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Capture race in Shotwell
Posted: Fri Aug 20, 2010 7:49 pm
by kukula
From Shotwell's
Go! More Than a Game p. 109...
Here is a situation I just don't get:
$$Bc
$$ ----------------
$$ . . . . . . . . |
$$ . . O O X . . . |
$$ . . O X . . . . |
$$ . . O X , X . . |
$$ . O X O 2 4 6 . |
$$ . O X X X 3 5 . |
$$ . X O O X X O . |
$$ . X O O O O O 1 |
$$ . . X O . O X . |
$$ X . X O O X . X |
$$ X . O X X X X . |
$$ . O . O X . . . |
$$ . . . . . . . . |
- Click Here To Show Diagram Code
[go]$$Bc
$$ ----------------
$$ . . . . . . . . |
$$ . . O O X . . . |
$$ . . O X . . . . |
$$ . . O X , X . . |
$$ . O X O 2 4 6 . |
$$ . O X X X 3 5 . |
$$ . X O O X X O . |
$$ . X O O O O O 1 |
$$ . . X O . O X . |
$$ X . X O O X . X |
$$ X . O X X X X . |
$$ . O . O X . . . |
$$ . . . . . . . . |[/go]
The caption reads: "White dies". How so? That black chain with B3 and B5 - it's it atari, right? It is certain a race - that white chain with one eye has just one liberty beyond the eye. But what can black do?
Got to extend to T14 with B7, right? Then why not W8 at T15, so that black group is still in atari. Sure, B9 at T13 would put the big white group in atari, but then W10 at T11 would kill black.
What am I missing?
Thanks!
Re: Capture race in Shotwell
Posted: Fri Aug 20, 2010 8:05 pm
by Dusk Eagle
It seems they made a mistake in the text. It should say, "Black dies". To put things in context for everyone, this is the position in question:
$$Bc
$$ ----------------
$$ . . . . . . . . |
$$ . . O O X . . . |
$$ . . O X . . . . |
$$ . . O X , X . . |
$$ . O X O . . . . |
$$ . O X X X . . . |
$$ . X O O X X W . |
$$ . X O O O O O a |
$$ . . X O . O X O |
$$ X . X O O X . X |
$$ X . O X X X X . |
$$ . O . O X . . . |
$$ . . . . . . . . |
- Click Here To Show Diagram Code
[go]$$Bc
$$ ----------------
$$ . . . . . . . . |
$$ . . O O X . . . |
$$ . . O X . . . . |
$$ . . O X , X . . |
$$ . O X O . . . . |
$$ . O X X X . . . |
$$ . X O O X X W . |
$$ . X O O O O O a |
$$ . . X O . O X O |
$$ X . X O O X . X |
$$ X . O X X X X . |
$$ . O . O X . . . |
$$ . . . . . . . . |[/go]

was just played as a ko threat. If black responds at 'a', finishing the ko, then he loses the [sl=capturingrace]semeai[/sl] as shown in kukula's diagram. So instead, black must play as below, and the ko continues:
$$Bc
$$ ----------------
$$ . . . . . . . . |
$$ . . O O X . . . |
$$ . . O X . . . . |
$$ . . O X , X . . |
$$ . O X O . . . . |
$$ . O X X X . 1 . |
$$ . X O O X X O . |
$$ . X O O O O O . |
$$ . . X O . O X O |
$$ X . X O O X 2 X |
$$ X . O X X X X . |
$$ . O . O X . . . |
$$ . . . . . . . . |
- Click Here To Show Diagram Code
[go]$$Bc
$$ ----------------
$$ . . . . . . . . |
$$ . . O O X . . . |
$$ . . O X . . . . |
$$ . . O X , X . . |
$$ . O X O . . . . |
$$ . O X X X . 1 . |
$$ . X O O X X O . |
$$ . X O O O O O . |
$$ . . X O . O X O |
$$ X . X O O X 2 X |
$$ X . O X X X X . |
$$ . O . O X . . . |
$$ . . . . . . . . |[/go]
Re: Capture race in Shotwell
Posted: Fri Aug 20, 2010 8:17 pm
by kukula
Dusk Eagle wrote: black must play as below,
Ah, right, that's what the text says, black must play as you show, and the variation is given to show why. I.e. if black plays some other way, it must be black that gets hurt. So the text really should say "Black dies"!
Hey, there is hope! I might start understanding little bits of this game!
Thanks again!
Re: Capture race in Shotwell
Posted: Fri Aug 20, 2010 9:23 pm
by xed_over