The butterfly network, a communications network used in distributed computing and fast Fourier transform algorithms. The highlighted red nodes and edges show the subset of the butterfly reachable from one of its nodes. For each subset, the reachable subgraph forms a complete binary tree, showing that the butterfly is a <a href="https://en.wikipedia.org/wiki/Multitree" class="extiw" title="en:Multitree">multitree</a>.
<a href="//commons.wikimedia.org/wiki/User:David_Eppstein" class="mw-redirect" title="User:David Eppstein">David Eppstein</a>
<span class="int-own-work" lang="en">Own work</span>