Starcraft AI blog

This Steamhammer version is not performing as well as I had hoped. It seems that the new weaknesses more or less offset the new strengths. Also, every time Steamhammer’s play changes, its past learned data becomes less effective. This change was big enough that some counters which used to work against a given opponent no longer do.

• The new retreat behavior in defense looks like a net loss. As I mentioned in the change list, it prevents the severe mistake of making a last stand outside of static defense range, but causes the severe mistake of fleeing from a stronger enemy when it should engage. I think the mistake caused is probably worse than the mistake prevented. For example, Steamhammer lost its ability to reliably defeat XIMP by Tomas Vajda, and excess retreating by defenders is the main cause.

The upside is that it’s relatively easy to reduce excess retreating without causing premature last stands. It was always on my list, I didn’t have time.

• The other defense changes are good, but don’t help greatly. Steamhammer is a little more effective at assigning defenders, and I may be the only person who can tell.

• Predicting enemy unit movement seems to be a win overall. Enemy scouting workers are caught, and units trying to slip past screening zerglings rarely get through. Zergling versus zergling micro is sometimes dramatically stronger—attack with fewer and no advantage in formation, win anyway. The disadvantage is that units are more likely to get stuck, either stuck in place on their own or stuck on each other. I have to dig in and solve that.

• The improvements in overlord safety help against many opponents, but do not help enough to make a big difference. Probably Steamhammer can defeat weaker enemies a little more consistently. Against protosses that make corsairs but don’t have strong overlord hunting skills, like Skynet, the improvements can save games. Against those with strong skills, like BananaBrain, Steamhammer holds on well at first and survives longer into the game, but the slaughter begins as soon as observers or dark templar come out and the overlords leave the safety of their spore colonies. Alongside better overlord movement, Steamhammer needs better air defense skills with hydras and scourge.

• I suspect that the heuristic “the enemy is ahead in army, make more combat units” rule is not tuned well. I think it helps on average, but not as much as it could. And there are times when it is wrong.

• The “oops, expanding failed, I’ll turn it into a macro hatchery” rule causes Steamhammer to make many extra macro hatcheries when it is contained. It may be an improvement over losing an infinite stream of drones, but it’s still awful. There is an obvious quick-and-dirty fix of canceling excess macro hatcheries in the building manager before they are started—but I think that will cause Steamhammer to go back to losing an infinite stream of drones, while doing unnecessary work in between. Have to bite the bullet on this one and perform serious surgery.

• The better sunken and spore placement is all win, despite occasional odd results. “Ooh, sunkens right up against my ramp! Units can’t get out? So what, it’s safe!” Now I need to add the production goal to put the right static defense at every base that is vulnerable to vulture or air harass.

Next: AIIDE plans in a little more detail.