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<p class='location'>Crate crossbeam_deque</p><div class="sidebar-elems"><div class="block items"><ul><li><a href="#structs">Structs</a></li><li><a href="#enums">Enums</a></li></ul></div><p class='location'></p><script>window.sidebarCurrent = {name: 'crossbeam_deque', ty: 'mod', relpath: '../'};</script></div>
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<h1 class='fqn'><span class='in-band'>Crate <a class="mod" href=''>crossbeam_deque</a></span><span class='out-of-band'><span id='render-detail'>
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<a id="toggle-all-docs" href="javascript:void(0)" title="collapse all docs">
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[<span class='inner'>−</span>]
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</span><a class='srclink' href='../src/crossbeam_deque/lib.rs.html#1-1136' title='goto source code'>[src]</a></span></h1>
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<div class='docblock'><p>A concurrent work-stealing deque.</p>
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<p>The data structure can be thought of as a dynamically growable and shrinkable buffer that has
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two ends: bottom and top. A <a href="struct.Deque.html"><code>Deque</code></a> can <a href="struct.Deque.html#method.push"><code>push</code></a> elements into the bottom and <a href="struct.Deque.html#method.pop"><code>pop</code></a>
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elements from the bottom, but it can only <a href="struct.Deque.html#method.steal"><code>steal</code></a> elements from the top.</p>
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<p>A <a href="struct.Deque.html"><code>Deque</code></a> doesn't implement <code>Sync</code> so it cannot be shared among multiple threads. However, it
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can create <a href="struct.Stealer.html"><code>Stealer</code></a>s, and those can be easily cloned, shared, and sent to other threads.
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<a href="struct.Stealer.html"><code>Stealer</code></a>s can only <a href="struct.Stealer.html#method.steal"><code>steal</code></a> elements from the top.</p>
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<p>Here's a visualization of the data structure:</p>
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<pre><code class="language-text"> top
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_
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Deque::steal -> | | <- Stealer::steal
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| |
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| |
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| |
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Deque::push/pop -> |_|
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bottom
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</code></pre>
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<h1 id="work-stealing-schedulers" class="section-header"><a href="#work-stealing-schedulers">Work-stealing schedulers</a></h1>
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<p>Usually, the data structure is used in work-stealing schedulers as follows.</p>
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<p>There is a number of threads. Each thread owns a <a href="struct.Deque.html"><code>Deque</code></a> and creates a <a href="struct.Stealer.html"><code>Stealer</code></a> that is
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shared among all other threads. Alternatively, it creates multiple <a href="struct.Stealer.html"><code>Stealer</code></a>s - one for each
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of the other threads.</p>
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<p>Then, all threads are executing in a loop. In the loop, each one attempts to <a href="struct.Deque.html#method.pop"><code>pop</code></a> some work
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from its own <a href="struct.Deque.html"><code>Deque</code></a>. But if it is empty, it attempts to <a href="struct.Stealer.html#method.steal"><code>steal</code></a> work from
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some other thread instead. When executing work (or being idle), a thread may produce more work,
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which gets <a href="struct.Deque.html#method.push"><code>push</code></a>ed into its <a href="struct.Deque.html"><code>Deque</code></a>.</p>
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<p>Of course, there are many variations of this strategy. For example, sometimes it may be
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beneficial for a thread to always <a href="struct.Deque.html#method.steal"><code>steal</code></a> work from the top of its deque
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instead of calling <a href="struct.Deque.html#method.pop"><code>pop</code></a> and taking it from the bottom.</p>
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<h1 id="examples" class="section-header"><a href="#examples">Examples</a></h1>
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<pre class="rust rust-example-rendered">
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<span class="kw">use</span> <span class="ident">crossbeam_deque</span>::{<span class="ident">Deque</span>, <span class="ident">Steal</span>};
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<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">thread</span>;
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<span class="kw">let</span> <span class="ident">d</span> <span class="op">=</span> <span class="ident">Deque</span>::<span class="ident">new</span>();
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<span class="kw">let</span> <span class="ident">s</span> <span class="op">=</span> <span class="ident">d</span>.<span class="ident">stealer</span>();
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<span class="ident">d</span>.<span class="ident">push</span>(<span class="string">'a'</span>);
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<span class="ident">d</span>.<span class="ident">push</span>(<span class="string">'b'</span>);
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<span class="ident">d</span>.<span class="ident">push</span>(<span class="string">'c'</span>);
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">d</span>.<span class="ident">pop</span>(), <span class="prelude-val">Some</span>(<span class="string">'c'</span>));
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<span class="ident">drop</span>(<span class="ident">d</span>);
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<span class="ident">thread</span>::<span class="ident">spawn</span>(<span class="kw">move</span> <span class="op">||</span> {
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">steal</span>(), <span class="ident">Steal</span>::<span class="ident">Data</span>(<span class="string">'a'</span>));
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<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">s</span>.<span class="ident">steal</span>(), <span class="ident">Steal</span>::<span class="ident">Data</span>(<span class="string">'b'</span>));
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}).<span class="ident">join</span>().<span class="ident">unwrap</span>();</pre>
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<h1 id="references" class="section-header"><a href="#references">References</a></h1>
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<p>The implementation is based on the following work:</p>
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<ol>
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<li><a href="https://dl.acm.org/citation.cfm?id=1073974">Chase and Lev. Dynamic circular work-stealing deque. SPAA 2005.</a></li>
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<li><a href="https://dl.acm.org/citation.cfm?id=2442524">Le, Pop, Cohen, and Nardelli. Correct and efficient work-stealing for weak memory models.
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PPoPP 2013.</a></li>
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<li><a href="https://dl.acm.org/citation.cfm?id=2509514">Norris and Demsky. CDSchecker: checking concurrent data structures written with C/C++
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atomics. OOPSLA 2013.</a></li>
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</ol>
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</div><h2 id='structs' class='section-header'><a href="#structs">Structs</a></h2>
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<table>
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<tr class=' module-item'>
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<td><a class="struct" href="struct.Deque.html"
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title='struct crossbeam_deque::Deque'>Deque</a></td>
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<td class='docblock-short'>
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<p>A concurrent work-stealing deque.</p>
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</td>
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</tr>
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<tr class=' module-item'>
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<td><a class="struct" href="struct.Stealer.html"
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title='struct crossbeam_deque::Stealer'>Stealer</a></td>
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<td class='docblock-short'>
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<p>A stealer that steals elements from the top of a deque.</p>
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<td><a class="enum" href="enum.Steal.html"
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title='enum crossbeam_deque::Steal'>Steal</a></td>
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<td class='docblock-short'>
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<p>Possible outcomes of a steal operation.</p>
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