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understanding endgame tesuji from Lee Sedol's game
http://lifein19x19.com/viewtopic.php?f=15&t=7344
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Author:  xed_over [ Mon Dec 03, 2012 12:09 am ]
Post subject:  understanding endgame tesuji from Lee Sedol's game

A few of us kyu players were recently looking at this game in Lee Sedol's book, and we didn't understand the very brief commentary remark about this endgame move, and was wondering if there are any stronger players out there willing to try and expound further on the commentary.

Commented Games by Lee Sedol I
Part 24, p. 106-107
move 139

GoGoD: 2000-12-04a.sgf

Click Here To Show Diagram Code
[go]$$Wm138
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . X . O . . . . . O . 3 . |
$$ | . X . X . . X . X O . . . . . . O 2 . |
$$ | . O X , . . X X O , . X . . O O X 1 . |
$$ | O . O X . . . O . O . . . O X . X . . |
$$ | . O O O X . . . O . . O . O X . X . d |
$$ | . . O . X . . . . . . . . O X O . . . |
$$ | . . . O X . . . . . . . . . X . . . . |
$$ | . . . O X . . . . . . . X . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . O O . . X . . X X . X X X X . |
$$ | . . . . O X . . . X X O . . O X O X . |
$$ | O . X O X . . X X O O . X . . O O O . |
$$ | . O O O X . X O . . . . . . . . . . . |
$$ | O X X O X . O O . O O O O O O O . . . |
$$ | . X . X O O . X X O X X O X X . O O . |
$$ | X . . X . . . O X X . X X . . X O X . |
$$ | . X X . . . . . . . . . . X X . X . . |
$$ ---------------------------------------[/go]


Lee Sedol wrote:
There is a cut at :b39: in the following sequence that is played to prevent White from following up at d. This is a tesuji that amateur players should watch out for. It may seem trivial, but it could make a big difference in a close game.


Our question is: Couldn't :b39: simply block at S15 to also prevent White following up at d?

(I couldn't use board coordinates because of a bug with alternate starting numbers)

edit: my move numbers were off by 1. white 138 is the hane, and black 139 is the cut in question. corrected diagram.

Author:  HermanHiddema [ Mon Dec 03, 2012 1:31 am ]
Post subject:  Re: understanding endgame tesuji from Lee Sedol's game

White can ignore that move. Afte S15, the best black can do is capture a stone. After the tesuji (S17), if white ignores, black can extend to S18 (the 2-2) point. So the point of the tesuji is not so much that it prevents d, but that it does so in sente.

Author:  logan [ Mon Dec 03, 2012 1:55 am ]
Post subject:  Re: understanding endgame tesuji from Lee Sedol's game

Click Here To Show Diagram Code
[go]$$Wcm139
$$ ---------------------------------------
$$ | 2 . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . X . O . . . . . O . . . |
$$ | . X . X . . X . X O . . . . . . O 6 . |
$$ | . O X , . . X X O , . X . . O O X 1 7 |
$$ | O . O X . . . O . O . . . O X . X 4 5 |
$$ | . O O O X . . . O . . O . O X . X . 3 |
$$ | . . O . X . . . . . . . . O X O . . . |
$$ | . . . O X . . . . . . . . . X . . . . |
$$ | . . . O X . . . . . . . X . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . O O . . X . . X X . X X X X . |
$$ | . . . . O X . . . X X O . . O X O X . |
$$ | O . X O X . . X X O O . X . . O O O . |
$$ | . O O O X . X O . . . . . . . . . . . |
$$ | O X X O X . O O . O O O O O O O . . . |
$$ | . X . X O O . X X O X X O X X . O O . |
$$ | X . . X . . . O X X . X X . . X O X . |
$$ | . X X . . . . . . . . . . X X . X . . |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$Wcm139
$$ ---------------------------------------
$$ | 2 . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . X . O . . . . . O . . . |
$$ | . X . X . . X . X O . . . . . . O 4 . |
$$ | . O X , . . X X O , . X . . O O X 1 . |
$$ | O . O X . . . O . O . . . O X . X . 5 |
$$ | . O O O X . . . O . . O . O X . X . 3 |
$$ | . . O . X . . . . . . . . O X O . . . |
$$ | . . . O X . . . . . . . . . X . . . . |
$$ | . . . O X . . . . . . . X . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . O O . . X . . X X . X X X X . |
$$ | . . . . O X . . . X X O . . O X O X . |
$$ | O . X O X . . X X O O . X . . O O O . |
$$ | . O O O X . X O . . . . . . . . . . . |
$$ | O X X O X . O O . O O O O O O O . . . |
$$ | . X . X O O . X X O X X O X X . O O . |
$$ | X . . X . . . O X X . X X . . X O X . |
$$ | . X X . . . . . . . . . . X X . X . . |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$Wcm139
$$ ---------------------------------------
$$ | 4 . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . X . O . . . . . O . 3 . |
$$ | . X . X . . X . X O . . . . . . O 2 . |
$$ | . O X , . . X X O , . X . . O O X 1 . |
$$ | O . O X . . . O . O . . . O X . X 6 . |
$$ | . O O O X . . . O . . O . O X . X . 5 |
$$ | . . O . X . . . . . . . . O X O . . . |
$$ | . . . O X . . . . . . . . . X . . . . |
$$ | . . . O X . . . . . . . X . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . O O . . X . . X X . X X X X . |
$$ | . . . . O X . . . X X O . . O X O X . |
$$ | O . X O X . . X X O O . X . . O O O . |
$$ | . O O O X . X O . . . . . . . . . . . |
$$ | O X X O X . O O . O O O O O O O . . . |
$$ | . X . X O O . X X O X X O X X . O O . |
$$ | X . . X . . . O X X . X X . . X O X . |
$$ | . X X . . . . . . . . . . X X . X . . |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$Wcm139
$$ ---------------------------------------
$$ | 3 . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . X . O . . . . . O . 4 . |
$$ | . X . X . . X . X O . . . . . . O 2 . |
$$ | . O X , . . X X O , . X . . O O X 1 . |
$$ | O . O X . . . O . O . . . O X . X . . |
$$ | . O O O X . . . O . . O . O X . X . . |
$$ | . . O . X . . . . . . . . O X O . . . |
$$ | . . . O X . . . . . . . . . X . . . . |
$$ | . . . O X . . . . . . . X . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . O O . . X . . X X . X X X X . |
$$ | . . . . O X . . . X X O . . O X O X . |
$$ | O . X O X . . X X O O . X . . O O O . |
$$ | . O O O X . X O . . . . . . . . . . . |
$$ | O X X O X . O O . O O O O O O O . . . |
$$ | . X . X O O . X X O X X O X X . O O . |
$$ | X . . X . . . O X X . X X . . X O X . |
$$ | . X X . . . . . . . . . . X X . X . . |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$Wcm139
$$ ---------------------------------------
$$ | 3 . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . X . O . . . . . O . 5 . |
$$ | . X . X . . X . X O . . . . . . O 4 . |
$$ | . O X , . . X X O , . X . . O O X 1 . |
$$ | O . O X . . . O . O . . . O X . X 2 . |
$$ | . O O O X . . . O . . O . O X . X . . |
$$ | . . O . X . . . . . . . . O X O . . . |
$$ | . . . O X . . . . . . . . . X . . . . |
$$ | . . . O X . . . . . . . X . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . O O . . X . . X X . X X X X . |
$$ | . . . . O X . . . X X O . . O X O X . |
$$ | O . X O X . . X X O O . X . . O O O . |
$$ | . O O O X . X O . . . . . . . . . . . |
$$ | O X X O X . O O . O O O O O O O . . . |
$$ | . X . X O O . X X O X X O X X . O O . |
$$ | X . . X . . . O X X . X X . . X O X . |
$$ | . X X . . . . . . . . . . X X . X . . |
$$ ---------------------------------------[/go]

Author:  Joaz Banbeck [ Mon Dec 03, 2012 9:14 am ]
Post subject:  Re: understanding endgame tesuji from Lee Sedol's game

The important point here for kyu players is that A19 is usually a bad move.

Author:  xed_over [ Mon Dec 03, 2012 10:28 am ]
Post subject:  Re: understanding endgame tesuji from Lee Sedol's game

thanks guys.

I think logan's diagrams illustrate what Herman says, but it will take me some time to digest this, as its still not immediately obvious to me.

Author:  mitsun [ Mon Dec 03, 2012 12:08 pm ]
Post subject:  Re: understanding endgame tesuji from Lee Sedol's game

I will admit that I do not fully understand this play either :)

B presumably wants sente to play elsewhere, after first limiting the damage W can do locally with another move. For this purpose, the cut is a nice tesuji.

But suppose B simply blocks without cutting. If W answers, B gets sente anyway, and the cut tesuji is not needed and accomplishes nothing. So is B worried that W will not connect if he blocks? But in this case, the initial W hane would have gained nothing compared to W simply playing elsewhere directly. Maybe I am missing some tiny gain W makes by playing the hane in sente, then not connecting after B blocks.

Apart from that possibility, the only scenario I see where the cut tesuji is better than simply blocking, is if B feels that the W hane was too small, but if he blocks, W will realize his mistake and switch elsewhere.

Author:  Alguien [ Tue Dec 04, 2012 12:29 am ]
Post subject:  Re: understanding endgame tesuji from Lee Sedol's game

logan wrote:
*diagrams*


I wish everything was explained in this way.

Author:  Marcel GrĂ¼nauer [ Tue Dec 04, 2012 2:31 am ]
Post subject:  Re: understanding endgame tesuji from Lee Sedol's game

mitsun wrote:
But suppose B simply blocks without cutting. If W answers, B gets sente anyway, and the cut tesuji is not needed and accomplishes nothing.


I guess cutting first has a stronger follow-up (at the 2-2 point).

Author:  Uberdude [ Tue Dec 04, 2012 4:19 am ]
Post subject:  Re: understanding endgame tesuji from Lee Sedol's game

mitsun wrote:
But suppose B simply blocks without cutting. If W answers, B gets sente anyway, and the cut tesuji is not needed and accomplishes nothing. So is B worried that W will not connect if he blocks? But in this case, the initial W hane would have gained nothing compared to W simply playing elsewhere directly. Maybe I am missing some tiny gain W makes by playing the hane in sente, then not connecting after B blocks.


Yes, if W doesn't hane then black may be able to play sagari at s16 and first line hane connect in sente in that corner, the hane block exchange means black only has gote yose. In this example the white territory behind is fairly small so my feeling is it will be hard to find a time black can reasonably get this in sente, but if the territory is bigger putting in the hane for block exchange can be a very important endgame tesuji. In fact the failure to do this cost Vanessa Wong, the UK representative, a medal in the Women's individual competition at the 2nd World Mind Sports Games: there were various mistakes beforehand, but the pro commentary was that the game was over once white descended to e18 on move 118, black should have made the e18 f18 exchange earlier and then could have won the yose.


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