From: Karl Feind <kaf@XXXXXXX>
Date: January 19, 2007 7:43:38 AM CST
To: Jeff Squyres <jsquyres@XXXXXXXXX>
Cc: Karl Feind <kaf@XXXXXXX>,mpi-comments@XXXXXXXXXXXXX, Steven  
Reinhardt <spr@XXXXXXX>, mpi-users@mcs.anl.govSubject: Re: [MPICH] standardizing 64 bit integer MPI

Hi Jeff,

We have an actual user/partner that needs the message sizes > 2^31.

By the way, I know that a few vendors have solved the issue on non-Linux
systems.   Part of the solution in these cases involves supporting a
C compiler option to change "int" to 64 bits.  I suppose we could try
to put pressure on GNU to provide this option for GCC, or we could
address the issue by enhancing the MPI standard.

Since most libraries and all system headers assume the default "int"  
size,
changing the size of int by compiler option does present problems.  It
essentially creates a new ABI and requires ALL libraries to be provided
in that flavor.  This is why I think enahncing the MPI standard is a
better approach.

Karl

On Thu, Jan 18, 2007 at 11:26:07PM -0500, Jeff Squyres wrote:
> Greetings Karl!
>
> Just curious: do you have a current customer demand for this?  I.e.,
> are there real-world apps out there that could benefit from Enormous
> counts/sizes?  Or are you mainly trying to look forward and
> anticipate the need?
>