Starcraft AI blog

Instead of configuring all of Steamhammer’s opening probabilities by hand, I want it to figure them out for itself. The starting point is data: For each matchup, keep overall statistics of all the openings in a file. Another goal is to have Steamhammer adapt its strategy to maps based on experience. So I thought, why not combine the two? For each matchup and map, keep a file with numbers for all the openings. Or for each matchup, keep a file for all the pairs (map, opening)—that way the bot has the data to generalize between maps.

Someday I also want Steamhammer to adapt its strategy reactions and its tactics to the map. At first it will analyze the map and decide what looks good (“look at that cliff over the mineral line—I should go air or drop”); later it will learn from experience what works well. I don’t expect to get to that for a long time, though.

Steamhammer has over 60 zerg openings (it doesn’t play all of them), and the count will increase. SSCAIT has 14 maps and other tournaments use fewer, so I think I should be ready for on the order of 1000 pairs (map, opening) if I keep them in one file. Each pair would be one line of data, something like “<opening> <map> <# games> <# wins>” and maybe a few more numbers like mean game length, or a statistical summary of evaluations once there is an evaluation function, or whatever else. If I want a cache of map data like number of starting positions and rush distances and so on, to use in generalizing across maps, that would be in a separate file.

In that case there would be 12 matchup files, including data for when the opponent went random: TvT TvP TvZ TvR, PvT PvP PvZ PvR, ZvT ZvP ZvZ ZvR. With up to 1000 lines per file, it seems like a reasonable amount of data. In every game, Steamhammer would read one file in onStart() and write it in onEnd(), which doesn’t seem excessive. There is one complication. If the opponent goes random, and after I give Steamhammer the ability to change its mind on the fly (which I will do), then when Steamhammer finds out the opponent’s race it may want to read that matchup file too. Reading and analyzing that much data may take more than one frame time, so it might have to go into a separate thread. Another solution for when the opponent goes random might be to read 4 matchup files during onStart() when we are allowed more time. Well, when it comes up I’ll figure out a plan. Maybe nothing special will be needed (seek time for a hard drive could exceed one frame time, but reading from SSD is faster).

That’s the data. How to use it? I haven’t decided on details. The opponent model keeps detailed records for each game against a given opponent, including the map. When we play the opponent for the first time, decisions have to be made without the opponent model, solely on the basis of the matchup+map+opening statistics. I’ll figure out a more-or-less sound way to turn the raw numbers into probability-to-play-this values, including an exploration policy. There are choices. After we’ve played an opponent many times, the opponent model will have more information (since it records more data, and it is specific to the opponent), so it can decide on its own. In between, I’ll need some kind of evidence combination procedure to blend the 2 sources of information together. I expect that a simple procedure would work fine, even weighted averaging of probabilities.

Steamhammer’s configuration file will become much shorter. I expect I’ll retain the manual configuration options for openings, for those bot authors who want to do it that way, but Steamhammer itself will rely on the data it collects. Once I have a good set, I’ll distribute it with the bot.

I’m not sure when I’ll get to all this stuff. Maybe or maybe not in the 1.4.x series.

Next: A tree of openings. It ties in.