[Mpi-forum] overloading MPI_Init etc.

[Fab Tillier]

I don't think defining one's own mpi.h is an issue from a compliance perspective.  However, overloading MPI_Init definitely is - the standard reserves the MPI_ namespace, so if it isn't in the standard, it's not standard compliant.  Now, if they named it MyMPI_Init, it'd be fine.

-Fab

Jeff Hammond wrote on Sun, 4 Mar 2012 at 18:22:40

> I have a user who insists it is MPI-compliant to do the following:
> 
> user file mpi.h, which is included in the application with #include
> "mpi.h": ================================== #include <mpi.h>
> 
> <snip>
> 
> void MPI_Init(int argc, char* argv[], int& my_rank, int& mpi_size, int&
> Master) {
>   MPI::Init(argc, argv);
>   my_rank = MPI::COMM_WORLD.Get_rank();
>   mpi_size = MPI::COMM_WORLD.Get_size();
>   Master = 0;
>   
>   std::cout << "Hello World! I am " << my_rank << " of " << mpi_size
> << std::endl;
> }
> 
> void MPI_finalize()
> {MPI::Finalize();}
> 
> ==================================
> 
> I believe that it is a terrible practice, if not a violation of the
> MPI standard to:
> (1) define one's own mpi.h, since this may confuse the preprocessor
> (or are there precedence rules in the ANSI C standard?) as to which to
> include first (especially if CC=mpicc or CXX=mpicxx), and
> (2) overload MPI_Init, even if one is using C++ and relying upon C++
> name-mangling to avoid a symbol conflict.
> 
> The user believes that the inability to overload MPI_Init in C++ means
> that MPI is not compliant with the C++ standard.
> 
> Thanks,
> 
> Jeff
>