i was doing this problem from "this is haengma" and i couldn't tell what was wrong with my solution compared to the book's solution. they both seem to cut off the same stone and i cannot refute my own solution even after playing it out on a board so i am wondering what is wrong with it.

variation 1 is the official solution, variation 2 is mine

Your move 4 is wrong. Connect at G3 instead. I am stupid.

but if white connects at g3 with move 4, then if i follow up with g6 i can still cut him. hm i must be making a mistake because i cannot see how g6 doesn't work after g3

Then doesn't G6 still cut?

Oops! Yes, you're both right.

Then black still peeps at G6?

To me it seems that OP got it right, both ways are acceptable ways of cutting.


Oh, and billywoods, I found a hidden tag in your post. What was that all about?

I have no idea what you mean by this...

Does Kim give any comments, either in the Q or the A?

the Q just says, "Cut white with the best sequence".

It might be useful to ask if the marked move gives any benefit to black:

Click Here To Show Diagram Code

[go]$$W
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . . . . . . . . . . . . |
$$ | . . . X . O . . . X . . . . . . . . . |
$$ | . . . X . O B . X . . . . . . . . . . |
$$ | . . . X . O O O X . . . . . . . . . . |
$$ | . . . X X X O X X , . . . . . , . . . |
$$ | . . . X . O X . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Compared with the end sequence in the alternative variation:

Click Here To Show Diagram Code

[go]$$W
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . . . . . . . . . . . . |
$$ | . . . X . O . . . X . . . . . . . . . |
$$ | . . . X . . . . X . . . . . . . . . . |
$$ | . . . X . O O O X . . . . . . . . . . |
$$ | . . . X X X O X X , . . . . . , . . . |
$$ | . . . X . O X . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

If black tries to play the move now, white probably won't answer the same way. Here's one possibility:

Click Here To Show Diagram Code

[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . . . . . . . . . . . . |
$$ | . . . X . O . . . X . . . . . . . . . |
$$ | . . . X . . 1 2 X . . . . . . . . . . |
$$ | . . . X . O O O X . . . . . . . . . . |
$$ | . . . X X X O X X , . . . . . , . . . |
$$ | . . . X . O X . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

So I guess to me, I would wonder, again, if the marked exchange benefits black in the slightest:

Click Here To Show Diagram Code

[go]$$W
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . O . . . . . . . . . . . . |
$$ | . . . O O . . . . . . . . . . . . . . |
$$ | . . . X . O . . . X . . . . . . . . . |
$$ | . . . X . W B . X . . . . . . . . . . |
$$ | . . . X . O O O X . . . . . . . . . . |
$$ | . . . X X X O X X , . . . . . , . . . |
$$ | . . . X . O X . . X . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Both variations appear to cut, but if this exchange is even a fraction of a point better for black, that could be the reason it is better.

_________________
be immersed

Well, I didn't realize what it was until now when I checked back in the thread. What happened was that you had already edited your post when I clicked "quote" to include strikeout tags and "I'm stupid". Now, I'm not forum savvy so I didn't know those were strikeout tags so to me it looked like they were tags to make only the original message show, and the "I'm stupid" appeared to be hidden to only show up in a quote. I bet a more experienced forum user would have identified what had happened right away, but to me it all just seemed bizarre Anyway, no hidden tags, just normal tags added on in an edit that did not show on my screen since I had not refreshed. My bad!

Oops. No problem!

I don't think that exchange is good for black. I think the key takeaway for this problem is just that double peep.

Does it say anywhere in the book that any move other than the first one of the given main-line solution is necessarily a failure?

And while the given solution may not be better than yours, it clearly is more educational, since it makes the double peep explicit.

Generally in cases like this the book will state that it's also ok to play the wedge first.

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?

_________________
be immersed

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 viewtopic.php?p=101952#p101952 The video is at http://eurogotv.com/index.php?menu=Vide ... AeECADmHmc Apologies to cherryhill for derailment XD

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...

_________________
be immersed

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.

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]

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]

_________________
Dave Sigaty
"Short-lived are both the praiser and the praised, and rememberer and the remembered..."
- Marcus Aurelius; Meditations, VIII 21

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.