[MPI3 Fortran] What to do with mpif.h in MPI-3?

Jeff Squyres jsquyres at cisco.com
Mon Jan 25 11:29:03 CST 2010

On Jan 24, 2010, at 6:38 PM, Torsten Hoefler wrote:

> > What is everyone's opinion on which (1-4) the Forum should go with?
> It seems like the route to go with the C-bindings (and also the general
> bindings) is not clear yet and this would decide the outcome. Because if
> we decide to take the "64-bit" (tm) approach and double the number of
> function symbols, then the issue would be much simpler. However, if we
> decide to take the int -> MPI_Count approach, then I don't see how we
> can "extend" F77 in a standard-conforming and portable manner (but I
> might miss something).

Hmm -- maybe I missed something in ATL, but I thought we agreed that we would do *both* things:

- Add new versions of various MPI functions with a <suffix> appended (e.g., MPI_File_write<suffix>) and take the large count parameter
- The large count parameter in these new functions would have (in C) a parameter type of MPI_Count

There has been some discussion on the mailing list (by 1 person) since ATL about *not* using an "MPI_Count" datatype (rather, use uint64_t or somesuch), but my $0.02 is that we should use MPI_Count.

> So depending on the outcome, I would vote:
> - if we choose the extra function symbol for long types: option 4
> - if we choose the MPI_Count approach: option 3

Based on my understanding, I'm not sure how to parse your answer because the current direction of the Forum is to do *both* things: new functions *and* use MPI_Count.

Jeff Squyres
jsquyres at cisco.com

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