[petsc-dev] Seeking Advice on Petsc Preconditioners to Try

[Dave Nystrom]

Jed Brown writes:
 > On Thu, Dec 29, 2011 at 11:15, Dave Nystrom <dnystrom1 at comcast.net> wrote:
 > 
 > > I have tried out -ksp_type cg -pc_type gamg -pc_gamg_type sa on my problem
 > > and am encouraged enough with the results that I would like to try taking
 > > the
 > > next step with using gamg.  Could you provide some advice on how to do
 > > that?
 > > I'm not sure how to provide the null space info you say is important.
 > >
 > 
 > Are you solving a scalar or vector problem?

Both although the most challenging problem right now is one for a Hall matrix
system that is block banded with 2x2 blocks.  Right now, I am just inputting
the matrix into a petsc seqaij matrix.  I guess I need to put it into a petsc
block matrix but have not yet attempted to do that.  I'm not sure how much
work is involved - I need to read the section in the users manual on that.

Anyway, I have 5 scalar systems and on vector system with 2x2 blocks.  I am
interested in applying gamg to all of them to see how well it works.