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Preventing shimari from growing in fuseki
   

In the fuseki don't allow your opponent to get a double wing formation.

[Diagram]
Diag.: Double wing formation is usually a great claim

Try to prevent this formation in the fuseki. Usually the wedge in the middle of the right side helps if played early.



[Diagram]
Diag.: Double wing formation

In professional games the upper side stone is usually played one line further away, as shown here. That makes a five-line extension on both sides. Now White typically reduces at a or b.

DaveSigaty - Hmmm... These days I can't resist asking, "Yes, that's what they say, but what do pro's really do?!". The tools are available to try to answer this such questions. :-)

Here is the result from searching across the 17,000+ games in the July 2002 update of the GoGoD CD. As familiar as this formation seems, it appears only nine times (so in general the pro's do not let their opponents make the double-wing formation?):

[Diagram]
Diag.: Search Pattern

[Diagram]
Diag.: Continuations

In two of the games, W ignores the moyo around the shimari and B plays next within the search area. In the other seven games W tries 6 different approaches. Only the shoulder hit at "f" in the diagram appears more than once. Surprisingly W won 5 of the 9 games despite letting B make the double-wing formation.


Statistics:

9 matches (6/3), B: 44.4%, W: 55.6%

 Wf:    2 (1), B100.0% - W0.0%
 Wd:    1 (0), B0.0% - W100.0%
 Wh:    1 (1), B0.0% - W100.0%
 Be:    1 (0), B0.0% - W100.0%
 Wb:    1 (0), B0.0% - W100.0%
 Wa:    1 (0), B100.0% - W0.0%
 Wg:    1 (0), B0.0% - W100.0%
 Bc:    1 (0), B100.0% - W0.0%

Game list

 1943-05-26a: Kitani Minoru     - Iwamoto Kaoru   (B) 13a
 1977-03-10:  Fujisawa Hideyuki - Otake Hideo     (W) 11b
 1981-02-19b: Honda Kunihisa    - Kato Masao      (B) 21c
 1981-07-09c: Hasegawa Sunao    - O Rissei        (B) 18d-
 1981-09-23b: Awaji Shuzo       - Tokimoto Hajime (B) 12e-
 1987-06-11c: Kobayashi Koichi  - Kato Masao      (B) 13f
 1994-12-22a: Kato Masao        - Cho Chikun      (B) 24g-
 2000-09-11:  Zhou Heyang       - Xie He          (W) 17h
 2002-03-15d: Yu Ch'ang-hyeok   - An Cho-yeong    (B) 15f

Charles Matthews The basic wisdom about not allowing your opponent double wing formations around an enclosure is often illustrated by problems with ryojimari positions. It is interesting to use a database also to look at how the pros play such positions, in komi go. It certainly isn't the case that they make it a strict rule to deny the opponent the double wing formation.



This is a copy of the living page "Preventing shimari from growing in fuseki" at Sensei's Library.
(C) the Authors, published under the OpenContent License V1.0.