It's the symmetry that gives recursive opportunities to apply the optimization. It's the same optimization folded over and over again. Butterfly diagrams are gr

It's the symmetry that gives recursive opportunities to apply the optimization. It's the same optimization folded over and over again. Butterfly diagrams are great for understanding this. https://news.ycombinator.com/item?id=45291978 https://news.ycombinator.com/item?id=45291978 has pointers to more in depth exploration of the idea.