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AnswerKeimaWithKo...

 

keima slide and ogeima slide
  Difficulty: Dan level   Keywords: Shape

Discussion originally on answer keima with kosumi.

[Diagram]
Diag.: Answer keima with kosumi (i)

This is another common kosumi response to a keima.


[Diagram]
Diag.: Answer keima with kosumi (ii)

But when White plays ogeima, the tobi is the usual response.

I learned this years ago. Frankly, I have forgotten why. Yesterday I saw Prof. Teigo Nakamura 6-dan. He has the most encyclopedic go knowledge of any amateur I know. He had forgotten why, too. ;-) But he spent a few minutes playing with the position and came up with the answer.


[Diagram]
Diag.: Black's play

If Black answers the ogeima with kosumi (both marked), later he can play Black 1 - Black 7.


[Diagram]
Diag.: White's play

If White protects with White 1, she threatens to jump in at a. Note that Black had responded at a instead of the kosumi (marked), he would still threaten to play at b, but White would not have a big threat after White 1.

--BillSpight

(Moved from answer keima with kosumi.)



Charles Matthews I have wondered about this, having seen something very similar in an old Japanese book on tesuji.[1]

Firstly, there is no 'shape-based' rule.

[Diagram]
Diag.: Either answer ...

If one looks at this sort of pattern, just somewhere on the side, then Black a and Black b are both commonly seen.

If one specialises to the case of the small high enclosure, then the diagonal move answer is more popular:


[Diagram]
Diag.: Enclosure, knight's move slide

Black 1 here is much more popular than Black at a.


[Diagram]
Diag.: Enclosure, ogeima slide

Black 1 is more popular than Black a.

These come from database search: they may contradict the book I read.

Looking, as one should, into the game context, the diagonal move answers do seem to be in the type of position where Black wants to take sente.


[Diagram]
Diag.: Enclosure, ogeima slide variant

There may be something in the idea that the one-point jump answer Black 1 here invites White 2 and 4, at which point Black would want to add another stone here.


[Diagram]
Diag.: Enclosure, knight's move slide variant

In the keima slide case, White's immediate cut with 4 and 6 is possibly tactically. (White would like a good ladder for this, but perhaps that isn't a precondition?)



[1] A 1955 book by Kano Yoshinori. Here are the actual positions.

[Diagram]
Diag.: First case

Black 1 is given as correct. In three pro games, Black played tenuki from the corner.


[Diagram]
Diag.: Second case

Black 1 here is given as correct. This is more plausible: a low-ranked Korean pro has played a, but as a rule this is what one sees.

Charles Matthews



This is a copy of the living page "keima slide and ogeima slide" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.