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 Post subject: Re: Beat Elf!
Post #21 Posted: Sat Oct 19, 2019 8:51 am 
Honinbo

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The third one comes from GoGoD 1996-01-31a, between Kobayashi Satoru (W) and Cho Chikun. I found it when I was looking for a game for How is your positional judgement? ( https://lifein19x19.com/viewtopic.php?f=15&t=16909 ). ;)

Earlier in the game.

Click Here To Show Diagram Code
[go]$$Bcm7 White blunders
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . O 4 5 . . . |
$$ | . . . O . . . . . , . . 9 1 2 X 0 . . |
$$ | . . . . . . . . . . . . . . 3 6 7 . . |
$$ | . . . . . . . . . . . . . . . 8 a . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Cho played sanrensei and played the jump attachment, :b7:, against Kobayashi's approach. Kobayashi replied with the unorthodox wedge. (Elf's choice is 10.) I suspect that Cho set a trap for White with :b15:. If so, White fell into it with :w16:. In any event, :w16: is a blunder. According to Elf it loses 23% by comparison with a.

Click Here To Show Diagram Code
[go]$$Bcm17 A tale of two ladders
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . O O X 1 . . |
$$ | . . . O . . . . . , . a X X O X O c . |
$$ | . . . . . . . . . . . . 4 2 X O X . . |
$$ | . . . . . . . . . . . . . . 3 O . . . |
$$ | . . . . . . . . . . . . . . b . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


With :w18: and :w20: Kobayashi set up two possible ladders at a and b. Elf recommends c instead. This two ladder setup is a common tactic when the shape is one line closer to the top side. I'm sure that Kobayashi had seen classical problems and ancient game records with Black's refutation. Maybe he was having a bad day. Elf's winrate estimate is skewed by the fact that Elf had perhaps never played the refutation against itself in its training. We can estimate White's loss at around 18%.

Click Here To Show Diagram Code
[go]$$Bcm21 Off with their heads!
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . O O X X . . |
$$ | . . . O . . . . . , . . X X O X O . . |
$$ | . . . . . . . . . . . 1 O O X O X . . |
$$ | . . . . . . . . . . . 6 4 3 X O . . . |
$$ | . . . . . . . . . . 7 . . 5 2 a . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


The double ladder breaker, :b27:, was completely off Elf's radar (0 playouts). Elf's first choice was a (241.8k playouts), for a comparative loss of 18½%. Go Seigen criticized Cho Chikun for taking too much time in the opening. But in this case Cho might have played :b27: in two seconds flat.

It is obvious that :b27: breaks the ladder from the right, but where is this ladder from the top? Glad you asked. :cool:

Click Here To Show Diagram Code
[go]$$Wcm28 The other ladder
$$ ---------------------------------------
$$ | . . . . . . . . . . 9 8 . . . . . . . |
$$ | . . . . . . . . . . 7 6 3 . . . . . . |
$$ | . . . . . . . . . . 5 4 2 O O X X . . |
$$ | . . . O . . . . . , 0 1 X X O X O . . |
$$ | . . . . . . . . . . . X O O X O X . . |
$$ | . . . . . . . . . . . O O X X O . . . |
$$ | . . . . . . . . . . X . . X O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


White pushes Black to the edge, then :b37: captures :w28:.

Click Here To Show Diagram Code
[go]$$Wcm38 The other ladder, continued
$$ ---------------------------------------
$$ | . . . . . . . . . . O X 1 . . . . . . |
$$ | . . . . . . . . . . O X O . . . . . . |
$$ | . . . . . . . . . . O X X O O X X . . |
$$ | . . . O . . . . . 3 X 2 X X O X O . . |
$$ | . . . . . . . . . . 4 X O O X O X . . |
$$ | . . . . . . . . . . . O O X X O . . . |
$$ | . . . . . . . . . . B . . X O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


:w38: is atari. After :b39: fills, :w40: starts the ladder up again. This kind of ladder is called a spiral ladder ( https://senseis.xmp.net/?TurnaroundLadder ). Anyway, it is now obvious that :bc: breaks it. :D

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Last edited by Bill Spight on Sat Oct 19, 2019 9:02 am, edited 3 times in total.
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 Post subject: Re: Beat Elf!
Post #22 Posted: Sat Oct 19, 2019 8:58 am 
Lives with ko

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Bill Spight wrote:
I ran across this one the other day.

Click Here To Show Diagram Code
[go]$$Wcm26 Black to play.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . O O X X . . |
$$ | . . . O . . . . . , . . X X O X O . . |
$$ | . . . . . . . . . . . X O O X O X . . |
$$ | . . . . . . . . . . . O O X X O . . . |
$$ | . . . . . . . . . . . . . X O . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

One of my favourite games, and I like to use this position as an example sometimes: https://github.com/bernds/q5Go#database-support


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 Post subject: Re: Beat Elf!
Post #23 Posted: Sat Oct 19, 2019 9:09 am 
Lives in gote

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KGS: Tryss
:b27: was also off Katago radar. With 100k playout, it didn't explore it, and when played, it's a +25% move (or about 10 pts).

This is how Katago try to salvage the situation :

Click Here To Show Diagram Code
[go]$$Wcm28 Katago choice (38-39-40 at a-b-c)
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . a 7 1 . . . . . 0 . |
$$ | . . . . . . . . 8 . 6 . . O O X X 9 . |
$$ | . . . O . . . . . , . 2 X X O X O 3 . |
$$ | . . . . . . . . . . . X O O X O X 4 . |
$$ | . . . . . . . . c . 5 O O X X O . . . |
$$ | . . . . . . . . . . X . . X O b . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


And it put white at 30% winrate, with -9 pts


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