Sente Ko

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1) An extreme form of one-sided (hanami) ko fight. The capture by one of the players, Black say, has such a large potential follow-up that White must treat it as a sente play.

Such a ko position, at a given stage of the game so that it really is a sente ko, will not give rise to an extended ko fight. But it is possible sometimes for White to capture once, even in such a fight. The reason is that Black must find some ko threat. White therefore has a chance to make Black use one threat.

2) A ko such that taking the ko is sente for one player. Here is a small example.

[Diagram]

Small sente ko

(N. B. By convention, stones adjacent to empty space are alive.)

If White takes the ko she raises the local temperature (from 1/3 to 7/9) by threatening to take again.

But see Ambiguous Ko.

Another example:

[Diagram]

Example 2

If White takes the ko she raises the local temperature from 1 2/3 to 2 1/3.

This kind of sente ko is fairly common. They do favor the player with sente, but the sente threat is not so large that they are unfightable, as a rule.

3) A ko such that winning it is sente for one player. Here is an example.

[Diagram]

Sente ko (iii)

If Black fills, the White group dies. But if White takes and wins the ko,

[Diagram]

Sente ko (iii-a)

White threatens to kill the Black group with White 1. This is worth 16 1/3 points, miai, hotter than the original ko position, in which a play is worth only 12 2/3 points.

[Diagram]

Sente ko (iii-b)

If White wins the ko in sente, later Black 1 is a 1 2/3 point sente ko, where taking the ko is sente.


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This is a copy of the living page "Sente Ko" at Sensei's Library.
(OC) 2005 the Authors, published under the OpenContent License V1.0.
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