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<title>Speed &mdash; pythonguide 0.0.1 documentation</title>
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<div class="section" id="speed">
<h1>Speed<a class="headerlink" href="#speed" title="Permalink to this headline"></a></h1>
<p>CPython, the most commonly used implementation of Python, is slow for CPU bound tasks. <a class="reference external" href="http://pypy.org">PyPy</a> is fast.</p>
<p>Using a slightly modified version of <a class="reference external" href="http://www.dabeaz.com/GIL/gilvis/measure2.py">David Beazleys</a> CPU bound test code(added loop for multiple tests), you can see the difference between CPython and PyPy&#8217;s processing.</p>
<div class="highlight-python"><pre>PyPy
$ ./pypy -V
Python 2.7.1 (7773f8fc4223, Nov 18 2011, 18:47:10)
[PyPy 1.7.0 with GCC 4.4.3]
$ ./pypy measure2.py
0.0683999061584
0.0483210086823
0.0388588905334
0.0440690517426
0.0695300102234</pre>
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<div class="highlight-python"><pre>CPython
$ ./python -V
Python 2.7.1
$ ./python measure2.py
1.06774401665
1.45412397385
1.51485204697
1.54693889618
1.60109114647</pre>
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<div class="section" id="context">
<h2>Context<a class="headerlink" href="#context" title="Permalink to this headline"></a></h2>
<div class="section" id="the-gil">
<h3>The GIL<a class="headerlink" href="#the-gil" title="Permalink to this headline"></a></h3>
<p><a class="reference external" href="http://wiki.python.org/moin/GlobalInterpreterLock">The GIL</a> (Global Interpreter Lock) is how Python allows multiple threads to operate at the same time. Python&#8217;s
memory management isn&#8217;t entirely thread-safe, so the GIL is requried to prevents multiple threads from running
the same Python code at once.</p>
<p>David Beazley has a great <a class="reference external" href="http://www.dabeaz.com/python/UnderstandingGIL.pdf">guide</a> on how the GIL operates. He also covers the <a class="reference external" href="http://www.dabeaz.com/python/NewGIL.pdf">new GIL</a> in Python 3.2. His
results show that maximizing performance in a Python application requires a strong understanding of the GIL,
how it affects your specific application, how many cores you have, and where your application bottlenecks are.</p>
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<h3>C Extentions<a class="headerlink" href="#c-extentions" title="Permalink to this headline"></a></h3>
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<div class="section" id="id1">
<h3>The GIL<a class="headerlink" href="#id1" title="Permalink to this headline"></a></h3>
<p><a class="reference external" href="http://docs.python.org/c-api/init.html#threads">Special care</a> must be taken when writing C extensions to make sure you register your threads
with the interpreter.</p>
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<div class="section" id="id2">
<h2>C Extentions<a class="headerlink" href="#id2" title="Permalink to this headline"></a></h2>
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<h3>Cython<a class="headerlink" href="#cython" title="Permalink to this headline"></a></h3>
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<h3>Pyrex<a class="headerlink" href="#pyrex" title="Permalink to this headline"></a></h3>
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<h3>Shedskin?<a class="headerlink" href="#shedskin" title="Permalink to this headline"></a></h3>
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<h2>Threading<a class="headerlink" href="#threading" title="Permalink to this headline"></a></h2>
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<h3>Threading<a class="headerlink" href="#id3" title="Permalink to this headline"></a></h3>
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<h3>Spanwing Processes<a class="headerlink" href="#spanwing-processes" title="Permalink to this headline"></a></h3>
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<h3>Multiprocessing<a class="headerlink" href="#multiprocessing" title="Permalink to this headline"></a></h3>
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<div class="sphinxsidebarwrapper"><h3><a href="http://python-guide.org">Python Guide</a></h3>
<p>
This opinionated guide exists to provide both novice and expert Python developers a best-practice handbook to the installation, configuration, and usage of Python on a daily basis.
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<h3><a href="../index.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Speed</a><ul>
<li><a class="reference internal" href="#context">Context</a><ul>
<li><a class="reference internal" href="#the-gil">The GIL</a></li>
<li><a class="reference internal" href="#c-extentions">C Extentions</a></li>
<li><a class="reference internal" href="#id1">The GIL</a></li>
</ul>
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<li><a class="reference internal" href="#id2">C Extentions</a><ul>
<li><a class="reference internal" href="#cython">Cython</a></li>
<li><a class="reference internal" href="#pyrex">Pyrex</a></li>
<li><a class="reference internal" href="#shedskin">Shedskin?</a></li>
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<li><a class="reference internal" href="#spanwing-processes">Spanwing Processes</a></li>
<li><a class="reference internal" href="#multiprocessing">Multiprocessing</a></li>
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<li>Previous: <a href="ci.html" title="previous chapter">Continuous Integration</a></li>
<li>Next: <a href="scientific.html" title="next chapter">Scientific Applications</a></li>
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&copy; Copyright 2012. A <a href="http://kennethreitz.com/pages/open-projects.html">Kenneth Reitz</a> Project. <a href="http://creativecommons.org/licenses/by-sa/3.0/"> Creative Commons Share-Alike 3.0</a>..
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