Release 3.5.10

Tournament preparation

• Special preparation against 9 prospective AIIDE 2021 opponents—the ones it might make a difference against, plus Stardust where Steamhammer is at risk of scoring zero. I followed the same preparation plan as last year: For each opponent, choose a small number of builds that have historically won, or that seem to have good chances, and enter them into history as fictional single winning games. Let learning do the rest.

It amounts to giving hints “try this a few times before giving it up.” Steamhammer has a better chance of finding good builds early, and is not weighed down with masses of outdated learning data if the opponent brings surprises.

Information

• Remember whether the enemy has used psionic storm this game. I wanted to feed the information into lurker spacing decisions, but ended up not implementing lurker spacing, so the feature is unused for now. There are other potential uses.

Static defense

Changes to static defense include tuning to make the right amount in different situations—zerg static defense is expensive, and needs to be worth it. I think the tuning is improved versus terran, fairly good versus protoss, and still weak versus zerg.

• Fixed a crash due to division by zero. The bug fix does not affect strength, because the crash only happened when Steamhammer had no bases left. Yes, it was dividing by the number of bases. How easy it is to forget that you may already be dead! For my part, I forget that nearly every day.

• Morph forgotten creep colonies into sunkens or spores, if and when they happen to be needed. The building manager sometimes slips up and forgets to morph a creep colony that was intended to become static defense. If defense is not needed, it will remain a creep for the time being. When the static defense planner decides that it is needed, it may turn into either a sunken or a spore. At some point I’ll implement tactical analysis and Steamhammer will have an idea of when the enemy might attack in strength. Then it will be able to leave all colonies until they are needed.

• Try to place spore colonies in the mineral line, rather than somewhere vaguely near the hatchery. This helps ZvZ the most.

• Make one sunken colony less per base, compared to before.

• If the enemy has many tanks with siege mode, sharply limit the number of sunkens. They become a waste of minerals.

• Make more spores versus mass wraiths and mass scouts.

Buildings

• Anti-cannon sunken reaction failed due to errors in building placement introduced in a recent version. Fixed.

• Other attempted improvements to anti-cannon sunken placement.

• Added configuration option Config::Skills::UseSunkenRangeBug so that I can turn the feature off when it’s not allowed. It’s part of building placement; see BuildingPlacer::getAntiCannonSunkenPosition(). It’s off for AIIDE, where use of the bug is not allowed. It’s on for SCHNAIL, since it’s allowed in human games.

• Steamhammer might try to build a macro hatchery directly on top of the main hatchery in the opening. The hatchery failed to build and the drone assigned to build it was left idle for a time, a serious breakdown. Fixed.

• In rare cases, a building might be placed invalidly so that it could not be built. Fixed.

Squad orders

• Each squad keeps track of the last time its order was changed to a different target. It also remembers the most recent frame that any cluster of the squad attacked, and the most recent frame of a retreat. (“Attack” usually means that the combat sim said “go attack”, not that any unit fired a shot.)

• The above info is used by the air squad in deciding whether to keep attacking its current target, or seek an undefended target of opportunity. If the last attack was a long time ago and the last retreat was just now, then the mutas are sitting around and should try another target. They look for the closest undefended thing and try that instead. Unfortunately, the closest undefended target is often as inaccessible as the original target—it can be attacked in theory, but Steamhammer doesn’t have the smarts to do it in practice. So far, the feature is not worth the effort I put into it. I think it will become worth it when I implement more pathing and harassing skills.

• In defense, defeat enemy proxy pylons when nothing more dangerous threatens. There was always code to do this, but it was broken in a subtle way. The method for assigning units to squads is too complicated; I’ve got to find a better idea.

• In defense, count an enemy proxy creep colony as 2 units, not 1. When pulling drones to defeat the proxy before it can finish morphing into a sunken, Steamhammer will pull 4 drones and win the fight instead of 2 drones and lose. (3 drones would be ideal, if no other unit interferes.)

Recon squad

The Recon squad has been a valuable feature ever since I implemented it. But lately Steamhammer has become strong enough that Recon’s weaknesses are hurting. For example, classically the Recon squad only pays attention to units that it can see, ignoring the remembered positions of enemy units, because its purpose is to see what’s going on. But suppose the squad consists of 1 zergling and it wants to scout an area defended by a sieged tank. The ling approaches to see, gets splatted by the tank. Another ling is assigned, approaches, splatted, etc., until the target times out. The process is, as people say nowadays, unsustainable.

I made 3 changes. None is critical in itself, but together they make the Recon squad safer and more effective and count as an important improvement.

• Combat sim attends to all enemy units, as for other squads, not only visible enemy units.

• When the squad is restored after it has become empty (for any reason, not only losing all units to the enemy), reset its target to somewhere else.

• Don’t assign the squad a target that is already in view. If the Watch squad or an overlord can see the target, the Recon squad doesn’t need to. As always, if no targets need scouting, disband the squad.

Irradiated squad

I improved the behavior of irradiated units, but it still doesn’t work as intended. I’m convinced that bugs are hidden somewhere in the infrastructure code, not in the top-level decision code.

• The code was already clean, but I simplified it a little more.

• An irradiated unit keeps farther away from its friends than before. This is the most important change, even though the old distance was already outside the irradiation splash range.

• Flying units seek in a wider radius to find enemy units to splash radiation onto. Mutas are fast and may get there in time to do a little splashing.

• A slight change to burrow decisions.

Scouting

• Release the scout worker early in a few special cases: If there is an overlord nearby to continue the scouting work; if the scout runs into a completed enemy bunker or photon cannon. There are details to the conditions; for example, if no enemy unit type has been seen yet beyond those the enemy had at the start of the game, then the scout stays on the job. Steamhammer usually scouts early, and returning the scout is economically good. An enemy bunker or cannon (if not a proxy) means on the one hand that the scout cannot advance, and on the other that the enemy has no intention of attacking right away, so Steamhammer can return the scout now and wait for zerglings to arrive to keep watch.

Squad tactics

• Don’t retreat forward if the enemy is near at all. The feature was meant to fix the case where one cluster of units is attacking the enemy, while a smaller cluster farther away was afraid to approach because it could not win on its own. But if an enemy was between the two clusters, which could happen despite a triangle-inequality test to try to prevent it, the cluster retreating forward would walk through the enemy and get shredded. Instead, a Regroup cluster close to an Attack cluster is itself changed to Attack in a second pass through the cluster status decisions before they are executed. The failure cases are non-horrible, and the change fixes one of Steamhammer’s biggest tactical weaknesses. At some point I’ll rewrite it so that clusters fighting the same enemies are treated together, not separately, but that’s for the future.

• Enemy unit clustering is turned on, so that known enemy units are grouped into clusters just as Steamhammer’s units are. The config option Config::Debug::DrawClusters draws the enemy clusters in red circles to contrast with Steamhammer’s clusters in white circles. The enemy clusters are used in various decisions at the cluster and unit level.

• An unhandled case led to poor lurker retreat decisions. I rewrote the code to simplify it and fix the bug.

• When retreated all the way to the retreat point, lurkers burrow and tanks siege. Formerly, both remained ready to move, which meant that they were unready if the enemy advanced. It may not sound important, but it’s a big improvement. Indecision between advancing and retreating is common, which causes the familiar burrow/unburrow frenzy, but it’s a net gain by a wide margin.

• When retreating, count a sieged tank or a burrowed lurker as immobile defense, an option to retreat toward. Formerly, Steamhammer only looked for static defense.

• When seeking a cluster ahead to join this cluster with, use the squad’s order distance instead of the air distance. The order distance is the ground distance for ground clusters or the air distance for air clusters. This fixes some poor decisions made by ground units near terrain features.

• The code to retreat behind static defense was rewritten to be correct for a change. The actual behavior doesn’t change much, though.

• Be a little quicker to declare overlord danger at a base, so that new overlords are not spawned there to die uselessly.

Combat sim

• The configuration option Config::Debug::DrawCombatSimInfo now draws information for each cluster, rather than for the most recent cluster simulated. It shows both the raw and the smoothed attack/regroup results, so you can see how the raw results flip-flop more. Combat sim is that much more debuggable—still not very.

• A bug could leave the combat sim in an out-of-date state. Fixed. The bug (mentioned earlier in Steamhammer is progressing) is responsible for most or all of the 50-100 elo strength loss on BASIL in version 3.5.2. It’s what caused units to sit back instead of, say, attacking an undefended base.

• The radius to look for enemy units to include in the combat sim is altered to match what the Squad code does. I think this is a no-op; the enemy units that end up included are those in range to fire into the combat radius, which is different. But it looks tidy.

Micro

• Cancel a dying egg, cocoon, or unfinished building 1 second before it is predicted to die, not 5 seconds as previously. Lurker eggs were being canceled almost the moment they came under attack, which was bad. The gain of canceling items later outweighs the loss of a few units that come under sudden massive attack and die before they can be canceled.

• In figuring out which direction to kite a hydralisk, Steamhammer knows not to kite back into its own ground units—they are in the way. But it did not check whether the units were burrowed. Hydras had trouble kiting when near burrowed lurkers, because escape paths appeared to be blocked. Fixed.

Terran

• Slightly improve the stim calculation, so that marines overstim a little less. It’s a change made in passing while I was working on other stuff, under the rule “if you see it now, fix it now.” (If it were possible to follow this rule all the time, there would be no such thing as technical debt.)

Zerg

• Macro: Steamhammer did not always make enough macro hatcheries due to a bug. That hurt a lot. Fixed.

• Macro: Make no macro hatchery unless there are at least 3 drones per base. Yeesh. It sounds basic, but the drone count never entered into Steamhammer’s calculation of whether it needed a macro hatch. This is a lenient limit that prevents rare egregious blunders (which I have seen happen). I expect I’ll tighten it in the future, one way or another.

• Macro: I noticed that Steamhammer sometimes became briefly supply blocked in the early middle game. I tweaked an overlord timing parameter by 1 point of supply, which fixed it.

• Macro: Fixed a potential production freeze related to air upgrades. This is a rare freeze; I'm not sure it has ever happened. When I fixed it, I thought it was a less-rare freeze that can happen when the enemy goes mass air. Then I discovered I was wrong. I have fixed the more important freeze, but not in time to get it into this version.

• Queue sunkens ordered by the strategy boss (as well as those ordered by the static defense boss, a change made in version 3.5.2), rather than posting them directly to the building manager. I never saw the old code cause a problem, but it’s likely that the change fixes rare misbehaviors.

• Queens: Be more flexible about parasiting high-priority targets instead of waiting for a good ensnare or broodling. If there is no tank in sight and the queen suddenly notices an enemy dropship, it should know what to do. A parasited dropship cannot surprise you.

• Queens: Get ensnare much less often versus terran, and a little less often versus protoss. I find the improvement in terran play to be visible.

• Defilers: A defiler that is about to die wants to cast a last spell. It’s done in part by a hit point test. Formerly, if the HP were too low but the enemy was gone, the defiler might (say) swarm itself, then consume, then swarm again nearby because the HP were still low, etc. There was often little or no gain, and the consumed zerglings did not appreciate it. Now the defiler only casts its low-HP Hail Mary spell if the enemy is around to shoot at it. (Being irradiated, stormed, or plagued also brings a Hail Mary.)

• Lurkers: Avoid burrowing in tank or cannon range unless friends are along to help. This reduces the tendency of lurkers to rush in where angels fear to tread, though they’re still pretty foolish.

• Lurkers: Undetected lurkers look around harder for dangerous enemies nearby before unburrowing.

• Unit mix: Discourage guardians more overall. Discourage ultralisks and encourage hydralisks versus battlecruisers more. Favor hydras a little more versus wraiths. I think guardians may finally be tuned almost acceptably for Steamhammer’s current poor skill with them.

• Unit mix: When seeing 2 or more starports and no other air units, assume wraiths are likely and nudge the unit mix toward countering them. Steamhammer doesn’t make many predictions, but this one seemed important.

• Unit mix: Dark archons discourage queen production, though they don’t always eliminate it.

• I found that some urgent defensive reactions were happening too slowly. Therefore, first, call makeUrgentReaction() twice as often. Second, when making an anti-cannon sunken, it is allowed to start the creep colony before the spawning pool finishes. (Starting the creep before the prerequisite finishes for the final morph to a sunken or spore was already supported in other cases.)

• Upgrades: Better code for ground upgrades. Historically, in long games Steamhammer went for ultra-ling in all matchups, and I wrote rigid upgrade code to match. It got carapace and then melee attack upgrade, and that’s all, correct preparation for the ultra-ling unit mix, with an exception added later for ZvZ to get melee attack first. Today Steamhammer varies its unit mix more sensitively depending on the situation, and may stick with or switch to hydralisks in the late game if they’re called for. I rewrote the code to be simpler and more flexible. In the planning phase, code puts any or all of melee attack, missile attack, and carapace into priority order depending on the matchup and game situation. In the execution phase, code assigns the top priorities to available evolution chambers.

In ZvT, Steamhammer gets missile attack if it is making hydras to fight goliaths or battlecruisers, because the terran is likely to stick with them. In ZvP, Steamhammer likes hydras and usually gets missile attack first and carapace next, though it depends. In ZvZ, with less variety, upgrades are about the same as before, except that there are extra rules if hive tech is reached. To my eye, play is clearly improved, especially in ZvP. Though the behavior is a lot more complicated, the total code size is small and about the same as the old rigid code.

• Upgrades: Fixed a minor bug where Steamhammer thought it could upgrade in an uncompleted evolution chamber. The worst case result was that the bot might slightly underspend its money on this production round.

Openings

• Overgas+1 build added to use more of that fast gas. Only one new opening! Is it a record low?