[Mpi-forum] [EXTERNAL] Re: An f2c question

[Pritchard Jr., Howard]

Thanks Rolf!

On 8/24/21, 3:26 PM, "Rolf Rabenseifner" <rabenseifner at hlrs.de> wrote:

    %IMPI_VAL was a typo. %MPI_VAL is correct, see MPI-4.0 page 18, line 20.

    ----- Original Message -----
    > From: "Pritchard" <howardp at lanl.gov>
    > To: "Rolf Rabenseifner" <rabenseifner at hlrs.de>, "Main MPI Forum mailing list" <mpi-forum at lists.mpi-forum.org>
    > Sent: Tuesday, August 24, 2021 10:55:51 PM
    > Subject: Re: [EXTERNAL] Re: [Mpi-forum] An f2c question

    > Hi Ralph,
    > 
    > Okay, not quite right, looks like both mpich and open mpi use %MPI_VAL, so I'll
    > go with that.
    > 
    > Thanks,
    > 
    > Howard
    > 
    >On 8/24/21, 2:28 PM, "Rolf Rabenseifner" <rabenseifner at hlrs.de> wrote:
    > 
    >    Dear Howard,
    > 
    >    SUBROUTINE MPI_TYPE_COMMIT(DATATYPE, IERR)
    >    INTEGER :: IERR
    >    ! some module USE to include the definition of TYPE(MPI_Datatype)
    >    TYPE(MPI_Datatype) :: DATATYPE
    >    CALL MPI_X_TYPE_COMMIT(DATATYPE%IMPI_VAL, IERR)
    >    RETURN
    >    END
    > 
    >    I do not know how to handle the optional ierr, but here is the way you should
    >    handle the datatype handle.
    > 
    >    Best regards
    >    Rolf
    > 
    >    ----- Original Message -----
    >    > From: "Main MPI Forum mailing list" <mpi-forum at lists.mpi-forum.org>
    >    > To: "Main MPI Forum mailing list" <mpi-forum at lists.mpi-forum.org>
    >    > Cc: "Pritchard" <howardp at lanl.gov>
    >    > Sent: Tuesday, August 24, 2021 10:19:27 PM
    >    > Subject: [Mpi-forum] An f2c question
    > 
    >    > Hi All,
    >    > 
    >    > 
    >    > 
    >    > In porting an MPI application written mainly in Fortran and a little c to using
    >    > mpi_f08 rather than mpi, I’ve hit an issue.
    >    > 
    >    > 
    >    > 
    >    > Namely, how would I write example 19.11 in the MPI 4 standard if the app uses
    >    > type(MPI_Type) rather than integer?
    >    > 
    >    > Note I’m working with an application, so the MPI_Type structure is opaque, or at
    >    > least I thought we’re supposed to treat it as opaque.
    >    > 
    >    > 
    >    > 
    >    > Here’s the example:
    >    > 
    >    > 
    >    > 
    >    > Example 19.11 The example below illustrates how the Fortran MPI function
    >    > 
    >    > MPI_TYPE_COMMIT can be implemented by wrapping the C MPI function
    >    > 
    >    > MPI_Type_commit with a C wrapper to do handle conversions. In this example a
    >    > Fortran-C
    >    > 
    >    > interface is assumed where a Fortran function is all upper case when referred to
    >    > from C and
    >    > 
    >    > arguments are passed by addresses.
    >    > 
    >    > ! FORTRAN PROCEDURE
    >    > 
    >    > SUBROUTINE MPI_TYPE_COMMIT(DATATYPE, IERR)
    >    > 
    >    > INTEGER :: DATATYPE, IERR
    >    > 
    >    > CALL MPI_X_TYPE_COMMIT(DATATYPE, IERR)
    >    > 
    >    > RETURN
    >    > 
    >    > END
    >    > 
    >    > /* C wrapper */
    >    > 
    >    > void MPI_X_TYPE_COMMIT(MPI_Fint *f_handle, MPI_Fint *ierr)
    >    > 
    >    > {
    >    > 
    >    > MPI_Datatype datatype;
    >    > 
    >    > datatype = MPI_Type_f2c(*f_handle);
    >    > 
    >    > *ierr = (MPI_Fint)MPI_Type_commit(&datatype);
    >    > 
    >    > *f_handle = MPI_Type_c2f(datatype);
    >    > 
    >    > return;
    >    > 
    >    > }
    >    > 
    >    > 
    >    > 
    >    > Now I suspect that most of the time if one has some old ‘c’ code assuming a
    >    > pointer to a 4 byte fortran integer argument for the datatype is just going to
    >    > work, but I’d rather not just try to be lucky.
    >    > 
    >    > Anyway, there are fortran gurus on this project and they’d be sure to want a
    >    > better solution.
    >    > 
    >    > 
    >    > 
    >    > Thanks for any help/ideas,
    >    > 
    >    > 
    >    > 
    >    > Howard
    >    > 
    >    > 
    >    > 
    >    > 
    >    > 
    >    > —
    >    > 
    >    > 
    >    > 
    >    > 
    >    >        
    >    > 
    >    > Howard Pritchard
    >    > 
    >    > Research Scientist
    >    > 
    >    > HPC-ENV
    >    > 
    >    > 
    >    > 
    >    > Los Alamos National Laboratory
    >    > 
    >    > howardp at lanl.gov
    >    > 
    >    > 
    >    > 
    >    > [ https://www.instagram.com/losalamosnatlab/ ] [
    >    > https://twitter.com/LosAlamosNatLab ] [
    >    > https://www.linkedin.com/company/los-alamos-national-laboratory/ ] [
    >    > https://www.facebook.com/LosAlamosNationalLab/ ]
    >    > 
    >    > 
    >    > 
    >    > 
    >    > 
    >    > 
    >    > _______________________________________________
    >    > mpi-forum mailing list
    >    > mpi-forum at lists.mpi-forum.org
    >    > https://lists.mpi-forum.org/mailman/listinfo/mpi-forum
    > 
    >    --
    >    Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de .
    >    High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 .
    >    University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 .
    >    Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner .
    >     Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307) .

    -- 
    Dr. Rolf Rabenseifner . . . . . . . . . .. email rabenseifner at hlrs.de .
    High Performance Computing Center (HLRS) . phone ++49(0)711/685-65530 .
    University of Stuttgart . . . . . . . . .. fax ++49(0)711 / 685-65832 .
    Head of Dpmt Parallel Computing . . . www.hlrs.de/people/rabenseifner .
    Nobelstr. 19, D-70550 Stuttgart, Germany . . . . (Office: Room 1.307) .