[O-MPI users] Re: [Beowulf] Alternative to MPI ABI

Greg Lindahl lindahl at pathscale.com
Fri Mar 25 18:26:28 EST 2005


On Fri, Mar 25, 2005 at 05:49:13PM -0500, Jeff Squyres wrote:

> MorphMPI (or, as Patrick suggests, we need a cooler name -- PatrickMPI? 
> ;-) ) is the work of 1 grad clever student (or anyone else industrious 
> enough).  Elapsed time: a few months.

Right.

> Making even 2 MPI implementations agree on an ABI is an enormous amount 
> of work.  Given that two major MPI implementations take opposite sides 
> on the pointers-vs.integers for MPI handles debate (and I suspect that 
> neither is willing to change), just getting them to agree on one of 
> them will be a major amount of work.  Then changing the internals of 
> one of those MPIs to match the other is another enormous amount of work 
> (death by a million cuts).

You yourself said how MPI implementers would actually implement this
without needing to change any internals: Make the C interface routines
do the same thing that F77 does today. Elapsed time: a few months,
same as MorphMPI. No internals need to be changed.

I suppose the good news is that if this is your main objection,
then it's gone.

> Also, as I pointed out in my original alternate proposal, with 
> PatrickMPI, only those who want to use an ABI will use it.  Those who 
> do *not* want an ABI do not have to have it forced upon them.

I missed where anyone was being forced to do anything. MPI
implementers can support the ABI alongside their current interface or
not, it's their choice.

-- greg

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