Blind eye

  Difficulty: Intermediate   Keywords: Life & Death, Theory

A blind eye of a chain C is a term proposed by PJTraill for use in the context of Benson's Definition of Unconditional Life for an enclosed region that fails to be vital for C (an eye of C) because not all vacant points in it are adjacent to the C.

Benson's theorem states that a set S of chains is pass-alive (cannot be capture by the opponent however many moves in a row he has) if and only if each chain in S has two eyes enclosed by S; an eye of a chain is a maximal connected collection of empty points and opposing stones such that every vacant point (and, if suicide is allowed, every opposing stone) in it is adjacent to C.

[Diagram]

Blind eyes

For the chains marked black+cross:

f marks a false eye that is not blind

g is false and blind

b marks a blind eye

r marks a real eye


See also


Blind eye last edited by PJTraill on September 9, 2018 - 22:43
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