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 Post subject: Sneaky ko threat and tesuji from Kim Jiseok
Post #1 Posted: Thu Apr 20, 2017 6:28 am 
Tengen

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Kim Jiseok won his game today against Heo Yongho in the 4th round of the GS Caltex cup with a very sneaky ko threat and follow-up tesuji that impressed me. It was endgame and they were fighting a few points ko on the top left when Kim played at :w2:. Was this just making good shape and a point or two or was it actually a threat? His opponent didn't see any danger and took the next ko with :b3:. See if you can find the threat, explained in the hidden below.

Click Here To Show Diagram Code
[go]$$B Kim Jiseok (white) vs Heo Yongho
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . O . |
$$ | . O O O X X X X X . O O X O X O O X . |
$$ | O . . . O X X O O . O X O O X O X X O |
$$ | 3 O O O X X . . . , O X X O X X O O . |
$$ | O 1 O . . . O O X X X O X . O O O . . |
$$ | X . X O . X . . O O O O X X O X X X . |
$$ | . X X . X . . . . . . . O X X X X . . |
$$ | . . X . . . X X . . 2 . O O X O O O . |
$$ | . X . O X X O . O . . X X O X . . . . |
$$ | . X . O O X O . O , . X O O . X . X . |
$$ | X . X . . O X X O X X . X X X . . . . |
$$ | X . X X O O . . O X O . . O X . . . . |
$$ | X X O X X O O X O . . O O O X . . . . |
$$ | O O O . X X X O O . O X O X . . . . . |
$$ | . . O O O O X X O O O X . X . . . . . |
$$ | . . . , X O X O X X X X . . . , X . . |
$$ | . . . O . X O O X X O . . . X . . . . |
$$ | . . . . . O . O O X X . . . . . . . . |
$$ | . . . . . . . . O O X . . . . . . . . |
$$ +---------------------------------------+[/go]


After the presumed time tesuji of :w1: for :b2: , Kim unleashed the atekomi tesuji of :w3:! Heo must have been so shocked he played his own time tesuji of :b4: 4 but that was only worth about 20 points so Kim ignored to cut and kill black's larger top group and Heo resigned.
Click Here To Show Diagram Code
[go]$$W Game continuation: White + Resign
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . O . |
$$ | . O O O X X X X X . O O X O X O O X . |
$$ | O . . . O X X O O . O X O O X O X X O |
$$ | X O O O X X . . . , O X X O X X O O . |
$$ | . X O . . 7 O O X X X O X 4 O O O . 1 |
$$ | X . X O 5 X . . O O O O X X O X X X 2 |
$$ | . X X 6 X 3 . . . . . . O X X X X . . |
$$ | . . X . . . X X . . O . O O X O O O . |
$$ | . X . O X X O . O . . X X O X . . . . |
$$ | . X . O O X O . O , . X O O . X . X . |
$$ | X . X . . O X X O X X . X X X . . . . |
$$ | X . X X O O . . O X O . . O X . . . . |
$$ | X X O X X O O X O . . O O O X . . . . |
$$ | O O O . X X X O O . O X O X . . . . . |
$$ | . . O O O O X X O O O X . X . . . . . |
$$ | . . . , X O X O X X X X . . . , X . . |
$$ | . . . O . X O O X X O . . . X . . . . |
$$ | . . . . . O . O O X X . . . . . . . . |
$$ | . . . . . . . . O O X . . . . . . . . |
$$ +---------------------------------------+[/go]


But even if Heo answered Kim's move was genius and could gain something. First if black just ataris then white can now cut and kill the top due to :w4: now being atari giving him time to connect back at :w6:.
Click Here To Show Diagram Code
[go]$$B
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . O . |
$$ | . O O O X X X X X . O O X O X O O X . |
$$ | O . . . O X X O O . O X O O X O X X O |
$$ | X O O O X X . . . , O X X O X X O O . |
$$ | . X O 6 3 2 O O X X X O X . O O O . O |
$$ | X . X O 4 X . . O O O O X X O X X X X |
$$ | . X X . X O 1 . . . . . O X X X X . . |
$$ | . . X . . 5 X X . . O . O O X O O O . |
$$ | . X . O X X O . O . . X X O X . . . . |
$$ | . X . O O X O . O , . X O O . X . X . |
$$ | X . X . . O X X O X X . X X X . . . . |
$$ | X . X X O O . . O X O . . O X . . . . |
$$ | X X O X X O O X O . . O O O X . . . . |
$$ | O O O . X X X O O . O X O X . . . . . |
$$ | . . O O O O X X O O O X . X . . . . . |
$$ | . . . , X O X O X X X X . . . , X . . |
$$ | . . . O . X O O X X O . . . X . . . . |
$$ | . . . . . O . O O X X . . . . . . . . |
$$ | . . . . . . . . O O X . . . . . . . . |
$$ +---------------------------------------+[/go]


So the next idea is black connects. Now if white just pushes then black's block at :b3: is a mistake as :w4: would capture 3 stones (if connect then when :w6: runs out black can't capture it. White's initial marked ko threat stone makes a difference here, I'll go into variations later).
Click Here To Show Diagram Code
[go]$$B White's plan
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . O . |
$$ | . O O O X X X X X . O O X O X O O X . |
$$ | O . . . O X X O O . O X O O X O X X O |
$$ | X O O O X X . . . , O X X O X X O O . |
$$ | . X O . . . O O X X X O X . O O O . O |
$$ | X . X O 1 X . . O O O O X X O X X X X |
$$ | . X X 3 X O 6 . . . . . O X X X X . . |
$$ | . . X 2 4 5 X X . . W . O O X O O O . |
$$ | . X . O X X O . O . . X X O X . . . . |
$$ | . X . O O X O . O , . X O O . X . X . |
$$ | X . X . . O X X O X X . X X X . . . . |
$$ | X . X X O O . . O X O . . O X . . . . |
$$ | X X O X X O O X O . . O O O X . . . . |
$$ | O O O . X X X O O . O X O X . . . . . |
$$ | . . O O O O X X O O O X . X . . . . . |
$$ | . . . , X O X O X X X X . . . , X . . |
$$ | . . . O . X O O X X O . . . X . . . . |
$$ | . . . . . O . O O X X . . . . . . . . |
$$ | . . . . . . . . O O X . . . . . . . . |
$$ +---------------------------------------+[/go]


So black would answer push with making one eye inside, and added to the one of the top edge he is alive even though cut off:
Click Here To Show Diagram Code
[go]$$B Black lives inside
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . O . |
$$ | . O O O X X X X X . O O X O X O O X . |
$$ | O . . . O X X O O . O X O O X O X X O |
$$ | X O O O X X . . . , O X X O X X O O . |
$$ | . X O . . . O O X X X O X . O O O . O |
$$ | X . X O 1 X 3 . O O O O X X O X X X X |
$$ | . X X 4 X O . . . . . . O X X X X . . |
$$ | . . X 2 . . X X . . W . O O X O O O . |
$$ | . X . O X X O . O . . X X O X . . . . |
$$ | . X . O O X O . O , . X O O . X . X . |
$$ | X . X . . O X X O X X . X X X . . . . |
$$ | X . X X O O . . O X O . . O X . . . . |
$$ | X X O X X O O X O . . O O O X . . . . |
$$ | O O O . X X X O O . O X O X . . . . . |
$$ | . . O O O O X X O O O X . X . . . . . |
$$ | . . . , X O X O X X X X . . . , X . . |
$$ | . . . O . X O O X X O . . . X . . . . |
$$ | . . . . . O . O O X X . . . . . . . . |
$$ | . . . . . . . . O O X . . . . . . . . |
$$ +---------------------------------------+[/go]


So white would play :w2: here. Now if black connects at 3 to save the 2 stones then white pushes at :w4: (having destroyed the half eye in sente) and if black blocks above white cuts and it reverts to the previous-but-one diagram and kills the 6 stones (as the 2 cutting stones can't be captured). And if black plays :b5: at :w6: white just plays the other and the whole black group is dead.
Click Here To Show Diagram Code
[go]$$B White captures something if black tries to save all
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . O . |
$$ | . O O O X X X X X . O O X O X O O X . |
$$ | O . . . O X X O O . O X O O X O X X O |
$$ | X O O O X X . . . , O X X O X X O O . |
$$ | . X O . . . O O X X X O X . O O O . O |
$$ | X . X O 1 X . . O O O O X X O X X X X |
$$ | . X X 5 X O 2 . . . . . O X X X X . . |
$$ | . . X 4 6 3 X X . . O . O O X O O O . |
$$ | . X . O X X O . O . . X X O X . . . . |
$$ | . X . O O X O . O , . X O O . X . X . |
$$ | X . X . . O X X O X X . X X X . . . . |
$$ | X . X X O O . . O X O . . O X . . . . |
$$ | X X O X X O O X O . . O O O X . . . . |
$$ | O O O . X X X O O . O X O X . . . . . |
$$ | . . O O O O X X O O O X . X . . . . . |
$$ | . . . , X O X O X X X X . . . , X . . |
$$ | . . . O . X O O X X O . . . X . . . . |
$$ | . . . . . O . O O X X . . . . . . . . |
$$ | . . . . . . . . O O X . . . . . . . . |
$$ +---------------------------------------+[/go]


So black's best play is to give up the 2 stones, but then white cuts them and makes a nice handful of points in the centre:
Click Here To Show Diagram Code
[go]$$B Best for both after the tesuji
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . O . |
$$ | . O O O X X X X X . O O X O X O O X . |
$$ | O . . . O X X O O . O X O O X O X X O |
$$ | X O O O X X . . . , O X X O X X O O . |
$$ | . X O . . . O O X X X O X . O O O . O |
$$ | X . X O 1 X . . O O O O X X O X X X X |
$$ | . X X . X O 2 . . . . . O X X X X . . |
$$ | . . X . 3 4 X X . . O . O O X O O O . |
$$ | . X . O X X O . O . . X X O X . . . . |
$$ | . X . O O X O . O , . X O O . X . X . |
$$ | X . X . . O X X O X X . X X X . . . . |
$$ | X . X X O O . . O X O . . O X . . . . |
$$ | X X O X X O O X O . . O O O X . . . . |
$$ | O O O . X X X O O . O X O X . . . . . |
$$ | . . O O O O X X O O O X . X . . . . . |
$$ | . . . , X O X O X X X X . . . , X . . |
$$ | . . . O . X O O X X O . . . X . . . . |
$$ | . . . . . O . O O X X . . . . . . . . |
$$ | . . . . . . . . O O X . . . . . . . . |
$$ +---------------------------------------+[/go]


So why didn't this sequence work without white's sneaky ko threat? Because black would use the peep of :b7: (which threatens to cut and capture the larger 6 stones than his 2 in the centre) and use that and white's shortage of liberties to extricate his 2 cut stones.
Click Here To Show Diagram Code
[go]$$B Black's counter without white's ko threat
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . O . |
$$ | . O O O X X X X X . O O X O X O O X . |
$$ | O . . . O X X O O . O X O O X O X X O |
$$ | . O O O X X . . . , O X X O X X O O . |
$$ | O 1 O . . . O O X X X O X . O O O . . |
$$ | X . X O 3 X . . O O O O X X O X X X . |
$$ | . X X . X 2 4 . . . . . O X X X X . . |
$$ | . . X . 5 6 X X . . 7 . O O X O O O . |
$$ | . X . O X X O . O . . X X O X . . . . |
$$ | . X . O O X O . O , . X O O . X . X . |
$$ | X . X . . O X X O X X . X X X . . . . |
$$ | X . X X O O . . O X O . . O X . . . . |
$$ | X X O X X O O X O . . O O O X . . . . |
$$ | O O O . X X X O O . O X O X . . . . . |
$$ | . . O O O O X X O O O X . X . . . . . |
$$ | . . . , X O X O X X X X . . . , X . . |
$$ | . . . O . X O O X X O . . . X . . . . |
$$ | . . . . . O . O O X X . . . . . . . . |
$$ | . . . . . . . . O O X . . . . . . . . |
$$ +---------------------------------------+[/go]


If white defends like this and the wedges he gets caught in a shortage of liberties (actually 5 could make ko but if black wins the ko there's more death for white with throw ins utilising the 3 dead stones above).
Click Here To Show Diagram Code
[go]$$W Continued: var 1
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . O . |
$$ | . O O O X X X X X . O O X O X O O X . |
$$ | O . . . O X X O O . O X O O X O X X O |
$$ | . O O O X X . . . , O X X O X X O O . |
$$ | O X O . . . O O X X X O X . O O O . . |
$$ | X . X O X X 6 8 O O O O X X O X X X . |
$$ | . X X . X O O 7 9 5 1 0 O X X X X . . |
$$ | . . X . X O X X 2 3 X . O O X O O O . |
$$ | . X . O X X O . O 4 . X X O X . . . . |
$$ | . X . O O X O . O , . X O O . X . X . |
$$ | X . X . . O X X O X X . X X X . . . . |
$$ | X . X X O O . . O X O . . O X . . . . |
$$ | X X O X X O O X O . . O O O X . . . . |
$$ | O O O . X X X O O . O X O X . . . . . |
$$ | . . O O O O X X O O O X . X . . . . . |
$$ | . . . , X O X O X X X X . . . , X . . |
$$ | . . . O . X O O X X O . . . X . . . . |
$$ | . . . . . O . O O X X . . . . . . . . |
$$ | . . . . . . . . O O X . . . . . . . . |
$$ +---------------------------------------+[/go]


And if defends like this then black connects home as :b6: makes a and b miai:
Click Here To Show Diagram Code
[go]$$W Continued: var 2
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . O . |
$$ | . O O O X X X X X . O O X O X O O X . |
$$ | O . . . O X X O O . O X O O X O X X O |
$$ | . O O O X X . . . , O X X O X X O O . |
$$ | O X O . . . O O X X X O X . O O O . . |
$$ | X . X O X X a . O O O O X X O X X X . |
$$ | . X X . X O O . 6 4 b 1 O X X X X . . |
$$ | . . X . X O X X 2 3 X . O O X O O O . |
$$ | . X . O X X O . O 5 . X X O X . . . . |
$$ | . X . O O X O . O , . X O O . X . X . |
$$ | X . X . . O X X O X X . X X X . . . . |
$$ | X . X X O O . . O X O . . O X . . . . |
$$ | X X O X X O O X O . . O O O X . . . . |
$$ | O O O . X X X O O . O X O X . . . . . |
$$ | . . O O O O X X O O O X . X . . . . . |
$$ | . . . , X O X O X X X X . . . , X . . |
$$ | . . . O . X O O X X O . . . X . . . . |
$$ | . . . . . O . O O X X . . . . . . . . |
$$ | . . . . . . . . O O X . . . . . . . . |
$$ +---------------------------------------+[/go]


All-in-all, a beautiful tesuji from Kim Jiseok. :clap: :clap: :clap:


This post by Uberdude was liked by 12 people: Bill Spight, BlindGroup, daal, dfan, hyperpape, jeromie, joellercoaster, Kirby, lobotommy, Solomon, Waylon, wolfking
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 Post subject: Re: Sneaky ko threat and tesuji from Kim Jiseok
Post #2 Posted: Thu Apr 20, 2017 11:36 am 
Gosei
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Awesome analysis Uberdude!

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 Post subject: Re: Sneaky ko threat and tesuji from Kim Jiseok
Post #3 Posted: Thu Apr 20, 2017 11:51 am 
Gosei
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https://youtu.be/hqdNomwAk7E?t=46m1s


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 Post subject: Re: Sneaky ko threat and tesuji from Kim Jiseok
Post #4 Posted: Thu Apr 20, 2017 9:36 pm 
Lives in gote

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Solomon wrote:
https://youtu.be/hqdNomwAk7E?t=46m1s


You can see the commentator point out white's follow up to the ko threat right away. Also you can see when Heo Yongho plays his time tesuji, Kim Jiseok comes very close to answering it quickly, but then reconsiders.

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 Post subject: Re: Sneaky ko threat and tesuji from Kim Jiseok
Post #5 Posted: Fri Apr 21, 2017 2:55 am 
Tengen

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Thanks for the video link Solomon. Watching Heo's pained body language (and given the commentator saw it too) I think maybe he did see some bad aji or at least realised he was in a bad situation, so maybe this was a case of "if I defend I lose so be greedy and take the points and resign if he finds the working sequence" (I didn't actually count*). Also he disappeared for a break and the clocks stopped (but Kim could keep reading) after blocking Kim's timesuji which surprised me: are they allowed to leave like that for a toilet break, or can he just pause the game to splash cold water on his face and calm his nerves? I'm not even allowed to have a toilet break in our amateur tournaments between Canadian byo-yomi periods.

* Edit: Now that I've done a quick count I think black wins by about 1.5 if he answers the sneaky ko threat and submits in the top left ko, so probably he left to slap himself for losing a won game?

Here's the full game:


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 Post subject: Re: Sneaky ko threat and tesuji from Kim Jiseok
Post #6 Posted: Fri Apr 21, 2017 5:00 am 
Lives in gote
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Really, you're not allowed toilet breaks during byo-yomi in Canada? No one does that here in the Netherlands either but I'm pretty sure EGF rules allow it (within reason, of course).

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 Post subject: Re: Sneaky ko threat and tesuji from Kim Jiseok
Post #7 Posted: Fri Apr 21, 2017 5:35 am 
Tengen

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gaius, I replied in this new thread: viewtopic.php?p=218611#p218611.

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