[Beowulf] The Case for an MPI ABI

[Greg Lindahl]

On Wed, Feb 23, 2005 at 12:19:55PM +0100, Joachim Worringen wrote:

> Unfortunately, the value of an ABI is much reduced by the fact that the 
> most important target platform Linux itself has no stable ABI (think of 
> libc and other version nightmares). On a OS like Solaris or Windows, 
> this is much more of a benefit.

I don't think it's "much reduced" by this, but I think it's clear this
would be a matter of opinion. What you'll definitely be able to do is
run an application built on a particular Linux version with different
MPI libraries compiled for that same Linux version.  You are correct
that if the MPI library was built for a wildly different Linux distro
than the app, you can't necessarily put them together.

> Another problem are i.e. vendor-specific assertions that could conflict. 
> A solution for this could be "numerical namespaces" for such extensions, 
> but how should they be managed?

This is certainly something that a committe would discuss. There are
plenty of examples of this problem being solved successfully by
handing out numeric ranges.

> And what about the different calling-conventions in Fortran?

The calling conventions differences (in Linux) revolve around the
f2c-abi issue, and it so happens that no MPI routines trip on this
issue, as it only affects functions that return REAL*4 or COMPLEX
types. Did I miss a function that has those return types?

-- greg