[mpich-discuss] Support for MIC in MPICH 3.0.4

[Jeff Hammond]

> Unfortunately the MPI application I'm trying to run would require too much effort to convert to hybrid OpenMP/MPI to be viable option at this point.

Does your code actually scale to 240 MPI ranks per card?  What is the
performance relative to peak or a fully-populated MPI-only run on e.g
SNB?

You're going to have to convert to MPI+Threads eventually so you might
as well start now.  It is completely unreasonable to expect that
MPI-only is reasonable usage on a 60-core chip with a ring
interconnect.

I am so convinced of the impossibility that MPI_Allreduce scales to
>100 MPI procs in shared memory that I will learn Ada as punishment if
I'm wrong.

If you don't like OpenMP, you could consider Pthreads or TBB instead,
but something tells me that if you're unwilling to use OpenMP, it's
because you have an F77  code with common blocks that cannot be made
thread-safe for all the beer in Australia.

Jeff

-- 
Jeff Hammond
jeff.science at gmail.com