approach liberty


The approach liberties of a group is the minimal number of the attacker's excess approach plays necessary for removal. [1]

approach liberties  

The white semeai string has 2 while the black semeai string has 3 approach liberties.

Timm(10k): Hi Robert. I do not understand this page. According to the definition given, I feel like black has one approach liberty and white doesn't have any. Thus the black group would have two primary and one approach liberties. Am I wrong ?

Robert Jasiek: You seem to think that "number of liberties to be played = physical liberties + approach liberties". I use "approach liberties" in the sense "number of liberties to be played". However, the definition of term above is more refined. In an alternating move-sequence, in which the attacker approaches a string and the defender tries to delay the attacker's approach, incidents like capture-recapture or almostfill-capture can occur before all physical liberties of the studied string can be filled. Therefore, one must study the excess number of attacker minus defender plays. Both players optimise numbers of plays, so the definition also speaks of "mininal". An "extra approach move" is not the same concept as an "approach liberty"! Maybe this is the cause of your confusion.

[1] The definition follows that one in the book Capturing Races 1 by Robert Jasiek.

approach liberty last edited by on April 25, 2018 - 20:56
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