nlhs,plhs,nrhs,prhs,"PetscSNESComputeFunctionInternal");CHKERRQ(ierr);
5076   ierr    = mxGetScalar(plhs[0]);CHKERRQ(ierr);
5077   mxDestroyArray(prhs[0]);
5078   mxDestroyArray(prhs[1]);
5079   mxDestroyArray(prhs[2]);
5080   mxDestroyArray(prhs[3]);
5081   mxDestroyArray(plhs[0]);
5082   PetscFunctionReturn(0);
5083 }
5084 
5085 #undef __FUNCT__
5086 #define __FUNCT__ "SNESSetFunctionMatlab"
5087 /*
5088    SNESSetFunctionMatlab - Sets the function evaluation routine and function
5089    vector for use by the SNES routines in solving systems of nonlinear
5090    equations from MATLAB. Here the function is a string containing the name of a MATLAB function
5091 
5092    Logically Collective on SNES
5093 
5094    Input Parameters:
5095 +  snes - the SNES context
5096 .  r - vector to store function value
5097 -  f - function evaluation routine
5098 
5099    Notes:
5100    The Newton-like methods typically solve linear systems of the form
5101 $      f'(x) x = -f(x),
5102    where f'(x) denotes the Jacobian matrix and f(x) is the function.
5103 
5104    Level: beginner
5105 
5106    Developer Note:  This bleeds the allocated memory SNESMatlabContext *sctx;
5107 
5108 .keywords: SNES, nonlinear, set, function
5109 
5110 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction()
5111 */
5112 PetscErrorCode  SNESSetFunctionMatlab(SNES snes,Vec r,const char *f,mxArray *ctx)
5113 {
5114   PetscErrorCode    ierr;
5115   SNESMatlabContext *sctx;
5116 
5117   PetscFunctionBegin;
5118   /* currently sctx is memory bleed */
5119   ierr = PetscNew(&sctx);CHKERRQ(ierr);
5120   ierr = PetscStrallocpy(f,&sctx->funcname);CHKERRQ(ierr);
5121   /*
5122      This should work, but it doesn't
5123   sctx->ctx = ctx;
5124   mexMakeArrayPersistent(sctx->ctx);
5125   */
5126   sctx->ctx = mxDuplicateArray(ctx);
5127   ierr      = SNESSetFunction(snes,r,SNESComputeFunction_Matlab,sctx);CHKERRQ(ierr);
5128   PetscFunctionReturn(0);
5129 }
5130 
5131 #undef __FUNCT__
5132 #define __FUNCT__ "SNESComputeJacobian_Matlab"
5133 /*
5134    SNESComputeJacobian_Matlab - Calls the function that has been set with SNESSetJacobianMatlab().
5135 
5136    Collective on SNES
5137 
5138    Input Parameters:
5139 +  snes - the SNES context
5140 .  x - input vector
5141 .  A, B - the matrices
5142 -  ctx - user context
5143 
5144    Level: developer
5145 
5146 .keywords: SNES, nonlinear, compute, function
5147 
5148 .seealso: SNESSetFunction(), SNESGetFunction()
5149 @*/
5150 PetscErrorCode  SNESComputeJacobian_Matlab(SNES snes,Vec x,Mat A,Mat B,void *ctx)
5151 {
5152   PetscErrorCode    ierr;
5153   SNESMatlabContext *sctx = (SNESMatlabContext*)ctx;
5154   int               nlhs  = 2,nrhs = 6;
5155   mxArray           *plhs[2],*prhs[6];
5156   long long int     lx = 0,lA = 0,ls = 0, lB = 0;
5157 
5158   PetscFunctionBegin;
5159   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
5160   PetscValidHeaderSpecific(x,VEC_CLASSID,2);
5161 
5162   /* call Matlab function in ctx with arguments x and y */
5163 
5164   ierr    = PetscMemcpy(&ls,&snes,sizeof(snes));CHKERRQ(ierr);
5165   ierr    = PetscMemcpy(&lx,&x,sizeof(x));CHKERRQ(ierr);
5166   ierr    = PetscMemcpy(&lA,A,sizeof(x));CHKERRQ(ierr);
5167   ierr    = PetscMemcpy(&lB,B,sizeof(x));CHKERRQ(ierr);
5168   prhs[0] = mxCreateDoubleScalar((double)ls);
5169   prhs[1] = mxCreateDoubleScalar((double)lx);
5170   prhs[2] = mxCreateDoubleScalar((double)lA);
5171   prhs[3] = mxCreateDoubleScalar((double)lB);
5172   prhs[4] = mxCreateString(sctx->funcname);
5173   prhs[5] = sctx->ctx;
5174   ierr    = mexCallMATLAB(nlhs,plhs,nrhs,prhs,"PetscSNESComputeJacobianInternal");CHKERRQ(ierr);
5175   ierr    = mxGetScalar(plhs[0]);CHKERRQ(ierr);
5176   mxDestroyArray(prhs[0]);
5177   mxDestroyArray(prhs[1]);
5178   mxDestroyArray(prhs[2]);
5179   mxDestroyArray(prhs[3]);
5180   mxDestroyArray(prhs[4]);
5181   mxDestroyArray(plhs[0]);
5182   mxDestroyArray(plhs[1]);
5183   PetscFunctionReturn(0);
5184 }
5185 
5186 #undef __FUNCT__
5187 #define __FUNCT__ "SNESSetJacobianMatlab"
5188 /*
5189    SNESSetJacobianMatlab - Sets the Jacobian function evaluation routine and two empty Jacobian matrices
5190    vector for use by the SNES routines in solving systems of nonlinear
5191    equations from MATLAB. Here the function is a string containing the name of a MATLAB function
5192 
5193    Logically Collective on SNES
5194 
5195    Input Parameters:
5196 +  snes - the SNES context
5197 .  A,B - Jacobian matrices
5198 .  J - function evaluation routine
5199 -  ctx - user context
5200 
5201    Level: developer
5202 
5203    Developer Note:  This bleeds the allocated memory SNESMatlabContext *sctx;
5204 
5205 .keywords: SNES, nonlinear, set, function
5206 
5207 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction(), J
5208 */
5209 PetscErrorCode  SNESSetJacobianMatlab(SNES snes,Mat A,Mat B,const char *J,mxArray *ctx)
5210 {
5211   PetscErrorCode    ierr;
5212   SNESMatlabContext *sctx;
5213 
5214   PetscFunctionBegin;
5215   /* currently sctx is memory bleed */
5216   ierr = PetscNew(&sctx);CHKERRQ(ierr);
5217   ierr = PetscStrallocpy(J,&sctx->funcname);CHKERRQ(ierr);
5218   /*
5219      This should work, but it doesn't
5220   sctx->ctx = ctx;
5221   mexMakeArrayPersistent(sctx->ctx);
5222   */
5223   sctx->ctx = mxDuplicateArray(ctx);
5224   ierr      = SNESSetJacobian(snes,A,B,SNESComputeJacobian_Matlab,sctx);CHKERRQ(ierr);
5225   PetscFunctionReturn(0);
5226 }
5227 
5228 #undef __FUNCT__
5229 #define __FUNCT__ "SNESMonitor_Matlab"
5230 /*
5231    SNESMonitor_Matlab - Calls the function that has been set with SNESMonitorSetMatlab().
5232 
5233    Collective on SNES
5234 
5235 .seealso: SNESSetFunction(), SNESGetFunction()
5236 @*/
5237 PetscErrorCode  SNESMonitor_Matlab(SNES snes,PetscInt it, PetscReal fnorm, void *ctx)
5238 {
5239   PetscErrorCode    ierr;
5240   SNESMatlabContext *sctx = (SNESMatlabContext*)ctx;
5241   int               nlhs  = 1,nrhs = 6;
5242   mxArray           *plhs[1],*prhs[6];
5243   long long int     lx = 0,ls = 0;
5244   Vec               x  = snes->vec_sol;
5245 
5246   PetscFunctionBegin;
5247   PetscValidHeaderSpecific(snes,SNES_CLASSID,1);
5248 
5249   ierr    = PetscMemcpy(&ls,&snes,sizeof(snes));CHKERRQ(ierr);
5250   ierr    = PetscMemcpy(&lx,&x,sizeof(x));CHKERRQ(ierr);
5251   prhs[0] = mxCreateDoubleScalar((double)ls);
5252   prhs[1] = mxCreateDoubleScalar((double)it);
5253   prhs[2] = mxCreateDoubleScalar((double)fnorm);
5254   prhs[3] = mxCreateDoubleScalar((double)lx);
5255   prhs[4] = mxCreateString(sctx->funcname);
5256   prhs[5] = sctx->ctx;
5257   ierr    = mexCallMATLAB(nlhs,plhs,nrhs,prhs,"PetscSNESMonitorInternal");CHKERRQ(ierr);
5258   ierr    = mxGetScalar(plhs[0]);CHKERRQ(ierr);
5259   mxDestroyArray(prhs[0]);
5260   mxDestroyArray(prhs[1]);
5261   mxDestroyArray(prhs[2]);
5262   mxDestroyArray(prhs[3]);
5263   mxDestroyArray(prhs[4]);
5264   mxDestroyArray(plhs[0]);
5265   PetscFunctionReturn(0);
5266 }
5267 
5268 #undef __FUNCT__
5269 #define __FUNCT__ "SNESMonitorSetMatlab"
5270 /*
5271    SNESMonitorSetMatlab - Sets the monitor function from MATLAB
5272 
5273    Level: developer
5274 
5275    Developer Note:  This bleeds the allocated memory SNESMatlabContext *sctx;
5276 
5277 .keywords: SNES, nonlinear, set, function
5278 
5279 .seealso: SNESGetFunction(), SNESComputeFunction(), SNESSetJacobian(), SNESSetFunction()
5280 */
5281 PetscErrorCode  SNESMonitorSetMatlab(SNES snes,const char *f,mxArray *ctx)
5282 {
5283   PetscErrorCode    ierr;
5284   SNESMatlabContext *sctx;
5285 
5286   PetscFunctionBegin;
5287   /* currently sctx is memory bleed */
5288   ierr = PetscNew(&sctx);CHKERRQ(ierr);
5289   ierr = PetscStrallocpy(f,&sctx->funcname);CHKERRQ(ierr);
5290   /*
5291      This should work, but it doesn't
5292   sctx->ctx = ctx;
5293   mexMakeArrayPersistent(sctx->ctx);
5294   */
5295   sctx->ctx = mxDuplicateArray(ctx);
5296   ierr      = SNESMonitorSet(snes,SNESMonitor_Matlab,sctx,NULL);CHKERRQ(ierr);
5297   PetscFunctionReturn(0);
5298 }
5299 
5300 #endif
5301