I think we should default to ch3:nemesis when --download-mpich, and only do ch3:sock when requested (which we would do in CI).
Satish Balay via petsc-dev <[email protected]> writes: > Primarily because ch3:sock performance does not degrade in oversubscribe mode > - which is developer friendly - i.e on your laptop. > > And folks doing optimized runs should use a properly tuned MPI for their > setup anyway. > > In this case --download-mpich-device=ch3:nemesis is likely appropriate if > using --download-mpich [and not using a separate/optimized MPI] > > Having defaults that satisfy all use cases is not practical. > > Satish > > On Wed, 22 Jul 2020, Matthew Knepley wrote: > >> We default to ch3:sock. Scott MacLachlan just had a long thread on the >> Firedrake list where it ended up that reconfiguring using ch3:nemesis had a >> 2x performance boost on his 16-core proc, and noticeable effect on the 4 >> core speedup. >> >> Why do we default to sock? >> >> Thanks, >> >> Matt >> >>
