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  25 <div class="refentry">
  26 <a name="boost.compute.exclusive_scan"></a><div class="titlepage"></div>
  27 <div class="refnamediv">
  28 <h2><span class="refentrytitle">Function exclusive_scan</span></h2>
  29 <p>boost::compute::exclusive_scan</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="../../boost_compute/reference.html#header.boost.compute.algorithm.exclusive_scan_hpp" title="Header &lt;boost/compute/algorithm/exclusive_scan.hpp&gt;">boost/compute/algorithm/exclusive_scan.hpp</a>&gt;
  33
  34 </span>
  35 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> InputIterator<span class="special">,</span> <span class="keyword">typename</span> OutputIterator<span class="special">,</span> <span class="keyword">typename</span> T<span class="special">,</span>
  36          <span class="keyword">typename</span> BinaryOperator<span class="special">&gt;</span>
  37   <span class="identifier">OutputIterator</span>
  38   <span class="identifier">exclusive_scan</span><span class="special">(</span><span class="identifier">InputIterator</span> first<span class="special">,</span> <span class="identifier">InputIterator</span> last<span class="special">,</span>
  39                  <span class="identifier">OutputIterator</span> result<span class="special">,</span> <span class="identifier">T</span> init<span class="special">,</span> <span class="identifier">BinaryOperator</span> binary_op<span class="special">,</span>
  40                  <span class="identifier">command_queue</span> <span class="special">&amp;</span> queue <span class="special">=</span> <span class="identifier">system</span><span class="special">::</span><span class="identifier">default_queue</span><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</span>
  41 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> InputIterator<span class="special">,</span> <span class="keyword">typename</span> OutputIterator<span class="special">,</span> <span class="keyword">typename</span> T<span class="special">&gt;</span>
  42   <span class="identifier">OutputIterator</span>
  43   <span class="identifier">exclusive_scan</span><span class="special">(</span><span class="identifier">InputIterator</span> first<span class="special">,</span> <span class="identifier">InputIterator</span> last<span class="special">,</span>
  44                  <span class="identifier">OutputIterator</span> result<span class="special">,</span> <span class="identifier">T</span> init<span class="special">,</span>
  45                  <span class="identifier">command_queue</span> <span class="special">&amp;</span> queue <span class="special">=</span> <span class="identifier">system</span><span class="special">::</span><span class="identifier">default_queue</span><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</span>
  46 <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> InputIterator<span class="special">,</span> <span class="keyword">typename</span> OutputIterator<span class="special">&gt;</span>
  47   <span class="identifier">OutputIterator</span>
  48   <span class="identifier">exclusive_scan</span><span class="special">(</span><span class="identifier">InputIterator</span> first<span class="special">,</span> <span class="identifier">InputIterator</span> last<span class="special">,</span>
  49                  <span class="identifier">OutputIterator</span> result<span class="special">,</span>
  50                  <span class="identifier">command_queue</span> <span class="special">&amp;</span> queue <span class="special">=</span> <span class="identifier">system</span><span class="special">::</span><span class="identifier">default_queue</span><span class="special">(</span><span class="special">)</span><span class="special">)</span><span class="special">;</span></pre></div>
  51 <div class="refsect1">
  52 <a name="idm46113334255056"></a><h2>Description</h2>
  53 <p>Performs an exclusive scan of the elements in the range [<code class="computeroutput">first</code>, <code class="computeroutput">last</code>) and stores the results in the range beginning at <code class="computeroutput">result</code>.</p>
  54 <p>Each element in the output is assigned to the sum of all the previous values in the input.</p>
  55 <p>
  56
  57 The default operation is to add the elements up.</p>
  58 <pre class="programlisting"></pre>
  59 <p> But different associative operation can be specified as <code class="computeroutput">binary_op</code> instead (e.g., multiplication, maximum, minimum). Also value used to initialized the scan sequence can be specified.</p>
  60 <pre class="programlisting"></pre>
  61 <p> Space complexity on GPUs: \Omega(n)<br>
  62  Space complexity on GPUs when <code class="computeroutput">first</code> == <code class="computeroutput">result:</code> \Omega(2n)<br>
  63  Space complexity on CPUs: \Omega(1)</p>
  64 <p><span class="bold"><strong>See Also:</strong></span></p>
  65 <p>inclusive_scan() </p>
  66 <p>
  67 </p>
  68 <p>
  69 </p>
  70 <div class="variablelist"><table border="0" class="variablelist compact">
  71 <colgroup>
  72 <col align="left" valign="top">
  73 <col>
  74 </colgroup>
  75 <tbody>
  76 <tr>
  77 <td><p><span class="term">Parameters:</span></p></td>
  78 <td><div class="variablelist"><table border="0" class="variablelist compact">
  79 <colgroup>
  80 <col align="left" valign="top">
  81 <col>
  82 </colgroup>
  83 <tbody>
  84 <tr>
  85 <td><p><span class="term"><code class="computeroutput">binary_op</code></span></p></td>
  86 <td><p>associative binary operator </p></td>
  87 </tr>
  88 <tr>
  89 <td><p><span class="term"><code class="computeroutput">first</code></span></p></td>
  90 <td><p>first element in the range to scan </p></td>
  91 </tr>
  92 <tr>
  93 <td><p><span class="term"><code class="computeroutput">init</code></span></p></td>
  94 <td><p>value used to initialize the scan sequence </p></td>
  95 </tr>
  96 <tr>
  97 <td><p><span class="term"><code class="computeroutput">last</code></span></p></td>
  98 <td><p>last element in the range to scan </p></td>
  99 </tr>
 100 <tr>
 101 <td><p><span class="term"><code class="computeroutput">queue</code></span></p></td>
 102 <td><p>command queue to perform the operation</p></td>
 103 </tr>
 104 <tr>
 105 <td><p><span class="term"><code class="computeroutput">result</code></span></p></td>
 106 <td><p>first element in the result range </p></td>
 107 </tr>
 108 </tbody>
 109 </table></div></td>
 110 </tr>
 111 <tr>
 112 <td><p><span class="term">Returns:</span></p></td>
 113 <td><p><code class="computeroutput">OutputIterator</code> to the end of the result range</p></td>
 114 </tr>
 115 </tbody>
 116 </table></div>
 117 </div>
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 121 <td align="right"><div class="copyright-footer">Copyright &#169; 2013, 2014 Kyle Lutz<p>
 122         Distributed under the Boost Software License, Version 1.0. (See accompanying
 123         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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