Life In 19x19 :: Semeai

I got

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]$$B at circled stone, B makes ko by playing atari from the outside. $$ ---------------------- $$ | O O 5 W O X . O . . . $$ | 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?

Author:	Bill Spight [ Wed May 04, 2011 12:14 pm ]
Post subject:	Semeai
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]

Author:	John Fairbairn [ Wed May 04, 2011 12:22 pm ]
Post subject:	Re: Semeai
The famous Go Seigen-Fujisawa catastrophe! Now that's what I call not dumbing down

Author:	HermanHiddema [ Thu May 05, 2011 2:09 am ]
Post subject:	Re: Semeai
The obvious approach seems to be below... Click Here To Show Diagram Code `[go]$$B @ , @ , @ $$ ---------------------- $$ \| . O 7 W 4 5 . O . . . $$ \| 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 , , @ the marked points, @ $$ ---------------------- $$ \| 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 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 , then with and prevents black from making two eyes, allowing black to connect out, sealing him in again with Now, unless black has some serious support on the outside, he seems dead to me.

Author:	aurik [ Thu May 05, 2011 9:21 am ]
Post subject:	Re: Semeai
HermanHiddema wrote: The obvious approach seems to be below... <snip> I got 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]$$B at circled stone, B makes ko by playing atari from the outside. $$ ---------------------- $$ \| O O 5 W O X . O . . . $$ \| 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?

Author:	gonut [ Fri May 06, 2011 4:16 pm ]
Post subject:	Re: Semeai
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]

Life In 19x19 http://lifein19x19.com/

Semeai http://lifein19x19.com/viewtopic.php?f=15&t=3798	Page 1 of 1

Author:	Joaz Banbeck [ Fri May 06, 2011 10:11 pm ]
Post subject:	Re: Semeai
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...

Author:	aurik [ Fri May 06, 2011 11:18 pm ]
Post subject:	Re: Semeai
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.

Author:	gonut [ Sat May 07, 2011 8:57 pm ]
Post subject:	Re: Semeai
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]

Author:	Koroviev [ Mon May 09, 2011 5:13 am ]
Post subject:	Re: Semeai
John Fairbairn wrote: The famous Go Seigen-Fujisawa catastrophe! Now that's what I call not dumbing down What does this mean?

Author:	John Fairbairn [ Mon May 09, 2011 12:16 pm ]
Post subject:	Re: Semeai
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".

Author:	Koroviev [ Mon May 09, 2011 1:56 pm ]
Post subject:	Re: Semeai
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.

Author:	emeraldemon [ Thu Nov 01, 2018 8:57 am ]
Post subject:	Re: Semeai
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"...

Author:	jlt [ Thu Nov 01, 2018 10:02 am ]
Post subject:	Re: Semeai
The solution to the semeai problem also appears in Abe Yoshiteru's book "Dramatic Moments On the Go Board".

Author:	Bill Spight [ Thu Nov 01, 2018 12:10 pm ]
Post subject:	Re: Semeai
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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