[petsc-dev] PETSc MG Solvers vs agmg

[Dave Nystrom]

I have a 2d resistive mhd code that has an interface to both agmg and various
multigrid solvers available from PETSc including gamg, hypre and ml.  I'm not
that familiar with multigrid and so it is difficult for me to know how to
experiment with the various mg packages and tune them to my particular
problems.  In my code, agmg is a stand alone solver.  I have a couple of
questions.

1.  Is it possible to use the PETSc mg solvers effectively without an
iterative method by choosing preonly as the iterative method - like I do for
the PETSc direct solves?

2.  Is anyone on this list sufficiently familiar with agmg and the other
PETSc mg solvers to know how to configure the PETSc mg solvers to work more
like agmg?  It seems that agmg gives better performance than the PETSc mg
solvers but I also have issues with agmg including fragility.

Thanks,

Dave