Starcraft AI blog

SSCAIT’s web site is back up, though so far it doesn’t seem to be playing games. (Is this the service being moved to its new home?) I uploaded Steamhammer 3.1 there as soon as I saw. It should pass through to BASIL as usual.

I’m pleased with 3.1’s performance on the Starcraft AI Ladder. It was a small update, and the win rate went up by a small but consistent amount. If that holds on BASIL too (I expect it will), then Steamhammer stands a good chance of overtaking Microwave, which just recently stole the top zerg crown. Steamhammer and Microwave have been swapping top zerg honors for a long time now.

Stardust has joined the Starcraft AI Ladder with a 93% win rate, pushing everybody else’s win percentages down. That’s good. But with few participants and those changing over time, it’s difficult to check progress week to week; you can’t simply compare your win rate this week to your win rate last week. Maybe at the end of the week I’ll calculate elo ratings.

Steamhammer has suffered a regression: Scourge has mysteriously started to target floating buildings again, a mistake that I originally fixed long ago. Somewhere bits have decayed.

Steamhammer 3.2 and up

Steamhammer 3.1 is no longer running on the Starcraft AI Ladder; I already uploaded a version I called 3.2. I decided that the plan is to leave Steamhammer 3.1 on SSCAIT and BASIL until after the AIIDE submission deadline, and upload frequent test versions to the eponymous Ladder (as opposed to the ladders with other names). They’ll be called 3.2, 3.2.1, and so on, so the AIIDE 2020 version will be 3.2.something.

I won’t be going into detail yet, but 3.2 has 3 changes. 2 are the cheese responses, and if they’re successful you won’t often see them because opponents will learn better. The other you won’t see at all: I lifted the limitation which made Steamhammer unable to mine out blocking mineral patches which contain a non-zero amount of minerals. Once I looked at it, I realized it was only 2 lines of code, trivial to write and easy to test. None of the ladder maps (for any of the ladders), and none of the AIIDE 2020 maps, has blocking minerals like that; all their mineral blocks are stacked 0-mineral patches. But there will be another “unknown maps” contest at AIIDE, and maybe one of those maps will.

I tested on Sin Peaks of Baekdu, by the way, which has mineral patches with 40 minerals to block a useful path next to each main. The difference between stacked 0-mineral patches and single small mineral patches is usually not important to the player; you have to return the minerals you mined, which eats frames, but the blocks are normally close and have few minerals so it’s not many trips. But if the opponent wants to mine out the block to attack you, it’s a different story. Stacked o-mineral patches can be mined out in one go by sending one worker for each patch in the stack (mining out all patches in the stack simultaneously), so it can allow early-game cheese. The single mineral patch has to be mined out 8 minerals at a time, so the prospective cheese victim has more opportunity to react.

The sunken defense of outlying bases in Steamhammer 3.1 has the effect of keeping drones alive and allowing it to play its favorite macro game. Not that Steamhammer is feeble at fast rushes, but in the late game once it has all the drones it wants it rarely loses. Cheese defenses also discourage the opponent from trying to win fast, and allow Steamhammer to select macro openings more safely. Against Halo by Hao Pan, Steamhammer has been favoring one-base muta play, which can defeat both Halo’s bunker rush and its 2-port wraith strategy (it’s amazing to watch mutas and scourge pummel the 2-port wraiths—soon cloaked—with less than half of terran’s worker count). In fact, Steamhammer prefers pool-first builds against a surprising number of opponents. My hope is to tighten the early game and get a big economy more often.