Hi!
I have a question about a particular tsumego exercise at GoChild
Problem 2763 (Dong-Dong grouping):
https://i.imgur.com/G3SpYF0.png
http://eidogo.com/#4tsEbyN8q
It gives two correct answers for black. Playing either T19 or T18.
The way I understand the problem, playing T19 kills the corner ("bent four in the corner").
https://senseis.xmp.net/?BentFourInTheCorner
Playing T18 starts a ko and if white wins the ko, white can live.
So basically I would expect T18 to be wrong, because if you can just kill the corner,
why would you want to give white the opportunity to live by winning the ko?
Or does it somehow depend on the rule-set that is being played under, which might determine
whether or not "bent four in the corner" has to be played out?
greetings and thanks in advance for any feedback on this issue.
GoChild tsumego question
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S0nge
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Re: GoChild tsumego question
It's weird for sure. Maybe the idea behind T18 being accepted as a valid answer is that Black will not play either of both moves until the very end of the game. He can then be assured that white does not have anay ko threat left. If he, Black, still has some, then T18 does the job.
That being said I agree that T19 is simpler and safer, whichever ruleset is in use.
That being said I agree that T19 is simpler and safer, whichever ruleset is in use.
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xela
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Re: GoChild tsumego question
For reference, the position is:
(See How to make diagrams. If you copy-paste from examples on that page, it's pretty quick and easy.)
The choice comes down to whether black is forced to remove the white stones during the game, or whether the black stones on the outside are independently alive.
This is a bit far-fetched, but the best I could come up with: suppose there is a ko fight elsewhere on the board, white plays
as a ko threat and black ignores it:
Now black a is too slow. If black wants to save the marked stones and capture the corner, then b is the only way.
Alternatively, later in the endgame it might look like this:
(See How to make diagrams. If you copy-paste from examples on that page, it's pretty quick and easy.)
The choice comes down to whether black is forced to remove the white stones during the game, or whether the black stones on the outside are independently alive.
This is a bit far-fetched, but the best I could come up with: suppose there is a ko fight elsewhere on the board, white plays
as a ko threat and black ignores it:Now black a is too slow. If black wants to save the marked stones and capture the corner, then b is the only way.
Alternatively, later in the endgame it might look like this:
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dohduhdah
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Re: GoChild tsumego question
Yeah, I guess one can kind of imagine a context that justifies each of the given
answers. But often the logic of the tsumego seems to be that you have to consider only
the pattern given and then certain responses are not accepted because they are
not optimal (like leaving more ko-threats while otherwise obtaining an equivalent
result).
A closely related problem at GoChild is Problem 4631 (Dong-Dong grouping):
https://i.imgur.com/RgkRHRB.png
In this case, where white has outside liberties, only the move in the
corner at L11 is accepted as a solution. This makes sense, because
white would immediately be alive by responding at H11 if black plays at L10.
answers. But often the logic of the tsumego seems to be that you have to consider only
the pattern given and then certain responses are not accepted because they are
not optimal (like leaving more ko-threats while otherwise obtaining an equivalent
result).
A closely related problem at GoChild is Problem 4631 (Dong-Dong grouping):
https://i.imgur.com/RgkRHRB.png
In this case, where white has outside liberties, only the move in the
corner at L11 is accepted as a solution. This makes sense, because
white would immediately be alive by responding at H11 if black plays at L10.
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xela
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Re: GoChild tsumego question
If you put letters on the diagrams here, it's much easier to read...
Black a is the only correct answer here. If black b, then white c. If you've got two or more outside liberties, then you can squeeze.
Black a is the only correct answer here. If black b, then white c. If you've got two or more outside liberties, then you can squeeze.
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dohduhdah
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Re: GoChild tsumego question
Yeah, but the downside is that it kind of gives away the answer in the diagram, so if possiblexela wrote:If you put letters on the diagrams here, it's much easier to read...
[..]
I'd prefer to have custom coordinates on the diagram.
I didn't see how to do that, so I just referred to the coordinates visible in the imgur
screenshot.
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xela
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Re: GoChild tsumego question
Where your diagram code has "$$B Black to play" at the top, just put in a 'c' for coordinates: "$$Bc Black to play", like this:
It's all there in the instructions at How to make diagrams.
To get coordinates matching your screen shot, you need to tell it you're on an 11x11 board. So that's "$$Bc11":
You can also put and around a block of text if you want to hide an answer,
Diagrams are the best feature of the site (next to embedded SGFs). We've got features that make it easier to discuss go positions, no need to open screen shots in another window to see what's going on. That's why I'm here, not on reddit or facebook.
It's all there in the instructions at How to make diagrams.
To get coordinates matching your screen shot, you need to tell it you're on an 11x11 board. So that's "$$Bc11":
You can also put
Code: Select all
[hide]Code: Select all
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