">::</span><span class="n">Task</span><span class="o">&gt;&gt;</span><span class="w"> </span><span class="n">node</span><span class="p">(</span><span class="n">num_blocks</span><span class="p">);</span>
<span class="w">  </span>
<span class="w">  </span><span class="c1">// create num_blocks*num_blocks placeholder tasks</span>
<span class="w">  </span><span class="k">for</span><span class="p">(</span><span class="k">auto</span><span class="w"> </span><span class="o">&amp;</span><span class="n">n</span><span 