[Mpi3-bwcompat] MPI Backward Compatibility Working Group

[Solt, David George]

During our meeting today we decided that MPI_Count should be at least as large as an MPI_Aint.    We already had the restriction that it had to be as large as a C/Fortran integer.   We want both restrictions (they cannot be combined because there is no guarantee that MPI_Aint > integer).

I'll throw this out as a starting point for discussion:

2.5.8  Last sentence change to:

The size of the MPI_Count type is determined by the MPI implementation
with the restriction that it must be minimally capable of encoding a C int and Fortran INTEGER
and any value that may be stored in an MPI_Aint type.

Rational thingy:

MPI_Count is used to communicate both the number of elements in a datatype and the bounds of a datatype.
The number of elements in a datatype is specified at creation time using a C int or Fortran INTEGER.   The bounds
may be specified using an MPI_Aint.

So, I was especially brief here.   I did not want to get into the "new" routines vs. "old routines", but if you attempt to go into more depth than what I said, you will inevitably end up going down that path.  I can think of a thousand ways not to say it, but its hard to come up with a good way.
Dave



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