1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Function reduce</title> 5<link rel="stylesheet" href="../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../index.html" title="Chapter 1. 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When used with non-associative functions the result may be non-deterministic and vary in precision. Notably this affects the <code class="computeroutput">plus<float>()</code> function as floating-point addition is not associative and may produce slightly different results than a serial algorithm.</p> 49<p>This algorithm supports both host and device iterators for the result argument. This allows for values to be reduced and copied to the host all with a single function call.</p> 50<p>For example, to calculate the sum of the values in a device vector and copy the result to a value on the host:</p> 51<pre class="programlisting"></pre> 52<p> Note that while the the <code class="computeroutput">reduce()</code> algorithm is conceptually identical to the <code class="computeroutput">accumulate()</code> algorithm, its implementation is substantially more efficient on parallel hardware. For more information, see the documentation on the <code class="computeroutput">accumulate()</code> algorithm.</p> 53<p>Space complexity on GPUs: \Omega(n)<br> 54 Space complexity on CPUs: \Omega(1)</p> 55<p><span class="bold"><strong>See Also:</strong></span></p> 56<p>accumulate() </p> 57<p> 58</p> 59<p> 60</p> 61<div class="variablelist"><table border="0" class="variablelist compact"> 62<colgroup> 63<col align="left" valign="top"> 64<col> 65</colgroup> 66<tbody><tr> 67<td><p><span class="term">Parameters:</span></p></td> 68<td><div class="variablelist"><table border="0" class="variablelist compact"> 69<colgroup> 70<col align="left" valign="top"> 71<col> 72</colgroup> 73<tbody> 74<tr> 75<td><p><span class="term"><code class="computeroutput">first</code></span></p></td> 76<td><p>first element in the input range </p></td> 77</tr> 78<tr> 79<td><p><span class="term"><code class="computeroutput">function</code></span></p></td> 80<td><p>binary reduction function </p></td> 81</tr> 82<tr> 83<td><p><span class="term"><code class="computeroutput">last</code></span></p></td> 84<td><p>last element in the input range </p></td> 85</tr> 86<tr> 87<td><p><span class="term"><code class="computeroutput">queue</code></span></p></td> 88<td><p>command queue to perform the operation</p></td> 89</tr> 90<tr> 91<td><p><span class="term"><code class="computeroutput">result</code></span></p></td> 92<td><p>iterator pointing to the output </p></td> 93</tr> 94</tbody> 95</table></div></td> 96</tr></tbody> 97</table></div> 98</div> 99</div> 100<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 101<td align="left"></td> 102<td align="right"><div class="copyright-footer">Copyright © 2013, 2014 Kyle Lutz<p> 103 Distributed under the Boost Software License, Version 1.0. (See accompanying 104 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>) 105 </p> 106</div></td> 107</tr></table> 108<hr> 109<div class="spirit-nav"> 110<a accesskey="p" href="random_shuffle.html"><img src="../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../../boost_compute/reference.html#header.boost.compute.algorithm.reduce_hpp"><img src="../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../index.html"><img src="../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="reduce_by_key.html"><img src="../../../../../../doc/src/images/next.png" alt="Next"></a> 111</div> 112</body> 113</html> 114
