[mpich2-dev] Fw: 32-bit ROMIO: What is the best solution?

[Bob Cernohous]

I'm moving a discussion here from the IBM/Argonne open source DCMF mailing
list (http://dcmf.anl-external.org/wiki).

Very briefly, we're making MPI_Aint into a 64 bit signed value on 
32-bit MPICH2/ROMIO platforms.  This will fix problems with files larger
than 2G (and possibly other 4G virtual address problems).

We'd like to start sending fix patches to the mpich-dev community for 
comment.

The code base that we're patching is changing under us.  So our patches 
might not apply properly for members of this list.  When we're done, we
will have a patch for the current release of MPICH2.  For now, we'd like 
to provide these patches to the community for information and discussion.

If you're interested, there might be more technical history in the DCMF
archives.  Otherwise, start the discussion here.

bobc at us.ibm.com wrote on 02/27/2008 04:19:29 PM:
> 
> bobc at us.ibm.com wrote on 02/08/2008 02:41:40 PM: 
> 
> >We all realize there are issues with MPI_Aint's in 32 bit 
implementations. 
> >Using signed 32 bit addresses along with 64 bit offsets can result in 
> >some pretty broken code.  I've reproduced several problems on 
> >BGL/BGP/linux.   The problems are most obvious with romio files > 2G or 

> >virtual addresses > 2G. 
> 
> Earlier this month I posted some comments to this mailing list about 
> 32-bit MPICH/ROMIO/MPI_Aint issues (see above and the archive). 
> 
> We've started to work on the problem.   We're (optionally) making 
> MPI_Aint a 64 bit signed value even when integers/pointers are 32 bit 
> values. 
> 
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