On May 26, 2006, at 6:55 AM, Jeff Squyres ((jsquyres)) wrote:
MPI_THREAD_MULITPLE is "somewhat" supported, meaning that support
for it was designed in to Open MPI, but it has not been fully
stress tested. As such, there is likely to still be bugs when
using multiple user threads with MPI_THREAD_MULTIPLE.
fork() is not technically supported by the MPI standard. If you
*need* to fork(), you might want to look at alternate mechanisms if
you need to move between multiple MPI implementations because
support for it is not likely to be portable.
Within Open MPI, fork() will almost certainly fail if you use the
OS-bypass networks (Myrinet, InfiniBand). The mechanisms that
these networks use for high-speed/low latency are quite problematic
with fork(). If you are using tcp or shared memory, fork() *might*
work, but this is not something that we have extensively tested.
I did some work on that last week. Jeff is right all OS bypass
network don't like fork. Once you fork the status of the application
is "not usable". SM and TCP kind of support it, if you never do
communications on the child. But that's not what you're looking for.
Therefore the generic answer is never use fork in an MPI application
once you called MPI_Init (not even after MPI_Finalize).
Thanks,
george.
From: users-boun...@open-mpi.org [mailto:users-bounces@open-
mpi.org] On Behalf Of imran shaik
Sent: Friday, May 26, 2006 1:50 AM
To: openMPI mailing list
Subject: [OMPI users] Thread Safety
Hi,
I am a newbie to OpenMPI.
Can anyone say how the support for MPI_THREAD_MULTIPLE is
implemented in openMPI?
Is thread safety completely provided in openMPI? or does it still
has some bugs?
I am currently using LAM/MPI.But i need concurrent threads making
MPI calls. So i am planning to move to another implementation of
MPI. Can i choose openMPI?
Also, is "fork"(for child preoces creation) still a no-no in
openMPI too? Can a child process(forked) make concurrent MPI calls
along with its parent ?
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