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Appendix
========
.. _python-mpi:
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
:c:func:`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:
.. sourcecode:: c
#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=$HOME/bin]
After the above steps you should have the MPI-enabled interpreter
installed as :file:`{prefix}/bin/python{X}.{X}-mpi` (or
:file:`$HOME/bin/python{X}.{X}-mpi`). Assuming that
:file:`{prefix}/bin` (or :file:`$HOME/bin`) is listed on your
:envvar:`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'
>>>
.. _macosx-universal-sdk:
Mac OS X and Universal/SDK Python builds
----------------------------------------
Mac OS X users employing a Python distribution built with support for
`Universal applications <http://www.apple.com/universal/>`_ could have
trouble building *MPI for Python*, specially if they want to link
against MPI libraries built without such support. Another source of
trouble could be a Python build using a specific *deployment target*
and *cross-development SDK* configuration. Workarounds for such issues
are to temporarily set the environment variables
:envvar:`MACOSX_DEPLOYMENT_TARGET`, :envvar:`SDKROOT` and/or
:envvar:`ARCHFLAGS` to appropriate values in the shell before trying
to build/install *MPI for Python*.
An appropriate value for :envvar:`MACOSX_DEPLOYMENT_TARGET` should be
any greater or equal than the one used to build Python, and less or
equal than your system version. The safest choice for end-users would
be to use the system version (e.g, if you are on *Leopard*, you should
try ``MACOSX_DEPLOYMENT_TARGET=10.5``).
An appropriate value for :envvar:`SDKROOT` is the full path name of
any of the SDK's you have at :file:`/Developer/SDKs` directory (e.g.,
``SDKROOT=/Developer/SDKs/MacOSX10.5.sdk``). The safest choice for
end-users would be the one matching the system version; or
alternatively the root directory (i.e., ``SDKROOT=/``).
Appropriate values for :envvar:`ARCHFLAGS` have the form ``-arch
<value>``, where ``<value>`` should be chosen from the following
table:
====== ========== =========
@ Intel PowerPC
====== ========== =========
32-bit ``i386`` ``ppc``
64-bit ``x86_64`` ``ppc64``
====== ========== =========
For example, assuming your Mac is running **Snow Leopard** on a
**64-bit Intel** processor and you want to override the hard-wired
cross-development SDK in Python configuration, you can build and
install *MPI for Python* using any of the alternatives below. Note
that environment variables may need to be passed/set both at the build
and install steps (because :program:`sudo` may not pass environment
variables to subprocesses for security reasons)
* Alternative 1::
$ env MACOSX_DEPLOYMENT_TARGET=10.6 \
SDKROOT=/ \
ARCHFLAGS='-arch x86_64' \
python setup.py build [options]
$ sudo env MACOSX_DEPLOYMENT_TARGET=10.6 \
SDKROOT=/ \
ARCHFLAGS='-arch x86_64' \
python setup.py install [options]
* Alternative 2::
$ export MACOSX_DEPLOYMENT_TARGET=10.6
$ export SDKROOT=/
$ export ARCHFLAGS='-arch x86_64'
$ python setup.py build [options]
$ sudo -s # enter interactive shell as root
$ export MACOSX_DEPLOYMENT_TARGET=10.6
$ export SDKROOT=/
$ export ARCHFLAGS='-arch x86_64'
$ python setup.py install [options]
$ exit
.. _building-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
+ *LAM/MPI* ::
$ tar -zxf lam-X.X.X.tar.gz
$ cd lam-X.X.X
$ ./configure --enable-shared --prefix=/usr/local/lam
$ make
$ 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 :envvar:`LD_LIBRARY_PATH`
environment variable (using :command:`export`, :command:`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 (:file:`.profile`, :file:`.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
- *LAM/MPI* ::
MPI_DIR=/usr/local/lam
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
:envvar:`MPICH_USE_SHLIB` to ``yes`` in order to avoid link
problems when using the :program:`mpicc` compiler wrapper.
|
