[Mpi-forum] MPI_Count

[Rajeev Thakur]

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

Rajeev 

> -----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.
> 
> -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.
> >
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