[petsc-dev] DMGetMatrix --> DMGetMatrices?

[Jed Brown]

On Fri, Feb 10, 2012 at 16:56, Barry Smith <bsmith at mcs.anl.gov> wrote:

> I realize that since the DMs may often share "the grid information" and
> only be different in the stencil width or box type or something Jed (or
> maybe it is Matt) is going to get all upset that their are two DMs with
> common information sometimes. My response is "get over it"   :-).


Lots of objects share PetscLayouts, ISLocalToGlobalMappings, etc., without
forcing this sharing on users (or, in most cases, even exposing the
existence of these shared objects to the user). I think DM should work the
same way.

In this case, we are interpreting Vecs as being part of both spaces. I'm
less keen on that, but it's not a deal breaker.

What about DMDAFormJacobianLocal()? Should it have both matrices? How does
the user manage the two DMs if they want to assemble both matrices in the
same mesh traversal?
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