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?
Not sure. Scott I think was running his new MHD stuff. His post is on the #general channel on the Firedrake slack.
Thanks,
Matt
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
> >
> >
>
--
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