Yes, though the degree of impact obviously depends on the messaging pattern of the app. 

On Oct 31, 2013, at 2:50 AM, MM <finjulhich@gmail.com> wrote:

Of course, by this you mean, with the same total number of nodes, for e.g. 64 process on 1 node using shared mem, vs 64 processes spread over 2 nodes (32 each for e.g.)?


On 29 October 2013 14:37, Ralph Castain <rhc@open-mpi.org> wrote:
As someone previously noted, apps will always run slower on multiple nodes vs everything on a single node due to the shared memory vs IB differences. Nothing you can do about that one.
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