DMDAGetElements — PETSc 3.21.4 documentation

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# DMDAGetElements

Gets an array containing the indices (in local indexing) of all the local elements

## Synopsis

    #include "petscdmda.h"
    PetscErrorCode DMDAGetElements(DM dm, PetscInt *nel, PetscInt *nen, const PetscInt *e[])

Not Collective

## Input Parameter

- dm - the `DMDA` object

## Output Parameters

- nel - number of local elements

- 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 (for `DMDA_ELEMENT_Q1`)

- e - the local indices of the elements’ vertices, of length `nel` * `nen`

## Notes

Call `DMDARestoreElements()` once you have finished accessing the elements.

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

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

## Fortran Note

Use

       PetscScalar, pointer :: e(:)

to declare the element array

## See Also

DMDA - Creating vectors for structured grids, `DM`, `DMDA`, `DMDAElementType`, `DMDASetElementType()`, `VecSetValuesLocal()`, `MatSetValuesLocal()`, `DMGlobalToLocalBegin()`, `DMLocalToGlobalBegin()`, `DMDARestoreElements()`, `DMDA_ELEMENT_P1`, `DMDA_ELEMENT_Q1`, `DMDAGetElementsSizes()`, `DMDAGetElementsCorners()`

## Level

intermediate

## Location

src/dm/impls/da/dagetelem.c

## Examples

src/dm/tutorials/ex11f90.F90
src/ksp/ksp/tutorials/ex71.c
src/ksp/ksp/tutorials/ex70.c
src/dm/tutorials/ex5.c

## Implementations

DMDAGetElements_1D() in src/dm/impls/da/dagetelem.c
DMDAGetElements_2D() in src/dm/impls/da/dagetelem.c
DMDAGetElements_3D() in src/dm/impls/da/dagetelem.c

Index of all DMDA routines
Table of Contents for all manual pages
Index of all manual pages