3) Played with default civ2civ3 rules, this time with the AI trait expansionist_default = 500
I have tried to increase the expansionist AI trait (to 90 in 2nd savegame, to 500 in the 3th), but I do not notice any improvement.
I have found the main reason why I find the AI less challenging in v3.0: it is because their attitude towards the other players is more friendly, and it is easier to firm peace treaties with every AI, at least in my games.
Playing civ2civ3 ruleset in previous freeciv versions, there was always some AI that hated me from the start and forced me to expand while being continually attacked. In 3.0, I use to expand being at peace with everyone, I hardly need to protect my settlers and cities, I can use my units to block the AI movements, and I use to end the expansion phase with double number of cities than the AI, and it is no longer challenging from there.
When I play a game where I do not agree any cease fire, being at war against the AI from the start, then I'm forced to expand like the AI too, building many military units and few settlers. The issue I tried to point in this ticket of AI building many military units before the first settler I suppose is actually a reasonable strategy when you are continually attacked.
I'd say the problem of the AI in 3.0 is that it likes to firm peace treaties, but does not take advantage of being at peace, it seems to expand as if it was at war with the surrounding players.
The solution I have found is to edit the ruleset with a negative amount of AI love for every player, making it hard to keep peace with everyone from the start, and I finally get challenging games against the AI. I also tried to increase the AI trait "aggressive", but as my tests with "expansionist", the effect seems too subtle and I did not notice any difference.
Reply To bard
I have found the main reason why I find the AI less challenging in v3.0: it is because their attitude towards the other players is more friendly, and it is easier to firm peace treaties with every AI, at least in my games.
After some more tests watching AI debug logs, I have found the AI is more friendly when the ruleset includes the Animal kingdom (both in 2.6 and 3.0), not related to 3.0 as I said.
This is how I understand it: the code that handles the AI love for another player increases +15 per turn if they are not at war with each other, and +7,5 per turn if the other player is already at war with someone. When there is an Animal kingdom, every player is at war with him from the beginning, and everyone gets this extra +7,5 love from everyone else (even when they are not at war with each other), so it is much easier to keep peace and firm alliances. Also, since all AIs hate so much this barbarian kingdom, they chose him as preferred enemy to start a war campaign, and use to leave alone the human player.
In my tests, I need to give a negative AI love of -10 every turn to compensate the presence of the Animal Kingdom, and get similar chances of war against the player.
I'm not asking any change to freeciv code, but I found it interesting to post here to clarify my previous post. My concerns about AI issues to expand when surrounded by enemies (in my other posts) are still valid.
I have been testing the new 3.1 release and the AI no longer has this problem to expand, even with animals around. I think you can close this ticket.
The expansion of the AI in the initial stage of the game seems to be well optimized for classic and default civ2civ3 rules. I do not consider this ticket a bug.
But I have find situations where the AI struggles to expand when surrounded by many enemy players, especially with a custom ruleset that uses the Animal Kingdom.
I'll upload 3 savegames to try to show the problem, played with freeciv 3.0.7 + patch #42169 + patch #47776 (but I can recreate the problem without those patches):
1) Played with default civ2civ3 rules in a densely populated map with 40 players. In turn 30, the active aztec AI player has build 7 phalanx and 1 diplomat, the city has grown to size 5, and it has not build any settler yet.
It is a corner case, it doesn't use to happen with default rules, and it is not that bad in this situation, after all there is few room to expand and many enemy units. But even in this case, the AI does not really need 7 phalanx to protect 1 single city, when it is actually at peace (cease fire) with every nation, and everyone is still expanding.
2) Played with my custom ruleset, the same modpack from #47776, named "civ2civ3-306-freights-Modpack.zip"
It is turn 45, and the active danish AI player (cheating level) has built 8 units (warriors, phalanx and horsemen), the city has grown to size 6, and it has not build any settler yet (2 pop required in this ruleset). In this case, there is free room next to the initial city, there are no barbarian units near, and the player is not at war with anyone else, but the AI keeps building more military units instead of settlers.
With my ruleset, this problem of the AI to expand happens all the time. The gameplay in the beginning of the game is pretty similar to civ2civ3, the main difference is the presence of enemy animals (barbarian Animal Kingdom). But even when I remove the animals from the ruleset, the AI struggles to expand when there are many players close to each other, and I can no longer enjoy the earth map with 40 nations that I have been playing since freeciv 2.2, and the AI used to expand properly until now.
I open this ticket mainly to learn how to edit my ruleset to avoid this issue, that makes it hard for me to enjoy any game against the AI. But I think it is an issue that could be happening to other people working on custom rulesets and scenarios too.