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<h1 class="topictitle1">parallel_sort Template Function</h1>
<div>
<div class="section"><h2 class="sectiontitle">Summary</h2> Sort a sequence. </div>
<div class="section"><h2 class="sectiontitle">Header</h2>
<pre>#include "tbb/parallel_sort.h"</pre>
</div>
<div class="section"><h2 class="sectiontitle">Syntax</h2>
<pre>template<typename RandomAccessIterator>
void parallel_sort(RandomAccessIterator begin, RandomAccessIterator end);
template<typename RandomAccessIterator, typename Compare>
void parallel_sort(RandomAccessIterator begin,
RandomAccessIterator end,
const Compare& comp );
</pre></div>
<div class="section"><h2 class="sectiontitle">Description</h2> <p> Performs an <em>unstable</em> sort of sequence [<em>begin1</em>, <em>end1</em>). An unstable sort
might not preserve the relative ordering of elements with equal keys. The sort is deterministic;
sorting the same sequence will produce the same result each time. The requirements on the
iterator and sequence are the same as for<samp class="codeph"> std::sort</samp> . Specifically,
<samp class="codeph">RandomAccessIterator</samp> must be a random access iterator, and its value type
<em>T</em> must model the requirements in the table below.</p>
<div class="tablenoborder"><table cellpadding="4" summary="" width="100%" frame="hsides" border="1" rules="all"><caption><span class="tablecap">Requirements on Value Type T of RandomAccessIterator
for parallel_sort</span></caption>
<thead align="left">
<tr>
<th class="cellrowborder" valign="top" id="d8660e85">
<p>Pseudo-Signature
</p>
</th>
<th class="row-nocellborder" valign="top" id="d8660e91">
<p>Semantics
</p>
</th>
</tr>
</thead>
<tbody>
<tr valign="top">
<td class="cellrowborder" valign="top" headers="d8660e85 ">
<p><samp class="codeph"> void swap( T& x, T& y )</samp>
</p>
</td>
<td class="row-nocellborder" valign="top" headers="d8660e91 ">
<p> Swap <samp class="codeph">x</samp> and <samp class="codeph">y</samp> .</p>
</td>
</tr>
<tr valign="top">
<td class="cellrowborder" valign="top" headers="d8660e85 ">
<p><samp class="codeph"> bool Compare::operator()(
const T& x, const T& y
)</samp>
</p>
</td>
<td class="row-nocellborder" valign="top" headers="d8660e91 ">
<p> True if <samp class="codeph">x</samp> comes before <samp class="codeph">y</samp> ; false
otherwise.</p>
</td>
</tr>
</tbody>
</table>
</div>
<p>A call <samp class="codeph">parallel_sort(i,j,comp)</samp> sorts the <samp class="codeph">sequence [i,j)</samp> using
the argument <samp class="codeph">comp</samp> to determine relative orderings. If
<samp class="codeph">comp(x,y)</samp> returns <samp class="codeph">true</samp> then <samp class="codeph">x</samp> appears before <samp class="codeph">y</samp> in the sorted
sequence.</p>
<p>A call <samp class="codeph">parallel_sort(i,j)</samp> is equivalent to
<samp class="codeph">parallel_sort(i,j,std::less<T>)</samp>.</p>
<p> <strong>Complexity</strong></p>
<p><samp class="codeph"> parallel_sort</samp> is comparison sort with an average time complexity of <em>O(N
log (N))</em>, where <em>N</em> is the number of elements in the sequence. When
worker threads are available, <samp class="codeph">parallel_sort</samp> creates subtasks that may be
executed concurrently, leading to improved execution times.</p>
<p><strong>Example</strong></p>
<p>The following example shows two sorts. The sort of array <samp class="codeph">a</samp> uses the default
comparison, which sorts in ascending order. The sort of array <samp class="codeph">b</samp> sorts in descending order by
using <samp class="codeph">std::greater<float></samp> for comparison.</p>
<pre>#include "tbb/parallel_sort.h"
#include <math.h>
using namespace tbb;
const int N = 100000;
float a[N];
float b[N];
void SortExample() {
for( int i = 0; i < N; i++ ) {
a[i] = sin((double)i);
b[i] = cos((double)i);
}
parallel_sort(a, a + N);
parallel_sort(b, b + N, std::greater<float>());
}
</pre></div>
</div>
<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="../../reference/algorithms.htm">Algorithms</a></div>
</div>
<div class="See Also">
<h2>See Also</h2>
<div class="linklist">
<div><a href="../task_scheduler/task_scheduler_init_cls.htm">task_scheduler_init
class</a></div></div>
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