Hi Mark, Matt,
We recently downloaded the petsc development version, to test the gamg package. This works in serial : we tried for small cases. The parallel case (even with 2 partitions) just hangs. As of now, we have not set any parameters. So I guess that the default parameters are being used. Do we need to explicitly set the block size to MatSetBlockSize(mat,1) for a PARALLEL run? Our solver solves U,V,W and P separately. Any input on this would be great. Thanks, Ravi. From: petsc-dev-bounces at mcs.anl.gov [mailto:petsc-dev-boun...@mcs.anl.gov] On Behalf Of Mark F. Adams Sent: Thursday, December 15, 2011 1:18 PM To: For users of the development version of PETSc Subject: Re: [petsc-dev] boomerAmg scalability On Dec 15, 2011, at 1:56 PM, Matthew Knepley wrote: On Thu, Dec 15, 2011 at 10:23 AM, Ravi Kannan <rxk at cfdrc.com> wrote: Dear All, This is Ravi Kannan from CFD Research Corporation. Recently, we are experimenting with the BoomerAMG preconditioner for some "stiff" CFD problems. In that regard, all the other standard solver-preconditioner combinations failed for the current CFD problem. The boomer is the only one which is able to provide with "converged" solutions. We noticed that the scalability of this boomer preconditioner is really poor. For instance, even with a cell size of 2 million, we cannot scale to even 16 partitions (in contrast, the other solver-preconditioner combinations like the BI-CGS/BJacobi gave good enough scalability). Are we missing something? Do we need to use a more latest version of boomer? Have you tried -pc_type gamg in petsc-dev? For gamg you also want to use MPIAIJ matrices and set the block size MatSetBlockSize(mat,3), for a 3D velocity field, for instance. You can also try '-pc_gamg_type pa' or '-pc_gamg_type sa'. "pa", for plain aggregation might be better for CFD problems. Mark Matt Thanks, Ravi. -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-dev/attachments/20120104/14887a5b/attachment.html>