Sunday Problem #83

Published 2 Jan 2022 by antti (last edited 15 Feb 2022)

This is an interesting problem from the Celestial Dragon Diagrams (Tenryū-Zu). The correct solution may change depending on whether this problem is treated as a life-and-death problem or as an endgame problem.

Black to play.

Life-and-death solution
Black can live unconditionally with 1. White has various possible responses, but 2–7 gives him the most territorial profit.
Ultimately, White has eight points to Black’s three, so the net score is five points for White (W+5).
7 at a
Endgame solution
Territorially, it is better for Black to fight with 1 here. White resists with 2 and on, and, after black 7 . . .
Endgame solution (contd.)
. . . White recaptures with 8, finally setting up a kō for the black group with 10.
Assuming black then takes the kō, we have the same relative number of moves played as in the L&D solution. Black is then one move away from living with a net score of B+10, and two moves away from dying with a net score of W+23. On average, this means a net score of W+1 at the time Black captures the kō, so four points better for Black than the L&D solution.

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