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Subject: Re: [OMPI users] enable-mpi-threads
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-06-30 07:23:13

On Jun 30, 2009, at 1:29 AM, rahmani wrote:

> I want install openmpi in a cluster with multicore processor.
> Is it necessary to configure with --enable-mpi-threads option?
> when this option should be used?

Open MPI's threading support is functional but not optimized.

It depends on the problem you're trying to solve. There's many ways
to write software, but two not-uncommon models for MPI applications are:

1. Write the software such that MPI will launch one process for each
core. You communicate between these processes via MPI communication
calls such as MPI_SEND, MPI_RECV, etc.

2. Write the software that that MPI will launch one process per host,
and then spawn threads for all the cores on that host. The threads
communicate with each other via typical threaded IPC mechanisms
(usually not MPI); MPI processes communicate across hosts via MPI
communication calls. Sometimes MPI function calls are restricted to
one thread; sometimes they're invoked by any thread.

So it really depends on how you want to write your software. Make

Jeff Squyres
Cisco Systems