On 13/02/2014 21:59, Matthias Troyer wrote:
You need to ask the OpenMPI folks if they have a version that supports
threading on Windows
Small warning:
At least on Linux, OpenMPI can be built explicitly with threading
support. The same is probably true on other platforms, but the reason
why this is not the default is that some optimizations on the
communication layers are dropped in that mode (related with InfiniBand
if I recall correctly).
Regards
On 13 Feb 2014, at 21:23, MM <[email protected]
<mailto:[email protected]>> wrote:
my ompi_info says (openmpi)
Threading support: No
Does that mean it's not supported?
If so, what to do?
On 13 February 2014 17:00, Matthias Troyer <[email protected]
<mailto:[email protected]>> wrote:
On Feb 13, 2014, at 17:44, MM <[email protected]
<mailto:[email protected]>> wrote:
On 13 February 2014 15:33, Matthias Troyer <[email protected]
<mailto:[email protected]>> wrote:
Hi,
In orders to use MPI in a multi-threaded environment, even
when only one thread uses MPI, you need to request the
necessary level of thread support in the environment
constructor. Then you'd an check whether your MPI
implementation supports multi threading. Note that using MPI
the way you do need not work even though it seems safe at
first sight. One reason is that your MPI implementation
might use threads internally to support, e.g. nonblocking
calls and those threads might not be compatible with your
threads.
Matthias
So in my case, as I have a main thread that doesn't call MPI,
and another purposely created user thread to call MPI lib, the
mode is MPI_THREAD_FUNNELLED ?
as boost 1.54 doesn't have the level in the enviroment ctor, I
need to explicitly call the underlying
MPI::Init_thread(MPI_THREAD_FUNNELED).
once I move to 1.55, I'll use the env ctor.
You need MPI_THREAD_SERIALIZED since it is not the main thread
which is doing the MPI communication. Be sure to check whether
that level is actually supported.
Matthias
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Alain Miniussi
DSI/Pôle Génie Logiciel Scientifique
Observatoire de la Côte d'Azur
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