Making `wc` 20x faster with parallel state machines

A few years back, I came across Robert Graham’s wc2 repository on GitHub. wc2 is an implementation of the Unix wc command that is significantly faster than the existing GNU and BSD wc implementations. It achieves its speed by using something called a state machine. The repo contains a nice write-up that explains some things, but doesn’t explain how the program actually works. I wrote this post to explain all of that.