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 Post subject: myeongin final ko question
Post #1 Posted: Sun Dec 11, 2011 7:15 pm 
Gosei
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Here's the sgf:



My question: Instead of fighting the ko at 159, what if black just protects on the left side? Is there anything white can do?

Click Here To Show Diagram Code
[go]$$Bcm159 Black's play in the game
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . . . . X O . . . . . . . . . . . |
$$ | . O X X X X X O . . . . . X . . . X . |
$$ | O . O O O O X O . , . . . . X X X O . |
$$ | . O . . . X O . . . . . . X . . X O . |
$$ | . . X O . O . O O . . . . . X X O . . |
$$ | . . . . . . X X X X . X X . O O O . . |
$$ | . . O . . . . . X O . X O . . . X . . |
$$ | . . . O . X . . X O . O . . . . . . . |
$$ | . . O X . . . O O , . . . . O , O . . |
$$ | . . O O X . X X . O . . . . . . . . . |
$$ | . . X O X . . . . . . . . O X X X O . |
$$ | . O O X O X . . . . . . . . O O X O . |
$$ | . O X X O O O O O O . O O O . X O . O |
$$ | . X . X X X X X X . . X O X X X O O X |
$$ | . X X O . . . . . , X X X O X , X X X |
$$ | . O O . O O . . . . X O W O X . . . . |
$$ | . . . O O X X . . X O 1 O . O X O . . |
$$ | . . . . . . . . . X X O . . . X . . . |
$$ ---------------------------------------[/go]


If black protects on the left instead, at first I thought white could threaten life this way:

Click Here To Show Diagram Code
[go]$$Bcm159 ko for life
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . . . . X O . . . . . . . . . . . |
$$ | . O X X X X X O . . . . . X . . . X . |
$$ | O . O O O O X O . , . . . . X X X O . |
$$ | . O . . . X O . . . . . . X . . X O . |
$$ | . . X O . O . O O . . . . . X X O . . |
$$ | . . . . . . X X X X . X X . O O O . . |
$$ | . . O . . . . . X O . X O . . . X . . |
$$ | . . . O . X . . X O . O . . . . . . . |
$$ | . . O X . . . O O , . . . . O , O . . |
$$ | . . O O X . X X . O . . . . . . . . . |
$$ | . . X O X . . . . . . . . O X X X O . |
$$ | . O O X O X . . . . . . . . O O X O . |
$$ | . O X X O O O O O O . O O O . X O . O |
$$ | . X . X X X X X X 1 . X O X X X O O X |
$$ | . X X O . . . . . , X X X O X 5 X X X |
$$ | . O O . O O . . . . X O W O X 2 3 . . |
$$ | . . . O O X X . . X O . O . O X O . . |
$$ | . . . . . . . . . X X O . 6 4 X . . . |
$$ ---------------------------------------[/go]


But black doesn't have to allow that:

Click Here To Show Diagram Code
[go]$$Bcm159 preventing two eyes
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . . . . X O . . . . . . . . . . . |
$$ | . O X X X X X O . . . . . X . . . X . |
$$ | O . O O O O X O . , . . . . X X X O . |
$$ | . O . . . X O . . . . . . X . . X O . |
$$ | . . X O . O . O O . . . . . X X O . . |
$$ | . . . . . . X X X X . X X . O O O . . |
$$ | . . O . . . . . X O . X O . . . X . . |
$$ | . . . O . X . . X O . O . . . . . . . |
$$ | . . O X . . . O O , . . . . O , O . . |
$$ | . . O O X . X X . O . . . . . . . . . |
$$ | . . X O X . . . . . . . . O X X X O . |
$$ | . O O X O X . . . . . . . . O O X O . |
$$ | . O X X O O O O O O . O O O . X O . O |
$$ | . X . X X X X X X 1 . X O X X X O O X |
$$ | . X X O . . . . . , X X X O X , X X X |
$$ | . O O . O O . . . . X O W O X 2 3 . . |
$$ | . . . O O X X . . X O . O . O X O . . |
$$ | . . . . . . . . . X X O . 5 4 X 6 . . |
$$ ---------------------------------------[/go]

Click Here To Show Diagram Code
[go]$$Bcm159 continued
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . . . . X O . . . . . . . . . . . |
$$ | . O X X X X X O . . . . . X . . . X . |
$$ | O . O O O O X O . , . . . . X X X O . |
$$ | . O . . . X O . . . . . . X . . X O . |
$$ | . . X O . O . O O . . . . . X X O . . |
$$ | . . . . . . X X X X . X X . O O O . . |
$$ | . . O . . . . . X O . X O . . . X . . |
$$ | . . . O . X . . X O . O . . . . . . . |
$$ | . . O X . . . O O , . . . . O , O . . |
$$ | . . O O X . X X . O . . . . . . . . . |
$$ | . . X O X . . . . . . . . O X X X O . |
$$ | . O O X O X . . . . . . . . O O X O . |
$$ | . O X X O O O O O O . O O O . X O . O |
$$ | . X . X X X X X X X . X O X X X O O X |
$$ | . X X O . . . . . , X X X O X , X X X |
$$ | . O O . O O . . . . X O O O X O X . . |
$$ | . . . O O X X . . X O . O . O 7 O . . |
$$ | . . . . . . . . . X X O . X O . O . . |
$$ ---------------------------------------[/go]


I realize black doesn't have two eyes either, but there's a sent eye capturing 3 stones, which also gives black a lot of liberties. It doesn't seem like white can win that capturing race.

Can someone help me make sense of this fight?

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 Post subject: Re: myeongin final ko question
Post #2 Posted: Sun Dec 11, 2011 7:20 pm 
Lives in gote
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This might be the move you're looking for:

Click Here To Show Diagram Code
[go]$$Bcm159 Still ko.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . . . . X O . . . . . . . . . . . |
$$ | . O X X X X X O . . . . . X . . . X . |
$$ | O . O O O O X O . , . . . . X X X O . |
$$ | . O . . . X O . . . . . . X . . X O . |
$$ | . . X O . O . O O . . . . . X X O . . |
$$ | . . . . . . X X X X . X X . O O O . . |
$$ | . . O . . . . . X O . X O . . . X . . |
$$ | . . . O . X . . X O . O . . . . . . . |
$$ | . . O X . . . O O , . . . . O , O . . |
$$ | . . O O X . X X . O . . . . . . . . . |
$$ | . . X O X . . . . . . . . O X X X O . |
$$ | . O O X O X . . . . . . . . O O X O . |
$$ | . O X X O O O O O O . O O O . X O . O |
$$ | . X . X X X X X X 1 . X O X X X O O X |
$$ | . X X O . . . . . , X X X O X , X X X |
$$ | . O O . O O . . . . X O W O X . . . . |
$$ | . . . O O X X . . X O . O . O X O . . |
$$ | . . . . . . . . . X X O . 2 . X . . . |
$$ ---------------------------------------[/go]

Also, Dieter wrote a nice analysis of this ko fight on Sensei's, so I won't write more here: http://senseis.xmp.net/?KoFightExampleFromAProGame2

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This post by gogameguru was liked by: emeraldemon
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 Post subject: Re: myeongin final ko question
Post #3 Posted: Sun Dec 11, 2011 8:39 pm 
Gosei
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Thanks, it looks so obvious in retrospect, I just had a blind spot. And the SL page is great, a really nice example.

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 Post subject: Preparing the ko fight
Post #4 Posted: Mon Dec 12, 2011 12:19 pm 
Judan

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I found Park's play throughout the game with that lower side group really interesting. When black played the key shape point of p5 the obvious thing for white to do is connect at o5, or maybe m6 (though that does have some liberty problems with o5 and o2 then n4). But giving black p5 in sente is a bit generous so instead Park played some sente exchanges to make some eyeshape on the side, and then tenukid to a big point, the plan being cutting at o5 and starting the m1 ko were miai.

Click Here To Show Diagram Code
[go]$$c81 Taking sente
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X X X X . . . . . . . X . . . . . |
$$ | . . O O O . . . . , . . . . X X X . . |
$$ | . . . . . . O . . . . . . X . . X O . |
$$ | . . X O . . . . . . . . . . X X O . . |
$$ | . . . . . . . . . . . . . . 8 O O . . |
$$ | . . O . . . . . . . . . . . . . X . . |
$$ | . . . O . . . . X . . . . . . . . . . |
$$ | . . O X . . . . . , . . . . O , O . . |
$$ | . . . O X . . . . . . . . . . . . . . |
$$ | . . . O X . . . . . . . . . . . X . . |
$$ | . O O X O X . . . . . . . . . . . . . |
$$ | . O X X O O O O O O . . . O . . . . . |
$$ | . X . X X X X X X . . . . . 1 . . . . |
$$ | . X X O . . . . . , X . . O X , X . . |
$$ | . O O . O O . . . . X O . O X . . . . |
$$ | . . . O O X X . . 3 2 . 6 . 4 5 . . . |
$$ | . . . . . . . . . . 7 . . . . . . . . |
$$ ---------------------------------------[/go]


Sometime later black swallowed the group, but Park showed nice technique in getting in the r2 kikashi and making black connect at k1, leaving some aji still in his group.

Click Here To Show Diagram Code
[go]$$c127 Sacrificed, but not a clean kill for black
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . . . . X O . . . . . . . . . . . |
$$ | . O X X X X X O . . . . . X . . . . . |
$$ | O . O O O O X O . , . . . . X X X . . |
$$ | . O . . . X O . . . . . . X . . X O . |
$$ | . . X O . O . O O . . . . . X X O . . |
$$ | . . . . . . X X X X . X . . O O O . . |
$$ | . . O . . . . . X O . . . . . . X . . |
$$ | . . . O . X . . X O . . . . . . . . . |
$$ | . . O X . . . O O , . . . . O , O . . |
$$ | . . O O X . X X . O . . . . . . . . . |
$$ | . . X O X . . . . . . . . . . . X . . |
$$ | . O O X O X . . . . . . . . . . . . . |
$$ | . O X X O O O O O O . O 6 O . . . . . |
$$ | . X . X X X X X X . . X 4 X X . . . . |
$$ | . X X O . . . . . , X 7 5 O X , X . . |
$$ | . O O . O O . . . . X O . O X . . . . |
$$ | . . . O O X X . . X O . O . O X 2 . . |
$$ | . . . . . . . . . 1 X O . . . 3 . . . |
$$ ---------------------------------------[/go]


When I was replaying this game n12 confused me when white then tenukid black's n13. "What was the point of that?" I thought. But these moves were preparation for the ko and it all became clear 44 moves later: by getting in these kikashi white made black o9 a less effective ko threat as n12 slowed down black's attempt to cut white, a nice example of the "covering fire" effect of kikashi. Note also s16 is a yose move which generates a few big threats with the r17 cut.

Click Here To Show Diagram Code
[go]$$Wc150 Preparing the ko
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . . . . X O . . . . . . . . . . . |
$$ | . O X X X X X O . . . . . X . . . 8 . |
$$ | O . O O O O X O . , . . . . X X X 7 . |
$$ | . O . . . X O . . . . . . X . . X O . |
$$ | . . X O . O . O O . . . . . X X O . . |
$$ | . . . . . . X X X X . X 6 . O O O . . |
$$ | . . O . . . . . X O . 4 1 . . . X . . |
$$ | . . . O . X . . X O . 5 . . . . . . . |
$$ | . . O X . . . O O , . . . . O , O . . |
$$ | . . O O X . X X . O . . . . . . . . . |
$$ | . . X O X . . . . . . . . 3 2 X X O . |
$$ | . O O X O X . . . . . . . . O O X O . |
$$ | . O X X O O O O O O . O O O . X O . O |
$$ | . X . X X X X X X . . X O X X X O O X |
$$ | . X X O . . . . . , X X X O X , X X X |
$$ | . O O . O O . . . . X O 9 O X . . . . |
$$ | . . . O O X X . . X O . O . O X O . . |
$$ | . . . . . . . . . X X O . . . X . . . |
$$ ---------------------------------------[/go]


So when white ignores black's o9 threat, the n12 kikashi come in handy as white can connect his groups. This does make me wonder though if black's block at n13 was soft, maybe he should cut as a probe to avoid being kikashid?

Click Here To Show Diagram Code
[go]$$c193 White connects thanks to n12 kikashis
$$ ---------------------------------------
$$ | . X . . . O O . . . . . . . . . . . . |
$$ | O X . . . . X O . . . . . . . . X X . |
$$ | . O X X X X X O . . . . . X . . O X O |
$$ | O . O O O O X O . , . . . . X X X O . |
$$ | . O . . O . O . . . . . . X . . X O . |
$$ | . . X O . O X O O . . . . . X X O . . |
$$ | . . . . . O X X X X . X X . O O O . . |
$$ | . . O . . . X . X O . X O 3 . . X . . |
$$ | . . . O . X X O X O . O 1 . . . . . . |
$$ | . . O X . . . O O , . . 2 4 O , O . . |
$$ | . . O O X . X X . O . . . X . . . . . |
$$ | . . X O X . . . . . . . . O X X X O . |
$$ | . O O X O X . . . . . . . . O O X O . |
$$ | . O X X O O O O O O . O O O . X . X O |
$$ | . X . X X X X X X . . X O X X X . . X |
$$ | . X X O X . . . . X X X X O X , X X X |
$$ | . O O . O O . . O O X O O O X . . . . |
$$ | . O . O O X X . O X . X O . O X O . . |
$$ | . . . . . . . . . X X . X . . X . . . |
$$ ---------------------------------------[/go]


If white hadn't made the n12 exchanges, then black's o9 threat would be more powerful as white can't connect his groups so is in some considerable danger.

Click Here To Show Diagram Code
[go]$$c White cut, entire centre in danger
$$ ---------------------------------------
$$ | . X . . . O O . . . . . . . . . . . . |
$$ | O X . . . . X O . . . . . . . . X X . |
$$ | . O X X X X X O . . . . . X . . O X O |
$$ | O . O O O O X O . , . . . . X X X O . |
$$ | . O . . O . O . . . . . . X . . X O . |
$$ | . . X O . O X O O . . . . . X X O . . |
$$ | . . . . . O X X X X . X . . O O O . . |
$$ | . . O . . . X . X O . 5 4 . . . X . . |
$$ | . . . O . X X O X O . . 1 . . . . . . |
$$ | . . O X . . . O O , . . 2 3 O , O . . |
$$ | . . O O X . X X . O . . . X . . . . . |
$$ | . . X O X . . . . . . . . O X X X O . |
$$ | . O O X O X . . . . . . . . O O X O . |
$$ | . O X X O O O O O O . O O O . X . X O |
$$ | . X . X X X X X X . . X O X X X . . X |
$$ | . X X O X . . . . X X X X O X , X X X |
$$ | . O O . O O . . O O X O O O X . . . . |
$$ | . O . O O X X . O X . X O . O X O . . |
$$ | . . . . . . . . . X X . X . . X . . . |
$$ ---------------------------------------[/go]


A beautiful sacrifice from Park, getting 110% value out of his dead stones. (He even has g3 yose left for desserts!).


This post by Uberdude was liked by: emeraldemon
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 Post subject: Re: myeongin final ko question
Post #5 Posted: Mon Dec 12, 2011 4:45 pm 
Lives in gote
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emeraldemon wrote:
Thanks, it looks so obvious in retrospect, I just had a blind spot. And the SL page is great, a really nice example.

Obvious in retrospect, perhaps. When I looked at the game I had similar thoughts to you and the first thing I read was similar to your variation above where white dies. After that I kept reading.

Just remember, KEEP READING :).

@Uberdude
Nice analysis. Another point that's worth noting is that white could have easily lived at move 4 in your second diagram, but chose to sacrifice (in sente) and leave the ko aji instead. I think many of us would've been reluctant to play that way when there's a clear way to live (including me).

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 Post subject: Re: myeongin final ko question
Post #6 Posted: Wed Dec 14, 2011 11:54 am 
Judan

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Yeah, sacrificing is hard and requires a lot of confidence in your judgement of the game. I think my play is relatively inflexible and is something I am trying to improve. Reviewing Go Seigen's games should help with that, but his plans are often rather advanced and hard to understand ;-). Rewinding a few moves when black played m5 I think it is here white chose to sacrifice the group (for now) and block off the centre at m6. He could have played as below but then I expect black jumps into the middle, separating white and aiming at the cut at a. And although white connected to o6 the group is still not settled.


Click Here To Show Diagram Code
[go]$$c117 Connect group, but black splits
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . O X X X X X . . . . . . X . . . . . |
$$ | O . O O O O X O . , . . . . X X X . . |
$$ | . O . . . X O . . . . . . X . . X O . |
$$ | . . X O . O . O O . . . . . X X O . . |
$$ | . . . . . . X X X X . . . . O O O . . |
$$ | . . O . . . . . X O . . . . . . X . . |
$$ | . . . O . X . . X O . . . . . . . . . |
$$ | . . O X . . . O O , . . . . O , O . . |
$$ | . . O O X . X X . O . . . . . . . . . |
$$ | . . X O X . . . . a . . . . . . X . . |
$$ | . O O X O X . . . . . 3 . . . . . . . |
$$ | . O X X O O O O O O . . . O . . . . . |
$$ | . X . X X X X X X . . 1 . 2 X . . . . |
$$ | . X X O . . . . . , X . . O X , X . . |
$$ | . O O . O O . . . . X O . O X . . . . |
$$ | . . . O O X X . . X O . O . O X . . . |
$$ | . . . . . . . . . . X . . . . . . . . |
$$ ---------------------------------------[/go]

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