[Mpi-22] Should all constants/types be available inall languagebindings?

[Supalov, Alexander]

Thanks. We can surely define all datatypes everywhere in MPI-2.2. It
appears however that the current arrangement, with Fortran types defined
in C and C++, may be adequate. 

-----Original Message-----
From: mpi-22-bounces_at_[hidden]
[mailto:mpi-22-bounces_at_[hidden]] On Behalf Of Hubert Ritzdorf
Sent: Friday, October 24, 2008 3:43 PM
To: MPI 2.2
Subject: Re: [Mpi-22] Should all constants/types be available inall
languagebindings?

Hi,

as far as I remember it was cleared in the MPI 2.1
standardization process that "all" datatypes have to be
defined in all 3 languages.
Changelog item 2 requires this explicitly for MPI_LONG_LONG,
MPI_LONG_LONG_INT, ...
(But I think that some C++ datatypes are missing since there wasn't
defined a name).

Possibly, Jeff is not referencing MPI 2.1 implementations.

Supalov, Alexander wrote:
> Hi,
>
> I think we should answer the following questions to decide whether and
> how to define the constants:
>
> 1. When would a C MPI program call Fortran MPI subprogram? Probably,
> never.
> 2. When would a Fortran MPI program call a C MPI subprogram?
Sometimes.
> 3. When would a C++ MPI program call Fortran MPI program? Probably,
> never.
>   
I don't agree. I know some programs of this kind.

Hubert
> 4. When would a Fortran MPI program call a C++ MPI program? Probably,
> never.
>
> Here, "subprogram" means a part of program that relies on the MPI use
or
> knowledge of MPI datatypes, etc. This may or may not be a direct call
> into the respective MPI library.
>
> >From this, what is needed is to define Fortran datatypes from mpif.h
in
> C mpi.h. The rest does not seem relevant. Even the existing C++
> definitions may just reflect C heritage.
>
> Best regards.
>
> Alexander
>
> -----Original Message-----
> From: mpi-22-bounces_at_[hidden]
> [mailto:mpi-22-bounces_at_[hidden]] On Behalf Of Jeff Squyres
> Sent: Thursday, October 23, 2008 10:13 PM
> To: MPI 2.2
> Subject: [Mpi-22] Should all constants/types be available in all
> languagebindings?
>
> I notice that OMPI, MPICH2, Intel MPI, and HP MPI all do the
following:
>
>   * define Fortran datatypes in mpi.h (e.g., MPI_INTEGER, MPI_DOUBLE)
>   * define Fortran datatypes in the C++ MPI namespace (e.g.,  
> MPI::INTEGER, MPI::DOUBLE, etc.)
>   * do *not* define C datatypes in mpif.h (e.g., MPI_INT, MPI_FLOAT,  
> etc.)
>
> Why?  AFAICT, there is no rule about what constants have to appear in

> which language bindings.  But doesn't that implicitly mean that all  
> constants are supposed to appear in all language bindings?
>
> (the argument for having MPI_DOUBLE available in C, for example, is  
> that a C routine may be invoked to send or receive a message  
> containing Fortran data.  Similar arguments exist for why you'd want  
> MPI datatypes from other languages available in your language)
>
> This is also related to whether the type MPI::Fint should exist or
not.
>
> I just filed a ticket about these issues
> (https://svn.mpi-forum.org/trac/mpi-forum-web/ticket/56 
> ) and marked it as "feedback requested", meaning that I need feedback

> from the Forum before a proposal can be made.
>
> What do people think?
>
>   
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