[petsc-users] DIVERGED_INDEFINITE_PC in algebraic multigrid

[Mark Adams]

If the solver is degrading as the coefficients change, and I would assume
get more nasty, you can try deleting the solver at each time step.  This
will be about 2x more expensive, because it does the setup each solve, but
it might fix your problem.

You also might try:

-pc_type hypre
-pc_hypre_type boomeramg




On Mon, May 19, 2014 at 6:49 PM, Jed Brown <jed at jedbrown.org> wrote:

> Michele Rosso <mrosso at uci.edu> writes:
>
> > Jed,
> >
> > thank you very much!
> > I will try with ///-mg_levels_ksp_type chebyshev -mg_levels_pc_type
> > sor/   and report back.
> > Yes, I removed the nullspace from both the system matrix and the rhs.
> > Is there a way to have something similar to Dendy's multigrid or the
> > deflated conjugate gradient method with PETSc?
>
> Dendy's MG needs geometry.  The algorithm to produce the interpolation
> operators is not terribly complicated so it could be done, though DMDA
> support for cell-centered is a somewhat awkward.  "Deflated CG" can mean
> lots of things so you'll have to be more precise.  (Most everything in
> the "deflation" world has a clear analogue in the MG world, but the
> deflation community doesn't have a precise language to talk about their
> methods so you always have to read the paper carefully to find out if
> it's completely standard or if there is something new.)
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20140522/1460cf95/attachment.html>