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 Post subject: What is the solution to this tesuji problem?
Post #1 Posted: Wed Mar 04, 2020 6:35 pm 
Dies in gote

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The book Graded Go Problems for Dan Players Volume Five contains the following tesuji problem/capturing race. Black to play, any ladder towards the right works for Black, any ladder towards the left works for white.

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


The white N16 group and the black S16 group are fighting for life and death.
The first correct move is N15, no questions here.

Click Here To Show Diagram Code
[go]$$Bc
$$ +---------------------------+
$$ . . . . . . . . . . X O . |
$$ . . . . . X X . O O . O X |
$$ . . . X X O . X X O O X . |
$$ . . . X O . O O O X X X . |
$$ . . X O . . B X X O . O . |
$$ . . . . . . . . . O . O . |
$$ . . . . . . , . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . , . . . . . , . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |[/go]


The sequence given as the solution is the following, white is caught in a ladder. Fair enough.

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


But what happens when white :w2: is placed at M16? What can Black do now?

Click Here To Show Diagram Code
[go]$$Bc
$$ +---------------------------+
$$ . . . . . . . . . . X O . |
$$ . . . . . X X . O O . O X |
$$ . . . X X O . X X O O X . |
$$ . . . X O 2 O O O X X X . |
$$ . . X O . . 1 X X O . O . |
$$ . . . . . . . . . O . O . |
$$ . . . . . . , . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . , . . . . . , . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |[/go]


The first intuition for Black is the cut at L15.

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


However, as the ladder towards the left favors white, black cant capture white this way. In fact, the book describes this exact sequence as a wrong answer for Black, but it doesn't show a correct move for Black in this situation.
My question is then, what is the correct Black response to :w2: at M16? I can't find any move that would work. In fact, the only other candidates are N17 and M15 and these seem to fail immediately. Am I missing something or is the book mistaken?

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 Post subject: Re: What is the solution to this tesuji problem?
Post #2 Posted: Wed Mar 04, 2020 7:45 pm 
Lives with ko

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Actually, there’s two different moves that work for black after white 2.
My question is: which one is better? I’m not quite sure which leaves less aji. :scratch:

Hint:
Surround first, then kill.

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 Post subject: Re: What is the solution to this tesuji problem?
Post #3 Posted: Wed Mar 04, 2020 8:23 pm 
Honinbo

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Not sure if it's best, but doesn't seem all that bad...
Click Here To Show Diagram Code
[go]$$Bc
$$ +---------------------------+
$$ . . . . . . . . . . X O . |
$$ . . . . . X X . O O . O X |
$$ . . . X X O . X X O O X . |
$$ . . . X O 2 O O O X X X 6 |
$$ . . X C 5 7 1 X X O 4 O . |
$$ . . . 3 . . . . . O . O . |
$$ . . . . . . , . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . , . . . . . , . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |[/go]

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 Post subject: Re: What is the solution to this tesuji problem?
Post #4 Posted: Wed Mar 04, 2020 11:19 pm 
Judan

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Leon, I agree connect is better for White and means Black's inside stones die so White's live if no ladder to bottom left. Telegraph Go. I think you miscounted liberties: if black K14 (better) or l14 then white just r15 and wins the race. Sure black gets a squeeze and the result still could be ok, but it's much worse than saving black and killing White inside.

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 Post subject: Re: What is the solution to this tesuji problem?
Post #5 Posted: Thu Mar 05, 2020 2:07 am 
Lives in gote

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Uberdude wrote:
...if black K14 (better) or l14 then white just r15 and wins the race

Why is K14 better than L14? This is a nice one for tewari analysis!
Click Here To Show Diagram Code
[go]$$Bc
$$ +---------------------------+
$$ . . . . . . . . . . X O . |
$$ . . . . . X X . O O . O X |
$$ . . . X X O . X X O O X . |
$$ . . . X O O O O O X X X 4 |
$$ . . X O 3 . X X X O 2 O . |
$$ . . . a 1 . . . . O . O . |
$$ . . . . . . , . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . , . . . . . , . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |
$$ . . . . . . . . . . . . . |[/go]

If the move order were :w2: -- :b3: -- :w4:, then surely black would like to follow up at a rather than :b1:.

Getting back to the original position, I wonder if there's been a mistranslation and all ladders are supposed to work? Otherwise it seems rather unsatisfying as a problem.

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 Post subject: Re: What is the solution to this tesuji problem?
Post #6 Posted: Thu Mar 05, 2020 3:19 am 
Dies in gote

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[quote]The first correct move is N15, no questions here.[quote]

What about b's first move at M15?

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 Post subject: Re: What is the solution to this tesuji problem?
Post #7 Posted: Thu Mar 05, 2020 3:53 am 
Judan

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dust wrote:
Quote:
The first correct move is N15, no questions here.


What about b's first move at M15?


Then N15. Black can capture l16 but not White's important p16 stones.

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 Post subject: Re: What is the solution to this tesuji problem?
Post #8 Posted: Thu Mar 05, 2020 6:55 am 
Dies in gote

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Ok, the sequence that Kirby posted is the best black can do here then.
The book worded this problem somewhat poorly then, but its not to unreasonable.

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 Post subject: Re: What is the solution to this tesuji problem?
Post #9 Posted: Thu Mar 05, 2020 7:21 am 
Honinbo

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Leon wrote:
Ok, the sequence that Kirby posted is the best black can do here then.
The book worded this problem somewhat poorly then, but its not to unreasonable.


I wonder if there was an issue with translation - it's probably a problem from another source (e.g. a Japanese book). In that case, maybe the original problem said something like "all ladders work for black"... But it'd be a little weird that they'd mess up this translation, and *also* post the ladder you showed as a failure diagram.

I think I might have this book, but I haven't looked at it in awhile. If the ladder were to work for black on both sides, and the book's "wrong answer" is actually the solution, would the level of difficulty match the problems around it? I seem to recall that Graded Go Problems for Dan Players have problems that gradually increase in difficulty. In that case, does the difficulty of reading the ladder variation match the level of difficulty of the problems before and after it?

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 Post subject: Re: What is the solution to this tesuji problem?
Post #10 Posted: Thu Mar 05, 2020 7:38 am 
Judan

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I just checked the book as I have it too. It's a wrong problem and the explanation in the answer is illogical. In summary it says:
- After black push 1 if white connect 2 then 3 cut for ladder looks like a tesuji but doesn't work cos we said that ladder doesn't work
- So this black 3 is correct and then ladder other way, but white 2 changed from solid connect that wins the race to worse outside connect.
- It doesn't give a working black 3 if white plays good move 2.
Bad problem.


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 Post subject: Re: What is the solution to this tesuji problem?
Post #11 Posted: Thu Mar 05, 2020 11:05 am 
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It was probably a good problem before the ghost writer got his hands on it. ;)

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 Post subject: Re: What is the solution to this tesuji problem?
Post #12 Posted: Thu Mar 05, 2020 3:47 pm 
Oza
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Uberdude wrote:
I just checked the book as I have it too. It's a wrong problem and the explanation in the answer is illogical. In summary it says:
- After black push 1 if white connect 2 then 3 cut for ladder looks like a tesuji but doesn't work cos we said that ladder doesn't work
- So this black 3 is correct and then ladder other way, but white 2 changed from solid connect that wins the race to worse outside connect.
- It doesn't give a working black 3 if white plays good move 2.
Bad problem.

Katago evaluates capturing the one stone and squeezing in sente as a great result for Black. So, isn't this an excellent "dan-level" problem? How quickly can you read that you cannot actually capture White and decide on squeezing? I am the type of person that would waste ten minutes of my clock time convinced that in this shape there 'must be' a tesuji here somewhere! :)

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 Post subject: Re: What is the solution to this tesuji problem?
Post #13 Posted: Thu Mar 05, 2020 5:03 pm 
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ez4u wrote:
Uberdude wrote:
I just checked the book as I have it too. It's a wrong problem and the explanation in the answer is illogical. In summary it says:
- After black push 1 if white connect 2 then 3 cut for ladder looks like a tesuji but doesn't work cos we said that ladder doesn't work
- So this black 3 is correct and then ladder other way, but white 2 changed from solid connect that wins the race to worse outside connect.
- It doesn't give a working black 3 if white plays good move 2.
Bad problem.

Katago evaluates capturing the one stone and squeezing in sente as a great result for Black. So, isn't this an excellent "dan-level" problem? How quickly can you read that you cannot actually capture White and decide on squeezing? I am the type of person that would waste ten minutes of my clock time convinced that in this shape there 'must be' a tesuji here somewhere! :)


I agree with the sentiment, but if that's the case, it'd be good to be a bit more clear in the solution that this was the intent.

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 Post subject: Re: What is the solution to this tesuji problem?
Post #14 Posted: Mon Aug 17, 2020 2:36 am 
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I have the japanese problem book this was taken from (六段合格の手筋150題) and despite my japanese being a bit rusty at the moment it doesn't say anything in the problem description about the ladders being bad for black. The solution you showed is listed as being correct.

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