Starcraft AI blog

Why does random UAlbertaBot score so well? Its 5 pool rush is easy to counter. Its marine rush is weak and easy to counter. Its zealot rush is strong, but it can be stopped too. I think the secret is: What opening counters all 3? Well, overpool works, but you have to play it very differently depending on what race UAlbertaBot turns out to be. Bots struggle to adapt. Randomness has value in itself, because it forces the opponent first, to choose openings carefully, and second, to scout and adapt.

Steamhammer’s new strategy boss is not far along; it can only respond to a few basic emergencies, like having no drones. (Steamhammer 0.2 freezes; the development version orders up a drone and can play on if it has 50 minerals.) But yesterday I decided it would be more fun to switch the order of improvements around and do randomized openings before getting the strategy basics down.

I was right, the variety is a lot more fun. I don’t know in advance what Steamhammer is going to do; I have to watch and see.

Today I played a long ZvZ match versus Zia to make sure that the random openings don’t hurt performance. Steamhammer played 5 different openings. One of the openings dominates Zia, but Zia has answers to the other 4—if it can find the answers with its opening learning. Does mixing in the weaker openings give Zia a chance to find the answers, or does the randomness wipe out any learning signal and make life even harder for Zia?

Answer: After 45 games, giving Zia time to learn, Steamhammer scored 40-5. Zia won 4 games by accidentally hitting on a counter and 1 by playing better tactically. At worst, the weaker openings do not hurt. They were chosen to have different counters, and Zia’s implicit assumption that there should be One Best Counter is wrong.

Lesson: Opening learning is not enough, at least not this kind. As difficult as it may be, you have to recognize what the opponent is doing and adapt to it.

On the downside, to earn the full advantage from random openings I have to implement more openings and make sure that Steamhammer plays all of them well enough. At the moment it only has enough variety in ZvZ. But someday, with both random openings and opening learning, Steamhammer will turn fearsome.

Update: I should have added a couple points. 1. Random openings make it hard for other bot authors to hand-code counters to your strategy. This change to Steamhammer should defeat Chris Coxe’s plan of countering specific opponents. 2. Random openings are more fun for humans to play against.

Tomorrow: The curséd bunker obsession. After that: Retreating is hard to do.