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:   if (!*vf) PetscFunctionReturn(PETSC_SUCCESS);
161:   PetscCall(PetscViewerDestroy(&(*vf)->viewer));
162:   if ((*vf)->data_destroy) PetscCall((*vf)->data_destroy(&(*vf)->data));
163:   PetscCall(PetscFree(*vf));
164:   PetscFunctionReturn(PETSC_SUCCESS);
165: }

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

170:   Not Collective

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

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

178:   Level: intermediate

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

183: .seealso: [](sec_viewers), `PetscViewerType`, `PetscViewer`, `PetscViewerCreate()`, `PetscViewerSetType()`
184: @*/
185: PetscErrorCode PetscViewerGetType(PetscViewer viewer, PetscViewerType *type)
186: {
187:   PetscFunctionBegin;
189:   PetscAssertPointer(type, 2);
190:   *type = ((PetscObject)viewer)->type_name;
191:   PetscFunctionReturn(PETSC_SUCCESS);
192: }

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

198:   Logically Collective

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

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

208:   Level: advanced

210: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerSetFromOptions()`, `PetscViewerAppendOptionsPrefix()`
211: @*/
212: PetscErrorCode PetscViewerSetOptionsPrefix(PetscViewer viewer, const char prefix[])
213: {
214:   PetscFunctionBegin;
216:   PetscCall(PetscObjectSetOptionsPrefix((PetscObject)viewer, prefix));
217:   PetscFunctionReturn(PETSC_SUCCESS);
218: }

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

224:   Logically Collective

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

230:   Level: advanced

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

236: .seealso: [](sec_viewers), `PetscViewer`, `PetscViewerGetOptionsPrefix()`, `PetscViewerSetOptionsPrefix()`
237: @*/
238: PetscErrorCode PetscViewerAppendOptionsPrefix(PetscViewer viewer, const char prefix[])
239: {
240:   PetscFunctionBegin;
242:   PetscCall(PetscObjectAppendOptionsPrefix((PetscObject)viewer, prefix));
243:   PetscFunctionReturn(PETSC_SUCCESS);
244: }

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

250:   Not Collective

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

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

258:   Level: advanced

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

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

273:   Collective

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

278:   Level: advanced

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

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

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

299:   Collective

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

306:   Level: intermediate

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

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

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

324:   Collective

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

330:   Level: beginner

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

343:   PetscFunctionBegin;
346:   if (!viewer) PetscCall(PetscViewerASCIIGetStdout(PetscObjectComm((PetscObject)v), &viewer));
348:   PetscCheckSameComm(v, 1, viewer, 2);

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

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

377:   Collective

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

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

388:   Level: beginner

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

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

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

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

442:   Not Collective

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

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

450:   Level: intermediate

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

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

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

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

485:   Not Collective

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

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

493:   Level: intermediate

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

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

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

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

520:   Collective

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

525:   Level: intermediate

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

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

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

543:   Collective

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

548:   Level: intermediate

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

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