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Eternal Life
Path: LifeAndDeath   · Prev: DoorGroup   · Next: ApproachingALifeAndDeathProblemTheRightWay
Path: SecondCourseOnKo   · Prev: BentFourInTheCornerIsDead   · Next: RepeatingPositions

    Keywords: Ko, Rules

Chinese: 长生
Japanese: Chosei

Eternal life is yet another situation where a void game (no result: neither player wins, but neither player loses) can occur, under rulesets which permit such a thing. Several special rules, such as superko and the Ing Ko Rule, forbid the recurring sequence to occur.

However, eternal life is so rare in games that if one occurs, a Chinese Go text says that:

  You should buy fish, vegetables, meat and wine
  And have a good party to celebrate yourself

Of course, it's an exaggeration...

Example

[Diagram]
Eternal life

This is the situation to begin with.


[Diagram]
Eternal life

B1 begins by sacrificing two stones (to prevent the formation of bulky five)...


[Diagram]
Eternal life

B3 takes back two white stones...


[Diagram]
Eternal life

White makes a throw in at W4 to destroy the eye, and the cycle repeats itself when B5 sacrifices two stones again.



White has the option of making seki:

[Diagram]
Seki



Q: But suppose White needs to kill Black in order to win, and Black would never let go of his group, then eternal life occurs.

A: Strictly speaking the position after White 1 in the Seki diagram is not seki, but a hyperactive position. However, when it is correct to make the play, it will almost always become seki.


There was some excitement about this thirty years ago when a variation of the kado joseki played in a title game Sakata - Yamabe could have led to chosei.


SL material

Kanazawa Problem 85

External references

[ext] http://www-2.cs.cmu.edu/~wjh/go/rules/Japanese.html


[Diagram]
Rin Kaiho vs. Komatsu Hideki

Warp: In the game 2 of the 49th Honinbo league between Rin Kaiho (black) and Komatsu Hideki, played on 1993-09-02, a very curious eternal life variant involving a ko happened, which resulted in the game being voided. I think it was called an "eternal ko". The position leading to this happened in the lower left corner of the board, shown in the diagram (it's black's turn).


[Diagram]
Eternal ko

Black captures the ko with B1. White doesn't have any good ko-threat elsewhere other than at W2, which naturally forces black to capture at B3.


[Diagram]
Eternal ko

Now, after white captures the ko with W4, black doesn't have any other good ko-threat besides B5, which forces white to capture at W6. After this black captures the ko again and the position repeats.

Instead of W6 white could capture the marked black stone but that would result in a ko which white cannot possibly win (when black captures the marked white stone) so it would not help white to do that.

The game was declared void.



Authors



Path: LifeAndDeath   · Prev: DoorGroup   · Next: ApproachingALifeAndDeathProblemTheRightWay
Path: SecondCourseOnKo   · Prev: BentFourInTheCornerIsDead   · Next: RepeatingPositions

This is a copy of the living page "Eternal Life" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.