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1000 year ko
http://lifein19x19.com/viewtopic.php?f=10&t=14157		 Page 1 of 1
Author:  drieger [ Sun Apr 09, 2017 7:10 am ]
Post subject:  1000 year ko
Hi. I recently found myself in a 1000-year ko on IGS. I could not figure out how to conclude the game and eventually suggested that one of us resign, followed by an accepted new game challenge, followed by 4 moves, followed by the other person resigning. Is there a proper way to recognize a gigo?
Author:  Schachus [ Sun Apr 09, 2017 7:17 am ]
Post subject:  Re: 1000 year ko
What? no...
In a 10000-year ko, if neither player wants to play a ko then usually either one can make seki. At least when there is nothing else on the board, there is one one player who will hapily make seki, because it wins the game for him(so if there is really nothing else left, maybe the other one should have made a disadvantegous ko.., better then just losing, usually it would be resolved a little(but not much) earlier). This is not like triple ko..
Author:  BlindGroup [ Sun Apr 09, 2017 9:10 am ]
Post subject:  Re: 1000 year ko
I played a game last night with a 1000 year ko. I think my opponent played it properly. So, maybe this might be a useful example. The game was on KGS and my opponent was ranked as 7k. However, the rank was brand new, and he was just getting back into go after a long hiatus. So, I suspect he's probably a bit stronger than 7k. He seemed to make two big mistakes (got away with one...) in the fuseki, but otherwise, he dominated me.

Here are the key moves:
Move 127: He starts harassing my L+2 group, and as I often do, I misplay a position that I know well.
Move 135: He establishes a 1000 year ko. As Schachus notes, opponent can create the ko by playing at S19 or convert to seki by playing T19. I can also start the ko by playing T19, but I can't force seki.
Move 265: Opponents initiates ko fight since I'm not short on ko threats.
Move 288: I run out of ko threats and lose the group after the next move.



Attachments:
2017-04-09 1000 year ko.sgf [4.88 KiB]
Downloaded 619 times
Author:  Schachus [ Sun Apr 09, 2017 10:03 am ]
Post subject:  Re: 1000 year ko
I'm sorry to say that, but I think you(and your opponent) misread the L+D there. THis is not in fact a 10000-year ko, because your opponents play at t19 does not make seki, but it kills your corner in a bent four in the corner shape. So this is what he should have done instead of starting the ko(at least under japanese rules, under chinese he will have play a ko in the end to prove that bent 4 in the corner is dead).
Author:  BlindGroup [ Sun Apr 09, 2017 10:09 am ]
Post subject:  Re: 1000 year ko
Schachus wrote:
I'm sorry to say that, but I think you(and your opponent) misread the L+D there. THis is not in fact a 10000-year ko, because your opponents play at t19 does not make seki, but it kills your corner in a bent four in the corner shape. So this is what he should have done instead of starting the ko(at least under japanese rules, under chinese he will have play a ko in the end to prove that bent 4 in the corner is dead).


Good to know. Thanks for correcting me. Not familiar with this, but will take a look. That said, I guess I was dead either way...
Author:  Bill Spight [ Sun Apr 09, 2017 10:29 am ]
Post subject:  Re: 1000 year ko
Before we get to the position in question:

Click Here To Show Diagram Code
[go]$$Bc Move 127 Variation
$$ ---------------------------------------
$$ | . . . . . . . X 1 . . . . . . . . . . |
$$ | . . O O . O O X O . . . O . X O O . . |
$$ | . . X . . O X X O O O O O X . X O . . |
$$ | . . . X . O X O . O X X O X . X O O . |
$$ | . . . . . O X X O X X O X X . O X O . |
$$ | . . X . . . . . X . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . X . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . O . O . . |
$$ | . . . , . . X . . , . . . . . , . . . |
$$ | . . . . . X O O O . O . . . . . . . . |
$$ | . . . . . X O . O X . . . . . . . . . |
$$ | . . . X . X O O X O O . . X O O O O . |
$$ | . . X O O X X X X X O . . X X X X X . |
$$ | . . X . . . . X O O X X . . . . X O . |
$$ | . . O O . . X O . O O O . . . O O X . |
$$ | . . . . O . X O O . . . . O O . O X . |
$$ | . . . . . X . X O . . . . . . X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Black might have done well to play B 127 here. :)

Click Here To Show Diagram Code
[go]$$Bc Move 135: Not 10,000 year ko
$$ ---------------------------------------
$$ | . . . . . . . X . . . . . . X X O . . |
$$ | . . O O . O O X O . O . O . X O O O 1 |
$$ | . . X . . O X X O O O O O X . X O . X |
$$ | . . . X . O X O . O X X O X . X O O O |
$$ | . . . . . O X X O X X O X X . O X O X |
$$ | . . X . . . . . X . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . X . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . O . O . . |
$$ | . . . , . . X . . , . . . . . , . . . |
$$ | . . . . . X O O O . O . . . . . . . . |
$$ | . . . . . X O . O X . . . . . . . . . |
$$ | . . . X . X O O X O O . . X O O O O . |
$$ | . . X O O X X X X X O . . X X X X X . |
$$ | . . X . . . . X O O X X . . . . X O . |
$$ | . . O O . . X O . O O O . . . O O X . |
$$ | . . . . O . X O O . . . . O O . O X . |
$$ | . . . . . X . X O . . . . . . X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


This is not a 10,000 year ko.

Click Here To Show Diagram Code
[go]$$Wc White throw-in ko
$$ ---------------------------------------
$$ | . . . . . . . X . . . . . . X X O . 1 |
$$ | . . O O . O O X O . O . O . X O O O X |
$$ | . . X . . O X X O O O O O X . X O . X |
$$ | . . . X . O X O . O X X O X . X O O O |
$$ | . . . . . O X X O X X O X X . O X O X |
$$ | . . X . . . . . X . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . X . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . O . O . . |
$$ | . . . , . . X . . , . . . . . , . . . |
$$ | . . . . . X O O O . O . . . . . . . . |
$$ | . . . . . X O . O X . . . . . . . . . |
$$ | . . . X . X O O X O O . . X O O O O . |
$$ | . . X O O X X X X X O . . X X X X X . |
$$ | . . X . . . . X O O X X . . . . X O . |
$$ | . . O O . . X O . O O O . . . O O X . |
$$ | . . . . O . X O O . . . . O O . O X . |
$$ | . . . . . X . X O . . . . . . X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


White can play a throw-in to make a ko.

Click Here To Show Diagram Code
[go]$$Bc Bent four in the corner
$$ ---------------------------------------
$$ | . . . . . . . X . . . . . . X X O . 1 |
$$ | . . O O . O O X O . O . O . X O O O X |
$$ | . . X . . O X X O O O O O X . X O . X |
$$ | . . . X . O X O . O X X O X . X O O O |
$$ | . . . . . O X X O X X O X X . O X O X |
$$ | . . X . . . . . X . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . X . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . O . O . . |
$$ | . . . , . . X . . , . . . . . , . . . |
$$ | . . . . . X O O O . O . . . . . . . . |
$$ | . . . . . X O . O X . . . . . . . . . |
$$ | . . . X . X O O X O O . . X O O O O . |
$$ | . . X O O X X X X X O . . X X X X X . |
$$ | . . X . . . . X O O X X . . . . X O . |
$$ | . . O O . . X O . O O O . . . O O X . |
$$ | . . . . O . X O O . . . . O O . O X . |
$$ | . . . . . X . X O . . . . . . X X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Or Black can kill with Bent Four in the Corner. :)

As Schachus pointed out.

Edit: BTW, Black 135 is a middling endgame play. It can wait.

Also:

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


:b1:, to make ko in the corner, is a large endgame play. It is better than Black 131 in the game, but it would still have been premature.
Author:  Bill Spight [ Sun Apr 09, 2017 10:32 am ]
Post subject:  Re: 1000 year ko
Schachus wrote:
I'm sorry to say that, but I think you(and your opponent) misread the L+D there. THis is not in fact a 10000-year ko, because your opponents play at t19 does not make seki, but it kills your corner in a bent four in the corner shape. So this is what he should have done instead of starting the ko(at least under japanese rules, under chinese he will have play a ko in the end to prove that bent 4 in the corner is dead).


Under Chinese rules he can remove ko threats before playing either of the two kos involved. :)
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