We could still use MPI_Count and specify that it must be at least 64 bit. Rajeev

-----Original Message----- From: [email protected] [mailto:[email protected]] 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.

-d

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.

_______________________________________________ mpi-forum mailing list [email protected] http://lists.mpi-forum.org/mailman/listinfo.cgi/mpi-forum