Starcraft AI blog

Here is the path I followed to discover (what I conclude is) the fastest possible lurker rush. Whew, that was hard work. The build can afford 2 lurkers. I’ve never seen anything similar before.

All the timings are of course with Steamhammer’s execution, which is reasonably good but hardly perfect. For example, mineral locking is not ideal, and drones can make unnecessary movements when building.

I found a simple improvement to yesterday’s supposedly optimal build, by heeding my own lesson: It makes sense to delay 1 drone now to get 2 drones sooner, provided you can use the income of the 2 drones in time for the next step. It does not make sense to delay a drone for no benefit! Simply move the delayed drone before the overlord for a faster lair and faster lurkers. The lair timing is then gas-limited, and making the overlord immediately before the lair does not delay it.

"9Pool8GasLurker" : { "Race" : "Zerg", "OpeningBuildOrder" : ["go nonadaptive", "5 x drone", "spawning pool", "extractor", "2 x drone", "overlord", "lair", "2 x drone", "hydralisk den", "lurker aspect", "drone", "3 x hydralisk", "3 x lurker"] }

I got a lair timing of frame 2972 and a lurker timing of 6286. Ideally, lair start at 2972 + lair build time 1500 + lurker aspect research time 1800 should give a lurker timing of 6272, which is 14 frames earlier. Watching the game by eye, lurker aspect has its prerequisites on time and seems to start instantly when the lair finishes, and the lurker morph seems to start instantly when lurker research finishes. There could be a few frames of unnecessary Steamhammer execution delay, but I suspect that the bulk of the 14 frame slippage is Brood War latency stuff that is not accounted for in the build time. Maybe some other day I will instrument it and track down those 14 frames.

Now that the lair is gas limited, can we speed it up by getting gas earlier? 9 gas 9 pool gave me lair timing 3139, limited by the spawning pool. For a faster spawning pool, drop the drone in front of the pool for 9 gas 8 pool, and collect just enough gas at each step. That got me a lair timing of 3022, faster but still limited by the spawning pool—and not fast enough. Since the lair is slower, there is no point in timing out what happens after.

"9Gas9PoolLurker" : { "Race" : "Zerg", "OpeningBuildOrder" : ["go nonadaptive", "5 x drone", "extractor", "drone", "spawning pool", "drone", "overlord", "lair", "hydralisk den", "lurker aspect", "hydralisk", "lurker"] },

"9Gas8PoolLurker" : { "Race" : "Zerg", "OpeningBuildOrder" : ["go nonadaptive", "5 x drone", "extractor", "go gas until 100", "spawning pool", "2 x drone", "overlord", "lair", "go gas until 375", "hydralisk den", "lurker aspect", "hydralisk", "lurker"] },

The next step is to reduce the number of drones. Will that speed up the lair, or slow it down for lack of resources? I optimized this build through several steps which I won’t show. Notice that the second overlord is delayed until after lurker research starts! The overlord costs too much; otherwise lurkers would be delayed. Lair timing: 2868. Lurker timing: 6182. Success! Again there are 14 frames of slippage.

"8Gas7PoolLurker" : { "Race" : "Zerg", "OpeningBuildOrder" : ["go nonadaptive", "4 x drone", "extractor", "go gas until 100", "spawning pool", "2 x drone", "lair", "drone", "go gas until 500", "hydralisk den", "drone", "lurker aspect", "overlord", "2 x hydralisk", "2 x drone", "2 x lurker"] },

Can we get away with 7 drones? When does the drone count go too low to support the tech? 7 gas 6 pool got the lair slightly faster than 8 gas 7 pool above, but it was limited by the pool timing, so I went back to pool before gas. My first try with 7 pool 6 gas got the lair substantially faster at 2649, but there were not enough resources to start lurker aspect on time, and lurkers were delayed to 6465. I tried different ways to get extra drones in. The feasibility is narrow: It breaks the build to insert 1 more drone anywhere... or to shift any drone earlier... or to collect more gas than specified. In the end, I was able to get lurkers out faster overall, despite delays both in the lair and in starting lurker aspect. Lair timing: 2718. Lurker timing: 6080. This time there are 62 frames of slippage, most of which are due to a delay in starting lurker aspect because minerals are short.

"7Pool6GasLurker" : { "Race" : "Zerg", "OpeningBuildOrder" : ["go nonadaptive", "3 x drone", "spawning pool", "extractor", "go gas until 350", "2 x drone", "lair", "drone", "hydralisk den", "lurker aspect", "2 x drone", "go gas until 250", "overlord", "2 x hydralisk", "2 x lurker"] },

I find it clear that 6 pool or 6 gas will not work. The delays due to lack of resources will be longer than the gain from starting sooner. I didn’t bother to try.

The final build must be close to optimal. But it’s possible that there is a faster lurker build. I tried a lot of ideas, but I did not examine every detail with mathematical thoroughness; it is too big a job for the time I was willing to spend on it. At some point, maybe I will do as Dave Churchill did in his thesis: Search programmatically through the tree of builds to find builds which are optimal for different purposes. The giant search for optimal builds is a perfect computer job.

Next: Competitive versions of some of these builds.