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© 2017 Slate & Shell

AlphaGo vs. Ke Jie

Yuan Zhou

Buy the full book at gobooks.com

The match between AlphaGo and Ke Jie 9P was the last time a human played the computer program. Yuan Zhou gives a thorough and insightful analysis of the three games in the match and reflects on the significance of AlphaGo for the go community.

About the Author

Yuan Zhou (American Go Association 7 dan) was born in Tianjin, China. Tianjin is a major city in the northern part of China, near Beijing. His father taught him to play go at the age of six and a year later he won the Tanggu District Junior Go Championship. After this auspicious beginning, Zhou began professional go training while he was still seven years old. He was twice invited to represent Tianjin in the All China Prodigy Cup.

In 1989, Zhou immigrated to the USA, becoming a US citizen and joining the American Go Association (AGA). He earned a BS degree in electrical engineering at the Unversity of Maryland, where he was the president of the University Go Club. He also became increasingly involved in AGA events, winning many tournaments. Zhou was also elected to the AGA board of directors in 2005 and is currently president of the XYZ Go Club, an official AGA chapter.

Zhou is one of the top competitors on the American go scene, winning the Eastern US Open, one of the biggest US tournaments, in 1992. He also won the prestigious New Jersey Open, another of the biggest US tournaments, four times. Twice he won the Maryland Open, another major event that attracts strong players. These tournaments involve the strongest North American go amateurs as well as pros. In Zhou’s go career, he has defeated pros many times, including five times in even tournament games: Hak Soo Kim 6p in the 1996 Fujitsu, Xuefen Lin 1p in the 2001 Eastern Oza, Huiren Yang 1p in the 2009 and the 2014 North American Ing Masters, and Feng Yun 9p in the 2011 SAMG World Team Go US Team Qualifier. Zhou also won the US Pair Go Championship four times. Zhou represented the USA in international tournaments many times (World Amateur Go Championship, Korea Prime Minister Cup, World Pair Go Championships, etc.).

In 2009, Zhou represented the USA in the 4th Korea Prime Minister Cup World Go Championship in Jeonju, Korea, and finished in fifth place.

In addition to his competitive successes, Zhou has become a popular teacher and lecturer, frequently giving lectures and teaching lessons at various go clubs in the Eastern US regions well as on the internet. He has also published many go books with Slate & Shell and SmartGo E-Books (www.smartgo.com). Zhou resides in Germantown, Maryland. His website is at www.zhouyuan.com.

Copyright Page

(c) 2017 Yuan Zhou

All rights reserved. Reproduction in whole or in part is prohibited.

Slate & Shell
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Edited by William Cobb

Cover design by Laurie M. Crammond

Conversion to SmartGo Books by William Cobb

Table of Contents

AlphaGo vs. Ke Jie 9P

About the Author

Copyright Page

Introduction

Game 1:
Black: Ke Jie; White: AlphaGo

The chapters in gray are included only in the full book.

Game 2:
Black: AlphaGo; White: Ke Jie

Game 3:
Black: AlphaGo; White: Ke Jie

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About SmartGo Books

Introduction

The go-playing computer program AlphaGo has had a revolutionary impact on the world of go. Not only has it vastly increased the awareness of the game among the general population, especially in the West, it has also profoundly impacted the understanding of the game among regular players, including professionals. The clearest evidence of the latter impact is that a number of patterns of play that have been universally accepted as good or bad are now having to be re-evaluated. The games in this book illustrate some clear examples of this.

This three game match between AlphaGo and Ke Jie 9p, the young Chinese pro who is currently ranked as the number one player in the world, was likely the last time AlphaGo will actually play as the program has been retired. The AlphaGo that Ke Jie played was the third and final version of the program. The first was that which Fan Hui 2p, the reigning champion of Europe, played in October 2015, losing 0 to 5 with one hour of basic playing time. The second version was that used in the five game match with Lee Sedol 9p, which AlphaGo won 4–1, this time with two hours basic time. Lee’s victory in the fourth game of that match is the only game that AlphaGo has lost (although Lee should have won the fifth game (see my book AlphaGo vs. Lee Sedol: The Match that Changed the World of Go). The program was strengthened again after that match—earlier versions had some weaknesses and made some endgame mistakes. This final version was first used in the sixty game series AlphaGo played on the internet against different pros, winning every game with a time limit of thirty seconds per move, including the game with the legendary Nie Weiping 9p when the time was one minute per move. AlphaGo won that game by seven and a half points. In the three game match with Ke Jie, the basic time was increased to three hours. Ke Jie got into time trouble in every game, however, while AlphaGo used only half the time allowed.

Whether AlphaGo in this third version was truly unbeatable by human players will never be known for certain, but it is clear that the program became incredibly strong and in fact found numerous new ideas about what constitutes best play. In that regard, the program has to be seen as remarkably creative. This is not just in the case of life and death problems, in which the program probably is invincible, but with regard to whole board thinking and a number of common josekis. The program’s attention to the whole board at every play is one of its most impressive features, and a number of patterns that have been universally accepted as good or bad are having to be carefully re-examined in light of AlphaGo’s play, including some standard josekis that have been universally considered correct. It’s also interesting that some basic features of AlphaGo’s play were explicitly anticipated by Go Seigen, the go genius of the twentieth century.

In preparation for the match, Ke Jie played many games with top Chinese pros and of course studied the records of AlphaGo’s games. His playing style is very flexible and creative. Ke Jie’s strength is particularly impressive in the middlegame and endgame, where he often makes surprising and unexpected plays. Among the very top pros, he is not considered among the best at the opening. Nevertheless, his reading ability is phenomenal. It is rare for him to lose with the white stones.

After the match with Lee Sedol, Ke Jie was confident he could defeat AlphaGo. He felt that Lee had not played that well. However, after playing the final version of AlphaGo in the fast-play matches on the internet and studying the games of the final version, Ke became less confident, saying he thought he had a 50–50 chance of winning. At the least, Ke was able to be better prepared than Lee Sedol had been and had a longer basic time in the games. The prize money for this match was increased to one and a half million dollars, with a guarantee that Ke would get $300,000 even if he lost the match. Ke Jie also had the advantage of knowing about six months in advance that he would be playing this match.

Game 1
Black: Ke Jie; White: AlphaGo

Ke Jie won the nigiri for this first game and is playing Black. The Chinese rules are being followed, which means that dame count and the komi is seven and a half points. The basic time is three hours, with one minute periods of byoyomi. Ke Jie is normally a relatively fast player, but in these games, he plays much more slowly than AlphaGo and ends up in time pressure in every game.

Move 1

Ke Jie had determined from his studies that AlphaGo, which is very strong in the opening, leans toward a territorial style and likes to get solid territory with outside thickness. So he begins with a 3–4 point play, hoping for a relatively simple opening that would enable him to enter the part of the game where he is strongest with the game at least even.

Moves 2–3

Ke Jie’s second move on a 3–3 point is a very unusual opening pattern nowadays, although Sakata Eio played this way back in the mid 20th century when he was a top player. Black’s aim in this opening is to take solid territory before fighting in the open parts of the board. This is not unlike the new territorial style. (See my book The New Territorial Style, which is available from Amazon.)

Moves 4–5

AlphaGo also takes a 3–4 point with White 4.

Ke Jie then makes a large knight’s move corner enclosure. The more common small knight’s move enclosure was criticized by Go Seigen as inefficient and AlphaGo seems to agree. As a result the large knight’s move for a corner enclosure has become popular. Until very recently, pros consistently played the small enclosure.

Move 6

AlphaGo makes a high two-space extension with 6. This has not been considered a good play for White, because it makes it more difficult to defend the corner, as we will see later in the game. However, White is aiming at the outside with this move. One of the most striking aspects of AlphaGo is its ability to control the center.

Black’s next move may surprise you, although it is becoming popular.

Move 7

Black now invades the corner on the 3–3 point. Traditionial theory sees this as not good for Black: The complaint is that Black will get sealed in and White will have very powerful outside thickness. So this early invasion with 7 has been seen as a bad play.

However, in its series of games on the internet, AlphaGo frequently made this early invasion and still won the games. So now this early move is seen as definitely playable, which is a clear departure from traditional go theory. It is showing up in many pro and amateur games.

Moves 8–9

White makes the natural block with 8 on the side where it has the most territorial potential and Black naturally extends to 9.

As the next diagram shows, in the past, White would now hane at 1 in that diagram and the usual joseki would continue with Black ending with sente.

Variation: Good for White

This is a well-known joseki. Black ends with sente, which is some compensation for the fact that the local result here is much better for White. But Black only has about ten points in the corner, while White’s outside thickness, especially in the opening, is very powerful.

However, AlphaGo does not play this way as Black.

Variation: Good for Black

In the internet matches, AlphaGo as Black played away from the corner after White 5 and in the future played around Black 6, not playing the hane at Black 6 in the above diagram. This variation effectively erases the influence of White’s stones to the right. So Black takes the corner, but White’s outside stones are not a thickness—they are a group that Black can attack later. This is a revolutionary idea that is very efficient for Black. Ke Jie hopes to use this strategy against AlphaGo.

Move 10

In the game, AlphaGo does not follow the common joseki by playing 10 at White 1 in the two variation diagrams just above. Instead, it plays this 10, which is not a new move. It was popular with Takemiya Masaki as part of his moyo (or “cosmic”) style of play. So AlphaGo is confirming this center-oriented idea of Takemiya’s.

Moves 11–16

Ke Jie continues this way. Black does better in the corner by playing 11 and 13. White plays 14 so that when White double hanes with 16, it creates aji in the corner. White is thicker outside.

To understand what is going on, we need to compare the game sequence with the joseki in the next variation diagram.

Variation

White could also play this way, with 10 in the game at this White 1. However, most players actually prefer Black in this variation. The sente capture of White 3 is big and in the future Black A will be a good move. Black can also create aji in the corner with the descent to B. So White’s corner is not as big as it looks. Hence, AlphaGo does not play this way.

Variation

Now we can see that if Black had continued by playing an atari like Black 4 in the previous variation with Black 17 (Black 1 here), this would be the result. White gets a better corner and a taller thickness so this is better for White than for Black.

So Ke Jie does not play this way but instead cuts at A with 17.

Moves 17–21

The cut at Black 17 protects the corner and threatens to leave White with a group of stones that is not a thickness but a potential target for Black.

White plays atari with 18 and Black 19 forces White to connect at 20 and leaves a potential problem outside.

Black then makes the corner secure by capturing with 21.