Double Sente is Relative

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    Keywords: EndGame, Strategy

Bill Spight:

Double sente is relative. It depends on what else is on the board. Every Go position can be categorized as sente, gote, or ambiguous. Any play, whether a sente or gote in the abstract, can be a double sente if the reply when either player makes the first play is larger than anything else on the board. Usually, double sente are played as soon as they arise.


Example 1

Example (outer stones alive):

[Diagram]

"Double" sente

This appears in Kano's Yose Dictionary. He says that it is a double sente, but that Black's play has more "necessity". (It threatens White's group.)



Actually, this is a seven-point sente for Black. If Black plays first, we get

[Diagram]

Black sente

which has a local score of 5.



If White plays first, we get

[Diagram]

White reverse sente

which has a local count of -2 (2 points for White).



Later this is White's sente.

[Diagram]

White sente



And even later, this is Black's sente.

[Diagram]

Black sente (2)

The local score is -2.



After White's hane, Black's reverse sente is worth three points.

[Diagram]

Black reverse sente

The local score is 1.



The original position is a seven-point sente for Black. However, when the ambient temperature drops below 3 points, it is double sente (as a rule).


Example 2

Beware of so-called double sente. For instance, Kano's "Yose Dictionary" gives the following as a two-point double sente (p.30).

[Diagram]

Double sente???

[Diagram]

Black sente???



After the exchange of B1 - W2, White has a one-point sente sequence with W4 - B7. The score is +5 (for Black).

[Diagram]

White sente???



After the exchange of W1 - B2, Black has a one-point sente sequence with B4 - W7. The score is +3.

If this is a double sente, then whoever plays it picks up two points (by comparison) for free.

But do not be misled. This is actually a gote play, worth about 3 2/3 points (miai value).

[Diagram]

Black's follower



After B1, B3 is a gote play worth about 2 1/4 points. If there are bigger plays on the board, White is unlikely to respond to B1.

[Diagram]

White's follower



After W1, W3 is worth slightly more than 3 points.

So if there are plays worth between about 3 2/3 and 3 points elsewhere, Black is unlikely to respond to W1.

This is a middling gote play. Do not think of it as a double sente.

Also see How Big is the 6 point Double Sente


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