On 02/23/2013 06:49 PM US Central Time, Jeff Hammond wrote:

My understanding, having looked at the code for this, is that no thread binding is set. The OS will hopefully do the right thing when the cores are undersubscribed, but I see no thread affinity code in the MPICH source for the comm threads.

This is incorrect. Hydra allows you to bind a process to a cpuset. If you are using an affinity thread, make sure your cpuset has at least 2 cores in it. -- Pavan -- Pavan Balaji http://www.mcs.anl.gov/~balaji