Border Growth Priority

Are these rules for priority not correct?

http://civilization.wikia.com/wiki/City_(Civ5)#border_expansion

The AI basically always ignores the tiles I want and it should be picking, like in this screenshot:

My guess it that you don't have iron working yet, so the gems are inaccessible?

Not clear why the empty sea rather than the fish, maybe it prefers closer tiles over more distant tiles and the fish aren't special enough to trigger a tile 3 pick?

I'm definitely in the Renaissance Era; not having Iron Working isn't an issue.

My thoughts were that the Civ V Wiki has it wrong and the city will always fill out any given ring before moving to the next. For it to pick the coastal and not the river tiles could indicate Oil?

I don’t think the wiki article is wrong so much as overly optimistic. Check out the cost to buy the fish tile. Is it more expensive than the two closer empty coastal tiles?

I don’t think you should hope for oil, and the governor will definitely not always fill out any given ring before moving to the next. I wish it were either more logical or at least more consistent!

As far as the gems go, you can make tiles more likely to picked by the governor by clearing forest or jungle.

Also, FWIW, I would have settled 1 hex NE. Mostly because of one exposed hex to ocean instead of three. You would have gotten the first fish a little later, but the second one much sooner. Other specials are the same distance, and less useless coastal and ocean hexes to distract the governor.

This looks normal to me.

However, I note that cash buying tiles with a resource such as the Gems you mentioned and also the other Fish would be extremely cheap. (There is a major cash discount in BNW for buying tiles with a visible resource)

Yes, resource tiles are usually cheap to buy, although the governor might not prioritize them at all. Also many natural wonders counts as mountains, so the governor also don't like them, but they're expensive to buy.

The governor uses the same basic algorithm as the rest of the AI


More seriously, in my experience the gov often takes food bonus resources first (even when 4th ring ) then strategic resources (even if you are currently unhappy ) then luxuries but it will sometimes acquire cheap tiles (flat tiles are cheaper and i think ocean counts as flat) closer to the city before going to far away resources (seemingly at random). As has been said, forests and jungles lower priority so removing the jungle from some resource will make it more attractive for the gov.

I guess someone with access to the source code could tell us if it's purely weight based or there is some random roll but given how the AI tend to work, i would guess some RNG is involved.

EDIT : must add that the wiki is badly outdated as it still lists great artists "culture bomb" ability. it's been a long time since this ability was given to the great general's citadel.

Wiki is probably wrong. The Tile acquisition is actually extremely simple. If it's a flat resource, it'll grab that first (something like river wheat.) Then it will move on to flat empty tiles, then it will grab hills, then it will grab forested/jungle, then forest/jungle hills.

If you want any of those other tiles, simply chop the forest and you'll see the priority move. It doesn't fill one ring before moving on to the next, but it absolutely won't grab a 3rd ring forested/jungle hill before a 2nd ring flat area (the ocean, in this case). As for the fish, I've seen it both ways, and I should also note that just because it has the tile highlighted doesn't mean it's for certain going to expand to one of those slots.

Bob Morane said:

I guess someone with access to the source code could tell us if it's purely weight based or there is some random roll but given how the AI tend to work, i would guess some RNG is involved.

EDIT : must add that the wiki is badly outdated as it still lists great artists "culture bomb" ability. it's been a long time since this ability was given to the great general's citadel.

Click to expand...

The folks in Creation & Customization are the ones most likely to know the source code.

For those that ONLY have Vanilla, and not G&K / BNW, that part of the wiki is still correct. It was in G&K that culture bomb shifted from Artists to Generals.

Chum said:

Wiki is probably wrong. The Tile acquisition is actually extremely simple. If it's a flat resource, it'll grab that first (something like river wheat.) Then it will move on to flat empty tiles, then it will grab hills, then it will grab forested/jungle, then forest/jungle hills.

If you want any of those other tiles, simply chop the forest and you'll see the priority move. It doesn't fill one ring before moving on to the next, but it absolutely won't grab a 3rd ring forested/jungle hill before a 2nd ring flat area (the ocean, in this case). As for the fish, I've seen it both ways, and I should also note that just because it has the tile highlighted doesn't mean it's for certain going to expand to one of those slots.

Click to expand...

There were minor tweaks made to this in BNW, the wiki is right for those with Vanilla, but a bit wrong for those with expansions.

I do note though that sometimes chopping forest on hills doesn't seem to change cultural priority, the hill itself is tough terrain. And in case of a resource present, you are definitely better off paying the cash than chopping forest and waiting because of the cash discount for buying.

Bob Morane said:

I guess someone with access to the source code could tell us if it's purely weight based or there is some random roll but given how the AI tend to work, i would guess some RNG is involved.

Click to expand...

It's only slightly RNG based.

Every available plot is given a weight (search for INFLUENCE in GlobalDefines.xml - ignore the ones relating to spies!) - despite cost being in multiples of 5, influence/weight can (and does) differ by 1

The RNG is only used to pick one plot if multiple plots have the same weight.

The oddity between cost (multiple of 5) and weight (multiple of 1) is why on the city screen you can get several plots showing that they could be acquired next, and then the governor picks a "dumb" one - eg sea - as that tile will have a slightly lower weight than another highlighted one.

(The code is in CvCity::GetBuyablePlotList(), and is over 200 lines, so not too easy to summarise.)

Somewhat tangentially, and I have only done this a few times, but when I play the same map with Liberty + Tradition Opener versus Tradition, border growth in the Tradition game is noticeably better. Is that just because I have fewer cities? Or does Tradition have some other perk for borders beyond the opener?

whoward69 said:

The oddity between cost (multiple of 5) and weight (multiple of 1) is why on the city screen you can get several plots showing that they could be acquired next, and then the governor picks a "dumb" one - eg sea - as that tile will have a slightly lower weight than another highlighted one.

Click to expand...

Thanks for clearing this up. Also, thank you for Pick-n-mix!

Chum said:

I should also note that just because it has the tile highlighted doesn't mean it's for certain going to expand to one of those slots.

Click to expand...

Is Chum mistaken about this, or does it happen? I don't think I have seen it, but I don’t watch that closely, since it is so painful to wait on the governor to pick up the tiles I want.

beetle said:

or does it happen?

Click to expand...

It can happen, but there always underlying reasons. Eg, you have two overlapping cities and they both expand the same turn (or within the turns that you look)

Cities A and B share a tile in (say) the second ring of A and the third ring of B. This tile is adjacent to a luxury resource in the fourth ring of B.

City B will be showing three or four tiles to expand to, none of them the lux in ring 4.

City A expands and takes the shared tile. The weight given to the lux in ring 4 now decreases significantly (low is good) and can fall to such a point that it will now be chosen over the previously highlighted ones.

beetle said:

... so painful to wait on the governor to pick up the tiles I want

Click to expand...

Exactly why one of my first DLL based mods was "UI - City Expansion" - pick the one you want, or get a discount on it if it's not one the governor thinks you should have!

beetle said:

Somewhat tangentially, and I have only done this a few times, but when I play the same map with Liberty + Tradition Opener versus Tradition, border growth in the Tradition game is noticeably better. Is that just because I have fewer cities? Or does Tradition have some other perk for borders beyond the opener?

Click to expand...

There is no other Tradition bonus for border growth, besides the opener, but border growth is a function of culture generated in the specific city. The opener's +3 culture in the capital (together with your palace's culture) certainly provides a bigger bonus than the +1 culture from the Liberty opener. And the free culture buildings from Legalism certainly can help on that front (in your first four cities), particularly if you don't prioritize building monuments in your Liberty cities (there's so much to build in expos -- you may be prioritizing libraries, granaries, workers, archers, etc., which can make sense, but does result in delayed culture in your expos).

To be clear, Beetle -- the border growth from Tradition is for ALL cities. It's just the capital that gets +3 culture specifically.

Browd said:

And the free culture buildings from Legalism certainly can help on that front (in your first four cities), particularly if you don't prioritize building monuments in your Liberty cities

Click to expand...

Monuments are pretty high in Liberty build queue -- unless I am near unlock the first policy in Aesthetics (which makes the culture buildings cheaper), but still monuments would be still be later, and the amphitheater (in cap) much later. Also, Tradition opener for me is after three picks in Liberty. So I think the difference I see is, as you point out, explained sufficiently by the delay.