defending the corner

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nickxyzt
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defending the corner

Post by nickxyzt »

Hi,

I have a question regarding the following diagram (Get strong at tesuji, problem #14) - black to defend the corner:
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O O . . . . . . . . . . . . . . . |
$$ | . . X O . X . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


The answer in the book is:
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O O . . . . . . . . . . . . . . . |
$$ | . 2 X O . X . . . . . . . . . . . . . |
$$ | . 1 3 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Could anybody point out what is the difference with the next diagram? What am doing wrong?
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O O . . . . . . . . . . . . . . . |
$$ | . 2 X O . X . . . . . . . . . . . . . |
$$ | . 3 1 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
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lovelove
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Re: defending the corner

Post by lovelove »

Your diagrams are exactly the same result, but there can be difference when white tenukis.

Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 1 O O . . . . . . . . . . . . . . . |
$$ | . . X O . X . . . . . . . . . . . . . |
$$ | . X . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O O . . . . . . . . . . . . . . . |
$$ | . 1 X O . X . . . . . . . . . . . . . |
$$ | . . X X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


This is why tiger mouth is joseki.
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Uberdude
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Re: defending the corner

Post by Uberdude »

nickxyzt wrote:Could anybody point out what is the difference with the next diagram? What am doing wrong?
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O O . . . . . . . . . . . 3 . . . |
$$ | . 2 X O . X . . . . . . . . . . . . . |
$$ | . . 1 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


2 is not 100% sente, black can choose to play 3 elsewhere depending how big other moves are.

The reason the hanging connection is (usually) better than solid is if white tenukis, then you can increase your territory and eyespace in sente (notice how :b1: means white can't capture :b3: if black now tenukis):

Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . 4 . . . . . . . . . . . . . . . . . |
$$ | . 3 O O . . . . . . . . . . . 2 . . . |
$$ | . . X O . X . . . . . . . . . . . . . |
$$ | . 1 . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


If you just played solid, then you'd need to end in gote if you want to defend :b3:

Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . 4 . . . . . . . . . . . . . . . . . |
$$ | . 3 O O . . . . . . . . . . . 2 . . . |
$$ | 5 . X O . X . . . . . . . . . . . . . |
$$ | . . 1 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


The reason white should play atari as in your second diagram is it makes black's 2nd line move there gote instead of sente.

Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . 6 . . . . . . . . . . . . . . . . . |
$$ | . 5 O O . . . . . . . . . . . 4 . . . |
$$ | 7 2 X O . X . . . . . . . . . . . . . |
$$ | . 1 3 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


A more subtle advantage of the hanging connection over the solid is that it makes better eyeshape: Imagine white plays e3 as a ko threat and black ignores (or through some other fighting in this area black gets cut off here), he can live unconditionally in the corner:

Click Here To Show Diagram Code
[go]$$W
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . 5 . . . . . . . . . . . . . . . . . |
$$ | . 4 O O . . . . . . . . . . . . . . . |
$$ | 6 O X O 1 X . . . . . . . . . . . . . |
$$ | . X X X 3 . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


With the solid, it is only a ko for life in the corner (tripod group with extra leg):

Click Here To Show Diagram Code
[go]$$W
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . 5 . . . . . . . . . . . . . . . . . |
$$ | . 4 O O . . . . . . . . . . . . . . . |
$$ | 6 . X O 1 X . . . . . . . . . . . . . |
$$ | . . X X 3 . . . . . . . . . . . . . . |
$$ | . 7 . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


There is a possible advantage of the solid connection though, that is if you don't expect the additional eyeshape of the hanging connection to be useful and in the yose you wish to play this sente yose sequence. White can try to prevent black making this sente profit by exchanging b3 for b2 (if black ignores then white's block at b2 is big and sente to capture 3 stones) so that it reverts to the hanging connection shape with just the gote capture as black's yose here. Which of these outcomes is more likely basically comes down to who will have sente to start the endgame, which is not an easy thing to say.

Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | 4 6 . . . . . . . . . . . . . . . . . |
$$ | 3 2 O O . . . . . . . . . . . . . . . |
$$ | 5 1 X O . X . . . . . . . . . . . . . |
$$ | . . X X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
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drmwc
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Re: defending the corner

Post by drmwc »

To add one more point to Uberdude's excellent post, consider the effect of the following two moves:

Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 2 O O . . . . . . . . . . . , . . . |
$$ | . . X O . X . . . . . . . . . . . . . |
$$ | . . 1 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


and:

Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 4 O O . . . . . . . . . . . , . . . |
$$ | . 2 X O . X . . . . . . . . . . . . . |
$$ | . 1 3 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


The first diagram is potentially better yose for W, due the possibility of a 2-2 point attachement as follow up.

Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . 2 O O . . . . . . . . . . . , . . . |
$$ | . . X O . X . . . . . . . . . . . . . |
$$ | . 4 1 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


On alisghtly different strand, one yose move for W to watch out for is 4 below, which saves a couple of points:
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | 4 . O O . . . . . . . . . . . , . . . |
$$ | . 3 X O . X . . . . . . . . . . . . . |
$$ | . . 1 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


The reason is that B 7 below is now gote (dependent on the other yose on the board):

Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . 6 . . . . . . . . . . . . . . . . . |
$$ | 4 5 O O . . . . . . . . . . . , . . . |
$$ | 7 3 X O . X . . . . . . . . . . . . . |
$$ | . . 1 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Alternatively, B could play as follows but get 2 points less than when W descends for 4:
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | 4 6 O O . . . . . . . . . . . , . . . |
$$ | 5 3 X O . X . . . . . . . . . . . . . |
$$ | . . 1 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]
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Dusk Eagle
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Re: defending the corner

Post by Dusk Eagle »

drmwc wrote:Alternatively, B could play as follows but get 2 points less than when W descends for 4:
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | 4 6 O O . . . . . . . . . . . , . . . |
$$ | 5 3 X O . X . . . . . . . . . . . . . |
$$ | . . 1 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Although, if white tenukis for :w6:, the result is no different then if black had pushed at :w6: with :b5:, white blocked, black descended to :b5:, and white tenukis.
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drmwc
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Re: defending the corner

Post by drmwc »

Dusk Eagle wrote:
drmwc wrote:Alternatively, B could play as follows but get 2 points less than when W descends for 4:
Click Here To Show Diagram Code
[go]$$B
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | 4 6 O O . . . . . . . . . . . , . . . |
$$ | 5 3 X O . X . . . . . . . . . . . . . |
$$ | . . 1 X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Although, if white tenukis for :w6:, the result is no different then if black had pushed at :w6: with :b5:, white blocked, black descended to :b5:, and white tenukis.


True.
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illluck
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Re: defending the corner

Post by illluck »

Uberdude, I don't quite agree with "The reason the hanging connection is (usually) better than solid is if white tenukis, then you can increase your territory and eyespace in sente" because white pretty much will never tenuki and black has to take gote to connect. I think the strength of the group is the most important determinant - if the group is strong then the connect is preferred due to the descent being sente later.
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