[Beowulf] Alternative to MPI ABI

[Jeff Squyres]

On Mar 25, 2005, at 5:03 PM, Greg Lindahl wrote:

>> I don't see it that way. First, the implementations of the translation
>> layers will be done by each MPI implementations.
>
> In which case it's basically the same as doing an ABI. Or did I miss
> something?  Does this somehow save a significant amount of work for
> anyone?

YES!

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.

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).

And MPI handles is only one issue.  Consider all the rest of the 
issues...  Elapsed time: 2 years (that's optimistic).

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.

-- 
{+} Jeff Squyres
{+} The Open MPI Project
{+} http://www.open-mpi.org/