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© 2019 Yuan Zhou

Using AlphaGo’s Enlarged Corner Enclosures

Yuan Zhou

Buy the full book at gobooks.com

AlphaGo’s tactic of making a two space rather than a traditional one space corner enclosure from a 3–4 point stone has become very popular among pro players. Zhou explains the significance of this tactic and the variations involved in using it. A large number of illustrative pro games are presented with commentary on the tactic and its consequences.

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). Zhou was the president of the University of Maryland Go Club, from which he earned a BS in Electrical Engineering, and became increasingly involved in AGA events, winning many go tournaments. Zhou was also elected to the AGA board of directors in 2005.

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 New Jersey Open, one of the biggest US tournaments, four times. Twice he has won the Maryland Open, another major tournament that attracts strong players. Zhou has placed in the top ten in the US Open many times, as well as in the North American Ing Masters Cup and the North American Fujitsu Qualifying Tournament. These tournaments involve the strongest North American go players and include pros. In Zhou’s go career, he has defeated pros many times, including four 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 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 (WAGC, Korea Prime Minister Cup, World Pair Go Championship, etc).

In 2009, Zhou represented USA in the 4th Korea Prime Minister Cup World Go Championship in Jeonju, Korea and finished in 5th 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 region. He has also published many go books with Slate & Shell (www.slateandshell.com) and SmartGo Books (gobooks.com). Zhou resides in Germantown, Maryland, USA. His website is at www.zhouyuan.com.

Copyright Page

(c) 2019 Yuan Zhou

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

Slate & Shell
www.slateandshell.com

Edited by William Cobb

Conversion to SmartGo Books by William Cobb

Table of Contents

Using AlphaGo’s Enlarged Corner Enclosures

About the Author

Copyright Page

Introduction

Attacking the Basic Shapes

Example Pro Games

Game 1: Lian Xiao vs Ke Jie

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

Game 2: Chen Yaoye vs Tang Weixing

Game 3: Shi Yue vs Jiang Weijie

Game 4: Ke Jie vs Kim Jiseok

Game 5: Park Junghwan vs Ke Jie

Game 6: Kim Seongjae vs Weon Seongjin

Game 7: Shi Yue vs Dang Yifei

Game 8: Gu Zihao vs Ke Jie

Game 9: Fan Tingyu vs Kim Jiseok

Game 10: Chen Qirui vs Jiang Weijie

Game 11: Ke Jie vs Liu Xing

Game 12: Jiang Weijie vs Lee Sedol

Game 13: Ke Jie vs Kim Jiseok

Game 14: Cho U vs Iyama Yuta

Game 15: Shi Yue vs Xie Erhao

Game 16: Gu Zihao vs Mi Yuting

Game 17: Shin Jinseo vs Ke Jie

Game 18: Fan Yunruo vs Gu Li

Game 19: Lian Xiao vs Zhou Ruiyang

Game 20: Lian Xiao vs Chen Yaoye

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Introduction

The most popular opening tactic that pros are adopting from AlphaGo [go players continue to refer to the other versions of this AI program as “AlphaGo”, including the latest which is actually “AlphaZero”] is the early 3–3 invasion that I discussed in a recent book, Playing AlphaGo’s Early 3–3 Invasion, which is available in print form from Amazon and also as a SmartGo e-book. The other quite popular opening tactic that pros are adopting from AlphaGo is the expanded corner enclosure from a 3–4 point stone. This tactic was also advocated by Go Seigen, but did not become popular until AlphaGo starting playing it regularly. The difference is that the slide or extension from the initial 3–4 point stone is two spaces instead of only one. Go Seigen argued that the traditional one space slide (or extension—the slide is more solid and has been much more popular) is too small so the small slide is slow in the opening. Even though it guarantees the corner territory, it is inefficient. It is better for the corner to be a little vulnerable than for it to be inefficient, especially at the beginning of the game, when outside potential is also very important.

Moreover, when the opponent begins attacking the traditional corner enclosure, as with contact moves at the letters in this diagram, Black’s corner group immediately becomes overconcentrated.

Move 1

Even if Black gets an ideal double wing structure as in this diagram, White 1 is an ideal invasion point for White, with excellent follow-up moves at A or B to reduce Black’s moyo.

The traditional, one space corner enclosure is simply inefficient.

One effort to improve the one space corner enclosure has been to extend rather than slide, as in this diagram.

Moves 1–9

However, this shape also has weaknesses. For example, if White peeps as in this diagram, when Black connects, White can make a ko for the corner. So the one space high extension does not really secure the corner for Black.

Moves 1–2

Alternatively, if Black protects the corner with this 2, White has sente moves at A and B to cause trouble for Black.

Moreover, White can attach at any of the lettered points to make Black overconcentrated.

If Black gets a double wing position with this one space high corner enclosure, it does provide the possibility of a much more effective large position. White does not have an easy way to deal with this shape.

AlphaGo plays both the two space slide and the two space high extension from the initial 3–4 stone. Of these, the two space high extension is by far the most popular among pros. It is important to recognize that the issue here is not just the points in the corner, but the situation on the whole board, that is, the corner position’s outside influence is also important. One of the most impressive qualities of AlphaGo is its intense focus on and awareness of the whole board at all times. In the case of the early 3–3 invasion this comes out in terms of the side on which the player whose 3–3 point was invaded decides to block. It also arises when the players decide where to play in taking sente to play away from the early invasion. I pointed out in the earlier book how often players do not simply extend on the side on which the outside stones appear after the invasion. With the corner enclosure, the issue of the whole board situation is more complicated: the corner has a larger potential for territory than in the case of the 3–3 invasion and it also has a larger outside potential.

We will see that, because of this larger potential in both senses, both players sometimes avoid playing near a corner with a two space extension or slide for a surprisingly long time in a game (though it is now becoming more common for the other player to approach the two space high corner enclosure very early). This is another way in which this tactic is quite different from the early 3–3 invasion, which induces immediate follow-ups. The issue is when to decide between solidifying the corner and developing the outside potential. That depends, of course, on how the rest of the game is developing. In other words, the need for paying attention to the whole board is made obvious with this tactic.

Of course, the two space slide or extension is potentially more complicated to deal with than the one space positions. This is part of the reason some players are reluctant to play this way. Nevertheless, there can be no question about the fact that the traditional corner enclosure is slow.

I note that weaker players do not seem to be playing either of these tactics endorsed by AlphaGo very often. The tactics are not guaranteed game winners, of course, but a good case can be made for the claim that they make possible a better overall situation for you at the beginning of the game than the more traditional alternatives.

Let’s now look at how these positions work out in actual pro games.

Attacking the Basic Shapes

The first thing to be aware of is how these two space corner enclosures can be attacked.

The traditional one space slide from a 3–4 point stone creates a solid corner. The two space slide from a 3–4 point stone is more solid than the two space high extension, but it is still vulnerable to attack.

The two space slide (large knight’s move) has several vulnerable points. On the one hand, any attachment by White at one of the letters in this diagram would be good for Black.

Moves 1–2

For example, this exchange is obviously a loss for White.

However, because of the larger shape, there is more aji inside Black’s position at E, F, and G.

For example, this sequence could occur. However, depending on the overall situation, Black could be happy with this result.

Move 1

If Black tries the double wing formation based on the two space slide, White 1 is an excellent reducing move. This is part of the reason the two space high extension has become more popular than the large knight’s move.

Of course, the corner is big and open after the two space high extension so there is still aji in the corner. This may not be an immediate issue so it depends on who chooses to use sente to play in this area and when they do so.

Move 1

The first thing to see is that with the two space high extension, this White 1 is an excellent attacking point, threatening to play inside. It is not easy for Black to respond.

Moves 1–5

If Black does not respond locally, White has this kind of follow-up moves. Black has obvious problems here. Black lacks a good way to avoid this sort of harassment in this situation.

If Black responds with this 2, White can still create a difficult situation for Black with 3.

If Black tries to defend like this, becomes oddly placed. The situation remains complicated and difficult. Locally, Black does not have a good response to this White 1. In fact, we will see that Black usually plays elsewhere after this 1.

In the full book, this analysis of the large enclosure continues.

Example Pro Games

Owing to the ambiguous nature of the potential of the two space corner enclosure, although it is usually approached early by the opponent nowadays, it is not uncommon for the local situation to be left relatively undeveloped until well into the game, when the issue of the value of the corner versus the value of outside development can be better assessed. Sometimes it is used as a useful place for ko threats by the opponent. This makes showing how it works out in actual games more complicated than was the case with the early 3–3 point invasion. The whole board situations are more complicated when examining the two space corner enclosure. Playing through the games is really the best way to understand this tactic. That would be much more useful than the brief overviews I can provide here. Happily the complete game records are included in this SmartGo ebook. I encourage you to study them.

Game 1

This is the second game of the finals match in the Chinese Longxing (J: Ryusei) tournament, played on June 6, 2018. Lian Xiao 9p is White and won this game. Ke Jie 9p, whom many believe is the best human player in the world, is Black. Ke Jie lost this game but took the title by a score of 2–1.

Moves 1–7

Ke Jie is famous for using AlphaGo tactics, and he does not disappoint in the opening of this game. First he plays on a 3–3 point with his second move and then he makes a two space high extension from a 3–4 point stone. His fourth move is an early 3–3 invasion. All these are AlphaGo moves.

Moves 8–17

White blocks this way with 8 because of Black’s increased potential at the top with being high. Black abandons the joseki in the upper left to play 15 and 17 to pay more attention to the whole board, which is common today. Local situations are evaluated in terms of the whole board.

Moves 18–24

White’s getting the upper left corner is of course locally good for White. Black can play this way because of the significance of his overall position. Ke Jie is not afraid of this new way of thinking in go.

Moves 25–29

Black 25 and 29 also show Ke Jie’s focus on the whole board situation. He is reducing the value of White’s thickness to the left of Black 29. 29 prevents White A, which is the best attack on this two space high extension. Locally, White can invade and live in the top right, which could make 29 overconcentrated, but the timing of that is very tricky: Black would become strong and thick on the outside. Black is thinking of the whole board.

Moves 30–31

So Black ignores White’s attack with 30 and expands his moyo with 31.

Moves 32–33

Note that Black must not allow the three stones in the bottom left to become a loss. This style of play is not easy. When White expands with 32, Black 33 aims to start a fight here.

Moves 34–35

White helps one of stones with 34 and Black jumps out with 35, cutting off the connection between White’s two stones and initiating chaotic, middle game fighting. This lack of a systematic opening is typical of post-AlphaGo play. Early fighting shapes the game.

Moves 36–41

Now the game moves into the complicated middle game. With the modern big komi, this sort of complicated game is actually good for Black. A peaceful game is likely to work better for White. A complicated game gives Black a better chance of overcoming the burden of the big komi.

The large corner enclosure makes the game more complicated. So Black must try to make the most of his initial sente advantage. AlphaGo has shown that today’s big komi requires a new strategy for Black. This makes things more difficult for weaker players.

Moves 1–200
133 at 91; ko: 136, 143, 152, 175, 178, 181, 184, 187, 190, 193, 196, 199

Here’s the entire game. White wins by resignation.