[petsc-dev] PETSc MG Solvers vs agmg

[Dave Nystrom]

Barry Smith writes:
 > On May 1, 2012, at 7:22 PM, Dave Nystrom wrote:
 > > 
 > >>> 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.
 > >> 
 > >> Please send a link for information on agmg; I've never heard of that.
 > > 
 > > http://homepages.ulb.ac.be/~ynotay/AGMG
 > 
 > Ok, this general approach is what the Trilinos ML solver users (which is a
 > fairly good) and what Mark Adams is adding to PETSc in PCGAMG.

Thanks for this info.

 > You can start by ./configure PETSc with --download-ml and then run the
 > program with -pc_type mg

I assume you mean "-pc_type ml".  I have actually configured and run
petsc-dev with gamg, ml and hypre-boomeramg.  I have just used the default
parameters because I am not sure which of the parameters would be most useful
to try and tune.  It has seemed that ML has given the best results so far but
those results in terms of run time performance are not as good as agmg.

I'd like to somehow get educated on how to intelligently tune the adjustable
parameters on these various MG packages and ML seems a good place to start.
But I'm not quite sure how to get started since there are enough adjustable
parameters that exploring parameter space could be challenge.

Perhaps there is some good documentation on this.  I guess I should google
"Trilinos ML documentation" and see what I find.  My solves are on a 2d
structured mesh and I have 8 of them of various flavors.

 > You can run with -ksp_view to see the number of levels etc it ended up
 > with and
 > http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/PC/PCML.html
 > for some options.

Thanks again.

Dave

 > Barry
 > 
 > > 
 > >> Barry
 > >> 
 > >>> 
 > >>> Thanks,
 > >>> 
 > >>> Dave
 >