cutting problem

[Kirby]

...
I don't think that exchange is good for black...

Could you explain why? It's possible that you are correct, but it would seem that the OP's variation is superior to the book's variation if the exchange is bad for black.

To me, the difference between the two end positions seems small.

But it would seem odd to me that a problem solution, presumably given by a pro, would not have the optimal line of play. That's why I'm guessing here that the given solution is better in terms of haengma or endgame or something. Otherwise, why not use the OP's solution in the book?

[illluck]

...
I don't think that exchange is good for black...

Could you explain why? It's possible that you are correct, but it would seem that the OP's variation is superior to the book's variation if the exchange is bad for black.

To me, the difference between the two end positions seems small.

But it would seem odd to me that a problem solution, presumably given by a pro, would not have the optimal line of play. That's why I'm guessing here that the given solution is better in terms of haengma or endgame or something. Otherwise, why not use the OP's solution in the book?

Typing on ipad mini, so not going to elaborate too much (especially since as you said the difference is quite minute and I'm not fully sure. My thinking is that it's hard to imagine that double peep stone being useful and that exchange loses at least a ko threat.

My guess is that the solution in book is given because it most clearly demonstrates the key idea.

p.s. While we are talking about pro comments, I suddenly remembered that I had a question a long time ago about a pro lecture that was never answered at http://www.lifein19x19.com/forum/viewto ... 52#p101952 The video is at http://eurogotv.com/index.php?menu=Vide ... AeECADmHmc Apologies to cherryhill for derailment XD

[Kirby]

Fair enough, illluck. I am personally still not sure what to believe. Even if it were for pedagogical reasons, I'm surprised that a solution to a pro's problem would be sub-optimal. But as I think we both agree, the benefit of the exchange in the pro's variation is not clear to us (or at least not from the comments people have left thus far).

So for now, I'll just scratch my head on this one...

[ez4u]

It is true that either play will cut. However, it is not correct to think that White will go ahead and play out the situation at this time. Consider the implications of in the two diagrams below. White waits to see whether this can turn into an important play in the center. The exchange of the marked stones in the first diagram eliminates any aji here. It is indeed the better sequence.

$$Wc If Black has to answer in the center 1
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . 2 . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . 1 . . . . . . . . . . |
$$ | . . . X . O . . . X . . . . . . . . . |
$$ | . . . X . W B . X . . . . . . . . . . |
$$ | . . . X . O 6 O X . . . . . . . . . . |
$$ | . . . X 4 X 3 X X , . . . . . , . . . |
$$ | . . . X . O 5 . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Wc If Black has to answer in the center 1
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . 2 . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . 1 . . . . . . . . . . |
$$ | . . . X . O . . . X . . . . . . . . . |
$$ | . . . X . W B . X . . . . . . . . . . |
$$ | . . . X . O 6 O X . . . . . . . . . . |
$$ | . . . X 4 X 3 X X , . . . . . , . . . |
$$ | . . . X . O 5 . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

$$Wc If Black has to answer in the center 2
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . 2 . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . 1 . . . . . . . . . . |
$$ | . . . X . O a 0 c X . . . . . . . . . |
$$ | . . . X b 8 6 9 X . . . . . . . . . . |
$$ | . . . X . O 7 O X . . . . . . . . . . |
$$ | . . . X 4 X 3 X X , . . . . . , . . . |
$$ | . . . X . O 5 . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Wc If Black has to answer in the center 2
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . 2 . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . 1 . . . . . . . . . . |
$$ | . . . X . O a 0 c X . . . . . . . . . |
$$ | . . . X b 8 6 9 X . . . . . . . . . . |
$$ | . . . X . O 7 O X . . . . . . . . . . |
$$ | . . . X 4 X 3 X X , . . . . . , . . . |
$$ | . . . X . O 5 . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

[paK0]

Fair enough, illluck. I am personally still not sure what to believe. Even if it were for pedagogical reasons, I'm surprised that a solution to a pro's problem would be sub-optimal.

Its probably common that go books have tons of mistakes, regardless of the author. A ton of chess books that were written before the time that computers got this strong got updates in their more recent versions because they contained unsound lines that were thought to be correct.

[Kirby]

Fair enough, illluck. I am personally still not sure what to believe. Even if it were for pedagogical reasons, I'm surprised that a solution to a pro's problem would be sub-optimal.

Its probably common that go books have tons of mistakes, regardless of the author. A ton of chess books that were written before the time that computers got this strong got updates in their more recent versions because they contained unsound lines that were thought to be correct.

Agreed, but I feel it is more likely that we, as amateurs, missed something

[illluck]

It is true that either play will cut. However, it is not correct to think that White will go ahead and play out the situation at this time. Consider the implications of in the two diagrams below. White waits to see whether this can turn into an important play in the center. The exchange of the marked stones in the first diagram eliminates any aji here. It is indeed the better sequence.

$$Wc If Black has to answer in the center 1
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . 2 . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . 1 . . . . . . . . . . |
$$ | . . . X . O . . . X . . . . . . . . . |
$$ | . . . X . W B . X . . . . . . . . . . |
$$ | . . . X . O 6 O X . . . . . . . . . . |
$$ | . . . X 4 X 3 X X , . . . . . , . . . |
$$ | . . . X . O 5 . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Wc If Black has to answer in the center 1
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . 2 . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . 1 . . . . . . . . . . |
$$ | . . . X . O . . . X . . . . . . . . . |
$$ | . . . X . W B . X . . . . . . . . . . |
$$ | . . . X . O 6 O X . . . . . . . . . . |
$$ | . . . X 4 X 3 X X , . . . . . , . . . |
$$ | . . . X . O 5 . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

$$Wc If Black has to answer in the center 2
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . 2 . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . 1 . . . . . . . . . . |
$$ | . . . X . O a 0 c X . . . . . . . . . |
$$ | . . . X b 8 6 9 X . . . . . . . . . . |
$$ | . . . X . O 7 O X . . . . . . . . . . |
$$ | . . . X 4 X 3 X X , . . . . . , . . . |
$$ | . . . X . O 5 . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------

Click Here To Show Diagram Code

[go]$$Wc If Black has to answer in the center 2
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . 2 . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . 1 . . . . . . . . . . |
$$ | . . . X . O a 0 c X . . . . . . . . . |
$$ | . . . X b 8 6 9 X . . . . . . . . . . |
$$ | . . . X . O 7 O X . . . . . . . . . . |
$$ | . . . X 4 X 3 X X , . . . . . , . . . |
$$ | . . . X . O 5 . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Sure, but then the double peep doesn't have to be answered either and that aji still remains. Though the double peep does threaten a slightly bigger capture.

[Kirby]

Thanks for the diagrams, ez4u. I think that your explanation at least gives one example where the first variation makes more sense.