[Beowulf] Alternative to MPI ABI

Greg Lindahl lindahl at pathscale.com
Thu Mar 24 17:34:48 PST 2005

> Create a new software project (preferably open source, preferably with 
> an BSD-like license so that ISV's can incorporate this software into 
> their products) that provides a compatibility layer for all the 
> different MPI implementations out there.  Let's call it MorphMPI.


A similar idea was actually written up by Bill Gropp and was mentioned
by him 5 weeks ago on the beowulf list. Quoth he:

| I wrote a paper that appeared in the EuroPVMMPI'02 meeting that discusses 
| the issues of a common ABI.  The paper is "Building Library Components That 
| Can Use Any MPI Implementation" and is available as 
| http://www-unix.mcs.anl.gov/~gropp/bib/papers/2002/gmpishort.pdf .

I think this overall idea falls short of the benefit of an ABI for a
couple of reasons. The first is that it's unlikely to get wide
distribution if it doesn't come with MPI implementations. The second
is that it's harder to maintain "out of tree"; the minute that an MPI
implementation changes something, MorphMPI is going to be broken.

You keep on coming back to this:

> 2. Cancel the MPI Implementor's Ultimate Prize Fighting Cage Match on 
> pay-per-view (read: no need for time-consuming, potentially fruitless 
> attempts to get MPI implementors to agree on anything)

Was there a big fight over the Fortran interface? It nails down the
types because it has to. All the ABI does is make C look like Fortran;
no internals need change in any implementation.

-- greg

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