The MPI_Aint vs void * is a hack to deal with a combination of limitations in the MPI spec and in the MPICH2 implementation. Specifically, the real issue is to make MPI_Aint the same as MPI_Offset, though that's not the way it looks in their patch. Some things that they did, particularly the MPI_Pint and MPI_Puint, need to be changed to meet our naming conventions and avoid potential conflicts with MPI 3.

On May 2, 2008, at 3:11 AM, Pavan Balaji wrote:

Hi all,

Sorry about the delay in sending out the BG/P patches. I've placed them
here: http://www.mcs.anl.gov/~balaji/projects/mpich2/bgp/r2. I've
assigned a few patches to each person below. Can the below folks please
confirm that you can go over them and make sure there are no problems
integrating them into the trunk? The plan is to go over these and have a
telecon around mid next week.

The IBM folks didn't do a very good job in breaking up the diffs, so
some of the patches are large; you'll probably need to break them up and
try different parts separately.

build.patch -- Bill
datatype.patch -- Pavan
dcmfd.patch -- Pavan
debugger.patch -- Darius
ignore.patch -- Pavan
mpe.patch -- Anthony
other.patch -- Rajeev
test-build.patch -- Dave
test-source.patch -- Dave

A few things I noticed on a quick glance through the patches:

1. MPI_Aint vs. (void *). I remember that there was some discussion, but
what was the conclusion? Can MPI_Aint be larger than (void *)? A large
chunk of the patches assumes that these two can be different, so they
introduce MPI_AINT_TO_VOID_PTR and friends to deal with such cases.

2. Some of the patches (e.g., debugger.patch, test-build.patch and
test-source.patch) have a number of BG specific additions. These need to
be pruned out in a way that IBM can still use it, but they will continue
to be generic enough for other platforms.

Thanks.

-- Pavan

--
Pavan Balaji
http://www.mcs.anl.gov/~balaji

William Gropp

Paul and Cynthia Saylor Professor of Computer Science

University of Illinois Urbana-Champaign