Starcraft AI blog

Steamhammer 1.2.2 is uploaded. It is a bug fix release, mostly to fix strength-reducing bugs introduced in 1.2.1.

Next will be 1.2.3, primarily a feature release to help all races play stronger and more interesting games, then 1.2.4 to fix lingering bugs.

bug fixes

6 bugs are fixed, 3 serious bugs that caused losses for all races in version 1.2.1, and 3 zerg bugs that are smaller and didn’t cause any losses that I could identify. There are still no known crashing bugs.

• The bug in retreating to the natural is fixed. When retreating with no fresh units on the way, Steamhammer now retreats to the natural if it has been taken, or to the main otherwise. Retreating blindly to the natural caused many losses when the bot did things like retreat from the main to the natural when the enemy was at the ramp. (Squad::calcRegroupPosition())

The retreat system is confused in the first place. The first choice of retreat point is the closest friendly unit that is not “near” the enemy. It is supposed to close up gaps in the formation—that is why it is called “regrouping”. But in practice the closest friendly unit might be anywhere, and Steamhammer may retreat to the natural, to the main, or in a direction that makes no sense at all. Only when there is no friendly unit to retreat toward does it retreat to the natural or main as appropriate.

• Errors related to pulling workers for emergency defense are fixed. There were subtle issues causing workers to be left in the base defense squad after they were supposed to be released. It sometimes caused weird worker dances and other bad behavior. I also tightened it up; workers are now pulled to fight a proxy only if no combat units are out yet, and to fight zerglings only when they come very close to the mineral line, and otherwise not at all. Steamhammer will self-destruct less often, and (I hope) continue to successfully defend itself when it can. (CombatCommander::updateBaseDefenseSquads()—I renamed it for consistency.)

• A change in 1.2.1 to put more idle workers back to work introduced a bug where it also put building workers back to work before they started building, sometimes delaying the start of construction by as much as a few seconds. When timing is critical, it causes losses. In particular, it caused the 9 hatch opening to lose to 9 pool, when it should defend in time. Excess worker pulling contributed. (WorkerManager::updateWorkerStatus())

Lukas Moravec has found another bug that makes buildings start later, but the effect is smaller. I decided to delay fixing it until I understand it thoroughly.

• Zerg mistakenly made sunkens to defend against air attack. Oops. (StrategyBossZerg::checkGroundDefenses())

• Zerg was ignoring its absoluteMaxDrones value and making too many drones in long games, cutting into the supply available for its army. (StrategyBossZerg::updateGameState())

• Zerg catches more cases of deadlocks that cause production freezes. It should only have happened when Steamhammer was already in trouble, though. (StrategyBossZerg::nextInQueueIsUseless())

other improvements

• I tuned up the ZvZ 12 pool opening, and adjusted some opening settings.

• The true/false configuration options KiteWithRangedUnits, WorkersDefendRush, and ScoutHarassEnemy can now be set differently per race, to better support playing random. The feature is not used in the default configuration; all races are set to the same value. I also removed UseSparcraftSimulation, since it was already unused in the code.

Stone

This version does do worse versus Stone. In a test match, it scored 12-3 with 2 close calls where it went down to 2 drones. When worker defense was first implemented, Steamhammer scored 15-0 with 1 close call where it was taken down to 3 drones. The cause seems to be the return cargo bug fix. The effect is hard to see, but it makes workers more likely to stop and defend themselves in spots where other workers will not help them out. I decided that the correct fix is to improve worker micro, and I didn’t want to try something so delicate in a bug fix release.