[petsc-dev] DMDA_*PERIODIC and DMDA_XYZGHOSTED

[Jed Brown]

On Tue, Dec 7, 2010 at 22:37, Dmitry Karpeev <karpeev at mcs.anl.gov> wrote:

> I may be out on a limb here, but the column DM could also encapsulate the
> scatter
> that currently sits in the Mat object. By default the row DM could have an
> identity (noop) scatter.
>
> Note that this is very natural from the DD standpoint: ASM/GASM/FieldSplit
> already define scatters that
> scatter to a "subdomain" on which a  matrix/pc operate.  Currently, the
> VecScatter inside the subdomain Mat
> will further scatter the Vec to the "local" part, on which the matrix then
> operates locally.  If the scatter is moved
> out of Mat and into its column DM, than this double scatter can be avoided.
>

Hmm, now the DM is starting to know a lot.  There are times where I think
fusing scatters is good, but this one sounds tricky.  How would you
implement this?
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