Odd eyed seki

  Difficulty: Advanced   Keywords: Rules, Theory

In a seki where the enclosed points (territory) are unequally distributed, the score varies over rulesets.


It does not depend on the choice of territory or area scoring. What matters is whether eyes in seki are considered special or not.

Under Japanese and Korean rules, they don`t count as ordinary points do. In AGA, Chinese, French and New Zealand rules on the other hand, there is no such exception.


Whilst territory and area scoring usually differ by only one or zero moku, treatment of eyes in seki can result in a significantly greater difference.



[Diagram]

Odd eyed seki



In this seki, White encloses six points, but Black just one. x is neutral (shared) under all rules.
There shall be no komi nor prisoners.


So, the five circlemarked points decide the game:


 points in seki  ||       Area scoring              |       Territory scoring
   treated as    ||          gives                  |             gives
 ================||=================================|==================================
                 ||  (e. g. Chinese rules)          |   (not commonly used)
                 ||                                 |
 not special     ||  Black: 39.5                    |  Black: 11.0
                 ||       = 39 points + 0.5 shared  |       = 11 territory + 0 captives
                 ||  White: 41.5                    |  White: 13.0
                 ||       = 41 points + 0.5 shared  |       = 13 territory + 0 captives
                 ||                                 |
                 ||  -> W wins by 2 moku            |  -> W wins by 2 moku
 ----------------||---------------------------------|----------------------------------
                 || (this case doesn`t make sense)  |  (e. g. Japanese rules)
                 ||                                 |
 invalid         ||         XXXX                    |  Black: 10.0
                 ||                                 |       = 10 territory + 0 captives
                 ||         XXXX                    |  White:  7.0
                 ||                                 |       =  7 territory + 0 captives
                 ||                                 |
                 ||                                 |  -> B wins by 3 moku




Note that the asymmetry examined here concerns seki territory only. Sometimes, another asymmetry is interesting, which is the area? tally of the seki (territory + stones). About that, see 10000 Year Ko and seki collapse.


This is a copy of the living page "Odd eyed seki" at Sensei's Library.
(OC) 2007 the Authors, published under the OpenContent License V1.0.
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