Starcraft AI blog

I counted Steamhammer’s zerg openings, and found 222. Most of those I wrote as variations of standard builds, or when inspired to copy somebody else’s build ideas, or to systematically fill out a range of possibilities. A few are novel ideas that I had myself. Steamhammer’s new 12 gas 11 pool builds I have not seen elsewhere, though Steamhammer did already have a build named ZvZ_12Gas11Pool which is similar (it was an example of filling out a range of possibilities).

Why did I write over 200 opening builds? It’s obvious that Steamhammer can’t effectively use that many, because it doesn’t know how to choose between them without trying each one repeatedly. Against a difficult opponent, Steamhammer would have to play thousands of games to be likely to make the best choices, and even then it would risk being wrong—the opponent is learning too. I wrote them all anyway, because I have been planning from the beginning to make learning smarter. If the opening timing project works as well as I hope, the bot will be able to quickly zero in on promising builds from its large library, perhaps turning up surprising but effective tries. Compare my post Precomputing a catalog of build orders from April 2016, before I started work on Steamhammer.

11 gas 10 spawning pool is a standard zerg opening stem. It continues into fast one-hatchery mutalisks for ZvZ (implemented in Steamhammer in version 1.0 in January 2017 and for a long time Steamhammer’s favorite ZvZ build), or into one-hatchery lurkers for other matchups (mainly useful against terran). The timings have a good feeling, because when the spawning pool finishes, you can start your lair immediately and simultaneously start zerglings. You’re spending a lot to get fast tech, so the second hatchery comes much later.

I noticed that if you squeeze in a couple drones and drop one of the zergling pairs, you can get a second hatchery right after without delaying your tech. The only delay is in getting one extra drone before the extractor (you do have to wait a bit for the larva to spawn); after that, the build is every bit as smooth as the classic version. For the cost of that delay plus a lower number of zerglings, you get a stronger economy and a second hatchery, with a much wider selection of follow-up plans.

The build shares ideas with 12 pool builds, where you use the high number of early drones to get a second hatchery, but gets the lair before the second hatch. It also shares ideas with 2.5 hatch muta builds, where you get your tech first and add the extra hatchery along the way. You could think of it is as a 1.5 hatchery lurker/muta build.

I prefer the lurker version. Steamhammer wins a lot of games versus terran with 1 hatch lurker builds, but it is not skilled at using its lings along with the fast lurkers. And many terrans stay safe at home anyway, so that lings have little value before lurkers; all they can do is keep an eye on the front line. Getting an extra hatchery and stronger economy seems like a good tradeoff.

Here are the timings of some of Steamhammer’s lurker builds. The lurker column is the number of lurkers made in the first wave, for an initial attack (Steamhammer’s lurkers always attack). The time given is the frame that the first lurker hatches from its egg, median of 3 runs.