Re: [Boost-users] mpi non-blocking communication

-----Original Message----- From: boost-users-bounces@lists.boost.org [mailto:boost-users- bounces@lists.boost.org] On Behalf Of Riccardo Murri Sent: 07 December 2010 08:14 To: boost-users@lists.boost.org Subject: Re: [Boost-users] mpi non-blocking communication

Hi Hicham,

On Tue, Dec 7, 2010 at 12:10 AM, Hicham Mouline wrote:

...

On a related note, I posted a question to the openmpi forum. MPI_INIT is identical MPI_INIT_THREAD(MPI_THREAD_SINGLE), but I couldn't see the utility of having MPI_THREAD_FUNNELED.

MPI_THREAD_SINGLE = no threads at all.

MPI_THREAD_FUNNELED = you can have threads, but only the *main* thread (see below) issues MPI calls; you can think of this as: your application is multi-threaded, but it is single-threaded when it comes to MPI interaction.

Thanks Riccardo, I am just curious as to the value of distinguishing between these 2. Is it just informative? I mean, as you said, it is as if the application is single-threaded when it comes to MPI interaction. What value is there in telling the MPI implementation that we have other threads but they will not call you? I guess I'm stuck on this point, regards,