AI behaviour Obvservations

[stavrosfa]

There are many things that I have taken note of regarding AI behaviour, and I wanted to have a central place that we can reference.
These are not necessarily bugs, just things we should make better. I don't want to address things that are not implemented at all, for example, why not settle islands using boats? Because this is more of a feature than tuning.

Feel free to add what ever you think fits in here.

Settlers

1. Building very close to other cities borders.

2. Building cities inside other civ's borders (I think regardless of their relationship status with this civ). I had seen this before, if the a settler finds a "gap" big enough (BFC + 1) it will build there

3. Sometimes settler will go very far and plant a random city while the surrounding area is relatively scarcely populated, that doesn't even have a resource.
4. Cities will not produce settlers even if there is a huge empty space right next to where they are. This probably happens after the civ reaches the "optimalNumberOfCities"

Workers

1. Workers will often gather in one tile, in masses, to build an improvement that requires less workers than what they end up being. This often leads to building 2 improvements in 1 turn, as one set of workers override what the other set did (it's ussually mines vs irrigation)
2. On the note of mines and irrigation, if any amount of workers find themselves on a desert tile, they will probably get stuck there forever, building a mine, then after finishing that, override it with an irrigation, in an endless vicious circle.
   Even if they have tiles left that have unconnected resources, or need a road, or even railroad, they won't move at all from that tile, endlessly working it.

3. They will often choose to chop trees/jungle, before there are roads on the tile and before there is a stable network roads, to justify taking the time to do it.
4. Perhaps I am wrong on this, or at least slightly off, but I don't think that they take into account what's been produced on the city, chopping trees when there is a warrior to be built in 1-2 turns, in a city that produces 2-3 shields.
5. They will sometimes start building roads on enemy territory, but I haven't studied it thoroughly, they might be trying to connect 2 tiles that belong to their civ.
6. They will also sometimes build road, on unowned tiles, trying to connect a road from nowhere to their border tiles, 10 tiles away.

Unit Production and General Unit Behaviour

1. Cities will often overproduce, especially when at war.
2. But they will produce for example 150 Infantry units over the support limit, but they won't send them to fight, they will just stay to protect the city.
3. At the same time, they won't produce a single attack unit to fight back.
   This doesn't happen in all ages, for example I guess that the Infantry is stronger than the Cavalry, so that's why this happens in the industrial era. In the middle ages, they will produce more Knights than Pikemen for example.
4. The wealth production should also be tweaked, now it's at a level where it almost never gets picked by the AI, most likely contributing to the above overproduction, which halts research too. Reasearch is also affected by how we handle going below 0 in our treasury.
5. Especially in the early game, pretty much ALL (combat) units will explore regardless of borders