Starcraft AI blog

All 3 races have tricks they can sometimes do, depending on the starting position, to make workers spawn a little closer to the minerals they will mine. It provides a very small macro boost, starting early in the game when it matters most. I doubt that any of these tricks will make much difference in bot play; mineral locking gives a much larger edge. I haven’t noticed any bot implementing them. (Do you know of one?) On the other hand, they’re not hard to implement, and might possibly help the strongest bots.

terran

A fresh unit, just produced, appears to the bottom left of the building that produced it, like this new-made SCV:

If the minerals are on the left, cool. But in this case, the minerals are on the right, and the SCV starts far away. To get the SCV to spawn closer to the minerals, block the space on the left with your first supply depot. The left edge of the depot (3 tiles wide) is aligned with the left of the command center (4 tiles wide).

Then the SCV appears below the command center and to the right of the supply depot. You use your first supply depot because you want to start gaining the macro advantage (small as it is) right away; it matters most at the start of the game. Starcraft has consistent rules for where new units appear: As far toward the bottom and left of the producing building as possible. If you start with a barracks first, you can align the barracks (4 tiles wide, the same as the command center) exactly underneath, so that the SCV appears even closer to the minerals.

If SCVs are returning minerals at the time and place where the new SCV would spawn, blocking the spot, then the SCV may appear farther up the right side. That should not bother a bot in the least.

Pro terrans do this trick with their first depot. At their level of play, they think it’s worth it.

By the way, exit blocking tricks like this have game uses outside of macro. For example, if zerglings are attacking a barracks and the barracks is producing a marine, then zerg controls where the marine will spawn. Lings at the bottom left of the barracks can pull back a little so the marine spawns there, already surrounded. Pros do this too.

protoss

Protoss can do essentially the same trick with their first gateway, if the minerals are to the right of the nexus.

Pros do not use this trick, as far as I’ve seen. The gateway should start only a little later than the terran supply depot, so I think the trick should still bring a tiny macro advantage. I suppose that pros find other factors more important for gateway placement.

zerg

Zerg produces drones from larvas, and exit blocking tricks don’t apply. Zerg has a completely different trick, apparently a weird bug in Starcraft, that is useful if the minerals are to the left of the hatchery: The larva trick. Except for this trick, larvas are not controllable. When performed by a human, select any larvas you want to move to the left together with an overlord, and hit stop. You can use a controllable unit other than an overlord if you don’t mind it stopping. The selected larvas will slide to the left side of the hatchery and stay there. And the overlord stopped, so you probably want to send it on its way. When a new larva appears, you have to repeat the trick to make it move—no trouble for a bot.

When I tested it in Steamhammer, I found that the overlord was not necessary. Apparently the overlord is only included to bypass UI limitations that BWAPI does not emulate. This simple test code, which runs only once on frame 0, worked for me.

  if (BWAPI::Broodwar->getFrameCount() == 0 &&
      BWAPI::Broodwar->self()->getRace() == BWAPI::Races::Zerg)
  {
      Bases::Instance().myMainBase()->getDepot()->getLarva().stop();
  }

Bases::Instance().myMainBase()->getDepot() returns the main base hatchery. BWAPI provides getLarva() which returns its set of larvas.

The larva trick also has game uses outside of early macro.