.. _mpi_osx:

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Installing MPI on a Mac
=============================================================

On a Mac you might get the following error::

    $ mpif90 pisum1.f90
    --------------------------------------------------------------------------
    Unfortunately, this installation of Open MPI was not compiled with
    Fortran 90 support.  As such, the mpif90 compiler is non-functional.
    --------------------------------------------------------------------------

This indicates that the Mac has a version of MPI, but not one that works
with Fortran 90.

To fix this, see
`<http://www.macresearch.org/compiling-mpi-f90-support-snow-leopard>`_.

Kyle Mandli suggests the following modifications to what's there:

 #. All of the compilers in the flags are intel compilers, you need to switch
    them to the corresponding gcc compilers such as ::

        CXX=g++ CC=gcc F77=gfortran F90=gfortran FC=gfortran

    although I would be surprised if the configure script does not figure this
    out for itself.

 #. I might also suggest using a different prefix than /opt/openmpi
    (something more sensible would be /usr/local).  If you use the /usr/local
    prefix you should not have to set all the paths.

 #. The --with-xgrid flag is not installed by default with OpenMPI so you can
    skip that flag as well.