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CapturingRace

 

No Eye versus No Eye Capturing Race
Path: EyesCollection   · Prev: EyeVersusNoEyeCapturingRace   · Next: EyeStealingTesuji
    Keywords: Tactics

When both parties involved in the capturing race (semeai) have no eye, the fight is calculated as follows.

1. Fewer than Two Inside Liberties

If there is one or no inside liberty, there is no possibility of seki: one of the groups will die. It is the one with less outside liberties. If both groups have an equal number of outside liberties, the one who has sente wins the fight.

In a formula:

OL1 > OL2 => 2 dies, else sente kills

Example 1

[Diagram]
No eye - no eye - no inside liberties

There are 4 outside liberties for White (marked a) and 4 for Black (marked b). There is no inside liberty.

The player who has sente kills the other.



Example 2

[Diagram]
No eye - no eye - 1 inside liberty

There are 4 outside liberties for White (marked a) and 4 for Black (marked b). The circled point is the only inside liberty.

The player who has sente kills the other.


[Diagram]
Demonstration

Black goes first to give atari at 7 and capture at 9. Of course, White should realize this and keep 2, 4, 6 and 8 in reserve as ko-threats.



Example 3

[Diagram]
No eye - no eye - 1 inside liberty

There are 5 outside liberties for White (marked a): the utmost left is an approach move and as such is also counted as a liberty. Still 4 outside liberties for Black (marked b). The circled point is the only inside liberty.

Black is dead.


[Diagram]
Demonstration

So, Black should keep 1 to 9 in reserve as ko-threats.



2. Two or More Inside Liberties

If there are two or more inside liberties, seki is possible. The group with more outside liberties is alive. The threshold for the other group to live in seki is:

OL1 + 1 = OL2 + IL

If the numbers are equal, then sente decides whether the defender can make seki or the attacker can kill. If one number is larger, the status is settled as seki or death. The oddity in this formula is that the attacker counts one of the inside liberties for himself.


See also the pages in the Eyes Collection.



Path: EyesCollection   · Prev: EyeVersusNoEyeCapturingRace   · Next: EyeStealingTesuji
This is a copy of the living page "No Eye versus No Eye Capturing Race" at Sensei's Library.
(OC) 2004 the Authors, published under the OpenContent License V1.0.