Interesting go problem from a real game

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gamesorry
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Interesting go problem from a real game

Post by gamesorry »

I recently came across an interesting game in one of the online tournaments:
Click Here To Show Diagram Code
[go]$$B
$$ ----------------------
$$ X . X X O . . . . . . |
$$ . X . X O . X X W . . |
$$ X X X O O . . O X . . |
$$ . . . . O . . O X . . |
$$ X X . O X X . O X O . |
$$ . X O . . . O O O X . |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
The question is, after white's move, can black defend the corner without a ko?
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dhu163
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Re: Interesting go problem from a real game

Post by dhu163 »

Click Here To Show Diagram Code
[go]$$W
$$ ----------------------
$$ X . X X O . . . X . . |
$$ . X . X O . X X X X 3 |
$$ X X X O O . . O X O . |
$$ . . . . O . . O X O 1 |
$$ X X . O X X . O X O 4 |
$$ . X O . . . O O O X 2 |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
I think so
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Shaddy
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Re: Interesting go problem from a real game

Post by Shaddy »

dhu163 wrote:
Click Here To Show Diagram Code
[go]$$W
$$ ----------------------
$$ X . X X O . . . X . . |
$$ . X . X O . X X X X 3 |
$$ X X X O O . . O X O . |
$$ . . . . O . . O X O 1 |
$$ X X . O X X . O X O 4 |
$$ . X O . . . O O O X 2 |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
Click Here To Show Diagram Code
[go]$$W
$$ ----------------------
$$ X . X X O . . . . . . |
$$ . X . X O . X X 1 2 . |
$$ X X X O O . . O X . . |
$$ . . . . O . . O X . 3 |
$$ X X . O X X . O X O . |
$$ . X O . . . O O O X . |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
Ko. I don't see any way for Black to keep the whole corner, at least the 2 stones on top are going to get ko'd.
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Tryss
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Re: Interesting go problem from a real game

Post by Tryss »

Edit : same idea as Shaddy

White won't play like that in this line :
Click Here To Show Diagram Code
[go]$$B
$$ ----------------------
$$ X . X X O . . . 3 . . |
$$ . X . X O . X X W 1 . |
$$ X X X O O . . O X 2 . |
$$ . . . . O . . O X . 4 |
$$ X X . O X X . O X O . |
$$ . X O . . . O O O X . |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
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skydyr
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Re: Interesting go problem from a real game

Post by skydyr »

The empty triangle looks good to me at first, but...
Click Here To Show Diagram Code
[go]$$B
$$ ----------------------
$$ X . X X O . . . . . . |
$$ . X . X O . X X W 2 3 |
$$ X X X O O . . O X 1 6 |
$$ . . . . O . . O X . 4 |
$$ X X . O X X . O X O . |
$$ . X O . . . O O O X 5 |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
However, does black need to play :b3?
Click Here To Show Diagram Code
[go]$$B
$$ ----------------------
$$ X . X X O . 8 6 9 7 0 |
$$ . X . X O . X X W 2 4 |
$$ X X X O O . . O X 1 . |
$$ . . . . O . . O X . 3 |
$$ X X . O X X . O X O 5 |
$$ . X O . . . O O O X . |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
This seems to work:
Click Here To Show Diagram Code
[go]$$B
$$ ----------------------
$$ X . X X O . O O 1 . O |
$$ . X . X O . X X O O O |
$$ X X X O O . . O X X . |
$$ . . . . O . . O X . X |
$$ X X . O X X . O X O X |
$$ . X O . . . O O O X . |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
However:
Click Here To Show Diagram Code
[go]$$B
$$ ----------------------
$$ X . X X O . . 7 . 6 . |
$$ . X . X O . X X W 2 4 |
$$ X X X O O . 8 O X 1 . |
$$ . . . . O . . O X . 3 |
$$ X X . O X X . O X O 5 |
$$ . X O . . . O O O X . |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
So perhaps:
Click Here To Show Diagram Code
[go]$$B
$$ ----------------------
$$ X . X X O . . 9 . 6 . |
$$ . X . X O . X X W 2 4 |
$$ X X X O O . 7 O X 1 . |
$$ . . . . O . 8 O X . 3 |
$$ X X . O X X . O X O 5 |
$$ . X O . . . O O O X . |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
And now black has enough liberties for the fight.
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Shaddy
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Re: Interesting go problem from a real game

Post by Shaddy »

skydyr - still not enough liberties.
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skydyr
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Re: Interesting go problem from a real game

Post by skydyr »

Shaddy wrote:skydyr - still not enough liberties.
In the last diagram? I don't see it, so could you explain?

That said, I think on re-examination, white can play at :b9: instead and black can either play an unfavourable ko or connect and let white connect under.

Edit: Nevermind, I'm still counting four for some reason.
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phillip1882
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Re: Interesting go problem from a real game

Post by phillip1882 »

Click Here To Show Diagram Code
[go]$$W
$$ ----------------------
$$ X . X X O . . . 6 . . |
$$ . X . X O . X X 1 2 . |
$$ X X X O O . . O X 5 . |
$$ . . . . O . . O X . 3 |
$$ X X . O X X . O X O . |
$$ . X O . . . O O O X 4 |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
Click Here To Show Diagram Code
[go]$$W
$$ ----------------------
$$ X . X X O . . . X . . |
$$ . X . X O . X X 2 X 1 |
$$ X X X O O . . O X O . |
$$ . . . . O . . O X . O |
$$ X X . O X X . O X O . |
$$ . X O . . . O O O X X |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O . O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
now what for white?
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Schachus
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Re: Interesting go problem from a real game

Post by Schachus »

Phillip:
Click Here To Show Diagram Code
[go]$$W
$$ ----------------------
$$ X . X X O . . . X . . |
$$ . X . X O . X X . X . |
$$ X X X O O . . O X O . |
$$ . . . . O . . O X a O |
$$ X X . O X X . O X O b |
$$ . X O . . . O O O X X |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O 1 O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
Black is captured, because he cant approach a, so white b next captures.
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gamesorry
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Re: Interesting go problem from a real game

Post by gamesorry »

Thanks, so it does seem that a ko is unavoidable.

FYI, the original game is here. I missed white's refusal at (4,1) at first glance.
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rafaelclp
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Re: Interesting go problem from a real game

Post by rafaelclp »

Schachus wrote:Phillip:
Click Here To Show Diagram Code
[go]$$W
$$ ----------------------
$$ X . X X O . . . X . . |
$$ . X . X O . X X . X . |
$$ X X X O O . . O X O . |
$$ . . . . O . . O X a O |
$$ X X . O X X . O X O b |
$$ . X O . . . O O O X X |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O 1 O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
Black is captured, because he cant approach a, so white b next captures.
I still don't get why black dies. Wouldn't 5 below save black if white played as expected above?
Click Here To Show Diagram Code
[go]$$B
$$ ----------------------
$$ X . X X O . . . 3 . . |
$$ . X . X O . X X . 1 5 |
$$ X X X O O . . O X 2 . |
$$ . . . . O . . O X . 4 |
$$ X X . O X X . O X O . |
$$ . X O . . . O O O X . |
$$ O O O X X X O X X . X |
$$ . O X X . O . O X X X |
$$ . . . . X O . O 6 O X |
$$ . . . . X O O . O . O |
$$ . . . . X X X O . O . |
$$[/go]
Edit: oh, right, it still ends in ko
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