Starcraft AI blog

I wrote up a few fun games between Steamhammer and its rivals. The first of the two games against McRave is especially exciting.

versus Arrakhammer

Arrakhammer is successful, but its ZvZ matchup is not as strong as the others. It has been losing a lot of games to Steamhammer and winning rarely. In Arrakhammer vs Steamhammer, Arrakhammer went with a fast mutalisk opening and Steamhammer chose a zergling opening. Arrakhammer made 3 sunkens to hold the zerglings... and they weren’t enough.

Steamhammer hit a bug this game (fixed in the next version). It intended to take its gas early, but incorrectly thought it couldn’t. If it had played as intended, it would have had fewer zerglings but they would have had speed, and I don’t know how the game would have gone.

versus McRave

McRave has been playing a lot of games against Steamhammer, with increasing success. McRave has been opening with forge-expand—it may sound simple but it is a sophisticated build that is difficult for a bot to master. Steamhammer plays its usual random selection. Many of the games are stomps for one side or the other. Here are the 2 I found the most entertaining.

In a game on Moon Glaive, Steamhammer went 12 hatch into 3 hatch ling, which sometimes breaks the cannons and wins outright. Not this time, though. Both sides struggled with weaknesses. Steamhammer went hydras and then switched to mutas, then switched back to hydras, repeatedly suiciding units all the while. McRave blocked its dragoons in its base with buildings and only got zealots out on the map.

McRave maxed its supply earlier, capping its workers at 60 probes and saving the rest for army. Since only zealots and probes got out of the base, Steamhammer was able to take the map and grow a larger economy, going to 75 drones. Finally Steamhammer got ultralisks and, nearly maxed itself, busted the cannons, letting McRave’s army free. What would win, the bigger army or the bigger economy?

Protoss held the ramp. The ultras could not break in. The battle went on and on and on as both sides burned resources, and the blue ramp on Moon Glaive will probably be red forever. Both bots controlled their units poorly in the usual bot way—more moving than shooting, all butting heads and no finesse. Eventually reavers and storm forced the zerg back and protoss gained map control for the first time.

With its ample economy, Steamhammer was soon maxed again, while protoss had lost many probes in the fight. Protoss had held its ramp, but could not maintain map control for long. A detachment with ultralisks defeated the reavers in the center while most of the zerg army reduced the protoss main, and only mop-up was left.

A game on Andromeda went differently. Steamhammer chose a less economic opening and reacted sluggishly to the cannons. It ended up going mass lings with mutalisks. This time McRave was ahead in both army and economy.

Protoss moved the army to protect a center expansion. Mutalisks had been picking off probes from the undefended mineral only base, and eventually they moved forward far enough to notice that the defending units had departed. Muta-ling broke the cannons and rampaged through the 3 protoss bases around the main. Probes died, and suddenly zerg had a chance. Would the protoss army get back in time to defend?

McRave reacted not by defending, but by countering Steamhammer’s distant corner expansions. Zerg ought to have finished off the protoss tech and production before anything else, but that is not how Steamhammer is coded. Zerg ran to defend, creating a complex situation—and Steamhammer is vulnerable to tactical collapse in complex situations. The zerg units in the picture are not attacking the mined-out center expansion, they are moving past the enemy while taking fire. On the minimap, notice the diagonal line in two colors. It was a debacle.

About a dozen bots have been updated in the last week, and a bunch of new bots have been uploaded this month. We’re going through a burst of activity similar to the one around the previous SSCAI tournament.

The reason might be that the CIG tournament is coming up. The timing fits, but other evidence is not as clear. I don’t see an upcoming tournament as a good reason to release new rushbots, or to put out an instance of McRave playing terran (Sparks). But only the bot authors know their own motivations. Maybe some will comment?

A tournament in April or thereabouts might be a good way to maintain interest, if tournaments really are good motivation. Thinking about the timescale on which interest waxes and wanes, I guess April would be about right, depending on how long the tournament runs. The CIG and AIIDE tournaments are tied to academic conferences and can’t be moved around the calendar, and SSCAIT traditionally runs starting near the end of the year. It’s possible that a gap-filling tournament, if people see it as important, might keep the scene lively. Well, it’s a speculative idea, but spacing tournaments around the calendar makes sense. Authors should have time to make updates before the next submission.

Sparks, by the way, has a pretty good strategy. It is McRave set to play terran, and obviously some thought has been put into the terran, though McRave’s protoss play is more sophisticated (so it will presumably play as protoss in tournaments). I imagine it is named after “sparks terran,” which was traditionally a sunken bust timed for just before mutalisks came out. (Sparks terran is a strategy I’ve been keeping in mind as tough for a zerg bot to counter when following a mutalisk plan. Luckily for Steamhammer, it’s not easy to implement well. Tscmoo comes closest but is missing skills.) Today people often say “sparks terran” and mean nothing more than straight infantry play.

Anyway, Sparks the bot opens with 2 barracks and puts its first marines in the mineral line for safety. When it has enough it transfers them to the ramp, arranging them in a nice arc. When stim is done, upgrades are started, and medics are available, it moves out to attack. A terran should stop the attack easily; a protoss shouldn’t have much trouble if it saw what was coming; but a zerg needs to pay attention and defend smartly to hold. It’s a good attack timing.

Two surprise upsets today caught my interest.

new from MadMix

The game MadMix by Oyvind Johannessen vs McRave surprised me.

McRave fell out of the top ranks a while back, but has lately been climbing back up. I’m guessing that some new subsystem was switched in a while back, and it has taken this long to work the bugs out. After a long drought and a bunch of tries, the new version of McRave notched its first recent win versus Steamhammer today (and another shortly after). I expect McRave will keep rising and return to the top 5 before long.

MadMix is brand new, but already has a big update. The initial version made most units for all races, but never researched upgrades or tech. Today’s version researches most upgrades and at least some tech, so the mix is even madder!

In MadMix versus McRave, random MadMix rolled zerg and started off with fast lurkers. McRave is much higher ranked and has a better build order, better tactics, and better micro. McRave had a vastly superior force in the early game, but for some reason chose not to engage—mistake #1. When the lurkers came out, McRave had no detection and was contained despite MadMix’s poor combat skills.

MadMix slowly expanded to many bases while McRave was contained. McRave made a robo facility but never added an observatory, so it had no detection—mistake #2. I’m sure it’s an oversight or bug and will be fixed before long. McRave still could have made a nexus at its natural, added cannons for detection, and maintained a chance to win, but instead when the protoss main mined out, McRave resorted to long distance mining—mistake #3. Even so, McRave’s macro was stronger and the protoss army remained dominant. In smaller attacks, MadMix retreated support units and unburrowed lurkers each time targets moved out of range, so the forward lurkers tended not to live long. For a lurker, staying underground and restricting your enemy’s mobility can be more important than having a target.

McRave was strangely passive this game, moving its army mostly in response to immediate threats. With zerg on many bases and protoss long distance mining, the writing was on the wall. Eventually MadMix started mass attacks and broke through to win. The picture is from shortly after MadMix’s army first became the larger one (notice the worker counts). In the upper left you can see lurkers holding an isolated protoss force at bay; for some reason, MadMix made better use of its lurkers during the breakthrough attack.

The upgrades tab shows that MadMix did a ton of upgrades this game, even overlord sight range. You can see scourge, and offscreen is a devourer, even though McRave never made an air unit. The zerg unit mix is genuinely mad. It did not make queens, which may mean that it realizes it needs to know how to use the spells first.

Maybe another update soon will see MadMix using most tech, too. In any case, MadMix is already ranked higher than Travis Shelton, the other random bot with a wide choice of units.

Randomhammer gets a win over Krasi0

Randomhammer scored an upset win over Krasi0 with a vulture drop. I knew the drops would pull some good wins.

Randomhammer (this time) sent its dropship the short way around the edge of the map to Krasi0’s base. Randomhammer’s vulture micro was disappointingly poor, but even so the drop was moderately successful; it killed few SCVs, but stopped mining for a surprisingly long time as Krasi0 cautiously backed away.You can see in the production tab that Randomhammer is expanding and adding units while Krasi0 is producing nothing.

Krasi0 may have seen the building starport just before its scout was chased away by marines. In any case, it made goliaths with a few tanks mixed in, a good counter to the air units and vultures which were the only units it had seen indications of. But Randomhammer immediately switched to tanks (it’s a hardcoded tech switch—Steamhammer’s terran and protoss strategy is ultra-simple), and expanded not once, but twice.

Krasi0 delayed its expansion and did not have enough gas to make many tanks alongside the other tech it wanted. With 3 geysers, Randomhammer had greater tank numbers and was able to push through and win despite Krasi0’s superior tactics and unit control. Knowing how to position tanks on high ground is great, but if you have 2 tanks versus 6, it’s not great enough.

The SSCAIT news is that McRave and Microwave have been steadily climbing up the ranking. I’ve been watching it happen for a while. Just recently McRave edged past Steamhammer in elo, pushing Steamhammer down from #4 to #5. Today Microwave has moved ahead of McRave. The 3 bots seem quite close in strength for now.

Maybe the two authors would like to comment on their improvements?

According to my machine learning algorithm, the important common factor between protoss McRave (made from scratch) and zerg Microwave (a Steamhammer 1.o fork) is the -ave name. I speculate that there may be a connection with Aves, the birds. In any case, the hypothesis suggests that PurpleWave may be the next climber, and I hear that plans have been laid.

Now back to work. My tactical changes have introduced some new misbehavior that must be addressed, and not with “hello, misbehavior.”