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Subject: Re: [OMPI users] EXTERNAL: Re: What's the status of OpenMPI and thread safety?
From: Ralph Castain (rhc_at_[hidden])
Date: 2013-12-20 19:03:33


Hi Ed

FWIW: Intel MPI has better thread support, though you'll lose some features. I don't know what NICs you have, but have you tried running with the MTL's instead of the openib BTL? Both the psm and mxm MTLs are supposed to be thread safe, and will outperform the openib BTL anyway.

Not sure if Intel supports mxm or not - should handle psm as Intel now owns Truescale.

HTH
Ralph

On Dec 19, 2013, at 7:23 AM, Blosch, Edwin L <edwin.l.blosch_at_[hidden]> wrote:

> Thanks Ralph,
>
> We are attempting to use 1.6.4 with an application that requires multi-threading, and it is hanging most of the time; it is using openib. They steered us to try Intel MPI for now. If you lack drivers/testers for improved thread safety on openib, let me know and I’ll encourage the developers of the application to support you.
>
> Ed
>
> From: users [mailto:users-bounces_at_[hidden]] On Behalf Of Ralph Castain
> Sent: Wednesday, December 18, 2013 6:50 PM
> To: Open MPI Users
> Subject: EXTERNAL: Re: [OMPI users] What's the status of OpenMPI and thread safety?
>
> This was, in fact, a primary point of discussion at last week's OMPI developer's conference. Bottom line is that we are only a little further along than we used to be, but are focusing on improving it. You'll find good thread support for some transports (some of the MTLs and at least the TCP BTL), not so good for others (e.g., openib is flat-out not thread safe).
>
>
> On Dec 18, 2013, at 3:57 PM, Blosch, Edwin L <edwin.l.blosch_at_[hidden]> wrote:
>
>
> I was wondering if the FAQ entry below is considered current opinion or perhaps a little stale. Is multi-threading still considered to be ‘lightly tested’? Are there known open bugs?
>
> Thank you,
>
> Ed
>
>
> 7. Is Open MPI thread safe?
>
> Support for MPI_THREAD_MULTIPLE (i.e., multiple threads executing within the MPI library) and asynchronous message passing progress (i.e., continuing message passing operations even while no user threads are in the MPI library) has been designed into Open MPI from its first planning meetings.
>
> Support for MPI_THREAD_MULTIPLE is included in the first version of Open MPI, but it is only lightly tested and likely still has some bugs. Support for asynchronous progress is included in the TCP point-to-point device, but it, too, has only had light testing and likely still has bugs.
>
> Completing the testing for full support of MPI_THREAD_MULTIPLE and asynchronous progress is planned in the near future.
>
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