Punishing joseki mistake (problem)

[Magicwand]

That's what herman is saying I think entropi.

not really.. what herman is saying is ..16 & 17 exchange is an aji keshi that only helps black cover his weakness. although endgame point of view it is not optimal but in the opening part of the game it is better not playing optimally. black is not going to play 16 anytime soon because it is an aji keshi so there is no point playing endgame that only expose your weakness.



16-17 exchange will coverup the weakness at 'a'

$$Bm13
$$ ------------------
$$ | . . . . . . . . .
$$ | . . O . 2 O 1 . .
$$ | . . X O O X O 3 .
$$ | . O O X X X . . .
$$ | . 4 X a . . . . .
$$ | . . 5 . . . . . .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$Bm13
$$ ------------------
$$ | . . . . . . . . .
$$ | . . O . 2 O 1 . .
$$ | . . X O O X O 3 .
$$ | . O O X X X . . .
$$ | . 4 X a . . . . .
$$ | . . 5 . . . . . .
$$ | . . . . . . . . .[/go]

[HermanHiddema]

That's what herman is saying I think entropi.

not really.. what herman is saying is ..16 & 17 exchange is an aji keshi that only helps black cover his weakness. although endgame point of view it is not optimal but in the opening part of the game it is better not playing optimally. black is not going to play 16 anytime soon because it is an aji keshi so there is no point playing endgame that only expose your weakness.



16-17 exchange will coverup the weakness at 'a'

$$Bm13
$$ ------------------
$$ | . . . . . . . . .
$$ | . . O . 2 O 1 . .
$$ | . . X O O X O 3 .
$$ | . O O X X X . . .
$$ | . 4 X a . . . . .
$$ | . . 5 . . . . . .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$Bm13
$$ ------------------
$$ | . . . . . . . . .
$$ | . . O . 2 O 1 . .
$$ | . . X O O X O 3 .
$$ | . O O X X X . . .
$$ | . 4 X a . . . . .
$$ | . . 5 . . . . . .
$$ | . . . . . . . . .[/go]

Actually, that was what I was saying in the text above my diagram.

Also, it's probably good to play this exchange anyway, even though it removes aji, because otherwise:

$$B
$$ ------------------
$$ | . . . . . . . . .
$$ | . . O . O O X . .
$$ | . . X O O X C X .
$$ | . O O X X X B . .
$$ | . 1 X . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$B
$$ ------------------
$$ | . . . . . . . . .
$$ | . . O . O O X . .
$$ | . . X O O X C X .
$$ | . O O X X X B . .
$$ | . 1 X . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

If black ever captures the white stone with (e.g. white played a ladder breaker) then becomes sente:

$$B
$$ ------------------
$$ | . . . 5 . 7 a . .
$$ | 6 2 O . O O X . .
$$ | . 1 X O O X C X .
$$ | 3 O O X X X B . .
$$ | . X X . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$B
$$ ------------------
$$ | . . . 5 . 7 a . .
$$ | 6 2 O . O O X . .
$$ | . 1 X O O X C X .
$$ | 3 O O X X X B . .
$$ | . X X . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

Now, white can't ignore the capture and play tenuki with , because then and kill. As long as a is still atari (i.e. before the capture of white stone at ), black can't kill, but:

$$B
$$ ------------------
$$ | . . . 5 . . 6 . .
$$ | 8 2 O . O O X . .
$$ | . 1 X O O X O X .
$$ | 3 O O X X X 7 . .
$$ | . X X . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$B
$$ ------------------
$$ | . . . 5 . . 6 . .
$$ | 8 2 O . O O X . .
$$ | . 1 X O O X O X .
$$ | 3 O O X X X 7 . .
$$ | . X X . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

This is a rather painful way to lose a ladder breaker.

So all in all, White should usually just play the exchange in the original diagram, even though it is aji keshi a little.

[zinger]

Rolling back a few moves ...

$$
$$ ------------------
$$ | . . . . . . . . .
$$ | . . . . . O . . .
$$ | . . X O O X O . .
$$ | . 3 O X X 2 . . .
$$ | . . 1 . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$
$$ ------------------
$$ | . . . . . . . . .
$$ | . . . . . O . . .
$$ | . . X O O X O . .
$$ | . 3 O X X 2 . . .
$$ | . . 1 . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

When black plays 1, is it feasible for white to capture with 2? For ease of viewing it would look like this:

$$
$$ ------------------
$$ | . . . . . . . . .
$$ | . . . . . O . . .
$$ | . . X O O . O . .
$$ | . X . X X O . . .
$$ | . . X . . . . . .
$$ | . . . . . a . . .
$$ | . . . . . b . . .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$
$$ ------------------
$$ | . . . . . . . . .
$$ | . . . . . O . . .
$$ | . . X O O . O . .
$$ | . X . X X O . . .
$$ | . . X . . . . . .
$$ | . . . . . a . . .
$$ | . . . . . b . . .
$$ | . . . . . . . . .[/go]

True there is a loss in the corner, but white is much thicker than in the joseki. It seems like this might be playable in an approriate whole board position.

Next white can take sente to play elsewhere, or locally jump to a or even b.

[Harleqin]

I think that it is feasible, although the loss in the corner is quite big, so the sente has to be worth it.

[fwiffo]

Kogo's lists that as a joseki variation, but it's Kogo's.

[amnal]

I believe kogos is, in this case, correct. It seems to be fairly common for pros to capture instead of extending.

[Dusk Eagle]

As you can see at Cho Hye-yeon's blog, that joseki has been played by pros. http://loveku.livejournal.com/?skip=1