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Seki
Difficulty: Beginner
Keywords: Life & Death, Go term
Seki means 'dual life'. It can be seen as a sort of symbiosis where two groups share liberties which neither of them can fill without dying.
Although in general a group needs two eyes to live, there are exceptions where groups of different colours, each with less than two eyes, keep a 'balance'. The simplest form of a seki is as shown in this diagram: the marked white and black groups have no eyes, and share two liberties at A and B. If either player plays on one of these points, his opponent will play the other and capture his group.
A slightly more complex variant is formed by the marked black and white groups. Both groups have one eye, and they share a liberty. Again if either player plays at A, the other one will capture his group.
The two white groups both have one eye. The black group has none, but shares a liberty with both of the white groups. Again no player can capture any stones of the other player, and the position is seki. {TakeNGive 11k: If i understand correctly, in Japanese Counting (territory scoring), neither Black nor White gets any points from the seki; but with Chinese Counting (area scoring), Black gets 2 points from the stones living in seki, while White gets 12 points from this seki (10 points from the stones living in seki plus 2 points from the eyes 'a' and 'b'). Right? unkx80: You are right.}
Hmm. I think that saying that he gets '10 points from the stones in the seki' can be misunderstood. With area scoring all alive stones on the board (+ territory) count as points. Stones involved in a seki are alive and thus count as points. That is not because they're in a seki, but because they are alive. In practice, under area scoring, there is no points from a 'balanced' (same number of eyes/liberties) seki either - if Black has 10 stones in the group and White only 2 then White has 8 stones (=points) somehwere else on the goban.
A final example of a seki. Black can capture the three white stones, but if he does, White will then come back at the point where the marked stone is. Black will then be left with a dead shape, so black will not do so. Instead, this position will remain until the end, and the three white stones live through a seki.
If you play using Japanese counting, as is usual in Europe and Japan, this is a position to watch out for. The Japanese rules say that there are no points counted in a seki, so Black cannot count 3 points for A and the marked white stone. Instead, after the game is over, during or after the filling of dames, Black should capture at A, and that way get at least one point out of the situation. This is also of importance in the position of the third diagram: The points A and B are not territory points in Japanese counting, but they are in Chinese counting (for example in a game using Ing rules). A final note: although neither side can 'win' a seki, a seki can be a source of ko threats - as long as the ko is larger than the seki.
Allow me to provide just one more interesting example on seki, but involving kos. Go figure. :-) --unkx80 A related shape can be found on the Double Ko page. See also Seki with eyes question. --MortenPahle (Discussion moved from False Eye page --unkx80) Proposal for seki: Defintion:
Addition:
(TapaniRaiko: The proposal is not enough, as these two examples show. I saw an example where 35x35 board was filled with small groups all living in a single seki.)
This is a copy of the living page "Seki" at Sensei's Library. (C) the Authors, published under the OpenContent License V1.0. |