mpi4py


Introduction:

MPI4PY is a package that enables Python programs to run
in parallel under MPI.

MPI4PY provides an interface designed on translating MPI syntax and
semantics from standard MPI-2 C++ bindings to Python. As syntax
translation from C++ to Python is generally straightforward, any user
with some knowledge of those C++ bindings should be able to use this
package without learning a new interface.

Web site:

The home page “MPI for Python” at pythonhosted.org:

http://pythonhosted.org/mpi4py/

Reference:

  • Lisandro Dalcin, Rodrigo Paz, Mario Storti,
    MPI for Python,
    Journal of Parallel and Distributed Computing,
    Volume 65, pages 1108-1115, 2005.

Usage:

ARC has not installed MPI4PY on any of its clusters. However, it is
possible for a user to install MPI4PY, and then to use it in the usual way.

Example User Installation on NewRiver:

In this example, the user PID has decided to create a subdirectory
tfcascades into which to install TENSORFLOW. The user PID
should log in interactively to NewRiver and issue the following commands:

      module purge
      module load gcc/5.2.0
      module load openmpi/1.8.5
      module load Anaconda/2.3.0

      export PYTHONUSERBASE=/home/PID/newriver/python

      pip install --user mpi4py
    

Example Usage on NewRiver:

We assume MPI4PY has been installed as in the above example.
A simple test code might be the following “hello_mpi.py”:

def hello_mpi ( ):

  import sys
  from mpi4py import MPI

  comm = MPI.COMM_WORLD

  id = comm.Get_rank()

  p = comm.Get_size()

  if ( id == 0 ):
    print ""
    print "HELLO_MPI:"
    print "  P", id, ":  There are ", p, " MPI processes running."

  print "  P", id, ":  Hello, world!"

Then a typical batch job to run the code under MPI4PY might be:

#! /bin/bash
#
#PBS -l walltime=00:05:00
#PBS -l nodes=1:ppn=4
#PBS -W group_list=newriver
#PBS -q open_q
#PBS -j oe
#
cd $PBS_O_WORKDIR
#
module purge
module load gcc/5.2.0
module load Anaconda/2.3.0
module load openmpi/1.8.5
#
export PYTHONUSERBASE=/home/burkardt/newriver/python
#
mpirun -np 4 python hello_mpi.py
    

A complete set of files to carry out a similar process are available in
mpi4py_example.tar