[Welcome to Sensei's Library!]

StartingPoints
ReferenceSection
About


Aliases (info)
MoonshineKo

Paths
SecondCourseOnKo

Referenced by
Ko
Passing
MakraiRules
WhenFalseEyesAreEyes
PassFight
FalseEyeLife
BasicKoAnomalies

 

Moonshine Life
Path: SecondCourseOnKo   · Prev: PinwheelKo   · Next: GoResearchOnKo
    Keywords: Ko

What is the status of the white group in the upper left corner?

[Diagram]
Moonshine Life


  1. Dead. - one eye dies.
  2. Seki. - White cannot make two eyes but Black cannot kill, because White has infinitely many unremovable threats.
  3. Alive - the white stones cannot be captured, so the "eye" should be worth 1 point.
  4. No result - if Black insists on playing the ko, a triple ko occurs

-- Bass


This is the earliest known rules dispute, involving an ambiguous pronouncement by a Japanese monk called Nyobutsu. The status of the top left white group has been regarded differently over the centuries, and modern rulesets do not agree.

I took the liberty of moving this from the MoonlightLife page. Moonshine Life is the usual name for this.

-- Bill Spight


The full story by John Fairbairn: [ext] Nyobutsu's Judgement


[Diagram]
Moonshine Ko, 1

[Diagram]
Moonshine Ko, 2


It seems to me (HoverSink?) that of the four options listed, we only have to consider #4. Since Black can always insist on playing into the triple ko, the position must be treated according to whatever rules we happen to be using for complicated ko. If we used any other reasoning to come to a different conclusion, we would be forced to then change our ko rules in order to keep the game self-consistent.

So, by Japanese rules, W6 would probably result in a voided game. Using a superko rule, W6 would not even be allowed. This problem would then be like the eye shapes reducible to the bent four in the corner; White will eventually become exhausted of all external ko threats, and be powerless to stop Black from playing the ko and winning.

So, in other words, since I am much happier seeing groups dead than alive (so long as they aren't mine), I would probably call White dead.

-- HoverSink?


Bill: By Japanese rules Black waits until the suspension of play and, in hypothetical play to determine life and death, takes the moonshine ko. White cannot take it back except by a pass for it, and if White does so, Black captures White's group. So the group is dead.

It is true that White can cause problems in the hypothetical play by taking in the double ko seki, forcing a Black reply, and then passing for the ko Black took in the double ko seki. To protect himself Black must pass for the ko White took in the double ko seki, and does not have time to capture White's group in the top left corner. In theory, White can keep this up indefinitely. It is a known flaw in the Japanese '89 rules.



Path: SecondCourseOnKo   · Prev: PinwheelKo   · Next: GoResearchOnKo
This is a copy of the living page "Moonshine Life" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.