[petsc-users] Scatter context for MatMult

[Jed Brown]

On Fri, Aug 17, 2012 at 1:05 PM, John Fettig <john.fettig at gmail.com> wrote:

> Is this the role of MatGetGhosts?
>

That's the intent, but it looks like this function was only implemented for
MPIBAIJ.

The actual implementation of MatMult_MPI*AIJ is to start the scatter, apply
the diagonal block, finish the scatter, and apply the off-diagonal part.

Why do you want raw access?

If you really need, you can either use MatMPIAIJGetSeqAIJ() or just include
the private header.


>
> John
>
> On Fri, Aug 17, 2012 at 2:01 PM, John Fettig <john.fettig at gmail.com>
> wrote:
> > Is there a scatter context available someplace that would allow me to
> > gather all of the elements of a vector that correspond to the ones
> > needed for a MatMult (MPIAIJ matrices)?  When you do a MatMult, I
> > presume it first scatters/gathers the ghost elements of the vector
> > being multiplied, can I use this scatter for a vectors outside of the
> > MatMult?
> >
> > Thanks,
> > John
>
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