I would prefer a solution where an application or middlware can check at runtime whether the Fortran MPI datatypes exist, i.e., I like mpich's solution. It is more simple than all methods that People must check prior to compile and must remove or Change parts of there software. In the moment,in the case of a missing accompanying Fortran Compiler, an application or middleware that wants to handle MPI Fortran datatypes must handle both cases (1) mpi.h does not provide a specific MPI Fortran datatype (2) mpi.h provides this MPI Fortran datatype as MPI_DATATYPE_NULL The additional case, that it is mapped to a real datatype is not an exception, because it defines some sort of accompanying Fortran Compiler. I would prefer that the MPI standard defines, which of the two options should be implemented. As said at the beginning, I would prefer (1), - as mpich is doing it in general, and - OMPI is doing it partially, whereas (2) was not done by mpich nor by OMPI. The MPI Forum may do a straw vote on that. Best regards Rolf ----- Original Message -----
From: "Jeff Squyres" <[email protected]> To: "MPI-WG Fortran working group" <[email protected]> Sent: Thursday, February 18, 2016 7:42:05 PM Subject: Re: [MPIWG Fortran] Provide Fortran datatypes if Fortran bindings not provided?
On Feb 18, 2016, at 1:31 PM, Jeff Hammond <[email protected]> wrote:
Please tell me why we want to do something different for Fortran.
Seems to be a good point. What is mpich doing if there is no accompanying Fortran compiler?
Full mpi.h from my Clang MPICH builds with FC=false attached. Relevant excerpt below. /* Fortran types */
#define MPI_COMPLEX ((MPI_Datatype)MPI_DATATYPE_NULL)
It looks like OMPI does a mix of setting some Fortran datatypes to (effectively) MPI_DATATYPE_NULL and others to what we guess/assume they should be equivalent to (e.g., MPI_INTEGER --> MPI_INT).
Middleware that compiles but cannot be used in any nontrivial way because MPI_DATATYPE_NULL may (at least with Open-MPI) cause the program to abort. I don't see a problem in breaking compilation when successful compilation today leads to unsuccessful execution.
+1
-- Jeff Squyres [email protected] For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
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