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Pretty cool endgame problem
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Author:  Bill Spight [ Mon Apr 26, 2010 9:57 am ]
Post subject:  Pretty cool endgame problem
The SGF shows a cool endgame problem from the Gokyo Seimyo, based on play in one of Jowa's games. Black to play.



To see the original, cool play by both sides, just play through the file.

My question is, "What is Black's play in the variation for W2?"

Enjoy!
Author:  fwiffo [ Mon Apr 26, 2010 10:56 am ]
Post subject:  Re: Pretty cool endgame problem
Click Here To Show Diagram Code
[go]$$B Ko
$$ | . . . . .
$$ | X X X , .
$$ | 4 O X . .
$$ | 3 O O X .
$$ | . 5 O X .
$$ | X . O X .
$$ | 1 O O X .
$$ | O X X O .
$$ | 2 . . O .
$$ | . O . . .
$$ | . . . . .
$$ ---------[/go]

Click Here To Show Diagram Code
[go]$$B Throw-in not working anymore
$$ | . . . . .
$$ | X X X , .
$$ | a O X . .
$$ | 3 O O X .
$$ | 4 5 O X .
$$ | X b O X .
$$ | 1 O O X .
$$ | O X X O .
$$ | 2 . . O .
$$ | . O . . .
$$ | . . . . .
$$ ---------[/go]
Author:  Bill Spight [ Mon Apr 26, 2010 12:29 pm ]
Post subject:  Re: Pretty cool endgame problem
fwiffo wrote:
Click Here To Show Diagram Code
[go]$$B Ko
$$ | . . . . .
$$ | X X X , .
$$ | 4 O X . .
$$ | 3 O O X .
$$ | . 5 O X .
$$ | X . O X .
$$ | 1 O O X .
$$ | O X X O .
$$ | 2 . . O .
$$ | . O . . .
$$ | . . . . .
$$ ---------[/go]

Click Here To Show Diagram Code
[go]$$B Throw-in not working anymore
$$ | . . . . .
$$ | X X X , .
$$ | a O X . .
$$ | 3 O O X .
$$ | 4 5 O X .
$$ | X b O X .
$$ | 1 O O X .
$$ | O X X O .
$$ | 2 . . O .
$$ | . O . . .
$$ | . . . . .
$$ ---------[/go]


White can do better. :)
Author:  Bill Spight [ Tue Apr 27, 2010 9:40 am ]
Post subject:  Pretty cool subproblem
Hmmm. Not a lot of people are jumping on this problem. So here is an easier subproblem:



What is White's play after this Black response in the variation?

:)
Author:  quantumf [ Tue Apr 27, 2010 10:06 am ]
Post subject:  Re: Pretty cool endgame problem
White A7

No real defence: If Black A3, White B6, and then lives at A9, or, if black approaches at A9, then white captures the two stones, and if black captures back, white plays B3
Author:  Bill Spight [ Tue Apr 27, 2010 11:29 am ]
Post subject:  Re: Pretty cool endgame problem
quantumf wrote:
White A7

No real defence: If Black A3, White B6, and then lives at A9, or, if black approaches at A9, then white captures the two stones, and if black captures back, white plays B3


White can do better. :)
Author:  MountainGo [ Tue Apr 27, 2010 2:52 pm ]
Post subject:  Re: Pretty cool endgame problem
quantumf wrote:
White A7

No real defence: If Black A3, White B6, and then lives at A9, or, if black approaches at A9, then white captures the two stones, and if black captures back, white plays B3
If Black A3, White can just A9, which gets a couple more points. So Black won't play A3 but rather A9 immediately, which forces White to capture two.
Bill Spight wrote:
White can do better. :)
I continue to be stumped on this, though...
Author:  Bill Spight [ Tue Apr 27, 2010 3:01 pm ]
Post subject:  Re: Pretty cool endgame problem
MountainGo wrote:
quantumf wrote:
White A7

No real defence: If Black A3, White B6, and then lives at A9, or, if black approaches at A9, then white captures the two stones, and if black captures back, white plays B3
If Black A3, White can just A9, which gets a couple more points. So Black won't play A3 but rather A9 immediately, which forces White to capture two.
Bill Spight wrote:
White can do better. :)
I continue to be stumped on this, though...


No, you got it right. if B A-03, W A-09, not W B-06. That's how White does better. :)
Author:  gonut [ Tue Apr 27, 2010 3:29 pm ]
Post subject:  Re: Pretty cool endgame problem
Bill,

Great problem! I obviously don't know the correct answer to your question, because your White move seems to be better than the actual game. And a master wouldn't misplay an endgame, right?

In any event, here's my analysis, which in addition to $5 will get you a latte at a Starbucks:

[sgf-full](;
AB[aj][bj][cj][ck][dl][dm][dn][do][cp][bp]
AW[bk][bl][cl][cm][cn][co][bo][dp][dq][br];
B[an]
(;
W[ao]
C[The actual game.];
B[al];W[am];B[bm];W[bn];B[ak];W[am]
)
(;
W[ap]
C[Bill Spight's question: Black's response?]
(;
B[ao]
C[Best for Black.]
(;
W[am]
C[Best]
(;
B[ak]
C[Sente];
W[bn];B[al]
C[At the end of the game, Black may be able to take another point here. But Black is still a half point worse than in the actual game?]
)
(;
B[aq]
C[A mistake];
W[ak]
C[Black cannot avoid a shortage of liberties.];
B[bn];W[bq];B[ap];W[ar]
)
)
(;
W[bq]
C[Inferior];
B[aq];W[am];B[ak];W[bn];B[al]
C[Black pushes again in sente.]
)
(;
W[ak]
C[A mistake];
B[bm]
C[Black has a seki or a ko.]
)
(;
W[al]
C[A mistake];
B[aq];W[bq];B[ak];W[cq];B[ap];W[ar];B[bn]
C[Seki]
)
(;
W[aq]
C[A mistake.];
B[al]
C[Black has a ko.]
)
)
(;
B[ak]
C[2nd best for Black, but still one point worse for Black than the actual game.];
W[al]
C[Black does end in sente.];
B[aq]
C[Black cannot do any better.];
W[ao]
C[White is safe.]
)
(;
B[aq]
C[Fails];
W[ak]
C[Correct];
B[ao];W[am];B[bn];W[bq];B[ap];W[ar]
)
(;
B[al]
C[Fails];
W[ak]
(;
B[aq];W[am]
)
(;
B[bm];W[bq]
)
(;
B[ao];W[am];B[aq];W[bn]
)
)
)
)[/sgf-full]
Author:  Bill Spight [ Tue Apr 27, 2010 10:52 pm ]
Post subject:  Re: Pretty cool endgame problem
gonut wrote:
Bill,

Great problem! I obviously don't know the correct answer to your question, because your White move seems to be better than the actual game. And a master wouldn't misplay an endgame, right?

In any event, here's my analysis, which in addition to $5 will get you a latte at a Starbucks:



Yes, for a while I thought that I had found a better move. ;)



BTW, gonut, are you counting zi? :)
Author:  gonut [ Wed Apr 28, 2010 5:03 am ]
Post subject:  Re: Pretty cool endgame problem
Bill,

Doesn't my SGF above show the refutation of your most recent variation for Black? Viz., after the end of your variation, doesn't White A7 kill all the Black corner stones by keeping the Black stones in a shortage of liberties?

What am I missing?
Please be sure to type slow, I'm old.

And what is "zi"? (I don't really go to Starbucks.)

Myron
Author:  topazg [ Wed Apr 28, 2010 5:11 am ]
Post subject:  Re: Pretty cool endgame problem
gonut wrote:
Bill,

Doesn't my SGF above show the refutation of your most recent variation for Black? Viz., after the end of your variation, doesn't White A7 kill all the Black corner stones by keeping the Black stones in a shortage of liberties?

What am I missing?
Please be sure to type slow, I'm old.

And what is "zi"? (I don't really go to Starbucks.)

Myron


I think Black at B7 instead of capturing at A5 is Bill's point ?
Author:  Bill Spight [ Wed Apr 28, 2010 6:32 am ]
Post subject:  Re: Pretty cool endgame problem
gonut wrote:
Bill,

Doesn't my SGF above show the refutation of your most recent variation for Black? Viz., after the end of your variation, doesn't White A7 kill all the Black corner stones by keeping the Black stones in a shortage of liberties?


Sorry for not being clear. I meant that Black has a better move than the last one.

Quote:
And what is "zi"? (I don't really go to Starbucks.)

Myron


Myron, I thought that you might be using the Chinese style of counting only Black area. :)
Author:  Bill Spight [ Wed Apr 28, 2010 6:46 am ]
Post subject:  Re: Pretty cool endgame problem
topazg wrote:
I think Black at B7 instead of capturing at A5 is Bill's point ?


Yes. :)

This ko is lurking in the main line, as well. E. g., B A-06, W A-09, B B-07, W A-07. ;) If White is komaster, White can play that way. But then Black will not start at A-06, either.
Author:  gonut [ Wed Apr 28, 2010 8:06 am ]
Post subject:  Re: Pretty cool endgame problem
Bill Spight wrote:
topazg wrote:
I think Black at B7 instead of capturing at A5 is Bill's point ?


Yes. :)

This ko is lurking in the main line, as well. E. g., B A-06, W A-09, B B-07, W A-07. ;) If White is komaster, White can play that way. But then Black will not start at A-06, either.


Ah! Now I understand.
Thanks!
Author:  Bill Spight [ Wed Apr 28, 2010 11:21 am ]
Post subject:  Subproblem solution
gonuts solved the subproblem. :)



White gets one point more in this variation than in the main variation. :)
Author:  Bill Spight [ Wed Apr 28, 2010 11:28 am ]
Post subject:  Subproblem 2


What is White's play after :b3: in the variation?
Author:  gonut [ Fri Apr 30, 2010 6:11 am ]
Post subject:  Re: Pretty cool endgame problem
Endgames are the worst part of my game, except for joseki, fuseki, middle game, yose, and tsumego. But here goes an attempt to answer Bill's last question anyway...

[sgf-full](;
AB[aj][bj][cj][ck][dl][dm][dn][do][cp][bp][an][aq]
AW[bk][bl][cl][cm][cn][co][bo][dp][dq][br][ap]
(;
W[am]
C[May be best, but depends on the rest of the board?];
B[ak];W[bn];B[al]
C[Black ends in sente.]
)
(;
W[ao]
C[Another possibility.];
B[al]
C[White loses 3 points relative to the main line, and later loses 2 more points capturing the A3 stone. But Black ends in gote.

So this line would be better for White, given at least a 5 point play elsewhere.]
)
)[/sgf-full]
Author:  Bill Spight [ Fri Apr 30, 2010 7:39 am ]
Post subject:  Re: Pretty cool endgame problem
gonuts has solved this subproblem too. :)

I have added some comments to his SGF file.



And that means that, along with his earlier work, gonuts has solved the original problem, as well. :) Correct play for Black in it is the atari at A-03, which yields this subproblem.

The end result is the same as in the main line in Gokyo Seimyo, so I did not find an improvement. And that line is cool for both players. However, I thought that the atari (A-03) was pretty cool. The cut (A-05), while it looks natural, loses a dame and, hence, 1 point by comparison. :)
Author:  Harleqin [ Sun May 02, 2010 10:21 am ]
Post subject:  Re: Pretty cool endgame problem
[sgf-full](;AP[another subproblem]CA[ISO8859-1]ST[2]FF[4]SZ[19]GM[1]PB[ ]AB[aj][bj][cj][ck][dl][dm][dn][do][cp][bp]FG[259:]AW[bk][bl][cl][cm][cn][co][bo][dp][dq][br]PW[ ]PM[2]GN[ ]
;B[an]
(;W[am]))[/sgf-full]

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