Poor water-related AI actions

[Kzer-Za]

I was playing an archipelago map and noticed that AI players are not sending any units outside of their islands. I am already pretty far into the game (started researching Combustion), so I suppose AI players should have Compass, which would allow them to embark, but none of the 8 AI players (it's a huge map) has left their islands. Come to think of it, I have not seen a single naval unit of theirs, even though I have been encountering Barb galleys for a long time. I have not seen even their Workboats.

Maybe it's an issue of the base game, I have not tried it with Civ V ruleset because checking it is gonna take some time. But having played previously a map with several continents with Civ V ruleset I seem to remember that my continent was visited by several embarked military units from another continent.

Also, I do not see any of the fish/crab/pearl tiles within AI civs' culture borders to be improved. I have even loaded 2 previous saves from 2 different playthroughs with Civ IV ruleset; in these saves I already have Satellites, so I can see the whole map. I have not paid any attention to it during those playthroughs, but now checked carefully all their coasts, and all their fish/crab/pearl tiles are unimproved.

[RobLoach]

AI players are not sending any units outside of their islands

That's definitely a weird one. Think it could be that they don't know they could build a ship? Many of the units require either one or another unit type...

"Unavailable <without [Copper]> <without [Iron]>",

Maybe the AI doesn't quite understand that it can build it when they have copper, but no iron?

though I have been encountering Barb

Speaking of which, a few of the units have "Never appears as a Barbarian unit" that we may want to remove. Which units do you think should appear as barbs?

https://github.com/yairm210/Civ-IV/blob/master/jsons/Units.json

Also, I do not see any of the fish/crab/pearl tiles within AI civs' culture borders to be improved

There is a flag "Guaranteed with Strategic Balance resource option", think we should add that to some of the sea-tiles?

[Kzer-Za]

Maybe the AI doesn't quite understand that it can build it when they have copper, but no iron?

I have the impression that the AI civs not only do not build naval units, but do not embark land units. Though in one of those saves where I have researched Satellites I can see that one of their civs have improved tiles on a small island; that island does not have a city but it is within culture borders of a continental city; so a Worker must have been embarked and sent there. But apart from that I do not see any evidence that they ever embark their units. Maybe they do not have Compass researched? But that would be strange considering that I am playing on Prince and already several turns into Modern era.

I do remember being visited by several embarked units in one campaign with Civ V ruleset. I don't know, does Civ IV ruleset have any changes that actually affect AI behavior?

Their civs do not even use workboats for scouting, and workboats do not require any resources to be built. Although I don't know if AIs use them for scouting with Civ V ruleset, haven't paid any attention to it while playing with Civ V ruleset.

Speaking of which, a few of the units have "Never appears as a Barbarian unit" that we may want to remove. Which units do you think should appear as barbs?

As far as I know, in Civ IV any unit could appear as a barb unit? Then probably, remove it from all the units except those that are unique (Keshiks, Jaguar Warriors, etc)?

There is a flag "Guaranteed with Strategic Balance resource option", think we should add that to some of the sea-tiles?

What I meant was that I don't see those tiles improved by workboats within their borders: there are those resouces within their borders, but those tiles are not improved, so I mentioned it as another evidence that the AI does not properly handle water. Does it actually know how to build workboats and use them? I have not paid attention to it when playing with Civ V ruleset, and now it's gonna be some time before I get around to checking it.

[yairm210]

AI definitely builds work boats in Civ V ruleset

[Kzer-Za]

I noticed something else: in Civ V ruleset not only other civilizations properly use water-related actions, but even Barbarians starting from some moment (which moment it is I am not sure, maybe when the first actual civilization is able to embark?) start embarking their land units. With Civ IV ruleset barbs are only able to build galleys (if their camp is on a shore), but they never embark their land units.

[RobLoach]

Thank you for debugging here. I am unclear what the differences are here. Take Caravel, for instance...

Civ V

https://civilization.fandom.com/wiki/Caravel_(Civ5)

{
  "name": "Caravel",
  "unitType": "Melee Water",
  "movement": 4,
  "strength": 20,
  "cost": 120,
  "requiredTech": "Astronomy",
  "upgradesTo": "Ironclad",
  "obsoleteTech": "Combustion",
  "uniques": ["[+1] Sight", "Withdraws before melee combat <with [80]% chance>"],
  "hurryCostModifier": 30,
  "attackSound": "cannon"
},

Civ IV

https://civilization.fandom.com/wiki/Caravel_(Civ4)

{
  "name": "Caravel",
  "unitType": "Melee Water",
  "strength": 3,
  "movement": 3,
  "cost": 60,
  "requiredTech": "Optics",
  "uniques": [
    "Can upgrade to [Frigate]",
    "Can upgrade to [Submarine]",
    "Can carry [1] [Scout] units",
    "May enter foreign tiles without open borders"
  ],
  "attackSound": "shipguns"
},

[yairm210]

Only air units can be "carried" in current implementation