FieldSplit Schur preconditioner

[Matthew Knepley]

On Sat, Sep 6, 2008 at 10:57 AM, Kees, Christopher E
<Christopher.E.Kees at usace.army.mil> wrote:
> Hi,
>
> I'm interested in these types of Shur complement preconditioners as well. I
> had stopped working with petsc-dev some time back because I wasn't using new
> functionality. Would this be a good time to start working with petsc-dev in
> order to start testing these? I'm primarily interested in stokes and
> navier-stokes type systems but also have some other coupled systems that an
> "operator-split" preconditioner should work well on.

Yes. We have introduced a whole new set of tools that work by mapping each field
to an IS, like PCFieldSplit.

> With regard to testing, I am also looking for a solid parallel direct solver
> to verify everything from the nonlinear solver up. I have been using superlu
> in serial and superlu_dist in parallel (through PETSc) but have noticed some
> reduction in accuracy as I go to more processors with superlu_dist. This may
> just be a bug in our code, but I thought if I get petsc-dev the new approach
> to external direct solvers that Barry mentioned earlier might make it easier
> to look at some other direct solvers. Several years ago I got better results
> with spooles, but I'd be interested in any current recommendations.

You can also try MUMPS with --download-mumps.

   Matt

> Thanks,
> Chris
-- 
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