[petsc-dev] Question about MPICH device we use

[Satish Balay]

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
> > 
> > 
>