On Dec 29, 2011, at 8:24 PM, Dave Nystrom wrote: > 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.
yes > >>> 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. >>> >> >> >