Starcraft AI blog

The opponent model can (sometimes) select openings in the development Steamhammer. That’s the key feature I wanted, so I should be able to release Steamhammer 1.4 shortly after SSCAIT ends, as I hoped. After some thought, I found a simple way to avoid the big refactoring I had expected.

It’s rather nice to see Steamhammer lose the first game, or sometimes the first several games, then realize what’s going on and abruptly counter the opponent’s play. It tries to predict the opponent’s plan. So far the prediction is made in an extremely simpleminded way, but I may improve it before release. Of course it is easier to predict an opponent that plays a fixed strategy than a learning bot, so I expect the skill to be less effective against the top bots. Predicting the opponent’s plan lets Steamhammer choose more extreme openings that are risky against an unknown opponent. Today I added a ZvZ_12Hatch opening, which is unsafe against many bots but is a strong counter to the favorite strategies of AILien and a few other zergs.

I expect to remove most of the enemy-specific strategies that are configured for various opponents. There are way too many of them. Steamhammer will finally have the ability to adjust its play when an opponent starts playing differently. Some enemy-specific configuration will remain for this version because the opponent model is not smart enough yet. I think I will let Steamhammer learn from scratch rather than feeding it artificial “learned” data to replace the manual configuration. That will depress its results against the rushbots until it learns about them, but it will be a good test of how well the opponent model works. Steamhammer will be smarter, but at first it will look stupider.

As always, my list of bugs to fix and improvements to make is longer than I can possibly work through. CherryPi has a whole team that still can’t fix all its bugs. I should be able to make some progress before the end of the tournament, though.

One of Brood War’s permanent irritations is that updates to the game engine tend to break saved replays from previous versions. There is no backward compatibility. I have decided to add a version number to Steamhammer’s saved opponent data files. I hope that I’ll be able to release future versions with different file formats that can still make use of the learning data from older versions. It would be no fun to have to relearn the opponents from scratch because an improved version came out.

aside

Speaking of SSCAIT, mixed in the usual random game list since the round robin phase ended are games that look like they’re from the round of 16. It worked the same last year. I watched some of these games from the replay page, but Steamhammer’s apparent round of 16 games are omitted from the page, no doubt due to some glitch. I save all of Steamhammer’s replays. Tournament replays are especially interesting, so it will be a shame if some of them aren’t available.