[petsc-users] DMDA questions

[Xiangdong]

On Tue, Feb 25, 2014 at 4:12 PM, Jed Brown <jed at jedbrown.org> wrote:

> Xiangdong <epscodes at gmail.com> writes:
>
> > For the MatSetValuesStencil, should it always work in pair with
> > DMCreateMatrix?
>
> Yes, or MatSetStencil.
>
> > However, in some example, e.g., src/ksp/ksp/examples/tutorials/ex25.c,
> the
> > DMCreateMatrix is never called. Is it because KspSetComputeOperators is
> > used and DMCreateMatrix is called implicitly somewhere?
>
> No, it is just testing that certain functionality works even if the DM
> is not set.  If you have a DM, we recommend setting it.
>

I am not clear about this. In this example, where is the format declaration
(e.g.,mpiaij) of Mat jac? Why is this mat jac always distributed in
a compatible way as the DM vectors?

Thanks.

Xiangdong
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