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Stellaris Dev Diary #24 - AI

Hello everyone and welcome to yet another development diary for Stellaris! Today, I'll be talking about AI, and not of the robotic kind. I'm talking of course, of the game AI, which is currently being developed by myself and @merni who is the dedicated Stellaris AI programmer, while I'm just temporarily on the project to flesh out certain aspects of the AI before launch.

Artificial Personalities
A major challenge when making the Stellaris AI has been the randomized nature of the game. With thousands of different combinations of ethoses and traits, there's a risk that every AI Empire ends up feeling the same to the player, or fall into a very basic categorization of 'aggressive aliens' and 'peaceful aliens'. I as the AI programmer might know that an AI with Fanatic Collectivism makes their decisions differently from with plain old vanilla Collectivism, but it might all look the same to a player who doesn't have this foreknowledge.

In order to address this problem, we've implemented a system of AI Personalities that govern almost every aspect of how they behave, such as who they'll pick a fight with, which trade deals they are interested in and how they budget and utilize the resources available to them. This personality is determined by their ethos, government form and traits, and will be shown to the player when diplomatically interacting with that Empire. To feel recognizeable to the player, all of the personalities are rooted in sci-fi tropes, so that you'll immediately know who the Klingons are to your United Federation of Planets.
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Personalities naturally have a bigger impact on diplomacy than anything else - if your goal is to form a Federation, it'll be much easier to do so with an Empire of Federation Builders than a bunch of Ruthless Capitalists, and forget getting Xenophobic Isolationists to agree to any such proposal unless they have a very pressing reason. You can tell how an Empire feels about you from their Attitude, which is primarily driven by opinion, and affects factors such as what diplomatic offers they'll consider and how fair a shake they will give you in trade deals.
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In addition to the regular personalities, there is also a special set of personalities for Fallen Empires. Instead of the usual mix of Ethoses, each Fallen Empire has only a single Fanatic Ethos - the single remaining ideal they hold to after centuries of seeing what the galaxy has to offer. This Ethos determines their personality, which in turn affects how they view your actions. For example, a Xenophobic Fallen Empire will want nothing to do with you or anyone else and will be very upset if you start encroaching on their borders, while a Spiritualist Fallen Empire will consider themselves the protectors of the galaxy's holy sites, and will not look kindly on your colonists trampling all over their sacred planets. If you think angering a Fallen Empire is harmless because they won't conquer you - think again. Fallen Empires get a special wargoal to force you to abandon planets, and will be more than happy to cut your upstart species down to size if you don't show sufficient respect for your elders.
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Threats and Rivals
So what then, is a pressing reason for an AI to go against their personality? Well, one such reason is Threat. Threat is a mechanic somewhat similar to Aggressive Expansion in Europa Universalis 4. Conquering planets, subjugating other Empires and destroying space installations will generate Threat towards other Empires. The amount of Threat generated depends both on how far away the Empire is from what's happening and on their Personality. Xenophobic Isolationists won't care if you're purging aliens half a galaxy away, but if all the planets around them being swallowed up by an expanionistic Empire, they'll definitely take note. Empires that are threatened by the same aggressor will get an opinion boost towards each other, and will be more likely to join in Alliances and Federations - if you go on a rampage, you may find the rest of the Galaxy uniting to take you down, and while Threat decays naturally over time, there's no guarantee that the alliances formed by your imperialism will break up even if you take a timeout from conquering... so expand with care.

Another feature borrowed from EU4 to drive AI behaviour is Rivals. Any independent Empire that are you not allied to can be declared a Rival, up to a maximum of 3 Rivals at the same time. Having an Empire as a Rival will give you a monthly increase of Influence, with the amount gained based on how powerful they are relative to yourself - having a far weaker Empire as your antagonist will not overly impress your population. It is further modified by Ethos, with Militarist Empires benefitting significantly more from Rivalries than Pacifist ones (but paying more influence to be part of an Alliance). Naturally, Empires won't be particularly happy about being declared a Rival, and are pretty likely to rival you right back. Having a Rival will improve relations with their enemies and worsen relations with their friends, so the Rivalry system will act as a primary driver of conflict and alliance in the galaxy.
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AI Economics
Finally, I wanted to cover the topic of the AI's bookkeeping. While it may be far less exciting and far less visible to the player than its diplomatic behaviour, having solid economics is one of our biggest priorities for the Stellaris AI, for multiple reasons. Firstly, so that the AI is able to compete reasonably with the player without resorting to outright cheating. True, the AI will never be as good as an experienced player, but there is a big difference between the player being able to outproduce one AI Empire and the player being able to outproduce five of them together. Secondly, because of the Sector mechanic that was covered in DD 21, the AI will actively be making construction and management decisions on the player's planets, and while - again - it will never be as good as an experienced player making the decisions themselves, it needs to be good enough that the player doesn't feel like the AI is actively sabotaging their Empire.

In order to accomplish all this, a huge amount of time has been put into the AI's budgeting system. Every single mineral and energy credit that the AI takes in is earmarked for a particular budget post such as navies or new colonies, with the division between the posts being set according to the AI's personality and what it needs at the time. The AI is only permitted to spend appropriately budgeted resources, so it'll never fail to establish new colonies because it's too busy constructing buildings on its planet, or miss building a navy because mining stations are eating up its entire mineral income. In times of dire need, it can move resources from one budget post to another - if it's at war and its navy gets destroyed, expect it to pour every last mineral into building a new one.

When making decisions about what to construct, the AI looks primarily at what resources it has a critical need for (such as Energy if it's running a deficit), secondarily at what resources it's not producing a lot of compared to what it expects an Empire of its size to produce, and lastly at whatever it deems useful enough for the mineral investment. Sectors have additional logic to ensure they produce more of the resource you've set them to focus on, so an Energy sector will naturally overproduce Energy - you told it to, after all.
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Alright, that's all for today. Next week we'll be talking about debris and the fine art of reverse engineering.
 
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Well, first off, it is capped to 1000+ but thank you for clarifying it is the same in minus score. My question is why is it so high in the first place.

Probably to read more accurately quickly. Say hypothetically if 300 is the absolute most you can benefit from the reputation or that anything beyond that is so marginal it doesn't matter. And you have 360. You can easily see that you can do something dishonorable that will hurt your rep -60.
If i'm not mistaken in eu4 relations go beyond 200 aswell. It just stops counting at 200. For example if you had Royal Marriage 25+. Alliance 50+. Improved relationship 200+. the total would say 200+ even though it's really 275 and you have an invisible 75+ buffer.
 
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Uh, he said this was an AI personality, so it's not something you'd pick as a player. I imagine you strive to make more informed choices than the AI.
Why would you not be able to pick your own ideology and policies so I would imagine that I can do the same. It is probably going to be something like expansionist, militarist and fanatically xenophobic empire.
 
My question is why is it so high in the first place.
I said already: so it is essentially uncapped. The way Wiz says it, it sounds like a number higher than was possible to reach was chosen.

To make up some numbers, let's say the maximum possible set of modifiers will give you a +305 for positive and -430 for negative. Making the maximum +/- 1,000 allows the game to recognize, and act upon, the full amount rather than an arbitrary limit lower than the maximum possible (as it would be if they went with the old limit of +/- 200) without setting aside a much larger chunk of memory than the game needs to store this value (like if they made the maximum value +/- 2,097,152).
 
I said already: so it is essentially uncapped. The way Wiz says it, it sounds like a number higher than was possible to reach was chosen.

To make up some numbers, let's say the maximum possible set of modifiers will give you a +305 for positive and -430 for negative. Making the maximum +/- 1,000 allows the game to recognize, and act upon, the full amount rather than an arbitrary limit lower than the maximum possible (as it would be if they went with the old limit of +/- 200) without setting aside a much larger chunk of memory than the game needs to store this value (like if they made the maximum value +/- 2,097,152).

Seems fair enough to me. Never thought of it this way.

Thanks for the response!
 
That said, it's fact. Stellaris is mostly inspired by space operas and other 4X with unrealistic premises. Making a hard Sci-fi game would be... Something quite different.

Realistic space battle: there is no battle, just flinging rocks at near light speed at enemy home planets.
The problem is, sci-fi (and other fantasy) still has to be somewhat consistent with the reader's expectations. Sure, technology can have some aspects in which you have to suspend belief, but a few of those are fine as long as everything's logical, and if it deals with physical laws that people rarely deal with, then it barely even has any cost to change.

On the other hand, adding a magical force which effects how many embassies you can have doesn't really benefit from those, it's just an organization. Organizations are fundamental to our conception of social structure, and we interact with them all the time, so it takes a LOT of suspended disbelief. To say that the issue of realism is outweighed by other factors would be reasonable. To say that it's not relevant is inane.
 
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The problem is, sci-fi (and other fantasy) still has to be somewhat consistent with the reader's expectations. Sure, technology can have some aspects in which you have to suspend belief, but a few of those are fine as long as everything's logical, and if it deals with physical laws that people rarely deal with, then it barely even has any cost to change.

On the other hand, adding a magical force which effects how many embassies you can have doesn't really benefit from those, it's just an organization. Organizations are fundamental to our conception of social structure, and we interact with them all the time, so it takes a LOT of suspended disbelief. To say that the issue of realism is outweighed by other factors would be reasonable. To say that it's not relevant is inane.

How is that different from only being allowed to have 2 free leaders in EU4? It might be annoying and not in line with what you'd expect from reality, but it's done for the sake of gameplay and balance.
 
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The cap is -1000/+1000, so effectively uncapped. The Confederacy of Penkor *really* doesn't like me.
A very interesting change indeed. :)
 
At the moment, no. It may be something we look into later, but honestly leaders just aren't front in center in the way they'd need to be to be primary drivers of AI behavior.
It would be amazing if leaders had an impact on the game similar to what they have in CK2. I've always felt that EUIV felt very impersonal and that the actual portrait and traits of rulers caused there to be an air of believability behind everything. Since in reality rulers guide their countries. They aren't some faceless entity, they're a person with personality quirks. But they're also their country and what people often associate with a country. Like if someone says Putin, I think Russia. If someone says Obama I think America. If someone says Churchill, I think Britain. And so on and so fourth.
 
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Great DD, AI plans sounds solid and art looks good. It should also work well to add more personalities later with this system. This is one game where a sunset invasion DLC would not feel completely out of place.
 
On the other hand, adding a magical force which effects how many embassies you can have doesn't really benefit from those, it's just an organization. Organizations are fundamental to our conception of social structure, and we interact with them all the time, so it takes a LOT of suspended disbelief.

I would look at it in more abstract terms. Just think of the game mechanic of embassies as a way of representing the increased diplomatic skill of pacifist races instead of a building that houses your diplomats.
 
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Will the AI interpret aggression differently depending on the circumstances?

As in, will 100 aggression (my arbitrary measure of stuff taken) gained in a fight to the death (where you literally had to eliminate the other guy, like what the humans thought in Ender's Game) be less threatening than 100 aggression points from "I want a little from you ... and you ... and some from you, too"?

In more arbitrary terms:
A and B have exactly 0 relations both ways with all other empires and -1000 with eachother, and empire X has no vested interest in either party (for the fight to the search scenario). In the second scenario empires B is just another empire and empire A decides to take chunks out of B, D, and C. The question would be if empire X sees A as much more aggressive in one scenario (and if that perception potentially changes based on X's personality).
 
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