Okay, so let me point out a second distinction from MVAPICH: the
default policy would be to spread out over sockets.
----- "Eugene Loh" <Eugene.Loh@Sun.COM> wrote:
This is an important discussion.
Indeed! My big fear is that people won't pick up the significance
of the change and will complain about performance regressions
in the middle of an OMPI stable release cycle.
2) The proposed OMPI bind-to-socket default is less severe. In the
general case, it would allow multiple jobs to bind in the same way
without oversubscribing any core or socket. (This comment added to
the trac ticket.)
That's a nice clarification, thanks. I suspect though that the
same issue we have with MVAPICH would occur if two 4 core jobs
both bound themselves to the first socket.