BTW: Last we compared performance [many years ago] the difference was not a factor of 2 - but a few percentage points.
Which petsc example can we re-run to compare? Satish On Wed, 22 Jul 2020, Satish Balay via petsc-dev wrote: > 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 > > > > >
