[petsc-users] transfer vector data diagonally on DA

[Matthew Knepley]

On Mon, Apr 2, 2012 at 3:36 AM, khalid ashraf <khalid_eee at yahoo.com> wrote:

> 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 would guess (because you provide almost no information about what you are
doing), that
this is a domain on the edge. If you truly mean to have a periodic domain,
you must set that in the
creation call. Then the local vector will also ghost regions outside the
domain boundary.

   Matt


> 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 at mcs.anl.gov>
> *To:* khalid ashraf <khalid_eee at yahoo.com>; PETSc users list <
> petsc-users at 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 at 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].
>
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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