[Mpi-forum] ABI

[Supalov, Alexander]

Hi everybody,

We looked into this matter in substantial detail back in the times of ABI WG (pre-MPI-2.1, I think). Details can be found in https://svn.mpi-forum.org/trac/mpi-forum-web/wiki/AbiWikiPage#no1 .

Best regards.

Alexander

-----Original Message-----
From: mpi-forum [mailto:mpi-forum-bounces at lists.mpi-forum.org] On Behalf Of N.M. Maclaren
Sent: Thursday, December 05, 2013 10:44 AM
To: Main MPI Forum mailing list
Subject: Re: [Mpi-forum] ABI

On Dec 4 2013, Jed Brown wrote:
>
>However, the question of integer (MPICH) versus pointer (OMPI) handles 
>is a long-standing impasse.

Yes, but I don't think that it's the worst issue.

>Suppose MPICH used intptr_t for handles.  I believe pointers are 
>treated the same as integers for all the common calling conventions.

I wouldn't bet on it, especially not in the medium term.  It's true on systems like the x86 (and its predecessor in dominance System/370), but I don't know all of the systems that either of those has been ported to.
It certaainly used not to be the case.

> This
>leaves a question of the predefined constants, which are currently 
>compile-time constants of some sort (either integers or addresses of 
>privately-defined structs), but I'm not aware of text in the standard 
>that requires them to be defined in a header.  That is, can we have
>
>  extern MPI_Datatype MPI_INT;
>
>in the header and leave it to the library to provide the value?

The killer there is whether they can be used in initialisations.  That would break:

    static MPI_Datatype weeble = MPI_INT;

Lastly, there are some very nasty differences that would have to be tackled, such as:

    Attributes (especially the I/O ones).  I meant to propose some fixes for MPI 3 (the current specification is weird), but didn't do it.  Sorry.
But there are probably quite a lot of such corner-cases.

    Implementation assumptions.  Not just signals and threading, but the handling of stdin/stdout/stderr, passive one-sided and more.

This doesn't mean that it can't be done, merely that it isn't as easy as just agreeing the types and values.


Regards,
Nick Maclaren.





_______________________________________________
mpi-forum mailing list
mpi-forum at lists.mpi-forum.org
http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-forum
Intel GmbH
Dornacher Strasse 1
85622 Feldkirchen/Muenchen, Deutschland
Sitz der Gesellschaft: Feldkirchen bei Muenchen
Geschaeftsfuehrer: Christian Lamprechter, Hannes Schwaderer, Douglas Lusk
Registergericht: Muenchen HRB 47456
Ust.-IdNr./VAT Registration No.: DE129385895
Citibank Frankfurt a.M. (BLZ 502 109 00) 600119052