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Tsumegos from real games

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Tsumegos from real games

Posted: Sat Nov 23, 2019 3:43 am
by jlt
In this thread I will post some tsumegos that I missed in my games. SDKs should find them fairly easy, but seeing the solution in byo-yomi without knowing if a solution exists is another matter.

The following is from a Fox 3k vs. 3k game (after a 6-game losing streak I was demoted from 2k to 3k, but afterwards won 11 games in a row so I will be back to at least 2k).

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

Re: Tsumegos from real games

Posted: Sat Nov 23, 2019 7:48 am
by Bill Spight
jlt wrote:Black to play and kill something.
:tmbup:

Re: Tsumegos from real games

Posted: Sat Nov 23, 2019 11:32 am
by Joaz Banbeck
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . O X . . . . . . . . . . . . . |
$$ | . O O O O X . . O . X . O . X . . . . |
$$ | . O X X X X . O . , X O . O . X . . . |
$$ | X X X X O O O . . . X . . . . X . . . |
$$ | X O O X X X . . . . . . O . O O X X . |
$$ | X X O O . . O O . O X X . O . . O . . |
$$ | . O . O X X X O . O . . . . . . O . . |
$$ | 1 . O O X . X X O . O X . O . O . . . |
$$ | . . O X X . X X O X O X O . . O X X . |
$$ | . O X X O X . X X O O X X O O X . . . |
$$ | . O O O . O O O X X X . . X X . . X . |
$$ | . X . . O O X X . . . . . . . . . X . |
$$ | . . X X . X . . . X . . . . . X X O . |
$$ | . . O . X . . . X O X X . . X . O O . |
$$ | . . . O . X . X . O O . . X . O . . . |
$$ | . . O . O X . . O . . O . X O . O O . |
$$ | . . O . O X O O . O . . . X X O O . . |
$$ | . . . O X X . . . . . . . . X X X O . |
$$ ---------------------------------------[/go]

Re: Tsumegos from real games

Posted: Sun Nov 24, 2019 4:17 am
by jlt
This move indeed kills something.

Re: Tsumegos from real games

Posted: Sun Nov 24, 2019 6:36 am
by explo
jlt wrote:This move indeed kills something.
Was it the move you had in mind? I think white can play A8 to save half the group in sente, but I don't know if it was actually played.

Re: Tsumegos from real games

Posted: Sun Nov 24, 2019 8:52 am
by jlt
Yes, that's the move I had in mind and that I didn't see during the game. That move indeed kills half of the white group.

The actual game was ridiculous, both players didn't see that the group could be killed between moves 170 and 208, and on the other hand another white group died at move 196 although it could have survived easily, among other big mistakes.

Re: Tsumegos from real games

Posted: Sun Nov 24, 2019 1:38 pm
by Mike Novack
explo wrote:
jlt wrote:This move indeed kills something.
Was it the move you had in mind? I think white can play A8 to save half the group in sente, but I don't know if it was actually played.
A8? And not B11? What am I not seeing?

Re: Tsumegos from real games

Posted: Sun Nov 24, 2019 1:57 pm
by jlt
I don't know if everyone is talking about the same thing, but here is a variation that kills the whole group if Black A11 and if White tries to save everything.
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . O X . . . . . . . . . . . . . |
$$ | . O O O O X . . O . X . O . X . . . . |
$$ | . O X X X X . O . , X O . O . X . . . |
$$ | X X X X O O O . . . X . . . . X . . . |
$$ | X O O X X X . . . . . . O . O O X X . |
$$ | X X O O . . O O . O X X . O . . O . . |
$$ | 3 O . O X X X O . O . . . . . . O . . |
$$ | 1 2 O O X . X X O . O X . O . O . . . |
$$ | 4 . O X X . X X O X O X O . . O X X . |
$$ | . O X X O X . X X O O X X O O X . . . |
$$ | 5 O O O . O O O X X X . . X X . . X . |
$$ | . X . . O O X X . . . . . . . . . X . |
$$ | . . X X . X . . . X . . . . . X X O . |
$$ | . . O . X . . . X O X X . . X . O O . |
$$ | . . . O . X . X . O O . . X . O . . . |
$$ | . . O . O X . . O . . O . X O . O O . |
$$ | . . O . O X O O . O . . . X X O O . . |
$$ | . . . O X X . . . . . . . . X X X O . |
$$ ---------------------------------------[/go]
(In the game I read until :w4: but didn't see that B10 was a false eye. :oops: )

Re: Tsumegos from real games

Posted: Sun Nov 24, 2019 4:17 pm
by EricBackus
To be honest, the first thing that jumped out at me on this position was a question of whether the white upper left corner is completely safe. Black has a descent on one side, and it is black's move. After looking it up, I think it probably is safe, but it's not at all obvious to me as an SDK player. Maybe there's a thousand-year ko hidden in there somewhere.

Re: Tsumegos from real games

Posted: Sun Nov 24, 2019 6:15 pm
by dfan
Here's my take on the upper left corner.

In the normal "Long L" shape, Black can make a 10,000 year ko:
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------
$$ | . 4 5 . . . .
$$ | 2 1 3 . O X .
$$ | . O O O O X .
$$ | . X X X X X .
$$ | . . . . . . .[/go]
If White has an extra liberty, she can resist and live with the tesuji of :w4::
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------
$$ | 7 6 4 5 . . .
$$ | 2 1 3 . O X .
$$ | . O O O O X .
$$ | . X X X a X .
$$ | . . . . . . .[/go]
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------
$$ | X 8 . X 9 . .
$$ | O X X 0 O X .
$$ | . O O O O X .
$$ | . X X X a X .
$$ | . . . . . . .[/go]
:w10: would be self-atari if a were filled, which is why White needs the liberty.

This is effectively the same situation as the game, in that White has one extra liberty than in the 10,000-year-ko situation, which I've labeled b:
Click Here To Show Diagram Code
[go]$$Bc
$$ ---------------
$$ | . . . . . . .
$$ | . . . . O X .
$$ | . O O O O X .
$$ | b O X X X X .
$$ | X X X X . . .[/go]
I don't see any good tricks for Black (involving A17, say), so White looks safe to me.

Re: Tsumegos from real games

Posted: Wed Jan 01, 2020 10:40 am
by jlt
Tsumego #2.

This one should be fairly easy. I am white, 5k on Tygem (possibly underranked, I haven't had many games there recently).

1. White to play. What is the status of the upper left corner?
2. Some moves of White are better than others. How can Black punish if White chooses a suboptimal move?
Click Here To Show Diagram Code
[go]$$Wc White to play
$$ ---------------------------------------
$$ | . . X . X . . . . . X . . . . . . . . |
$$ | . . X X O O . . . X O X X . . . X X . |
$$ | . . X O O X . . . O O O X X X X O O . |
$$ | . X . O . . . O . , . O O O X O . . . |
$$ | . O . . . . . . . . O . . . O O . . . |
$$ | . . O O O . . . . X . . . . . . . . . |
$$ | . X X X X O O O . X O O X X O . . . . |
$$ | . . . . . X X O O O X . X . X O . . . |
$$ | . . . . . . . X . O X . X . X O . . . |[/go]
In the game, I played the following move but Black didn't find the punishment.
A18

Re: Tsumegos from real games

Posted: Wed Jan 01, 2020 3:37 pm
by xela
Status:
The black group is a dead shape, but black has threats to connect out below, so white shouldn't expect to kill the group unconditionally.
Black replies to your move:
Click Here To Show Diagram Code
[go]$$Wc Two ways to make ko
$$ ---------------------------------------
$$ | . . X . X . . . . . X . . . . . . . . |
$$ | 1 3 X X O O . . . X O X X . . . X X . |
$$ | 2 . X O O X . . . O O O X X X X O O . |
$$ | 7 X . O . . . O . , . O O O X O . . . |
$$ | 4 O . . . . . . . . O . . . O O . . . |
$$ | 5 6 O O O . . . . X . . . . . . . . . |
$$ | . X X X X O O O . X O O X X O . . . . |
$$ | . . . . . X X O O O X . X . X O . . . |
$$ | . . . . . . . X . O X . X . X O . . . |[/go]
Click Here To Show Diagram Code
[go]$$Bc Continuation: the more complicated ko -- black can't connect at A16!
$$ ---------------------------------------
$$ | . . X . X . . . . . X . . . . . . . . |
$$ | O O X X O O . . . X O X X . . . X X . |
$$ | X 2 X O O X . . . O O O X X X X O O . |
$$ | O X 4 O . . . O . , . O O O X O . . . |
$$ | 3 O 1 . . . . . . . O . . . O O . . . |
$$ | O X O O O . . . . X . . . . . . . . . |
$$ | . X X X X O O O . X O O X X O . . . . |
$$ | . . . . . X X O O O X . X . X O . . . |
$$ | . . . . . . . X . O X . X . X O . . . |[/go]
Click Here To Show Diagram Code
[go]$$Wc Black's best reply: alive
$$ ---------------------------------------
$$ | 6 7 X . X . . . . . X . . . . . . . . |
$$ | 1 4 X X O O . . . X O X X . . . X X . |
$$ | 5 8 X O O X . . . O O O X X X X O O . |
$$ | 2 X . O . . . O . , . O O O X O . . . |
$$ | 3 O . . . . . . . . O . . . O O . . . |
$$ | . . O O O . . . . X . . . . . . . . . |
$$ | . X X X X O O O . X O O X X O . . . . |
$$ | . . . . . X X O O O X . X . X O . . . |
$$ | . . . . . . . X . O X . X . X O . . . |[/go]
Is this the best move for white?
Click Here To Show Diagram Code
[go]$$Wc This way, black can't avoid the ko
$$ ---------------------------------------
$$ | . . X . X . . . . . X . . . . . . . . |
$$ | . 3 X X O O . . . X O X X . . . X X . |
$$ | 2 . X O O X . . . O O O X X X X O O . |
$$ | 1 X . O . . . O . , . O O O X O . . . |
$$ | 4 O 7 . . . . . . . O . . . O O . . . |
$$ | 5 6 O O O . . . . X . . . . . . . . . |
$$ | . X X X X O O O . X O O X X O . . . . |
$$ | . . . . . X X O O O X . X . X O . . . |
$$ | . . . . . . . X . O X . X . X O . . . |[/go]

Re: Tsumegos from real games

Posted: Wed Jan 01, 2020 6:07 pm
by zermelo
Mike Novack wrote:
explo wrote:
jlt wrote:This move indeed kills something.
Was it the move you had in mind? I think white can play A8 to save half the group in sente, but I don't know if it was actually played.
A8? And not B11? What am I not seeing?
A8 allows connection to lower left by B6, shown below. This is a good shape to know, as it comes up now and then in games:

Re: Tsumegos from real games

Posted: Thu Jan 02, 2020 2:17 am
by jlt
@xela:
Click Here To Show Diagram Code
[go]$$Wc Black's best reply: alive
$$ ---------------------------------------
$$ | 6 7 X . X . . . . . X . . . . . . . . |
$$ | 1 4 X X O O . . . X O X X . . . X X . |
$$ | 5 8 X O O X . . . O O O X X X X O O . |
$$ | 2 X . O . . . O . , . O O O X O . . . |
$$ | 3 O . . . . . . . . O . . . O O . . . |
$$ | . . O O O . . . . X . . . . . . . . . |
$$ | . X X X X O O O . X O O X X O . . . . |
$$ | . . . . . X X O O O X . X . X O . . . |
$$ | . . . . . . . X . O X . X . X O . . . |[/go]
But White can play :w5: differently:
Click Here To Show Diagram Code
[go]$$Wc Still a ko
$$ ---------------------------------------
$$ | 6 7 X . X . . . . . X . . . . . . . . |
$$ | 1 4 X X O O . . . X O X X . . . X X . |
$$ | . . X O O X . . . O O O X X X X O O . |
$$ | 2 X 5 O . . . O . , . O O O X O . . . |
$$ | 3 O . . . . . . . . O . . . O O . . . |
$$ | . . O O O . . . . X . . . . . . . . . |
$$ | . X X X X O O O . X O O X X O . . . . |
$$ | . . . . . X X O O O X . X . X O . . . |
$$ | . . . . . . . X . O X . X . X O . . . |[/go]
So it seems that if White's move is at A18, Black's best response is to threaten to connect by ko the corner group with the side group.
Click Here To Show Diagram Code
[go]$$Wc This way, black can't avoid the ko
$$ ---------------------------------------
$$ | . . X . X . . . . . X . . . . . . . . |
$$ | . 3 X X O O . . . X O X X . . . X X . |
$$ | 2 . X O O X . . . O O O X X X X O O . |
$$ | 1 X . O . . . O . , . O O O X O . . . |
$$ | 4 O 7 . . . . . . . O . . . O O . . . |
$$ | 5 6 O O O . . . . X . . . . . . . . . |
$$ | . X X X X O O O . X O O X X O . . . . |
$$ | . . . . . X X O O O X . X . X O . . . |
$$ | . . . . . . . X . O X . X . X O . . . |[/go]
The following response by White looks better, since even if Black wins the ko, the corner group is still disconnected.
Click Here To Show Diagram Code
[go]$$Wc Better for White
$$ ---------------------------------------
$$ | 6 . X . X . . . . . X . . . . . . . . |
$$ | . 4 X X O O . . . X O X X . . . X X . |
$$ | 2 7 X O O X . . . O O O X X X X O O . |
$$ | 1 X 5 O . . . O . , . O O O X O . . . |
$$ | 3 O . . . . . . . . O . . . O O . . . |
$$ | . . O O O . . . . X . . . . . . . . . |
$$ | . X X X X O O O . X O O X X O . . . . |
$$ | . . . . . X X O O O X . X . X O . . . |
$$ | . . . . . . . X . O X . X . X O . . . |[/go]

Re: Tsumegos from real games

Posted: Thu Jan 02, 2020 3:46 am
by xela
So many different ways to make ko! Thanks for the clear explanation.
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