Using MPI on Iridis

Implementations of MPI on Iridis

MPICH 1.2.6 with the PGI compilers is installed in /local/mpich-pgi. Alternatively a version using the Gnu compilers is installed in /local/mpich-1.2.6.
Important Note: To use the MPICH versions you must either specify the full path to the compiler wrapper, eg. /local/mpich-pgi/bin/mpif90 or modify your default path so that the MPICH bin directory precedes /usr/bin. The unqualified use of these commands will normally pick up a LAM version using the gnu compilers which comes bundled with the O/S and is in /usr/bin on the default path. The use of this version has not been fully tested at present and its use is not recommended. A LAM version using the PGI compilers may be added later, but for the moment MPICH 1.2.6 is the only supported version of MPI.

Compiling for MPI

When compiling MPI codes it is recommended to use the appropriate wrapper for the compilers to ensure that the correct libraries and include files are selected. These are mpif77 or mpif90 for Fortran and mpicc and mpicxx for C and C++. As noted above, to use the MPICH versions you must either specify the full path to the compiler wrapper, eg. /local/mpich-pgi/bin/mpif90 or modify your default path so that the MPICH bin directory precedes /usr/bin.

Compiling MPI codes without wrapper scripts

Some packages may have makefiles which require the path to MPI include files, and the MPI libraries to be linked, to be declared explicitly. Both MPICH and MPICH_GM provide assistance to indicate the required flags. The use of the -compile_info and -link_info flags with the appropriate wrapper script indicates the compiler flags and linking options required for correct operation of the MPICH routines. e.g. /local/mpich-pgi/bin/mpif90 -compile_info

gives the compiler options required to include the MPI include files in MPICH using pgf90.

/local/mpich-1.2.6/bin/mpicc -link_info

gives the compiler options required to link the MPI libraries for MPICH using gcc.

Running MPI Jobs

  • Submitting jobs, general information..... Details
  • Submitting MPI jobs..... Details Further Information

MPI

  • The MPI standards documents are available via the MPI Forum home page.
  • The book MPI: A Complete Reference is available online and has a good discussion of many of the finer points of using MPI.

MPICH

  • The best source of information is the MPICH user documentation which can be found at /local/mpich-pgi/doc/ or online page (there are now separate versions for each MPICH device, the ch_p4 version is probably appropriate for most people).
  • Information on MPICH commands can be found from the man pages for mpirun, mpif77 etc. These are not currently on the standard MANPATH, so if you want to view the MPICH versions you will need to use the -M flag to man to specify the full path to the MPICH man pages, eg. man -M /local/mpich-pgi/man mpirun These are not always fully up to date ....
  • For further information see the MPICH home page.