Actual source code: view.c

  1: #include <petsc/private/viewerimpl.h>
  2: #include <petscdraw.h>

  4: PetscClassId PETSC_VIEWER_CLASSID;

  6: static PetscBool PetscViewerPackageInitialized = PETSC_FALSE;

  8: /*@C
  9:   PetscViewerFinalizePackage - This function destroys any global objects created in PETSc viewers. It is
 10:   called from `PetscFinalize()`.

 12:   Level: developer

 14: .seealso: [](sec_viewers), `PetscViewer`, `PetscFinalize()`, `PetscViewerInitializePackage()`
 15: @*/
 16: PetscErrorCode PetscViewerFinalizePackage(void)
 17: {
 18:   PetscFunctionBegin;
 19:   if (Petsc_Viewer_keyval != MPI_KEYVAL_INVALID) PetscCallMPI(MPI_Comm_free_keyval(&Petsc_Viewer_keyval));
 20:   if (Petsc_Viewer_Stdout_keyval != MPI_KEYVAL_INVALID) PetscCallMPI(MPI_Comm_free_keyval(&Petsc_Viewer_Stdout_keyval));
 21:   if (Petsc_Viewer_Stderr_keyval != MPI_KEYVAL_INVALID) PetscCallMPI(MPI_Comm_free_keyval(&Petsc_Viewer_Stderr_keyval));
 22:   if (Petsc_Viewer_Binary_keyval != MPI_KEYVAL_INVALID) PetscCallMPI(MPI_Comm_free_keyval(&Petsc_Viewer_Binary_keyval));
 23:   if (Petsc_Viewer_Draw_keyval != MPI_KEYVAL_INVALID) PetscCallMPI(MPI_Comm_free_keyval(&Petsc_Viewer_Draw_keyval));
 24: #if defined(PETSC_HAVE_HDF5)
 25:   if (Petsc_Viewer_HDF5_keyval != MPI_KEYVAL_INVALID) PetscCallMPI(MPI_Comm_free_keyval(&Petsc_Viewer_HDF5_keyval));
 26: #endif
 27: #if defined(PETSC_USE_SOCKETVIEWER)
 28:   if (Petsc_Viewer_Socket_keyval != MPI_KEYVAL_INVALID) PetscCallMPI(MPI_Comm_free_keyval(&Petsc_Viewer_Socket_keyval));
 29: #endif
 30:   PetscCall(PetscFunctionListDestroy(&PetscViewerList));
 31:   PetscViewerPackageInitialized = PETSC_FALSE;
 32:   PetscViewerRegisterAllCalled  = PETSC_FALSE;
 33:   PetscFunctionReturn(PETSC_SUCCESS);
 34: }

 36: /*@C
 37:   PetscViewerInitializePackage - This function initializes everything in the `PetscViewer` package.

 39:   Level: developer

 41: .seealso: [](sec_viewers), `PetscViewer`, `PetscInitialize()`, `PetscViewerFinalizePackage()`
 42: @*/
 43: PetscErrorCode PetscViewerInitializePackage(void)
 44: {
 45:   char      logList[256];
 46:   PetscBool opt, pkg;

 48:   PetscFunctionBegin;
 49:   if (PetscViewerPackageInitialized) PetscFunctionReturn(PETSC_SUCCESS);
 50:   PetscViewerPackageInitialized = PETSC_TRUE;
 51:   /* Register Classes */
 52:   PetscCall(PetscClassIdRegister("Viewer", &PETSC_VIEWER_CLASSID));
 53:   /* Register Constructors */
 54:   PetscCall(PetscViewerRegisterAll());
 55:   /* Process Info */
 56:   {
 57:     PetscClassId classids[1];

 59:     classids[0] = PETSC_VIEWER_CLASSID;
 60:     PetscCall(PetscInfoProcessClass("viewer", 1, classids));
 61:   }
 62:   /* Process summary exclusions */
 63:   PetscCall(PetscOptionsGetString(NULL, NULL, "-log_exclude", logList, sizeof(logList), &opt));
 64:   if (opt) {
 65:     PetscCall(PetscStrInList("viewer", logList, ',', &pkg));
 66:     if (pkg) PetscCall(PetscLogEventExcludeClass(PETSC_VIEWER_CLASSID));
 67:   }
 68: #if defined(PETSC_HAVE_MATHEMATICA)
 69:   PetscCall(PetscViewerMathematicaInitializePackage());
 70: #endif
 71:   /* Register package finalizer */
 72:   PetscCall(PetscRegisterFinalize(PetscViewerFinalizePackage));
 73:   PetscFunctionReturn(PETSC_SUCCESS);
 74: }

 76: /*@
 77:   PetscViewerDestroy - Destroys a `PetscViewer`.

 79:   Collective

 81:   Input Parameter:
 82: . viewer - the `PetscViewer` to be destroyed.

 84:   Level: beginner

 86: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerCreate()`, `PetscViewerSocketOpen()`, `PetscViewerASCIIOpen()`, `PetscViewerDrawOpen()`
 87: @*/
 88: PetscErrorCode PetscViewerDestroy(PetscViewer *viewer)
 89: {
 90:   PetscFunctionBegin;
 91:   if (!*viewer) PetscFunctionReturn(PETSC_SUCCESS);

 94:   PetscCall(PetscViewerFlush(*viewer));
 95:   if (--((PetscObject)*viewer)->refct > 0) {
 96:     *viewer = NULL;
 97:     PetscFunctionReturn(PETSC_SUCCESS);
 98:   }

100:   PetscCall(PetscObjectSAWsViewOff((PetscObject)*viewer));
101:   PetscTryTypeMethod(*viewer, destroy);
102:   PetscCall(PetscHeaderDestroy(viewer));
103:   PetscFunctionReturn(PETSC_SUCCESS);
104: }

106: /*@C
107:   PetscViewerAndFormatCreate - Creates a `PetscViewerAndFormat` struct.

109:   Collective

111:   Input Parameters:
112: + viewer - the viewer
113: - format - the format

115:   Output Parameter:
116: . vf - viewer and format object

118:   Level: developer

120:   Notes:
121:   This increases the reference count of the viewer.

123:   Use `PetscViewerAndFormatDestroy()` to free the struct

125:   This is used as the context variable for many of the `TS`, `SNES`, and `KSP` monitor functions

127:   This construct exists because it allows one to keep track of the use of a `PetscViewerFormat` without requiring the
128:   format in the viewer to be permanently changed.

130: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerAndFormat`, `PetscViewerFormat`, `PetscViewerSocketOpen()`, `PetscViewerASCIIOpen()`, `PetscViewerCreate()`,
131:           `PetscViewerDrawOpen()`, `PetscViewerAndFormatDestroy()`
132: @*/
133: PetscErrorCode PetscViewerAndFormatCreate(PetscViewer viewer, PetscViewerFormat format, PetscViewerAndFormat **vf)
134: {
135:   PetscFunctionBegin;
136:   PetscCall(PetscObjectReference((PetscObject)viewer));
137:   PetscCall(PetscNew(vf));
138:   (*vf)->viewer = viewer;
139:   (*vf)->format = format;
140:   (*vf)->data   = NULL;
141:   PetscFunctionReturn(PETSC_SUCCESS);
142: }

144: /*@C
145:   PetscViewerAndFormatDestroy - Destroys a `PetscViewerAndFormat` struct created with `PetscViewerAndFormatCreate()`

147:   Collective

149:   Input Parameter:
150: . vf - the `PetscViewerAndFormat` to be destroyed.

152:   Level: developer

154: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerAndFormat`, `PetscViewerFormat`, `PetscViewerAndFormatCreate()`, `PetscViewerSocketOpen()`,
155:           `PetscViewerASCIIOpen()`, `PetscViewerCreate()`, `PetscViewerDrawOpen()`
156: @*/
157: PetscErrorCode PetscViewerAndFormatDestroy(PetscViewerAndFormat **vf)
158: {
159:   PetscFunctionBegin;
160:   PetscCall(PetscViewerDestroy(&(*vf)->viewer));
161:   if ((*vf)->data_destroy) PetscCall((*vf)->data_destroy(&(*vf)->data));
162:   PetscCall(PetscFree(*vf));
163:   PetscFunctionReturn(PETSC_SUCCESS);
164: }

166: /*@
167:   PetscViewerGetType - Returns the type of a `PetscViewer`.

169:   Not Collective

171:   Input Parameter:
172: . viewer - the `PetscViewer`

174:   Output Parameter:
175: . type - `PetscViewerType`

177:   Level: intermediate

179:   Note:
180:   `PetscViewerType` is actually a string

182: .seealso: [](sec_viewers), `PetscViewerType`, `PetscViewer`, `PetscViewerCreate()`, `PetscViewerSetType()`
183: @*/
184: PetscErrorCode PetscViewerGetType(PetscViewer viewer, PetscViewerType *type)
185: {
186:   PetscFunctionBegin;
188:   PetscAssertPointer(type, 2);
189:   *type = ((PetscObject)viewer)->type_name;
190:   PetscFunctionReturn(PETSC_SUCCESS);
191: }

193: /*@
194:   PetscViewerSetOptionsPrefix - Sets the prefix used for searching for
195:   `PetscViewer` options in the database during `PetscViewerSetFromOptions()`.

197:   Logically Collective

199:   Input Parameters:
200: + viewer - the `PetscViewer` context
201: - prefix - the prefix to prepend to all option names

203:   Note:
204:   A hyphen (-) must NOT be given at the beginning of the prefix name.
205:   The first character of all runtime options is AUTOMATICALLY the hyphen.

207:   Level: advanced

209: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerSetFromOptions()`, `PetscViewerAppendOptionsPrefix()`
210: @*/
211: PetscErrorCode PetscViewerSetOptionsPrefix(PetscViewer viewer, const char prefix[])
212: {
213:   PetscFunctionBegin;
215:   PetscCall(PetscObjectSetOptionsPrefix((PetscObject)viewer, prefix));
216:   PetscFunctionReturn(PETSC_SUCCESS);
217: }

219: /*@
220:   PetscViewerAppendOptionsPrefix - Appends to the prefix used for searching for
221:   `PetscViewer` options in the database during `PetscViewerSetFromOptions()`.

223:   Logically Collective

225:   Input Parameters:
226: + viewer - the `PetscViewer` context
227: - prefix - the prefix to prepend to all option names

229:   Level: advanced

231:   Note:
232:   A hyphen (-) must NOT be given at the beginning of the prefix name.
233:   The first character of all runtime options is AUTOMATICALLY the hyphen.

235: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerGetOptionsPrefix()`, `PetscViewerSetOptionsPrefix()`
236: @*/
237: PetscErrorCode PetscViewerAppendOptionsPrefix(PetscViewer viewer, const char prefix[])
238: {
239:   PetscFunctionBegin;
241:   PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)viewer, prefix));
242:   PetscFunctionReturn(PETSC_SUCCESS);
243: }

245: /*@
246:   PetscViewerGetOptionsPrefix - Gets the prefix used for searching for
247:   `PetscViewer` options in the database during `PetscViewerSetFromOptions()`.

249:   Not Collective

251:   Input Parameter:
252: . viewer - the `PetscViewer` context

254:   Output Parameter:
255: . prefix - pointer to the prefix string used

257:   Level: advanced

259: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerAppendOptionsPrefix()`, `PetscViewerSetOptionsPrefix()`
260: @*/
261: PetscErrorCode PetscViewerGetOptionsPrefix(PetscViewer viewer, const char *prefix[])
262: {
263:   PetscFunctionBegin;
265:   PetscCall(PetscObjectGetOptionsPrefix((PetscObject)viewer, prefix));
266:   PetscFunctionReturn(PETSC_SUCCESS);
267: }

269: /*@
270:   PetscViewerSetUp - Sets up the internal viewer data structures for the later use.

272:   Collective

274:   Input Parameter:
275: . viewer - the `PetscViewer` context

277:   Level: advanced

279:   Note:
280:   For basic use of the `PetscViewer` classes the user need not explicitly call
281:   `PetscViewerSetUp()`, since these actions will happen automatically.

283: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerCreate()`, `PetscViewerDestroy()`
284: @*/
285: PetscErrorCode PetscViewerSetUp(PetscViewer viewer)
286: {
287:   PetscFunctionBegin;
289:   if (viewer->setupcalled) PetscFunctionReturn(PETSC_SUCCESS);
290:   PetscTryTypeMethod(viewer, setup);
291:   viewer->setupcalled = PETSC_TRUE;
292:   PetscFunctionReturn(PETSC_SUCCESS);
293: }

295: /*@
296:   PetscViewerViewFromOptions - View from the viewer based on options in the options database

298:   Collective

300:   Input Parameters:
301: + A    - the `PetscViewer` context
302: . obj  - Optional object that provides the prefix for the option names
303: - name - command line option

305:   Level: intermediate

307:   Note:
308:   See `PetscObjectViewFromOptions()` for details on the viewers and formats support via this interface

310: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerView`, `PetscObjectViewFromOptions()`, `PetscViewerCreate()`
311: @*/
312: PetscErrorCode PetscViewerViewFromOptions(PetscViewer A, PetscObject obj, const char name[])
313: {
314:   PetscFunctionBegin;
316:   PetscCall(PetscObjectViewFromOptions((PetscObject)A, obj, name));
317:   PetscFunctionReturn(PETSC_SUCCESS);
318: }

320: /*@
321:   PetscViewerView - Visualizes a viewer object.

323:   Collective

325:   Input Parameters:
326: + v      - the viewer to be viewed
327: - viewer - visualization context

329:   Level: beginner

331: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerPushFormat()`, `PetscViewerASCIIOpen()`, `PetscViewerDrawOpen()`,
332:           `PetscViewerSocketOpen()`, `PetscViewerBinaryOpen()`, `PetscViewerLoad()`
333: @*/
334: PetscErrorCode PetscViewerView(PetscViewer v, PetscViewer viewer)
335: {
336:   PetscBool         iascii;
337:   PetscViewerFormat format;
338: #if defined(PETSC_HAVE_SAWS)
339:   PetscBool issaws;
340: #endif

342:   PetscFunctionBegin;
345:   if (!viewer) PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)v), &viewer));
347:   PetscCheckSameComm(v, 1, viewer, 2);

349:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
350: #if defined(PETSC_HAVE_SAWS)
351:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSAWS, &issaws));
352: #endif
353:   if (iascii) {
354:     PetscCall(PetscViewerGetFormat(viewer, &format));
355:     PetscCall(PetscObjectPrintClassNamePrefixType((PetscObject)v, viewer));
356:     if (format == PETSC_VIEWER_DEFAULT || format == PETSC_VIEWER_ASCII_INFO || format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
357:       if (v->format) PetscCall(PetscViewerASCIIPrintf(viewer, "  Viewer format = %s\n", PetscViewerFormats[v->format]));
358:       PetscCall(PetscViewerASCIIPushTab(viewer));
359:       PetscTryTypeMethod(v, view, viewer);
360:       PetscCall(PetscViewerASCIIPopTab(viewer));
361:     }
362: #if defined(PETSC_HAVE_SAWS)
363:   } else if (issaws) {
364:     if (!((PetscObject)v)->amsmem) {
365:       PetscCall(PetscObjectViewSAWs((PetscObject)v, viewer));
366:       PetscTryTypeMethod(v, view, viewer);
367:     }
368: #endif
369:   }
370:   PetscFunctionReturn(PETSC_SUCCESS);
371: }

373: /*@C
374:   PetscViewerRead - Reads data from a `PetscViewer`

376:   Collective

378:   Input Parameters:
379: + viewer - The viewer
380: . data   - Location to write the data, treated as an array of the type defined by `datatype`
381: . num    - Number of items of data to read
382: - dtype  - Type of data to read

384:   Output Parameter:
385: . count - number of items of data actually read, or `NULL`

387:   Level: beginner

389:   Notes:
390:   If datatype is `PETSC_STRING` and `num` is negative, reads until a newline character is found,
391:   until a maximum of (-num - 1) chars.

393:   Only certain viewers, such as `PETSCVIEWERBINARY` can be read from, see `PetscViewerReadable()`

395: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerASCIIOpen()`, `PetscViewerPushFormat()`, `PetscViewerDestroy()`,
396:           `PetscViewerReadable()`, `PetscViewerBinaryGetDescriptor()`,
397:           `PetscViewerBinaryGetInfoPointer()`, `PetscFileMode`
398: @*/
399: PetscErrorCode PetscViewerRead(PetscViewer viewer, void *data, PetscInt num, PetscInt *count, PetscDataType dtype)
400: {
401:   PetscFunctionBegin;
403:   if (dtype == PETSC_STRING) {
404:     PetscInt c, i = 0, cnt;
405:     char    *s = (char *)data;
406:     if (num >= 0) {
407:       for (c = 0; c < num; c++) {
408:         /* Skip leading whitespaces */
409:         do {
410:           PetscUseTypeMethod(viewer, read, &s[i], 1, &cnt, PETSC_CHAR);
411:           if (!cnt) break;
412:         } while (s[i] == '\n' || s[i] == '\t' || s[i] == ' ' || s[i] == '\0' || s[i] == '\v' || s[i] == '\f' || s[i] == '\r');
413:         i++;
414:         /* Read strings one char at a time */
415:         do {
416:           PetscUseTypeMethod(viewer, read, &s[i++], 1, &cnt, PETSC_CHAR);
417:           if (!cnt) break;
418:         } while (s[i - 1] != '\n' && s[i - 1] != '\t' && s[i - 1] != ' ' && s[i - 1] != '\0' && s[i - 1] != '\v' && s[i - 1] != '\f' && s[i - 1] != '\r');
419:         /* Terminate final string */
420:         if (c == num - 1) s[i - 1] = '\0';
421:       }
422:     } else {
423:       /* Read until a \n is encountered (-num is the max size allowed) */
424:       do {
425:         PetscUseTypeMethod(viewer, read, &s[i++], 1, &cnt, PETSC_CHAR);
426:         if (i == -num || !cnt) break;
427:       } while (s[i - 1] != '\n');
428:       /* Terminate final string */
429:       s[i - 1] = '\0';
430:       c        = i;
431:     }
432:     if (count) *count = c;
433:     else PetscCheck(c >= num, PetscObjectComm((PetscObject)viewer), PETSC_ERR_FILE_READ, "Insufficient data, only read %" PetscInt_FMT " < %" PetscInt_FMT " strings", c, num);
434:   } else PetscUseTypeMethod(viewer, read, data, num, count, dtype);
435:   PetscFunctionReturn(PETSC_SUCCESS);
436: }

438: /*@
439:   PetscViewerReadable - Return a flag whether the viewer can be read from with `PetscViewerRead()`

441:   Not Collective

443:   Input Parameter:
444: . viewer - the `PetscViewer` context

446:   Output Parameter:
447: . flg - `PETSC_TRUE` if the viewer is readable, `PETSC_FALSE` otherwise

449:   Level: intermediate

451:   Note:
452:   `PETSC_TRUE` means that viewer's `PetscViewerType` supports reading, that is `PetscViewerRead()`, (this holds e.g. for `PETSCVIEWERBINARY`)
453:   and the viewer is in a mode allowing reading, i.e. `PetscViewerFileGetMode()`
454:   returns one of `FILE_MODE_READ`, `FILE_MODE_UPDATE`, `FILE_MODE_APPEND_UPDATE`.

456: .seealso: [](sec_viewers), `PetscViewerRead()`, `PetscViewer`, `PetscViewerWritable()`, `PetscViewerCheckReadable()`, `PetscViewerCreate()`, `PetscViewerFileSetMode()`, `PetscViewerFileSetType()`
457: @*/
458: PetscErrorCode PetscViewerReadable(PetscViewer viewer, PetscBool *flg)
459: {
460:   PetscFileMode mode;
461:   PetscErrorCode (*f)(PetscViewer, PetscFileMode *) = NULL;

463:   PetscFunctionBegin;
465:   PetscAssertPointer(flg, 2);
466:   PetscCall(PetscObjectQueryFunction((PetscObject)viewer, "PetscViewerFileGetMode_C", &f));
467:   *flg = PETSC_FALSE;
468:   if (!f) PetscFunctionReturn(PETSC_SUCCESS);
469:   PetscCall((*f)(viewer, &mode));
470:   switch (mode) {
471:   case FILE_MODE_READ:
472:   case FILE_MODE_UPDATE:
473:   case FILE_MODE_APPEND_UPDATE:
474:     *flg = PETSC_TRUE;
475:   default:
476:     break;
477:   }
478:   PetscFunctionReturn(PETSC_SUCCESS);
479: }

481: /*@
482:   PetscViewerWritable - Return a flag whether the viewer can be written to with `PetscViewerWrite()`

484:   Not Collective

486:   Input Parameter:
487: . viewer - the `PetscViewer` context

489:   Output Parameter:
490: . flg - `PETSC_TRUE` if the viewer is writable, `PETSC_FALSE` otherwise

492:   Level: intermediate

494:   Note:
495:   `PETSC_TRUE` means viewer is in a mode allowing writing, i.e. `PetscViewerFileGetMode()`
496:   returns one of `FILE_MODE_WRITE`, `FILE_MODE_APPEND`, `FILE_MODE_UPDATE`, `FILE_MODE_APPEND_UPDATE`.

498: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerReadable()`, `PetscViewerCheckWritable()`, `PetscViewerCreate()`, `PetscViewerFileSetMode()`, `PetscViewerFileSetType()`
499: @*/
500: PetscErrorCode PetscViewerWritable(PetscViewer viewer, PetscBool *flg)
501: {
502:   PetscFileMode mode;
503:   PetscErrorCode (*f)(PetscViewer, PetscFileMode *) = NULL;

505:   PetscFunctionBegin;
507:   PetscAssertPointer(flg, 2);
508:   PetscCall(PetscObjectQueryFunction((PetscObject)viewer, "PetscViewerFileGetMode_C", &f));
509:   *flg = PETSC_TRUE;
510:   if (!f) PetscFunctionReturn(PETSC_SUCCESS);
511:   PetscCall((*f)(viewer, &mode));
512:   if (mode == FILE_MODE_READ) *flg = PETSC_FALSE;
513:   PetscFunctionReturn(PETSC_SUCCESS);
514: }

516: /*@
517:   PetscViewerCheckReadable - Check whether the viewer can be read from, generates an error if not

519:   Collective

521:   Input Parameter:
522: . viewer - the `PetscViewer` context

524:   Level: intermediate

526: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerReadable()`, `PetscViewerCheckWritable()`, `PetscViewerCreate()`, `PetscViewerFileSetMode()`, `PetscViewerFileSetType()`
527: @*/
528: PetscErrorCode PetscViewerCheckReadable(PetscViewer viewer)
529: {
530:   PetscBool flg;

532:   PetscFunctionBegin;
534:   PetscCall(PetscViewerReadable(viewer, &flg));
535:   PetscCheck(flg, PetscObjectComm((PetscObject)viewer), PETSC_ERR_SUP, "Viewer doesn't support reading, or is not in reading mode (FILE_MODE_READ, FILE_MODE_UPDATE, FILE_MODE_APPEND_UPDATE)");
536:   PetscFunctionReturn(PETSC_SUCCESS);
537: }

539: /*@
540:   PetscViewerCheckWritable - Check whether the viewer can be written to, generates an error if not

542:   Collective

544:   Input Parameter:
545: . viewer - the `PetscViewer` context

547:   Level: intermediate

549: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerWritable()`, `PetscViewerCheckReadable()`, `PetscViewerCreate()`, `PetscViewerFileSetMode()`, `PetscViewerFileSetType()`
550: @*/
551: PetscErrorCode PetscViewerCheckWritable(PetscViewer viewer)
552: {
553:   PetscBool flg;

555:   PetscFunctionBegin;
557:   PetscCall(PetscViewerWritable(viewer, &flg));
558:   PetscCheck(flg, PetscObjectComm((PetscObject)viewer), PETSC_ERR_SUP, "Viewer doesn't support writing, or is in FILE_MODE_READ mode");
559:   PetscFunctionReturn(PETSC_SUCCESS);
560: }