Hello all, I am solving a Poisson equation with Neumann BC on a structured grid (arising from an incompressible Navier-Stokes problem). Although my mesh is structured, the matrix is 'given' so I am using AMG instead of geometric multigrid, for the moment. To solve the Poisson equation I use CG with preconditioning provided by BoomerAMG, using standard options. I have run my problem for different grid sizes and number of processors, but I am confused regarding the parallel scalability. Attached are some timing results that give the average time spent on solving the Poisson equation. As you can see, when going from 1 to 2 processors, the scaling is very good, even for the case of 200^3 grid points (8 million). For larger number of processors this quickly deteriorates. The cluster I am running on has 8 cores per node and 24GB memory per node. Can someone comment on these results? Is this what I should expect?
Some additional information: - I set the NullSpace of the matrix explicitly with MatNullSpaceCreate - The set-up of the problem is not included in the timing results. The set-up is not efficient yet (use of MatRow, for example), and there is some code cleanup to do (too many matrices and vectors), but I think this should not affect the performance of the Poisson solve. - log_summary and ksp_monitor are attached. Thanks a lot, Benjamin -------------- next part -------------- A non-text attachment was scrubbed... Name: log_summary Type: application/octet-stream Size: 10868 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120710/e71412c0/attachment-0003.obj> -------------- next part -------------- -------------- next part -------------- A non-text attachment was scrubbed... Name: timing Type: application/octet-stream Size: 170 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120710/e71412c0/attachment-0004.obj> -------------- next part -------------- -------------- next part -------------- A non-text attachment was scrubbed... Name: ksp_view Type: application/octet-stream Size: 1777 bytes Desc: not available URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120710/e71412c0/attachment-0005.obj> -------------- next part -------------- -- Ir. B. Sanderse Centrum Wiskunde en Informatica Science Park 123 1098 XG Amsterdam t: +31 20 592 4161 e: sanderse at cwi.nl
