On Dec 17, 2013, at 11:04 AM, Ralph Castain <r...@open-mpi.org> wrote:
> Are you binding the procs? We don't bind by default (this will change in > 1.7.4), and binding can play a significant role when comparing across kernels. > > add "--bind-to-core" to your cmd line I've previously always used mpi_paffinity_alone=1, and the new behavior seems to be independent of whether or not I use it. I'll try bind-to-core. One more possible clue. I haven't done a full test, but for one particular setup (newer nodes, single node so presumably using sm), there are apparently two ways to fix the problem: 1. go back to the previous kernel, but stick with openmpi 1.7.3 2. stick with the new kernel, but go back to openmpi 1.6.4 So it appears to be some interaction between the new kernel and 1.7.3 that isn't present with 1.6.4. We specifically switched to 1.7.3 because of a bug in 1.6.4 (lock up in some collective communication), but now I'm wondering whether I should just test 1.6.5. Noam
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