Starcraft AI blog

Watch Tscmoo’s early game closely (these games will do; follow the minimap) and you’ll see that the bot scouts like it has OCD. It scouts for enemy expansions repeatedly, it scouts in its base for proxies, it scouts around its base for proxies. It often has two workers scouting at once, and when it loses one it sends another. It seems less interested in looking inside the enemy base, but it tries to go there too. It can notice tricks that kill other bots.

Humans are different. Expert humans have confidence in their ability to hold off rushes and are aware of how far it sets them back to lose mining time, especially early, so they commonly scout later than is recommended for beginners. While in the dark they may add a few quick checks for proxies depending on the map and matchup. To make up for it, humans infer far more information from their scouting data. Bisu’s probe does not see buildings and units, it sees strategies and timings and intentions far into the future.

That’s hard for bots, of course. There are academic papers about strategy inference, and I found them unconvincing. One step at a time.

All bots should use scouting information about the location of enemy buildings, and I’m sure most do. Adaptive bots, from what I’ve seen, look at enemy buildings and units and adjust to counter them, or switch to a strategy that counters. I’ve heard of counting workers too. BroodWarBotQ used to try fancy strategy inference; I don’t know how well it worked. ZZZKBot, which has to scout early for its 4-pool, knows how to infer the location of an enemy zerg base when it sees the first overlord, a rare skill. Those are all the uses of scouting information that I know of. I’d love to hear about bots that do other cool stuff.

Do any bots count supply? Humans are always on the lookout for missing pylons, which could power a proxy. For example, if there are more zealots and probes than the pylons can support, then you’ve missed a pylon somewhere and may want to search for it. Or you could cut it down to “At this frame number/with this probe count I expect 2 pylons. Where’s the second one?”

Do any bots count minerals? How many minerals are left in each mineral patch is visible as long as the patch is in your sight range. If you add up the enemy’s total minerals mined and the total needed to produce the enemy buildings and units that you’ve seen (plus the number you can see being carried by workers), then the difference is the stuff produced that you haven’t seen yet (plus minerals being saved up, and minerals carried by workers that were lost or traded for gas or are out of sight). You may be able to suspect or rule out a hidden expansion or a proxy. Bots can do this much more easily than humans!

I’m sure some bots look at buildings and not only units to guess what the enemy will build. If you see a barracks, you don’t know (without more information) whether it was made to produce units or as a prerequisite for a factory. If you see 2 barracks, you can be pretty sure. A hydra den or a protoss stargate gives stronger clues. Surely some bots understand, but I don’t know which ones. Do any current bots try to put together a holistic picture?

I also wonder whether some bots scout too early for their own good. When you should scout depends on your strategy, of course. If your bot is on the dumb side and only cares where the enemy is so it knows which direction to attack, maybe it can scout very late.