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  25 <div class="refentry">
  26 <a name="boost.histogram.accumulators.sum"></a><div class="titlepage"></div>
  27 <div class="refnamediv">
  28 <h2><span class="refentrytitle">Class template sum</span></h2>
  29 <p>boost::histogram::accumulators::sum &#8212; Uses Neumaier algorithm to compute accurate sums. </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="../../../histogram/reference.html#header.boost.histogram.accumulators.sum_hpp" title="Header &lt;boost/histogram/accumulators/sum.hpp&gt;">boost/histogram/accumulators/sum.hpp</a>&gt;
  33
  34 </span><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> RealType<span class="special">&gt;</span>
  35 <span class="keyword">class</span> <a class="link" href="sum.html" title="Class template sum">sum</a> <span class="special">{</span>
  36 <span class="keyword">public</span><span class="special">:</span>
  37   <span class="comment">// <a class="link" href="sum.html#boost.histogram.accumulators.sumconstruct-copy-destruct">construct/copy/destruct</a></span>
  38   <a class="link" href="sum.html#idm45414525141184-bb"><span class="identifier">sum</span></a><span class="special">(</span><span class="special">)</span> <span class="special">=</span> <span class="keyword">default</span><span class="special">;</span>
  39   <span class="keyword">explicit</span> <a class="link" href="sum.html#idm45414525140624-bb"><span class="identifier">sum</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
  40   <a class="link" href="sum.html" title="Class template sum">sum</a> <span class="special">&amp;</span> <a class="link" href="sum.html#idm45414525138800-bb"><span class="keyword">operator</span><span class="special">=</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span>
  41
  42   <span class="comment">// <a class="link" href="sum.html#idm45414525160368-bb">public member functions</a></span>
  43   <a class="link" href="sum.html" title="Class template sum">sum</a> <span class="special">&amp;</span> <a class="link" href="sum.html#idm45414525159808-bb"><span class="keyword">operator</span><span class="special">++</span></a><span class="special">(</span><span class="special">)</span><span class="special">;</span>
  44   <a class="link" href="sum.html" title="Class template sum">sum</a> <span class="special">&amp;</span> <a class="link" href="sum.html#idm45414525158384-bb"><span class="keyword">operator</span><span class="special">+=</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</span><span class="special">)</span><span class="special">;</span>
  45   <a class="link" href="sum.html" title="Class template sum">sum</a> <span class="special">&amp;</span> <a class="link" href="sum.html#idm45414525156256-bb"><span class="keyword">operator</span> <span class="special">*=</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</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> T<span class="special">&gt;</span> <span class="keyword">bool</span> <a class="link" href="sum.html#idm45414525154144-bb"><span class="keyword">operator</span><span class="special">==</span></a><span class="special">(</span><span class="keyword">const</span> <a class="link" href="sum.html" title="Class template sum">sum</a><span class="special">&lt;</span> <span class="identifier">T</span> <span class="special">&gt;</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
  47   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> <span class="keyword">bool</span> <a class="link" href="sum.html#idm45414525151040-bb"><span class="keyword">operator</span><span class="special">!=</span></a><span class="special">(</span><span class="keyword">const</span> <span class="identifier">T</span> <span class="special">&amp;</span><span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span>
  48   <span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</span> <a class="link" href="sum.html#idm45414525148384-bb"><span class="identifier">large</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  49   <span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</span> <a class="link" href="sum.html#idm45414525146960-bb"><span class="identifier">small</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  50   <a class="link" href="sum.html#idm45414525145536-bb"><span class="keyword">operator</span> <span class="identifier">RealType</span></a><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span>
  51   <span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Archive<span class="special">&gt;</span> <span class="keyword">void</span> <a class="link" href="sum.html#idm45414525144416-bb"><span class="identifier">serialize</span></a><span class="special">(</span><span class="identifier">Archive</span> <span class="special">&amp;</span><span class="special">,</span> <span class="keyword">unsigned</span><span class="special">)</span><span class="special">;</span>
  52 <span class="special">}</span><span class="special">;</span></pre></div>
  53 <div class="refsect1">
  54 <a name="idm45212148985600"></a><h2>Description</h2>
  55 <p>The algorithm uses memory for two floats and is three to five times slower compared to a simple floating point number used to accumulate a sum, but the relative error of the sum is at the level of the machine precision, independent of the number of samples.</p>
  56 <p>A. Neumaier, Zeitschrift fuer Angewandte Mathematik und Mechanik 54 (1974) 39-51. </p>
  57 <div class="refsect2">
  58 <a name="idm45212148984304"></a><h3>
  59 <a name="boost.histogram.accumulators.sumconstruct-copy-destruct"></a><code class="computeroutput">sum</code>
  60         public
  61        construct/copy/destruct</h3>
  62 <div class="orderedlist"><ol class="orderedlist" type="1">
  63 <li class="listitem"><pre class="literallayout"><a name="idm45414525141184-bb"></a><span class="identifier">sum</span><span class="special">(</span><span class="special">)</span> <span class="special">=</span> <span class="keyword">default</span><span class="special">;</span></pre></li>
  64 <li class="listitem">
  65 <pre class="literallayout"><span class="keyword">explicit</span> <a name="idm45414525140624-bb"></a><span class="identifier">sum</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</span> value<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre>Initialize sum to value. </li>
  66 <li class="listitem">
  67 <pre class="literallayout"><a class="link" href="sum.html" title="Class template sum">sum</a> <span class="special">&amp;</span> <a name="idm45414525138800-bb"></a><span class="keyword">operator</span><span class="special">=</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</span> value<span class="special">)</span> <span class="keyword">noexcept</span><span class="special">;</span></pre>Set sum to value. </li>
  68 </ol></div>
  69 </div>
  70 <div class="refsect2">
  71 <a name="idm45212148961264"></a><h3>
  72 <a name="idm45414525160368-bb"></a><code class="computeroutput">sum</code> public member functions</h3>
  73 <div class="orderedlist"><ol class="orderedlist" type="1">
  74 <li class="listitem">
  75 <pre class="literallayout"><a class="link" href="sum.html" title="Class template sum">sum</a> <span class="special">&amp;</span> <a name="idm45414525159808-bb"></a><span class="keyword">operator</span><span class="special">++</span><span class="special">(</span><span class="special">)</span><span class="special">;</span></pre>Increment sum by one. </li>
  76 <li class="listitem">
  77 <pre class="literallayout"><a class="link" href="sum.html" title="Class template sum">sum</a> <span class="special">&amp;</span> <a name="idm45414525158384-bb"></a><span class="keyword">operator</span><span class="special">+=</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</span> value<span class="special">)</span><span class="special">;</span></pre>Increment sum by value. </li>
  78 <li class="listitem">
  79 <pre class="literallayout"><a class="link" href="sum.html" title="Class template sum">sum</a> <span class="special">&amp;</span> <a name="idm45414525156256-bb"></a><span class="keyword">operator</span> <span class="special">*=</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</span> value<span class="special">)</span><span class="special">;</span></pre>Scale by value. </li>
  80 <li class="listitem"><pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> <span class="keyword">bool</span> <a name="idm45414525154144-bb"></a><span class="keyword">operator</span><span class="special">==</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="sum.html" title="Class template sum">sum</a><span class="special">&lt;</span> <span class="identifier">T</span> <span class="special">&gt;</span> <span class="special">&amp;</span> rhs<span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></pre></li>
  81 <li class="listitem"><pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">&gt;</span> <span class="keyword">bool</span> <a name="idm45414525151040-bb"></a><span class="keyword">operator</span><span class="special">!=</span><span class="special">(</span><span class="keyword">const</span> <span class="identifier">T</span> <span class="special">&amp;</span> rhs<span class="special">)</span> <span class="keyword">const</span> <span class="keyword">noexcept</span><span class="special">;</span></pre></li>
  82 <li class="listitem">
  83 <pre class="literallayout"><span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</span> <a name="idm45414525148384-bb"></a><span class="identifier">large</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>Return large part of the sum. </li>
  84 <li class="listitem">
  85 <pre class="literallayout"><span class="keyword">const</span> <span class="identifier">RealType</span> <span class="special">&amp;</span> <a name="idm45414525146960-bb"></a><span class="identifier">small</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre>Return small part of the sum. </li>
  86 <li class="listitem"><pre class="literallayout"><a name="idm45414525145536-bb"></a><span class="keyword">operator</span> <span class="identifier">RealType</span><span class="special">(</span><span class="special">)</span> <span class="keyword">const</span><span class="special">;</span></pre></li>
  87 <li class="listitem"><pre class="literallayout"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> Archive<span class="special">&gt;</span> <span class="keyword">void</span> <a name="idm45414525144416-bb"></a><span class="identifier">serialize</span><span class="special">(</span><span class="identifier">Archive</span> <span class="special">&amp;</span> ar<span class="special">,</span> <span class="keyword">unsigned</span><span class="special">)</span><span class="special">;</span></pre></li>
  88 </ol></div>
  89 </div>
  90 </div>
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