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<div class="section" id="appendix">
<h1>Appendix<a class="headerlink" href="#appendix" title="Permalink to this headline">¶</a></h1>
<div class="section" id="mpi-enabled-python-interpreter">
<span id="python-mpi"></span><h2>MPI-enabled Python interpreter<a class="headerlink" href="#mpi-enabled-python-interpreter" title="Permalink to this headline">¶</a></h2>
<p>Some MPI-1 implementations (notably, MPICH 1) <strong>do require</strong> the
actual command line arguments to be passed at the time
<tt class="xref docutils literal"><span class="pre">MPI_Init()</span></tt> 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:</p>
<div class="highlight-c"><div class="highlight"><pre><span class="cp">#include <Python.h></span>
<span class="cp">#include <mpi.h></span>
<span class="kt">int</span> <span class="nf">main</span><span class="p">(</span><span class="kt">int</span> <span class="n">argc</span><span class="p">,</span> <span class="kt">char</span> <span class="o">*</span><span class="n">argv</span><span class="p">[])</span>
<span class="p">{</span>
<span class="kt">int</span> <span class="n">status</span><span class="p">,</span> <span class="n">flag</span><span class="p">;</span>
<span class="n">MPI_Init</span><span class="p">(</span><span class="o">&</span><span class="n">argc</span><span class="p">,</span> <span class="o">&</span><span class="n">argv</span><span class="p">);</span>
<span class="n">status</span> <span class="o">=</span> <span class="n">Py_Main</span><span class="p">(</span><span class="n">argc</span><span class="p">,</span> <span class="n">argv</span><span class="p">);</span>
<span class="n">MPI_Finalized</span><span class="p">(</span><span class="o">&</span><span class="n">flag</span><span class="p">);</span>
<span class="k">if</span> <span class="p">(</span><span class="o">!</span><span class="n">flag</span><span class="p">)</span> <span class="n">MPI_Finalize</span><span class="p">();</span>
<span class="k">return</span> <span class="n">status</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
<p>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, <em>MPI for Python</em> provides some
pure-distutils based support to build and install an MPI-enabled
Python interpreter executable:</p>
<div class="highlight-python"><pre>$ cd mpi4py-X.X.X
$ python setup.py build_exe [--mpi=<name>|--mpicc=/path/to/mpicc]
$ [sudo] python setup.py install_exe [--install-dir=$HOME/bin]</pre>
</div>
<p>After the above steps you should have the MPI-enabled interpreter
installed as <tt class="docutils literal"><em><span class="pre">prefix</span></em><span class="pre">/bin/python</span><em><span class="pre">X</span></em><span class="pre">.</span><em><span class="pre">X</span></em><span class="pre">-mpi</span></tt> (or
<tt class="docutils literal"><span class="pre">$HOME/bin/python</span><em><span class="pre">X</span></em><span class="pre">.</span><em><span class="pre">X</span></em><span class="pre">-mpi</span></tt>). Assuming that
<tt class="docutils literal"><em><span class="pre">prefix</span></em><span class="pre">/bin</span></tt> (or <tt class="docutils literal"><span class="pre">$HOME/bin</span></tt>) is listed on your
<span class="target" id="index-0"></span><strong class="xref">PATH</strong>, you should be able to enter your MPI-enabled Python
interactively, for example:</p>
<div class="highlight-python"><pre>$ python2.6-mpi
Python 2.6 (r26:66714, Jun 8 2009, 16:07:26)
[GCC 4.4.0 20090506 (Red Hat 4.4.0-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.executable
'/usr/bin/python2.6-mpi'
>>></pre>
</div>
</div>
<div class="section" id="mac-os-x-and-universal-sdk-python-builds">
<span id="macosx-universal-sdk"></span><h2>Mac OS X and Universal/SDK Python builds<a class="headerlink" href="#mac-os-x-and-universal-sdk-python-builds" title="Permalink to this headline">¶</a></h2>
<p>Mac OS X users employing a Python distribution built with support for
<a class="reference external" href="http://www.apple.com/universal/">Universal applications</a> could have
trouble building <em>MPI for Python</em>, 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 <em>deployment target</em>
and <em>cross-development SDK</em> configuration. Workarounds for such issues
are to temporarily set the environment variables
<span class="target" id="index-1"></span><strong class="xref">MACOSX_DEPLOYMENT_TARGET</strong>, <span class="target" id="index-2"></span><strong class="xref">SDKROOT</strong> and/or
<span class="target" id="index-3"></span><strong class="xref">ARCHFLAGS</strong> to appropriate values in the shell before trying
to build/install <em>MPI for Python</em>.</p>
<p>An appropriate value for <span class="target" id="index-4"></span><strong class="xref">MACOSX_DEPLOYMENT_TARGET</strong> 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 <em>Leopard</em>, you should
try <tt class="docutils literal"><span class="pre">MACOSX_DEPLOYMENT_TARGET=10.5</span></tt>).</p>
<p>An appropriate value for <span class="target" id="index-5"></span><strong class="xref">SDKROOT</strong> is the full path name of
any of the SDK’s you have at <tt class="docutils literal"><span class="pre">/Developer/SDKs</span></tt> directory (e.g.,
<tt class="docutils literal"><span class="pre">SDKROOT=/Developer/SDKs/MacOSX10.5.sdk</span></tt>). The safest choice for
end-users would be the one matching the system version; or
alternatively the root directory (i.e., <tt class="docutils literal"><span class="pre">SDKROOT=/</span></tt>).</p>
<p>Appropriate values for <span class="target" id="index-6"></span><strong class="xref">ARCHFLAGS</strong> have the form <tt class="docutils literal"><span class="pre">-arch</span>
<span class="pre"><value></span></tt>, where <tt class="docutils literal"><span class="pre"><value></span></tt> should be chosen from the following
table:</p>
<table border="1" class="docutils">
<colgroup>
<col width="24%" />
<col width="40%" />
<col width="36%" />
</colgroup>
<thead valign="bottom">
<tr><th class="head">@</th>
<th class="head">Intel</th>
<th class="head">PowerPC</th>
</tr>
</thead>
<tbody valign="top">
<tr><td>32-bit</td>
<td><tt class="docutils literal"><span class="pre">i386</span></tt></td>
<td><tt class="docutils literal"><span class="pre">ppc</span></tt></td>
</tr>
<tr><td>64-bit</td>
<td><tt class="docutils literal"><span class="pre">x86_64</span></tt></td>
<td><tt class="docutils literal"><span class="pre">ppc64</span></tt></td>
</tr>
</tbody>
</table>
<p>For example, assuming your Mac is running <strong>Snow Leopard</strong> on a
<strong>64-bit Intel</strong> processor and you want to override the hard-wired
cross-development SDK in Python configuration, you can build and
install <em>MPI for Python</em> using any of the alternatives below. Note
that environment variables may need to be passed/set both at the build
and install steps (because <strong>sudo</strong> may not pass environment
variables to subprocesses for security reasons)</p>
<ul>
<li><p class="first">Alternative 1:</p>
<div class="highlight-python"><pre>$ 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]</pre>
</div>
</li>
<li><p class="first">Alternative 2:</p>
<div class="highlight-python"><pre>$ 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</pre>
</div>
</li>
</ul>
</div>
<div class="section" id="building-mpi-from-sources">
<span id="building-mpi"></span><h2>Building MPI from sources<a class="headerlink" href="#building-mpi-from-sources" title="Permalink to this headline">¶</a></h2>
<p>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.</p>
<ul>
<li><p class="first"><em>MPICH 2</em></p>
<div class="highlight-python"><pre>$ tar -zxf mpich2-X.X.X.tar.gz
$ cd mpich2-X.X.X
$ ./configure --enable-sharedlibs=gcc --prefix=/usr/local/mpich2
$ make
$ make install</pre>
</div>
</li>
<li><p class="first"><em>Open MPI</em></p>
<div class="highlight-python"><pre>$ tar -zxf openmpi-X.X.X tar.gz
$ cd openmpi-X.X.X
$ ./configure --prefix=/usr/local/openmpi
$ make all
$ make install</pre>
</div>
</li>
<li><p class="first"><em>LAM/MPI</em></p>
<div class="highlight-python"><pre>$ tar -zxf lam-X.X.X.tar.gz
$ cd lam-X.X.X
$ ./configure --enable-shared --prefix=/usr/local/lam
$ make
$ make install</pre>
</div>
</li>
<li><p class="first"><em>MPICH 1</em></p>
<div class="highlight-python"><pre>$ tar -zxf mpich-X.X.X.tar.gz
$ cd mpich-X.X.X
$ ./configure --enable-sharedlib --prefix=/usr/local/mpich1
$ make
$ make install</pre>
</div>
</li>
</ul>
<p>Perhaps you will need to set the <span class="target" id="index-7"></span><strong class="xref">LD_LIBRARY_PATH</strong>
environment variable (using <strong>export</strong>, <strong>setenv</strong> 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 (<tt class="docutils literal"><span class="pre">.profile</span></tt>, <tt class="docutils literal"><span class="pre">.bashrc</span></tt>, etc.).</p>
<ul>
<li><p class="first"><em>MPICH 2</em></p>
<div class="highlight-python"><pre>MPI_DIR=/usr/local/mpich2
export LD_LIBRARY_PATH=$MPI_DIR/lib:$LD_LIBRARY_PATH</pre>
</div>
</li>
<li><p class="first"><em>Open MPI</em></p>
<div class="highlight-python"><pre>MPI_DIR=/usr/local/openmpi
export LD_LIBRARY_PATH=$MPI_DIR/lib:$LD_LIBRARY_PATH</pre>
</div>
</li>
<li><p class="first"><em>LAM/MPI</em></p>
<div class="highlight-python"><pre>MPI_DIR=/usr/local/lam
export LD_LIBRARY_PATH=$MPI_DIR/lib:$LD_LIBRARY_PATH</pre>
</div>
</li>
<li><p class="first"><em>MPICH 1</em></p>
<div class="highlight-python"><pre>MPI_DIR=/usr/local/mpich1
export LD_LIBRARY_PATH=$MPI_DIR/lib/shared:$LD_LIBRARY_PATH:
export MPICH_USE_SHLIB=yes</pre>
</div>
<div class="admonition warning">
<p class="first admonition-title">Warning</p>
<p class="last">MPICH 1 support for dynamic libraries is not completely
transparent. Users should set the environment variable
<span class="target" id="index-8"></span><strong class="xref">MPICH_USE_SHLIB</strong> to <tt class="docutils literal"><span class="pre">yes</span></tt> in order to avoid link
problems when using the <strong>mpicc</strong> compiler wrapper.</p>
</div>
</li>
</ul>
</div>
</div>
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<li><a class="reference external" href="#">Appendix</a><ul>
<li><a class="reference external" href="#mpi-enabled-python-interpreter">MPI-enabled Python interpreter</a></li>
<li><a class="reference external" href="#mac-os-x-and-universal-sdk-python-builds">Mac OS X and Universal/SDK Python builds</a></li>
<li><a class="reference external" href="#building-mpi-from-sources">Building MPI from sources</a></li>
</ul>
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