[Beowulf] Shared memory

[Kozin, I (Igor)]

> 
> But back to the original question: instead of using OpenMP and MPI at 
> once (which I see in the same way as Mark), I'd suggest to 
> compile MPICH 
> with shared memory support and setup the machinefile 
> accordingly. Then 
> you can easy look for any speed improvement using shared memory.
> 
> CU - Reuti

I think MPI/OpenMP has its niche. Choosing OpenMP or MPI or 
mixed MPI/OpenMP is also about a choice of appropriate/most suitable 
algorithm as well. However I must agree that pure MPI seems 
most suitable if the target architecture is Opteron.

BTW, "taskset" worked fine with MPI but could not get a grip on OpenMP
threads on a dual core. 

It is straightforward to make STREAM a mixed OpenMP/MPI code
from an MPI source and use it as a test. On the other
hand the conclusion of
http://www-fp.mcs.anl.gov/petsc-fun3d/Talks/pcfd00.pdf
is that mixed MPI/OpenMP model performs well if the job
is not memory bandwidth bounded (however this presentation
seems to be a bit dated.)
Unfortunately I can't recommend a simple established code or benchmark 
which would allow transparent comparison of MPI versus OpenMP/MPI.

Best,
Igor