an artificial intelligence developed by Carnegie Mellon University, made
history by defeating four of the world’s best professional poker players
in a marathon 20-day poker competition, called “Brains Vs. Artificial
Intelligence: Upping the Ante” at Rivers Casino in Pittsburgh.
Once the last of 120,000 hands of Heads-up, No-Limit Texas Hold’em were
played on Jan. 30, Libratus led the pros by a collective $1,766,250 in
chips. The developers of Libratus — Tuomas Sandholm, professor of
computer science, and Noam Brown, a Ph.D. student in computer science —
said the sizable victory is statistically significant and not simply a
matter of luck.
“The best AI’s ability to do strategic reasoning with imperfect
information has now surpassed that of the best humans,” Sandholm said.
This new milestone in artificial intelligence has implications for any
realm in which information is incomplete and opponents sow
misinformation, said Frank Pfenning, head of the Computer Science
Department in CMU’s School of Computer Science. Business negotiation,
military strategy, cybersecurity and medical treatment planning could
all benefit from automated decision-making using a Libratus-like AI.
“The computer can’t win at poker if it can’t bluff,” Pfenning said.
“Developing an AI that can do that successfully is a tremendous step
forward scientifically and has numerous applications. Imagine that your
smartphone will someday be able to negotiate the best price on a new car
for you. That’s just the beginning.”
The pros — Dong Kim, Jimmy Chou, Daniel McAulay and Jason Les — will
split a $200,000 prize purse based on their respective performances
during the event.
McAulay, of Scotland, said Libratus was a tougher opponent than he
expected, but it was exciting to play against it.
“Whenever you play a top player at poker, you learn from it,” McAulay
Les, of Costa Mesa, Calif., agreed that superior opponents help poker
“Usually, you have to lose a lot and pay a lot of money for the
experience,” he said. “Here, at least I’m not losing any money.”
“This experiment demanded that we assemble some of the world’s best
professional poker players who specialize in Heads-up No-Limit Texas
Hold’em and that they would play to the best of their abilities
throughout the long contest,” Brown said. “These players more than met
that description and proved to be a tenacious team of opponents for
Libratus, studying and strategizing together throughout the event.”
Libratus’ victory was made possible by the Pittsburgh Supercomputing
Center’s Bridges computer, on which the AI computed its strategy before
and during the event, and by Rivers Casino, which hosted the event.
“Rivers Casino was proud to partner with Carnegie Mellon University and
the Pittsburgh Supercomputing Center to host the Brains Vs. Artificial
Intelligence: Upping the Ante competition,” said Craig Clark, general
manager of Rivers Casino. “History-making events like this are very
important as they increase awareness of how companies in Pittsburgh are
impacting the world.”
The event was surrounded by speculation about how Libratus was able to
improve day to day during the competition. It turns out it was the pros
themselves who taught Libratus about its weaknesses.
“After play ended each day, a meta-algorithm analyzed what holes the
pros had identified and exploited in Libratus’ strategy,” Sandholm said.
“It then prioritized the holes and algorithmically patched the top three
using the supercomputer each night. This is very different than how
learning has been used in the past in poker. Typically researchers
develop algorithms that try to exploit the opponent’s weaknesses. In
contrast, here the daily improvement is about algorithmically fixing
holes in our own strategy.”
Sandholm also said that Libratus’ end-game strategy, which was computed
live with the Bridges computer for each hand, was a major advance.
“The end-game solver has a perfect analysis of the cards,” he said.
It was able to update its strategy for each hand in a way that ensured
any late changes would only improve the strategy. Over the course of the
competition, the pros responded by making more aggressive moves early in
the hand, no doubt to avoid playing in the deep waters of the endgame
where the AI had an advantage, he added.
Sandholm will be sharing all of Libratus’ secrets now that the
competition is over, beginning with invited talks at the Association for
the Advancement of Artificial Intelligence meeting Feb. 4-9 in San
Francisco and in submissions to peer-reviewed scientific conferences and
Throughout the competition, Libratus recruited the raw power of
approximately 600 of Bridges’ 846 compute nodes. Bridges total speed is
1.35 petaflops, about 7,250 times as fast as a high-end laptop and its
memory is 274 Terabytes, about 17,500 as much as you’d get in that
laptop. This computing power gave Libratus the ability to play four of
the best Texas Hold’em players in the world at once and beat them.
Developer Tuomas Sandholm and the Pittsburgh Supercomputing Center’s
Bridges computer, on which the AI computed its strategy.
“We designed Bridges to converge high-performance computing and
artificial intelligence,” said Nick Nystrom, PSC’s senior director of
research and principal investigator for the National Science
Foundation-funded Bridges system. “Libratus’ win is an important
milestone toward developing AIs to address complex, real-world problems.
At the same time, Bridges is powering new discoveries in the physical
sciences, biology, social science, business and even the humanities.
With its unique emphasis on usability, new projects are always welcome.”
Sandholm said he will continue his research push on the core
technologies involved in solving imperfect-information games and in
applying these technologies to real-world problems. That includes his
work with Optimized Markets, a company he founded to automate
played a pivotal role in developing both computer chess, which
eventually beat the human world champion, and Watson, the AI that beat
top human Jeopardy! competitors,” Pfenning said. “It has been very
exciting to watch the progress of poker-playing programs that have
finally surpassed the best human players. Each one of these
accomplishments represents a major milestone in our understanding of
Brains Vs. AI was sponsored by GreatPoint Ventures, Avenue4Analytics,
TNG Technology Consulting GmbH, the journal Artificial Intelligence,
Intel and Optimized Markets, Inc. Carnegie Mellon’s School of Computer
Science partnered with Rivers Casino, the Pittsburgh Supercomputing
Center (PSC) through a peer-reviewed XSEDE allocation, and Sandholm’s
Electronic Marketplaces Laboratory for the event.
Head’s-Up No-Limit Texas Hold’em is an exceedingly complex game, with
10160 (the number 1 followed by 160 zeroes) information sets — each set
being characterized by the path of play in the hand as perceived by the
player whose turn it is. That’s vastly more information sets than the
number of atoms in the universe.
The AI must make decisions without knowing all of the cards in play,
while trying to sniff out bluffing by its opponent. As “no-limit”
suggests, players may bet or raise any amount up to all of their chips.