Just a quick reply until I get back to a computer on Monday... The answer to #2 is YES... We use Hypre with BoomerAMG to precondition our matrix free solves all the time. Just build petsc with Hypre support and pass the following on the command-line for your app:
-snes_mf_operator -pc_type hypre -pc_hypre_type boomeramg This will use AMG on whatever you put into the jacobian matrix and use the result to precondition your matrix free solve. Derek Sent from my iPhone On Nov 7, 2008, at 8:50 AM, "Vijay S. Mahadevan" <[EMAIL PROTECTED]> wrote: > Hi there, > > Before I even start, I know this is probably going to be a loaded > question, but nevertheless, any help would be appreciated. > > Background: I'm working on solution to large scale PDE systems based > on libmesh for discretization and petsc for solution procedures. My > physics objects are derived from EquationSystems in libmesh > datastructure and can contain one or more implicitsystems in it. I use > the Jacobian-Free Krylov scheme for my nonlinear solve and hence the > efficiency of the method is achieved from good preconditioning. I've > tried using ILU to precondition my preconditioner (linearized version) > of the original nonlinear system and this works well for serial runs. > But this does not scale when I run in parallel. > > So my questions are > > 1) Is it is possible to use libmesh objects to perform geometric > multigrid preconditioning and completely avoid the matrix creation > except in the coarsest case ?! I've seen some of Ben's presentation > that mentions using multigrid for stokes problems etc. and so am > curious as to what this would entail ... For example, would I have to > create multiple equationsystems object since the mesh is not > associated with just the system. Hence for every multi-grid level, I > would have a new instance of the physics system but on a coarser mesh > level. Is this how you would possibly implement this ?! > 2) If I can afford to create the matrix in the finest level, can we > use algebraic multigrid procedures to precondition this system in > parallel ? Anyone know how this scales ? > 3) Also, I was reading about Prometheus > (http://www.columbia.edu/~ma2325/prom_intro.html) and it looks > promising as both a black-box solver and preconditioner when the > matrix is available and geometric multigrid in 2D (not sure about 3D). > Has anyone in this list used this package with Petsc and/or libMesh ?! > > Again, like I said before, there is a lot of things here you can > comment on. Feel free to write your thoughts because I want to get as > much input as possible before choosing anything specific. > > Thanks, > Vijay > > --- > ---------------------------------------------------------------------- > This SF.Net email is sponsored by the Moblin Your Move Developer's > challenge > Build the coolest Linux based applications with Moblin SDK & win > great prizes > Grand prize is a trip for two to an Open Source event anywhere in > the world > http://moblin-contest.org/redirect.php?banner_id=100&url=/ > _______________________________________________ > Libmesh-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/libmesh-users ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
