[petsc-users] Insert values into matrix using MatSetValuesStencil or MatSetValuesLocal

Matthew Knepley knepley at gmail.com
Mon Aug 24 05:21:21 CDT 2015

On Mon, Aug 24, 2015 at 4:09 AM, Wee-Beng Tay <zonexo at gmail.com> wrote:

> Hi,
> I'm modifying my 3d fortran code from MPI along 1 direction (z) to MPI
> along 2 directions (y,z)
> Previously I was using MatSetValues with global indices. However, now I'm
> using DM and global indices is much more difficult.
> I come across MatSetValuesStencil or MatSetValuesLocal.
> So what's the difference bet the one since they both seem to work locally?

No. MatSetValuesLocal() takes local indices. MatSetValuesStencil() takes
global vertex numbers.

> Which is a simpler/better option?


> Is there an example in Fortran for MatSetValuesStencil?

Timothée Nicolas shows one in his reply.

Do I also need to use DMDAGetAO together with MatSetValuesStencil or
> MatSetValuesLocal?




> Thanks!

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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