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Subject: Re: [OMPI users] MPI flavor-agnostic libraries
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-01-14 10:00:19


On Jan 14, 2009, at 9:49 AM, Gregory D Abram wrote:

> I'd like to release binary libraries that use MPI but are agnostic
> as to which flavor or MPI (eg. OpenMPI, MVAPICH, LAM...) that is
> used by the application linking the libraries. I've seen that there
> are some significant differences that stand in the way, for example
> that MPI_Comm is a pointer on OpenMPI and an integer on MVAPICH. I
> can see some ways that might work, but they are pretty complex - for
> example, I could create an intercept library that loads a real MPI
> library explicitly and do whatever needs be done (for example,
> translating MPI_Comm parameters). Does anyone know of anything that
> might help?
>

This is the age-old "there is no MPI ABI" issue. :-\ The root of the
issue is that MPI is [at least currently] defined to be source code
compatible, not binary compatible.

A "MorphMPI" solution has been proposed and discussed many times
(similar to what you describe -- a thin intercept layer than acts as a
translator to multiple back-end MPI implementations, probably loaded
dynamically at run-time), but no one has implemented a general purpose
solution that could be standardized across/used by any MPI software
package.

Most MPI software packages either distribute binaries for each
different MPI implementation that they want to support or distribute
source code and allow themselves to be compiled against multiple
different MPI implementations (which, these days, isn't too
difficult). Neither of these are optimal solutions, obviously.

-- 
Jeff Squyres
Cisco Systems