Seth, I appreciate that. As a novice programmer I appreciate to have exchanges with you guys who are making this. I'm using commercial software every day that hasn't made progress since the nineties.
I worked through something like fifteen types for the adjacency matrix (and, by the way, tuples for storage worked out, but was slower). I suppose Julia is fast so that we don't actually need to optimize like this all the time, but it's an excellent lesson. In the example I gave above you may have noted some confusion about rows-columns order. Those algorithms which were adapted from text books or other languages seem to walk along rows. In Julia, you walk faster downhill. And with @simd.
