Mark Twain advised writers that every time you want to write “very” you should put “damn” instead: “Supporting Sparkle is damn hard.” Your editor, he said, would remove the word “damn” and your writing would be as it should. Well, I don’t have an editor. Supporting Sparkle is damn hard, and my writing is as it should be.
When I first looked at the AIST competition, I posted “I will have to spend time surviving tricky map features and won’t have much for thriving with the important play features like mineral-walking drones into the third world, or linking up island bases with nydus canals.” I was right. Steamhammer can survive on Sparkle and Third World, but it doesn’t have the skills to play the maps as they were meant to be played. I did not have the time to implement them. That’s the theme of this post: Not enough time.
the Require: feature
Since Sparkle requires specialized openings, I wanted to implement at least Require: { “map” : “Sparkle” } for openings in the configuration file. See yesterday for the many ways in which my plan was flawed. I invested too much time before I realized that it would not pay off, and I had to put in a hack and move on to other stuff. It was not fun. I’ll rethink this completely for the next version.
the opponent model
You can’t get 5 pooled on an island. You don’t have to do anything special if the enemy makes a fast factory—you expect that on an island map. The plans that Steamhammer knows how to recognize don’t matter on island maps, and I had neither time nor test opponents to work on recognizing island plans, much less to counter the plans. It made more sense to short-circuit the plan recognizer, or you might say, to correctly recognize that none of the known plans mattered.
Still, Steamhammer does know 3 Sparkle openings, and it would have been nice to rely on the opponent model’s opening selection to pick the ones that worked better. But that was problematic too, because of how the opponent model tries to generalize across maps. Most maps you can generalize across: If this opening worked well against this opponent on Circuit Breaker, it has a good chance to work on Roadrunner too. But island maps, and concept maps in general, call for specialized choices; you can’t generalize from a concept map to any other map, or vice versa. I’ll remember that when I work on opening statistics, one of the next planned features. I learned that Steamhammer should be able to measure how much a map is like other maps, and generalize appropriately.
island transport
When I surveyed the AIST S1 map pool, I thought: Hmm, Sparkle is an island map and Third World is a kind of semi-island map where workers can pass between the map halves by mineral walking. The important skills are mineral walking, drop, and placing nydus canals. What combination of skills should I aim for first? Drop is the most flexible and the most useful overall, but it will take a ton of work to implement in Steamhammer because the existing infrastructure is weak. Also drop is slow and awkward for moving units around. Mineral walking drones is comparatively easy, and it is useful on a modest variety of maps. Also mineral walking doesn’t require research; when you can use it at all, you can use it from the start of the game. Nydus canals are the best way to move units between islands in the late game, they’re useful on almost all maps, and they’re related to pathfinding which I want to work on, so now is a good time to work on nydus. Plus Sparkle provides neutral zerg buildings on islands, so zerg can create nydus connections without needing drop. Mineral walking and nydus were my choice; drop is not required for zerg to play either map.
As it turned out, I didn’t have time to implement either feature. Steamhammer is restricted to its starting island and cannot move land units to another island. Zerg will win with air power, or it will not win. On Third World, Steamhammer is restricted to the starting half of the map, which has only 5 bases including the enemy main and natural. It’s disappointing.
island strategy
Ideally, I wanted to provide an air strategy with an optional switch into a late game ground strategy of securing islands with hydralisks by nydus. As the deadline approached, I foresaw that I would not have time for nydus, so I spent a few days getting the air strategy tuned up. I optimized the 3 Sparkle openings (1 hatchery muta, 2 hatchery muta, and 3 hatchery muta) until improvements became small. Once I realized that I could not finish the Require: feature and that the opponent model had to be more or less turned off, I simply set each opening to be played 1/3 of the time. It’s as good a guess as I can make.
At first, the mutalisks were uselessly weak. To get anywhere, I had to make changes to the strategy boss to give it some understanding of island maps. First, correct the unit mix so Steamhammer sticks with air and doesn’t decide to switch to lurkers or ultralisks, which without drop or nydus have no offensive value. Even after that, Steamhammer often lost against the weak built-in AI. I continued: Reduce ground upgrades and eliminate unnecessary research to save gas for mutalisks, and get air armor upgrades. Now Steamhammer can defeat weak or unprepared opponents. Improving mutalisk and scourge micro would help more, but that would have taken way too long.
In Candide’s best of all possible worlds, meaning several versions from now, Steamhammer should support drop and have the option of following a ground strategy on an island map. Ideally.
ground units
Steamhammer still tends to make many zerglings with its leftover minerals, which it accumulates because it has too many drones for what it is doing, which is because it doesn’t understand that it is stuck on one island. Well, its economy control skills are lacking overall; it only wants to make drones up to a limit depending on the number of mineral patches and geysers it has. The zerglings are at least useful for keeping an eye on the island and stopping drop attempts.
At first, the zerglings tried to reach the enemy base, piling up at the island edge. I expected that; it is part of what MapPartitions is for. I updated the tactical analyzer (primitive as it is) to only send ground squads to places they can reach. Now the zerglings understand that they can’t get to any enemy base, so they “explore the map,” running back and forth between corners of the starting island to keep an eye on things. Incursions should be spotted right away.
There is a bug with assigning air units to a ground squad. Despite a fix in the previous version, it still happens sometimes; it must be a second bug. I’ve seen guardians assigned to the ground squad when they should not be, which on Sparkle causes this weird behavior: The squad is sent as usual to explore the map, but because it includes air units it knows it can explore the entire map. The zerglings again gather at the edge of the island, while the guardians slowly drift from empty point to empty point. The bug doesn’t cause much trouble on land maps, but on islands it’s serious.
Steamhammer still makes defensive sunkens as usual when it sees a scary enemy ground army. It doesn’t know whether the army might appear at its base.
At some point in the 1.5.x series I will make squads more dynamic. I plan to make it illegal for a squad to have ground units in more than one map partition; if a ground unit moves from one partition to another, it will be put into a different squad which belongs to that partition. Ground units in transports will belong to a different squad yet. Squads won’t have to worry about their units being stuck in separate places, and should have an easier time making decisions.
island scouting
Steamhammer’s original Recon squad is a small ground squad that scours the map for enemy bases, and when it finds one, may attack if the base is poorly defended. On Sparkle, Steamhammer only found a new enemy island base when it happened to stumble across it while doing something else. I changed the squad assignment so that on an island map, the Recon squad consists of 1 overlord. Before overlord speed finishes, the overlord moves so slowly that its recon target often times out before it gets there, switching the overlord to a new destination, but the overlord still crisscrosses the map and sees stuff that wouldn’t otherwise be seen. Once speed is done, the overlord scouts nicely. Steamhammer has no overlord survival skills, so the overlord will happily fly over turrets and generally has no fear. I’m hoping that the scouting info makes up for the vulnerability. But in test games, Steamhammer loses overlords at a high rate.
destructible blocking buildings
The low ground natural base on each starting island has a psi disruptor building on top of the geyser. Every race can build a refinery building under the psi disruptor, but none can mine the gas until the psi disruptor is destroyed. I found by experience that building an extractor before destroying the psi disruptor was a poor idea. First, the extractor apparently sticks out beyond the edges of the psi disruptor at some points, so that zerglings attacking the psi disruptor have to choose their target carefully and it takes longer to finish off the neutral building. Second, when the psi disruptor is destroyed, usually—though not always—the extractor is destroyed at the same time. I’m not sure how that happens, but it explains why I’ve always seen pros destroy the building first and take the gas after.
Yesterday I described Steamhammer’s new multi-part system to destroy the psi disruptor, and how the openings are adjusted to get the right number of zerglings at the right time to take the gas when needed. It’s complicated and it is needed only on occasional concept maps like Sparkle.
the geyser with a crystal on it
The high ground natural has a geyser with a big crystal on it. Only zerg can mine from that geyser. Steamhammer does not believe that it can take this gas, and never tries. I have a theory about why, but I haven’t looked into it; I chose to deal with the destructible buildings first, and ran out of time. It may have been the wrong decision. Maybe I should have skipped the destructible psi disruptor and figured out how to take the crystal gas.
As zerg, Steamhammer should be able to mine 3 geysers on its starting island. It is only smart enough to get 2.
taking the high ground natural
BWTA believes that the high ground natural base does not exist; it does not locate a base there for any race. Maybe it understands that the neutral zerg lair spreads creep which blocks the base placement. If so, it is a mistake: Zerg can build on the creep and mine the gas, and terran and protoss can either destroy the neutral lair and wait for the creep to dissipate, or (since they can’t mine the gas) locate a base on the opposite side of the minerals. Pros commonly take the opposite side of the minerals. To figure all this out needs a sophisticated understanding of the situation.
Steamhammer’s map analysis doesn’t understand the base either. It doesn’t realize that the neutral lair spreads creep, and tells all races they can build a base in the normal spot. Or, in some starting positions, near the normal spot; it sometimes displaces the base (maybe there’s an off-by-one bug). Since Steamhammer will be playing zerg in AIST and no other map has the weird features, it was good enough and I left it alone.
Steamhammer recognizes the neutral lair as a “blocker” that should be destroyed, but does not destroy it. I think the bug happens because of a use of BWTA that I didn’t remove. It does no harm in practice, so I left this one alone too.
I decided to do all this stuff and I’m not convinced that it was worth it. I could have concentrated on Third World instead. I would now have the mineral walking feature at a minimum, and it could share some pathfinding code with nydus canals. On the downside, I would have done less to improve Steamhammer’s play in AIST, because moving Sparkle from can’t-win to can-win is a bigger jump than moving Third World from can-win to plays-nicely. On the upside, I would have had a feature that is more widely useful. I feel some regret. I could have chosen to play somewhat better on a variety of maps, and instead chose to play substantially better on one map, Sparkle, that may never matter again. And that substantially better play is still painfully weak.
