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 Post subject: Re: Tsumegos from real games
Post #61 Posted: Wed Sep 22, 2021 2:55 am 
Lives in sente
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I wanted to play :w5: at :w9:, and if black draws out the stones, you can build the eye.

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 Post subject: Re: Tsumegos from real games
Post #62 Posted: Tue Oct 12, 2021 11:11 pm 
Gosei
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Problem #26, an endgame problem.

I was White in that game. Both players missed a big endgame move, which one? Black to play.

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

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 Post subject: Re: Tsumegos from real games
Post #63 Posted: Wed Oct 13, 2021 2:35 am 
Lives in sente
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Click Here To Show Diagram Code
[go]$$Bc Black to play
$$ ---------------------------------------
$$ | . . . . O O O X . . X X X O . . 3 . . |
$$ | . . . O O X X . . X X O X O 1 . . . . |
$$ | . . . O X X . X . X O O O . . 2 O O O |
$$ | . . . O O O X X . , X X O O O O X X O |
$$ | O O O . . . O O X . . . X X X X . X O |
$$ | O X X . . O . . X . X O X . . . . X X |
$$ | O X . . . O X . . X . . O X . . . . . |
$$ | X . X . . X X O O X . . O O X . . . . |
$$ | . . X . . . X X O X O . O X . . X . . |
$$ | . . . X X O O X O X O . O X . , . . . |
$$ | . . . X X X X O O X O X O X . O O X . |
$$ | . . X O X X O . . O O O X . . X . . X |
$$ | . X X O O O O . . . O X . X . X X X O |
$$ | . X O . . . . . O . O X . . . O . O O |
$$ | O X O . . . . O X O . . . . . . O . . |
$$ | . O . , . . . O X X O O O O O , . . . |
$$ | . . . O . . . O O X X X b X X X O O . |
$$ | . . . . . . . . O X . . . . . . X X O |
$$ | . . . . . . . . . . a . . . . . . X . |
$$ ---------------------------------------[/go]


I think this is a problem for White. If S19, then Black throws in and squeezes on the left before S18, which leaves White short of liberties for the squeeze. If Q18 first, then Black just lets himself get squeezed, but then O17 becomes a double atari.

On the lower side, I think White could also go in at 'a', so Black should protect at 'b'.

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 Post subject: Re: Tsumegos from real games
Post #64 Posted: Wed Oct 13, 2021 4:41 am 
Gosei
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@Harleqin: you got the correct :b1: but I think your :b3: doesn't work.

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


Click Here To Show Diagram Code
[go]$$Wcm8
$$ ---------------------------------------
$$ | . . . . O O O X . . X X X O X . X O 4 |
$$ | . . . O O X X . . X X O X O X 5 3 2 . |
$$ | . . . O X X . X . X O O O 1 O O O O O |
$$ | . . . O O O X X . , X X O O O O X X O |
$$ | O O O . . . O O X . . . X X X X . X O |
$$ | O X X . . O . . X . X O X . . . . X X |[/go]

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 Post subject: Re: Tsumegos from real games
Post #65 Posted: Wed Oct 13, 2021 7:36 am 
Gosei
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Rank: KGS 2d OGS 1d Fox 4d
KGS: Artevelde
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Click Here To Show Diagram Code
[go]$$Bc Black to play
$$ ---------------------------------------
$$ | . . . . O O O X . . X X X O 3 . . 6 . |
$$ | . . . O O X X . . X X O X O 1 2 . . . |
$$ | . . . O X X . X . X O O O 5 . 4 O O O |
$$ | . . . O O O X X . , X X O O O O X X O |
$$ | O O O . . . O O X . . . X X X X . X O |
$$ | O X X . . O . . X . X O X . . . . X X |
$$ | O X . . . O X . . X . . O X . . . . . |
$$ ---------------------------------------[/go]


Initially I saw the above sequence.

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


Then I realized White could change the order and think about saving everything. I don't think she can.

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


So it probably boils down to the initial sequence in reverse order anyway.

Click Here To Show Diagram Code
[go]$$Bc Black to play
$$ ---------------------------------------
$$ | . . . . O O O X . . X X X O . . 3 6 9 |
$$ | . . . O O X X . . X X O X O 1 5 8 7 0 |
$$ | . . . O X X . X . X O O O 4 . 2 O O O |
$$ | . . . O O O X X . , X X O O O O X X O |
$$ | O O O . . . O O X . . . X X X X . X O |
$$ | O X X . . O . . X . X O X . . . . X X |
$$ | O X . . . O X . . X . . O X . . . . . |
$$ ---------------------------------------[/go]


And I don't think Harleqin's move holds, but for different reasons.


Click Here To Show Diagram Code
[go]$$Bc Black to play
$$ ---------------------------------------
$$ | . . . . O O O X . . X X X O 3 . 5 6 9 |
$$ | . . . O O X X . . X X O X O 1 . 8 7 0 |
$$ | . . . O X X . X . X O O O 4 . 2 O O O |
$$ | . . . O O O X X . , X X O O O O X X O |
$$ | O O O . . . O O X . . . X X X X . X O |
$$ | O X X . . O . . X . X O X . . . . X X |
$$ | O X . . . O X . . X . . O X . . . . . |
$$ ---------------------------------------[/go]


Edit: I'm defeated by my own argument ....

So how about:

Click Here To Show Diagram Code
[go]$$Bc Black to play
$$ ---------------------------------------
$$ | . . . . O O O X . . X X X O 3 . . 5 . |
$$ | . . . O O X X . . X X O X O 1 . . . . |
$$ | . . . O X X . X . X O O O 4 . 2 O O O |
$$ | . . . O O O X X . , X X O O O O X X O |
$$ | O O O . . . O O X . . . X X X X . X O |
$$ | O X X . . O . . X . X O X . . . . X X |
$$ | O X . . . O X . . X . . O X . . . . . |
$$ ---------------------------------------[/go]


Seems like seki

But is it sente? That makes all the difference


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 Post subject: Re: Tsumegos from real games
Post #66 Posted: Wed Oct 13, 2021 8:05 am 
Gosei
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You got it!

The last diagram is best for White since White gets sente, while White takes gote in the first diagram.

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 Post subject: Re: Tsumegos from real games
Post #67 Posted: Sun Nov 21, 2021 2:58 pm 
Gosei
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Problem #27, White to live.

This is from a 2-stone handicap game. In the game I managed to live after a 50-move fight but there was a much simpler solution.

Edit: after all, it seems that Black can kill, see kvasir's message below. So the problem doesn't work (or should be reformulated as "White to live or to find a good way to sacrifice").

Click Here To Show Diagram Code
[go]$$Wc White to live
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . X . . . . . |
$$ | . . . . . . . . . X . O O O X . . . . |
$$ | . X X X . X . . X . . O . O X . . . . |
$$ | . X O O O . . . . , . O O X . X . . . |
$$ | . O . . . . O . X . . O X X . . X . . |
$$ | . O X . . . . . . . X X O X . O O . . |
$$ | . . O . . . . . . . . . O O . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . X . . . |
$$ | . O O X . . . . . , . . . . . , X . . |
$$ | . O X . . X . . . . . O . . O . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Answer:

Click Here To Show Diagram Code
[go]$$Wc Answer
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . X . . . . . |
$$ | . . . . . . . . . X 4 O O O X . . . . |
$$ | . X X X . X . . X 3 a O . O X . . . . |
$$ | . X O O O . . . 2 1 . O O X . X . . . |
$$ | . O . . . . O . X 6 7 O X X . . X . . |
$$ | . O X . . . . . . 5 X X O X . O O . . |
$$ | . . O . . . . . . . b . O O . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . X . . . |
$$ | . O O X . . . . . , . . . . . , X . . |
$$ | . O X . . X . . . . . O . . O . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Last edited by jlt on Thu Nov 25, 2021 11:29 am, edited 1 time in total.
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 Post subject: Re: Tsumegos from real games
Post #68 Posted: Tue Nov 23, 2021 3:21 pm 
Gosei
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Problem #28, White to play. Not exactly a life and death problem, but a problem related to the life and death status of a corner group. One of the forum members will recognize this position if he reads this.

Click Here To Show Diagram Code
[go]$$Wc White to play
$$ ---------------------------------------
$$ | . . . b c . . . O X X X . . . . . X . |
$$ | . . X X O . . . a O O X X . X . . . X |
$$ | . . X O . O . . . . O . . O X . X X O |
$$ | . X X O . . . . . , O X . O . X O O O |
$$ | . X O . O . . . . . O X . . O O O X . |
$$ | . O O O . O . . . . . X . X X . O . . |
$$ | . . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . . . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |
$$ | . . . X O . X X . X . O . . . O . . . |
$$ | . . X O O O O X O O . O X . . . . X . |
$$ | X X X X O . X O O . O X X . . O O X . |
$$ | X O O O X X X . . , . . . X . , X . . |
$$ | O O . . O X . . O . . O . . X . . . . |
$$ | . . O . O X . . . . . . O O X . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


In the game I didn't want to connect passively at "a", and I hesitated between "b" and "c".

1) If White plays "b", how does Black protect the corner group?
2) If White plays "b", can Black respond with F19?
3) If White plays "c", is it sente? Suppose that Black plays elsewhere, does White have a followup?

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 Post subject: Re: Tsumegos from real games
Post #69 Posted: Thu Nov 25, 2021 10:54 am 
Lives with ko

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IGS: kvasir
jlt wrote:
Problem #27, White to live.
...
Answer:


I was thinking along same lines but I have doubts.
Click Here To Show Diagram Code
[go]$$Wc White to live?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . X . . . . . |
$$ | . . . . . . . . . X . O O O X . . . . |
$$ | . X X X . X . . X 3 . O . O X . . . . |
$$ | . X O O O . . . . 1 4 O O X . X . . . |
$$ | . O . . . . O . X . 2 O X X . . X . . |
$$ | . O X . . . . . . . X X O X . O O . . |
$$ | . . O . . . . . . . . . O O . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . X . . . |
$$ | . O O X . . . . . , . . . . . , X . . |
$$ | . O X . . X . . . . . O . . O . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


When I put down the diagram it occurred to me that white could play :w5: and that looked like a very good move but it is not saving the dead stones.

Click Here To Show Diagram Code
[go]$$Wcm5 White not living.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . X . . . . . |
$$ | . . . . . . . 2 1 X 6 O O O X . . . . |
$$ | . X X X . X . 5 X O 4 O . O X . . . . |
$$ | . X O O O . . . 3 O X O O X . X . . . |
$$ | . O . . . . O . X . X O X X . . X . . |
$$ | . O X . . . . . . . X X O X . O O . . |
$$ | . . O . . . . . . . . . O O . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . X . . . |
$$ | . O O X . . . . . , . . . . . , X . . |
$$ | . O X . . X . . . . . O . . O . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


Click Here To Show Diagram Code
[go]$$Wcm5 White not living, continued.
$$ ---------------------------------------
$$ | . . . . . . . 7 . . . . . X . . . . . |
$$ | . . . 6 1 3 4 X O X X O O O X . . . . |
$$ | . X X X 2 X 5 O . O X O . O X . . . . |
$$ | . X O O O . . . O O X O O X . X . . . |
$$ | . O . . . . O . X . X O X X . . X . . |
$$ | . O X . . . . . . . X X O X . O O . . |
$$ | . . O . . . . . . . . . O O . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . 8 . . . . . . . . . . . X . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . X . . . |
$$ | . O O X . . . . . , . . . . . , X . . |
$$ | . O X . . X . . . . . O . . O . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


White is still in the game but if it is about sacrificing then keeping sente is probably better.

Click Here To Show Diagram Code
[go]$$Wcm5 White to sacrifice.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . X . . . . . |
$$ | . . . . . 6 . . 3 X 4 O O O X . . . . |
$$ | . X X X . X . 5 X O 2 O . O X . . . . |
$$ | . X O O O . . . 1 O X O O X . X . . . |
$$ | . O . . . . O . X . X O X X . . X . . |
$$ | . O X . . . . . . . X X O X . O O . . |
$$ | . . O . . . . . . . . . O O . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . 7 . . . . . . . . . . . X . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . X . . . |
$$ | . O O X . . . . . , . . . . . , X . . |
$$ | . O X . . X . . . . . O . . O . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


I wondered about not playing anything at all but black seems to have a too easy time of that.

Click Here To Show Diagram Code
[go]$$Wc White to tenuki.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . X . . . . . |
$$ | . . . . . . . . . X . O O O X . . . . |
$$ | . X X X . X . . X . . O . O X . . . . |
$$ | . X O O O . . . . . . O O X . X . . . |
$$ | . O . . . . O . X . . O X X . . X . . |
$$ | . O X . . . . . . . X X O X . O O . . |
$$ | . . O . . . . 2 . . . . O O . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . 1 . . . . . . . . . . . X . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . X . . . |
$$ | . O O X . . . . . , . . . . . , X . . |
$$ | . O X . . X . . . . . O . . O . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


I am not sure these are the best variations, but I just don't see how white is escaping.

This way also doesn't seem to allow an escape, at least I don't see the tesuji, because black is winning the capturing race even though white could potentially play something like a to e.

Click Here To Show Diagram Code
[go]$$Wc White to capture something?
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . X . . . . . |
$$ | . . . . . b . c d X . O O O X . . . . |
$$ | . X X X . X a e X O 1 O . O X . . . . |
$$ | . X O O O . . . 2 O X O O X . X . . . |
$$ | . O . . . . O . X 3 X O X X . . X . . |
$$ | . O X . . . . . 5 4 X X O X . O O . . |
$$ | . . O . . . . . 7 . . . O O . . . . . |
$$ | . . . . . . . . . 6 . . . . . . . . . |
$$ | . . . . . . . . . . 8 . . . . . . . . |
$$ | . . . , . . . . . , . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . O X . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . X . . . |
$$ | . O O X . . . . . , . . . . . , X . . |
$$ | . O X . . X . . . . . O . . O . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


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 Post subject: Re: Tsumegos from real games
Post #70 Posted: Thu Nov 25, 2021 11:31 am 
Gosei
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Hmmm... Thanks for your message. So the problem doesn't work, I overlooked :b2: in your diagram.

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 Post subject: Re: Tsumegos from real games
Post #71 Posted: Thu Nov 25, 2021 8:24 pm 
Lives with ko

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IGS: kvasir
Problem #28

I always think this corner group is confusing.

1)
I think :b2: lives without giving :w3: in sente.

Click Here To Show Diagram Code
[go]$$Wc White to play
$$ ---------------------------------------
$$ | . 2 . 1 3 . . . O X X X . . . . . X . |
$$ | . . X X O . . . . O O X X . X . . . X |
$$ | . . X O . O . . . . O . . O X . X X O |
$$ | . X X O . . . . . , O X . O . X O O O |
$$ | . X O . O . . . . . O X . . O O O X . |
$$ | . O O O . O . . . . . X . X X . O . . |
$$ | . . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . 4 . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |
$$ | . . . X O . X X . X . O . . . O . . . |
$$ | . . X O O O O X O O . O X . . . . X . |
$$ | X X X X O . X O O . O X X . . O O X . |
$$ | X O O O X X X . . , . . . X . , X . . |
$$ | O O . . O X . . O . . O . . X . . . . |
$$ | . . O . O X . . . . . . O O X . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


2)
Not sure what the question is.

Normally it would be this way but it fails because of :b2:
Click Here To Show Diagram Code
[go]$$Wc White to play
$$ ---------------------------------------
$$ | . 5 7 1 8 2 . . O X X X . . . . . X . |
$$ | 4 3 X X O . . . . O O X X . X . . . X |
$$ | . 6 X O . O . . . . O . . O X . X X O |
$$ | . X X O . . . . . , O X . O . X O O O |
$$ | . X O . O . . . . . O X . . O O O X . |
$$ | . O O O . O . . . . . X . X X . O . . |
$$ | . . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . . . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |
$$ | . . . X O . X X . X . O . . . O . . . |
$$ | . . X O O O O X O O . O X . . . . X . |
$$ | X X X X O . X O O . O X X . . O O X . |
$$ | X O O O X X X . . , . . . X . , X . . |
$$ | O O . . O X . . O . . O . . X . . . . |
$$ | . . O . O X . . . . . . O O X . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


But this is a ko. Black would normally not take this risk.

Click Here To Show Diagram Code
[go]$$Wc White to play
$$ ---------------------------------------
$$ | 7 6 . 1 . 2 . . O X X X . . . . . X . |
$$ | 4 3 X X O . . . . O O X X . X . . . X |
$$ | 5 . X O . O . . . . O . . O X . X X O |
$$ | . X X O . . . . . , O X . O . X O O O |
$$ | . X O . O . . . . . O X . . O O O X . |
$$ | . O O O . O . . . . . X . X X . O . . |
$$ | . . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . . . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |
$$ | . . . X O . X X . X . O . . . O . . . |
$$ | . . X O O O O X O O . O X . . . . X . |
$$ | X X X X O . X O O . O X X . . O O X . |
$$ | X O O O X X X . . , . . . X . , X . . |
$$ | O O . . O X . . O . . O . . X . . . . |
$$ | . . O . O X . . . . . . O O X . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


On this board I notice as I make the diagram that there is something afoot because winning the ko is not that much bigger for white than entering the side is for black.

Click Here To Show Diagram Code
[go]$$Bcm8 White to play
$$ ---------------------------------------
$$ | O X . O 4 X . 3 O X X X . . . . . X . |
$$ | O O X X O . . . 1 O O X X . X . . . X |
$$ | O . X O . O . 5 2 . O . . O X . X X O |
$$ | . X X O . . . . . , O X . O . X O O O |
$$ | . X O . O . . . . . O X . . O O O X . |
$$ | . O O O . O . . . . . X . X X . O . . |
$$ | . . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . . . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |
$$ | . . . X O . X X . X . O . . . O . . . |
$$ | . . X O O O O X O O . O X . . . . X . |
$$ | X X X X O . X O O . O X X . . O O X . |
$$ | X O O O X X X . . , . . . X . , X . . |
$$ | O O . . O X . . O . . O . . X . . . . |
$$ | . . O . O X . . . . . . O O X . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


This might be too difficult :scratch: but it is really white's choice to go after the corner because white can play like this and could then probably win the ko if black doesn't defend.

Click Here To Show Diagram Code
[go]$$Wc White to play
$$ ---------------------------------------
$$ | . . . 1 . 2 . . O X X X . . . . . X . |
$$ | . . X X O . 3 . . O O X X . X . . . X |
$$ | . . X O . O . . . . O . . O X . X X O |
$$ | . X X O . . . . . , O X . O . X O O O |
$$ | . X O . O . . . . . O X . . O O O X . |
$$ | . O O O . O . . . . . X . X X . O . . |
$$ | . . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . . . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |
$$ | . . . X O . X X . X . O . . . O . . . |
$$ | . . X O O O O X O O . O X . . . . X . |
$$ | X X X X O . X O O . O X X . . O O X . |
$$ | X O O O X X X . . , . . . X . , X . . |
$$ | O O . . O X . . O . . O . . X . . . . |
$$ | . . O . O X . . . . . . O O X . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]




3)
Yep, it is a ko.

Click Here To Show Diagram Code
[go]$$Wc White to play
$$ ---------------------------------------
$$ | 7 4 9 0 1 . . . O X X X . . . . . X . |
$$ | 6 3 X X O . . . . O O X X . X . . . X |
$$ | 5 8 X O . O . . . . O . . O X . X X O |
$$ | . X X O . . . . . , O X . O . X O O O |
$$ | . X O . O . . . . . O X . . O O O X . |
$$ | . O O O . O . . . . . X . X X . O . . |
$$ | . . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . 2 . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |
$$ | . . . X O . X X . X . O . . . O . . . |
$$ | . . X O O O O X O O . O X . . . . X . |
$$ | X X X X O . X O O . O X X . . O O X . |
$$ | X O O O X X X . . , . . . X . , X . . |
$$ | O O . . O X . . O . . O . . X . . . . |
$$ | . . O . O X . . . . . . O O X . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


This post by kvasir was liked by: jlt
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 Post subject: Re: Tsumegos from real games
Post #72 Posted: Sat Nov 27, 2021 12:45 am 
Gosei
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Further comments on problem #28.

Question 1: The following move :b2: also protects, I don't know if it's better or worse than "a".
Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . a . 1 . . . . O X X X . . . . . X . |
$$ | . 2 X X O . . . . O O X X . X . . . X |
$$ | . . X O . O . . . . O . . O X . X X O |
$$ | . X X O . . . . . , O X . O . X O O O |
$$ | . X O . O . . . . . O X . . O O O X . |
$$ | . O O O . O . . . . . X . X X . O . . |
$$ | . . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . . . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |[/go]


Question 3: the following sequence was played in the game.

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


at which point I wondered: should I throw-in at "a" or play at "b" first?

If White plays "a", winning the ko is hard for White since White needs to make an approach at :w9: then win the ko B19.

Click Here To Show Diagram Code
[go]$$Wcm7 :w13: at B19
$$ ---------------------------------------
$$ | 1 X 5 X O . . . O X X X . . . . . X . |
$$ | . O X X O . . . . O O X X . X . . . X |
$$ | O . X O . O . . . . O . . O X . X X O |
$$ | . X X O . . . . . , O X . O . X O O O |
$$ | 3 X O . O . . . . . O X . . O O O X . |
$$ | . O O O . O . . . . . X . X X . O . . |
$$ | . . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . X . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |[/go]


If Black wants to win the ko, then Black doesn't need to answer the throw-in right away, can wait for the approach move :w9: before fighting the ko.

Click Here To Show Diagram Code
[go]$$Wcm7
$$ ---------------------------------------
$$ | 1 X . X O . . . O X X X . . . . . X . |
$$ | 4 O X X O . . . . O O X X . X . . . X |
$$ | O 6 X O . O . . . . O . . O X . X X O |
$$ | . X X O . . . . . , O X . O . X O O O |
$$ | 3 X O . O . . . . . O X . . O O O X . |
$$ | . O O O . O . . . . . X . X X . O . . |
$$ | . . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . X . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |[/go]


In the game, I played A15 which is forcing, and wondered whether I should continue at "a" or "c" (assuming I want to continue locally, which may not be the best choice).

Click Here To Show Diagram Code
[go]$$Wcm7
$$ ---------------------------------------
$$ | a X . X O . . . O X X X . . . . . X . |
$$ | . O X X O . . . . O O X X . X . . . X |
$$ | O . X O . O . . . . O . . O X . X X O |
$$ | 2 X X O . . . . . , O X . O . X O O O |
$$ | 1 X O . O . . . . . O X . . O O O X . |
$$ | c O O O . O . . . . . X . X X . O . . |
$$ | . . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . X . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |[/go]


A move at "c" can be ignored, and either player can choose later to convert the position into a seki or to throw-in and fight the ko. In the game I played "a", Black captured a stone:

Click Here To Show Diagram Code
[go]$$Wcm9
$$ ---------------------------------------
$$ | 1 X d X O . . . O X X X . . . . . X . |
$$ | . O X X O . . . . O O X X . X . . . X |
$$ | O . X O . O . . . . O . . O X . X X O |
$$ | X X X O . . . . . , O X . O . X O O O |
$$ | . X O . O . . . . . O X . . O O O X . |
$$ | 2 O O O . O . . . . . X . X X . O . . |
$$ | e . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . X . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |[/go]


After this the only way to continue for White would be to play "d" and fight the ko. However I made a mistake and blocked at "e" instead and Black lived by double ko...

Click Here To Show Diagram Code
[go]$$Wcm11
$$ ---------------------------------------
$$ | O X . X O . . . O X X X . . . . . X . |
$$ | . O X X O . . . . O O X X . X . . . X |
$$ | O 2 X O . O . . . . O . . O X . X X O |
$$ | X X X O . . . . . , O X . O . X O O O |
$$ | . X O . O . . . . . O X . . O O O X . |
$$ | X O O O . O . . . . . X . X X . O . . |
$$ | 1 . O . X X O O . O . . . O . X . . . |
$$ | . . . . . X X X O . . . X . . . . O . |
$$ | . X . O . . . . O . O . X X X X . O O |
$$ | . . . , . X . . . X O O X O O X . X . |
$$ | . . X . . . . . . . X X O . . O X . . |
$$ | . . . X X . . X . . X O . O . O X . . |[/go]

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