Starcraft AI blog

backward games

I added a zerg-versus-zerg 12 hatch opening to Steamhammer. It’s the greediest common ZvZ opening, so Steamhammer only plays it when the opponent model expects that the opponent will also play a hatchery-first opening. But look what happened: In a test game today against Microwave, Steamhammer opened 12 hatch and Microwave played its 5 pool opening. Steamhammer saw it coming only after the spawning pool was started; all it could do was start a sunken as soon as possible. Microwave’s zerglings tore down the natural hatchery first, and that was enough time for the sunken to finish and 4 zerglings to hatch, just enough to hold the rush. Steamhammer had a huge drone advantage, went up to 3 hatcheries, and smashed down Microwave by brute force while fighting right in the face of Microwave’s emergency defensive sunken. That’s the way to play!

It’s no wonder that pros, with their much stronger defensive skills, are so willing to play a greedy opening like 12 hatch in ZvZ.

Microwave’s 5 pool, by the way, is a clever build. Microwave builds a second hatchery at its natural to keep the zergling numbers up, and if the pressure doesn’t work out it drones up and switches to mutalisks. The opponent has to keep playing well to stay ahead. In a different test game, Steamhammer predicted the 5 pool and played an anti-rush opening which held the zerglings easily—then Steamhammer lost despite its advantage because it didn’t tech fast enough: The lair finished, and it decided to build a macro hatchery before the spire; the spire finished and it decided to build a third base before any mutalisks.... That’s not the way to play!

Steamhammer 1.4 is frozen

Steamhammer is feature-frozen for the 1.4 release. I will keep on fixing bugs and minor weaknesses (lair finished...) and tweaking the configuration, but I won’t start anything bigger that might delay the release, though there are plenty of temptations. I should be able to upload within a day after SSCAIT reopens for submissions, and release after another day or so once I can see that I didn’t break anything obvious.

Steamhammer 1.4 is substantially stronger than the tournament version in some ways. I think it is especially improved at transitioning out of the opening in ZvP. It will start off slowly on SSCAIT, because it will have to learn for itself how to beat a number of opponents that it currently beats by hand configuration. Also the opponent model has weaknesses and blind spots that are sure to cause some surprises. Still, if I didn’t mess anything up, Steamhammer should at least keep up with the competition and maintain a place near the top. Its play continues to grow more complex and interesting.

the game info display

As an example of a minor change, I have updated the game info display that Steamhammer can draw in the upper left corner.

If we have decided to steal gas, whether in the opening build order or in the opponent model’s auto gas steal decider, the strategy line adds + steal gas.

Opp Plan is the opponent’s plan. It is often Unknown. If the opponent model has predicted the opponent’s plan and the plan recognizer hasn’t verified it yet, we get the orange word expect. The opponent model tends to be overconfident about what it expects. When the plan recognizer thinks it knows what is going on, expect disappears and the recognized plan shows. The plan recognizer also relies on inadequate information, but at least it looks first. Steamhammer uses both the expected and the recognized plans, to a limited degree, for different purposes and with different levels of confidence.

The Time: line gives the game time in frames and in minutes:seconds. The minutes:seconds display is both more compact and easier to read than the original XXm YYs display. Then come the mean and maximum time spent per frame, in milliseconds, so we can start to get an idea of when things are slow.