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:   PetscCall(PetscFree(*vf));
162:   PetscFunctionReturn(PETSC_SUCCESS);
163: }

165: /*@
166:   PetscViewerGetType - Returns the type of a `PetscViewer`.

168:   Not Collective

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

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

176:   Level: intermediate

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

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

192: /*@
193:   PetscViewerSetOptionsPrefix - Sets the prefix used for searching for
194:   `PetscViewer` options in the database during `PetscViewerSetFromOptions()`.

196:   Logically Collective

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

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

206:   Level: advanced

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

218: /*@
219:   PetscViewerAppendOptionsPrefix - Appends to the prefix used for searching for
220:   `PetscViewer` options in the database during `PetscViewerSetFromOptions()`.

222:   Logically Collective

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

228:   Level: advanced

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

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

244: /*@
245:   PetscViewerGetOptionsPrefix - Gets the prefix used for searching for
246:   `PetscViewer` options in the database during `PetscViewerSetFromOptions()`.

248:   Not Collective

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

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

256:   Level: advanced

258:   Fortran Notes:
259:   The user should pass in a string 'prefix' of sufficient length to hold the prefix.

261: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerAppendOptionsPrefix()`, `PetscViewerSetOptionsPrefix()`
262: @*/
263: PetscErrorCode PetscViewerGetOptionsPrefix(PetscViewer viewer, const char *prefix[])
264: {
265:   PetscFunctionBegin;
267:   PetscCall(PetscObjectGetOptionsPrefix((PetscObject)viewer, prefix));
268:   PetscFunctionReturn(PETSC_SUCCESS);
269: }

271: /*@
272:   PetscViewerSetUp - Sets up the internal viewer data structures for the later use.

274:   Collective

276:   Input Parameter:
277: . viewer - the `PetscViewer` context

279:   Level: advanced

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

285: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerCreate()`, `PetscViewerDestroy()`
286: @*/
287: PetscErrorCode PetscViewerSetUp(PetscViewer viewer)
288: {
289:   PetscFunctionBegin;
291:   if (viewer->setupcalled) PetscFunctionReturn(PETSC_SUCCESS);
292:   PetscTryTypeMethod(viewer, setup);
293:   viewer->setupcalled = PETSC_TRUE;
294:   PetscFunctionReturn(PETSC_SUCCESS);
295: }

297: /*@
298:   PetscViewerViewFromOptions - View from the viewer based on options in the options database

300:   Collective

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

307:   Level: intermediate

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

312: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerView`, `PetscObjectViewFromOptions()`, `PetscViewerCreate()`
313: @*/
314: PetscErrorCode PetscViewerViewFromOptions(PetscViewer A, PetscObject obj, const char name[])
315: {
316:   PetscFunctionBegin;
318:   PetscCall(PetscObjectViewFromOptions((PetscObject)A, obj, name));
319:   PetscFunctionReturn(PETSC_SUCCESS);
320: }

322: /*@
323:   PetscViewerView - Visualizes a viewer object.

325:   Collective

327:   Input Parameters:
328: + v      - the viewer to be viewed
329: - viewer - visualization context

331:   Level: beginner

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

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

351:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
352: #if defined(PETSC_HAVE_SAWS)
353:   PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERSAWS, &issaws));
354: #endif
355:   if (iascii) {
356:     PetscCall(PetscViewerGetFormat(viewer, &format));
357:     PetscCall(PetscObjectPrintClassNamePrefixType((PetscObject)v, viewer));
358:     if (format == PETSC_VIEWER_DEFAULT || format == PETSC_VIEWER_ASCII_INFO || format == PETSC_VIEWER_ASCII_INFO_DETAIL) {
359:       if (v->format) PetscCall(PetscViewerASCIIPrintf(viewer, "  Viewer format = %s\n", PetscViewerFormats[v->format]));
360:       PetscCall(PetscViewerASCIIPushTab(viewer));
361:       PetscTryTypeMethod(v, view, viewer);
362:       PetscCall(PetscViewerASCIIPopTab(viewer));
363:     }
364: #if defined(PETSC_HAVE_SAWS)
365:   } else if (issaws) {
366:     if (!((PetscObject)v)->amsmem) {
367:       PetscCall(PetscObjectViewSAWs((PetscObject)v, viewer));
368:       PetscTryTypeMethod(v, view, viewer);
369:     }
370: #endif
371:   }
372:   PetscFunctionReturn(PETSC_SUCCESS);
373: }

375: /*@C
376:   PetscViewerRead - Reads data from a `PetscViewer`

378:   Collective

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

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

389:   Level: beginner

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

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

397: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerASCIIOpen()`, `PetscViewerPushFormat()`, `PetscViewerDestroy()`,
398:           `PetscViewerReadable()`, `PetscViewerBinaryGetDescriptor()`,
399:           `PetscViewerBinaryGetInfoPointer()`, `PetscFileMode`
400: @*/
401: PetscErrorCode PetscViewerRead(PetscViewer viewer, void *data, PetscInt num, PetscInt *count, PetscDataType dtype)
402: {
403:   PetscFunctionBegin;
405:   if (dtype == PETSC_STRING) {
406:     PetscInt c, i = 0, cnt;
407:     char    *s = (char *)data;
408:     if (num >= 0) {
409:       for (c = 0; c < num; c++) {
410:         /* Skip leading whitespaces */
411:         do {
412:           PetscUseTypeMethod(viewer, read, &s[i], 1, &cnt, PETSC_CHAR);
413:           if (!cnt) break;
414:         } while (s[i] == '\n' || s[i] == '\t' || s[i] == ' ' || s[i] == '\0' || s[i] == '\v' || s[i] == '\f' || s[i] == '\r');
415:         i++;
416:         /* Read strings one char at a time */
417:         do {
418:           PetscUseTypeMethod(viewer, read, &s[i++], 1, &cnt, PETSC_CHAR);
419:           if (!cnt) break;
420:         } 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');
421:         /* Terminate final string */
422:         if (c == num - 1) s[i - 1] = '\0';
423:       }
424:     } else {
425:       /* Read until a \n is encountered (-num is the max size allowed) */
426:       do {
427:         PetscUseTypeMethod(viewer, read, &s[i++], 1, &cnt, PETSC_CHAR);
428:         if (i == -num || !cnt) break;
429:       } while (s[i - 1] != '\n');
430:       /* Terminate final string */
431:       s[i - 1] = '\0';
432:       c        = i;
433:     }
434:     if (count) *count = c;
435:     else PetscCheck(c >= num, PetscObjectComm((PetscObject)viewer), PETSC_ERR_FILE_READ, "Insufficient data, only read %" PetscInt_FMT " < %" PetscInt_FMT " strings", c, num);
436:   } else PetscUseTypeMethod(viewer, read, data, num, count, dtype);
437:   PetscFunctionReturn(PETSC_SUCCESS);
438: }

440: /*@
441:   PetscViewerReadable - Return a flag whether the viewer can be read from with `PetscViewerRead()`

443:   Not Collective

445:   Input Parameter:
446: . viewer - the `PetscViewer` context

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

451:   Level: intermediate

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

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

465:   PetscFunctionBegin;
467:   PetscAssertPointer(flg, 2);
468:   PetscCall(PetscObjectQueryFunction((PetscObject)viewer, "PetscViewerFileGetMode_C", &f));
469:   *flg = PETSC_FALSE;
470:   if (!f) PetscFunctionReturn(PETSC_SUCCESS);
471:   PetscCall((*f)(viewer, &mode));
472:   switch (mode) {
473:   case FILE_MODE_READ:
474:   case FILE_MODE_UPDATE:
475:   case FILE_MODE_APPEND_UPDATE:
476:     *flg = PETSC_TRUE;
477:   default:
478:     break;
479:   }
480:   PetscFunctionReturn(PETSC_SUCCESS);
481: }

483: /*@
484:   PetscViewerWritable - Return a flag whether the viewer can be written to with `PetscViewerWrite()`

486:   Not Collective

488:   Input Parameter:
489: . viewer - the `PetscViewer` context

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

494:   Level: intermediate

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

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

507:   PetscFunctionBegin;
509:   PetscAssertPointer(flg, 2);
510:   PetscCall(PetscObjectQueryFunction((PetscObject)viewer, "PetscViewerFileGetMode_C", &f));
511:   *flg = PETSC_TRUE;
512:   if (!f) PetscFunctionReturn(PETSC_SUCCESS);
513:   PetscCall((*f)(viewer, &mode));
514:   if (mode == FILE_MODE_READ) *flg = PETSC_FALSE;
515:   PetscFunctionReturn(PETSC_SUCCESS);
516: }

518: /*@
519:   PetscViewerCheckReadable - Check whether the viewer can be read from, generates an error if not

521:   Collective

523:   Input Parameter:
524: . viewer - the `PetscViewer` context

526:   Level: intermediate

528: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerReadable()`, `PetscViewerCheckWritable()`, `PetscViewerCreate()`, `PetscViewerFileSetMode()`, `PetscViewerFileSetType()`
529: @*/
530: PetscErrorCode PetscViewerCheckReadable(PetscViewer viewer)
531: {
532:   PetscBool flg;

534:   PetscFunctionBegin;
536:   PetscCall(PetscViewerReadable(viewer, &flg));
537:   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)");
538:   PetscFunctionReturn(PETSC_SUCCESS);
539: }

541: /*@
542:   PetscViewerCheckWritable - Check whether the viewer can be written to, generates an error if not

544:   Collective

546:   Input Parameter:
547: . viewer - the `PetscViewer` context

549:   Level: intermediate

551: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerWritable()`, `PetscViewerCheckReadable()`, `PetscViewerCreate()`, `PetscViewerFileSetMode()`, `PetscViewerFileSetType()`
552: @*/
553: PetscErrorCode PetscViewerCheckWritable(PetscViewer viewer)
554: {
555:   PetscBool flg;

557:   PetscFunctionBegin;
559:   PetscCall(PetscViewerWritable(viewer, &flg));
560:   PetscCheck(flg, PetscObjectComm((PetscObject)viewer), PETSC_ERR_SUP, "Viewer doesn't support writing, or is in FILE_MODE_READ mode");
561:   PetscFunctionReturn(PETSC_SUCCESS);
562: }