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Developing StarCraft 2 Build Orders With Genetic Algorithms
Jamie recommends a blog post from software engineer Louis Brandy explaining how using genetic algorithms to evaluate build orders in StarCraft 2 has led to some surprisingly powerful results. Quoting:
"One of the reasons build-order optimization is so important is that you can discover openings that 'hard-counter' other openings. If I can get an army of N size into your base when you do opening X, you will always lose. ... a genetic algorithm is a type of optimization algorithm that tries to find optimal solutions using a method analogous to biologic evolution (to be specific: descent with modification & natural selection). Put simply, you take a 'population' of initial build orders, evaluate them for fitness, and modify the population according to each element’s fitness. In other words, have the most successful reproduce. The program’s input is simply the desired game state. In practice, this means 'make N units' to determine some rush build order (but it also allows for other types of builds, like make N workers with some defensive structures and a small army)."
Yes, I find the summary comprehensible and know what a genetic algorithm is. I don't know what an explanation of genetic algorithms is doing in the summary, though. Linking the Wikipedia page would be much more effective, since so many readers get nothing out of this explanation (either they already know what a GA is and, like me, are annoyed at the minor waste of time, or they don't and a brief explanation isn't enough).
Well, to be fair there's a lot more to SC2 than just build-orders. :-) Build orders are mainly concerned with the "macro" aspect of SC2 gameplay, which is base management and economy, and they're also relevant only in the opening. Everything past the 7 or 8-minute mark is beyond build orders. Good micro (unit-level manipulation of movement and actions), harassment of workers, and timed expansions all kick in after that point, and those become the difference between winning a game and losing a game.
Also, there is an element of "good practices" in SC2. Rushes, especially "all-in" rushes (referred to by TFA) are generally considered bad practice. Beating your opponent every time is cool, but this is usually indicative of a game imbalance that Blizzard will probably patch at some point down the line, at which point you'll rapidly fall in the leagues as you lose to high-level players clued in on countering that or who simply have the good practices to beat it (like early scouting, etc.).
The other (more important) factor is that a gamer specializing in an all-in rush deteriorates his/her gameplay, because he won't have the variety to compensate for a failure of that rush. A rush usually means a sacrifice of something or the other (the tight game-mechanics of an SC2 opening means there's always an opportunity cost; to get that extra army, your economy suffers, or to get those extra resource-collectors, your army will be smaller). All-in rushes, and rushes in general sacrifice some thing or the other which a good opponent can exploit if he/she manages to push back the rush. Someone over-playing one tactic will lack the skills to compensate for its failure, so varying one's game by mastering different build-orders and plays is the better way to do this (if slower).
-1, Misinformed
The AI does not get double resources (although on Very Hard and Insane it does get an extra amount, but not double), and it does not do the absolute best it can. I guarantee you that if given the source code I could improve it, by simply exploiting the hell out of its APM advantage. The reason is that the AI has imperfections designed in; it is designed to respond somewhat superficially like a human opponent and not exploit godly micro tricks that a 2000+ APM computer could use. Here are a few things to get started: roach burrow micro; hidden queens in overlords microing transfuse, perhaps on dancing mutalisks; blink micro tricks; rotating damaged infantry in and out of bunkers; thorship micro.
Yes, making a proper strategic AI is very hard. But the included AI has a lot of room to improve in tactics, just by virtue of the ridiculous APM it can exploit.