Poor AI targeting priorities

[xeren]

So in our current game, 3 players vs difficulty 7 Peacemaker and Bully, we probably _should_ be dead at about the 10 hour mark.

We got hit by a 4000 strong cross planet attack of tech 2 ships, and they quickly wiped out my homeworld, and about 1400 ships began to rampage.

But then a strange thing happened - about 400 got stuck in one system, and about 1000 go stuck in another.

We go look, and both are busily trying to destroy Core Warhead Interceptors in each system... which have 150M HP.

We regrouped our shattered fleets, sent them in, and wiped out every ship without taking any casualties, because the AI was obsessed with destroying these (useless) structures.

This isn't the first time we've seen this behavior, during normal raids, they'd often get obsessed with targeting those, but during other games/in other systems, we've also seen the AI prioritize really useless planetary specials, over raiding more useful targets.

[keith.lamothe]

Hmm, I think I know why.  They do have the "VeryLowPriorityTarget" flag which should lead to the behavior you would expect, but they also have the "AIIsIrreplaceable" flag which triggers a whole other set of preferences which could well lead to the behavior you have observed.  Strictly speaking the interceptor is irreplaceable, but since it's useless to the human I'll try removing that flag for 3.083.

[keith.lamothe]

Actually, Chris, do you know of a reason to have Warhead Interceptors not auto-die with the command station, just like the warp gates?

[x4000]

Yeah, I think the first is a good call.  I would suggest making the warhead interceptors remain belonging to the AI, not being capturable on planet ownership change, though.  Basically, the reasons for them not to auto die are twofold: first, I think that causes a minor bit of AI progress; and second, if that is left alone on a planet, it can still destroy warheads coming through just fine, which I think is a mildly interesting strategic thing.

[xeren]

To be clear, the Core Warhead Interceptor isn't the only special I've seen this behavior, it's just the most notable because it has so many HP (and so many of the AIs regular waves would get completely distracted by it)

Unfortunately I don't recall which other items the AI would get hung up on regularly. In general, the AI going after relatively tough specials with non-bomber ships seems like a bad idea, it'd be better served just raiding resources and then planet hopping when there's no easy pickings left.

[x4000]

Generally speaking, if it can kill something that is a permanent loss to you, that is the only way to permanently hurt you.  To replace whatever it is you have to go take another planet and incur more AI Progress cost, and otherwise you just have to do without that thing.  The motivation for the AI is to hurt you in ways that can't be repaired between waves.

[xeren]

Oh I think that's a good general strategy - it's just not good when it consistently sends waves that *can't* damage/destroy the special fast enough to do anything. So instead of destroying resources and delaying our fleet rebuilds at least slightly, it throws away a wave trying to destroy a target that it's ships simply aren't suited to

Now, I've seen it use forcefield ignoring ships to destroy stuff under the orbital command FF, which is funny, annoying, and effective, but I've also seen it get hung up on a planetary special and constantly send the waves that go into that system to attack the special, even though it failed miserably the last 5 times (I'm assuming there's no memory of success/failure, only target priority)

[x4000]

I gotcha.  Yeah, it uses some logic to determine if it can destroy a forcefield with the number of bombers (or whatever) it currently has with it.  Probably needs some logic relating to those other structures along those same lines.  Keith, I don't think you've done anything with the AI yet -- could be an interesting first foray into that area.

[keith.lamothe]

I was just thinking that the "kill the irreplaceable!" code could be made conditional on "can I even scratch the paint on that behemoth?".

[x4000]

Great!