[Beowulf] programming multicore clusters

[Greg Lindahl]

On Fri, Jun 15, 2007 at 01:49:49PM +0200, Toon Knapen wrote:

> AFAICT this is not always the case. E.g. on systems with glibc, this 
> functionality (set_process_affinity and such) is only available starting 
> from libc-2.3.4.

Nearly every statement about Linux is untrue at some point in the
past.

> E.g. you can obtain a big boost when running an 
> MPI-code where each process performs local dgemm's for instance by using 
> an OpenMP'd dgemm implementation. This is an example where running 
> mixed-mode makes a lot of sense.

First off, I see people using *threaded* DGEMM, not OpenMP. Second,
I've never seen anyone show an actual benefit -- can you name an
example? i.e. "for N=foo, I get a 13% speedup on..."

-- greg