Suicide

  Difficulty: Advanced   Keywords: Tactics, Rules

Chinese: 自杀 (zi4 sha1)
Japanese: 自殺 (jisatsu)
Korean:

[Diagram]
Suicide  

The term suicide (or self-capture) refers to a move which is played such that the stone just placed has no liberties, but all opposing stones still have.

Suicides are forbidden under most rulesets there are however different rulesets that do allow them.

For the vast majority of the cases, even if suicide is allowed, it only causes a loss of stones and/or points to oneself. However, in rare cases, suicide of more than one stone can be a useful move. further on in this aricle there are examples of positions where suicide (if allowed) can be useful.


Table of contents

Suicide and the rules of go

Suicide moves are forbidden under Japanese rules and Chinese rules

Suicides are allowed in some other rulesets, such as Ing rules, New Zealand rules and Tromp-Taylor rules but only when it is suicide of more than one stone.

(how about the aga, egf and other rule sets)

Suicide of a single stone?

A suicide of one stone does not change the position on the board, and therefore may be forbidden or equivalent to a pass stone, depending on the ruleset [1].

Suicide and counting.

(-- a bit about counting and suicide--)

Suicide Incident in a professional game

[Diagram]
Cho Hunhyeon 9d v. Choi Cheolhan 5d. Kisung tournament.  

A very unusual incident occurred in the first round of the 15th Korean Kiseong tournament (2003-10-02). Cho Hunhyun 9p was forced to lose a game (against Choi Cheolhan) because of an illegal move. You can see the game record at the time of the infraction at [ext] go4go. Cho obviously intended to take the ko at a in the lower left corner when he made an illegal one stone suicide play instead (on the lower edge). Such a mistake is extremely rare in professional tournaments.

For more on this see: [ext] Suicide is painful:


Positions with a good suicide

For the vast majority of the cases, even if suicide is allowed, it only causes a loss of stones and/or points to oneself.

However, in rare cases, suicide of more than one stone can be a useful move. The rest of this article gives examples of how suicide can be useful.

Suicide as ko threat

[Diagram]
Suicide as a ko threat  

The simplest, and best known, situation where suicide can make a difference is as a ko threat. In this position, the black group is alive. However, if White is allowed to play the suicide move of W1, taking three white stones off the board, Black will have to come back at the same point to make two eyes. If suicide is forbidden, then White has no ko threat here.


Suicide creates liberties

[Diagram]
A capturing race: B to move.  
[Diagram]
if suicides are prohibited..  

But sometimes suicide also makes a difference for the outcome of a capturing race. In this diagram, if White is not allowed to play suicide, she is dead. There is no way for White to avoid that: Black first fills up two liberties with B1 to B5, then captures at B7, resulting in the next diagram.

[Diagram]
Black wins  

Playing at W8 to prevent Black from getting two eyes will not help White.

Black plays atari at B9, and White is dead.



Note that these diagrams are just used to show that White is indeed dead - Black need not hurry to take the stones off the board.

...but, if suicides were permitted....

[Diagram]
Suicide permitted  

If suicide is allowed, White does have a resource in this situation. She can play the suicide move of W2. The result is shown in the next diagram.

[Diagram]
White lives in seki  

After W6, the position is a seki; neither player can make any useful move - so this time, White lives. If Black plays B3 or B5 at W4 or W6 or a, the position is still seki, each player having one eye and no external liberties.


No content

Links to other benificial suicides

(to do) * *

[Diagram]
 

See also


[1] The status of self-capture of a single stone in various rulesets which allow suicide is as follows:

  • Ing rules explicitly forbid suicide of a single stone.
  • Tromp-Taylor rules have the positional superko rule, so suicide of a single stone is not allowed.
  • New Zealand rules have only situational superko, so suicide of a single stone is usually allowed. When allowed, it is equivalent to passing. It is not allowed after a pass.

Links


Suicide last edited by 192.75.48.150 on April 17, 2014 - 23:57
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