thakur at mcs.anl.gov
Mon Jan 25 15:43:21 CST 2010
We could still use MPI_Count and specify that it must be at least 64 bit.
> -----Original Message-----
> From: mpi-forum-bounces at lists.mpi-forum.org
> [mailto:mpi-forum-bounces at lists.mpi-forum.org] On Behalf Of
> Darius Buntinas
> Sent: Monday, January 25, 2010 3:34 PM
> To: Main MPI Forum mailing list
> Subject: Re: [Mpi-forum] MPI_Count
> I liked Mark's suggestion. Using MPI_Count rather than
> explicitly fixing the size means the user has to check for overflow.
> Did the person state what the portability issues with int64_t
> could be?
> Is there a C "basic type" that would be compatible with a
> fortran INTEGER*8? BTW, we already added stdint datatypes to MPI 2.2.
> On 01/25/2010 03:04 PM, Jeff Squyres wrote:
> > On Jan 24, 2010, at 9:21 PM, Snir, Marc wrote:
> >> I would suggest to use explicitly 64 bit integers as the
> type of count in the new functions. I.e., int64_t in C and
> INTEGER(KIND=8) in Fortran. Both types are part of the
> (C/Fortran) standard.
> > FWIW, I mentioned the above point on the MPI3 Fortran WG
> mailing list and got this reply:
> >> Please do not touch any of the<stdint.h> stuff with a bargepole!
> >> Stick to the basic types and MPI type names.
> >> There are many different ways where<stdint.h> integers cause
> >> portability, efficiency and other problems. Inter alia,
> the current
> >> revision of C is thinking of changing them in ways that could be
> >> incompatible with old code, and they are semantically incompatible
> >> with Fortran and many other languages in several respects.
> >> MPI_count gives the opportunity to evade any such chaos, whether
> >> introduced by the standard or an implementation.
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