Build

Now that we are training our workers, eventually we'll be running out of supply.

To do this, we need to build some buildings that give us extra supply space.

Again for Zerg this would be an Overlord which is morphed from a Larva

larva.morph(UnitType.Zerg_Overlord);

Building buildings

Giving a command to build a building is as simple as

worker.build(building, location);

However, figuring out what, who, when and where you should build is not that trivial.

What

Something that gives supply

UnitType toBuild = self.getRace().getSupplyProvider();

Who

A random worker that is not already doing something except gathering minerals (as to not disturb a potential other future builder or future scouter)

Unit builder = null;
for (Unit unit: self.getUnits()) {
    if (unit.getType().isWorker() && (unit.isIdle() || unit.isGatheringMinerals())) {
        builder = unit;
        break;
    }
}

When

We need to build supply buildings only if we are going to run out of supply space in the near future (and did not reach our supplycap of 200 units yet).

if (self.supplyTotal() - self.supplyUsed() <= 2 && self.supplyTotal() <= 400) {

}

Note: because of how StarCraft works, Zerglings being only half a supply on the screen (0.5), supply in BWAPI is doubled compared to the number that the game displays. A Zergling costs 1 supply, a worker therefore costs 2 supply, and a supply building gives double of what you see on the screen. In the end it is the same, only this can be confusing for beginners when starting to work with BWAPI.

You can easily check for yourself with these handy methods

unitType.supplyProvided();
unitType.supplyRequired();

Where

Building placement in StarCraft is very important but also quite complex (e.g. walls, canon placement, etc.).

For this tutorial however we'll cut some corners and just build around our starting location and use a built-in method to get a TilePosition on where to build (which you shouldn't use for your real bot as it is quite unreliable).

TilePosition buildLocation = game.getBuildLocation(toBuild, self.getStartLocation());
builder.build(toBuild, buildLocation);

Problem

However have a problem right now, where this build condition will be true for a very long time, as long as the building is finished, so a lot of workers will try to build a supplyprovider at the same time. We can add a little hack by keeping track of our "queued" supply, e.g. the supply that we will have in the future.

NOTE: this is just a hack to keep the tutorial going, you should implement your own building building tracking system (e.g. my approach doesn't scale at all because it only works for buildings giving supply).

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