AI leaves wonders unfinished with 1-2 turns left

[Oberinspektor Derrick]

Yesterday it happened to me again, and I can't see that this has been discussed a lot on the forum so I figured I'd make a thread.
The AI built a wonder, and left it unfinished at 1-2 turns until completion.
This has been annoying me for quite a bit now, and I'm pretty certain that there is something fishy going on here in the way the AI prioritizes it's production.

Here's what happened in my game:

• I had just finished my Work Ethic religion, and was thinking of grabbing any unfinished Ancient/Classical era wonders with my excess production.
• I see that Etemenanki is still available, and consider building it.
• Before starting it, I scan my neighbour (Maya) to see if they are building it - they are. And unfortunately, the animation on the wonder shows that it is only 1-2 turns away from completion.
• Because the wonder is so close to completion, I give up on it and consider invading them instead because it will be finished in a turn or two, and I want their lands anyway.
• I start building more archers, a battering ram, and beeline Iron Working for swordsmen.
• By the time my army arrives, almost 20 turns have passed and the Maya still haven't finished Etemenanki.

The scenario described above has happened to me many times now, and I don't understand it in the slightest.
In fact, I'd estimate that I notice that something similar happens in roughly a a quarter to a third of my games, and that is only in the cases where I notice that it happens (meaning it could happen more frequently).
In this case it happened in the Classical era, but two games ago it happened in the late game (Industrial era).
I have been wondering if me having an army near their borders causes the AI to start building units instead, and while I cannot rule that out, I have seen this happen in other cases as well, where I was not even remotely close to their borders.
In this particular case, the Maya switched over to building an Encampment instead, but even when that was finished they didn't resume wonder production.

So, what are your thoughts on why this happens?
Why does the AI invest so much production into a wonder, only just to stop production on it when it's just a turn or two from being completed?

 

[kaspergm]

I have seen something similar happen, but not frequently. I'm (sadly) almost positive that it is NOT your units approaching the city that causes them to not finish the wonder - in fact I have many time experienced AI building some random useless wonder while a full-scale invasion was active in their empire.

Just to rule out a marginal case, it was not a case of an extremely low-production city that had boosted it to perhaps 80 % build by chopping and then had a finishing time of > 20 turns?

My hunch is that something like natural disasters can mess with the AI and have them change their build order. Another possible scenario is a barbarian unit entering the tile and forcing them to switch production, and then the AI fails to switch production back to the wonder. In fact, the latter scenario sounds very likely in terms of how Civ6 AI acts.

 

[Oberinspektor Derrick]

Just to rule out a marginal case, it was not a case of an extremely low-production city that had boosted it to perhaps 80 % build by chopping and then had a finishing time of > 20 turns?

No, this was in fact one of their highest population cities at 8 pop, similar to their capital.
This city had already finished a campus with library, holy site with shrine, and the encampment, and surely wasn't lacking for production (it had at least two mines and a pasture as I recall as well)

Good point on the natural disasters though, I'll pay attention to that the next time.

Cannot recall if they had barbarians on the wonder tile, but I'm tempted to rule that out because I've seen this happen in the late game as well, where there were no barbarians (or hostile units) attacking the AI in question.
Cannot rule it out though, so it's a good starting hypothesis as to what on earth the AI is doing here.

 

[GalleySlave]

Just to rule out a marginal case, it was not a case of an extremely low-production city that had boosted it to perhaps 80 % build by chopping and then had a finishing time of > 20 turns?

I thought the AI doesn't do any chopping - do they in fact chop?

 

[kaspergm]

I thought the AI doesn't do any chopping - do they in fact chop?

No, I think the consensus is they don’t, but I’m not positive. But theoretically it’s was a scenario that could explain the observation.

 

[MrRadar]

AI do chop, in the meaning that they do remove features, like jungle or forests, and bonus resources, like cattle, I've seen that myself, and not once. But I do not know if they can do that strategically, that is, chopping multiple tiles to speed up a specific production, probably not, I've only noticed occasional chopping.

As for wonder building, yes, AI do show strange behaviour, including starting a wonder, leaving it halfway built, starting another wonder in the same city, and never completing it as well.

 

[iammaxhailme]

No, I think the consensus is they don’t, but I’m not positive. But theoretically it’s was a scenario that could explain the observation.

Disclaimer that this is obviously from a mod, so behavior may not be the same as vanilla, but I think they can chop. I have lost Iron from a city state in the middle of a war because they chopped it (which was enabled by a mod, but as far as I know, the mod doesn't change the AI's desire for chopping; just adds the ability to chop luxes/strats).

 

[bbbt]

Sounds like the AI potentially has no "awareness" of what it has previously built, or what even has production contributed to it? You'd think at the very least if there was no "go back to building" logic, having it just look at production to build (taking in to account what was already contributed) would alert it "hey there's this really cheap thing with a lot of value I could build).

 

[Equilin]

i think the AI doesn't realize that it built a wonder partway through.

In my head it goes like this.
1. it builds a wonder
2. it stops a wonder for something else more important (settler? units? trader?)
3. once the build cleared it no longer wants to build the wonder (or want to build it in a different city) - the full cost wonder that is. It doesn't realize that it can spend less than 20% to complete that.

 

[Disgustipated]

I thought the AI doesn't do any chopping - do they in fact chop?

I'm fairly certain they chop. But I don't think they chop in wonders.

I know my last game one of the civs I conquered was very barren in their lands. This civ was the Mongols. I mean it was barren of improvements (I'm not exactly sure why since Mongolia doesn't have a unique improvement iirc), but also woods seemed to be gone from nearly every tile in their lands. I don't think they chop stone though, Mongols did leave their stone. But they certainly chop features.

 

[Aurelesk]

When I went for a "all Wonders / No Conquest" challenge (on Prince / Standard... don't judge me!), I found out that declaring wars can change the AI behavior from building Wonders to something else (savescumming... don't judge me!). So the AI does switch production queue on event at least. Maybe there are some "events" or priority change happening?

For example, having a new slot for district, discovering a new unit (unique unit spam?), or adapting strategy (sometime I can read "Russia is not looking to win a Religious Victory anymore") could be a significant event that let the AI change its production on a spot, instead to wait to finish the current production.

My hypothesis is that once it changes Production, it doesn't get back at what the AI was building. The AI is screening all possibilities and take the most valuable, without take the Wonder being on its way to be finished. The AI started the Wonder because it has nothing left valuable to do (no Food/Population for Settlers or Districts, no tiles to improve (Builder), no building left...), but after the Production switch happened, the border/population increased so the AI have new possibilities and new priorities, therefore prioritize the districts and units, putting the Wonder at the bottom of the list.


Reading all this, I can't help myself from thinking this dumb scenario:

Brainstorming Room at Firaxis:
Executive: "Hey people! Tell me the most frustrating yet iconic event that players love to be frustrated about?"
Developer: "Being swarm by 3 Barbarian Outposts at the same time by turn 15?"
Executive: "Exactly: losing a Wonder Race by 1 turn!"
Developer: "Yes, I guess. It can happen sometimes like one game out of a few. I wouldn't say it is the most frustrating..."
Executive: "Make this event consistent in each game. Multiple time in a single game."
Developer: "You can't force an unfortunate event to be systematic. It wouldn't be random anymore..."
Executive: "Find a way!"
Developer: "I guess we could make the AI prebuild the Wonders, and when the player is about to finish it, let the AI finish it before?"
Executive: "Amazing! Implement it!"
Developer: "But that means we are crippling the AI by adding counterproductive behavior that will hurt the performance. We shouldn't add this, AI is already tricky already...
Executive: "I can't hear you, I am already gone! Implement the Wonder thing or you are fired!"
Developer: "..."

 

[Widdershins]

Not that this could explain all instances of this phenomenon, but perhaps the AI occasionally arrest work on a wonder to save era score. When I already have enough era score to ensure a golden age I sometimes delay finishing a wonder until the next era. Of course, if an AI civ never finishes a wonder, that's a wonder in itself.