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  26 <a name="boost.sort.spreadsort.integer__idm46709765063136"></a><div class="titlepage"></div>
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  28 <h2><span class="refentrytitle">Function template integer_sort</span></h2>
  29 <p>boost::sort::spreadsort::integer_sort &#8212; Integer sort algorithm using random access iterators with just right-shift functor. (All variants fall back to <code class="computeroutput">boost::sort::pdqsort</code> if the data size is too small, &lt; <code class="computeroutput">detail::min_sort_size</code>). </p>
  30 </div>
  31 <h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
  32 <div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="../../../header/boost/sort/spreadsort/integer_sort_hpp.html" title="Header &lt;boost/sort/spreadsort/integer_sort.hpp&gt;">boost/sort/spreadsort/integer_sort.hpp</a>&gt;
  33
  34 </span>
  35 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> RandomAccessIter<span class="special">,</span> <span class="keyword">typename</span> Right_shift<span class="special">&gt;</span>
  36   <span class="keyword">void</span> <span class="identifier">integer_sort</span><span class="special">(</span><span class="identifier">RandomAccessIter</span> first<span class="special">,</span> <span class="identifier">RandomAccessIter</span> last<span class="special">,</span>
  37                     <span class="identifier">Right_shift</span> shift<span class="special">)</span><span class="special">;</span></pre></div>
  38 <div class="refsect1">
  39 <a name="idm45993903352560"></a><h2>Description</h2>
  40 <p><code class="computeroutput">integer_sort</code> is a fast templated in-place hybrid radix/comparison algorithm, which in testing tends to be roughly 50% to 2X faster than <code class="computeroutput">std::sort</code> for large tests (&gt;=100kB).<br>
  41  </p>
  42 <p><b>Performance:&#160;</b>Worst-case performance is <span class="emphasis"><em> O(N * (lg(range)/s + s)) </em></span>, so <code class="computeroutput">integer_sort</code> is asymptotically faster than pure comparison-based algorithms. <code class="computeroutput">s</code> is <code class="computeroutput">max_splits</code>, which defaults to 11, so its worst-case with default settings for 32-bit integers is <span class="emphasis"><em> O(N * ((32/11) </em></span> slow radix-based iterations fast comparison-based iterations).<br>
  43 <br>
  44 Some performance plots of runtime vs. n and log(range) are provided:<br>
  45  <a href="../../../../../doc/graph/windows_integer_sort.htm" target="_top">windows_integer_sort</a><br>
  46  <a href="../../../../../doc/graph/osx_integer_sort.htm" target="_top">osx_integer_sort</a></p>
  47 <p>
  48
  49
  50
  51
  52
  53
  54 </p>
  55 <div class="warning"><table border="0" summary="Warning">
  56 <tr>
  57 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../../../../doc/src/images/warning.png"></td>
  58 <th align="left">Warning</th>
  59 </tr>
  60 <tr><td align="left" valign="top"><p>Throwing an exception may cause data loss. This will also throw if a small vector resize throws, in which case there will be no data loss. </p></td></tr>
  61 </table></div>
  62 <p>
  63 </p>
  64 <div class="warning"><table border="0" summary="Warning">
  65 <tr>
  66 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Warning]" src="../../../../../../../doc/src/images/warning.png"></td>
  67 <th align="left">Warning</th>
  68 </tr>
  69 <tr><td align="left" valign="top"><p>Invalid arguments cause undefined behaviour. </p></td></tr>
  70 </table></div>
  71 <p>
  72 </p>
  73 <div class="note"><table border="0" summary="Note">
  74 <tr>
  75 <td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../../../../doc/src/images/note.png"></td>
  76 <th align="left">Note</th>
  77 </tr>
  78 <tr><td align="left" valign="top"><p><code class="computeroutput">spreadsort</code> function provides a wrapper that calls the fastest sorting algorithm available for a data type, enabling faster generic-programming.</p></td></tr>
  79 </table></div>
  80 <p>
  81 </p>
  82 <p>The lesser of <span class="emphasis"><em> O(N*log(N)) </em></span> comparisons and <span class="emphasis"><em> O(N*log(K/S + S)) </em></span>operations worst-case, where: </p>
  83 <p>
  84
  85 </p>
  86 <p>* N is <code class="computeroutput">last</code> - <code class="computeroutput">first</code>, </p>
  87 <p>
  88
  89 </p>
  90 <p>* K is the log of the range in bits (32 for 32-bit integers using their full range), </p>
  91 <p>
  92
  93 </p>
  94 <p>* S is a constant called max_splits, defaulting to 11 (except for strings where it is the log of the character size). </p>
  95 <p>
  96
  97 </p>
  98 <div class="variablelist"><table border="0" class="variablelist compact">
  99 <colgroup>
 100 <col align="left" valign="top">
 101 <col>
 102 </colgroup>
 103 <tbody>
 104 <tr>
 105 <td><p><span class="term">Parameters:</span></p></td>
 106 <td><div class="variablelist"><table border="0" class="variablelist compact">
 107 <colgroup>
 108 <col align="left" valign="top">
 109 <col>
 110 </colgroup>
 111 <tbody>
 112 <tr>
 113 <td><p><span class="term"><code class="computeroutput">first</code></span></p></td>
 114 <td><p>Iterator pointer to first element. </p></td>
 115 </tr>
 116 <tr>
 117 <td><p><span class="term"><code class="computeroutput">last</code></span></p></td>
 118 <td><p>Iterator pointing to one beyond the end of data. </p></td>
 119 </tr>
 120 <tr>
 121 <td><p><span class="term"><code class="computeroutput">shift</code></span></p></td>
 122 <td><p>A functor that returns the result of shifting the value_type right a specified number of bits.</p></td>
 123 </tr>
 124 </tbody>
 125 </table></div></td>
 126 </tr>
 127 <tr>
 128 <td><p><span class="term">Requires:</span></p></td>
 129 <td><p>[<code class="computeroutput">first</code>, <code class="computeroutput">last</code>) is a valid range. </p></td>
 130 </tr>
 131 <tr>
 132 <td><p><span class="term">Requires:</span></p></td>
 133 <td><p><code class="computeroutput">RandomAccessIter</code> <code class="computeroutput">value_type</code> is mutable. </p></td>
 134 </tr>
 135 <tr>
 136 <td><p><span class="term">Requires:</span></p></td>
 137 <td><p><code class="computeroutput">RandomAccessIter</code> <code class="computeroutput">value_type</code> is <a href="http://en.cppreference.com/w/cpp/concept/LessThanComparable" target="_top">LessThanComparable</a> </p></td>
 138 </tr>
 139 <tr>
 140 <td><p><span class="term">Postconditions:</span></p></td>
 141 <td><p>The elements in the range [<code class="computeroutput">first</code>, <code class="computeroutput">last</code>) are sorted in ascending order.</p></td>
 142 </tr>
 143 <tr>
 144 <td><p><span class="term">Throws:</span></p></td>
 145 <td>std::exception Propagates exceptions if any of the element comparisons, the element swaps (or moves), the right shift, subtraction of right-shifted elements, functors, or any operations on iterators throw.</td>
 146 </tr>
 147 </tbody>
 148 </table></div>
 149 </div>
 150 </div>
 151 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 152 <td align="left"></td>
 153 <td align="right"><div class="copyright-footer">Copyright &#169; 2014-2017 Steven
 154       Ross, Francisco Tapia, Orson Peters<p>
 155         Distributed under the <a href="http://boost.org/LICENSE_1_0.txt" target="_top">Boost
 156         Software License, Version 1.0</a>.
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