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<!DOCTYPE html>

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<title>tf::StaticPartitioner class | Taskflow QuickStart</title>

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<a href="https://taskflow.github.io"><img src="taskflow_logo.png" alt="" />Taskflow</a> <span class="m-breadcrumb">|</span> <a href="index.html" class="m-thin">QuickStart</a>

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<h1>

<div class="m-doc-include m-code m-inverted m-right-m m-text-right"><span class="cp">#include</span> <a class="cpf" href="partitioner_8hpp.html"><taskflow/algorithm/partitioner.hpp></a></div>

<div class="m-doc-template">template<typename C = <a href="structtf_1_1DefaultClosureWrapper.html" class="m-doc">DefaultClosureWrapper</a>></div>

<span class="m-breadcrumb"><a href="namespacetf.html">tf</a>::<wbr/></span>StaticPartitioner <span class="m-thin">class</span>

</h1>

<p>class to construct a static partitioner for scheduling parallel algorithms</p>

<thead>

<tr><th colspan="2">Template parameters</th></tr>

</thead>

<tbody>

<tr>

<td>closure wrapper type (default <a href="structtf_1_1DefaultClosureWrapper.html" class="m-doc">tf::<wbr />DefaultClosureWrapper</a>)</td>

</tr>

</tbody>

</table>

<h3>Contents</h3>

<ul>

<li>

Reference

<ul>

<li><a href="#base-classes">Base classes</a></li>

<li><a href="#pub-static-methods">Public static functions</a></li>

<li><a href="#typeless-methods">Constructors, destructors, conversion operators</a></li>

<li><a href="#pub-methods">Public functions</a></li>

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<p>The partitioner divides iterations into chunks and distributes chunks to workers in order. If the chunk size is not specified (default <code>0</code>), the partitioner resorts to a chunk size that equally distributes iterations into workers.</p><pre class="m-code"><span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">data</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="mi">2</span><span class="p">,</span><span class="w"> </span><span class="mi">3</span><span class="p">,</span><span class="w"> </span><span class="mi">4</span><span class="p">,</span><span class="w"> </span><span class="mi">5</span><span class="p">,</span><span class="w"> </span><span class="mi">6</span><span class="p">,</span><span class="w"> </span><span class="mi">7</span><span class="p">,</span><span class="w"> </span><span class="mi">8</span><span class="p">,</span><span class="w"> </span><span class="mi">9</span><span class="p">,</span><span class="w"> </span><span class="mi">10</span><span class="p">}</span>

<span class="n">taskflow</span><span class="p">.</span><span class="n">for_each</span><span class="p">(</span>

<span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span><span class="w"> </span><span class="n">data</span><span class="p">.</span><span class="n">end</span><span class="p">(),</span><span class="w"> </span><span class="p">[](</span><span class="kt">int</span><span class="w"> </span><span class="n">i</span><span class="p">){},</span><span class="w"> </span><span class="n">StaticPartitioner</span><span class="p">(</span><span class="mi">0</span><span class="p">)</span>

<span class="n">executor</span><span class="p">.</span><span class="n">run</span><span class="p">(</span><span class="n">taskflow</span><span class="p">).</span><span class="n">run</span><span class="p">();</span></pre><p>In addition to partition size, the application can specify a closure wrapper for a static partitioner. A closure wrapper allows the application to wrapper a partitioned task (i.e., closure) with a custom function object that performs additional tasks. For example:</p><pre class="m-code"><span class="n">std</span><span class="o">::</span><span class="n">atomic</span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="w"> </span><span class="n">count</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span>

<span class="n">tf</span><span class="o">::</span><span class="n">Taskflow</span><span class="w"> </span><span class="n">taskflow</span><span class="p">;</span>

<span class="n">taskflow</span><span class="p">.</span><span class="n">for_each_index</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="mi">100</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span>

<span class="w"> </span><span class="n">printf</span><span class="p">(</span><span class="s">"%d</span><span class="se">\n</span><span class="s">"</span><span class="p">,</span><span class="w"> </span><span class="n">i</span><span class="p">);</span><span class="w"> </span>

<span class="w"> </span><span class="n">tf</span><span class="o">::</span><span class="n">StaticPartitioner</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="p">[](</span><span class="k">auto</span><span class="o">&&</span><span class="w"> </span><span class="n">closure</span><span class="p">){</span>

<span class="w"> </span><span class="c1">// do something before invoking the partitioned task</span>

<span class="w"> </span><span class="c1">// invoke the partitioned task</span>

<span class="w"> </span><span class="n">closure</span><span class="p">();</span>

<span class="w"> </span><span class="c1">// do something else after invoking the partitioned task</span>

<h2><a href="#base-classes">Base classes</a></h2>

<dt>

<div class="m-doc-template">template<typename C = <a href="structtf_1_1DefaultClosureWrapper.html" class="m-doc">DefaultClosureWrapper</a>></div>

class <a href="classtf_1_1PartitionerBase.html" class="m-doc">PartitionerBase<DefaultClosureWrapper></a>

</dt>

<dd>class to derive a partitioner for scheduling parallel algorithms</dd>

</dl>

</section>

<h2><a href="#pub-static-methods">Public static functions</a></h2>

<span class="m-doc-wrap-bumper">static auto <a href="#ad6791c126752f2d85f3107ce8b09b784" class="m-doc-self">type</a>(</span><span class="m-doc-wrap">) -> <a href="namespacetf.html#a32d51425fa23cd0dc3518c16cf3bb6c0" class="m-doc">PartitionerType</a> <span class="m-label m-flat m-primary">constexpr</span></span>

</dt>

<dd>queries the partition type (static)</dd>

</dl>

</section>

<h2><a href="#typeless-methods">Constructors, destructors, conversion operators</a></h2>

<span class="m-doc-wrap-bumper"><a href="#a3b8b8040830d1d9f9635090e9af8edf8" class="m-doc-self">StaticPartitioner</a>(</span><span class="m-doc-wrap">) <span class="m-label m-flat m-info">defaulted</span></span>

</dt>

<dd>default constructor</dd>

<span class="m-doc-wrap-bumper"><a href="#aa6dacbd41f721303afe089f65f9f6549" class="m-doc-self">StaticPartitioner</a>(</span><span class="m-doc-wrap">size_t sz) <span class="m-label m-flat m-info">explicit</span> </span>

</dt>

<dd>construct a static partitioner with the given chunk size</dd>

<span class="m-doc-wrap-bumper"><a href="#ac4fb48bea1252246857e11993bee68c6" class="m-doc-self">StaticPartitioner</a>(</span><span class="m-doc-wrap">size_t sz,

C&& closure) <span class="m-label m-flat m-info">explicit</span> </span>

</dt>

<dd>construct a static partitioner with the given chunk size and the closure</dd>

</dl>

</section>

<h2><a href="#pub-methods">Public functions</a></h2>

<dt>

<span class="m-doc-wrap-bumper">auto <a href="#a54a55e0b20f054e215509486bcd5dc1c" class="m-doc">adjusted_chunk_size</a>(</span><span class="m-doc-wrap">size_t N,

size_t W,

size_t w) const -> size_t</span>

</dt>

<dd>queries the adjusted chunk size</dd>

</dl>

</section>

<h2>Function documentation</h2>

<h3>

template<typename C>

</div>

<span class="m-doc-wrap-bumper">size_t tf::<wbr />StaticPartitioner<C>::<wbr /></span><span class="m-doc-wrap"><span class="m-doc-wrap-bumper"><a href="#a54a55e0b20f054e215509486bcd5dc1c" class="m-doc-self">adjusted_chunk_size</a>(</span><span class="m-doc-wrap">size_t N,

size_t W,

size_t w) const</span></span>

</h3>

<p>queries the adjusted chunk size</p>

<p>Returns the given chunk size if it is not zero, or returns <code>N/W + (w < NW)</code>, where <code>N</code> is the number of iterations, <code>W</code> is the number of workers, and <code>w</code> is the worker ID.</p>

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