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Double Sente is Relative
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 1Example (outer stones alive):
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
which has a local score of 5.
If White plays first, we get
which has a local count of -2 (2 points for White).
Later this is White's sente.
And even later, this is Black's sente.
The local score is -2.
After White's hane, Black's reverse sente is worth three points.
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 2Beware of so-called double sente. For instance, Kano's "Yose Dictionary" gives the following as a two-point double sente (p.30).
After the exchange of Black 1 - White 2, White has a one-point sente sequence with White 4 - Black 7. The score is +5 (for Black).
After the exchange of White 1 - Black 2, Black has a one-point sente sequence with Black 4 - White 7. 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).
After Black 1, Black 3 is a gote play worth about 2 1/4 points. If there are bigger plays on the board, White is unlikely to respond to Black 1.
After White 1, White 3 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 White 1. This is a middling gote play. Do not think of it as a double sente. This is a copy of the living page "Double Sente is Relative" at Sensei's Library. (C) the Authors, published under the OpenContent License V1.0. |