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<!DOCTYPE html>

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<title>Taskflow Algorithms » Parallel Sort | Taskflow QuickStart</title>

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<h1>

<a href="Algorithms.html">Taskflow Algorithms</a> »

Parallel Sort

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<h3>Contents</h3>

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<li><a href="#ParallelSortInclude">Include the Header</a></li>

<li><a href="#SortARangeOfItems">Sort a Range of Items</a></li>

<li><a href="#SortARangeOfItemsWithACustomComparator">Sort a Range of Items with a Custom Comparator</a></li>

<li><a href="#ParallelSortEnableStatefulDataPassing">Enable Stateful Data Passing</a></li>

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Taskflow provides template functions for constructing tasks to sort ranges of items in parallel.<section id="ParallelSortInclude"><h2><a href="#ParallelSortInclude">Include the Header</a></h2>You need to include the header file, <code>taskflow/algorithm/sort.hpp</code>, for creating a parallel-sort task.<pre class="m-code">#include <taskflow/algorithm/sort.hpp></pre></section><section id="SortARangeOfItems"><h2><a href="#SortARangeOfItems">Sort a Range of Items</a></h2>The task created by <a href="classtf_1_1FlowBuilder.html#a7d844e9856c7c65b26ccdb83ffdab1d6" class="m-doc">tf::Taskflow::sort(B first, E last)</a> performs parallel sort to rank a range of elements specified by <code>[first, last)</code> in increasing order. The given iterators must be random-accessible. The following example creates a task to sort a data vector in increasing order.<pre class="m-code">tf::Taskflow taskflow;

tf::Executor executor;

std::vector<int> data = {1, 4, 9, 2, 3, 11, -8};

tf::Task sort = taskflow.sort(data.begin(), data.end());

executor.run(taskflow).wait();

tf::Executor executor;

[](int a, int b) { return a > b; }

);

assert(std::is_sorted(data.begin(), data.end(), std::greater<int>{}));</pre><aside class="m-note m-info"><h4>Note</h4><a href="classtf_1_1FlowBuilder.html#a35e180eb63de6c9f28e43185e837a4fa" class="m-doc">tf::Taskflow::sort</a> is not stable. That is, two or more objects with equal keys may not appear in the same order before sorting.</aside></section><section id="ParallelSortEnableStatefulDataPassing"><h2><a href="#ParallelSortEnableStatefulDataPassing">Enable Stateful Data Passing</a></h2>The iterators taken by <a href="classtf_1_1FlowBuilder.html#a35e180eb63de6c9f28e43185e837a4fa" class="m-doc">tf::Taskflow::sort</a> are templated. You can use <a href="http://en.cppreference.com/w/cpp/utility/functional/reference_wrapper.html" class="m-doc-external">std::reference_wrapper</a> to enable stateful data passing between the sort task and others. The following example creates a task <code>init</code> to initialize the data vector and a task <code>sort</code> to sort the data in parallel after <code>init</code> finishes.<pre class="m-code">tf::Taskflow taskflow;

tf::Executor executor;

std::vector<int>::iterator first, last;

tf::Task init = taskflow.emplace([&](){

data = {1, 4, 9, 2, 3, 11, -8};

first = data.begin();

last = data.end();

});

std::ref(first), std::ref(last), [] (int l, int r) { return l < r; }

);

init.precede(sort);

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Taskflow handbook is part of the <a href="https://taskflow.github.io">Taskflow project</a>, copyright © <a href="https://tsung-wei-huang.github.io/">Dr. Tsung-Wei Huang</a>, 2018–2022. Generated by <a href="https://doxygen.org/">Doxygen</a> 1.8.14 and <a href="https://mcss.mosra.cz/">m.css</a>.

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