span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> T<span class="special">,</span> <span class="keyword">typename</span> Op<span class="special">&gt;</span> 
  <span class="keyword">void</span> <span class="identifier">reduce</span><span class="special">(</span><span class="keyword">const</span> <a class="link" href="communicator.html" title="Class communicator">communicator</a> <span class="special">&amp;</span> comm<span class="special">,</span> <spa