[petsc-dev] Problem with SNES and FieldSplit

[Matthew Knepley]

On Tue, Mar 15, 2011 at 6:00 PM, Jed Brown <jed at 59a2.org> wrote:

> On Tue, Mar 15, 2011 at 23:50, Matthew Knepley <knepley at gmail.com> wrote:
>
>> That is not what I have here. I want to change a portion, but outside of
>> that I want it to fall back to a global matrix.
>
>
> You were going to put your MatShell in the "pmat" slot, right? What are you
> going to use for preconditioning the other blocks? If it's the same as in
> "mat", you could use a MatNest for both operators and put the special sauce
> in that slot of the "pmat".
>

This is the same objection Barry has. I do not want this tied to a
particular matrix impl for the global matrix.


> If you assemble the matrix entirely monolithically (using MatSetValues
> globally instead of MatSetValuesLocal on each physics separately), then we
> haven't written MatSetValues_Nest yet so maybe your MatShell is the right
> idea.
>
>
> Related: What do people think about having MatGetSubMatrix() retain
> ownership of the submatrix?
>

Does it matter with our interface? Should be transparent.

   Matt

-- 
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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