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Subject: Re: [OMPI users] Do MPI calls ever sleep?
From: David Ronis (David.Ronis_at_[hidden])
Date: 2010-07-21 15:20:24


Hi Jed,

Thanks for the reply and suggestion. I tried adding -mca
yield_when_idle 1 (and later mpi_yield_when_idle 1 which is what
ompi_info reports the variable as) but it seems to have had 0 effect.
My master goes into fftw planning routines for a minute or so (I see the
threads being created), but the overall usage of the slaves remains
close to 100% during this time. Just to be sure, I put the slaves into
a MPI_Barrier(MPI_COMM_WORLD) while they were waiting for the fftw
planner to finish. It also didn't help.

Do you know where is yield_when_idle documented?

David

On Wed, 2010-07-21 at 20:24 +0200, Jed Brown wrote:
> On Wed, 21 Jul 2010 14:10:53 -0400, David Ronis <David.Ronis_at_[hidden]> wrote:
> > Is there another MPI routine that polls for data and then gives up its
> > time-slice?
>
> You're probably looking for the runtime option -mca yield_when_idle 1.
> This will slightly increase latency, but allows other threads to run
> without competing with the spinning MPI.
>
> Jed
>