Ko threat in seki example

  Difficulty: Intermediate   Keywords: Ko
Black's threats?  

Let us consider this position as a source of ko threats.

First assume Black is to play. How many ko threats does Black have here?

Black can play B1-W2-B3-W4 as a long threat. Since W2 is atari, stopping there isn't good for a small ko. And for a large ko the threat of B1, to make six points, isn't interesting.

Note that Black neither gains nor loses points here.

Result - one more threat  

In the position left behind, B1-W2 is one more threat.

Now, with White to play.

White's threat  

W1-B2 is a clearcut threat.

Is therefore this position an example of a double ko threat? White has one threat here worth over 20 points. Black can get two lesser threats. In a small ko White will remove this double threat. Black can theoretically remove it, too (cf. slightly different example at unremovable ko threat). In a larger ko White will have no reason to remove the threat, and Black's plays to remove the threat may instead be gote.

This is therefore a more complex example for the remove double threats before you first capture the ko heuristic.

Ko threat in seki example last edited by Dieter on January 9, 2013 - 19:01
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