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Subject: Re: [OMPI users] OpenMPI problem on Fedora Core 12
From: Eugene Loh (Eugene.Loh_at_[hidden])
Date: 2010-01-12 10:57:50


Jeff Squyres wrote:

>It would be very strange for nanosleep to cause a problem for Open MPI -- it shouldn't interfere with any of Open MPI's mechanisms. Double check that your my_barrier() function is actually working properly -- removing the nanosleep() shouldn't affect the correctness of your barrier.
>
>
I read Gijsbert's e-mail differently. Apparently, the issue is not
MPI/OMPI at all, but a hang inside nanosleep.

>On Dec 31, 2009, at 1:15 PM, Gijsbert Wiesenekker wrote:
>
>
>>I only recently learned about the OMPI_MCA_mpi_yield_when_idle variable, I still have to test if that is an alternative to my workaround.
>>
>>
mpi_yield_when_idle does not free the CPU up very much. It still polls
fairly aggressively, and the yield() call doesn't really free the CPU up
that much. It's a weak and probably ungratifying solution for your problem.

>>Meanwhile I seem to have found the cause of problem ...
>>... rather than OpenMPI being the problem, nanosleep is the culprit because the call to it seems to hang.
>>
>>
So, "we" (OMPI community) are off the hook? Problem is in nanosleep?
"We" are relieved (or confused about what you're reporting)!