Merge pull request #73 from rday/master

Speed file updates

docs/scenarios/speed.rst

@@ -3,7 +3,32 @@ Speed
 
 CPython, the most commonly used implementation of Python, is slow for CPU bound tasks. `PyPy`_ is fast.
 
-.. todo:: Fill in stub for Speed comparisons
+Using a slightly modified version of `David Beazleys`_ CPU bound test code(added loop for multiple tests), you can see the difference between CPython and PyPy's processing.
+
+::
+
+   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
+
+::
+
+   CPython
+   $ ./python -V
+   Python 2.7.1
+   $ ./python measure2.py 
+   1.06774401665
+   1.45412397385
+   1.51485204697
+   1.54693889618
+   1.60109114647
 
 Context
 :::::::
@@ -12,7 +37,13 @@ Context
 The GIL
 -------
 
+`The GIL`_ (Global Interpreter Lock) is how Python allows multiple threads to operate at the same time. Python's
+memory management isn't entirely thread-safe, so the GIL is requried to prevents multiple threads from running
+the same Python code at once.
 
+David Beazley has a great `guide`_ on how the GIL operates. He also covers the `new GIL`_ 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.
 
 C Extentions
 ------------
@@ -21,8 +52,8 @@ C Extentions
 The GIL
 -------
 
-
-
+`Special care`_ must be taken when writing C extensions to make sure you register your threads
+with the interpreter.
 
 C Extentions
 ::::::::::::
@@ -57,4 +88,9 @@ Multiprocessing
 ---------------
 
 
-.. _`PyPy`: http://pypy.org
+.. _`PyPy`: http://pypy.org
+.. _`The GIL`: http://wiki.python.org/moin/GlobalInterpreterLock
+.. _`guide`: http://www.dabeaz.com/python/UnderstandingGIL.pdf
+.. _`New GIL`: http://www.dabeaz.com/python/NewGIL.pdf
+.. _`Special care`: http://docs.python.org/c-api/init.html#threads
+.. _`David Beazleys`: http://www.dabeaz.com/GIL/gilvis/measure2.py