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Library/boost/libs/python/doc/html/numpy/tutorial/ufunc.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title>Ufuncs - Boost.Python NumPy extension 1.0 documentation</title> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <link rel="stylesheet" href="../_static/style.css" type="text/css" /> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT: '../', VERSION: '1.0', COLLAPSE_MODINDEX: false, FILE_SUFFIX: '.html' }; </script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <link rel="index" title="Index" href="../genindex.html" /> <link rel="search" title="Search" href="../search.html" /> <link rel="top" title="Boost.Python NumPy extension 1.0 documentation" href="../index.html" /> <link rel="up" title="Boost.Python NumPy extension Tutorial" href="index.html" /> <link rel="next" title="How to access data using raw pointers" href="fromdata.html" /> <link rel="prev" title="Creating ndarrays" href="ndarray.html" /> </head> <body> <div class="header"> <table border="0" cellpadding="7" cellspacing="0" width="100%" summary= "header"> <tr> <td valign="top" width="300"> <h3><a href="../index.html"><img alt="C++ Boost" src="../_static/bpl.png" border="0"></a></h3> </td> <td > <h1 align="center"><a href="../index.html">(NumPy)</a></h1> <!-- <h2 align="center">CallPolicies Concept</h2>--> </td> <td> <div id="searchbox" style="display: none"> <form class="search" action="../search.html" method="get"> <input type="text" name="q" size="18" /> <input type="submit" value="Search" /> <input type="hidden" name="check_keywords" value="yes" /> <input type="hidden" name="area" value="default" /> </form> </div> <script type="text/javascript">$('#searchbox').show(0);</script> </td> </tr> </table> </div> <hr/> <div class="content"> <div class="navbar" style="text-align:right;"> <a class="prev" title="Creating ndarrays" href="ndarray.html"><img src="../_static/prev.png" alt="prev"/></a> <a class="up" title="Boost.Python NumPy extension Tutorial" href="index.html"><img src="../_static/up.png" alt="up"/></a> <a class="next" title="How to access data using raw pointers" href="fromdata.html"><img src="../_static/next.png" alt="next"/></a> </div> <div class="section" id="ufuncs"> <h1>Ufuncs</h1> <p>Ufuncs or universal functions operate on ndarrays element by element, and support array broadcasting, type casting, and other features.</p> <p>Lets try and see how we can use the binary and unary ufunc methods</p> <p>After the neccessary includes</p> <div class="highlight-c++"><div class="highlight"><pre><span class="cp">#include</span> <span class="cpf"><boost/python/numpy.hpp></span><span class="cp"></span> <span class="cp">#include</span> <span class="cpf"><iostream></span><span class="cp"></span> <span class="k">namespace</span> <span class="n">p</span> <span class="o">=</span> <span class="n">boost</span><span class="o">::</span><span class="n">python</span><span class="p">;</span> <span class="k">namespace</span> <span class="n">np</span> <span class="o">=</span> <span class="n">boost</span><span class="o">::</span><span class="n">python</span><span class="o">::</span><span class="n">numpy</span><span class="p">;</span> </pre></div> </div> <p>Now we create the structs necessary to implement the ufuncs. The typedefs <em>must</em> be made as the ufunc generators take these typedefs as inputs and return an error otherwise</p> <div class="highlight-c++"><div class="highlight"><pre><span class="k">struct</span> <span class="n">UnarySquare</span> <span class="p">{</span> <span class="k">typedef</span> <span class="kt">double</span> <span class="n">argument_type</span><span class="p">;</span> <span class="k">typedef</span> <span class="kt">double</span> <span class="n">result_type</span><span class="p">;</span> <span class="kt">double</span> <span class="nf">operator</span><span class="p">()(</span><span class="kt">double</span> <span class="n">r</span><span class="p">)</span> <span class="k">const</span> <span class="p">{</span> <span class="k">return</span> <span class="n">r</span> <span class="o">*</span> <span class="n">r</span><span class="p">;}</span> <span class="p">};</span> <span class="k">struct</span> <span class="n">BinarySquare</span> <span class="p">{</span> <span class="k">typedef</span> <span class="kt">double</span> <span class="n">first_argument_type</span><span class="p">;</span> <span class="k">typedef</span> <span class="kt">double</span> <span class="n">second_argument_type</span><span class="p">;</span> <span class="k">typedef</span> <span class="kt">double</span> <span class="n">result_type</span><span class="p">;</span> <span class="kt">double</span> <span class="nf">operator</span><span class="p">()(</span><span class="kt">double</span> <span class="n">a</span><span class="p">,</span><span class="kt">double</span> <span class="n">b</span><span class="p">)</span> <span class="k">const</span> <span class="p">{</span> <span class="k">return</span> <span class="p">(</span><span class="n">a</span><span class="o">*</span><span class="n">a</span> <span class="o">+</span> <span class="n">b</span><span class="o">*</span><span class="n">b</span><span class="p">)</span> <span class="p">;</span> <span class="p">}</span> <span class="p">};</span> </pre></div> </div> <p>Initialise the Python runtime and the numpy module</p> <div class="highlight-c++"><div class="highlight"><pre><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="n">Py_Initialize</span><span class="p">();</span> <span class="n">np</span><span class="o">::</span><span class="n">initialize</span><span class="p">();</span> </pre></div> </div> <p>Now expose the struct UnarySquare to Python as a class, and let ud be the class object.</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">object</span> <span class="n">ud</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">class_</span><span class="o"><</span><span class="n">UnarySquare</span><span class="p">,</span> <span class="n">boost</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">UnarySquare</span><span class="o">></span> <span class="o">></span><span class="p">(</span><span class="s">"UnarySquare"</span><span class="p">);</span> <span class="n">ud</span><span class="p">.</span><span class="n">def</span><span class="p">(</span><span class="s">"__call__"</span><span class="p">,</span> <span class="n">np</span><span class="o">::</span><span class="n">unary_ufunc</span><span class="o"><</span><span class="n">UnarySquare</span><span class="o">>::</span><span class="n">make</span><span class="p">());</span> </pre></div> </div> <p>Let inst be an instance of the class ud</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">object</span> <span class="n">inst</span> <span class="o">=</span> <span class="n">ud</span><span class="p">();</span> </pre></div> </div> <p>Use the “__call__” method to call the overloaded () operator and print the value</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="s">"Square of unary scalar 1.0 is "</span> <span class="o"><<</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span><span class="o"><</span><span class="kt">char</span> <span class="k">const</span> <span class="o">*></span><span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">inst</span><span class="p">.</span><span class="n">attr</span><span class="p">(</span><span class="s">"__call__"</span><span class="p">)(</span><span class="mf">1.0</span><span class="p">)))</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span> </pre></div> </div> <p>Create an array in C++</p> <div class="highlight-c++"><div class="highlight"><pre><span class="kt">int</span> <span class="n">arr</span><span class="p">[]</span> <span class="o">=</span> <span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">}</span> <span class="p">;</span> </pre></div> </div> <p>..and use it to create the ndarray in Python</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">np</span><span class="o">::</span><span class="n">ndarray</span> <span class="n">demo_array</span> <span class="o">=</span> <span class="n">np</span><span class="o">::</span><span class="n">from_data</span><span class="p">(</span><span class="n">arr</span><span class="p">,</span> <span class="n">np</span><span class="o">::</span><span class="n">dtype</span><span class="o">::</span><span class="n">get_builtin</span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="p">(),</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="mi">4</span><span class="p">),</span> <span class="n">p</span><span class="o">::</span><span class="n">make_tuple</span><span class="p">(</span><span class="mi">4</span><span class="p">),</span> <span class="n">p</span><span class="o">::</span><span class="n">object</span><span class="p">());</span> </pre></div> </div> <p>Print out the demo array</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="s">"Demo array is "</span> <span class="o"><<</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span><span class="o"><</span><span class="kt">char</span> <span class="k">const</span> <span class="o">*></span><span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">demo_array</span><span class="p">))</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span> </pre></div> </div> <p>Call the “__call__” method to perform the operation and assign the value to result_array</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">object</span> <span class="n">result_array</span> <span class="o">=</span> <span class="n">inst</span><span class="p">.</span><span class="n">attr</span><span class="p">(</span><span class="s">"__call__"</span><span class="p">)(</span><span class="n">demo_array</span><span class="p">);</span> </pre></div> </div> <p>Print the resultant array</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="s">"Square of demo array is "</span> <span class="o"><<</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span><span class="o"><</span><span class="kt">char</span> <span class="k">const</span> <span class="o">*></span><span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">result_array</span><span class="p">))</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span> </pre></div> </div> <p>Lets try the same with a list</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">p</span><span class="o">::</span><span class="n">list</span> <span class="n">li</span><span class="p">;</span> <span class="n">li</span><span class="p">.</span><span class="n">append</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span> <span class="n">li</span><span class="p">.</span><span class="n">append</span><span class="p">(</span><span class="mi">7</span><span class="p">);</span> </pre></div> </div> <p>Print out the demo list</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="s">"Demo list is "</span> <span class="o"><<</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span><span class="o"><</span><span class="kt">char</span> <span class="k">const</span> <span class="o">*></span><span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">li</span><span class="p">))</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span> </pre></div> </div> <p>Call the ufunc for the list</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">result_array</span> <span class="o">=</span> <span class="n">inst</span><span class="p">.</span><span class="n">attr</span><span class="p">(</span><span class="s">"__call__"</span><span class="p">)(</span><span class="n">li</span><span class="p">);</span> </pre></div> </div> <p>And print the list out</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="s">"Square of demo list is "</span> <span class="o"><<</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span><span class="o"><</span><span class="kt">char</span> <span class="k">const</span> <span class="o">*></span><span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">result_array</span><span class="p">))</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span> </pre></div> </div> <p>Now lets try Binary ufuncs. Again, expose the struct BinarySquare to Python as a class, and let ud be the class object</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">ud</span> <span class="o">=</span> <span class="n">p</span><span class="o">::</span><span class="n">class_</span><span class="o"><</span><span class="n">BinarySquare</span><span class="p">,</span> <span class="n">boost</span><span class="o">::</span><span class="n">shared_ptr</span><span class="o"><</span><span class="n">BinarySquare</span><span class="o">></span> <span class="o">></span><span class="p">(</span><span class="s">"BinarySquare"</span><span class="p">);</span> <span class="n">ud</span><span class="p">.</span><span class="n">def</span><span class="p">(</span><span class="s">"__call__"</span><span class="p">,</span> <span class="n">np</span><span class="o">::</span><span class="n">binary_ufunc</span><span class="o"><</span><span class="n">BinarySquare</span><span class="o">>::</span><span class="n">make</span><span class="p">());</span> </pre></div> </div> <p>And initialise ud</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">inst</span> <span class="o">=</span> <span class="n">ud</span><span class="p">();</span> </pre></div> </div> <p>Print the two input lists</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="s">"The two input list for binary ufunc are "</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span> <span class="o"><<</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span><span class="o"><</span><span class="kt">char</span> <span class="k">const</span> <span class="o">*></span><span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">demo_array</span><span class="p">))</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span> <span class="o"><<</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span><span class="o"><</span><span class="kt">char</span> <span class="k">const</span> <span class="o">*></span><span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">demo_array</span><span class="p">))</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span> </pre></div> </div> <p>Call the binary ufunc taking demo_array as both inputs</p> <div class="highlight-c++"><div class="highlight"><pre><span class="n">result_array</span> <span class="o">=</span> <span class="n">inst</span><span class="p">.</span><span class="n">attr</span><span class="p">(</span><span class="s">"__call__"</span><span class="p">)(</span><span class="n">demo_array</span><span class="p">,</span><span class="n">demo_array</span><span class="p">);</span> </pre></div> </div> <p>And print the output</p> <div class="highlight-c++"><div class="highlight"><pre> <span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o"><<</span> <span class="s">"Square of list with binary ufunc is "</span> <span class="o"><<</span> <span class="n">p</span><span class="o">::</span><span class="n">extract</span><span class="o"><</span><span class="kt">char</span> <span class="k">const</span> <span class="o">*></span><span class="p">(</span><span class="n">p</span><span class="o">::</span><span class="n">str</span><span class="p">(</span><span class="n">result_array</span><span class="p">))</span> <span class="o"><<</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span> <span class="p">}</span> </pre></div> </div> </div> <div class="navbar" style="text-align:right;"> <a class="prev" title="Creating ndarrays" href="ndarray.html"><img src="../_static/prev.png" alt="prev"/></a> <a class="up" title="Boost.Python NumPy extension Tutorial" href="index.html"><img src="../_static/up.png" alt="up"/></a> <a class="next" title="How to access data using raw pointers" href="fromdata.html"><img src="../_static/next.png" alt="next"/></a> </div> </div> </body> </html>