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        <h1>
          <span class="m-breadcrumb"><a href="Algorithms.html">Taskflow Algorithms</a> &raquo;</span>
          Parallel Scalable Pipeline
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          <h3>Contents</h3>
          <ul>
            <li><a href="#IncludeTheScalablePipelineHeader">Include the Header</a></li>
            <li><a href="#CreateAScalablePipelineModuleTask">Create a Scalable Pipeline Module Task</a></li>
            <li><a href="#ResetAPlaceholderScalablePipeline">Reset a Placeholder Scalable Pipeline</a></li>
            <li><a href="#ScalablePipelineUseOtherIteratorTypes">Use Other Iterator Types</a></li>
            <li><a href="#ParallelScalablePipelineLearnMore">Learn More about Taskflow Pipeline</a></li>
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<p>Unlike <a href="classtf_1_1Pipeline.html" class="m-doc">tf::<wbr />Pipeline</a> (see <a href="ParallelPipeline.html" class="m-doc">Parallel Pipeline</a>) that instantiates all pipes at the construction time, Taskflow provides a scalable alternative called <a href="classtf_1_1ScalablePipeline.html" class="m-doc">tf::<wbr />ScalablePipeline</a> to allow variable assignments of pipes using range iterators. A scalable pipeline is thus more flexible for applications to create a pipeline scheduling framework whose pipeline structure depends on runtime variables.</p><section id="IncludeTheScalablePipelineHeader"><h2><a href="#IncludeTheScalablePipelineHeader">Include the Header</a></h2><p>You need to include the header file, <code>taskflow/algorithm/pipeline.hpp</code>, for creating a scalable pipeline scheduling framework.</p><pre class="m-code"><span class="cp">#include</span> <span class="cpf">&lt;taskflow/algorithm/pipeline.hpp&gt;</span><span class="cp"></span></pre></section><section id="CreateAScalablePipelineModuleTask"><h2><a href="#CreateAScalablePipelineModuleTask">Create a Scalable Pipeline Module Task</a></h2><p>Similar to <a href="classtf_1_1Pipeline.html" class="m-doc">tf::<wbr />Pipeline</a>, <a href="classtf_1_1ScalablePipeline.html" class="m-doc">tf::<wbr />ScalablePipeline</a> is a composable graph object to implement a <em>pipeline scheduling framework</em> in a taskflow. The key difference between <a href="classtf_1_1Pipeline.html" class="m-doc">tf::<wbr />Pipeline</a> and <a href="classtf_1_1ScalablePipeline.html" class="m-doc">tf::<wbr />ScalablePipeline</a> is that a scalable pipeline can accept <em>variable</em> assignments of pipes rather than instantiating all pipes at construction or programming time. Users define a linear range of pipes, each of the same callable type, and apply that range to construct a scalable pipeline. Between successive runs, users can reset the pipeline to a different range of pipes. The following code creates a scalable pipeline that uses four parallel lines to schedule tokens through three serial pipes in the given vector, then resetting that pipeline to a new range of five serial pipes:</p><pre class="m-code"><span class="n">tf</span><span class="o">::</span><span class="n">Taskflow</span> <span class="n">taskflow</span><span class="p">(</span><span class="s">&quot;pipeline&quot;</span><span class="p">);</span>
<span class="n">tf</span><span class="o">::</span><span class="n">Executor</span> <span class="n">executor</span><span class="p">;</span>
<span class="k">const</span> <span class="kt">size_t</span> <span class="n">num_lines</span> <span class="o">=</span> <span class="mi">4</span><span class="p">;</span>
<span class="c1">// create data storage</span>
<span class="n">std</span><span class="o">::</span><span class="n">array</span><span class="o">&lt;</span><span class="kt">int</span><span class="p">,</span> <span class="n">num_lines</span><span class="o">&gt;</span> <span class="n">buffer</span><span class="p">;</span>
<span class="c1">// define the pipe callable</span>
<span class="k">auto</span> <span class="n">pipe_callable</span> <span class="o">=</span> <span class="p">[</span><span class="o">&amp;</span><span class="n">buffer</span><span class="p">]</span> <span class="p">(</span><span class="n">tf</span><span class="o">::</span><span class="n">Pipeflow</span><span class="o">&amp;</span> <span class="n">pf</span><span class="p">)</span> <span class="k">mutable</span> <span class="p">{</span>
  <span class="k">switch</span><span class="p">(</span><span class="n">pf</span><span class="p">.</span><span class="n">pipe</span><span class="p">())</span> <span class="p">{</span>
    <span class="c1">// first stage generates only 5 scheduling tokens and saves the </span>
    <span class="c1">// token number into the buffer.</span>
    <span class="k">case</span> <span class="mi">0</span><span class="o">:</span> <span class="p">{</span>
      <span class="k">if</span><span class="p">(</span><span class="n">pf</span><span class="p">.</span><span class="n">token</span><span class="p">()</span> <span class="o">==</span> <span class="mi">5</span><span class="p">)</span> <span class="p">{</span>
        <span class="n">pf</span><span class="p">.</span><span class="n">stop</span><span class="p">();</span>
      <span class="p">}</span>
      <span class="k">else</span> <span class="p">{</span>
        <span class="n">printf</span><span class="p">(</span><span class="s">&quot;stage 1: input token = %zu</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">,</span> <span class="n">pf</span><span class="p">.</span><span class="n">token</span><span class="p">());</span>
        <span class="n">buffer</span><span class="p">[</span><span class="n">pf</span><span class="p">.</span><span class="n">line</span><span class="p">()]</span> <span class="o">=</span> <span class="n">pf</span><span class="p">.</span><span class="n">token</span><span class="p">();</span>
      <span class="p">}</span>
      <span class="k">return</span><span class="p">;</span>
    <span class="p">}</span>
    <span class="k">break</span><span class="p">;</span>
    <span class="c1">// other stages propagate the previous result to this pipe and</span>
    <span class="c1">// increment it by one</span>
    <span class="k">default</span><span class="o">:</span> <span class="p">{</span>
      <span class="n">printf</span><span class="p">(</span>
        <span class="s">&quot;stage %zu: input buffer[%zu] = %d</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">,</span> <span class="n">pf</span><span class="p">.</span><span class="n">pipe</span><span class="p">(),</span> <span class="n">pf</span><span class="p">.</span><span class="n">line</span><span class="p">(),</span> <span class="n">buffer</span><span class="p">[</span><span class="n">pf</span><span class="p">.</span><span class="n">line</span><span class="p">()]</span>
      <span class="p">);</span>
      <span class="n">buffer</span><span class="p">[</span><span class="n">pf</span><span class="p">.</span><span class="n">line</span><span class="p">()]</span> <span class="o">=</span> <span class="n">buffer</span><span class="p">[</span><span class="n">pf</span><span class="p">.</span><span class="n">line</span><span class="p">()]</span> <span class="o">+</span> <span class="mi">1</span><span class="p">;</span>
    <span class="p">}</span> 
    <span class="k">break</span><span class="p">;</span>
  <span class="p">}</span>
<span class="p">};</span>
<span class="c1">// create a vector of three pipes</span>
<span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span> <span class="n">tf</span><span class="o">::</span><span class="n">Pipe</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">function</span><span class="o">&lt;</span><span class="kt">void</span><span class="p">(</span><span class="n">tf</span><span class="o">::</span><span class="n">Pipeflow</span><span class="o">&amp;</span><span class="p">)</span><span class="o">&gt;&gt;</span> <span class="o">&gt;</span> <span class="n">pipes</span><span class="p">;</span>
<span class="k">for</span><span class="p">(</span><span class="kt">size_t</span> <span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="n">i</span><span class="o">&lt;</span><span class="mi">3</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
  <span class="n">pipes</span><span class="p">.</span><span class="n">emplace_back</span><span class="p">(</span><span class="n">tf</span><span class="o">::</span><span class="n">PipeType</span><span class="o">::</span><span class="n">SERIAL</span><span class="p">,</span> <span class="n">pipe_callable</span><span class="p">);</span>
<span class="p">}</span>
<span class="c1">// create a pipeline of four parallel lines based on the given vector of pipes</span>
<span class="n">tf</span><span class="o">::</span><span class="n">ScalablePipeline</span> <span class="n">pl</span><span class="p">(</span><span class="n">num_lines</span><span class="p">,</span> <span class="n">pipes</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span> <span class="n">pipes</span><span class="p">.</span><span class="n">end</span><span class="p">());</span>
<span class="c1">// build the pipeline graph using composition</span>
<span class="n">tf</span><span class="o">::</span><span class="n">Task</span> <span class="n">init</span> <span class="o">=</span> <span class="n">taskflow</span><span class="p">.</span><span class="n">emplace</span><span class="p">([](){</span> <span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;ready</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">;</span> <span class="p">})</span>
                        <span class="p">.</span><span class="n">name</span><span class="p">(</span><span class="s">&quot;starting pipeline&quot;</span><span class="p">);</span>
<span class="n">tf</span><span class="o">::</span><span class="n">Task</span> <span class="n">task</span> <span class="o">=</span> <span class="n">taskflow</span><span class="p">.</span><span class="n">composed_of</span><span class="p">(</span><span class="n">pl</span><span class="p">)</span>
                        <span class="p">.</span><span class="n">name</span><span class="p">(</span><span class="s">&quot;pipeline&quot;</span><span class="p">);</span>
<span class="n">tf</span><span class="o">::</span><span class="n">Task</span> <span class="n">stop</span> <span class="o">=</span> <span class="n">taskflow</span><span class="p">.</span><span class="n">emplace</span><span class="p">([](){</span> <span class="n">std</span><span class="o">::</span><span class="n">cout</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;stopped</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">;</span> <span class="p">})</span>
                        <span class="p">.</span><span class="n">name</span><span class="p">(</span><span class="s">&quot;pipeline stopped&quot;</span><span class="p">);</span>
<span class="c1">// create task dependency</span>
<span class="n">init</span><span class="p">.</span><span class="n">precede</span><span class="p">(</span><span class="n">task</span><span class="p">);</span>
<span class="n">task</span><span class="p">.</span><span class="n">precede</span><span class="p">(</span><span class="n">stop</span><span class="p">);</span>
<span class="c1">// dump the pipeline graph structure (with composition)</span>
<span class="n">taskflow</span><span class="p">.</span><span class="n">dump</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">cout</span><span class="p">);</span>
<span class="c1">// run the pipeline</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">wait</span><span class="p">();</span>
<span class="c1">// reset the pipeline to a new range of five pipes and starts from</span>
<span class="c1">// the initial state (i.e., token counts from zero)</span>
<span class="k">for</span><span class="p">(</span><span class="kt">size_t</span> <span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="n">i</span><span class="o">&lt;</span><span class="mi">2</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
  <span class="n">pipes</span><span class="p">.</span><span class="n">emplace_back</span><span class="p">(</span><span class="n">tf</span><span class="o">::</span><span class="n">PipeType</span><span class="o">::</span><span class="n">SERIAL</span><span class="p">,</span> <span class="n">pipe_callable</span><span class="p">);</span>
<span class="p">}</span>
<span class="n">pl</span><span class="p">.</span><span class="n">reset</span><span class="p">(</span><span class="n">pipes</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span> <span class="n">pipes</span><span class="p">.</span><span class="n">end</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">wait</span><span class="p">();</span></pre><p>The program defines a uniform pipe type of <code>tf::Pipe&lt;std::function&lt;void(tf::Pipeflow&amp;)&gt;&gt;</code> and keep all pipes in a vector that is amenable to change. Then, it constructs a scalable pipeline using two range iterators, <code>[first, last)</code>, that point to the beginning and the end of the pipe vector, resulting in a pipeline of three serial stages:</p><div class="m-graph"><svg style="width: 22.250rem; height: 18.438rem;" viewBox="0.00 0.00 356.00 295.08">
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<title>p21&#45;&gt;p31</title>
<path d="M174,-88.4144C174,-80.6303 174,-71.4246 174,-62.8383"/>
<polygon points="177.5001,-62.8093 174,-52.8093 170.5001,-62.8094 177.5001,-62.8093"/>
<g class="m-node m-flat">
<title>p22</title>
<ellipse cx="285" cy="-107.1543" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="285" y="-103.3543">pipe&#45;2</text>
<g class="m-edge">
<title>p21&#45;&gt;p22</title>
<path d="M220.8281,-107.1543C223.1703,-107.1543 225.5125,-107.1543 227.8548,-107.1543"/>
<polygon points="228.1245,-110.6544 238.1245,-107.1543 228.1244,-103.6544 228.1245,-110.6544"/>
<g class="m-node m-flat">
<title>p32</title>
<ellipse cx="285" cy="-34.3848" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="285" y="-30.5848">pipe&#45;2</text>
<g class="m-edge">
<title>p31&#45;&gt;p32</title>
<path d="M220.8281,-34.3848C223.1703,-34.3848 225.5125,-34.3848 227.8548,-34.3848"/>
<polygon points="228.1245,-37.8849 238.1245,-34.3848 228.1244,-30.8849 228.1245,-37.8849"/>
<g class="m-edge">
<title>p02&#45;&gt;p12</title>
<path d="M285,-233.9535C285,-226.1694 285,-216.9637 285,-208.3774"/>
<polygon points="288.5001,-208.3484 285,-198.3484 281.5001,-208.3485 288.5001,-208.3484"/>
<g class="m-edge">
<title>p12&#45;&gt;p22</title>
<path d="M285,-161.1839C285,-153.3999 285,-144.1942 285,-135.6079"/>
<polygon points="288.5001,-135.5788 285,-125.5789 281.5001,-135.5789 288.5001,-135.5788"/>
<g class="m-edge">
<title>p22&#45;&gt;p32</title>
<path d="M285,-88.4144C285,-80.6303 285,-71.4246 285,-62.8383"/>
<polygon points="288.5001,-62.8093 285,-52.8093 281.5001,-62.8094 288.5001,-62.8093"/>
</div><p>Then, the program appends another two pipes into the vector and resets the pipeline to the new range of two additional pipes, resulting in a pipeline of five serial stages:</p><div class="m-graph"><svg style="width: 36.125rem; height: 18.438rem;" viewBox="0.00 0.00 578.00 295.08">
<g transform="scale(1 1) rotate(0) translate(4 291.0782)">
<title>Taskflow</title>
<g class="m-cluster">
<title>cluster0</title>
<polygon stroke-dasharray="5,2" points="8,-226.3087 8,-279.0782 562,-279.0782 562,-226.3087 8,-226.3087"/>
<g class="m-cluster">
<title>cluster1</title>
<polygon stroke-dasharray="5,2" points="8,-153.5391 8,-206.3087 562,-206.3087 562,-153.5391 8,-153.5391"/>
<g class="m-cluster">
<title>cluster2</title>
<polygon stroke-dasharray="5,2" points="8,-80.7696 8,-133.5391 562,-133.5391 562,-80.7696 8,-80.7696"/>
<g class="m-cluster">
<title>cluster3</title>
<polygon stroke-dasharray="5,2" points="8,-8 8,-60.7696 562,-60.7696 562,-8 8,-8"/>
<g class="m-node m-flat">
<title>p00</title>
<ellipse cx="63" cy="-252.6934" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="63" y="-248.8934">pipe&#45;0</text>
<g class="m-node m-flat">
<title>p10</title>
<ellipse cx="63" cy="-179.9239" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="63" y="-176.1239">pipe&#45;0</text>
<g class="m-edge">
<title>p00&#45;&gt;p10</title>
<path d="M63,-233.9535C63,-226.1694 63,-216.9637 63,-208.3774"/>
<polygon points="66.5001,-208.3484 63,-198.3484 59.5001,-208.3485 66.5001,-208.3484"/>
<g class="m-node m-flat">
<title>p01</title>
<ellipse cx="174" cy="-252.6934" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="174" y="-248.8934">pipe&#45;1</text>
<g class="m-edge">
<title>p00&#45;&gt;p01</title>
<path d="M109.8281,-252.6934C112.1703,-252.6934 114.5125,-252.6934 116.8548,-252.6934"/>
<polygon points="117.1245,-256.1935 127.1245,-252.6934 117.1244,-249.1935 117.1245,-256.1935"/>
<g class="m-node m-flat">
<title>p20</title>
<ellipse cx="63" cy="-107.1543" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="63" y="-103.3543">pipe&#45;0</text>
<g class="m-edge">
<title>p10&#45;&gt;p20</title>
<path d="M63,-161.1839C63,-153.3999 63,-144.1942 63,-135.6079"/>
<polygon points="66.5001,-135.5788 63,-125.5789 59.5001,-135.5789 66.5001,-135.5788"/>
<g class="m-node m-flat">
<title>p11</title>
<ellipse cx="174" cy="-179.9239" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="174" y="-176.1239">pipe&#45;1</text>
<g class="m-edge">
<title>p10&#45;&gt;p11</title>
<path d="M109.8281,-179.9239C112.1703,-179.9239 114.5125,-179.9239 116.8548,-179.9239"/>
<polygon points="117.1245,-183.424 127.1245,-179.9239 117.1244,-176.424 117.1245,-183.424"/>
<g class="m-node m-flat">
<title>p30</title>
<ellipse cx="63" cy="-34.3848" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="63" y="-30.5848">pipe&#45;0</text>
<g class="m-edge">
<title>p20&#45;&gt;p30</title>
<path d="M63,-88.4144C63,-80.6303 63,-71.4246 63,-62.8383"/>
<polygon points="66.5001,-62.8093 63,-52.8093 59.5001,-62.8094 66.5001,-62.8093"/>
<g class="m-node m-flat">
<title>p21</title>
<ellipse cx="174" cy="-107.1543" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="174" y="-103.3543">pipe&#45;1</text>
<g class="m-edge">
<title>p20&#45;&gt;p21</title>
<path d="M109.8281,-107.1543C112.1703,-107.1543 114.5125,-107.1543 116.8548,-107.1543"/>
<polygon points="117.1245,-110.6544 127.1245,-107.1543 117.1244,-103.6544 117.1245,-110.6544"/>
<g class="m-node m-flat">
<title>p31</title>
<ellipse cx="174" cy="-34.3848" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="174" y="-30.5848">pipe&#45;1</text>
<g class="m-edge">
<title>p30&#45;&gt;p31</title>
<path d="M109.8281,-34.3848C112.1703,-34.3848 114.5125,-34.3848 116.8548,-34.3848"/>
<polygon points="117.1245,-37.8849 127.1245,-34.3848 117.1244,-30.8849 117.1245,-37.8849"/>
<g class="m-edge">
<title>p01&#45;&gt;p11</title>
<path d="M174,-233.9535C174,-226.1694 174,-216.9637 174,-208.3774"/>
<polygon points="177.5001,-208.3484 174,-198.3484 170.5001,-208.3485 177.5001,-208.3484"/>
<g class="m-node m-flat">
<title>p02</title>
<ellipse cx="285" cy="-252.6934" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="285" y="-248.8934">pipe&#45;2</text>
<g class="m-edge">
<title>p01&#45;&gt;p02</title>
<path d="M220.8281,-252.6934C223.1703,-252.6934 225.5125,-252.6934 227.8548,-252.6934"/>
<polygon points="228.1245,-256.1935 238.1245,-252.6934 228.1244,-249.1935 228.1245,-256.1935"/>
<g class="m-edge">
<title>p11&#45;&gt;p21</title>
<path d="M174,-161.1839C174,-153.3999 174,-144.1942 174,-135.6079"/>
<polygon points="177.5001,-135.5788 174,-125.5789 170.5001,-135.5789 177.5001,-135.5788"/>
<g class="m-node m-flat">
<title>p12</title>
<ellipse cx="285" cy="-179.9239" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="285" y="-176.1239">pipe&#45;2</text>
<g class="m-edge">
<title>p11&#45;&gt;p12</title>
<path d="M220.8281,-179.9239C223.1703,-179.9239 225.5125,-179.9239 227.8548,-179.9239"/>
<polygon points="228.1245,-183.424 238.1245,-179.9239 228.1244,-176.424 228.1245,-183.424"/>
<g class="m-edge">
<title>p21&#45;&gt;p31</title>
<path d="M174,-88.4144C174,-80.6303 174,-71.4246 174,-62.8383"/>
<polygon points="177.5001,-62.8093 174,-52.8093 170.5001,-62.8094 177.5001,-62.8093"/>
<g class="m-node m-flat">
<title>p22</title>
<ellipse cx="285" cy="-107.1543" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="285" y="-103.3543">pipe&#45;2</text>
<g class="m-edge">
<title>p21&#45;&gt;p22</title>
<path d="M220.8281,-107.1543C223.1703,-107.1543 225.5125,-107.1543 227.8548,-107.1543"/>
<polygon points="228.1245,-110.6544 238.1245,-107.1543 228.1244,-103.6544 228.1245,-110.6544"/>
<g class="m-node m-flat">
<title>p32</title>
<ellipse cx="285" cy="-34.3848" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="285" y="-30.5848">pipe&#45;2</text>
<g class="m-edge">
<title>p31&#45;&gt;p32</title>
<path d="M220.8281,-34.3848C223.1703,-34.3848 225.5125,-34.3848 227.8548,-34.3848"/>
<polygon points="228.1245,-37.8849 238.1245,-34.3848 228.1244,-30.8849 228.1245,-37.8849"/>
<g class="m-edge">
<title>p02&#45;&gt;p12</title>
<path d="M285,-233.9535C285,-226.1694 285,-216.9637 285,-208.3774"/>
<polygon points="288.5001,-208.3484 285,-198.3484 281.5001,-208.3485 288.5001,-208.3484"/>
<g class="m-node m-flat">
<title>p03</title>
<ellipse cx="396" cy="-252.6934" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="396" y="-248.8934">pipe&#45;3</text>
<g class="m-edge">
<title>p02&#45;&gt;p03</title>
<path d="M331.8281,-252.6934C334.1703,-252.6934 336.5125,-252.6934 338.8548,-252.6934"/>
<polygon points="339.1245,-256.1935 349.1245,-252.6934 339.1244,-249.1935 339.1245,-256.1935"/>
<g class="m-edge">
<title>p12&#45;&gt;p22</title>
<path d="M285,-161.1839C285,-153.3999 285,-144.1942 285,-135.6079"/>
<polygon points="288.5001,-135.5788 285,-125.5789 281.5001,-135.5789 288.5001,-135.5788"/>
<g class="m-node m-flat">
<title>p13</title>
<ellipse cx="396" cy="-179.9239" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="396" y="-176.1239">pipe&#45;3</text>
<g class="m-edge">
<title>p12&#45;&gt;p13</title>
<path d="M331.8281,-179.9239C334.1703,-179.9239 336.5125,-179.9239 338.8548,-179.9239"/>
<polygon points="339.1245,-183.424 349.1245,-179.9239 339.1244,-176.424 339.1245,-183.424"/>
<g class="m-edge">
<title>p22&#45;&gt;p32</title>
<path d="M285,-88.4144C285,-80.6303 285,-71.4246 285,-62.8383"/>
<polygon points="288.5001,-62.8093 285,-52.8093 281.5001,-62.8094 288.5001,-62.8093"/>
<g class="m-node m-flat">
<title>p23</title>
<ellipse cx="396" cy="-107.1543" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="396" y="-103.3543">pipe&#45;3</text>
<g class="m-edge">
<title>p22&#45;&gt;p23</title>
<path d="M331.8281,-107.1543C334.1703,-107.1543 336.5125,-107.1543 338.8548,-107.1543"/>
<polygon points="339.1245,-110.6544 349.1245,-107.1543 339.1244,-103.6544 339.1245,-110.6544"/>
<g class="m-edge">
<title>p03&#45;&gt;p13</title>
<path d="M396,-233.9535C396,-226.1694 396,-216.9637 396,-208.3774"/>
<polygon points="399.5001,-208.3484 396,-198.3484 392.5001,-208.3485 399.5001,-208.3484"/>
<g class="m-node m-flat">
<title>p04</title>
<ellipse cx="507" cy="-252.6934" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="507" y="-248.8934">pipe&#45;4</text>
<g class="m-edge">
<title>p03&#45;&gt;p04</title>
<path d="M442.8281,-252.6934C445.1703,-252.6934 447.5125,-252.6934 449.8548,-252.6934"/>
<polygon points="450.1245,-256.1935 460.1245,-252.6934 450.1244,-249.1935 450.1245,-256.1935"/>
<g class="m-edge">
<title>p13&#45;&gt;p23</title>
<path d="M396,-161.1839C396,-153.3999 396,-144.1942 396,-135.6079"/>
<polygon points="399.5001,-135.5788 396,-125.5789 392.5001,-135.5789 399.5001,-135.5788"/>
<g class="m-node m-flat">
<title>p14</title>
<ellipse cx="507" cy="-179.9239" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="507" y="-176.1239">pipe&#45;4</text>
<g class="m-edge">
<title>p13&#45;&gt;p14</title>
<path d="M442.8281,-179.9239C445.1703,-179.9239 447.5125,-179.9239 449.8548,-179.9239"/>
<polygon points="450.1245,-183.424 460.1245,-179.9239 450.1244,-176.424 450.1245,-183.424"/>
<g class="m-node m-flat">
<title>p33</title>
<ellipse cx="396" cy="-34.3848" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="396" y="-30.5848">pipe&#45;3</text>
<g class="m-edge">
<title>p23&#45;&gt;p33</title>
<path d="M396,-88.4144C396,-80.6303 396,-71.4246 396,-62.8383"/>
<polygon points="399.5001,-62.8093 396,-52.8093 392.5001,-62.8094 399.5001,-62.8093"/>
<g class="m-node m-flat">
<title>p24</title>
<ellipse cx="507" cy="-107.1543" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="507" y="-103.3543">pipe&#45;4</text>
<g class="m-edge">
<title>p23&#45;&gt;p24</title>
<path d="M442.8281,-107.1543C445.1703,-107.1543 447.5125,-107.1543 449.8548,-107.1543"/>
<polygon points="450.1245,-110.6544 460.1245,-107.1543 450.1244,-103.6544 450.1245,-110.6544"/>
<g class="m-node m-flat">
<title>p34</title>
<ellipse cx="507" cy="-34.3848" rx="46.8387" ry="18.2703"/>
<text text-anchor="middle" x="507" y="-30.5848">pipe&#45;4</text>
<g class="m-edge">
<title>p33&#45;&gt;p34</title>
<path d="M442.8281,-34.3848C445.1703,-34.3848 447.5125,-34.3848 449.8548,-34.3848"/>
<polygon points="450.1245,-37.8849 460.1245,-34.3848 450.1244,-30.8849 450.1245,-37.8849"/>
<g class="m-edge">
<title>p04&#45;&gt;p14</title>
<path d="M507,-233.9535C507,-226.1694 507,-216.9637 507,-208.3774"/>
<polygon points="510.5001,-208.3484 507,-198.3484 503.5001,-208.3485 510.5001,-208.3484"/>
<g class="m-edge">
<title>p14&#45;&gt;p24</title>
<path d="M507,-161.1839C507,-153.3999 507,-144.1942 507,-135.6079"/>
<polygon points="510.5001,-135.5788 507,-125.5789 503.5001,-135.5789 510.5001,-135.5788"/>
<g class="m-edge">
<title>p24&#45;&gt;p34</title>
<path d="M507,-88.4144C507,-80.6303 507,-71.4246 507,-62.8383"/>
<polygon points="510.5001,-62.8093 507,-52.8093 503.5001,-62.8094 510.5001,-62.8093"/>
</div><p>When resetting a scalable pipeline to a new range, it will start from the initial state as if it has just been constructed, i.e., the token number counts from zero.</p><aside class="m-note m-warning"><h4>Attention</h4><p>Unlike <a href="classtf_1_1Pipeline.html" class="m-doc">tf::<wbr />Pipeline</a> that keeps the given pipes in a <a href="http://en.cppreference.com/w/cpp/utility/tuple.html" class="m-doc-external">std::<wbr />tuple</a> object, <a href="classtf_1_1ScalablePipeline.html" class="m-doc">tf::<wbr />ScalablePipeline</a> does not own the given pipe but maintains a vector of iterators to each pipe in the given range. It is your responsibility to keep those pipe objects alive during the execution of the pipeline task.</p></aside></section><section id="ResetAPlaceholderScalablePipeline"><h2><a href="#ResetAPlaceholderScalablePipeline">Reset a Placeholder Scalable Pipeline</a></h2><p>It is possible to create a scalable pipeline as a placeholder using the constructor overload <a href="classtf_1_1ScalablePipeline.html" class="m-doc">tf::<wbr />ScalablePipeline(size_t num_lines)</a> and reset it to another range later in the application. The following code creates a task to emplace a range of pipes and reset the pipeline to that range, before running the pipeline task:</p><pre class="m-code"><span class="n">tf</span><span class="o">::</span><span class="n">Executor</span> <span class="n">executor</span><span class="p">;</span>
<span class="n">tf</span><span class="o">::</span><span class="n">Taskflow</span> <span class="n">taskflow</span><span class="p">;</span>
<span class="kt">size_t</span> <span class="n">num_pipes</span> <span class="o">=</span> <span class="mi">10</span><span class="p">;</span>
<span class="kt">size_t</span> <span class="n">num_lines</span> <span class="o">=</span> <span class="mi">10</span><span class="p">;</span>
<span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="n">tf</span><span class="o">::</span><span class="n">Pipe</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">function</span><span class="o">&lt;</span><span class="kt">void</span><span class="p">(</span><span class="n">tf</span><span class="o">::</span><span class="n">Pipeflow</span><span class="o">&amp;</span><span class="p">)</span><span class="o">&gt;&gt;&gt;</span> <span class="n">pipes</span><span class="p">;</span>
<span class="n">tf</span><span class="o">::</span><span class="n">ScalablePipeline</span><span class="o">&lt;</span><span class="k">typename</span> <span class="nc">decltype</span><span class="p">(</span><span class="n">pipes</span><span class="p">)</span><span class="o">::</span><span class="n">iterator</span><span class="o">&gt;</span> <span class="n">spl</span><span class="p">(</span><span class="n">num_lines</span><span class="p">);</span> 
<span class="n">tf</span><span class="o">::</span><span class="n">Task</span> <span class="n">init</span> <span class="o">=</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="k">for</span><span class="p">(</span><span class="kt">size_t</span> <span class="n">i</span><span class="o">=</span><span class="mi">0</span><span class="p">;</span> <span class="n">i</span><span class="o">&lt;</span><span class="n">num_pipes</span><span class="p">;</span> <span class="n">i</span><span class="o">++</span><span class="p">)</span> <span class="p">{</span>
    <span class="n">pipes</span><span class="p">.</span><span class="n">emplace_back</span><span class="p">(</span><span class="n">tf</span><span class="o">::</span><span class="n">PipeType</span><span class="o">::</span><span class="n">SERIAL</span><span class="p">,</span> <span class="p">[</span><span class="o">&amp;</span><span class="p">](</span><span class="n">tf</span><span class="o">::</span><span class="n">Pipeflow</span><span class="o">&amp;</span> <span class="n">pf</span><span class="p">)</span> <span class="p">{</span> 
      <span class="k">if</span><span class="p">(</span><span class="n">pf</span><span class="p">.</span><span class="n">pipe</span><span class="p">()</span> <span class="o">==</span> <span class="mi">0</span> <span class="o">&amp;&amp;</span> <span class="n">pf</span><span class="p">.</span><span class="n">token</span><span class="p">()</span> <span class="o">==</span> <span class="mi">1024</span><span class="p">)</span> <span class="p">{</span>
        <span class="n">pf</span><span class="p">.</span><span class="n">stop</span><span class="p">();</span>
        <span class="k">return</span><span class="p">;</span>
      <span class="p">}</span>
    <span class="p">});</span>
  <span class="p">}</span>
  <span class="n">spl</span><span class="p">.</span><span class="n">reset</span><span class="p">(</span><span class="n">pipes</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span> <span class="n">pipes</span><span class="p">.</span><span class="n">end</span><span class="p">());</span>
<span class="p">}).</span><span class="n">name</span><span class="p">(</span><span class="s">&quot;init&quot;</span><span class="p">);</span>
<span class="n">tf</span><span class="o">::</span><span class="n">Task</span> <span class="n">pipeline</span> <span class="o">=</span> <span class="n">taskflow</span><span class="p">.</span><span class="n">composed_of</span><span class="p">(</span><span class="n">spl</span><span class="p">).</span><span class="n">name</span><span class="p">(</span><span class="s">&quot;pipeline&quot;</span><span class="p">);</span>
<span class="n">pipeline</span><span class="p">.</span><span class="n">succeed</span><span class="p">(</span><span class="n">init</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">wait</span><span class="p">();</span></pre><p>The task graph of this program is shown below:</p><div class="m-graph"><svg style="width: 55.750rem; height: 15.375rem;" viewBox="0.00 0.00 892.00 246.00">
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</div><aside class="m-note m-warning"><h4>Attention</h4><p>It is your responsibility to ensure a scalable pipeline has a valid structure before running it. A valid pipeline must have at least one parallel line and one pipe, where the first pipe is a serial type.</p></aside></section><section id="ScalablePipelineUseOtherIteratorTypes"><h2><a href="#ScalablePipelineUseOtherIteratorTypes">Use Other Iterator Types</a></h2><p>When assigning a range to a scalable pipeline, the pipeline fetches all pipe iterators in that range to an internal vector. This organization allows invoking a pipe callable to be a random accessible operation, regardless of the pipe container type. Taskflow does not have much restriction on the iterator type, as long as these pipes can be iterated in a sequential order using the postfix increment operator, <code>++</code>.</p><pre class="m-code"><span class="c1">// use vector to store pipes</span>
<span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="n">tf</span><span class="o">::</span><span class="n">Pipe</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">function</span><span class="o">&lt;</span><span class="kt">void</span><span class="p">(</span><span class="n">tf</span><span class="o">::</span><span class="n">Pipeflow</span><span class="o">&amp;</span><span class="p">)</span><span class="o">&gt;&gt;&gt;</span> <span class="n">vector</span><span class="p">;</span>
<span class="n">tf</span><span class="o">::</span><span class="n">ScalablePipeline</span> <span class="n">spl1</span><span class="p">(</span><span class="n">num_lines</span><span class="p">,</span> <span class="n">vector</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span> <span class="n">vector</span><span class="p">.</span><span class="n">end</span><span class="p">());</span>
<span class="c1">// use list to store pipes</span>
<span class="n">std</span><span class="o">::</span><span class="n">list</span><span class="o">&lt;</span><span class="n">tf</span><span class="o">::</span><span class="n">Pipe</span><span class="o">&lt;</span><span class="n">std</span><span class="o">::</span><span class="n">function</span><span class="o">&lt;</span><span class="kt">void</span><span class="p">(</span><span class="n">tf</span><span class="o">::</span><span class="n">Pipeflow</span><span class="o">&amp;</span><span class="p">)</span><span class="o">&gt;&gt;&gt;</span> <span class="n">list</span><span class="p">;</span>
<span class="n">tf</span><span class="o">::</span><span class="n">ScalablePipeline</span> <span class="n">spl2</span><span class="p">(</span><span class="n">num_lines</span><span class="p">,</span> <span class="n">list</span><span class="p">.</span><span class="n">begin</span><span class="p">(),</span> <span class="n">list</span><span class="p">.</span><span class="n">end</span><span class="p">());</span></pre></section><section id="ParallelScalablePipelineLearnMore"><h2><a href="#ParallelScalablePipelineLearnMore">Learn More about Taskflow Pipeline</a></h2><p>Visit the following pages to learn more about pipeline:</p><ol><li><a href="ParallelPipeline.html" class="m-doc">Parallel Pipeline</a></li><li><a href="TextProcessingPipeline.html" class="m-doc">Text Processing Pipeline</a></li><li><a href="GraphProcessingPipeline.html" class="m-doc">Graph Processing Pipeline</a></li><li><a href="TaskflowProcessingPipeline.html" class="m-doc">Taskflow Processing Pipeline</a></li></ol></section>
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