Dear Bruno, Thanks, that definitely answers my questions. I would have a final slightly related question. Would I see significant performance gain for a GMRES + ILU preconditioning setup by going from AztecOO to the Tpetra or Belos stack? I guess that the best parallel performance increase I could get would be by using the AMG from ML, but I think this will require some experiments before I can set-up the parameters correctly. My system is not elliptic and can be quite ugly at times due to stabilization.
Thank you for everything. On Monday, 4 March 2019 09:03:24 UTC-5, Bruno Turcksin wrote: > > Le lun. 4 mars 2019 à 08:44, Bruno Blais <blais...@gmail.com <javascript:>> > a écrit : > > I'm using the wrapper, so I guess by default that means it is using the > AztecOO stack of solvers? > > Yes, that's right. You won't get any speedup using OpenMP with > AztecOO, you need to switch to the Tpetra stack and Belos to use > OpenMP (but we don't have wrappers for the all Tpetra stack) > > >> 2) Why do you think that OpenMP would be faster than MPI? MPI is > usually faster than OpenMP unless you are very careful about your data > management. > > My original idea was that since in shared memory parallelism you could > precondition a larger chunk of the matrix as a whole, that the ILU > preconditioning would be more efficient in a shared-memory context than in > a distributed one. Thus you would need less GMRES iterations to solve > > your system. It seems I am wrong :) ? > > Using larger blocks for ILU preconditioning will decrease the number > of GMRES iterations but you will spend more time in ILU, so it's hard > to say if it's worth it. > > Best, > > Bruno > -- The deal.II project is located at http://www.dealii.org/ For mailing list/forum options, see https://groups.google.com/d/forum/dealii?hl=en --- You received this message because you are subscribed to the Google Groups "deal.II User Group" group. To unsubscribe from this group and stop receiving emails from it, send an email to dealii+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
