The algorithm of least astonishment

[Loki]

Funny title I know, but bear with me a bit...

I'm a software consultant that specializes in mechanical engineering applications. You know 3D solid modeling, CAE FEA etc. etc. (lotsa abbreviations in this field... Don't even get me going on Bi-directional associative parametric feature based modelers!).

Anyway, in a nutshell, one of the things these programs have to do (behind the scenes transparently to the users) is to effortlessly handle some really wicked geometry problems. Imagine all the Geometry proofs + trig on steroids kind of problems.

One of the challenges the programmers of these apps face is that many geometry problems have more than one degree of freedom. This means that there is more than one correct answer. Choosing the one that is the most logical, (the one a user of the software would expect to see) is a *really* big challenge.

I know because I spent some time with the developers of one of these types of programs whilst doing some consulting. They had coined the phrase "The algorithm of least astonishment" to capture the idea of having a program pick not only one of many possible and equally correct answers, but most importantly the "most" right one. It is *not* an easy task.

OK, I told you that story, so I could tell you this one.

It's fairly early in my grand campaign (about 1120 or so) and I'm playing the Danes (You expected the Spanish with a name like Loki?!?!) I have "partnered" with my Scandinavian neighbors and have a very healthy little Baltic empire going that stretches to the south shore of the baltic around and over to Atlantic. I'm trading the CRAP out of the local resources and have some good governers collecting taxes for me. My military is plump with Huscarls of both types, and those whacky Danish war clerics. I have no military peer among my Catholic neighbors. My Dragon boats also own the baltic and the north sea. None of my Catholic neighbors have much of a navy.

Across the north sea in the british Isles The Scotts have a nice little groove going. My spies have revealed that they have the top couple of provinces of the island and their English neghbors are week and disorganized due to rebels and civil war. The French and the HRE are both excommunicated and are ripe for the picking.

So what does the Scottish AI do?

Remember the The algorithm of least astonishment?

They sail past all those prime and logical targets, and they declare war on me!

Well, we'll see what happens when scads of armored highland nobles meet scads of Huscarls. I have a feeling they'll fight hard since they fleet they sailed over on is now gone.

It was too late last night to start the slug fest, so I'll try it tonight.

But in a way I'm glad its happened. It certainly spiced things up a bit.

Have I said yet that I love this game? Warts and all.

[katank]

Umm, AI invasion is utterly whack now. Before the patch, they didn't do it at all. Now, they do it every time.

Note that you can probably ceasefire with them if you want. Often, naval invasions are the result of a rogue general. They always invade and accept a ceasefire. Weird.

[nameless]

Curious about something if the AI is doing the same thing were doing.

You know when you want an army to get from Point A to point B, let's say they have to cross 5 provinces but you know where it is so you click on B and so you get that rainbow color line running from A to B. In about 5 turns, the army will reach the target and of course engage automatically each turn.

Now, what happens if during those turns you decide to get a ceasefire? You go forth and call a ceasefire but next turn you forgot to call off the army and the army ends up breaking the treaty and calling for war.

Of course, I'm not sure how the AI mechanics work or if it's doing the same thing were doing.

Umm, AI invasion is utterly whack now. Before the patch, they didn't do it at all. Now, they do it every time.

Well the thing is is that everyone complained about the AI not doing naval invasions at all. The problem of course is that the AI needs to be reined in a little bit from going overboard.

[zandor]

Well the thing is is that everyone complained about the AI not doing naval invasions at all. The problem of course is that the AI needs to be reined in a little bit from going overboard.

It seems like the sea is one big highway to the AI, though I suspect there's some sort of range determination going on as well. I know a lot of Mediterranean factions have ships, but they've never come close in my game as England.

I think what need to be done is the AI set to attack overseas only when a piece of land close to the target is held or it's at war with the owner. Crete will be attacked if the AI holds part of Greece, Corsica & Sardinia if it holds a province in France or NW Italy. The Danes should still attack Britain of course... they were doing that well before the time MTW2 takes place. Basically just a simple mapping would do. Provinces X, Y, and Z are considered adjacent to island B, etc. for purposes of war starting.

If you're at war though everything should change. The range calculation should still be in effect, so Egypt won't invade by sea Britain unless they've expanded into the Iberian peninsula or the north coast of Europe even if they're at war.

[OMGLAZERS]

Your best bet is to head to the mod section here or at twcenter and grab an AI mod update to help improve the dumb dumb dumb AI that CA has unleashed on the world.

[Satyr]

"The algorithm of least astonishment!"

I love it! That is exactly what one should expect in a game. That is no where near what CA ever provides. It seems to me that either CA needs a better project manager/lead programmer, or better structure design in MTW. They just seem sort of overwhelmed and keep introducing the same mistakes over and over with no consideration for your rule. After playing with the patch, I am not even sure they understand how their monster works and they certainly can no longer control it. Hopefully the tools they have provided to the community to mod with are sufficient to make up for their deficits.

[Zenicetus]

"The algorithm of least astonishment!"

I love it! That is exactly what one should expect in a game. That is no where near what CA ever provides. It seems to me that either CA needs a better project manager/lead programmer, or better structure design in MTW. They just seem sort of overwhelmed and keep introducing the same mistakes over and over with no consideration for your rule. After playing with the patch, I am not even sure they understand how their monster works and they certainly can no longer control it. Hopefully the tools they have provided to the community to mod with are sufficient to make up for their deficits.

Okay, but look at what the OP said about the unexpected action of the Scottish AI:

So what does the Scottish AI do?

Remember the The algorithm of least astonishment?

They sail past all those prime and logical targets, and they declare war on me!

Well, we'll see what happens when scads of armored highland nobles meet scads of Huscarls. I have a feeling they'll fight hard since they fleet they sailed over on is now gone.

It was too late last night to start the slug fest, so I'll try it tonight.

But in a way I'm glad its happened. It certainly spiced things up a bit.

Don't underestimate the power of astonishment, people. It's what can make a game interesting and have replay value, even if we're not sure if the wackiness is due to actual bugs, or just random factors.

Do we want the conquest of the map by the AI factions to follow a script that plays out exactly the same way each time? Or do we want different, "emergent" outcomes every time we play a new campaign?

Speaking for myself, I don't want to see absolute craziness, but I also don't want a predictable game where I can safely assume that Faction A will always do this, and Faction B will always do that. It's a question of balance, and maybe some "odd" or even buggy decisions by the AI are necessary to keep things unpredictable and challenging.

[katank]

Well, I agree there should be variety. The thing is that there should be some rhyme or reason to their invasion and not just variety for sake of variety. Random attacks that leave their homebase undefended and not taking easier pickings closer to home is silly.

Getting 90% of their armed forces sunk due to putting everything into one ship is beyond dumb. In my Russian game, the Danes didn't take Hamburg but instead sailed for Bruges. A castle closer to home would have served their interest far better. Then again, I decided to go crazy navally as well myself that game and promptly took over Arhus and destroyed Scotland in the first 15 or so turns.

[ElectricEel]

I have read in the discussions about the AI files that the AI is apparently hardcoded to attack the player if the player is at peace for too long, without regard for the current in-game situation. The lenght of time depends on the campaign difficulty level - if I remember correctly, 4 turns at Very Hard, 20 turns at Easy.

[mrbrownstain]

I play the danish. (that sounds funny) Same thing happened in my game. I'm sure the invasions are scripted or at least factions invade specific territories in a specific order.

Often I'm allied with a faction and on amiable terms when they decide to attack me.

Back to those belligerent Scotts. I was allied to them and feeding them cash every turn by the thousands in order to create turmoil in England. I was also strong in the North of Europe with any number of easy targets as neighbors. They had three territories on the island and had the military to take the island. They landed north of Brughes and wait for a few turns. I thought "Good luck lads, Caen is that way. Here's military access." They finally attacked my city of Brughes with too little force to even garrison if they succeeded at taking it.

So these guys deserve to die. I'll chop their arms off and toss them in the North Sea for christianity!

[katank]

As you can see in the previous example, they are doing algorithm of most astonishment not out of variety or valid strategy but sheer stupidity. To land two units next to a well garrisoned city and siege it or to send a lone ship to blockade a desolate port is not at all a viable way of warfare.

[Shahed]

Specially when there is ABSOLUTELY no viable follow up strategy whatsoever.

[Quillan]

Tell me about it. I wouldn't mind the AI doing some unpredictable things, but I'd like some design in it. For example, first it decides who to war against. That might be an unpredictable target. Once it's chosen the target, then do a military comparison. Don't have what they need to gain the upper hand? Well, before attacking, build up scads of troops. Then, muster those troops together. Only when they have 2-3 armies gathered should they attack. If they're coming by sea, they should come in force, not these little random drive-by blockades and weak invasions. I had Spain drop a single pavise crossbow unit on Corsica earlier. It didn't even siege (not suprising as I had a 16 unit garrison of militia there in that huge city), but it doesn't take much either for me to take a unit of cav militia and go run them down. It lost a unit and a 3 ship fleet for nothing.

[dopp]

Tell me about it. I wouldn't mind the AI doing some unpredictable things, but I'd like some design in it. For example, first it decides who to war against. That might be an unpredictable target. Once it's chosen the target, then do a military comparison. Don't have what they need to gain the upper hand? Well, before attacking, build up scads of troops. Then, muster those troops together. Only when they have 2-3 armies gathered should they attack. If they're coming by sea, they should come in force, not these little random drive-by blockades and weak invasions. I had Spain drop a single pavise crossbow unit on Corsica earlier. It didn't even siege (not suprising as I had a 16 unit garrison of militia there in that huge city), but it doesn't take much either for me to take a unit of cav militia and go run them down. It lost a unit and a 3 ship fleet for nothing.

Those random, really weak attacks are actually raids. There is this "raid" setting in the AI file that causes it to send tiny armies just to irritate you if it is too weak to mount a proper invasion. Check your alliances; you may be in a group that is opposed to the raiding faction, hence it is searching for an opportunity to aid its fellows against you. With the post-patch tweak that makes the AI consider itself adjacent to any of your coastal provinces, it is no wonder that you get random morons sailing halfway across the world just to land raiding parties at your doorstep. I think even a 1-turn siege of any settlement cuts off trade for that turn, so they are achieving something even if the very garrison they are besieging sallies forth next turn and obliterates them.

[katank]

Hey, that actually makes a bit of sense. The thing is, I'm seeing very high raid to invasion ratios. Also, the amount they gain from the raids probably don't justify the costs (their force lost+fleet). Even if they manage to choke off income for 1 turn, that's maybe 700 florins down the drain for me. Just losing a few crappy units + 1/2 ships probably costs the AI in the ball park of 1500-2000 florins.

They ain't even winning the economic game. It'd be actually funny (perhaps even viable) if they do this with many peasants (at every city) in concert constantly to try to destroy my income.

[dopp]

Hey, that actually makes a bit of sense. The thing is, I'm seeing very high raid to invasion ratios. Also, the amount they gain from the raids probably don't justify the costs (their force lost+fleet). Even if they manage to choke off income for 1 turn, that's maybe 700 florins down the drain for me. Just losing a few crappy units + 1/2 ships probably costs the AI in the ball park of 1500-2000 florins.

They ain't even winning the economic game. It'd be actually funny (perhaps even viable) if they do this with many peasants (at every city) in concert constantly to try to destroy my income.

The more powerful you are, the more likely they'll send raids (including the infamous 1-turn blockades). Yup, it's a FEATURE, not a BUG. Also, the less soldiers you have actually camping your mutual border (don't ask me how you camp the sea), the more likely you'll see raids. In theory, it forces you to maintain troops to guard the frontiers. In practice, you'd be better off using those troops to kill off the offending neighbor for good. No neighbor, no border, no problem.

[antisocialmunky]

I wonder if there's anyone willing to play a game without taking or permanantly holding any coastal provinces at all? That'd definately be and interesting way of seeing what the AI does then.

[Satyr]

I wonder if there's anyone willing to play a game without taking or permanantly holding any coastal provinces at all? That'd definately be and interesting way of seeing what the AI does then.

It wouldn't make much difference. While you wouldn't be getting raided in such silly ways, the AI does the same things to each other too. And any faction that does border you is going to be just as idiotic.

[Von Nanega]

I like the replay value inherent in the strange invasions. I am currently playing as the Danes also. I married off two princesses to the Polish and they have not attacked me. (Turn 100 now) This game is the second one of the Danes I am playing to test Replayability. The first game I married off two of those princesses to the Poles but they declared Total War on me. I pretty much scripted the first twenty turns for myself as close as possible. Two different experiences.

[Kobal2fr]

I have read in the discussions about the AI files that the AI is apparently hardcoded to attack the player if the player is at peace for too long, without regard for the current in-game situation. The lenght of time depends on the campaign difficulty level - if I remember correctly, 4 turns at Very Hard, 20 turns at Easy.

That's not true. The only thing there is is a comment (to non code savvy folk out there, that means a bit of code that is not processed, where the codewriter says what he wants his code to do or explains why it works) saying "special case exists here in code for forcing aggression on player if at peace with everyone for N turns", but that's it, there's no actual code for this. Just the comment to tell people "if you want to do this, here is where you'd put the relevant code".

As to the rest...

Dopp is (as always, it seems :) ) right in saying the apparently weak invasions are actually raids, disruption fodder sent because said faction is too weak to do anything else, but not wanting to bend over either. As katank points out, it's counterproductive through naval invasions most of the time, since ships are costly, but on land it works just fine. If it irritates you, the player, and cuts off one city for even one turn (or cuts trade between cities and forces you to sally to crush them) then mission accomplished .

But naval invasions do bork the AI a lot, and the worst thing is that whatever CA did to enable them, it's hardcoded and we can't touch it, neither to make them go away or just to tweak them into working more sensibly :/

[dopp]

But naval invasions do bork the AI a lot, and the worst thing is that whatever CA did to enable them, it's hardcoded and we can't touch it, neither to make them go away or just to tweak them into working more sensibly :/

You might try adding "force_invasion = false" to everything for your diplomacy mod, Kobal2fr. That may effectively neuter the naval invasions as they seem to be classified as "forced" (ie hardcoded) invasions.

[Vladimir]

Dopp is (as always, it seems :) ) right in saying the apparently weak invasions are actually raids, disruption fodder sent because said faction is too weak to do anything else, but not wanting to bend over either. As katank points out, it's counterproductive through naval invasions most of the time, since ships are costly, but on land it works just fine. If it irritates you, the player, and cuts off one city for even one turn (or cuts trade between cities and forces you to sally to crush them) then mission accomplished .

I can't see any reason why someone would send a unit of pavaise crossbowmen on a raid. That's the absolute worst unit to send on a raid; especially since in that example the raider was Spain and they have Jinettes! Personally I’m all about the raid, I love sending a 5 unit raiding party of mounted X-bows (in M:TW) against someone if I’m just trying to soften them up. I just don’t understand why the (incredibly) AI would send a slow ranged unit on a raid. Raids require speed!

[Kobal2fr]

@dopp : nah, that would stop the AI from invading, ever. cannot_force_invade is the "sit down, shut up, read a book or sumtink" AI function :)
Right now I've merely disabled all raids except when the factions are already at war (I figure a weak faction wouldn't want to draw too much attention anyway), and removed the "don't care for factions we don't share a border with, want peace" factor since it is obvious now that they *do* care, even though I don't understand how and why :)
But first the antitrait thingamajig, then X-mas derailed my tests, and now my comp itself is acting up (fan problems, overheating, BSOD's, the works...). Patience :)

@Vladimir : sure, but Jinettes cost a mint to produce and upkeep, while x-bows are cheap.
Anyway, I do agree with you, but that's not something I can mod directly, what the AI does with a given order is all hardcoded as far as I know, we can just fiddle with the orders themselves, and the descr_strat army preferences :/
And in any case, unless you really know what you're doing, sending a weak force against a big stack will not result in a weaker big stack, but only a dead weak force. The more lopsided the odds, the less losses for the big guy, unless you're all about HAs. Thus, given that the AI cannot handle raids properly (I can't tell it to only use HAs or skirmishers for raids, it just uses troop cost from what I can see. The AI seems to assume a 300 florins unit will beat a 200 florins one, period), I think it's better to do away with them alltogether...

[Shahed]

It would be great to see faction specific raiding mechanics for the AI. For obvious example the Mongols raiding their borders incessantly. Akinci corps raiding enemy borders for Turks.

[Kobal2fr]

Hmmm, while I can't tell them "use such and such units", I *can* let some factions raid and others not. This is a very good idea you have Sinan : Turks, Rus, Hungarians, Mongols, all have low-value HAs that they can build easy and en-masse and would probably use with a raid order. I'll keep this in mind.

The other problem there would still be with raids of all kinds is that 1) against another AI, the battle will be autocalc'd : full HA army advantage is completely lost, and 2) against a human, the AI "forgets" the raiding intention on the battlefield : even with a small, all HA force, the AI will play to the death, not just empty quivers and run away.
TBH, it can probably be coded to do so in the battle strat xml, but that file is hairy to say the least and I haven't tried to figure it out yet.

I wonder, did the big mods like Europa Barbaorum, Rome Total Realism etc... feature improved AIs ? Because if that's the case, it might be simpler/faster to just borrow their ideas and work on an already improved basis.

[ElectricEel]

That's not true. The only thing there is is a comment (to non code savvy folk out there, that means a bit of code that is not processed, where the codewriter says what he wants his code to do or explains why it works) saying "special case exists here in code for forcing aggression on player if at peace with everyone for N turns", but that's it, there's no actual code for this. Just the comment to tell people "if you want to do this, here is where you'd put the relevant code".

Oh? I understood the comment to mean 'for the information of those modding this file, the code that handles AI logic does this', rather than how you interpret it. But you probably have followed the AI modding discussion more closely than I.

[ElectricEel]

I wonder, did the big mods like Europa Barbaorum, Rome Total Realism etc... feature improved AIs ? Because if that's the case, it might be simpler/faster to just borrow their ideas and work on an already improved basis.

The AI logic itself was not modifiable in RTW, though some improvement was possible by modifying the formation files and changing the game enviroment to better suit the AI.

[Kobal2fr]

Could be either all other things being equal, but in the "mapping of old Rome params" at the end of the file, which is the template for the new AI, there are also a bunch of these "SPECIAL CASE EXISTS HERE IN CODE FOR SUCH AND SUCH" comments. There's one in the beginning in particular, saying "special case here for not allowing attack of trusted allies". In the code used by the game, the comment does not appear, and in it's place ... is a condition (not appearing in the old code) forcing the AI not to attack its trusted allies.

Which is what leads me to believe that all those special cases comments are just that : a "blueprint" for what could/should be done and where to put it so that it works, and not an explanation of what happens elsewhere (after all, I'd assume CA people working on the files would already know, or would easily find out what happens elsewhere, even though my work on the traits left me with some doubts regarding this :) ).