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Shape of the Week: Eternal Life
What is the shape of Eternal Life Go?
Eternal life is an extraordinary living shape in Go. It will cause a type of cycle, where the position of the board repeats. Under some rule sets, a game in which such a situation occurs can become void (no result: neither player wins, but neither player loses). Several special rules, such as super ko and the Ing Ko Rule, forbid the recurring sequence.
Why Endless Cycle?
First, the black cannot play at position B because if the black does, the White could play at A, and then the inner space becomes a bluky five. Even if black captures all of the white pieces inside, black will die. Therefore, to live, black has to play at position A. However, a cycle occurs as a result, over and over, and the game lasts forever.
Professional Games
Though rare, Eternal life does happen in professional games. There are three recorded professional games ended in a tie because of this shape.
The most recent one happened in the Korean professional Go League in 2013, by An Sungjoon and Choe Cheol-han. There was an eternal life shape in the upper left corner, and none of the players could yield, so the game ended in a tie.
Though recent Chinese Go rule use PSK, which prohibits a board play from repeating a position, regardless of whose turn it was when that position was first reached, in practice, referees and players prefer to no result when eternal life shape occurs.
Thought-provoking Problem - The True Eternal Life (tsumego)
In extreme situations, we could use the shape of eternal life to live, and here is a tsumego challenge! (Credit to Bilibili content creator 云小天1118)
There are two possible eternal life shapes in this special 7 x 7 board. But which one could help the white to live? (White first to live) Let’s play.
