Starcraft AI blog

From watching tournament games, I wrote down about 20 to-do items. A couple are ideas to try, but most are bugs, and 8 are critical bugs that I want to fix fast. I thought I had left Steamhammer in a more reliable state. :-(

Steamhammer lost its tournament record of no losses due to crippling bugs when it lost both games to Wuli. In both games, it misdiagnosed the protoss opening as “Fast rush” instead of “Heavy rush” and broke out of an opening that would have been strong, reacting as though it were facing a surprise 6 gate rather than 9-9 gates. You can’t survive a blunder like that against an aggressive opponent. I don’t see the error in the code, but I’ll work it until I find it.

Two winning games were even worse, against cannon bot Juno by Yuanheng Zhu. Steamhammer started out playing a build that had been 100% successful forever, then panicked and broke out of the opening when it saw the cannons. I think that somehow a bug got into the code that decides whether the current build is good for the situation and should not be interrupted. Having broken out of the opening, Steamhammer relied on the strategy boss, which made choices much inferior to the planned opening. In one of the 2 games it played well enough to eventually bust the cannons and win, but the other game, on Python, was plagued by further severe bugs. If you know Starcraft at all, this game will offend your sense of esthetics, and possibly your sense of ethics; it is so bad it is immoral. Steamhammer smuggled a drone to a hidden expansion, one of few successful actions in the game. It built the expansion after a long delay—there is probably another bug there—then sent nearly every drone made at the outside hatchery back to the main so that it died to the containing cannons—definitely a bug, and not one I’ve seen before. Steamhammer also burrowed drones that came near cannons, so that it eventually stopped mining (even gas mining) because every surviving drone was burrowed. And other bugs. So many bugs. :-( Zerg won the game on points because it mined less and because Juno had its own misbehavior, repeatedly building cannons in sunken range where they died instantly.

The rich player usually loses if the game times out, because the rich player made more stuff and it died. And you want to be the rich player. So win your winning games, don’t let them time out!

Steamhammer won its games versus XIMP by Tomas Vajda with its usual seeming ease, but there was a bug there too. This bug I’d seen before, but I only realized the cause in watching the tournament. Steamhammer had a partial production freeze, where it built nothing but scourge and zerglings for a period, losing ground compared to its regular production. The cause is that the reactive behavior of building scourge and the fallback behavior of adding zerglings when the situation allows were jointly blocking the regular behavior of refilling the production queue. Only special case units were being made, not regular units.

The bugs above are severe, but only affected a few games each. Together, they may have cost Steamhammer one rank in the tournament, if that much. I think the latency compensation bug is more severe, even though I can’t point to a game that Steamhammer definitely lost due to it. It affects far more games, and one of the effects is to drop one drone in 12 pool or 12 hatchery builds. Being one drone short of plan, starting early in the opening, is a serious handicap. It also sometimes drops planned zerglings or other units. Many openings have their timing disrupted, so that research is not accomplished or unit counts are reached late, causing further misplays.

I fixed the latency compensation bug yesterday. To do it I had to completely rewrite the routine that chooses which larva to morph into the next unit, so I took extra time and added features. Now it is more general: It is divided into one step that decides which bases are better locations for the next unit, and second step which tries to find a larva near one of those bases. The old version already knew that it’s better to make a drone at a base which needs more drones. I taught it in addition that if there are corsairs or wraiths flying about, and we have spores to defend, it’s better to make overlords at a base with a spore.

As mentioned here, I plan to release a bugfix version Steamhammer 3.3.6 first, then get back to work on my real project of 3.4. I’m often wrong in strength estimates, but even so, if I can fix the critical bugs I think 3.3.6 should be stronger by 50 elo points.