Date: 2026-03-31T05:46:06+00:00

Actual source code: dagetelem.c

      1: #include <petsc/private/dmdaimpl.h>

      3: static PetscErrorCode DMDAGetElements_1D(DM dm, PetscInt *nel, PetscInt *nen, const PetscInt *e[])
      4: {
      5:   DM_DA   *da = (DM_DA *)dm->data;
      6:   PetscInt i, xs, xe, Xs, Xe;
      7:   PetscInt cnt = 0;

      9:   PetscFunctionBegin;
     10:   if (!da->e) {
     11:     PetscInt corners[2];

     13:     PetscCheck(da->s, PetscObjectComm((PetscObject)dm), PETSC_ERR_SUP, "Cannot get elements for DMDA with zero stencil width");
     14:     PetscCall(DMDAGetCorners(dm, &xs, NULL, NULL, &xe, NULL, NULL));
     15:     PetscCall(DMDAGetGhostCorners(dm, &Xs, NULL, NULL, &Xe, NULL, NULL));
     16:     xe += xs;
     17:     Xe += Xs;
     18:     if (xs != Xs) xs -= 1;
     19:     da->ne = 1 * (xe - xs - 1);
     20:     PetscCall(PetscMalloc1(1 + 2 * da->ne, &da->e));
     21:     for (i = xs; i < xe - 1; i++) {
     22:       da->e[cnt++] = (i - Xs);
     23:       da->e[cnt++] = (i - Xs + 1);
     24:     }
     25:     da->nen = 2;

     27:     corners[0] = (xs - Xs);
     28:     corners[1] = (xe - 1 - Xs);
     29:     PetscCall(ISCreateGeneral(PETSC_COMM_SELF, 2, corners, PETSC_COPY_VALUES, &da->ecorners));
     30:   }
     31:   *nel = da->ne;
     32:   *nen = da->nen;
     33:   *e   = da->e;
     34:   PetscFunctionReturn(PETSC_SUCCESS);
     35: }

     37: static PetscErrorCode DMDAGetElements_2D(DM dm, PetscInt *nel, PetscInt *nen, const PetscInt *e[])
     38: {
     39:   DM_DA   *da = (DM_DA *)dm->data;
     40:   PetscInt i, xs, xe, Xs, Xe;
     41:   PetscInt j, ys, ye, Ys, Ye;
     42:   PetscInt cnt = 0, cell[4], ns = 2;
     43:   PetscInt c, split[] = {0, 1, 3, 2, 3, 1};

     45:   PetscFunctionBegin;
     46:   if (!da->e) {
     47:     PetscInt corners[4], nn = 0;

     49:     PetscCheck(da->s, PetscObjectComm((PetscObject)dm), PETSC_ERR_SUP, "Cannot get elements for DMDA with zero stencil width");

     51:     switch (da->elementtype) {
     52:     case DMDA_ELEMENT_Q1:
     53:       da->nen = 4;
     54:       break;
     55:     case DMDA_ELEMENT_P1:
     56:       da->nen = 3;
     57:       break;
     58:     default:
     59:       SETERRQ(PetscObjectComm((PetscObject)dm), PETSC_ERR_SUP, "Unknown element type %d", da->elementtype);
     60:     }
     61:     nn = da->nen;

     63:     if (da->elementtype == DMDA_ELEMENT_P1) ns = 2;
     64:     if (da->elementtype == DMDA_ELEMENT_Q1) ns = 1;
     65:     PetscCall(DMDAGetCorners(dm, &xs, &ys, NULL, &xe, &ye, NULL));
     66:     PetscCall(DMDAGetGhostCorners(dm, &Xs, &Ys, NULL, &Xe, &Ye, NULL));
     67:     xe += xs;
     68:     Xe += Xs;
     69:     if (xs != Xs) xs -= 1;
     70:     ye += ys;
     71:     Ye += Ys;
     72:     if (ys != Ys) ys -= 1;
     73:     da->ne = ns * (xe - xs - 1) * (ye - ys - 1);
     74:     PetscCall(PetscMalloc1(1 + nn * da->ne, &da->e));
     75:     for (j = ys; j < ye - 1; j++) {
     76:       for (i = xs; i < xe - 1; i++) {
     77:         cell[0] = (i - Xs) + (j - Ys) * (Xe - Xs);
     78:         cell[1] = (i - Xs + 1) + (j - Ys) * (Xe - Xs);
     79:         cell[2] = (i - Xs + 1) + (j - Ys + 1) * (Xe - Xs);
     80:         cell[3] = (i - Xs) + (j - Ys + 1) * (Xe - Xs);
     81:         if (da->elementtype == DMDA_ELEMENT_P1) {
     82:           for (c = 0; c < ns * nn; c++) da->e[cnt++] = cell[split[c]];
     83:         }
     84:         if (da->elementtype == DMDA_ELEMENT_Q1) {
     85:           for (c = 0; c < ns * nn; c++) da->e[cnt++] = cell[c];
     86:         }
     87:       }
     88:     }

     90:     corners[0] = (xs - Xs) + (ys - Ys) * (Xe - Xs);
     91:     corners[1] = (xe - 1 - Xs) + (ys - Ys) * (Xe - Xs);
     92:     corners[2] = (xs - Xs) + (ye - 1 - Ys) * (Xe - Xs);
     93:     corners[3] = (xe - 1 - Xs) + (ye - 1 - Ys) * (Xe - Xs);
     94:     PetscCall(ISCreateGeneral(PETSC_COMM_SELF, 4, corners, PETSC_COPY_VALUES, &da->ecorners));
     95:   }
     96:   *nel = da->ne;
     97:   *nen = da->nen;
     98:   *e   = da->e;
     99:   PetscFunctionReturn(PETSC_SUCCESS);
    100: }

    102: static PetscErrorCode DMDAGetElements_3D(DM dm, PetscInt *nel, PetscInt *nen, const PetscInt *e[])
    103: {
    104:   DM_DA   *da = (DM_DA *)dm->data;
    105:   PetscInt i, xs, xe, Xs, Xe;
    106:   PetscInt j, ys, ye, Ys, Ye;
    107:   PetscInt k, zs, ze, Zs, Ze;
    108:   PetscInt cnt = 0, cell[8], ns = 6;
    109:   PetscInt c, split[] = {0, 1, 3, 7, 0, 1, 7, 4, 1, 2, 3, 7, 1, 2, 7, 6, 1, 4, 5, 7, 1, 5, 6, 7};

    111:   PetscFunctionBegin;
    112:   if (!da->e) {
    113:     PetscInt corners[8], nn = 0;

    115:     PetscCheck(da->s, PetscObjectComm((PetscObject)dm), PETSC_ERR_SUP, "Cannot get elements for DMDA with zero stencil width");

    117:     switch (da->elementtype) {
    118:     case DMDA_ELEMENT_Q1:
    119:       da->nen = 8;
    120:       break;
    121:     case DMDA_ELEMENT_P1:
    122:       da->nen = 4;
    123:       break;
    124:     default:
    125:       SETERRQ(PetscObjectComm((PetscObject)dm), PETSC_ERR_SUP, "Unknown element type %d", da->elementtype);
    126:     }
    127:     nn = da->nen;

    129:     if (da->elementtype == DMDA_ELEMENT_P1) ns = 6;
    130:     if (da->elementtype == DMDA_ELEMENT_Q1) ns = 1;
    131:     PetscCall(DMDAGetCorners(dm, &xs, &ys, &zs, &xe, &ye, &ze));
    132:     PetscCall(DMDAGetGhostCorners(dm, &Xs, &Ys, &Zs, &Xe, &Ye, &Ze));
    133:     xe += xs;
    134:     Xe += Xs;
    135:     if (xs != Xs) xs -= 1;
    136:     ye += ys;
    137:     Ye += Ys;
    138:     if (ys != Ys) ys -= 1;
    139:     ze += zs;
    140:     Ze += Zs;
    141:     if (zs != Zs) zs -= 1;
    142:     da->ne = ns * (xe - xs - 1) * (ye - ys - 1) * (ze - zs - 1);
    143:     PetscCall(PetscMalloc1(1 + nn * da->ne, &da->e));
    144:     for (k = zs; k < ze - 1; k++) {
    145:       for (j = ys; j < ye - 1; j++) {
    146:         for (i = xs; i < xe - 1; i++) {
    147:           cell[0] = (i - Xs) + (j - Ys) * (Xe - Xs) + (k - Zs) * (Xe - Xs) * (Ye - Ys);
    148:           cell[1] = (i + 1 - Xs) + (j - Ys) * (Xe - Xs) + (k - Zs) * (Xe - Xs) * (Ye - Ys);
    149:           cell[2] = (i + 1 - Xs) + (j + 1 - Ys) * (Xe - Xs) + (k - Zs) * (Xe - Xs) * (Ye - Ys);
    150:           cell[3] = (i - Xs) + (j + 1 - Ys) * (Xe - Xs) + (k - Zs) * (Xe - Xs) * (Ye - Ys);
    151:           cell[4] = (i - Xs) + (j - Ys) * (Xe - Xs) + (k + 1 - Zs) * (Xe - Xs) * (Ye - Ys);
    152:           cell[5] = (i + 1 - Xs) + (j - Ys) * (Xe - Xs) + (k + 1 - Zs) * (Xe - Xs) * (Ye - Ys);
    153:           cell[6] = (i + 1 - Xs) + (j + 1 - Ys) * (Xe - Xs) + (k + 1 - Zs) * (Xe - Xs) * (Ye - Ys);
    154:           cell[7] = (i - Xs) + (j + 1 - Ys) * (Xe - Xs) + (k + 1 - Zs) * (Xe - Xs) * (Ye - Ys);
    155:           if (da->elementtype == DMDA_ELEMENT_P1) {
    156:             for (c = 0; c < ns * nn; c++) da->e[cnt++] = cell[split[c]];
    157:           }
    158:           if (da->elementtype == DMDA_ELEMENT_Q1) {
    159:             for (c = 0; c < ns * nn; c++) da->e[cnt++] = cell[c];
    160:           }
    161:         }
    162:       }
    163:     }

    165:     corners[0] = (xs - Xs) + (ys - Ys) * (Xe - Xs) + (zs - Zs) * (Xe - Xs) * (Ye - Ys);
    166:     corners[1] = (xe - 1 - Xs) + (ys - Ys) * (Xe - Xs) + (zs - Zs) * (Xe - Xs) * (Ye - Ys);
    167:     corners[2] = (xs - Xs) + (ye - 1 - Ys) * (Xe - Xs) + (zs - Zs) * (Xe - Xs) * (Ye - Ys);
    168:     corners[3] = (xe - 1 - Xs) + (ye - 1 - Ys) * (Xe - Xs) + (zs - Zs) * (Xe - Xs) * (Ye - Ys);
    169:     corners[4] = (xs - Xs) + (ys - Ys) * (Xe - Xs) + (ze - 1 - Zs) * (Xe - Xs) * (Ye - Ys);
    170:     corners[5] = (xe - 1 - Xs) + (ys - Ys) * (Xe - Xs) + (ze - 1 - Zs) * (Xe - Xs) * (Ye - Ys);
    171:     corners[6] = (xs - Xs) + (ye - 1 - Ys) * (Xe - Xs) + (ze - 1 - Zs) * (Xe - Xs) * (Ye - Ys);
    172:     corners[7] = (xe - 1 - Xs) + (ye - 1 - Ys) * (Xe - Xs) + (ze - 1 - Zs) * (Xe - Xs) * (Ye - Ys);
    173:     PetscCall(ISCreateGeneral(PETSC_COMM_SELF, 8, corners, PETSC_COPY_VALUES, &da->ecorners));
    174:   }
    175:   *nel = da->ne;
    176:   *nen = da->nen;
    177:   *e   = da->e;
    178:   PetscFunctionReturn(PETSC_SUCCESS);
    179: }

    181: /*@
    182:   DMDAGetElementsCorners - Returns the global (i,j,k) indices of the lower left
    183:   corner of the non-overlapping decomposition of elements identified by `DMDAGetElements()`

    185:   Not Collective

    187:   Input Parameter:
    188: . da - the `DMDA` object

    190:   Output Parameters:
    191: + gx - the i index
    192: . gy - the j index
    193: - gz - the k index

    195:   Level: intermediate

    197: .seealso: [](sec_struct), `DM`, `DMDA`, `DMDAElementType`, `DMDASetElementType()`, `DMDAGetElements()`, `DMDAGetCorners()`, `DMDAGetGhostCorners()`, `DMDAGetElementsSizes()`,
    198:           `DMDAGetElementsCornersIS()`, `DMDARestoreElementsCornersIS()`
    199: @*/
    200: PetscErrorCode DMDAGetElementsCorners(DM da, PeOp PetscInt *gx, PeOp PetscInt *gy, PeOp PetscInt *gz)
    201: {
    202:   PetscInt  xs, Xs;
    203:   PetscInt  ys, Ys;
    204:   PetscInt  zs, Zs;
    205:   PetscBool isda;

    207:   PetscFunctionBegin;
    209:   if (gx) PetscAssertPointer(gx, 2);
    210:   if (gy) PetscAssertPointer(gy, 3);
    211:   if (gz) PetscAssertPointer(gz, 4);
    212:   PetscCall(PetscObjectTypeCompare((PetscObject)da, DMDA, &isda));
    213:   PetscCheck(isda, PetscObjectComm((PetscObject)da), PETSC_ERR_USER, "Not for DM type %s", ((PetscObject)da)->type_name);
    214:   PetscCall(DMDAGetCorners(da, &xs, &ys, &zs, NULL, NULL, NULL));
    215:   PetscCall(DMDAGetGhostCorners(da, &Xs, &Ys, &Zs, NULL, NULL, NULL));
    216:   if (xs != Xs) xs -= 1;
    217:   if (ys != Ys) ys -= 1;
    218:   if (zs != Zs) zs -= 1;
    219:   if (gx) *gx = xs;
    220:   if (gy) *gy = ys;
    221:   if (gz) *gz = zs;
    222:   PetscFunctionReturn(PETSC_SUCCESS);
    223: }

    225: /*@
    226:   DMDAGetElementsSizes - Gets the local number of elements per coordinate direction for the non-overlapping decomposition identified by `DMDAGetElements()`

    228:   Not Collective

    230:   Input Parameter:
    231: . da - the `DMDA` object

    233:   Output Parameters:
    234: + mx - number of local elements in x-direction
    235: . my - number of local elements in y-direction
    236: - mz - number of local elements in z-direction

    238:   Level: intermediate

    240:   Note:
    241:   Returns the same number of elements, irrespective of the `DMDAElementType`

    243: .seealso: [](sec_struct), `DM`, `DMDA`, `DMDAElementType`, `DMDASetElementType()`, `DMDAGetElements()`, `DMDAGetElementsCorners()`
    244: @*/
    245: PetscErrorCode DMDAGetElementsSizes(DM da, PeOp PetscInt *mx, PeOp PetscInt *my, PeOp PetscInt *mz)
    246: {
    247:   PetscInt  xs, xe, Xs;
    248:   PetscInt  ys, ye, Ys;
    249:   PetscInt  zs, ze, Zs;
    250:   PetscInt  dim;
    251:   PetscBool isda;

    253:   PetscFunctionBegin;
    255:   if (mx) PetscAssertPointer(mx, 2);
    256:   if (my) PetscAssertPointer(my, 3);
    257:   if (mz) PetscAssertPointer(mz, 4);
    258:   PetscCall(PetscObjectTypeCompare((PetscObject)da, DMDA, &isda));
    259:   PetscCheck(isda, PetscObjectComm((PetscObject)da), PETSC_ERR_USER, "Not for DM type %s", ((PetscObject)da)->type_name);
    260:   PetscCall(DMDAGetCorners(da, &xs, &ys, &zs, &xe, &ye, &ze));
    261:   PetscCall(DMDAGetGhostCorners(da, &Xs, &Ys, &Zs, NULL, NULL, NULL));
    262:   xe += xs;
    263:   if (xs != Xs) xs -= 1;
    264:   ye += ys;
    265:   if (ys != Ys) ys -= 1;
    266:   ze += zs;
    267:   if (zs != Zs) zs -= 1;
    268:   if (mx) *mx = 0;
    269:   if (my) *my = 0;
    270:   if (mz) *mz = 0;
    271:   PetscCall(DMGetDimension(da, &dim));
    272:   switch (dim) {
    273:   case 3:
    274:     if (mz) *mz = ze - zs - 1; /* fall through */
    275:   case 2:
    276:     if (my) *my = ye - ys - 1; /* fall through */
    277:   case 1:
    278:     if (mx) *mx = xe - xs - 1;
    279:     break;
    280:   }
    281:   PetscFunctionReturn(PETSC_SUCCESS);
    282: }

    284: /*@
    285:   DMDASetElementType - Sets the element type to be returned by `DMDAGetElements()`

    287:   Not Collective

    289:   Input Parameter:
    290: . da - the `DMDA` object

    292:   Output Parameter:
    293: . etype - the element type, currently either `DMDA_ELEMENT_P1` or `DMDA_ELEMENT_Q1`

    295:   Level: intermediate

    297: .seealso: [](sec_struct), `DM`, `DMDA`, `DMDAElementType`, `DMDAGetElementType()`, `DMDAGetElements()`, `DMDARestoreElements()`,
    298:           `DMDA_ELEMENT_P1`, `DMDA_ELEMENT_Q1`
    299: @*/
    300: PetscErrorCode DMDASetElementType(DM da, DMDAElementType etype)
    301: {
    302:   DM_DA    *dd = (DM_DA *)da->data;
    303:   PetscBool isda;

    305:   PetscFunctionBegin;
    308:   PetscCall(PetscObjectTypeCompare((PetscObject)da, DMDA, &isda));
    309:   if (!isda) PetscFunctionReturn(PETSC_SUCCESS);
    310:   if (dd->elementtype != etype) {
    311:     PetscCall(PetscFree(dd->e));
    312:     PetscCall(ISDestroy(&dd->ecorners));

    314:     dd->elementtype = etype;
    315:     dd->ne          = 0;
    316:     dd->nen         = 0;
    317:     dd->e           = NULL;
    318:   }
    319:   PetscFunctionReturn(PETSC_SUCCESS);
    320: }

    322: /*@
    323:   DMDAGetElementType - Gets the element type to be returned by `DMDAGetElements()`

    325:   Not Collective

    327:   Input Parameter:
    328: . da - the `DMDA` object

    330:   Output Parameter:
    331: . etype - the element type, currently either `DMDA_ELEMENT_P1` or `DMDA_ELEMENT_Q1`

    333:   Level: intermediate

    335: .seealso: [](sec_struct), `DM`, `DMDA`, `DMDAElementType`, `DMDASetElementType()`, `DMDAGetElements()`, `DMDARestoreElements()`,
    336:           `DMDA_ELEMENT_P1`, `DMDA_ELEMENT_Q1`
    337: @*/
    338: PetscErrorCode DMDAGetElementType(DM da, DMDAElementType *etype)
    339: {
    340:   DM_DA    *dd = (DM_DA *)da->data;
    341:   PetscBool isda;

    343:   PetscFunctionBegin;
    345:   PetscAssertPointer(etype, 2);
    346:   PetscCall(PetscObjectTypeCompare((PetscObject)da, DMDA, &isda));
    347:   PetscCheck(isda, PetscObjectComm((PetscObject)da), PETSC_ERR_USER, "Not for DM type %s", ((PetscObject)da)->type_name);
    348:   *etype = dd->elementtype;
    349:   PetscFunctionReturn(PETSC_SUCCESS);
    350: }

    352: /*@C
    353:   DMDAGetElements - Gets an array containing the indices (in local indexing)
    354:   of all the local elements

    356:   Not Collective

    358:   Input Parameter:
    359: . dm - the `DMDA` object

    361:   Output Parameters:
    362: + nel - number of local elements
    363: . nen - number of nodes in each element (for example in one dimension it is 2, in two dimensions it is 3 (for `DMDA_ELEMENT_P1`) and 4
    364:         (for `DMDA_ELEMENT_Q1`)
    365: - e   - the local indices of the elements' vertices, of length `nel` * `nen`

    367:   Level: intermediate

    369:   Notes:
    370:   Call `DMDARestoreElements()` once you have finished accessing the elements.

    372:   Each process uniquely owns a subset of the elements. That is no element is owned by two or more processes.

    374:   If on each process you integrate over its owned elements and use `ADD_VALUES` in `Vec`/`MatSetValuesLocal()` then you'll obtain the correct result.

    376:   Fortran Note:
    377:   Use
    378: .vb
    379:    PetscScalar, pointer :: e(:)
    380: .ve
    381:   to declare the element array

    383: .seealso: [](sec_struct), `DM`, `DMDA`, `DMDAElementType`, `DMDASetElementType()`, `VecSetValuesLocal()`, `MatSetValuesLocal()`,
    384:           `DMGlobalToLocalBegin()`, `DMLocalToGlobalBegin()`, `DMDARestoreElements()`, `DMDA_ELEMENT_P1`, `DMDA_ELEMENT_Q1`, `DMDAGetElementsSizes()`,
    385:           `DMDAGetElementsCorners()`
    386: @*/
    387: PetscErrorCode DMDAGetElements(DM dm, PetscInt *nel, PetscInt *nen, const PetscInt *e[])
    388: {
    389:   PetscInt  dim;
    390:   DM_DA    *dd = (DM_DA *)dm->data;
    391:   PetscBool isda;

    393:   PetscFunctionBegin;
    395:   PetscAssertPointer(nel, 2);
    396:   PetscAssertPointer(nen, 3);
    397:   PetscAssertPointer(e, 4);
    398:   PetscCall(PetscObjectTypeCompare((PetscObject)dm, DMDA, &isda));
    399:   PetscCheck(isda, PetscObjectComm((PetscObject)dm), PETSC_ERR_USER, "Not for DM type %s", ((PetscObject)dm)->type_name);
    400:   PetscCheck(dd->stencil_type != DMDA_STENCIL_STAR, PetscObjectComm((PetscObject)dm), PETSC_ERR_SUP, "DMDAGetElements() requires you use a stencil type of DMDA_STENCIL_BOX");
    401:   PetscCall(DMGetDimension(dm, &dim));
    402:   if (dd->e) {
    403:     *nel = dd->ne;
    404:     *nen = dd->nen;
    405:     *e   = dd->e;
    406:     PetscFunctionReturn(PETSC_SUCCESS);
    407:   }
    408:   if (dim == -1) {
    409:     *nel = 0;
    410:     *nen = 0;
    411:     *e   = NULL;
    412:   } else if (dim == 1) {
    413:     PetscCall(DMDAGetElements_1D(dm, nel, nen, e));
    414:   } else if (dim == 2) {
    415:     PetscCall(DMDAGetElements_2D(dm, nel, nen, e));
    416:   } else if (dim == 3) {
    417:     PetscCall(DMDAGetElements_3D(dm, nel, nen, e));
    418:   } else SETERRQ(PETSC_COMM_SELF, PETSC_ERR_ARG_CORRUPT, "DMDA dimension not 1, 2, or 3, it is %" PetscInt_FMT, dim);
    419:   PetscFunctionReturn(PETSC_SUCCESS);
    420: }

    422: /*@
    423:   DMDAGetSubdomainCornersIS - Gets an index set containing the corner indices (in local indexing)
    424:   of the non-overlapping decomposition identified by `DMDAGetElements()`

    426:   Not Collective

    428:   Input Parameter:
    429: . dm - the `DMDA` object

    431:   Output Parameter:
    432: . is - the index set

    434:   Level: intermediate

    436:   Note:
    437:   Call `DMDARestoreSubdomainCornersIS()` once you have finished accessing the index set.

    439: .seealso: [](sec_struct), `DM`, `DMDA`, `DMDAElementType`, `DMDASetElementType()`, `DMDAGetElements()`, `DMDARestoreElementsCornersIS()`,
    440:           `DMDAGetElementsSizes()`, `DMDAGetElementsCorners()`
    441: @*/
    442: PetscErrorCode DMDAGetSubdomainCornersIS(DM dm, IS *is)
    443: {
    444:   DM_DA    *dd = (DM_DA *)dm->data;
    445:   PetscBool isda;

    447:   PetscFunctionBegin;
    449:   PetscAssertPointer(is, 2);
    450:   PetscCall(PetscObjectTypeCompare((PetscObject)dm, DMDA, &isda));
    451:   PetscCheck(isda, PetscObjectComm((PetscObject)dm), PETSC_ERR_USER, "Not for DM type %s", ((PetscObject)dm)->type_name);
    452:   PetscCheck(dd->stencil_type != DMDA_STENCIL_STAR, PetscObjectComm((PetscObject)dm), PETSC_ERR_SUP, "DMDAGetElement() requires you use a stencil type of DMDA_STENCIL_BOX");
    453:   if (!dd->ecorners) { /* compute elements if not yet done */
    454:     const PetscInt *e;
    455:     PetscInt        nel, nen;

    457:     PetscCall(DMDAGetElements(dm, &nel, &nen, &e));
    458:     PetscCall(DMDARestoreElements(dm, &nel, &nen, &e));
    459:   }
    460:   *is = dd->ecorners;
    461:   PetscFunctionReturn(PETSC_SUCCESS);
    462: }

    464: /*@C
    465:   DMDARestoreElements - Restores the array obtained with `DMDAGetElements()`

    467:   Not Collective

    469:   Input Parameters:
    470: + dm  - the `DM` object
    471: . nel - number of local elements
    472: . nen - number of nodes in each element
    473: - e   - the local indices of the elements' vertices

    475:   Level: intermediate

    477:   Note:
    478:   This restore signals the `DMDA` object that you no longer need access to the array information.

    480: .seealso: [](sec_struct), `DM`, `DMDA`, `DMDAElementType`, `DMDASetElementType()`, `DMDAGetElements()`
    481: @*/
    482: PetscErrorCode DMDARestoreElements(DM dm, PetscInt *nel, PetscInt *nen, const PetscInt *e[])
    483: {
    484:   PetscFunctionBegin;
    486:   PetscAssertPointer(nel, 2);
    487:   PetscAssertPointer(nen, 3);
    488:   PetscAssertPointer(e, 4);
    489:   if (nel) *nel = 0;
    490:   if (nen) *nen = -1;
    491:   if (e) *e = NULL;
    492:   PetscFunctionReturn(PETSC_SUCCESS);
    493: }

    495: /*@
    496:   DMDARestoreSubdomainCornersIS - Restores the `IS` obtained with `DMDAGetSubdomainCornersIS()`

    498:   Not Collective

    500:   Input Parameters:
    501: + dm - the `DM` object
    502: - is - the index set

    504:   Level: intermediate

    506: .seealso: [](sec_struct), `DM`, `DMDA`, `DMDAElementType`, `DMDASetElementType()`, `DMDAGetSubdomainCornersIS()`
    507: @*/
    508: PetscErrorCode DMDARestoreSubdomainCornersIS(DM dm, IS *is)
    509: {
    510:   PetscFunctionBegin;
    513:   *is = NULL;
    514:   PetscFunctionReturn(PETSC_SUCCESS);
    515: }