[mpi-21] Proposal: MPI_OFFSET built-in type

[Robert Latham]

I hope this is less contentious than adding 'const' keywords...

I would like to propose a new built-in type MPI_OFFSET, defined to be
a type corresponding to INTEGER(KIND=MPI_OFFSET_KIND) or MPI_Offset

This is a minor addition to the standard, which would have no impact
on existing code while serving to simplify code which exchanges file
offsets among processes.

There is a workaround in the standard: a user can define a type from
MPI_BYTE:

 MPI_Type_contiguous(sizeof(MPI_Offset), MPI_BYTE, &offtype);

However, it would clearly be more convienient to operate on built-in
types.  

MPI Datatype: MPI_OFFSET
Corresponding C type: long long int
Corresponding Fortran type: INTEGER(KIND=MPI_OFFSET_KIND)

Thanks
==rob


-- 
Rob Latham
Mathematics and Computer Science Division    A215 0178 EA2D B059 8CDF
Argonne National Lab, IL USA                 B29D F333 664A 4280 315B