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Subject: Re: [OMPI users] [EXTERNAL] MPI_THREAD_SINGLE vs. MPI_THREAD_FUNNELED
From: Jai Dayal (dayalsoap_at_[hidden])
Date: 2013-10-23 14:10:32


Hi,

The version of Open MPI I'm using is
mpiexec (OpenRTE) 1.6.5

It's what's offered on this smaller batch scheduling cluster at Oak Ridge
(Sith to be exact).

Running the ompi_info command, I get

          Thread support: posix (MPI_THREAD_MULTIPLE: no, progress: no)
   FT Checkpoint support: no (checkpoint thread: no)

and in my MPI_Init_thread call, the provided flag is returned as
MPI_THREAD_SINGLE.

I was mainly concerned because we have a threaded middleware underneath to
communicate across MPI worlds that also uses the IB infrastructure and
verbs library, so I just wanted to get some clarity as to what exactly
MPI_THREAD_SINGLE meant.

Brian's answer seems to make perfect sense.

Thanks!

On Wed, Oct 23, 2013 at 1:47 PM, Jeff Hammond <jeff.science_at_[hidden]>wrote:

> On Wed, Oct 23, 2013 at 12:02 PM, Barrett, Brian W <bwbarre_at_[hidden]>
> wrote:
> > On 10/22/13 10:23 AM, "Jai Dayal" <dayalsoap_at_[hidden]> wrote:
> <snip>
> > I'm asking because I'm using an open_mpi build ontop of infiniband, and
> the
> > maximum thread mode is MPI_THREAD_SINGLE.
> >
> >
> > That doesn't seem right; which version of Open MPI are you using?
>
> The last time I looked at this, OpenMPI only supported
> MPI_THREAD_SINGLE by default and if you ask for any higher thread
> level, you get MPI_THREAD_MULTIPLE, which requires a configure-time
> switch.
>
> Maybe something has changed dramatically more recently than I tested.
> Squyres told me some thread-oriented refactoring was going on. All of
> this was over a year ago so it is entirely reasonable for me to be
> wrong about all of this.
>
> Jeff
>
> --
> Jeff Hammond
> jeff.science_at_[hidden]
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