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From: Cupp, Matthew R (cuppm_at_[hidden])
Date: 2006-10-16 11:25:54

Thanks for the info, Jeff.

It sounds like THREAD_SINGLE is the only known working option available
currently? Is there really a difference between that and
THREAD_FUNNELED? Like if I have 2 threads, but only the main thread is
the one making MPI calls, is that allowed? It seems to work, but I
wasn't sure if there was something else that would cause it to lock or
fail somewhere.

Matt Cupp
Battelle Memorial Institute
Statistics and Information Analysis

-----Original Message-----
From: users-bounces_at_[hidden] [mailto:users-bounces_at_[hidden]] On
Behalf Of Jeff Squyres
Sent: Friday, October 13, 2006 5:07 PM
To: Open MPI Users
Subject: Re: [OMPI users] OpenMPI 1.1.1 with Multiple Thread Support

The problem is that we haven't done a whole lot of testing yet for
multiple thread support. In particular, OMPI was fundamentally
designed for both THREAD_MULTIPLE and progression thread support, and
several groups have done testing to ensure that when compiled with
multiple thread support, OMPI doesn't just hang, but:

- I don't know if we have tested the progress thread support in quite
a long time, and
- Even though OMPI has been tested to ensure that we don't have
boneheaded extra locks/unlocks, not a whole lot of testing has
occurred to ensure that THREAD_MULTIPLE support is completely solid.

As such, I'd be surprised if THREAD_MULTIPLE works for any
applications that do anything reasonably "interesting" with multiple
threads and MPI (it pains me to say this, but I'd rather be honest
than string you along! :-( ).

That being said, THREAD_MULTIPLE support is going to become more
relevant in the next several months (i.e., various organizations have
a vested interest in THREAD_MULTIPLE and the work will resume in this