Starcraft AI blog

I enjoyed the game TyrProtoss vs Simplicity on Benzene. Simplicity is not ranked high, but it plays some good games.

The just played Simplicity vs BananaBrain is a fine game by Simplicity. The early defense against zealots was especially well done, and Simplicity’s tech and attack decisions were good. Recommended.

In the meantime, I’ve hit a bug that’s slowing me down. I found a reproducible case where production fails because it tries to use the same larva to produce two drones. It looks like slippage in BWAPI’s latency compensation: The production system picks a larva to produce a drone. Ask the type during the same frame after giving the morph order, and you get egg; that is latency comp at work. Ask again a couple frames later, and the egg has turned back into a larva; the production system picks it a second time, and the second morph can only fail. I think it should be easy to work around, but can it be fixed? Latency compensation is not expected to be perfect.

It makes me wonder what other slippages may be hiding under the rug.

Yesterday’s game Simplicity vs Locutus on Andromeda on BASIL starts out as one of the most entertaining bot games I have seen. The pictures show some of the cool stuff that Simplicity tried—with success. Then, after a tremendous fight where each side pressed temporary advantages and maxed its army, the replay loses sync and OpenBW cannot show the last half of the game.

Queens with broodling. The Research tab shows broodling research, and there are broodlings on the ground. Simplicity made 8 queens early and even researched queen energy, and the queens paid for themselves with interest. When Locutus attacked, zerg sent out as many queens as had energy to simultaneously spawn broodlings, helping to break the attacks. It’s a simple way to coordinate the queens to get tactical results, and is more effective than the common bot approach of using the queens as attrition weapons. Simplicity’s queens eventually died to corsairs; with more careful play, they could have lived to the end of the game, because Locutus was not skilled with its corsairs.

Island base with static defense. The overlord on the left has just dropped off another drone to join the miners.

Drops. Simplicity repeatedly dropped small numbers of units into the far end of Locutus’s base, and Locutus did not react properly. The drops were not decisive, but were cost-effective.

Both sides maxed their supply, or nearly so. At that point, Locutus had better upgrades but Simplicity had a larger army. Locutus could not keep its natural safe. Luckily for protoss, it was already mined out.

But Locutus had a stronger economy with more bases and a large bank of resources, and Simplicity ran out of resources. The desync hides the end of the game, which timed out after an hour. I believe that Locutus wiped out all zerg it could reach on the ground, and then had no answer for the island base. When the game timed out, BASIL gave the win to Simplicity on points. Moral: You need at least enough island skills to make air units to attack inaccessible bases.

Simplicity has been getting updates, and an update yesterday was apparently when it gained overlord drop skills. (There’s another update today.) It is the first zerg bot that I have seen use drops (well, in public at least). The drops look a bit stereotyped, with about 8 overlords loaded up in the main and sent (usually along the edge of the map) toward an enemy mineral line—it looks as though the drop happens when the overlords find targets to drop on. That makes Simplicity the first bot I have seen do mass drops, a unique skill.

I found 3 drop games on SSCAIT. Curiously, all 3 games are on Moon Glaive, although Simplicity does research drop on other maps. The less impressive games are Simplicity-Juno aka Yuanheng Zhu and Simplicity-NiteKat terran. Drops definitely did not change the outcome of those games. The best drop game is Simplicity-WillBot, in which WillBot randomed to terran.

The first drop started to load up at the zerg main just before 16:00 into the game—while a terran attack on the natural was underway, not the most auspicious time. Apparently Simplicity does not put much analysis into the drop decision. In the picture, the two players are roughly even (objectively, with no defilers in sight, the big terran army should win, but neither bot has the skills). The selected overlords are exactly those that are loading units. In the minimap, notice the long tail of terran units moving toward the zerg natural; the terran attack was kind of piecemeal.

Loading proceeded slowly, I guess since the ground units were distracted by the terran activity, and the overlords set out at about 16:40. The overlords proceeded counterclockwise around the edge of the map toward the terran main. Meanwhile, terran diverted to annihilate the zerg base at 9 o’clock before returning its attention to the zerg natural, and zerg units that were still on the ground bypassed the marines and tanks and headed for the terran natural to counter. Simplicity’s decision was good. Attacking the terran bases from both sides put WillBot into a difficult situation where it was tough to make the right choices.

The drop started to land at about 17:40. WillBot defended the ground maneuvers poorly; it left tanks forward to pressure the zerg, and lost them to zerglings, and sent marines back to defend, where they ran full tilt into burrowed lurkers. In the picture, notice that both sides have lost workers and WillBot has already fallen behind before the drop happened. The white dots in the terran natural are lurkers which are in range of the command center.

WillBot did finally clear the attack, but was far behind. Simplicity made 2 follow-up drops to finish off the terran main.

All in all, the mass drop skill could use improvement—but you could say that about almost any skill of any player. In Steamhammer, I have held off on zerg drop because I think it requires tactical analysis that the bot can’t do yet. In this game we see that mass drop can be a scary ability even with little tactical calculation behind it.

The new zerg Simplicity has been getting a lot of games. Taking a peek at the binary, I see that it is a Java bot, and it lives up to its name: The compiled code is quite small, and most of the space used is in libraries.

Simplicity’s play is reminiscent of Proxy; it plays a similar mass hydralisk build with a similar late game addition of ultralisks. It’s a good general-purpose choice for a new bot, so no complaints there. At the same time, it puts on a direct and predictable kind of pressure. Proxy switched away from that build for both terran and zerg opponents, with good reason. (Well, Proxy still goes hydra against terran mech.)

Simplicity is weaker than Proxy, though (including the early Proxy before it was improved). Simplicity has been scoring around 50%, but many of its games are against low-level opposition. I forecast that its initial elo will come in below 1900. Simplicity does not have strong macro, and its tactics are clumsy. Also it appears to build a fixed amount of static defense, not adapting to the situation.

Simplicity does midgame scouting with reconnaissance in force, the same idea as Steamhammer—not common among bots, and unheard of among new bots made from scratch. It looked effective in games. I thought that that was Simplicity’s most impressive feature.

All in all, nothing dazzling, but good for a brand new bot, especially such a small one. After only one day, the bot got an update that I thought improved it, so development is proceeding rapidly. Any bot that improves rapidly has a chance to climb high.

Next: Analysis of potential paths.