Okay, thank you for the guidance. Jim
On Mon, Aug 12, 2013 at 1:38 PM, Karl Rupp <[email protected]> wrote: > Hi Jim, > > in addition to what Matt already said, keep in mind is that you usually > won't see a two-fold performance gain in iterative solvers anyway, as the > various integers used for storing the nonzeros in the sparse matrix don't > change their size. I once played with an implementation of an > non-preconditioned mixed-precision CG solver, and I only obtained about a > 40 percent overall performance gain for well-conditioned systems. For less > well-conditioned systems you may not get any better overall performance at > all (or worse, fail to converge). > > Best regards, > Karli > > > > On 08/12/2013 12:32 PM, Matthew Knepley wrote: > >> On Mon, Aug 12, 2013 at 12:24 PM, Jim Fonseca <[email protected] >> <mailto:[email protected]>> wrote: >> >> Hi, >> We are curious about the mixed-precision capabilities in NEMO5. I >> see that there is a newish configure option to allow single >> precision for linear solve. Other than that, I found this old post: >> https://lists.mcs.anl.gov/**mailman/htdig/petsc-users/** >> 2012-August/014842.html<https://lists.mcs.anl.gov/mailman/htdig/petsc-users/2012-August/014842.html> >> >> Is there any other information about to see if we can take advantage >> of this capability? >> >> >> Mixed-precision is hard, and especially hard in PETSc because the C type >> system is limited. >> However, it also needs to be embedded in an algorithm that can take >> advantage of it. I would >> always start out with a clear motivation: >> >> - What would mixed precision accomplish in your code? >> >> - What is the most possible benefit you would see? >> >> and decide if that is worth a large time investment. >> >> Thanks, >> Jim >> >> -- >> Jim Fonseca, PhD >> Research Scientist >> Network for Computational Nanotechnology >> Purdue University >> 765-496-6495 <tel:765-496-6495> >> www.jimfonseca.com <http://www.jimfonseca.com> >> >> >> >> >> >> >> -- >> 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 >> > > -- Jim Fonseca, PhD Research Scientist Network for Computational Nanotechnology Purdue University 765-496-6495 www.jimfonseca.com
