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

Subject: Re: [Boost-users] mpi non-blocking communication
From: Riccardo Murri (riccardo.murri_at_[hidden])
Date: 2010-12-08 08:39:40

Hi Hicham,

On Tue, Dec 7, 2010 at 9:37 AM, Hicham Mouline <hicham_at_[hidden]> wrote:
>> 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.
>
> I am just curious as to the value of distinguishing between these 2.
> Is it just informative?

The distinction could be important to the MPI implementation, in that
it may have to take some further steps if threads are used *at all*,
e.g., using the re-entrant version of C library calls.

(Whether it actually makes any difference, it really depends on the
MPI library.)

More info in the "Rationale" paragraph at:

  http://www.mpi-forum.org/docs/mpi22-report/node260.htm#Node260

Cheers,
Riccardo