Appendix¶
MPI-enabled Python interpreter¶
Warning
These days it is no longer required to use the MPI-enabled Python interpreter in most cases, and, therefore, is not built by default anymore because it is too difficult to reliably build a Python interpreter across different distributions. If you know that you still really need it, see below on how to use the build_exe and install_exe commands.
Some MPI-1 implementations (notably, MPICH 1) do require the
actual command line arguments to be passed at the time
MPI_Init()
is called. In this case, you will need to use a
re-built, MPI-enabled, Python interpreter binary executable. A basic
implementation (targeting Python 2.X) of what is required is shown
below:
#include <Python.h>
#include <mpi.h>
int main(int argc, char *argv[])
{
int status, flag;
MPI_Init(&argc, &argv);
status = Py_Main(argc, argv);
MPI_Finalized(&flag);
if (!flag) MPI_Finalize();
return status;
}
The source code above is straightforward; compiling it should also be. However, the linking step is more tricky: special flags have to be passed to the linker depending on your platform. In order to alleviate you for such low-level details, MPI for Python provides some pure-distutils based support to build and install an MPI-enabled Python interpreter executable:
$ cd mpi4py-X.X.X
$ python setup.py build_exe [--mpi=<name>|--mpicc=/path/to/mpicc]
$ [sudo] python setup.py install_exe [--install-dir=$HOME/bin]
After the above steps you should have the MPI-enabled interpreter
installed as prefix/bin/pythonX.X-mpi
(or
$HOME/bin/pythonX.X-mpi
). Assuming that
prefix/bin
(or $HOME/bin
) is listed on your
PATH
, you should be able to enter your MPI-enabled Python
interactively, for example:
$ python2.7-mpi
Python 2.7.8 (default, Nov 10 2014, 08:19:18)
[GCC 4.9.2 20141101 (Red Hat 4.9.2-1)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.executable
'/usr/bin/python2.7-mpi'
>>>
Building MPI from sources¶
In the list below you have some executive instructions for building some of the open-source MPI implementations out there with support for shared/dynamic libraries on POSIX environments.
MPICH
$ tar -zxf mpich-X.X.X.tar.gz $ cd mpich-X.X.X $ ./configure --enable-shared --prefix=/usr/local/mpich $ make $ make install
Open MPI
$ tar -zxf openmpi-X.X.X tar.gz $ cd openmpi-X.X.X $ ./configure --prefix=/usr/local/openmpi $ make all $ make install
MPICH 1
$ tar -zxf mpich-X.X.X.tar.gz $ cd mpich-X.X.X $ ./configure --enable-sharedlib --prefix=/usr/local/mpich1 $ make $ make install
Perhaps you will need to set the LD_LIBRARY_PATH
environment variable (using export, setenv or
what applies to your system) pointing to the directory containing the
MPI libraries . In case of getting runtime linking errors when running
MPI programs, the following lines can be added to the user login shell
script (.profile
, .bashrc
, etc.).
MPICH
MPI_DIR=/usr/local/mpich export LD_LIBRARY_PATH=$MPI_DIR/lib:$LD_LIBRARY_PATH
Open MPI
MPI_DIR=/usr/local/openmpi export LD_LIBRARY_PATH=$MPI_DIR/lib:$LD_LIBRARY_PATH
MPICH 1
MPI_DIR=/usr/local/mpich1 export LD_LIBRARY_PATH=$MPI_DIR/lib/shared:$LD_LIBRARY_PATH: export MPICH_USE_SHLIB=yes
Warning
MPICH 1 support for dynamic libraries is not completely transparent. Users should set the environment variable
MPICH_USE_SHLIB
toyes
in order to avoid link problems when using the mpicc compiler wrapper.