While a lot of the immediate focus was on the achievement of beating a top professional player, if you looked beneath the surface something quite magical was happening. AlphaGo discovered some truly beautiful and creative moves that have since inspired Go players across the world to try these new strategies for themselves. Find out more about
In May 2017 we teamed up with the world’s best Go players for The Future of Go Summit - a five day festival of Go and artificial intelligence in the game's birthplace, China - to uncover yet more secrets of this ancient game. A variety of game formats have been designed to unearth even more new strategies - including pair Go, team Go, and a 1:1 match with the world’s number one player Ke Jie.
The first opening surprise in this game arose almost immediately on move 7, a four-space extension from the upper right in which AlphaGo played one space closer to the corner than in the usual Chinese opening. Ke Jie, playing White, took advantage of the wider space on the right side to approach the lower right corner, and both sides continued to position themselves in an opening that AlphaGo evaluated as ideal for both sides.
White 20 in particular, a counter-intuitive second-line probe into Black's framework on the lower right, showcased Ke Jie's sublime positional judgment. With the combination of 40 through 44, a peep followed by a push and cut, Ke Jie divided the lower left into several groups to set up a complex position with endless variations. As commentator Hajin Lee remarked, while Ke Jie had played a territorial style in the first match and a complication-seeking style in the second, he pursued a combination of these approaches in the third match.
Black 59, loosely enclosing White's group in an indirect response to White's approach on the lower side, was a beautiful move by AlphaGo that set up a sequence to build strength in the centre before connecting. Ke Jie responded with a spirited counter, temporarily leaving the left side to establish a group in the lower right and wait for future opportunities. Black and White's groups began a vigorous dance in the centre, matching each other's weaknesses and strengths to create a delicate balance.
When Ke Jie attained a local advantage in the centre, AlphaGo switched to build a powerful framework on the top that spurred White to invade. The action came to a head when Ke Jie sacrificed the territory on the upper side to AlphaGo, gaining initiative to pressure the lower left. After AlphaGo protected its group, the match proceeded towards the endgame. Ke Jie revived his stones in the upper left to take the territorial lead, but this sequence left AlphaGo just enough latitude to take control of his group in the centre, and White resigned after 209 moves.
Ke Jie created complex situations with many interlocking battles, demonstrating an incredible ability to keep AlphaGo guessing. We hope that this special series of matches can serve as a platform for analysis and new knowledge for Go players and the Go community. It was thrilling to watch the games unfold, and it has been a huge honour for all of us to have the chance to play with such a great master, Ke Jie.
“We held this event aiming to discover new insights into this ancient, beautiful game. I can safely say that what has taken place since Tuesday has exceeded our highest hopes. We have seen many new and exciting moves, and we also saw AlphaGo truly pushed to its limits by the great genius Ke Jie, particularly in the amazing game two. It was thrilling to be in the match room and the control room watching that game unfold, and it has been a truly huge honour to play with such a great master.”
Demis Hassabis, CEO of DeepMind, during the post match wrap up
"Playing the match with AlphaGo is impressive, for me it’s a transformational moment. It’s still a wonderful experience that we can play the game, we can feel that we have a further understanding of the game of Go, we can feel that we’ve learned a lot.”
Tang Weixing, 9 Dan Professional, during post match wrap up
Winning and losing took a back seat as players had to work strategically with their teammates to anticipate the opposing side’s play and tactics. The results were both fascinating and fun, with a series of inventive and intriguing moves from the professionals and AlphaGo alike.
In Pair Go, the first of the day’s matches, top Chinese professionals Gu Li and Lian Xiao each had their own AlphaGo teammate, alternating moves in tag team style. In the second, Team Go, five of China’s top professional Go players had the unique challenge of working together to take on AlphaGo’s distinctive style.
White 12 (Lian Xiao + AlphaGo) brought the first of the match's many surprises, when AlphaGo declined the normal response to Black's (Gu Li + AlphaGo) pressing move in favor of a one-space jump. While not a standard joseki, this move allowed White to claim the corner while restricting Black's influence, so the result was a balanced position that worked well for both sides. The opening quickly evolved into a contrast between Black's influence and White's territory, but AlphaGo changed course for Black with the second-line invasion at 31. Mysterious at first, this move ultimately proved effective when Black traded the corner for a powerful formation on both sides. Gu Li confirmed this early advantage with Black 61, a calm and confident choice converting the influence on the right into solid territory. In response, White built up the left side before reducing Black's influence in the center.
Both sides upped the ante as the middle game progressed, resulting in a dazzlingly complex interplay of groups culminating in Black 103. A nose tesuji (tactical play), it compelled White's stones to escape, helping Black lay claim to the left side. Through the late middle game, the position remained close, but a surprising peep by AlphaGo at 120 and a six-stone sacrifice laid the groundwork for Lian Xiao's decisive invasion on the left side at 154. This invasion led to a dramatic ko, which White translated into a large gain on the right side. Though Black gained in the upper left corner in return, White held on to the advantage and Black resigned after 220 moves.
Both the team of top Chinese professionals (playing Black) and AlphaGo (playing White) began with calm openings. Black 27 was a very interesting decision from the team, avoiding the normal forcing moves of the atari and connection in favor of a more indirect threat. White captured Black's two sacrifice stones and the positional play continued, with the team striving to make the most of AlphaGo's potential weakness. With move 40, a strong connecting play, AlphaGo succeeded in shoring up White's position. In the following moves, AlphaGo continued to take territory. The team of five responded vigorously, starting a large ko on the right side. The ko continued for dozens of moves, finally concluding when the team declined to respond to a large ko threat on the lower left, finishing the ko to claim the corner. Each side came out with a wide swath of territory, Black on the right and White on the left, but White's territory proved slightly superior and the team eventually resigned.
The match proved to be a pleasure to watch, giving spectators the unique opportunity to see world-class players analyse, laugh, and debate as they explored the future of Go.
"AlphaGo gave me a lot of confidence! This is an unforgettable experience for me. AlphaGo could actually broaden the horizon of Go playing. It could bring more imagination into Go.”
Lian Xiao, 8 Dan Professional, Pair Go player, in the post-match press conference
“AlphaGo played many surprising moves in the game. Playing games like this will give us new ideas about how to play. If there’s an opportunity, we should do more of these.” -
Gu Li, 9 Dan Professional, Pair Go player and Chinese language commentator for Team Go
“For the team format, it may feel that a joint effort is stronger. But everyone has their own ideas so it is not necessarily one plus one is larger than two, especially when you are competing against a strong opponent. I feel we have learned a lot today.”
Weixing Tang, 9 Dan Professional, Team Go
“Today wasn’t really about winning or losing. It was about exploring the different formats and different possibilities in the game of Go and seeing what we could learn. Pair go was a beautiful game. All four players made some brilliant and creative moves. It felt like four painters working together on a shared canvas, all with different styles, all combining together to make something truly beautiful.”
David Silver, AlphaGo Lead Researcher, during the post-match press conference
Both sides opened in excellent form, with AlphaGo playing the same 3-3 point enclosure on its second move that Ke Jie played in match 1. AlphaGo initiated one of its favorite joseki (standard corner sequences) with move 11, which required a local response and quickly settled the position. During this sequence, Black 23 through 27 were hailed by commentators as an intelligently nuanced move order, a cut followed by a one-space jump that posed White the difficult challenge of finding an efficient way to capture the corner. Ke Jie's decision to return to the lower side, with a three-space jump at move 30, displayed a finely honed positional judgment. The following moves quietly set the stage for the coming spectacle by creating seven separate groups on the left and lower sides, all of them interrelated and none of them settled. This type of complex interaction, impossible to calculate fully and demanding the most of each player's value judgment and intuition, brought both Ke Jie and AlphaGo into their element.
The central tension of this game arose from the critical exchange of White's corner attachment at 56 for Black's connection at 57. Most professional players would regard White 56 as sente, a move that demands an immediate local response. However, AlphaGo turned back to connect at 57, a move that surprised many commentators. The following 30 moves, in which the players leapt from one arena to another, were both sharp and subtle, climaxing in a game-determining ko in the lower left corner. With many groups hanging in the balance, both sides continued raising the stakes. Ke Jie played daringly, creating the possibility of sacrificing the ko and two of his groups to take AlphaGo's two groups in the upper left on an even larger scale. However, AlphaGo chose to settle the ko and the game by connecting at move 137, conceding enormous gains to White on the lower left to secure even greater profits in the lower right. As White could not control the whole upper left, Black's territorial advantage proved decisive.
From our perspective, this was one of the most inspiring games we have ever had the honour to be part of. Drawing on his deep knowledge and balanced yet fierce style, Ke Jie pushed AlphaGo to its limits, creating a masterpiece in which both players explored the complexity that lies at the heart of Go. We hope that Go players and fans around the world enjoyed it!
"If you know Go, you know that AlphaGo in today’s game, played some moves which were opposite from his vision of maximising the probability of winning. From the perspectives of human beings, he stretched a little bit and I was surprised. I also thought I was very close to winning the match in the middle of the game, but that might not have been what AlphaGo was thinking. I was very excited, I could feel my heart thumping!”
Ke Jie, 9 Dan Professional, in the post-match press conference
“We’ve never seen any match in the past with this much scuffle. I was very surprised at the ability of Ke Jie 9-dan and the amount of preparation he puts in. His moves at the beginning were extraordinary and it appeared the match will be a close one but AlphaGo once again showed off its evolution.”
Hirofumi Ohashi, 6 Dan Professional and commentator from Japan
“AlphaGo showed the definition of ‘mind-blowing’ play today. When human artists start drawing landscapes, they keep drawing landscape no matter what happens during the process. However, AlphaGo can quickly switch from landscape to portrait. Similarly, human players have their own style of Go plays. However, AlphaGo has no fixed style and is so flexible.”
Kim Sung Yong, 9 Dan Professional and commentator from Japan
Ke Jie opened the game with a bold declaration by employing two of AlphaGo's favorite moves. The first of these, the 3-3 corner enclosure introduced to opening theory by the legendary players Go Seigen and Kitani Minoru in the 1930s, saw frequent use for decades before falling out of favor in contemporary Go. However, it is now seeing a revival as Ke Jie and other players have begun experimenting with it in recent tournament games. After AlphaGo responded by securing its own corner with its favored two-space high extension, Ke Jie leapt into the upper-left corner with a 3-3 invasion. Previously dismissed as unplayable, this move has experienced a sudden surge in popularity after AlphaGo introduced several new variations in its recent series of 60 games.
A rare variation of the 3-3 invasion joseki followed, at the end of which AlphaGo played a very interesting novelty: instead of resolving the ladder with a direct capture or the usual knight's move, it played on a grand scale with the large knight's move of 24. Fan Hui believes that AlphaGo was telling us its own unique philosophy: "AlphaGo's way is not to make territory here or there, but to place every stone in a position where it will be most useful. This is the true theory of Go: not 'what do I want to build?', but rather 'how can I use every stone to its full potential?'"
An exciting interchange on the upper left side followed and Ke Jie came through in excellent form. Giving up the corner for the side, Black captured four of White's stones in a trade that AlphaGo evaluated as ideal for both players. Not for nothing is Ke Jie regarded as the best player in the world! With the approach at 49, Black challenged White's influence on the lower side, but White turned lightly aside with the peep and cut at 50 and 54. These moves aimed not at a direct follow-up, but at subtly maximizing the potential and future initiative in the area. Although AlphaGo would have preferred the one-space jump to emphasize the center, Ke Jie responded by tightly gripping White's four stones at 51, maintaining maximum local control. With 55, a sharp probe that soon spurred Black to trade the lower side for the lower-left corner, Ke Jie made a choice that set the direction for the rest of the game. After Black lived in the corner, giving White an iron wall outside in compensation, Ke Jie resolutely discarded his stones on the lower side to gain a strong shape and initiative to return to the top.
Now behind in the balance of territory, Ke Jie was obliged to make the most of the upper side, and attempted to do so on a grand scale with the ambitious two-space jump of 97. AlphaGo's collected response at 98 forced Ke Jie to cut off the single white stone with 99, a decisive move that initiated the last major exchange of the game. Heading into the endgame, Ke Jie responded with vigour, but AlphaGo emerged with a modest but secure lead, ultimately winning by a half point.
We hope the innovations we have seen today are only the first of many, and look forward to Go players around the world analysing these moves as well as trying them out in their own games.
“Ahead of today, I studied and prepared quite a lot. At the very beginning, I made fierce, targeted moves, two 3-3 moves. I copied some moves that AlphaGo liked to use in past games. AlphaGo also made some unexpected moves as well. I was deeply impressed. Also, there was a cut that quite shocked me, because it was a move that would never happen in a human-to-human Go match. But, afterwards I analyzed the move and I found that it was very good. It is one move with two or even more purposes. We call it one stone, two birds. I am quite convinced by this loss that AlphaGo is really strong. From AlphaGo there are lots of things that are worthwhile learning and exploring. The influence of AlphaGo has been widespread. We should explore our minds and expand our thinking."
Ke Jie, 9 Dan Professional, in the post-match press conference
"Huge respect to Ke Jie for an amazing, great game. It was so close, and an exciting game for everyone. Huge respect to Ke Jie for pushing AG to its limits! Go is an amazing subject with almost limitless possibilities. I see AlphaGo as a tool for Go players and the Go community to explore the truth of Go, and to find out more. I hope that the Go players have enjoyed the last year, and I hope that it's contributed to our understanding of this amazing game."
Demis Hassabis, CEO of DeepMind, in the post-match press conference
“Ke Jie started with moves that he had learned from the Master series of games earlier this year — adding those new moves to his repertoire. Ke Jie used the lower board invasion point similar to AlphaGo in the Masters games, and this was a move that was unheard of before then. Although this was one of the most difficult moves for us to understand, in the last month or players have been making their own translations and interpretations of it."
Michael Redmond, 9 Dan Professional
“Every move AlphaGo plays is surprising and is out of our imagination. We can’t read those kind of moves. Some of the moves that AlphaGo played are not based off our human studies. Those moves completely overthrow the basic knowledge of Go. After the game, taking time to analyse those moves is very helpful — AlphaGo is now a teacher for all of us.”
Stephanie Yin, 1 Dan Professional