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Endgame tesuji from 20th Judan game 2
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Author:  xela [ Sat Apr 19, 2025 5:03 am ]
Post subject:  Endgame tesuji from 20th Judan game 2
Click Here To Show Diagram Code
[go]$$B Cho Chikun (W) vs Otake Hideo on 1982-03-11, position after white 196
$$ ---------------------------------------
$$ | . . O X X X X X X . . . . . . . . . . |
$$ | . O O X X O O X . X . . . . . . . . . |
$$ | . . X O X O . O X X . . . . X . . . . |
$$ | . X . O O O . O O X . . X . . X X . . |
$$ | . O O . . . . O O X . . . O . X . X . |
$$ | . . . . . . X O X X . . . . . O X . X |
$$ | . . . . . . O . O O X X X X . X X X O |
$$ | . . X . X . X O X O X O X O . O O O . |
$$ | . O O O O O . X . . O O O O . O X . O |
$$ | . . . , . . O O O , . . . . O , X . . |
$$ | . X c X X X X X X X . . X O X O O O O |
$$ | . a . X O . . . . O O O X X X X X X . |
$$ | . . O O O O . . . . . X O O . . X . . |
$$ | b . . O X X X X . O . O X O . X . X . |
$$ | . O O . O O X . O O O O X O . . X . X |
$$ | O . . O O X X . X O X X X O . O O X . |
$$ | X O O X X . . X X O O O X . O . . O . |
$$ | X X X . . . . . . X X X X O . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Black to play the best endgame move on the left side.

In the actual game, Otake played 'a'. I wondered about the monkey jump at 'b' instead, but it doesn't work because of the weakness at 'c'. KataGo found a surprising tesuji which is better than the game move.
Author:  kvasir [ Sun Apr 20, 2025 11:34 pm ]
Post subject:  Re: Endgame tesuji from 20th Judan game 2
I think it is like this.

Click Here To Show Diagram Code
[go]$$B
$$ +--------------------------------------+
$$ | . . O X X X X X X . . . . . . . . . .|
$$ | . O O X X O O X . X . . . . . . . . .|
$$ | . . X O X O . O X X . . . . X . . . .|
$$ | . X . O O O . O O X . . X . . X X . .|
$$ | . O O . . . . O O X . . . O . X . X .|
$$ | . . . . . . X O X X . . . . . O X . X|
$$ | . . . . . . O . O O X X X X . X X X O|
$$ | 6 8 X . X . X O X O X O X O . O O O .|
$$ | 5 O O O O O . X . . O O O O . O X . O|
$$ | 7 1 . 3 . . O O O , . . . . O , X . .|
$$ | . X . X X X X X X X . . X O X O O O O|
$$ | . 4 2 X O . . . . O O O X X X X X X .|
$$ | . . O O O O . . . . . . O O . . X . .|
$$ | . . . O X X X X . O . O X O . X . X .|
$$ | . O O . O O X . O O O O X O . . X . X|
$$ | O . . O O X X . X O X X X O . O O X .|
$$ | X O O X X . . X X O O O X . O . . O .|
$$ | X X X . . . . . . X X X X O . . O . .|
$$ | . . . . . . . . . . . . . . . . . . .|
$$ +--------------------------------------+[/go]


But if white blocks on the other side then the monkey jump is coming.

Click Here To Show Diagram Code
[go]$$W
$$ +--------------------------------------+
$$ | . . O X X X X X X . . . . . . . . . .|
$$ | . O O X X O O X . X . . . . . . . . .|
$$ | . . X O X O . O X X . . . . X . . . .|
$$ | . X . O O O . O O X . . X . . X X . .|
$$ | . O O . . . . O O X . . . O . X . X .|
$$ | . . . . . . X O X X . . . . . O X . X|
$$ | . . . . . . O . O O X X X X . X X X O|
$$ | . . X . X . X O X O X O X O . O O O .|
$$ | 1 O O O O O . X . . O O O O . O X . O|
$$ | . X . , . . O O O , . . . . O , X . .|
$$ | . X 8 X X X X X X X . . X O X O O O O|
$$ | 6 . 7 X O . . . . O O O X X X X X X .|
$$ | 4 . O O O O . . . . . . O O . . X . .|
$$ | 2 3 . O X X X X . O . O X O . X . X .|
$$ | 5 O O . O O X . O O O O X O . . X . X|
$$ | O . . O O X X . X O X X X O . O O X .|
$$ | X O O X X . . X X O O O X . O . . O .|
$$ | X X X . . . . . . X X X X O . . O . .|
$$ | . . . . . . . . . . . . . . . . . . .|
$$ +--------------------------------------+[/go]


There is a real surprise if white fails to protect with :w8: in the first diagram.

Click Here To Show Diagram Code
[go]$$B
$$ +--------------------------------------+
$$ | . . O X X X X X X . . . . . . . . . .|
$$ | . O O X X O O X . X . . . . . . . . .|
$$ | 5 . X O X O . O X X . . . . X . . . .|
$$ | . X . O O O . O O X . . X . . X X . .|
$$ | . O O . . . . O O X . . . O . X . X .|
$$ | 4 3 . . . . X O X X . . . . . O X . X|
$$ | 2 . . . . . O . O O X X X X . X X X O|
$$ | O 1 X . X . X O X O X O X O . O O O .|
$$ | X O O O O O . X . . O O O O . O X . O|
$$ | X X . X . . O O O , . . . . O , X . .|
$$ | . X . X X X X X X X . . X O X O O O O|
$$ | . O O X O . . . . O O O X X X X X X .|
$$ | . . O O O O . . . . . . O O . . X . .|
$$ | . . . O X X X X . O . O X O . X . X .|
$$ | . O O . O O X . O O O O X O . . X . X|
$$ | O . . O O X X . X O X X X O . O O X .|
$$ | X O O X X . . X X O O O X . O . . O .|
$$ | X X X . . . . . . X X X X O . . O . .|
$$ | . . . . . . . . . . . . . . . . . . .|
$$ +--------------------------------------+[/go]
Author:  xela [ Tue Apr 22, 2025 5:37 am ]
Post subject:  Re: Endgame tesuji from 20th Judan game 2
kvasir wrote:
I think it is like this.

Oh, that's nice!

To split hairs, KataGo thinks this way is about half a point better. This is all a bit above my level; I'm just posting it because the first move is so striking.
Click Here To Show Diagram Code
[go]$$B
$$ ---------------------------------------
$$ | . . O X X X X X X . . . . . . . . . . |
$$ | . O O X X O O X . X . . . . . . . . . |
$$ | . . X O X O . O X X . . . . X . . . . |
$$ | . X . O O O . O O X . . X . . X X . . |
$$ | . O O . . . . O O X . . . O . X . X . |
$$ | . . . . . . X O X X . . . . . O X . X |
$$ | . . . . . . O . O O X X X X . X X X O |
$$ | a . X . X . X O X O X O X O . O O O . |
$$ | 1 O O O O O . X . . O O O O . O X . O |
$$ | . . . , . . O O O , . . . . O , X . . |
$$ | . X . X X X X X X X . . X O X O O O O |
$$ | . . . X O . . . . O O O X X X X X X . |
$$ | . . O O O O . . . . . X O O . . X . . |
$$ | . . . O X X X X . O . O X O . X . X . |
$$ | . O O . O O X . O O O O X O . . X . X |
$$ | O . . O O X X . X O X X X O . O O X . |
$$ | X O O X X . . X X O O O X . O . . O . |
$$ | X X X . . . . . . X X X X O . . O . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


The point, according to my limited understanding, is that for white to reply at 'a' really is too passive (as opposed to your first variation, which is the better option for white). So KataGo's idea of best play for both sides is:

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


Black's loss with letting :b1: be captured is more than made up for by the monkey jump, so this is a full point better than the game move.
Author:  kvasir [ Tue Apr 22, 2025 1:26 pm ]
Post subject:  Re: Endgame tesuji from 20th Judan game 2
I wanted to find a way to make that move work but I tricked myself somewhere in the variations and thought I had found a way for white to resist the monkey jump.
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