## Scoring tennis using finite-state automata

Scoring tennis using finite-state automata by Michael McCandless.

From the post:

For some reason having to do with the medieval French, the scoring system for tennis is very strange.

In actuality, the game is easy to explain: to win, you must score at least 4 points and win by at least 2. Yet in practice, you are supposed to use strange labels like “love” (0 points), “15” (1 point), “30” (2 points), “40” (3 points), “deuce” (3 or more points each, and the players are tied), “all” (players are tied) instead of simply tracking points as numbers, as other sports do.

This is of course wildly confusing to newcomers. Fortunately, the convoluted logic is easy to express as a finite-state automaton (FSA):

And you thought that CS course in automata wasn’t going to be useful. ðŸ˜‰

Michael goes on to say:

FSA minimization saved only 3 states for the game of tennis, resulting in a 10% smaller automaton, and maybe this simplifies keeping track of scores in your games by a bit, but in other FSA applications in Lucene, such as the analyzing suggester, MemoryPostingsFormat and the terms index, minimization is vital since saves substantial disk and RAM for Lucene applications!

A funny introduction with a serious purpose!