Eternal Life

Sometimes a game played under Japanese rules ends in Eternal Life (chosei, 長生), a certain repetitive situation. Here some examples. See also Triple Ko and Quadruple Ko.

Games ending with "No Result" because of an Eternal Life cycle:

Black	White	Date	SGF
Kurotaki Masanori	Kono Mitsuki	1989-01-28	sgf	(insei)
Rin Kaiho	Komatsu Hideki	1993-09-02	sgf
Takizawa Yuta	Tanaka Yasunori	2003-09-28	sgf	(amateur)
Uchida Shuhei	O Meien	2009-09-14	sgf
An Sungjoon	Choi Cheolhan	2013-06-29	sgf

Additions and corrections are welcome. Mail to aeb@cwi.nl

Kurotaki Masanori vs Kono Mitsuki

sgf

Here Black 4 is forced, for if White plays there, Black is dead. After White 7 the situation is the same as after White 3. A repetition with period 4.

But Black 2 was a mistake, and he should have connected instead:

variation with or .

Rin Kaiho vs Komatsu Hideki

sgf

A different situation, involving an additional ko. The Black group on the left doesn't have eyes, and Black has to kill White before he is killed himself. White can sacrifice two stones as a ko threat, and then Black can sacrifice two stones as a ko threat, and the situation repeats (with period 6). On the other hand, instead of 5 at B1, Black could have played 5 at B4:

variation

and since White has no threats, Black would have won. (No threats, that is to say, no threats other than a pass. There are no further points, and Black is 0.5 points ahead. If this is the end of the game, and the remaining four White stones are just declared dead, he wins. If Black actually captures the four White stones, he loses by 0.5 point. So the precise rules about the end of a game play a role here.)