Starcraft AI blog

I’ve been playing with the new version of SparCraft by Dave Churchill. I made 2 Steamhammer versions which are identical except for the SparCraft version, so I can test for differences in various scenarios.

My conclusions so far:

1. The new version was not too much trouble to integrate. Throw out the old SparCraft folder, drop in the new one, tweak one Visual Studio setting since I’m using an older version, and rewrite a small amount of initialization code and calling code. There is a new SparCraft configuration file that has to go into bwapi-data/AI/. It’s not much work at all for swapping out a major component. I also removed a small amount of debugging code from SparCraft, but that wasn’t necessary.

2. Dave Churchill dubbed it “semi-stable”, and it’s true. It mostly works, but throws fairly often. I modified the try-catch in Squad to catch all exceptions, and return -1 “we lose” when SparCraft throws. Then the squads retreat, which simplifies the situation so that the errors don’t usually persist. It works well enough. Another idea would be to remember the results of the last successful run and reuse them. I didn’t try that.

3. It still doesn’t support bunkers, reavers, or carriers. That’s quite a limitation. The “let’s pretend this bunker is 5 marines” trick (or something like it) is still needed.

4. Results for battles among ground units seem about as good as before. Tests under controlled conditions would surely find differences, but I’m interested in real games first. For games which stay on the ground, the difference is smaller than I can see by eye and smaller than I can measure from game outcomes, at least so far.

5. Results for battles with air units are improved. Steamhammer with old SparCraft likes to suicide mutalisks. Steamhammer with new SparCraft will still do it, but less happily. It understands turrets and spore colonies better than before. It seems to have an advantage in straight air-to-air battles too, though that’s based on only a small number of test games.

6. Since air units have lost some of their overconfidence and retreat more often, the weakness of their retreating behavior shows more. Steamhammer has always had a tendency to string out its mutalisks due to poor retreating (and other causes), even when it should pull them into a tight knot. The new SparCraft makes it worse. The first couple mutalisks see a bunker and pull back “until reinforcements arrive,” and the reinforcements wait at home “until the outlook improves.” Fixing one weakness makes the next one starker! And it is an open question whether the cautious mutalisks will be as successful as overconfident mutalisks in harassment; they may pull back too early when they can’t win outright.

I haven’t measured the run time yet, which will be a crucial test. I hope the new version will turn out to be faster. Some day soon I will probably put up a test version on SSCAIT to see how it performs in the wide world. If I don’t hit any surprises, I may switch to the new SparCraft even if the remaining bugs don’t get fixed.