7x7 Article by J. Davies

  Difficulty: Advanced   Keywords: Rules, Theory, Books & Publications

Willemien This is the article about 7x7Go that was published in the American GO Journal (vol. 29, number 3,Summer '95) pages 11 till 13

The only difference being the layout, links and some diagrams are split do to the 10 move restriction in Sensei's library

The article republished here with kind permission from the American Go Association

There is an SGF file about the 7x7 game but at [ext] http://www.cwi.nl/~tromp/java/go/7x7.sgf but this file does differ from the article below.

One of the more stricking differences is that the SGF file uses the New Zealand rules while this article uses the Japanese rules And the SGFfile has a diffenend best move for move Black B11 in Diagram 14-2 see BQM442 where I posted it as problem

Discussion please at the end of this article. (To keep the article just as it is) excuses for the many versions it took to get it in the right state.


7 x 7 Go

by James Davies

On a 7x7 board, Go becomes challenging for even the strongest human players. The challenge (find the best moves for both sides) was taken up in 1977 by a group of Japanese amateurs including Kiga Yasuo?, Nebashi Teruichi?, Noro Natsuo? and Yamashita Isao?. In 1989, with some professional help from Kudo Norio and Nakayama Noriyuki, they reached the conclusion that Black wins by nine points. What follows is a tip-of-the-iceberg summary of the evidence. It should be added that the analysis is still somewhat tentative, and future discoveries may lead to further revisions.

[Diagram]

Diagram 1

On a 7x7 board, Black's best opening is pretty certainly in the center at 1 and white should reply in contact at 2. After Black 3. White can flip a coin to choose between the cross-cut at a and the hane at b.


[Diagram]

Diagram 2(1-9)

Here is one sequence developing from the cross-cut at White 1 that leads to a nine point win. Note the bamboo joint at Black 10. This is perhaps the only move for which Black has any choice, the other options being Black 13 or 14. White's options are alse limited to the timing of White 13

[Diagram]

Diagram 2(10-17)


[Diagram]

Diagram 3

Let's move on to White's hane at 1, which leads to many more correct variations. Black should extend at 2, after which White has another coin-flip: heads for a, tails for b.


[Diagram]

Diagram 4

White 1 is simplest. after 2 and 3, it is Black's turn to flip a coin to choose a or b. whichever of these points Black takes, White will take the other. Diagrams 5 and 6 show both variations.


[Diagram]

Diagram 5 (1-9)

The key move in this sequence is White 10. If Black plays 11 at 12, White replies at a and has a good ko threat at b. The details are a bit tricky, to say the least, but Black cannot do better than Diagram 5, winning by nine points

[Diagram]

Diagram 5 (10-12)


[Diagram]

Diagram 6 (1-10)

This sequence also wins by nine points. The apparent underplay at Black 5 is the critical move.

[Diagram]

Diagram 6 (11-18)


[Diagram]

Diagram 7

If Black extends to 1, White replies with 2 and 4, White has enough ko threats, starting at a, to win the ko if Black tries to fight it.


[Diagram]

Diagram 8

We now come to White 1, a triple hane opens the gates to a flood of variations. After Black 2 and White 3, Black has four equally good continuations, marked a to d. We'll sample all of them in a moment, but first let's mention one temptation that Black must resist


[Diagram]

Diagram 9

Black should not give atari at 1. After White 2 and 4, Black cannot win by nine points. Readers who doubt this should try and see for themselves.


[Diagram]

Diagram 10 (1-9)

Here is one correct continuation from Diagram 8

[Diagram]

Diagram 10 (10-13)


[Diagram]

Diagram 11 (1-9)

Here's another. White 8 at 9 is also playable.

[Diagram]

Diagram 11 (10-12)


[Diagram]

Diagram 12 (1-9)

Here is another following from White 2 in Diagram 11

[Diagram]

Diagram 12 (10-15)


[Diagram]

Diagram 13 (1-10)

Another variation, featuring sacrifice tactics:

[Diagram]

Diagram 13 (11-20)

[Diagram]

Diagram13 (21-23)


[Diagram]

Diagram 14 (1-8)

Yet another variation, and this by no means exhausts the correct lines of play. Let's stop here, however to note one final point.

[Diagram]

Diagram 14 (9-14)


[Diagram]

Diagram 15 (1-10)

The correct variations so far have been ecumenically correct under all sets of rules. You may think you have seen enough already for a board of this size, but under AGA rules,ING rules and Chinese rules, the number of correct variations increases still further, because eight-point wins promote to nine points when Black gets the last move. For example Black 1, which wins by only eight points under Japanese rules and Korean rules wins by nine under these other rule systems. White ends in control of 20 points(occupied or surrounded) to Black's 29.

It could be argued that Black has not really played well in Diagram 15, because he needs an extra stone to get the same result. This argument may be worth considering when different sets or rules are compared.

[Diagram]

Diagram 15 (11-19)



Discussion

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