On 4 May 2010, at 15:27, Jeff Squyres wrote:
> One thing to be careful with a run-time check is that you might not want *all* processes on a box to try to alloc a sysv segment, fork a child, try to connect, ...etc. With large count boxen, you might run out of sysv shmem segments if all procs try the test and/or run into OS serialization issues (someone here at the Forum cited a 96 core box). So you might want to have local rank 0 (or the orted? ...but that wouldn't work for srun / direct launch, etc.) do a test and communicate the results to the rest of the local procs -- maybe in the modex?
I think as as user I'd be quite surprised if my MPI job was spawning sub-processes during MPI_Init().
Ashley Pittman, Bath, UK.
Padb - A parallel job inspection tool for cluster computing