petsc-3.14.5 2021-03-03
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# DMDAVecGetArrayRead

Returns a multiple dimension array that shares data with the underlying vector and is indexed using the global dimensions.

### Synopsis

    #include "petscdmda.h"
    PetscErrorCode  DMDAVecGetArrayRead(DM da,Vec vec,void *array)

Not collective

### Input Parameter

| da | - the distributed array
| vec | - the vector, either a vector the same size as one obtained with DMCreateGlobalVector() or DMCreateLocalVector()

### Output Parameter

| array | - the array

### Notes

Call DMDAVecRestoreArrayRead() once you have finished accessing the vector entries.

In C, the indexing is "backwards" from what expects: array[k][j][i] NOT array[i][j][k]!

If vec is a local vector (obtained with DMCreateLocalVector() etc) then the ghost point locations are accessible. If it is a global vector then the ghost points are not accessible. Of course with the local vector you will have had to do the

appropriate DMGlobalToLocalBegin() and DMGlobalToLocalEnd() to have correct values in the ghost locations.

### Fortran Notes

From Fortran use DMDAVecGetArrayReadF90() and pass for the array type PetscScalar,pointer :: array(:,...,:) of the appropriate dimension. For a DMDA created with a dof of 1 use the dimension of the DMDA, for a DMDA created with a dof greater than 1 use one more than the dimension of the DMDA. The order of the indices is array(xs:xs+xm-1,ys:ys+ym-1,zs:zs+zm-1) (when dof is 1) otherwise array(0:dof-1,xs:xs+xm-1,ys:ys+ym-1,zs:zs+zm-1) where the values are obtained from DMDAGetCorners() for a global array or DMDAGetGhostCorners() for a local array. Include petsc/finclude/petscdmda.h90 to access this routine.

Due to bugs in the compiler DMDAVecGetArrayReadF90() does not work with gfortran versions before 4.5

### See Also

DMDAGetGhostCorners(), DMDAGetCorners(), VecGetArray(), VecRestoreArray(), DMDAVecRestoreArrayRead(), DMDAVecRestoreArrayDOF()
DMDAVecGetArrayDOF(), DMDAVecGetArray(), DMDAVecRestoreArray(), DMDAVecGetArrayRead(), DMDAVecRestoreArrayRead(), DMStagVecGetArrayRead()

### Level

intermediate

### Location

src/dm/impls/da/dagetarray.c

### Examples

src/dm/tutorials/ex3.c.html
src/ksp/ksp/tutorials/ex43.c.html
src/snes/tutorials/ex3.c.html
src/snes/tutorials/ex14.c.html
src/snes/tutorials/ex15.c.html
src/snes/tutorials/ex19.c.html
src/snes/tutorials/ex78.c.html
src/ts/tutorials/ex7.c.html
src/ts/tutorials/ex9.c.html
src/ts/tutorials/ex10.c.html
src/ts/tutorials/ex13.c.html
Index of all DMDA routines
Table of Contents for all manual pages
Index of all manual pages