Development

Prerequisites

You need to have the following software properly installed in order to build MPI for Python:

  • Python 3.6 or above.

  • The Cython compiler.

  • A working MPI implementation like MPICH or Open MPI, preferably supporting MPI-4 and built with shared/dynamic libraries.

    Note

    If you want to build some MPI implementation from sources, check the instructions at Building MPI from sources in the appendix.

    Note

    Some MPI-1 implementations do require the actual command line arguments to be passed in MPI_Init(). In this case, you will need to use a rebuilt, MPI-enabled, Python interpreter executable. MPI for Python has some support for alleviating you from this task. Check the instructions at MPI-enabled Python interpreter in the appendix.

Optionally, consider installing the following packages:

  • NumPy for enabling comprehensive testing of MPI communication.

  • CuPy for enabling comprehensive testing with a GPU-aware MPI.

  • Sphinx to build documentation.

Building

MPI for Python uses setuptools-based build system that relies on the setup.py file. Some setuptools commands (e.g., build) accept additional options:

--mpi=

Lets you pass a section with MPI configuration within a special configuration file. Alternatively, you can use the MPICFG environment variable.

--mpicc=

Specify the path or name of the mpicc C compiler wrapper. Alternatively, use the MPICC environment variable.

--mpild=

Specify the full path or name for the MPI-aware C linker. Alternatively, use the MPILD environment variable. If not set, the mpicc C compiler wrapper is used for linking.

--configure

Runs exhaustive tests for checking about missing MPI types, constants, and functions. This option should be passed in order to build MPI for Python against old MPI-1, MPI-2, or MPI-3 implementations, possibly providing a subset of MPI-4.

If you use a MPI implementation providing a mpicc C compiler wrapper (e.g., MPICH or Open MPI), it will be used for compilation and linking. This is the preferred and easiest way to build MPI for Python.

If mpicc is found in the executable search path (PATH environment variable), simply run the build command:

$ python setup.py build

If mpicc is not in your search path or the compiler wrapper has a different name, you can run the build command specifying its location, either via the --mpicc command option or using the MPICC environment variable:

$ python setup.py build --mpicc=/path/to/mpicc
$ MPICC=/path/to/mpicc python setup.py build

Alternatively, you can provide all the relevant information about your MPI implementation by editing the mpi.cfg file located in the top level source directory. You can use the default section [mpi] or add a new custom section, for example [other_mpi] (see the examples provided in the mpi.cfg file as a starting point to write your own section):

[mpi]
include_dirs         = /usr/local/mpi/include
libraries            = mpi
library_dirs         = /usr/local/mpi/lib
runtime_library_dirs = /usr/local/mpi/lib

[other_mpi]
include_dirs         = /opt/mpi/include ...
libraries            = mpi ...
library_dirs         = /opt/mpi/lib ...
runtime_library_dirs = /opt/mpi/lib ...

...

and then run the build command specifying you custom configuration section:

$ python setup.py build --mpi=other_mpi
$ MPICFG=other_mpi python setup.py build

After building, the package is ready for installation in development mode:

$ python setup.py develop --user

Alternatively, you can generate a binary wheel file in the dist/ directory with:

$ python setup.py bdist_wheel

Testing

To quickly test the installation:

$ mpiexec -n 5 python -m mpi4py.bench helloworld
Hello, World! I am process 0 of 5 on localhost.
Hello, World! I am process 1 of 5 on localhost.
Hello, World! I am process 2 of 5 on localhost.
Hello, World! I am process 3 of 5 on localhost.
Hello, World! I am process 4 of 5 on localhost.

$ mpiexec -n 5 python -m mpi4py.bench ringtest -l 10 -n 1048576
time for 10 loops = 0.00361614 seconds (5 processes, 1048576 bytes)

If you installed from a git clone or the source distribution, issuing at the command line:

$ mpiexec -n 5 python demo/helloworld.py

will launch a five-process run of the Python interpreter and run the test script demo/helloworld.py from the source distribution.

You can also run all the unittest scripts:

$ mpiexec -n 5 python test/runtests.py

or, if you have nose unit testing framework installed:

$ mpiexec -n 5 nosetests

or, if you have py.test unit testing framework installed:

$ mpiexec -n 5 py.test