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Is this corner alive?
Posted: Sun Jun 13, 2010 3:54 am
by blue88
Today I decided to revive an aji corner stone and it worked out quite well leaving me with this position:
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:3]ST[2]
RU[Japanese]SZ[19]KM[0.00]
PW[Weiß]PB[Schwarz]AW[bo][co][do][ep][eq][fq][fr]AB[bp][dq][dr][er]
;B[br])
I could have made a Weak Carpenter's Square with one leg at C4 (as far as I know that shape turns out as seki?) but decided to play 2-2 for unconditional life with points. It worked in the game, but I wonder whether it really is alive.
Re: Is this corner alive?
Posted: Sun Jun 13, 2010 4:02 am
by DrStraw
It is alive after the 2-2. Answer A4 with B3.
Re: Is this corner alive?
Posted: Sun Jun 13, 2010 4:06 am
by blue88
Thanks for your fast answer. I wasn't sure if I had read out all variations and anxiously returned later in the game to spend another move.
Re: Is this corner alive?
Posted: Sun Jun 13, 2010 7:19 am
by cyclops
For fun I tried to kill your shape ( W moving first ) and I found this sequence:
$$Wc next a&b are miai
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . O O O . . .
$$ | . X 2 , O . .
$$ | 4 a . X O O .
$$ | 3 1 5 X X O .
$$ | . 8 6 b 7 9 .
$$ +---------------
- Click Here To Show Diagram Code
[go]$$Wc next a&b are miai
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . O O O . . .
$$ | . X 2 , O . .
$$ | 4 a . X O O .
$$ | 3 1 5 X X O .
$$ | . 8 6 b 7 9 .
$$ +---------------[/go]
Re: Is this corner alive?
Posted: Sun Jun 13, 2010 7:46 am
by Harleqin
You should first explore the simpler starting moves, cyclops.
Re: Is this corner alive?
Posted: Sun Jun 13, 2010 8:20 am
by illluck
The 2-2 point might work, but black 2-3 in response seems hard to handle.
First instinct was the clamp (which works, I think), but then realized that the 1-2 point seems cleaner.
$$Wc A bit easier?
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . O O O . . .
$$ | . X . . O . .
$$ | . . . X O O .
$$ | 1 . . X X O .
$$ | . . . . . . .
$$ +---------------
- Click Here To Show Diagram Code
[go]$$Wc A bit easier?
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . O O O . . .
$$ | . X . . O . .
$$ | . . . X O O .
$$ | 1 . . X X O .
$$ | . . . . . . .
$$ +---------------[/go]
Re: Is this corner alive?
Posted: Sun Jun 13, 2010 8:25 am
by tj86430
Harleqin wrote:You should first explore the simpler starting moves, cyclops.
How about C4?
Re: Is this corner alive?
Posted: Sun Jun 13, 2010 11:28 am
by Dusk Eagle
Just to demonstrate why I belive the clamp works:
$$Wc
$$ | . . . . . . .
$$ | . . . . . . .
$$ | 5 O O O . . .
$$ | 2 X 3 . O . .
$$ | . 1 4 X O O .
$$ | 7 6 . X X O .
$$ | . . . . . . .
$$ +---------------
- Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . .
$$ | . . . . . . .
$$ | 5 O O O . . .
$$ | 2 X 3 . O . .
$$ | . 1 4 X O O .
$$ | 7 6 . X X O .
$$ | . . . . . . .
$$ +---------------[/go]
I believe C4 also works to kill:
$$Wc
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . O O O . . .
$$ | 5 X 1 . O . .
$$ | . 4 2 X O O .
$$ | 6 3 . X X O .
$$ | . 7 . . . . .
$$ +---------------
- Click Here To Show Diagram Code
[go]$$Wc
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . O O O . . .
$$ | 5 X 1 . O . .
$$ | . 4 2 X O O .
$$ | 6 3 . X X O .
$$ | . 7 . . . . .
$$ +---------------[/go]
$$Wc This is NOT seki due to connect-and-die
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . O O O . . .
$$ | 5 X 1 . O . .
$$ | 8 4 2 X O O .
$$ | 7 3 . X X O .
$$ | . 6 . . 9 . .
$$ +---------------
- Click Here To Show Diagram Code
[go]$$Wc This is NOT seki due to connect-and-die
$$ | . . . . . . .
$$ | . . . . . . .
$$ | . O O O . . .
$$ | 5 X 1 . O . .
$$ | 8 4 2 X O O .
$$ | 7 3 . X X O .
$$ | . 6 . . 9 . .
$$ +---------------[/go]
However, if black plays 2-2 before white moves, I see no way for white to kill or make seki.