Mark F. Adams writes: > On Dec 29, 2011, at 12:51 PM, Dave Nystrom wrote: > > > 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. > > Thats fine, actually require. Just call this: > > ierr = MatSetBlockSize(Amat,3); CHKERRQ(ierr);
Shouldn't it be ierr = MatSetBlockSize(Amat,2); CHKERRQ(ierr); since I have 2x2 blocks. > > 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. > > > >
