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 Post subject: Endgame problem from a recent game
Post #1 Posted: Tue Dec 01, 2020 2:26 pm 
Lives with ko
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After all these years.. here is my first problem.

It is very rare that a very book-ish position comes up in a real game but it happened to me two days ago in the last game of an online tournament I was playing in. My opponent, who was playing white, had just tenuki-ed from the lower left corner to connect two stones on the right side with 2, clearly thinking that this is the last big move to be played. However, he overlooked some very painful aji in the lower left corner and quickly answered my 3 at 4 (which should've been played at C2).

Click Here To Show Diagram Code
[go]$$c Black to play and use some aji in the best way possible.
$$ ---------------------------------------
$$ | . X O O O . . O O O X X . . . . . . . |
$$ | . . X X O O O . . O X . X . . . . . . |
$$ | . X . X X O O . O O O X X X . . . X X |
$$ | . . X O O O O O X O X X . O X X X X O |
$$ | . . X O X X O . X X X O O . O X X O O |
$$ | . . X O X O . O O . X X X O . O O O . |
$$ | . . . X X O O . O X X O O O . O O . . |
$$ | . . . . . X O X X X O O . . . O . . . |
$$ | . . . . . X X . O O . . . . . . O O . |
$$ | . . X X . . X O . , . . O O O O . . O |
$$ | . . . . . . X O . . . O X X X X O O 2 |
$$ | . . . . . X O O . . . O O X . X X X O |
$$ | . . . . . X O X O . . O X . X . . X O |
$$ | . X X X X X X X O . O X X X . O . . X |
$$ | X X O O O X . X O . . O X . . . . X . |
$$ | X O . , X O X X X O . . O X X O O . . |
$$ | O 4 O . . O O O O . . O . O X . X O . |
$$ | . 3 . . . . . . . . . . O O X . X X . |
$$ | . . . . . . . . . . . . O X X . . . . |
$$ ---------------------------------------[/go]


Of course there are several variations depending on white's answer. I'll put the next two moves from the game in the following spoiler tags. There's a really interesting line here that I missed from being overly confident, so if you've had a try at the first diagram, maybe you want to think about this as well. Can you do it better than me? :)

Click Here To Show Diagram Code
[go]$$c If white refuses to back down, how can black profit from this? AI says black may live in the corner now (a thought pretty disturbing for my EGF 4-5k mind :D )
$$ ---------------------------------------
$$ | . X O O O . . O O O X X . . . . . . . |
$$ | . . X X O O O . . O X . X . . . . . . |
$$ | . X . X X O O . O O O X X X . . . X X |
$$ | . . X O O O O O X O X X . O X X X X O |
$$ | . . X O X X O . X X X O O . O X X O O |
$$ | . . X O X O . O O . X X X O . O O O . |
$$ | . . . X X O O . O X X O O O . O O . . |
$$ | . . . . . X O X X X O O . . . O . . . |
$$ | . . . . . X X . O O . . . . . . O O . |
$$ | . . X X . . X O . , . . O O O O . . O |
$$ | . . . . . . X O . . . O X X X X O O 2 |
$$ | . . . . . X O O . . . O O X . X X X O |
$$ | . . . . . X O X O . . O X . X . . X O |
$$ | . X X X X X X X O . O X X X . O . . X |
$$ | X X O O O X . X O . . O X . . . . X . |
$$ | X O . , X O X X X O . . O X X O O . . |
$$ | O 4 O 5 6 O O O O . . O . O X . X O . |
$$ | . 3 . . . . . . . . . . O O X . X X . |
$$ | . . . . . . . . . . . . O X X . . . . |
$$ ---------------------------------------[/go]

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 Post subject: Re: Endgame problem from a recent game
Post #2 Posted: Tue Dec 01, 2020 2:38 pm 
Gosei
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- Wrong variation - deleted.


Last edited by jlt on Tue Dec 01, 2020 2:59 pm, edited 1 time in total.
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 Post subject: Re: Endgame problem from a recent game
Post #3 Posted: Tue Dec 01, 2020 2:54 pm 
Oza
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Click Here To Show Diagram Code
[go]$$B
$$ -----------------------------------------
$$ | . X O O O . . O O O X X . . . . . . . |
$$ | . . X X O O O . . O X . X . . . . . . |
$$ | . X . X X O O . O O O X X X . . . X X |
$$ | . . X O O O O O X O X X . O X X X X O |
$$ | . . X O X X O . X X X O O . O X X O O |
$$ | . . X O X O . O O . X X X O . O O O . |
$$ | . . . X X O O . O X X O O O . O O . . |
$$ | . . . . . X O X X X O O . . . O . . . |
$$ | . . . . . X X . O O . . . . . . O O . |
$$ | . . X X . . X O . , . . O O O O . . O |
$$ | . . . . . . X O . . . O X X X X O O O |
$$ | . . . . . X O O . . . O O X . X X X O |
$$ | . . . . . X O X O . . O X . X . . X O |
$$ | . X X X X X X X O . O X X X . O . . X |
$$ | X X O O O X . X O . . O X . . . . X . |
$$ | X O 2 , X O X X X O . . O X X O O . . |
$$ | O O O 1 4 O O O O . . O . O X . X O . |
$$ | 5 X 3 . . . . . . . . . O O X . X X . |
$$ | . . . . . . . . . . . . O X X . . . . |
$$ ---------------------------------------[/go]

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


... are my two lines. After checking the hidden OP, indeed there is also:

Click Here To Show Diagram Code
[go]$$B
$$ -----------------------------------------
$$ | . X O O O . . O O O X X . . . . . . . |
$$ | . . X X O O O . . O X . X . . . . . . |
$$ | . X . X X O O . O O O X X X . . . X X |
$$ | . . X O O O O O X O X X . O X X X X O |
$$ | . . X O X X O . X X X O O . O X X O O |
$$ | . . X O X O . O O . X X X O . O O O . |
$$ | . . . X X O O . O X X O O O . O O . . |
$$ | . . . . . X O X X X O O . . . O . . . |
$$ | . . . . . X X . O O . . . . . . O O . |
$$ | . . X X . . X O . , . . O O O O . . O |
$$ | . . . . . . X O . . . O X X X X O O O |
$$ | . . . . . X O O . . . O O X . X X X O |
$$ | . . . . . X O X O . . O X . X . . X O |
$$ | . X X X X X X X O . O X X X . O . . X |
$$ | X X O O O X . X O . . O X . . . . X . |
$$ | X O 8 4 B O X X X O . . O X X O O . . |
$$ | O O O 1 2 O O O O . . O . O X . X O . |
$$ | 5 X 7 3 9 . . . . . . . O O X . X X . |
$$ | . . . . . . . . . . . . O X X . . . . |
$$ ---------------------------------------[/go]

:w6: at the marked stone


Last edited by Knotwilg on Tue Dec 01, 2020 2:58 pm, edited 1 time in total.
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 Post subject: Re: Endgame problem from a recent game
Post #4 Posted: Tue Dec 01, 2020 2:57 pm 
Gosei
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Knotwilg: I initially thought about your second variation, however I think White's :w4: would be different:

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

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 Post subject: Re: Endgame problem from a recent game
Post #5 Posted: Tue Dec 01, 2020 2:58 pm 
Lives with ko
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jlt wrote:
Knotwilg: I initially thought about your second variation, however I think White's :w4: would be different:

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

This is actually the seuqnece from the game. However, accoring to AI, black can get a better result.

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 Post subject: Re: Endgame problem from a recent game
Post #6 Posted: Tue Dec 01, 2020 2:59 pm 
Oza
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Check my edit

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 Post subject: Re: Endgame problem from a recent game
Post #7 Posted: Tue Dec 01, 2020 3:01 pm 
Lives with ko
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jlt wrote:
Click Here To Show Diagram Code
[go]$$c
$$ ---------------------------------------
$$ | . X O O O . . O O O X X . . . . . . . |
$$ | . . X X O O O . . O X . X . . . . . . |
$$ | . X . X X O O . O O O X X X . . . X X |
$$ | . . X O O O O O X O X X . O X X X X O |
$$ | . . X O X X O . X X X O O . O X X O O |
$$ | . . X O X O . O O . X X X O . O O O . |
$$ | . . . X X O O . O X X O O O . O O . . |
$$ | . . . . . X O X X X O O . . . O . . . |
$$ | . . . . . X X . O O . . . . . . O O . |
$$ | . . X X . . X O . , . . O O O O . . O |
$$ | . . . . . . X O . . . O X X X X O O 2 |
$$ | . . . . . X O O . . . O O X . X X X O |
$$ | . . . . . X O X O . . O X . X . . X O |
$$ | . X X X X X X X O . O X X X . O . . X |
$$ | X X O O O X . X O . . O X . . . . X . |
$$ | X O . 2 . O X X X O . . O X X O O . . |
$$ | O O O . O O O O O . . O . O X . X O . |
$$ | 1 X X O . . . . . . . . O O X . X X . |
$$ | . . . . . . . . . . . . O X X . . . . |
$$ ---------------------------------------[/go]


But after your 9 (1 here) there comes 2, right?

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 Post subject: Re: Endgame problem from a recent game
Post #8 Posted: Tue Dec 01, 2020 3:02 pm 
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Knotwilg wrote:
Click Here To Show Diagram Code
[go]$$B
$$ -----------------------------------------
$$ | . X O O O . . O O O X X . . . . . . . |
$$ | . . X X O O O . . O X . X . . . . . . |
$$ | . X . X X O O . O O O X X X . . . X X |
$$ | . . X O O O O O X O X X . O X X X X O |
$$ | . . X O X X O . X X X O O . O X X O O |
$$ | . . X O X O . O O . X X X O . O O O . |
$$ | . . . X X O O . O X X O O O . O O . . |
$$ | . . . . . X O X X X O O . . . O . . . |
$$ | . . . . . X X . O O . . . . . . O O . |
$$ | . . X X . . X O . , . . O O O O . . O |
$$ | . . . . . . X O . . . O X X X X O O O |
$$ | . . . . . X O O . . . O O X . X X X O |
$$ | . . . . . X O X O . . O X . X . . X O |
$$ | . X X X X X X X O . O X X X . O . . X |
$$ | X X O O O X . X O . . O X . . . . X . |
$$ | X O 2 , X O X X X O . . O X X O O . . |
$$ | O O O 1 4 O O O O . . O . O X . X O . |
$$ | 5 X 3 . . . . . . . . . O O X . X X . |
$$ | . . . . . . . . . . . . O X X . . . . |
$$ ---------------------------------------[/go]

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


... are my two lines. After checking the hidden OP, indeed there is also:

Click Here To Show Diagram Code
[go]$$B
$$ -----------------------------------------
$$ | . X O O O . . O O O X X . . . . . . . |
$$ | . . X X O O O . . O X . X . . . . . . |
$$ | . X . X X O O . O O O X X X . . . X X |
$$ | . . X O O O O O X O X X . O X X X X O |
$$ | . . X O X X O . X X X O O . O X X O O |
$$ | . . X O X O . O O . X X X O . O O O . |
$$ | . . . X X O O . O X X O O O . O O . . |
$$ | . . . . . X O X X X O O . . . O . . . |
$$ | . . . . . X X . O O . . . . . . O O . |
$$ | . . X X . . X O . , . . O O O O . . O |
$$ | . . . . . . X O . . . O X X X X O O O |
$$ | . . . . . X O O . . . O O X . X X X O |
$$ | . . . . . X O X O . . O X . X . . X O |
$$ | . X X X X X X X O . O X X X . O . . X |
$$ | X X O O O X . X O . . O X . . . . X . |
$$ | X O 8 4 B O X X X O . . O X X O O . . |
$$ | O O O 1 2 O O O O . . O . O X . X O . |
$$ | 5 X 7 3 9 . . . . . . . O O X . X X . |
$$ | . . . . . . . . . . . . O X X . . . . |
$$ ---------------------------------------[/go]

:w6: at the marked stone


Yup, the second one is what AI suggests and what I missed. Nice job! :)

Looks like it was too easy. Hope you still had some fun with it.

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 Post subject: Re: Endgame problem from a recent game
Post #9 Posted: Tue Dec 01, 2020 3:03 pm 
Oza
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It's a surprising line indeed. I would definitely not think of it in a game.


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Post #10 Posted: Tue Dec 01, 2020 3:03 pm 
Gosei
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@Ember: Yes I realized my answer was wrong after posting it and deleted it.

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 Post subject: Re: Endgame problem from a recent game
Post #11 Posted: Tue Dec 01, 2020 3:05 pm 
Oza
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Which means

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


Not that the whole thing mattered for the end result, I think.

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 Post subject: Re: Endgame problem from a recent game
Post #12 Posted: Wed Dec 02, 2020 12:54 am 
Lives with ko
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Knotwilg wrote:
Not that the whole thing mattered for the end result, I think.

Yes, that's right, it made no difference to the final result. But as someone who during games often feels like a blind person with a wooden stick in a swamp, I like to poke at stuff with my stick when I find something of interest. :)

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