Starcraft AI blog

I think the biggest weakness in Steamhammer protoss and terran is macro (not that they have any shortage of other weaknesses). They rely on BOSS by Dave Churchill for production decisions, and BOSS does not live up to its promise. BOSS often orders more production buildings than it can use, and then does not use them efficiently. It will do things like order up a big batch of workers, or of production buildings, and allow resources to accumulate that could be spent immediately in the existing production buildings. Randomhammer loses game after game as protoss and terran because it does not have as many units as it should. “Never mind that we’re under attack. The factories we have are not enough. Make more factories and leave the existing ones idle!” Steamhammer forks like terran bftjoet also suffer.

BOSS also works more effectively with long build orders, which means that bots tend to react slowly when the situation changes. When the bot makes a discovery (“uh oh, we need detection” or “that’s too many tanks, I should make zealots instead of dragoons”), it has four choices. 1. It can insert an emergency reaction directly into the build order. It does that when it sees dark templar: Protoss makes a forge and cannons, terran makes an ebay and turrets. It’s inefficient and delays regular production, because the inserted reaction and regular production cannot overlap. 2. It can wait for the current build order to finish and call for a reaction in the next build order. If the current build order is long, it may be a long wait before the reaction occurs. 3. It can cancel the build order and call for a new one that includes the reaction along with regular production. The reaction is likely to be slow because BOSS does not offer any way to prioritize. If you say you want an observer, BOSS promises that by the end of the build order you will have an observer; that’s the only promise. 4. It can cancel the current build order and call for a new one with only the reaction. The reaction will be quick but other production will suffer—again, no overlap. You'll get your observer as soon as possible, but in the meantime your gateways will be idle.

BOSS’s strength is that it provides an API that is easy to use. You tell it what units and upgrades you want, and it figures out prerequisites, decides what production and research buildings you’ll need, and gives you back an exact build order that accomplishes what you want (modulo a few bugs, which are minor for protoss and terran). If its build orders were good, BOSS would be great. As it stands, BOSS is convenient but problematic.

The current zerg strategy boss combines “what do we want to make?” and “how do we make it?” into a monolithic module. I want to refactor the two questions into separate modules. BOSS solves “how do we make it?” I’ll replace BOSS with a new production planner that accepts abstract production goals and incrementally plans how to achieve them.

“Abstract production goals” means you don’t ask for exactly what you want, as with BOSS. If you want tanks and vultures, then your production is constrained by the situation. Tanks are gas-heavy and how fast you can make them depends on your gas income. Vultures are limited more by the number of factories. You might emphasize tanks or emphasize vultures, but the production planner should take the income and production constraints into account when deciding how many factories to build and what the ratio between units should be. That should both make the API easier to use and improve the bot’s play.

I’m thinking the input should be a set of goals with priorities. Something like: Tanks with this priority; vultures with that priority; 2 dropships and 2 science vessels as soon as possible without wasting resources; upgrades with some priority, etc.

“Incremental planning” means that the plan is worked out in small chunks so that reactions can be quick. You should be able to change goals and priorities at any time and see results quickly. If you want an observer with high priority, each step along the tech path should take minimum time, and remaining resources should continue to go into your regular production.

That is my idea, as far as I have worked it out. It’s not an immediate plan. I have more plans than time. But I want to get around to it at some point. When I do, I expect Randomhammer’s protoss and terran play to become much stronger. Zerg should be a little stronger too.