DMDAVecGetArrayRead#

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

Synopsis#

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

Not Collective

Input Parameters#

da - the DMDA
vec - 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.

The accessible indices are array[zs:zs+zm-1][ys:ys+ym-1][xs:xs+xm-1] where the values are obtained from DMDAGetCorners() for a global vector or DMDAGetGhostCorners() for a local vector.

Fortran Notes#

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 vector or DMDAGetGhostCorners() for a local vector.