[petsc-dev] automatic preconditioners for Stokes type problems?

[Matthew Knepley]

On Thu, Aug 5, 2010 at 2:10 AM, Jed Brown <jed at 59a2.org> wrote:

> On Thu, 5 Aug 2010 00:21:13 -0500, Matthew Knepley <knepley at gmail.com>
> wrote:
> > If someone tells us, "I have a Stokes problem", we could search for 0
> > diagonals and create the partition for FS.
>
> I suppose this would work for some common cases, but there are lot of
> discretizations and pressure-dependent constitutive relations/boundary
> conditions that have nonzeros in the pressure block.  I think some slip
> conditions can also produce zero or negative values in the momentum
> block.
>

Do not disagree.


> I'm not convinced that it's so much to ask people to provide an index
> set, considering that FieldSplit is a somewhat advanced thing anyway
> (based on sheer number of choices available, and (typical) sensitivity
> to those choices).


I guess the point here is somewhat like the point of DAs. It is a very
limited
thing, but something many people do. So we provide a way to most easily
do the very limited thing.

Not sure if this is useful enough, but it might be.

   Matt


>
> Jed
>



-- 
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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