The following is a conversation with Thomas Sanholm. He's a professor at SameU and cocreator of
Labratus, which is the first AI system to beat top human players in the game of Heads Up No Limit
Texas Holdem. He has published over 450 papers on game theory and machine learning, including a
best paper in 2017 at NIPS, now renamed to New Rips, which is where I caught up with him for this
conversation. His research and companies have had wide reaching impact in the real world,
especially because he and his group not only propose new ideas, but also build systems to prove
that these ideas work in the real world. This conversation is part of the MIT course on
artificial journal intelligence and the artificial intelligence podcast. If you enjoy it, subscribe
on YouTube, iTunes, or simply connect with me on Twitter at Lex Friedman, spelled FRID. And now
here's my conversation with Thomas Sanholm. Can you describe at the high level the game of poker,
Texas Holdem, Heads Up Texas Holdem, for people who might not be familiar with this card game?
Yeah, happy to. So Heads Up No Limit Texas Holdem has really emerged in the AI community
as a main benchmark for testing these application independent algorithms for
imperfect information game solving. And this is a game that's actually played by humans. You don't
see that much on TV or casinos because, well, for various reasons, but you do see it in some
expert level casinos and you see it in the best poker movies of all time. It's actually an event
in the world series of poker, but mostly it's played online and typically for pretty big sums
of money. And this is a game that usually only experts play. So if you go to your home game
on a Friday night, it probably is not going to be Heads Up No Limit Texas Holdem. It might be
No Limit Texas Holdem in some cases, but typically for a big group and it's not as competitive.
Well, Heads Up means it's two players, so it's really like me against you. Am I better or are you
better, much like chess or go in that sense, but an imperfect information game which makes it much
harder because I have to deal with issues of you knowing things that I don't know and I know
things that you don't know instead of pieces being nicely laid on the board for both of us to see.
So in Texas Holdem, there's two cards that you only see that belong to you and there is
they gradually lay out some cards that add up overall to five cards that everybody can see.
Yeah, the imperfect nature of the information is the two cards that you're holding up front.
Yeah. So as you said, you know, you first get two cards in private each, and then you there's a
betting round, then you get three cards in public on the table, then there's a betting round, then
you get the fourth card in public on the table, there's a betting round, then you get the fifth
card on the table, there's a betting round. So there's a total of four betting rounds and four
tranches of information revelation, if you will. The only the first tranche is private and then
it's public from there. And this is probably by far the most popular game in AI and just
the general public in terms of imperfect information. So it's probably the most popular
spectator game to watch, right? So, which is why it's a super exciting game tackle. So it's on
the order of chess, I would say in terms of popularity, in terms of AI setting it as the bar
of what is intelligence. So in 2017, Libratus beats a few four expert human players. Can you
describe that event? What you learned from it? What was it like? What was the process in general
for people who have not read the papers in the study? Yeah. So the event was that we invited
four of the top 10 players with these specialist players in Heads Up No Limit Texas Holden,
which is very important because this game is actually quite different than the multiplayer
version. We brought them in to Pittsburgh to play at the reverse casino for 20 days. We wanted to
get 120,000 hands in because we wanted to get statistical significance. So it's a lot of hands
for humans to play, even for these top pros who play fairly quickly normally. So we couldn't just
have one of them play so many hands. 20 days, they were playing basically morning to evening.
And you raised 200,000 as a little incentive for them to play. And the setting was so that
they didn't all get 50,000. We actually paid them out based on how they did against the AI each.
So they had an incentive to play as hard as they could, whether they're way ahead or way behind
or right at the mark of beating the AI. And you don't make any money, unfortunately. Right. No,
we can't make any money. So originally, a couple of years earlier, I actually explored whether we
could actually play for money because that would be, of course, interesting as well to play against
the top people for money. But the Pennsylvania Gaming Board said no. So we couldn't. So this
is much like an exhibit, like for a musician or a boxer or something like that. Nevertheless,
they were keeping track of the money and brought us one close to $2 million, I think. So if it was
for real money, if you were able to earn money, that was a quite impressive and inspiring achievement.
Just a few details. What were the players looking at? Were they behind a computer? What
was the interface like? Yes, they were playing much like they normally do. These top players,
when they play this game, they play mostly online. So they used to playing through a UI.
And they did the same thing here. So there was this layout, you could imagine. There's a table
on a screen. There's the human sitting there. And then there's the AI sitting there. And the
screen shows everything that's happening. The cards coming out and shows the bets being made.
And we also had the betting history for the human. So if the human forgot what had happened in the
hand so far, they could actually reference back and so forth. Is there a reason they were given
access to the betting history? Well, it didn't really matter. They wouldn't have forgotten
anywhere. These are top quality people. But we just wanted to put out there so it's not the question
of the human forgetting and the AI somehow trying to get that advantage of better memory.
So what was that like? I mean, that was an incredible accomplishment. So what did it feel like
before the event? Did you have doubt, hope? Where was your confidence at?
Yeah, that's great. Great question. So 18 months earlier, I had organized a similar
brains versus AI competition with a previous AI called Cloudical. And we couldn't beat the humans.
So this time around, it was only 18 months later. And I knew that this new AI, Libratus,
was way stronger. But it's hard to say how you'll do against the top humans before you try.
So I thought we had about a 50 50 shot. And the international betting sites put us as a
four to one or five to one underdog. So it's kind of interesting that people really believe in people
and over AI, not just people, people don't just believe over believing themselves,
but they have overconfidence in other people as well, compared to the performance of AI.
And yeah, so we were a four to one or five to one underdog. And even after three days of beating
the humans in a row, we were still 50 50 on the international betting sites.
Do you think there's something special and magical about poker in the way people think about it?
In the sense you have, I mean, even in chess, there's no Hollywood movies. Poker is the star
of many movies. And there's this feeling that certain human facial expressions and body language,
eye movement, all these tells are critical to poker. Like you can look into somebody's soul
and understand their betting strategy and so on. So that's probably why the possibly do you think
that is why people have a confidence that humans will outperform because AI systems cannot in this
construct perceive these kinds of tells, they're only looking at betting patterns and
nothing else, the betting patterns and statistics. So what's more important to you if you step back
on human players, human versus human? What's the role of these tells of these ideas that we romanticize?
Yeah, so I'll split it into two parts. So one is why do humans trust humans more than AI and
have overconfidence in humans? I think that's not really related to the tell question. It's
just that they've seen these top players how good they are and they're really fantastic. So it's just
hard to believe that the AI could beat them. So I think that's where that comes from. And that's
actually maybe a more general lesson about AI that until you've seen it overperform a human,
it's hard to believe that it could. But then the tells, a lot of these top players, they're so good
at hiding tells that among the top players, it's actually not really worth it for them to invest a
lot of effort trying to find tells in each other because they're so good at hiding them. So yes,
at the kind of Friday evening game, tells are going to be a huge thing. You can read other people
and if you're a good reader, you'll read them like an open book. But at the top levels of poker,
no, the tells become a less much smaller and smaller aspect of the game as you go to the top
levels. The amount of strategies, the amounts of possible actions is very large, 10 to the power
of 100 plus. So there has to be some, I've read a few of the papers related that has,
it has to form some abstractions of various hands and actions. So what kind of abstractions are
effective for the game of poker? Yeah, so you're exactly right. So when you go from a game tree
that's 10 to the 161, especially in an imperfect information game, it's way too large to solve
directly. Even with our fastest equilibrium finding algorithms. So you want to abstract it
first. And abstraction in games is much trickier than abstraction in MDPs or other single agent
settings. Because you have these abstraction pathologies. But if I have a finer grained abstraction,
the strategy that I can get from that for the real game might actually be worse than the strategy
I can get from the coarse grained abstraction. So you have to be very careful. Now, the kinds
of abstractions just to zoom out, we're talking about there's the hands abstractions and then there
is betting strategies. Yeah, betting actions. So there's information abstraction to talk about
general games, information abstraction, which is the abstraction of what chance does. And this
would be the cards in the case of poker. And then there's action abstraction, which is abstracting
the actions of the actual players, which would be bets in the case of poker, yourself, any other
players, yes, yourself and other players. And for information abstraction, we were completely
automated. So these were these are algorithms, but they do what we call potential aware abstraction,
where we don't just look at the value of the hand, but also how it might materialize in the
good or bad hands over time. And it's a certain kind of bottom up process with integer programming
there and clustering and various aspects, how do you build this abstraction. And then in the
action abstraction, there, it's largely based on how humans other and other AI's have played
this game in the past. But in the beginning, we actually use an automated action abstraction
technology, which is provably convergent, that it finds the optimal combination of bet sizes,
but it's not very scalable. So we couldn't use it for the whole game, but we use it for the first
couple of betting actions. So what's more important, the strength of the hand, so the
information abstraction or the how you play them, the actions, does it, you know, the romanticized
notion again, is that it doesn't matter what hands you have, that the actions, the betting,
maybe the way you win, no matter what hands you have. Yeah, so that's why you have to play a lot
of hands, so that the role of luck gets smaller. So you could otherwise get lucky and get some good
hands, and then you're going to win the match. Even with thousands of hands, you can get lucky.
Because there's so much variance in no limit, Texas hold them, because if we both go all in,
it's a huge stack of variance. So there are these massive swings in no limit Texas hold them. So
that's why you have to play not just thousands, but over a hundred thousand hands to get statistical
significance. So let me ask another way this question. If you didn't even look at your hands,
but they didn't know that the opponents didn't know that, how well would you be able to do?
That's a good question. There's actually, I heard the story that there's this Norwegian female poker
player called Annette Oberstad, who's actually won a tournament by doing exactly that. But that
would be extremely rare. So you cannot really play well that way. Okay, so the hands do have
some role to play. So Lebrados does not use, as far as I understand, use learning methods,
deep learning. Is there room for learning in, you know, there's no reason why Lebrados doesn't,
you know, combine with an alpha go type approach for estimating the quality for function estimator.
What are your thoughts on this? Maybe as compared to another algorithm, which I'm not
that familiar with deep stack, the engine that does use deep learning that is unclear how well
it does, but nevertheless uses deep learning. So what are your thoughts about learning methods to
aid in the way that Lebrados plays the game of poker? Yeah, so as you said, Lebrados did not
use learning methods and played very well without them. Since then, we have actually actually here,
we have a couple of papers on things that do use learning techniques. Excellent. So and deep learning
in particular, and sort of the way you're talking about where it's learning an evaluation function.
But in imperfect information games, unlike, let's say in go war, now also in chess and shogi,
it's not sufficient to learn an evaluation for a state because the value of an information set
depends not only on the exact state, but it also depends on both players beliefs. Like if I have
a bad hand, I'm much better off if the opponent thinks I have a good hand. And vice versa,
if I have a good hand, I'm much better off if the opponent believes I have a bad hand. So the value
of a state is not just a function of the cards. It depends on if you will, the path of play,
but only to the extent that it's captured in the belief distributions. So that's why it's not as
simple as it is in perfect information games. And I don't want to say it's simple there either.
It's of course, very complicated computationally there too. But at least conceptually, it's very
straightforward. There's a state, there's an evaluation function, you can try to learn it.
Here, you have to do something more. And what we do is in one of these papers, we're looking at
allowing where we allow the opponent to actually take different strategies at the leaf of the
search tree, if you will. And that is a different way of doing it. And it doesn't assume therefore
a particular way that the opponent plays. But it allows the opponent to choose from a set of
different continuation strategies. And that forces us to not be too optimistic in a lookahead
search. And that's that's one way you can do sound lookahead search in imperfect information
games, which is very different, difficult. And in US, you were asking about deep stack, what they
did, it was very different than what we do, either in Libertadores or in this new work.
They were generally randomly generating various situations in the game. Then they were doing
the lookahead from there to the end of the game, as if that was the start of a different game. And
then they were using deep learning to learn those values of those states. But the states were not
just the physical states, they include the belief distributions. When you talk about lookahead,
or deep stack, or with Libertadores, does it mean considering every possibility that the game can
evolve? Are we talking about extremely sort of this exponential growth of a tree? Yes. So we're
talking about exactly that. Much like you doing alpha beta search or Monte Carlo tree search,
but with different techniques. So there's a different search algorithm. And then we have to
deal with the leaves differently. So if you think about what Libertadores did, we didn't have to
worry about this, because we only did it at the end of the game. So we would always terminate into a
real situation. And we would know what the payout is. It didn't do these depth limited lookaheads.
But now in this new paper, which is called depth limited, I think it's called depth limited search
for imperfect information games, we can actually do sound depth limited lookaheads. So we can
actually start to do the lookahead from the beginning of the game on, because that's too
complicated to do for this whole long game. So in Libertadores, we were just doing it for the end.
So and then the other side, this belief distribution. So is it explicitly modeled
what kind of beliefs that the opponent might have? Yeah, it is explicitly modeled, but it's not
assumed that beliefs are actually output, not input. Of course, the starting beliefs are input,
but they just fall from the rules of the game, because we know that the dealer deals uniformly
from the deck. So I know that every pair of cards that you might have is equally likely.
I know that for a fact, that just follows from the rules of the game. Of course,
except the two cards that I have, I know you don't have those. You have to take that into
account. That's called card removal, and that's very important. Is the dealing always coming
from a single deck in heads up? Yes. So you can assume single deck. So you know that if I have
the ace of spades, I know you don't have an ace of spades. So in the beginning, your belief is
basically the fact that it's a fair dealing of hands. But how do you start to adjust that belief?
Well, that's where this beauty of game theory comes. So Nash equilibrium, which John Nash
introduced in 1950, introduces what rational play is when you have more than one player.
And these are pairs of strategies where strategies are contingency plans, one for each player.
So that neither player wants to deviate to a different strategy, given that the other
doesn't deviate. But as a side effect, you get the beliefs from base rule. So Nash equilibrium
really isn't just deriving in these imperfect information games. Nash equilibrium doesn't
just define strategies. It also defines beliefs for both of us, and it defines beliefs for each state.
So at each state, each, if they call information sets, at each information set in the game,
there's a set of different states that we might be in, but I don't know which one we're in.
Nash equilibrium tells me exactly what is the probability distribution over those real
wall states in my mind. How does Nash equilibrium give you that distribution? So why?
I'll do a simple example. So you know the game Rock Paper Scissors? So we can draw it
as player one moves first, and then player two moves. But of course, it's important that player
two doesn't know what player one moved. Otherwise player two would win every time. So we can draw
that as an information set where player one makes one or three moves first. And then there's an
information set for player two. So player two doesn't know which of those nodes the world is in.
But once we know the strategy for player one, Nash equilibrium will say that you play one third
rock, one third paper, one third scissors. From that I can derive my beliefs on the information
set that they're one third, one third, one third. So Bayes gives you that. But is that specific
to a particular player? Or is it something you quickly update with those? No, the game theory
isn't really player specific. So that's also why we don't need any data. We don't need any history
how these particular humans played in the past or how any AI or even had played before. It's all
about rationality. So we just think the AI just thinks about what would a rational opponent do?
And what would I do if I were I am rational and what that that's that's the idea of game theory.
So it's really a data free opponent free approach. So it comes from the design of the game as opposed
to the design of the player. Exactly. There's no opponent modeling per se. I mean, we've done
some work on combining opponent modeling with game theory. So you can exploit weak players
even more. But that's another strand and in Libra, there's wouldn't turn that on. So I decided that
these players are too good. And when you start to exploit an opponent, you typically open yourself
up self up to exploitation. And these guys have so few holes to exploit and they're world's leading
experts in counter exploitation. So I decided that we're not going to turn that stuff on.
Actually, I saw a few your papers exploiting opponents sound very interesting to explore.
Do you think there's room for exploitation, generally outside of the broadest?
Is there a subject or people differences that could be exploited? Maybe not just in poker,
but in general interactions and negotiations all these other domains that you're considering?
Yeah, definitely. We've done some work on that. And I really like the work that hybridizes the two.
So you figure out what would a rational opponent do. And by the way, that's safe in these zero
sum games to players, zero sum games, because if the opponent does something irrational,
yes, it might show a throw of my beliefs. But the amount that the player can gain by throwing
of my belief is always less than they lose by playing poorly. So it's safe. But still,
if somebody's weak as a player, you might want to play differently to exploit them more.
So you can think about it this way, a game theoretic strategy is unbeatable,
but it doesn't maximally beat the other opponent. So the winnings per hand might be better
with a different strategy. And the hybrid is that you start from a game theoretic approach,
and then as you gain data about the opponent in certain parts of the game tree, then in those
parts of the game tree, you start to tweak your strategy more and more towards exploitation,
while still staying fairly close to the game theoretic strategy so as to not open yourself
up to exploitation too much. How do you do that? Do you try to vary up strategies, make it unpredictable?
It's like, what is it, tit for tat strategies in Prisoner's Dilemma or?
Well, that's a repeated game, simple Prisoner's Dilemma, repeated games. But even there,
there's no proof that says that that's the best thing. But experimentally, it actually does well.
So what kind of games are there, first of all? I don't know if this is something that you could
just summarize. There's perfect information games with all the information on the table.
There is imperfect information games. There's repeated games that you play over and over.
There's zero sum games. There's non zero sum games. And then there's a really important
distinction you're making to player versus more players. So what are what other games are there?
And what's the difference, for example, with this two player game versus more players? Yeah,
what are the key differences? Right. So let me start from the the basics. So
a repeated game is a game where the same exact game is played over and over.
In these extensive form games, where you think about three form, maybe with these
information sets to represent incomplete information, you can have kind of repetitive
interactions and even repeated games are a special case of that, by the way. But
the game doesn't have to be exactly the same. It's like in sourcing options. Yes, we're going to
see the same supply base year to year. But what I'm buying is a little different every time.
And the supply base is a little different every time and so on. So it's not really repeated.
So to find a purely repeated game is actually very rare in the world. So they're really a very
coarse model of what's going on. Then if you move up from just repeated, simple,
repeated matrix games, not all the way to extensive form games, but in between,
there's stochastic games, where you know, there's these, you think about it like these little
matrix games. And when you take an action and your own takes an action, they determine not which
next state I'm going to next game, I'm going to, but the distribution over next games,
where I might be going to. So that's the stochastic game. But it's like
like matrix games, repeated stochastic games, extensive form games, that is from less to more
general. And poker is an example of the last one. So it's really in the most general setting,
extensive form games. And that's kind of what the AI community has been working on and being
benchmarked on with this heads up no limit, Texas Holden. Can you describe extensive form games?
What's the model here? So if you're familiar with the tree form, so it's really the tree form,
like in chess, there's a search tree versus a matrix versus a matrix. Yeah. And that's the
matrix is called the matrix form or by matrix form or normal form game. And here you have the tree
form. So you can actually do certain types of reasoning there, that you lose the information
when you go to normal form. There's a certain form of equivalence, like if you go from three
form and you say it every possible contingency plan is a strategy, then I can actually go back
to the normal form, but I lose some information from the lack of sequentiality. Then the multiplayer
versus two player distinction is an important one. So two player games in zero sum are conceptually
easier and computationally easier. They're still huge like this one, this one. But they're conceptually
easier and computationally easier. In that conceptually, you don't have to worry about
which equilibrium is the other guy going to play when there are multiple, because any equilibrium
strategy is the best response to any other equilibrium strategy. So I can play a different
equilibrium from you and we'll still get the right values of the game. That falls apart even
with two players when you have general sum games. Even without cooperation, just even without
cooperation. So there's a big gap from two player zero sum to two player general sum, or even to
three players zero sum. That's a big gap, at least in theory. Can you maybe non mathematically
provide the intuition why it all falls apart with three or more players? It seems like you should
still be able to have a Nash equilibrium that's instructive, that holds. Okay, so it is true
that all finite games have a Nash equilibrium. So this is what your Nash actually proved.
So they do have a Nash equilibrium. That's not the problem. The problem is that there can be many.
And then there's a question of which equilibrium to select. So and if you select your strategy
from a different equilibrium and I select mine, then what does that mean? And in these non zero
sum games, we may lose some joint benefit by being just simply stupid, we could actually both be
better off if we did something else. And in three player, you get other problems also like collusion.
Like maybe you and I can gang up on a third player, and we can do radically better by colluding.
So there are lots of issues that come up there. So No Brown, the student you work with on this,
has mentioned, I looked through the AMA on Reddit, he mentioned that the ability of poker players
to collaborate would make the game. He was asked the question of, how would you make the game of
poker? Or both of you were asked the question, how would you make the game of poker beyond
being solvable by current AI methods? And he said that there's not many ways of making poker more
difficult, but a collaboration or cooperation between players would make it extremely difficult.
So can you provide the intuition behind why that is, if you agree with that idea?
Yeah, so we've done a lot of work on coalitional games. And we actually have a paper here with
my other student Gabriella Farina and some other collaborators on at NIPPS on that actually just
came back from the poster session where we presented this. So when you have a collusion,
it's a different problem. And it typically gets even harder then. Even the game representations,
some of the game representations don't really allow good computation. So we actually introduced a new
game representation for that. Is that kind of cooperation part of the model? Do you have
information about the fact that other players are cooperating? Or is it just this chaos that
where nothing is known? So there's some some things unknown. Can you give an example of a
collusion type game? Or is it usually? So like bridge. Yeah, so think about bridge. It's like
when you and I are on a team, our payoffs are the same. The problem is that we can't talk. So when
I get my cards, I can't whisper to you what my cards are. That would not be allowed. So we have
to somehow coordinate our strategies ahead of time. And only ahead of time. And then there's
certain signals we can talk about. But they have to be such that the other team also understands
that. So so that that's that's an example where the coordination is already built into the rules
of the game. But in many other situations, like auctions or negotiations or diplomatic
relationships, poker, it's not really built in. But it still can be very helpful for the
colliders. I've read you write somewhere, the negotiations, you come to the table with prior
like a strategy that, like that you're willing to do and not willing to do those kinds of things.
So how do you start to now moving away from poker, moving beyond poker into other applications
like negotiations? How do you start applying this to other to other domains, even real world
domains that you've worked on? Yeah, I actually have two startup companies doing exactly that.
One is called Strategic Machine. And that's for kind of business applications, gaming, sports,
all sorts of things like that. Any applications of this to business and to sports and to gaming,
to various types of things for in finance, electricity markets and so on. And the other
is called Strategy Robot, where we are taking these to military security, cybersecurity,
and intelligence applications. I think you worked a little bit in
how do you put it, advertisement, sort of suggesting ads kind of thing.
Yeah, that's another company, Optimized Markets. But that's much more about a
combinatorial market and optimization based technology. That's not using these
game theory decreasing technologies. I see. Okay, so what sort of high level do you think about
our ability to use game theoretic concepts to model human behavior? Do you think human behavior is
amenable to this kind of modeling? So outside of the poker games and where have you seen it
done successfully in your work? I'm not sure. The goal really is modeling humans.
Like for example, if I'm playing a zero sum game, I don't really care that the opponent is actually
following my model of rational behavior. Because if they're not, that's even better for me.
All right, so see with the opponents in games, the prerequisite is that you've formalized
the interaction in some way that can be amenable to analysis. I mean, you've done this amazing work
with mechanism design, designing games that have certain outcomes. But so I'll tell you an example
for my world of autonomous vehicles. We're studying pedestrians and pedestrians and cars
negotiate in this nonverbal communication. There's this weird game dance of tension where
pedestrians are basically saying, I trust that you won't kill me. And so as a J Walker,
I will step onto the road even though I'm breaking the law and there's this tension.
And the question is, we really don't know how to model that well in trying to model intent.
And so people sometimes bring up ideas of game theory and so on. Do you think that aspect
of human behavior can use these kinds of imperfect information approaches, modeling?
How do you start to attack a problem like that when you don't even know how to design the game
to describe the situation in order to solve it? Okay, so I haven't really thought about J walking.
But one thing that I think could be a good application in autonomous vehicles is the
following. So let's say that you have fleets of autonomous cars operating by different companies.
So maybe here's the Waymo fleet and here's the Uber fleet. If you think about the rules of the road,
they define certain legal rules, but that still leaves a huge strategy space open.
Like as a simple example, when cars merge, you know, how humans merge, you know,
they slow down and look at each other and try to merge. Wouldn't it be better if these situations
would already be prenegotiated so we can actually merge at full speed and we know that this is the
situation, this is how we do it and it's all going to be faster. But there are way too many
situations to negotiate manually. So you could use automated negotiation. This is the idea at least.
You could use automated negotiation to negotiate all of these situations or many of them in advance.
And of course, it might be that, hey, maybe you're not going to always let me go first.
Maybe you said, okay, well, in these situations, I'll let you go first. But in exchange, you're
going to give me two hours, you're going to let me go first in these situations. So it's this huge
combinatorial negotiation. And do you think there's room in that example of merging to
model this whole situation as an imperfect information game? Or do you really want to
consider it to be a perfect? No, that's a good question. Yeah. That's a good question. Do you
pay the price of assuming that you don't know everything? Yeah, I don't know. It's certainly
much easier. Games with perfect information are much easier. So if you can get away with it,
you should. But if the real situation is of imperfect information, then you're going to
have to deal with imperfect information. Great. So what lessons have you learned the annual
computer poker competition? An incredible accomplishment of AI. You look at the history
of the blue AlphaGo, these kind of moments when AI stepped up in an engineering effort and a
scientific effort combined to beat the best human player. So what do you take away from
this whole experience? What have you learned about designing AI systems that play these kinds
of games? And what does that mean for AI in general, for the future of AI development?
Yeah, so that's a good question. So there's so much to say about it.
I do like this type of performance oriented research, although in my group, we go all the
way from like idea to theory to experiments to big system building to commercialization. So we
span that spectrum. But I think that in a lot of situations in AI, you really have to build the
big systems and evaluate them at scale before you know what works and doesn't. And we've seen
that in the computational game theory community, that there are a lot of techniques that look good
in the small, but then they cease to look good in the large. And we've also seen that there are a
lot of techniques that look superior in theory. And I really mean in terms of convergence rates,
better like first order methods, better convergence rates like the CFR based algorithms,
yet the CFR based algorithms are the first fastest in practice. So it really tells me that you have
to test these in reality, the theory isn't tight enough, if you will, to tell you which
algorithms are better than the others. And you have to look at these things that in the large,
because any sort of projections you do from the small can at least in this domain be very misleading.
So that's kind of from a kind of science and engineering perspective, from a personal perspective,
it's been just a wild experience in that with the first poker competition, the first
brains versus AI man machine poker competition that we organized. There had been, by the way,
for other poker games, there had been previous competitions, but this was for heads up no limit,
this was the first. And I probably became the most hated person in the world of poker. And I
didn't mean to sigh. Why is that for cracking the game for? Yeah, it was a lot of people
felt that it was a real threat to the whole game, the whole existence of the game. If AI becomes
better than humans, people would be scared to play poker, because there are these superhuman
AIs running around taking their money and you know, all of that. So I just it was really aggressive.
Interesting. The comments were super aggressive. I got everything just short of death threats.
Do you think the same was true for chess? Because right now, they just completed the
world championships in chess, and humans just started ignoring the fact that there's AI systems
now that outperform humans and they still enjoy the game is still a beautiful game.
That's what I think. And I think the same thing happened in poker. And so I didn't
think of myself as somebody was going to kill the game. And I don't think I did.
I've really learned to love this game. I wasn't a poker player before, but
learn so many nuances about it from these AIs. And they've really changed how the game is played,
by the way. So they have these very Martian ways of playing poker. And the top humans are now
incorporating those types of strategies into their own play. So if anything, to me, our work has made
poker a richer, more interesting game for humans to play, not something that is going to steer
humans away from it entirely. Just a quick comment on something you said, which is,
if I may say so, in academia is a little bit rare sometimes. It's pretty brave to put your ideas
to the test in the way you described, saying that sometimes good ideas don't work when you actually
try to apply them at scale. So where does that come from? I mean, if you could do advice for
people, what drives you in that sense? Were you always this way? I mean, it takes a brave person,
I guess is what I'm saying, to test their ideas and to see if this thing actually works against human
top human players and so on. I don't know about brave, but it takes a lot of work.
It takes a lot of work and a lot of time to organize, to make something big and to organize
an event and stuff like that. And what drives you in that effort? Because you could still,
I would argue, get a Best Paper Award at NIPS as you did in 17 without doing this.
That's right, yes.
So in general, I believe it's very important to do things in the real world and at scale.
And that's really where the pudding, if you will, proves in the pudding. That's where it is.
In this particular case, it was kind of a competition between different groups.
And for many years, as to who can be the first one to beat the top humans at heads up,
no limit takes us hold them. So it became kind of like a competition who can get there.
Yeah, so a little friendly competition could do wonders for progress.
Yes, absolutely.
So the topic of mechanism design, which is really interesting, also kind of new to me,
except as an observer of, I don't know, politics and any, I'm an observer of mechanisms,
but you write in your paper, an automated mechanism design that I quickly read.
So mechanism design is designing the rules of the game,
so you get a certain desirable outcome. And you have this work on doing so in an automatic
fashion as opposed to fine tuning it. So what have you learned from those efforts?
If you look, say, I don't know, at complex, it's like our political system. Can we design our
political system to have in an automated fashion, to have outcomes that we want? Can we design
something like traffic lights to be smart, where it gets outcomes that we want?
So what are the lessons that you draw from that work?
Yeah, so I still very much believe in the automated mechanism design direction.
Yes.
But it's not a panacea. There are impossibility results in mechanism design,
saying that there is no mechanism that accomplishes objective X in class C.
So it's not going up, there's no way, using any mechanism design tools, manual or automated,
to do certain things in mechanism design.
Can you describe that again? So meaning there, it's impossible to achieve that?
Yeah, there's also an impossible. So these are not statements about human ingenuity,
who might come up with something smart. These are proofs that if you want to accomplish properties
X in class C, that is not doable with any mechanism. The good thing about automated
mechanism design is that we're not really designing for a class, we're designing for specific settings
at a time. So even if there's an impossibility result for the whole class, it just doesn't
mean that all of the cases in the class are impossible, it just means that some of the
cases are impossible. So we can actually carve these islands of possibility within these
non impossible classes. And we've actually done that. So one of the famous results in mechanism
design is a Meyers and Settled Weight theorem by Roger Meyers and Mark Settled Weight from 1983.
So it's an impossibility of efficient trade under imperfect information. We show that
you can in many settings avoid that and get efficient trade anyway.
Depending on how you design the game. Depending how you design the game. And of course,
it doesn't in any way contradict the impossibility result. The impossibility result is still there,
but it just finds spots within this impossible class where in those spots you don't have the
impossibility. Sorry if I'm going a bit philosophical, but what lessons do you draw towards like I
mentioned politics or the human interaction and designing mechanisms for outside of just
these kinds of trading or auctioning or
purely formal games or human interaction like a political system. Do you think it's applicable
to politics or to business, to negotiations, these kinds of things, designing rules that have
certain outcomes? Yeah, yeah, I do think so. Have you seen success that successfully done?
There hasn't really. Oh, you mean mechanism design or automated mechanism? Automated mechanism design.
So mechanism design itself has had fairly limited success so far. There are certain cases,
but most of the real world situations are actually not sound from a mechanism design
perspective. Even in those cases where they've been designed by very knowledgeable mechanism
design people, the people are typically just taking some insights from the theory and applying
those insights into the real world rather than applying the mechanisms directly. So one famous
example of is the FCC spectrum auctions. So I've also had a small role in that and
very good economists have been working on that with no game theory. Yet the rules that are
designed in practice there, they're such that bidding truthfully is not the best strategy.
Usually mechanism design, we try to make things easy for the participants. So telling the truth
is the best strategy. But even in those very high stakes auctions where you have tens of billions
of dollars worth of spectrum being auctioned, truth telling is not the best strategy.
And by the way, nobody knows even a single optimal bidding strategy for those auctions.
What's the challenge of coming up with an optimal bid? Because there's a lot of players and there's
imperfections. It's not so much there, a lot of players, but many items for sale. And these
mechanisms are such that even with just two items or one item, bidding truthfully wouldn't be
the best strategy. If you look at the history of AI, it's marked by seminal events and an
AlphaGo beating a world champion, human go player, I would put Lebrados winning the heads
up no limit hold them as one of such event. Thank you. And what do you think is the next such event?
Whether it's in your life or in the broadly AI community that you think might be out there
that would surprise the world. So that's a great question and I really know the answer. In terms
of game solving heads up no limit takes us all and really was the one remaining widely agreed
upon benchmark. So that was the big milestone. Now, are there other things? Yeah, certainly
there are, but there there is not one that the community has kind of focused on. So what could
be other things? There are groups working on Starcraft. There are groups working on Dota 2.
These are video games. Yes, or you could have like diplomacy or Hanabi, you know, things like
that. These are like recreational games, but none of them are really acknowledged as kind of the
main next challenge problem. Like chess or go or heads up no limit takes us hold them was.
So I don't really know in the game solving space what is or what will be the next benchmark. I
kind of hope that there will be a next benchmark because really the different groups working on
the same problem really drove these application independent techniques forward very quickly
over 10 years. Do you think there's an open problem that excites you that you start moving
away from games into real world games like say the stock market trading? Yeah, so that's kind
of how I am. So I am probably not going to work as hard on these recreational benchmarks.
I'm doing two startups on game solving technology strategic machine and strategy robot and we're
really interested in pushing this stuff into practice. What do you think would be really,
you know, a powerful result that would be surprising that would be if you can say, I mean,
it's, you know, five years, 10 years from now, something that statistically would say is not
very likely, but if there's a breakthrough would achieve. Yeah, so I think that overall,
we're in a very different situation in game theory than we are in, let's say, machine learning. Yes.
So in machine learning, it's a fairly mature technology and it's very broadly applied and
proven success in the real world. In game solving, there are almost no applications yet.
We have just become superhuman, which machine learning you could argue happened in the 90s,
if not earlier, and at least on supervised learning, certain complex supervised learning
applications. Now, I think the next challenge problem, I know you're not asking about it this
way, you're asking about technology breakthrough. But I think that big breakthrough is to be able
to show that, hey, maybe most of, let's say, military planning or most of business strategy
will actually be done strategically using computational game theory. That's what I would
like to see as a next five or 10 year goal. Maybe you can explain to me again, forgive me if this
is an obvious question, but machine learning methods and neural networks suffer from not
being transparent, not being explainable. Game theoretic methods, Nash Equilibria,
do they generally, when you see the different solutions, are they, when you talk about military
operations, are they, once you see the strategies, do they make sense? Are they explainable or do
they suffer from the same problems as neural networks do? So that's a good question. I would say
a little bit yes and no. And what I mean by that is that these game theoretic strategies,
let's say, Nash Equilibrium, it has provable properties. So it's unlike, let's say, deep
learning where you kind of cross your fingers, hopefully it'll work. And then after the fact,
when you have the weights, you're still crossing your fingers, and I hope it will work. Here,
you know that the solution quality is there. There's provable solution quality guarantees.
Now, that doesn't necessarily mean that the strategies are human understandable.
That's a whole other problem. So I think that deep learning and computational game theory
are in the same boat in that sense, that both are difficult to understand.
But at least the game theoretic techniques, they have this
guarantees of solution quality. So do you see business operations, strategic operations,
even military in the future being at least the strong candidates being proposed by automated
systems? Do you see that? Yeah, I do. I do. But that's more of a belief than a substantiated fact.
Depending on where you land, an optimism or pessimism, that's a really, to me, that's an
exciting future, especially if there's provable things in terms of optimality. So looking into
the future, there's a few folks worried about the, especially you look at the game of poker,
which is probably one of the last benchmarks in terms of games being solved. They worry about
the future and the existential threats of artificial intelligence. So the negative impact
in whatever form on society, is that something that concerns you as much? Or are you more optimistic
about the positive impacts of AI? I am much more optimistic about the positive impacts.
So just in my own work, what we've done so far, we run the nationwide kidney exchange.
Hundreds of people are walking around alive today, who would it be? And it's increased employment.
You have a lot of people now running kidney exchanges and at transplant centers, interacting
with the kidney exchange. You have some extra surgeons, nurses, anesthesiologists, hospitals,
all of that. So employment is increasing from that and the world is becoming a better place.
Another example is combinatorial sourcing auctions. We did 800 large scale combinatorial
sourcing auctions from 2001 to 2010 in a previous startup of mine called Combinet.
And we increased the supply chain efficiency on that $60 billion of spend by 12.6%. So that's
over $6 billion of efficiency improvement in the world. And this is not like shifting value from
somebody to somebody else, just efficiency improvement, like in trucking, less empty
driving. So there's less waste, less carbon footprint and so on. This is a huge positive
impact in the near term. But sort of to stay in it for a little longer, because I think game theory
is a role to play here. Let me actually come back on that. That's one thing. I think AI is also going
to make the world much safer. So that's another aspect that often gets overlooked.
Well, let me ask this question. Maybe you can speak to the safer. So I talked to Max Tagmark
and Stuart Russell, who are very concerned about existential threats of AI. And often,
the concern is about value misalignment. So AI systems basically working, operating towards
goals that are not the same as human civilization, human beings. So it seems like game theory has
a role to play there to make sure the values are aligned with human beings. I don't know if that's
how you think about it. If not, how do you think AI might help with this problem? How do you think
AI might make the world safer? Yeah, I think this value misalignment is a fairly theoretical
worry. And I haven't really seen it in because I do a lot of real applications. I don't see it
anywhere. The closest I've seen it was the following type of mental exercise, really,
where I had this argument in the late 80s when we were building these transportation optimization
systems. And somebody had heard that it's a good idea to have high utilization of assets.
So they told me that, hey, why don't you put that as objective? And we didn't even put it as an
objective, because I just showed him that if you had that as your objective, the solution would be
to load your trucks full and drive in circles. Nothing would ever get delivered. You'd have
100% utilization. So yeah, I know this phenomenon. I've known this for over 30 years. But I've never
seen it actually be a problem in reality. And yes, if you have the wrong objective, the AI will
optimize that to the hilt. And it's going to hurt more than some human who's kind of trying to
solve it in a half baked way with some human insight, too. But I just haven't seen that
materialize in practice. There's this gap that you've actually put your finger on
very clearly just now between theory and reality that's very difficult to put into words, I think.
It's what you can theoretically imagine, the worst possible case or even, yeah, I mean,
bad cases. And what usually happens in reality. So for example, to me, maybe it's something you
can comment on, having grown up and I grew up in the Soviet Union. You know, there's currently
10,000 nuclear weapons in the world. And for many decades, it's theoretically surprising to me
that the nuclear war is not broken out. Do you think about this aspect from a game
theoretic perspective in general? Why is that true? Why? In theory, you could see how things
go terribly wrong. And somehow yet they have not. Yeah, how do you think so? So I do think that
about that a lot. I think the biggest two threats that we're facing as mankind, one is climate
change, and the other is nuclear war. So so those are my main two worries that they worry about.
And I've tried to do something about climate thought about trying to do something for climate
change twice. Actually, for two of my startups, I've actually commissioned studies of what we
could do on those things. And we didn't really find a sweet spot, but I'm still keeping an eye out
on that if there's something where we could actually provide a market solution or optimization
solution or some other technology solution to problems. Right now, like for example, pollution
critic markets was what we were looking at then. And it was much more the lack of political will
by those markets were not so successful, rather than bad market design. So I could go in and
make a better market design. But that wouldn't really move the needle on the world very much
if there's no political will and in the US, you know, the market, at least the Chicago market
was just shut down, and so on. So then it doesn't really help how great your market design was.
And on the nuclear side, it's more so global warming is a more encroaching problem.
You know, nuclear weapons have been here. It's an obvious problem has just been sitting there.
So how do you think about what is the mechanism design there that just made everything seem stable?
And are you still extremely worried? I am still extremely worried. So you probably know the simple
game theory of mad. So this was a mutually assured destruction. And it doesn't require any
computation with small matrices, you can actually convince yourself that the game is such that
nobody wants to initiate. Yeah, that's a very coarse grained analysis. And it really works in
a situation where you have two superpowers or small numbers of superpowers. Now things are
very different. You have a smaller nuke. So the threshold of initiating is smaller. And you have
smaller countries and non non nation actors who may get nukes and so on. So it's I think it's
riskier now than it was maybe ever before. And what idea application of AI, you've talked about
a little bit, but what is the most exciting to you right now? I mean, you're here at NIPS,
NewRips. Now, you have a few excellent pieces of work. But what are you thinking into the future
with several companies you're doing? What's the most exciting thing or one of the exciting things?
The number one thing for me right now is coming up with these scalable techniques for
game solving and applying them into the real world. I'm still very interested in market design
as well. And we're doing that in the optimized markets. But I'm most interested if number one
right now is strategic machine strategy robot getting that technology out there and seeing
as you're in the trenches doing applications, what needs to be actually filled, what technology
gaps still need to be filled. So it's so hard to just put your feet on the table and imagine what
needs to be done. But when you're actually doing real applications, the applications tell you
what needs to be done. And I really enjoy that interaction. Is it a challenging process to
apply some of the state of the art techniques you're working on, and having the various players in
industry or the military, or people who could really benefit from it actually use it? What's
that process like of, you know, in autonomous vehicles, we work with automotive companies and
they're in many ways are a little bit old fashioned, it's difficult. They really want to use this
technology, there's clearly will have a significant benefit. But the systems aren't quite in place
to easily have them integrated in terms of data in terms of compute in terms of all these kinds
of things. So do you, is that one of the bigger challenges that you're facing? And how do you
tackle that challenge? Yeah, I think that's always a challenge that that's kind of slowness and inertia
really of let's do things the way we've always done it. You just have to find the internal
champions that the customer who understand that hey, things can't be the same way in the future,
otherwise bad things are going to happen. And it's in autonomous vehicles, it's actually very
interesting that the car makers are doing that, and they're very traditional. But at the same time,
you have tech companies who have nothing to do with cars or transportation, like Google and Baidu,
really pushing on autonomous cars. I find that fascinating. Clearly, you're super excited about
how actually these ideas have an impact in the world. In terms of the technology, in terms of
ideas and research, are there directions that you're also excited about, whether that's on the
some of the approaches you talked about for imperfect information games, whether it's applying
deep learning to some of these problems? Is there something that you're excited in
in the research side of things? Yeah, yeah, lots of different things in the game solving.
So solving even bigger games, games where you have more hidden action of the player
actions as well. poker is a game where really chance actions are hidden, or some of them are
hidden, but the player actions are public. multiplayer games or various sorts, collusion,
opponent exploitation, all and even longer games. So games that basically go forever,
but they're not repeated. So see extensive fun games that go forever. What would that even look
like? How do you represent that? How do you solve that? What's an example of a game like that?
This is some of the stochastic games that you mentioned. Let's say business strategy. So it's
and not just modeling like a particular interaction, but thinking about the business from here to
eternity. Or I see, or let's let's say military strategy. So it's not like war is going to go away.
How do you think about military strategy that's going to go forever? How do you even model that?
How do you know whether a move was good that you use somebody made? And so on. So that that's
kind of one direction. I'm also very interested in learning much more scalable techniques for
integer programming. So we had an ICML paper this summer on that, the first automated algorithm
configuration paper that has theoretical generalization guarantees. So if I see these many
training examples, and I tool my algorithm in this way, it's going to have good performance
on the real distribution, which I've not seen. So which is kind of interesting that, you know,
algorithm configuration has been going on now for at least 17 years seriously. And there has not
been any generalization theory before. Well, this is really exciting. And it's been, it's a huge
honor to talk to you. Thank you so much, Tomas. Thank you for bringing Lebrates to the world
and all the great work you're doing. Well, thank you very much. It's been fun. Good questions.