Starcraft AI blog

Iruian donated some protoss openings with weights as used in the bot Antiga. I will distribute them with Steamhammer, but I’m still pondering exactly how. The openings are supposed to be straight from Liquipedia, and the ensemble is claimed 50 to 100 elo stronger than Steamhammer’s default protoss openings. I don’t have any reason to doubt it, but I’m still in the process of checking the openings myself.

Unfortunately, there are reasons not to take openings straight out of Liquipedia without testing. Most of Steamhammer’s provided openings are modified from Liquipedia versions, and sometimes the changes are major. (Some were taken from other sources, and a few were developed from scratch, starting with no more than the opening stem and a plan.)

Sometimes Liquipedia is unhelpful, if not outright wrong. I think the 12 pool lurker build on this page is a prime example. It says you should adhere to the build strictly. But if you build everything that the build order calls for, then lurkers are severely delayed, and the build order makes no sense (at least to me); use a 12 hatch build instead. If you minimize the build to get lurkers as fast as possible, then you end up with 4 or more larvas for a long stretch after the second hatchery finishes, meaning that there was no reason to get the second hatchery so soon; you should have stuck with a single hatchery build. Presumably a pro can weigh the situation and decide what extra stuff is good to make, but Steamhammer doesn’t have that skill. So I found the Liquipedia build order unhelpful.

Often Steamhammer plays poorly in the middle game, and the weak play can be worked around or delayed by extending the opening. This is the main reason to deviate from standard builds: Alter the opening so that Steamhammer plays it better.

BOSS is weak, which causes terran and protoss to play poorly after the opening. BOSS tends to build too many production buildings—I often see 6 or 7 gateways on a one-base income that can support 4 gateways, which is wasteful. BOSS also likes to bunch the production of similar things, not keeping the nexus and gateways busy at the same time, but rather “probe probe probe probe zealot zealot zealot zealot”, where first the nexus is busy, then the nexus goes idle and the gateways become busy. It’s crazy inefficient.

That is why Steamhammer’s 9-9Gate opening is so long and detailed. If it ended early like the Liquipedia build, then BOSS would take over sooner and build inefficiently, and the bot would fall behind in probe count and zealot count for the rest of the game. I know this for sure, because I’ve run the different variants head-to-head. Dave Churchill optimized the 9-9 gate opening already for UAlbertaBot, and he did an excellent job. I optimized the 10-12 gate opening myself in a similar way and did not do it as thoroughly; it has room for improvement.

Someday I’ll write a new macro system and drop BOSS, but not yet. I might be able to get to it this year....

Sometimes the middle game strategy decisions are silly. Terran and protoss are especially short on strategy smarts, but the zerg strategy boss also has many weaknesses. In one frustrating example, if the opening build makes a spire but doesn’t make the mutalisks, Steamhammer may decide that lurkers were a better idea after all, get no lair units for a long time, and lose. There are many ways for the strategy boss to misunderstand the strategy behind an opening, so that you have to write a long explicit build order. Some openings I have shortened after improving the strategy boss. Some openings have legacy endings that it might be good to remove.

Anyway, the bottom line is that Steamhammer is not strong enough to play Liquipedia opening builds uncritically. Some are fine, some will confuse the poor bot.

On the other hand, Steamhammer’s existing protoss openings leave a lot to be desired. They’re more a demonstration of what’s possible than a sound selection. It’s no surprise if Antiga’s openings are stronger.

Next: Looking at the donated openings.