AI targets enemy stacks? Or guns for cities?

[Captain]

Ok, while I've been playing the Civ series forever and am half-decent at playing the game, and even have a pretty good idea of the game mechanics, I don't really understand the AI.

So, the question is:

Does the AI try to kill your cities, or does it try to kill your units in the field? What has priority?

Is it more important for it to kill the small stack threatening a city or the big huge stack that is potentially way more dangerous?

And second question:

What should the AI be programmed to target?



---- FYI, here's the scenario that sparked the question-----

Regent, Standard, no UUs.
I'm Roman. I've killed the Germans in the 3rd war (failed in a warrior rush, and then spent my time cutting up his roads and sitting on his resources until he foolishly declared war), but during the second war, big huge Egypt declares war and starts throwing dozens of archers my way. Not hard to deflect, but had to delay my war with Germany. Then a brief lull, which I use to smash the German core, before a pile of Egyptian swordsmen shows up. I have walls in all border cities, plus took Great Wall from Berlin. So my cities are fine, but I don't want them to pillage my nice network, so I hit them back with my own swordsmen and wipe them out.

Egypt is located south of me with maybe 20 cities to my 8-10 and an army 2x as big to match. Germans to east. To get to Egypt, I have to go through Germany or a three tile thick border of jungle and mountain tiles in the west. As soon as I've dispatched Germany's core cities, I cluster my troops and head for Egypt. I've got maybe 10 swordsmen and 10 horse total. I send two of each to finish off the remaining German coastal cities (northeast).

At the same time, I've had an elite spearman and horse sitting in his territory, attempting to get close enough to cut an iron supply. But, that fails because he's got tons of roads and just as my guys get there, a bunch of swordsmen show up. My horse retreats, whew! and I am able to get a second spearman in there and reinforce on a mountain outside his borders. This is in the southeast. There are about ten Egyptian swordsmen converging on them. Yikes!

Meanwhile, I've thrown my western garrison (antioch & Cumae) at the western Egyptian city of Asyut (through the jungle) and take it. I had a big pile in Cumae where 10 Egyptian swords were coming through, but I killed half of those and the rest diverted towards Berlin. But they never showed near the city. I'm guessing they went further southeast to hit those 2 spear & 1 horse.

I've also emptied Berlin now since they're at least ten tiles away. I had it stocked with 3 spear, 4 horse, and 5 swords and those guys are marching southwest to hit Alexandria.

I take the city, and also Pi-Ramses on the west coast by Asyut. I accidently raze a tiny city (I think he pop-rushed it down to 1 and Egypt has virtually no culture). Meanwhile, his swordsmen are attacking my 2 elite spears & horse, killing off one.

So I run into his territory with horse and remaining spear, splitting directions so they follow me! Meanwhile, my now veteran and elite stacks of swords are now healed in alexandria, pi-ramses, and asyut. I'm also cranking out more swords and horse (only 3 cities doing so, Rome, Cumae, and Antioch).

I have a stack of twelve units 4 squares from Thebes (capital) but I have access to a road, so its only 2 turns to sit next to it.

Then I see a swarm of swordsmen hustling it in the west. Within my sight, I count a stack of 5, a stack of 4, 2 stacks of 3, 4 stacks of 2. That's >20 swords and they're all within 2 turns of hitting either alexandria, asyut or pi-ramses. I have 3 swords, 1 spear in pi-ram, 2 swords, 1 spear, 1 arch in Asyut, 1 spear and 1 horse in alexandria, and the stack of 12 by Alexandria/Thebes.

the funny part is, he goes for my swords in the field that are in <2 stacks. He avoids my stack of 12 like crazy. He attacks Asyut but instead of using all 4 swords sitting there, he uses only 1! So letting me counter it by bringing in reinforcements along my beautiful road network.

Then, instead of keeping his swords in a nice big 6 stack, he splits them up, making it really easy for me to run them down. I lose a few, but within four turns of this big threat, I've eradicated his threatening field armies and he's only got his garrisons left. The rest was easy consdiering I have my big stack still mostly intact.

He had a good chance at taking a city or two with those armies, but didn't. He does only partial attacks, splits his forces, and walks east past my stack of 12 instead of attacking. Seems stupid, but what is the rational for the AI doing this?

The fact is, I won that war not because I outproduced him but because the AI appears "dumb". He didn't lose a lot of men killing those 2 spear and 1 horse, but he diverted a huge army towards them that should have been able to take Berlin easily (no walls there yet). In the second case of his big swords army in the west, he didn't take a single city or attack my stack. He should have done one or the other. I used my main forces to counter wherever he sent his armies, but I used just a few small forces to distract him and capture poorly defended cities. once I realized his armies weren't threatening my cities, I pulled all the defenders to add to my front-line.

[rpodos]

My guess is that there is an algorithm that determines the strength of units on any given tile, and selects for what's "winnable."

This means giving preference to attacking the weak and disabled (nice!), then solo units, then doubles, etc.

If I'm right, this is why the AI avoids stacks.

I haven't thought through the behavior of AI stacks though, and why they would break up.

R

[The Thinker]

Originally posted by Captain
What should the AI be programmed to target?

The Ai should be programed to review on a case-by-case basis. Is the point of the war to take land and resorces or is it to teach another nation a lesson or is it just trying to defend itelf? Is it putting a small city at risk to take a slightly larger one, or are enemy forces moving in on the capital?

Rik

[Aeson]

I don't think people would like waiting hours on end for a good AI to figure out all its moves. The AI has to depend on simple rules, otherwise performance lags greatly. Once those rules are understood by the player, they can be taken advantage of. The AI "chooses" its course of action based on the players stance. This allows the player to manipulate the AI into exposing itself.

One way of making this less pronounced would be to define variable sets of rules. The AI could randomly pick between those to determine it's course of action. This would result in a less cohesive overall strategy, but less a predictable one as well.

[SpencerH]

The AI "chooses" its course of action based on the players stance.

I think that sums up how this AI functions. I think it works pretty well though and much better than any other AI in other games. My recent experience with colourless land units and the AI's "thoughtful" use of them was enlightening to say the least.

[Willem]

Originally posted by SpencerH


I think that sums up how this AI functions. I think it works pretty well though and much better than any other AI in other games. My recent experience with colourless land units and the AI's "thoughtful" use of them was enlightening to say the least.

Yes, using them certainly provides some insight into their battle plans don't they? Having a relentless stream of offensive units assaulting you gives you a much better idea of it's battle tactics.

I've dicovered something new about them BTW. As long as I keep my relations more or less peaceful with my neighbour, then there's not as much of a problem with them. They only seem to mass produce them if they're Furious with you. In my current game, I have several "outposts" right next the French, and I have only seen a couple of them so far. I tried not attacking with mine for awhile, and she did the same for the most part.

[SpencerH]

I think I can say that colourless units are the best mod I've tested and there has been many interesting permutations to their use. At one point the indians invaded my civ to take out some of these units I was builiding up on the border (that were aimed at causing nastiness fo them). It was like the AI read my mind. One that I kind of liked was being able to attack "friendly" units "passing through" my civ on their way somewhere else rather than building a wall of defending units to block their entrance or constantly harping about their removal (that inevitably starts a war). Now that the game has moved into industrial and stronger units are availble no one seems to be building medieval mercenarys any more.

I'm definitely gonna impliment stealth colourless "saboteurs" that will be available in the late industrial/early modern era in my next game. I'm sure there are a couple of appropiate unit graphics available.