Question

I have a code that has some mpi api-dependent bits:

#if MPIVERSION==1
...
#elif MPIVERSION==2
...
#endif

that switches between assuming MPI-1 and MPI-2.

Is there a good way to infer a good version — particularly one that might go in the build system?

Thanks!

Answer 1

Do what configure scripts usually do – try to compile and run a very simple test MPI code that consists of:

#include <stdio.h>
#include <mpi.h>

int main (void)
{
    int version, subversion;
    MPI_Get_version(&version, &subversion);
    printf("%d.%d\n", version, subversion);
    return 0;
}

Compile this code with mpicc (or whatever compiler was specified) and run it (directly and not through mpirun) during code configuration time and you will both:

• know that the MPI compiler wrapper actually works
• get the supported MPI standard major and minor versions

You can do the same for Fortran projects.

You can also try to parse mpi.h directly and search for MPI_VERSION and MPI_SUBVERSION but you might run into some non-portability issues. Besides those macros are meant to be used for conditional compilation inside the C/C++ code.