Hi Jed,

I am using petsc/3.1 and the include file "petscdmda.h" is not working. I am using the "petscda.h"

and DACreate3D.

unew_localptr[][][] is from a global vector using VecGetArray

u_localptr[][][] is from a local vector communicated from a global vector.

I tried

unew_localptr[k][j][i]=u_localptr[k-1][j-1][i-1]

but it gives Segmentation Violation error.

I also tried unew_localptr[k][j][i]=u_localptr[k][j+1][i+1] which works but

unew_localptr[k][j][i]=u_localptr[k+1][j+1][i+1] or unew_localptr[k][j][i]=u_localptr[k][j-1][i-1]

does not work. I am running the program on4 processors.

Thanks.

ierr = DACreate3d(PETSC_COMM_WORLD,DA_YPERIODIC,DA_STENCIL_BOX,appctx.l,appctx.m,appctx.n,

PETSC_DECIDE,PETSC_DECIDE,PETSC_DECIDE,1,1,PETSC_NULL,PETSC_NULL,PETSC_NULL,

&appctx.da);CHKERRQ(ierr);

for (k=zs; k<zs+zm; k++) {

for (j=ys; j<ys+ym; j++) {

for (i=xs; i<xs+xm; i++) {

if(i!=0 || j!=0 || k!=0|| i!=mx-1 || j!=my-1 || k!=mz-1)

unew_localptr[k][j][i]=u_localptr[k+1][j+1][i+1];

}}}

From: Jed Brown <jedbrown@mcs.anl.gov>
To: khalid ashraf <khalid_eee@yahoo.com>; PETSc users list <petsc-users@mcs.anl.gov>
Sent: Sunday, April 1, 2012 10:07 PM
Subject: Re: [petsc-users] transfer vector data diagonally on DA

On Sun, Apr 1, 2012 at 22:01, khalid ashraf <khalid_eee@yahoo.com> wrote:

I want to transfer vector data diagonally in the DA grid like
for (k=zs; k<zs+zm; k++) {
for (j=ys; j<ys+ym; j++) {
for (i=xs; i<xs+xm; i++) {
if(i!=mx-1 || j!=my-1 || k!=mz-1){

u_new[k+1][j+1][i+1]=u[k][j][i];}
}}}

Could you please suggest the best way to do it minimizing interprocessor assignments.

Both are on the same DMDA?

Communicate U to Ulocal (DMGlobalToLocalBegin/End) using a BOX stencil with width at least 1, get the global array u_new[][][] from UGlobalNew and the local arrays u[][][] from Ulocal, then assign u_new[k][j][i] = u[k-1][j-1][i-1].