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ParallelTransforms.html

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<!DOCTYPE html>
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 <a href="Algorithms.html">Taskflow Algorithms</a> &raquo;
 Parallel Transforms
 </h1>
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 <h3>Contents</h3>
 <ul>
 <li><a href="#ParallelTransformsInclude">Include the Header</a></li>
 <li><a href="#ParallelTransformsOverARange">Create a Unary Parallel-Transform Task</a></li>
 <li><a href="#ParallelTransformsCaptureIteratorsByReference">Capture Iterators by Reference</a></li>
 <li><a href="#ParallelBinaryTransformsOverARange">Create a Binary Parallel-Transform Task</a></li>
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Taskflow provides template functions for constructing tasks to perform parallel transforms over ranges of items.<section id="ParallelTransformsInclude"><h2><a href="#ParallelTransformsInclude">Include the Header</a></h2>You need to include the header file, <code>taskflow/algorithm/transform.hpp</code>, for creating a parallel-transform task.<pre class="m-code">#include &lt;taskflow/algorithm/transform.hpp&gt;</pre></section><section id="ParallelTransformsOverARange"><h2><a href="#ParallelTransformsOverARange">Create a Unary Parallel-Transform Task</a></h2>Parallel-transform transforms a range of items, possibly with a different type for the transformed data, and stores the result in another range. The task created by <a href="classtf_1_1FlowBuilder.html#ab2db36500ea85146772acc75fc586ced" class="m-doc">tf::Taskflow::transform(B first1, E last1, O d_first, C c, P&amp;&amp; part)</a> is equivalent to a parallel execution of the following loop:<pre class="m-code">while (first1 != last1) {
 *d_first++ = c(*first1++);
}</pre><a href="classtf_1_1FlowBuilder.html#ab2db36500ea85146772acc75fc586ced" class="m-doc">tf::Taskflow::transform</a> simultaneously applies the callable <code>c</code> to the object obtained by dereferencing every iterator in the range <code>[first1, last1)</code> and stores the result in another range beginning at <code>d_first</code>. It is user&#x27;s responsibility for ensuring the range is valid within the execution of the parallel-transform task.<pre class="m-code">std::vector&lt;int&gt; src = {1, 2, 3, 4, 5};
std::vector&lt;int&gt; tgt(src.size());
taskflow.transform(src.begin(), src.end(), tgt.begin(), [](int i){ 
 std::cout &lt;&lt; &quot;transforming item &quot; &lt;&lt; i &lt;&lt; &quot; to &quot; &lt;&lt; i + 1 &lt;&lt; &#39;\n&#39;;
 return i + 1;
});</pre></section><section id="ParallelTransformsCaptureIteratorsByReference"><h2><a href="#ParallelTransformsCaptureIteratorsByReference">Capture Iterators by Reference</a></h2>You can pass iterators by reference using <a href="https://en.cppreference.com/w/cpp/utility/functional/ref">std::ref</a> to marshal parameter update between dependent tasks. This is especially useful when the range is unknown at the time of creating a parallel-transform task, but needs initialization from another task.<pre class="m-code">std::vector&lt;int&gt; src, tgt;
std::vector&lt;int&gt;::iterator first, last, d_first;

tf::Task init = taskflow.emplace([&amp;](){
 src.resize(1000);
 tgt.resize(1000);
 first = src.begin();
 last = src.end();
 d_first = tgt.begin();
});

tf::Task transform = taskflow.for_each(
 std::ref(first), std::ref(last), std::ref(d_first), 
 [&amp;](int i) {
 std::cout &lt;&lt; &quot;transforming item &quot; &lt;&lt; i &lt;&lt; &quot; to &quot; &lt;&lt; i + 1 &lt;&lt; &#39;\n&#39;;
 return i+1;
 }
);

init.precede(transform);</pre>When <code>init</code> finishes, the parallel-transform task <code>transform</code> will see <code>first</code> pointing to the beginning of <code>src</code> and <code>last</code> pointing to the end of <code>src</code>. Then, it simultaneously transforms these 1000 items by adding one to each element and stores the result in another range starting at <code>d_first</code>.</section><section id="ParallelBinaryTransformsOverARange"><h2><a href="#ParallelBinaryTransformsOverARange">Create a Binary Parallel-Transform Task</a></h2>You can use the overload, <a href="classtf_1_1FlowBuilder.html#a519ca8f909c86efdc70fa01f28156219" class="m-doc">tf::Taskflow::transform(B1 first1, E1 last1, B2 first2, O d_first, C c, P&amp;&amp; part)</a>, to perform parallel transforms on two source ranges pointed by <code>first1</code> and <code>first2</code> using the binary operator <code>c</code> and store the result in another range pointed by <code>d_first</code>. This method is equivalent to the parallel execution of the following loop:<pre class="m-code">while (first1 != last1) {
 *d_first++ = c(*first1++, *first2++);
}</pre>The following example creates a parallel-transform task that adds two ranges of elements one by one and stores the result in a target range:<pre class="m-code">std::vector&lt;int&gt; src1 = {1, 2, 3, 4, 5};
std::vector&lt;int&gt; src2 = {5, 4, 3, 2, 1};
std::vector&lt;int&gt; tgt(src1.size());
taskflow.transform(
 src1.begin(), src1.end(), src2.begin(), tgt.begin(), 
 [](int i, int j){ 
 return i + j;
 }
);</pre></section><section id="ParallelTransformsCfigureAPartitioner"><h2><a href="#ParallelTransformsCfigureAPartitioner">Configure a Partitioner</a></h2>You can configure a partitioner for parallel-transform tasks to run with different scheduling methods, such as guided partitioning, dynamic partitioning, and static partitioning. The following example creates two parallel-transform tasks using two different partitioners, one with the static partitioning algorithm and another one with the guided partitioning algorithm:<pre class="m-code">tf::StaticPartitioner static_partitioner;
tf::GuidedPartitioner guided_partitioner;

std::vector&lt;int&gt; src1 = {1, 2, 3, 4, 5};
std::vector&lt;int&gt; src2 = {5, 4, 3, 2, 1};
std::vector&lt;int&gt; tgt1(src1.size());
std::vector&lt;int&gt; tgt2(src2.size());

// create a parallel-transform task with static execution partitioner
taskflow.transform(
 src1.begin(), src1.end(), src2.begin(), tgt1.begin(), 
 [](int i, int j){ 
 return i + j;
 },
 static_partitioner
);

// create a parallel-transform task with guided execution partitioner
taskflow.transform(
 src1.begin(), src1.end(), src2.begin(), tgt2.begin(), 
 [](int i, int j){ 
 return i + j;
 },
 guided_partitioner
);</pre><aside class="m-note m-info"><h4>Note</h4>By default, parallel-transform tasks use <a href="namespacetf.html#a77d193108ae375fdfc554e7f10bea23e" class="m-doc">tf::DefaultPartitioner</a> if no partitioner is specified.</aside></section>
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TSUNG-WEI HUANG authored 2023年09月28日 06:51 +08:00 . updated exception doc

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<!DOCTYPE html>
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 <meta charset="UTF-8" />
 <title>Taskflow Algorithms &raquo; Parallel Transforms | Taskflow QuickStart</title>
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 <span class="m-breadcrumb"><a href="Algorithms.html">Taskflow Algorithms</a> &raquo;</span>
 Parallel Transforms
 </h1>
 <nav class="m-block m-default">
 <h3>Contents</h3>
 <ul>
 <li><a href="#ParallelTransformsInclude">Include the Header</a></li>
 <li><a href="#ParallelTransformsOverARange">Create a Unary Parallel-Transform Task</a></li>
 <li><a href="#ParallelTransformsCaptureIteratorsByReference">Capture Iterators by Reference</a></li>
 <li><a href="#ParallelBinaryTransformsOverARange">Create a Binary Parallel-Transform Task</a></li>
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<p>Taskflow provides template functions for constructing tasks to perform parallel transforms over ranges of items.</p><section id="ParallelTransformsInclude"><h2><a href="#ParallelTransformsInclude">Include the Header</a></h2><p>You need to include the header file, <code>taskflow/algorithm/transform.hpp</code>, for creating a parallel-transform task.</p><pre class="m-code"><span class="cp">#include</span><span class="w"> </span><span class="cpf">&lt;taskflow/algorithm/transform.hpp&gt;</span><span class="cp"></span></pre></section><section id="ParallelTransformsOverARange"><h2><a href="#ParallelTransformsOverARange">Create a Unary Parallel-Transform Task</a></h2><p>Parallel-transform transforms a range of items, possibly with a different type for the transformed data, and stores the result in another range. The task created by <a href="classtf_1_1FlowBuilder.html#ab2db36500ea85146772acc75fc586ced" class="m-doc">tf::<wbr />Taskflow::<wbr />transform(B first1, E last1, O d_first, C c, P&amp;&amp; part)</a> is equivalent to a parallel execution of the following loop:</p><pre class="m-code"><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">first1</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">last1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w"> </span><span class="o">*</span><span class="n">d_first</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">c</span><span class="p">(</span><span class="o">*</span><span class="n">first1</span><span class="o">++</span><span class="p">);</span><span class="w"></span>
<span class="p">}</span><span class="w"></span></pre><p><a href="classtf_1_1FlowBuilder.html#ab2db36500ea85146772acc75fc586ced" class="m-doc">tf::<wbr />Taskflow::<wbr />transform</a> simultaneously applies the callable <code>c</code> to the object obtained by dereferencing every iterator in the range <code>[first1, last1)</code> and stores the result in another range beginning at <code>d_first</code>. It is user&#x27;s responsibility for ensuring the range is valid within the execution of the parallel-transform task.</p><pre class="m-code"><span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">src</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="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">tgt</span><span class="p">(</span><span class="n">src</span><span class="p">.</span><span class="n">size</span><span class="p">());</span><span class="w"></span>
<span class="n">taskflow</span><span class="p">.</span><span class="n">transform</span><span class="p">(</span><span class="n">src</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span><span class="w"> </span><span class="n">src</span><span class="p">.</span><span class="n">end</span><span class="p">(),</span><span class="w"> </span><span class="n">tgt</span><span class="p">.</span><span class="n">begin</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="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">cout</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">&quot;transforming item &quot;</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">&quot; to &quot;</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="sc">&#39;\n&#39;</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"></span>
<span class="p">});</span><span class="w"></span></pre></section><section id="ParallelTransformsCaptureIteratorsByReference"><h2><a href="#ParallelTransformsCaptureIteratorsByReference">Capture Iterators by Reference</a></h2><p>You can pass iterators by reference using <a href="https://en.cppreference.com/w/cpp/utility/functional/ref">std::<wbr />ref</a> to marshal parameter update between dependent tasks. This is especially useful when the range is unknown at the time of creating a parallel-transform task, but needs initialization from another task.</p><pre class="m-code"><span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">src</span><span class="p">,</span><span class="w"> </span><span class="n">tgt</span><span class="p">;</span><span class="w"></span>
<span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;::</span><span class="n">iterator</span><span class="w"> </span><span class="n">first</span><span class="p">,</span><span class="w"> </span><span class="n">last</span><span class="p">,</span><span class="w"> </span><span class="n">d_first</span><span class="p">;</span><span class="w"></span>

<span class="n">tf</span><span class="o">::</span><span class="n">Task</span><span class="w"> </span><span class="n">init</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">taskflow</span><span class="p">.</span><span class="n">emplace</span><span class="p">([</span><span class="o">&amp;</span><span class="p">](){</span><span class="w"></span>
<span class="w"> </span><span class="n">src</span><span class="p">.</span><span class="n">resize</span><span class="p">(</span><span class="mi">1000</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">tgt</span><span class="p">.</span><span class="n">resize</span><span class="p">(</span><span class="mi">1000</span><span class="p">);</span><span class="w"></span>
<span class="w"> </span><span class="n">first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">src</span><span class="p">.</span><span class="n">begin</span><span class="p">();</span><span class="w"></span>
<span class="w"> </span><span class="n">last</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">src</span><span class="p">.</span><span class="n">end</span><span class="p">();</span><span class="w"></span>
<span class="w"> </span><span class="n">d_first</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">tgt</span><span class="p">.</span><span class="n">begin</span><span class="p">();</span><span class="w"></span>
<span class="p">});</span><span class="w"></span>

<span class="n">tf</span><span class="o">::</span><span class="n">Task</span><span class="w"> </span><span class="n">transform</span><span class="w"> </span><span class="o">=</span><span class="w"> </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="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">ref</span><span class="p">(</span><span class="n">first</span><span class="p">),</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">ref</span><span class="p">(</span><span class="n">last</span><span class="p">),</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">ref</span><span class="p">(</span><span class="n">d_first</span><span class="p">),</span><span class="w"> </span>
<span class="w"> </span><span class="p">[</span><span class="o">&amp;</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="p">{</span><span class="w"></span>
<span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">cout</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">&quot;transforming item &quot;</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="s">&quot; to &quot;</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="mi">1</span><span class="w"> </span><span class="o">&lt;&lt;</span><span class="w"> </span><span class="sc">&#39;\n&#39;</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="o">+</span><span class="mi">1</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="p">}</span><span class="w"></span>
<span class="p">);</span><span class="w"></span>

<span class="n">init</span><span class="p">.</span><span class="n">precede</span><span class="p">(</span><span class="n">transform</span><span class="p">);</span><span class="w"></span></pre><p>When <code>init</code> finishes, the parallel-transform task <code>transform</code> will see <code>first</code> pointing to the beginning of <code>src</code> and <code>last</code> pointing to the end of <code>src</code>. Then, it simultaneously transforms these 1000 items by adding one to each element and stores the result in another range starting at <code>d_first</code>.</p></section><section id="ParallelBinaryTransformsOverARange"><h2><a href="#ParallelBinaryTransformsOverARange">Create a Binary Parallel-Transform Task</a></h2><p>You can use the overload, <a href="classtf_1_1FlowBuilder.html#a519ca8f909c86efdc70fa01f28156219" class="m-doc">tf::<wbr />Taskflow::<wbr />transform(B1 first1, E1 last1, B2 first2, O d_first, C c, P&amp;&amp; part)</a>, to perform parallel transforms on two source ranges pointed by <code>first1</code> and <code>first2</code> using the binary operator <code>c</code> and store the result in another range pointed by <code>d_first</code>. This method is equivalent to the parallel execution of the following loop:</p><pre class="m-code"><span class="k">while</span><span class="w"> </span><span class="p">(</span><span class="n">first1</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="n">last1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w"> </span><span class="o">*</span><span class="n">d_first</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">c</span><span class="p">(</span><span class="o">*</span><span class="n">first1</span><span class="o">++</span><span class="p">,</span><span class="w"> </span><span class="o">*</span><span class="n">first2</span><span class="o">++</span><span class="p">);</span><span class="w"></span>
<span class="p">}</span><span class="w"></span></pre><p>The following example creates a parallel-transform task that adds two ranges of elements one by one and stores the result in a target range:</p><pre class="m-code"><span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">src1</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="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">src2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">5</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">3</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">1</span><span class="p">};</span><span class="w"></span>
<span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">tgt</span><span class="p">(</span><span class="n">src1</span><span class="p">.</span><span class="n">size</span><span class="p">());</span><span class="w"></span>
<span class="n">taskflow</span><span class="p">.</span><span class="n">transform</span><span class="p">(</span><span class="w"></span>
<span class="w"> </span><span class="n">src1</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span><span class="w"> </span><span class="n">src1</span><span class="p">.</span><span class="n">end</span><span class="p">(),</span><span class="w"> </span><span class="n">src2</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span><span class="w"> </span><span class="n">tgt</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span><span class="w"> </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="kt">int</span><span class="w"> </span><span class="n">j</span><span class="p">){</span><span class="w"> </span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">j</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="p">}</span><span class="w"></span>
<span class="p">);</span><span class="w"></span></pre></section><section id="ParallelTransformsCfigureAPartitioner"><h2><a href="#ParallelTransformsCfigureAPartitioner">Configure a Partitioner</a></h2><p>You can configure a partitioner for parallel-transform tasks to run with different scheduling methods, such as guided partitioning, dynamic partitioning, and static partitioning. The following example creates two parallel-transform tasks using two different partitioners, one with the static partitioning algorithm and another one with the guided partitioning algorithm:</p><pre class="m-code"><span class="n">tf</span><span class="o">::</span><span class="n">StaticPartitioner</span><span class="w"> </span><span class="n">static_partitioner</span><span class="p">;</span><span class="w"></span>
<span class="n">tf</span><span class="o">::</span><span class="n">GuidedPartitioner</span><span class="w"> </span><span class="n">guided_partitioner</span><span class="p">;</span><span class="w"></span>

<span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">src1</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="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">src2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">{</span><span class="mi">5</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">3</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">1</span><span class="p">};</span><span class="w"></span>
<span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">tgt1</span><span class="p">(</span><span class="n">src1</span><span class="p">.</span><span class="n">size</span><span class="p">());</span><span class="w"></span>
<span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span><span class="w"> </span><span class="n">tgt2</span><span class="p">(</span><span class="n">src2</span><span class="p">.</span><span class="n">size</span><span class="p">());</span><span class="w"></span>

<span class="c1">// create a parallel-transform task with static execution partitioner</span>
<span class="n">taskflow</span><span class="p">.</span><span class="n">transform</span><span class="p">(</span><span class="w"></span>
<span class="w"> </span><span class="n">src1</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span><span class="w"> </span><span class="n">src1</span><span class="p">.</span><span class="n">end</span><span class="p">(),</span><span class="w"> </span><span class="n">src2</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span><span class="w"> </span><span class="n">tgt1</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span><span class="w"> </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="kt">int</span><span class="w"> </span><span class="n">j</span><span class="p">){</span><span class="w"> </span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">j</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="p">},</span><span class="w"></span>
<span class="w"> </span><span class="n">static_partitioner</span><span class="w"></span>
<span class="p">);</span><span class="w"></span>

<span class="c1">// create a parallel-transform task with guided execution partitioner</span>
<span class="n">taskflow</span><span class="p">.</span><span class="n">transform</span><span class="p">(</span><span class="w"></span>
<span class="w"> </span><span class="n">src1</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span><span class="w"> </span><span class="n">src1</span><span class="p">.</span><span class="n">end</span><span class="p">(),</span><span class="w"> </span><span class="n">src2</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span><span class="w"> </span><span class="n">tgt2</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span><span class="w"> </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="kt">int</span><span class="w"> </span><span class="n">j</span><span class="p">){</span><span class="w"> </span>
<span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="n">i</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">j</span><span class="p">;</span><span class="w"></span>
<span class="w"> </span><span class="p">},</span><span class="w"></span>
<span class="w"> </span><span class="n">guided_partitioner</span><span class="w"></span>
<span class="p">);</span><span class="w"></span></pre><aside class="m-note m-info"><h4>Note</h4><p>By default, parallel-transform tasks use <a href="namespacetf.html#a77d193108ae375fdfc554e7f10bea23e" class="m-doc">tf::<wbr />DefaultPartitioner</a> if no partitioner is specified.</p></aside></section>
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