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

[Jed Brown]

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.

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).

Jed