On Jan 5, 2012, at 6:12 PM, Ravi Kannan wrote: > Hi Mark, > > > From: petsc-dev-bounces at mcs.anl.gov [mailto:petsc-dev-bounces at > mcs.anl.gov] On Behalf Of Mark F. Adams > Sent: Wednesday, January 04, 2012 12:09 PM > To: For users of the development version of PETSc > Subject: Re: [petsc-dev] boomerAmg scalability > > Is your problem unsymmetric? I don't think this is the problem, it was fixed > recently. > > If not, can you run with -pc_gamg_verbose and -info and send me the output? > I have attached the verbose+info outputs for both the serial and the parallel > (2 partitions). NOTE: the serial output at some location says PC=Jacobi! Is > it implicitly converting the PC to a Jacobi?
That is an error in the print out. Mark > > You don't need to set the block size if it is 1. > > I have a feeling it has to do with not setting the buffer sizes correctly. > There are some heuristics in there and this needs to be improved. What kind > of discretization are you using? What order, how many non-zeros per row? > Maybe try the smallest case that you have with more processors. I have a > feeling it is trashing around mallocing stuff in MatSetValues so it just > "looks" hung. > > Mark > > Thanks, > Ravi. > > On Jan 4, 2012, at 12:14 PM, Ravi Kannan wrote: > > > 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-bounces at > 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/20120105/07efba5c/attachment.html>
