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today's problem of tsumegopro
http://www.lifein19x19.com/viewtopic.php?f=15&t=10350
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Author:  cyclops [ Sat May 24, 2014 3:02 pm ]
Post subject:  today's problem of tsumegopro

Tsumego pro is a very nice app for android tablets and provides daily exercises. Today it bluntly declared my solution to the first hard problem as wrong. I am not sure tsumegopro is correct.
Thx for your advice.
Click Here To Show Diagram Code
[go]$$Bc
$$ +-------------------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . O . . . . . .
$$ | . . . O . O . . .
$$ | . O O X O . . . .
$$ | O X X X O O . . .
$$ | . O O X X X O . .
$$ | . . . . . X O . .
$$ | . . X X X X O . .
$$ | . . X O X O O . .
$$ | . X O O O . . . .
$$ | . O . . . . . . .
$$ | . . O . . . . . .
$$ | . . . . . . . . .[/go]


black to play ...

Attachments:
TsumegoPro240514hard1_prob.sgf [326 Bytes]
Downloaded 339 times

Author:  cyclops [ Sat May 24, 2014 3:07 pm ]
Post subject:  Re: today's problem of tsumegopro

Here my solution and tsumego's solution

I played :b7: at A12 but tsumego wants it at B10. I guess both are correct but mine is even a bit better as I play the more sente-ish move first.


Attachments:
TsumegoPro240514hard1_prob.sgf [326 Bytes]
Downloaded 570 times

Author:  Inkwolf [ Sat May 24, 2014 6:46 pm ]
Post subject:  Re: today's problem of tsumegopro

EDIT: D'oh. deleting my answer, didn't notice the atari on the upper side....why I'm still on the beginner problems...

Author:  cyclops [ Mon May 26, 2014 6:12 pm ]
Post subject:  Re: today's problem of tsumegopro

Bonobo showed me how to become famous by answering your own questions. So here I go.

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


:b7: at a or at be that is the question.

1. :b5: and :b7: both proof that the combination :b1: :b3: solves the problem.
2. Both a and b proof that equally well. In that sense there is no best :b7:
3. the app shouldn't disapprove of my solution ( :b7: at a ).
3. w won't answer :b1: until the endgame or as threats in a ko fight.
4. If in a ko fight W eventually threatens at :w6: B will answer at a because the penalty of not answering it is more severe than after b.
5. The proverb sente first gote later is a good guide in situations like this.
6. Only if you can attack W's south wing playing :b7: at b might be better.

Author:  Bill Spight [ Mon May 26, 2014 6:51 pm ]
Post subject:  Re: today's problem of tsumegopro

cyclops wrote:
Bonobo showed me how to become famous by answering your own questions. So here I go.

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


:b7: at a or at be that is the question.


"a" and "c" are miai, forming a two-way ko threat. Since White's threat is much larger than Black's, it can hardly be wrong for Black to play at "a" to eliminate White's threat.:)

Besides, :w4: and :w6: are for illustrative purposes. In a real game White would play :w6: first. ;)

Author:  cyclops [ Tue May 27, 2014 8:23 am ]
Post subject:  Re: today's problem of tsumegopro

Bill Spight wrote:
Besides, :w4: and :w6: are for illustrative purposes. In a real game White would play :w6: first. ;)

So next diagram shows the normal evolution.
Click Here To Show Diagram Code
[go]$$Bc :b11:@d
$$ +-----------------
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . O . . . . .
$$ | . . . O . O . .
$$ | 8 O O X O . . .
$$ | O X X X O O . .
$$ | 2 O O X X X O .
$$ | 9 1 6 7 . X O .
$$ | 3 . X X X X O .
$$ | d 5 X O X O O .
$$ | 4 X O O O . . .
$$ | 0 O . . . . . .
$$ | . . O . . . . .
$$ | . . . . . . . .[/go]


In hindsight my question was not of that much interest. :sad:

Author:  Bill Spight [ Tue May 27, 2014 8:50 am ]
Post subject:  Re: today's problem of tsumegopro

cyclops wrote:
Bill Spight wrote:
Besides, :w4: and :w6: are for illustrative purposes. In a real game White would play :w6: first. ;)

So next diagram shows the normal evolution.
Click Here To Show Diagram Code
[go]$$Bc :b11:@d
$$ +-----------------
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . O . . . . .
$$ | . . . O . O . .
$$ | 8 O O X O . . .
$$ | O X X X O O . .
$$ | 2 O O X X X O .
$$ | 9 1 6 7 . X O .
$$ | 3 . X X X X O .
$$ | d 5 X O X O O .
$$ | 4 X O O O . . .
$$ | 0 O . . . . . .
$$ | . . O . . . . .
$$ | . . . . . . . .[/go]


In hindsight my question was not of that much interest. :sad:


Well, in a real game, White would probably play elsewhere after :b1:, saving :w2:, :w4:, and :w6: as potential ko threats. But in a problem it is important to have White play them. :w2: is important, because Black could misplay :b3:. :w4: and :w6: are important to show that White cannot take away the eye on the second line because of damezumari.

But it is silly to criticize your :b7: in the problem line, and, to judge from complaints here, that kind of thing is not uncommon with interactive problem software. I think that that is an important issue to raise.

Author:  cyclops [ Tue May 27, 2014 9:28 am ]
Post subject:  Re: today's problem of tsumegopro

Thx, Bill, for your clarifications.
For completeness I added my refutation for another :w2: .
Click Here To Show Diagram Code
[go]$$Bc :w8: @a-> :b9: @e
$$ +-----------------
$$ | . . . . . . . .
$$ | . . . . . . . .
$$ | . . O . . . . .
$$ | . . . O . O . .
$$ | . O O X O . . .
$$ | O X X X O O . .
$$ | 7 O O X X X O .
$$ | a 1 e . . X O .
$$ | 3 5 X X X X O .
$$ | 4 2 X O X O O .
$$ | 6 . O O O . . .
$$ | . O . . . . . .
$$ | . . O . . . . .
$$ | . . . . . . . .[/go]

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