On Thu, Jul 5, 2018 at 2:04 PM Mark Adams <[email protected]> wrote: > > > On Thu, Jul 5, 2018 at 12:41 PM Tobin Isaac <[email protected]> wrote: > >> On Thu, Jul 05, 2018 at 09:28:16AM -0400, Mark Adams wrote: >> > > >> > > >> > > Please share the results of your experiments that prove OpenMP does >> not >> > > improve performance for Mark’s users. >> > > >> > >> > This obviously does not "prove" anything but my users use OpenMP >> primarily >> > because they do not distribute their mesh metadata. They can not >> replicated >> > the mesh on every core, on large scale problems and shared memory allows >> > them to survive. They have decided to use threads as opposed to MPI >> shared >> > memory. (Not a big deal, once you decide not to use distributed memory >> the >> > damage is done and NERSC seems to be OMP centric so they can probably >> get >> > better support for OMP than MPI shared memory.) >> >> Out of curiosity, is the mesh immutable for a full simulation or adaptive? >> If it's immutable, that seems like a poster child for the "private by >> default, shared by choice" paradigm. >> > > This is Chombo so it is dynamic. >
We need more competitors like this :) We need to give more talks advocating serial meshes, unstable algorithms, OpenMP, and templates. Matt > > >> > BTW, PETSc does support OMP, that is what I have been working on testing >> > for the last few weeks. First with Hypre (numerics are screwed up from >> an >> > apparent compiler bug or a race condition of some sort; it fails at >> higher >> > levels of optimization), and second with MKL kernels. The numerics are >> > working with MKL and we are working on packaging this up to deliver to a >> > user (they will test performance). >> > -- 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 https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
