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capturing race problem
Posted: Fri May 23, 2014 1:27 am
by macelee
$$W
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . X . O . . . . . . . . . . . . . |
$$ | . . X . X O . . . O . . O . X . . . . |
$$ | . X O O . O . . . , . . . . . X . . . |
$$ | X O O . . . . . . . . . . . . . . . . |
$$ | . X O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . X X . X X X . |
$$ | . . O . . X . . . . . . X O O O X . X |
$$ | . . O . O X . O . . . O . X X O O X . |
$$ | . X X O . . X O . , X O . X O X O O O |
$$ | X . X O . X . O O . X X . X . X O . . |
$$ | . X O O . . X . . X . . X O X . O X X |
$$ | X O . O . X . O O O X X X O X O O O . |
$$ | O O O . . . . O X O O X O O O X X O O |
$$ | . X X X X X X . X O O O . O O . X X X |
$$ | . O . O X O . . X O X X O X O O X . X |
$$ | O X . O O . O O X X X X O . O X X O O |
$$ | . O . . O O X X . . . . X O O O X O O |
$$ | . . . . . . . . . . . X . . . O X X . |
$$ +---------------------------------------+
- Click Here To Show Diagram Code
[go]$$W
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . X . X . O . . . . . . . . . . . . . |
$$ | . . X . X O . . . O . . O . X . . . . |
$$ | . X O O . O . . . , . . . . . X . . . |
$$ | X O O . . . . . . . . . . . . . . . . |
$$ | . X O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . X X . X X X . |
$$ | . . O . . X . . . . . . X O O O X . X |
$$ | . . O . O X . O . . . O . X X O O X . |
$$ | . X X O . . X O . , X O . X O X O O O |
$$ | X . X O . X . O O . X X . X . X O . . |
$$ | . X O O . . X . . X . . X O X . O X X |
$$ | X O . O . X . O O O X X X O X O O O . |
$$ | O O O . . . . O X O O X O O O X X O O |
$$ | . X X X X X X . X O O O . O O . X X X |
$$ | . O . O X O . . X O X X O X O O X . X |
$$ | O X . O O . O O X X X X O . O X X O O |
$$ | . O . . O O X X . . . . X O O O X O O |
$$ | . . . . . . . . . . . X . . . O X X . |
$$ +---------------------------------------+[/go]
This is the end position of a game I just newly added to Go4Go database (
http://www.go4go.net/go/games/sgfview/42035). There is a capturing race at the bottom right corner having two groups with bulky five big eyes. I think this is a very good exercise for beginners.
Re: capturing race problem
Posted: Fri May 23, 2014 2:39 am
by oca
Thanks for posting this example, moves like white 32 kills me so many time...
I went to a situation like this just yesterday... which ended like this...
Re: capturing race problem
Posted: Fri May 23, 2014 4:37 am
by Aidoneus
Doesn't White capture easily? Black's bulky five gives 8 - 4 = 4 liberties, plus 1 outside liberty, for a total of 5 liberties. Black's bulky five gives 8 - 2 = 6 liberties, plus 4 outside liberties (an extra as White must first capture a lone stone to avoid a self atari, yes?), for a total of 10 liberties. Of course, I am a beginner and may be missing something.
Re: capturing race problem
Posted: Fri May 23, 2014 4:45 am
by HermanHiddema
Aidoneus wrote:Doesn't White capture easily? Black's bulky five gives 8 - 4 = 4 liberties, plus 1 outside liberty, for a total of 5 liberties. Black's bulky five gives 8 - 2 = 6 liberties, plus 4 outside liberties (an extra as White must first capture a lone stone to avoid a self atari, yes?), for a total of 10 liberties. Of course, I am a beginner and may be missing something.
Black's shape is not a bulky five (yet). If white plays one stone inside and black captures, only then is it a bulky five (with all its liberties). Black's initial big eye is six spaces, which has 12 approach liberties.
Re: capturing race problem
Posted: Fri May 23, 2014 5:03 am
by Aidoneus
HermanHiddema wrote:Aidoneus wrote:Doesn't White capture easily? Black's bulky five gives 8 - 4 = 4 liberties, plus 1 outside liberty, for a total of 5 liberties. Black's bulky five gives 8 - 2 = 6 liberties, plus 4 outside liberties (an extra as White must first capture a lone stone to avoid a self atari, yes?), for a total of 10 liberties. Of course, I am a beginner and may be missing something.
Black's shape is not a bulky five (yet). If white plays one stone inside and black captures, only then is it a bulky five (with all its liberties). Black's initial big eye is six spaces, which has 12 approach liberties.
Of course, he tricked me! Still 12 - 4 = 8, plus 1 outside for 9 liberties. So White wins, yes?
Edit: I am not awake yet. I meant to type Black must capture the lone White stone before approaching.
Re: capturing race problem
Posted: Fri May 23, 2014 5:11 am
by DrStraw
So how many ko threats does each side have?
Re: capturing race problem
Posted: Fri May 23, 2014 5:23 am
by HermanHiddema
Aidoneus wrote:
Of course, he tricked me! Still 12 - 4 = 8, plus 1 outside for 9 liberties. So White wins, yes?
Yes
Re: capturing race problem
Posted: Fri May 23, 2014 5:24 am
by Aidoneus
DrStraw wrote:So how many ko threats does each side have?
Now I know the problem is over my head!
Re: capturing race problem
Posted: Fri May 23, 2014 5:57 am
by oca
I even don't understand where the 12 number comes from
Re: capturing race problem
Posted: Fri May 23, 2014 6:03 am
by Aidoneus
oca wrote:I even don't understand where the 12 number comes from
See
http://senseis.xmp.net/?BigEyeLiberties
Re: capturing race problem
Posted: Sat May 24, 2014 3:31 pm
by Aidoneus
Another point worth mentioning that I read somewhere was that in races between two groups that each have a big eye, all of the shared liberties belong to the larger big eye. At least I find this sort of heuristic quite useful, and I wish I knew many more!