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.