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 Post subject: Semeai
Post #1 Posted: Wed May 04, 2011 12:14 pm 
Honinbo

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Click Here To Show Diagram Code
[go]$$Bc Black to play
$$ ----------------------
$$ | . O . O . . . O . . .
$$ | X X O X X X X O X . .
$$ | . X O O X . . . O O .
$$ | O O O O X . O . X O .
$$ | O X X O X O X . X O .
$$ | . . X . X O . . . . .
$$ | . X . X X O . . . . .
$$ | . O O O X O . . . . .
$$ | . . . . O O . . . . .
$$ | . . . O . . . . . , .
$$ | . . . . . . . . . . .[/go]


A little test of reading skill. :)

Enjoy!

[admin]
Added numbers. Hope nobody minds. -JB
[/admin]

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 Post subject: Re: Semeai
Post #2 Posted: Wed May 04, 2011 12:22 pm 
Oza

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The famous Go Seigen-Fujisawa catastrophe! Now that's what I call not dumbing down :)

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 Post subject: Re: Semeai
Post #3 Posted: Thu May 05, 2011 2:09 am 
Gosei
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The obvious approach seems to be :b1: below...

Click Here To Show Diagram Code
[go]$$B :w8: @ :wc:, :b9: @ :w4:, :w10: @ :b7:
$$ ----------------------
$$ | . O 7 W 4 5 . O . . .
$$ | X X O X X X X O X . .
$$ | . X O O X . . . O O .
$$ | O O O O X . O . X O .
$$ | O X X O X O X . X O .
$$ | 1 . X 3 X O . . . . .
$$ | . X 2 X X O . . . . .
$$ | 6 O O O X O . . . . .
$$ | . . . . O O . . . . .
$$ | . . . O . . . . . , .
$$ | . . . . . . . . . . .[/go]


Now black is losing the semeai

Click Here To Show Diagram Code
[go]$$Bm11 :b13:, :b17:, :b19: @ the :bc: marked points, :w20: @ :b11:
$$ ----------------------
$$ | 2 O O O X X 8 O . . .
$$ | B B O X X X X O X . .
$$ | 1 B O O X . 6 . O O .
$$ | O O O O X . O . X O .
$$ | O X X O X O X . X O .
$$ | X 5 X X X O . . . . .
$$ | 4 X O X X O . . . . .
$$ | O O O O X O . . . . .
$$ | . . . . O O . . . . .
$$ | . . . O . . . . . , .
$$ | . . . . . . . . . . .[/go]


After white captures, he is ahead by one liberty

The alternative is to play :b1: like this:

Click Here To Show Diagram Code
[go]$$B Black to play
$$ ----------------------
$$ | . O . O 1 . . O . . .
$$ | X X O X X X X O X 6 .
$$ | . X O O X . 3 5 O O .
$$ | O O O O X 4 O 7 X O .
$$ | O X X O X O X . X O .
$$ | . . X . X O . . 8 . .
$$ | 2 X . X X O . . . . .
$$ | . O O O X O . . . . .
$$ | . . . . O O . . . . .
$$ | . . . O . . . . . , .
$$ | . . . . . . . . . . .[/go]


White connects under with :w2:, then with :w4: and :w6: prevents black from making two eyes, allowing black to connect out, sealing him in again with :w8:

Now, unless black has some serious support on the outside, he seems dead to me.

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 Post subject: Re: Semeai
Post #4 Posted: Thu May 05, 2011 9:21 am 
Dies in gote

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HermanHiddema wrote:
The obvious approach seems to be :b1: below...
<snip>


I got :b1: as well, but a different sequence to give black at least a ko for life. Not capturing at 6 seems to be the key.

Click Here To Show Diagram Code
[go]$$B Black to play
$$ ----------------------
$$ | 8 O . O 4 5 . O . . .
$$ | X X O X X X X O X . .
$$ | 7 X O O X . . . O O .
$$ | O O O O X . O . X O .
$$ | O X X O X O X . X O .
$$ | 1 . X 3 X O . . . . .
$$ | . X 2 X X O . . . . .
$$ | 6 O O O X O . . . . .
$$ | . . . . O O . . . . .
$$ | . . . O . . . . . , .
$$ | . . . . . . . . . . .[/go]


Click Here To Show Diagram Code
[go]$$B Black to play
$$ ----------------------
$$ | O O 6 O O X . O . . .
$$ | 5 1 O X X X X O X . .
$$ | 8 7 O O X . . . O O .
$$ | O O O O X 4 O . X O .
$$ | O X X O X O X . X O .
$$ | X 3 X X X O . . . . .
$$ | 2 X O X X O . . . . .
$$ | O O O O X O . . . . .
$$ | . . . . O O . . . . .
$$ | . . . O . . . . . , .
$$ | . . . . . . . . . . .[/go]


9 @ 1, now W has 2 libs and B has 3. So W cannot play this way.

Click Here To Show Diagram Code
[go]$$B Seki
$$ ----------------------
$$ | O O 7 W O X . O . . .
$$ | 2 1 O X X X X O X . .
$$ | . 9 O O X . 3 4 O O .
$$ | O O O O X 5 O 6 X O .
$$ | O X X O X O X . X O .
$$ | X . X X X O . . . . .
$$ | . X O X X O . . . . .
$$ | O O O O X O . . . . .
$$ | . . . . O O . . . . .
$$ | . . . O . . . . . , .
$$ | . . . . . . . . . . .[/go]


Click Here To Show Diagram Code
[go]$$B Seki is wishful thinking though, this reverts to ko.
$$ ----------------------
$$ | O O 7 W O X . O . . .
$$ | 2 1 O X X X X O X . .
$$ | . 5 O O X . 3 6 O O .
$$ | O O O O X 4 O . X O .
$$ | O X X O X O X . X O .
$$ | X . X X X O . . . . .
$$ | . X O X X O . . . . .
$$ | O O O O X O . . . . .
$$ | . . . . O O . . . . .
$$ | . . . O . . . . . , .
$$ | . . . . . . . . . . .[/go]



Click Here To Show Diagram Code
[go]$$B :w6: at circled stone, B makes ko by playing atari from the outside.
$$ ----------------------
$$ | O O 5 W O X . O . . .
$$ | 2 1 O X X X X O X . .
$$ | . 3 O O X . 4 . O O .
$$ | O O O O X . O . X O .
$$ | O X X O X O X . X O .
$$ | X . X X X O . . . . .
$$ | . X O X X O . . . . .
$$ | O O O O X O . . . . .
$$ | . . . . O O . . . . .
$$ | . . . O . . . . . , .
$$ | . . . . . . . . . . .[/go]


It feels like one should be able to exploit the weakness at h17, though. Maybe it can be used to eliminate ko entirely?

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 Post subject: Re: Semeai
Post #5 Posted: Fri May 06, 2011 4:16 pm 
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One move seems to make Black miai of living and creating an extra outside liberty for the corner semeai.

Because I'm probably incorrect (such is the life of a weak kyu player), I've only included a couple sequences to show the idea.

In any event, thanks for yet another nice problem, Bill!

[sgf-full](;
AB[ab][bb][db][eb][fb][gb][ib][bc][ec][ed][id][be][ce][ee][ge][ie][cf][ef][bg][dg][eg][eh]
AW[ba][da][ha][cb][hb][cc][dc][ic][jc][ad][bd][cd][dd][gd][jd][ae][de][fe][je][ff][fg][bh][ch][dh][fh][ei][fi][dj]
C[Black plays.];
B[hc]
C[This move seems to give Black an extra outside liberty because White needs to spend 2 moves capturing 1 of the 2 singlet Black stones.];
W[jb]
C[White doesn't have time to capture the stone.];
B[fd]
(;
W[he];B[gc];W[gf];B[ga]
C[Black lives.]
)
(;
W[gc];B[hd];W[if];B[fc]
C[Black can make a 2nd eye.]
)
)[/sgf-full]

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 Post subject: Re: Semeai
Post #6 Posted: Fri May 06, 2011 10:11 pm 
Tengen
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gonut wrote:
One move seems to make Black miai of living and creating an extra outside liberty for the corner semeai....


Maybe black exchanges A14 for C13 first, then plays Gonut's sequence...

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 Post subject: Re: Semeai
Post #7 Posted: Fri May 06, 2011 11:18 pm 
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What's wrong with G17 in response to H17? The stone cannot escape capture. Maybe I'm just being thick, but I don't see the benefit of playing this exchange.

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 Post subject: Re: Semeai
Post #8 Posted: Sat May 07, 2011 8:57 pm 
Dies in gote

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Aurik, your refutation is correct! I missed that Black's outside stones would have a shortage of liberties. Ugh.

Anyway, I'll try once more to show what solution theme Bill probably had in mind, and then I'll go hide in a cave.


[sgf-full](;
AB[ab][bb][db][eb][fb][gb][ib][bc][ec][ed][id][be][ce][ee][ge][ie][cf][ef][bg][dg][eg][eh]
AW[ba][da][ha][cb][hb][cc][dc][ic][jc][ad][bd][cd][dd][gd][jd][ae][de][fe][je][ff][fg][bh][ch][dh][fh][ei][fi][dj]
C[Black plays.];
B[af];W[cg];B[df];W[ea];B[fa];W[ah];B[ac];W[aa];B[bb];W[ag];B[bf]
(;
W[ab];B[bc];W[ac];B[bb];W[gc];B[ca];W[da];B[ea]
C[Black takes 1st in a favorable 2-step ko.]
)
(;
W[gc]
C[White cannot win the semeai from the outside.];
B[ab]
C[Atari!];
W[ca];B[bc];W[ac];B[bb]
)
)[/sgf-full]

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 Post subject: Re: Semeai
Post #9 Posted: Mon May 09, 2011 5:13 am 
Lives with ko

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John Fairbairn wrote:
The famous Go Seigen-Fujisawa catastrophe! Now that's what I call not dumbing down :)


What does this mean?

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 Post subject: Re: Semeai
Post #10 Posted: Mon May 09, 2011 12:16 pm 
Oza

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Quote:
What does this mean?


Even leaving metaphysics out of it, I'm not sure what you mean. Is is the reference you don't get, or is "dumbing down" too colloquial for a foreigner?

The reference is that the position comes (with a slight cosmetic change) from Game 1 of the 1951 ten-game match between Go and Fujisawa, and both players - the first 9-dans in history - famously made a mess of getting to this position. The scorekeeper pointed out they had both missed a tesuji. Even in this position, there are extreme difficulties for many amateurs involving a ko and a yoseko. Hence the presenter of this problem is not "dumbing down", i.e. is not offering something for a low level of player.

The full story is in my "9-dan Showdown".

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 Post subject: Re: Semeai
Post #11 Posted: Mon May 09, 2011 1:56 pm 
Lives with ko

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John Fairbairn wrote:
Quote:
What does this mean?


Even leaving metaphysics out of it, I'm not sure what you mean. Is is the reference you don't get, or is "dumbing down" too colloquial for a foreigner?

The reference is that the position comes (with a slight cosmetic change) from Game 1 of the 1951 ten-game match between Go and Fujisawa, and both players - the first 9-dans in history - famously made a mess of getting to this position. The scorekeeper pointed out they had both missed a tesuji. Even in this position, there are extreme difficulties for many amateurs involving a ko and a yoseko. Hence the presenter of this problem is not "dumbing down", i.e. is not offering something for a low level of player.

The full story is in my "9-dan Showdown".


What I mean is: "what do you mean?" if you see what I mean. ;-)

The reference was what I was after - I'm not a foreigner by the way, just a fan of Russian literature.

Story sounds fascinating, 9-dan Showdown is now on my 'to buy' list.

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 Post subject: Re: Semeai
Post #12 Posted: Thu Nov 01, 2018 8:57 am 
Gosei
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Koroviev wrote:
The reference was what I was after - I'm not a foreigner by the way, just a fan of Russian literature.

I don't know what exactly JF would consider a foreigner, but he disapproves using "cookie" for "biscuit"...

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 Post subject: Re: Semeai
Post #13 Posted: Thu Nov 01, 2018 10:02 am 
Lives in gote
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The solution to the semeai problem also appears in Abe Yoshiteru's book "Dramatic Moments On the Go Board".

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 Post subject: Re: Semeai
Post #14 Posted: Thu Nov 01, 2018 12:10 pm 
Honinbo

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I had forgotten about this topic. I should have given a solution.

However, not long after posting this (Edit: in 2011) I underwent an operation for cancer, and not long after that, my wife's (then girlfriend's) brother died suddenly. Not an easy time.

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