On Wed, 4 May 2011, Eugene Loh wrote:
Depending on what version you use, the option has been renamed
--enable-mpi-thread-multiple.
Anyhow, there is widespread concern whether the support is robust. The
support is known to be limited and the performance poor.
Thanks :)
I absolutely see why support for MPI_THREAD_MULTIPLE is a configure option
(not at all related to the fact I'm on a platform where my best
interconnect gets disabled if you ask for it).
However, do the same concerns apply to MPI_THREAD_FUNNELED and
MPI_THREAD_SERIALIZED? They are disabled by default too and they look
difficult to enable without enabling some other functionality.
Details:
Jeff said (on this list, Tue, 14 Dec 2010 22:52:40) that, in OpenMPI,
there's no difference between MPI_THREAD_SINGLE and MPI_THREAD_FUNNELED.
Yet, with the default configure options, MPI_Init_thread will always
return MPI_THREAD_SINGLE.
* Release 1.4.3 - MPI_THREAD_(FUNNELED|SERIALIZED) are only available if
you specify "--mpi-threads". Codes that sensibly negotiate their thread
level automatically start using MPI_THREAD_MULTIPLE and my interconnect
(openib) is disabled.
* Release 1.5.3 - MPI_THREAD_(FUNNELED|SERIALIZED) are only available if
you specify "--mpi-threads" (same problems as with 1.4.3), or enable
asynchronous communication progress (whatever that is - but it sounds
scary) with "--enable-progress-threads"
Things do look different again in trunk, but seem to require you to at
least ask for "--enable-opal-multi-threads".
Are we supposed to be able to use MPI_THREAD_FUNNELED by default or not?
Best wishes,
Mark
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