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 Post subject: An interesting tesuji problem? #1 Posted: Wed May 22, 2024 4:58 am
 Lives in sente

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IGS: kvasir
`[go]\$\$B White to play\$\$ . . . . . . . . . . .|\$\$ . , . . . . . X . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . X .|\$\$ . . . . . X . . X O .|\$\$ . , . . O X . X O . .|\$\$ . . . . . O X . O . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . . .|\$\$ ----------------------+[/go]`

I encountered this tesuji problem the other day. I guess it could be said to be from a (middle game) joseki gone wrong. I was perplexed that I didn't think I understood the shape and then I disagreed with the provided solution.

Maybe checking it with the computer has the risk that the answer may fit one position and not others, but I did check in the two positions that follow. It turned out I was right to reject the solution as given and for the right reason but it is an interesting puzzle (I maybe I shouldn't confuse people by copying the incorrect solution here). I do find it to be easier to see the solution in the real game positions, which is maybe the real reasons why those positions are provided. It just seem too abstract somehow without a whole board diagram.
`[go]\$\$B \$\$ +--------------------------------------+\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . X X X . X . . . . . . . . . . . .|\$\$ | . O O X O X X . O . . . . O . . . . .|\$\$ | . . . O O X O . . , . . . . . X . . .|\$\$ | . . . . . O O . . . . . . . . . . . .|\$\$ | . . O . . . . . . . . . . . . X . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . X . . . . . . . . . . . . . . . .|\$\$ | . . . , . . . . . , . . . . . X . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . X . . . . . . . . . . . . . . .|\$\$ | . . X . . . . . . . . . . . . . . X .|\$\$ | . . O X . . . . . . . . . X . . X O .|\$\$ | . . O , . . . . . , . . O X . X O . .|\$\$ | . . . O . O . . . . . . . O X . O . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ +--------------------------------------+[/go]`

`[go]\$\$B \$\$ +--------------------------------------+\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . O . . . . . . . . . . O X . O . .|\$\$ | . . . , . . . . . , . . O X . X O . .|\$\$ | . . . . . . . . . . . . . X . . X O .|\$\$ | . . . . . . . . . . . . . . . . . X .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . , . . . . . , . . . . . X . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . O . . . X . . . . . . . . . . . .|\$\$ | . . . X . . . . . . . . . . . . . . .|\$\$ | . . O X . X . . . , . . . . . X . . .|\$\$ | . . O O O . O . . . . . X . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ +--------------------------------------+[/go]`

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 Post subject: Re: An interesting tesuji problem? #2 Posted: Thu May 23, 2024 1:01 am
 Oza

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The suji that is for everyone to see, is this one:

`[go]\$\$W\$\$ +--------------------------------------+\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . X X X . X . . . . . . . . . . . .|\$\$ | . O O X O X X . O . . . . O . . . . .|\$\$ | . . . O O X O . . , . . . . . X . . .|\$\$ | . . . . . O O . . . . . . . . . . . .|\$\$ | . . O . . . . . . . . . . . . X . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . X . . . . . . . . . . . . . . . .|\$\$ | . . . , . . . . . , . . . . . X . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . X . . . . . . . . . . . . . 3 .|\$\$ | . . X . . . . . . . . . . . . . 1 X 5|\$\$ | . . O X . . . . . . . . . X . 2 X O .|\$\$ | . . O , . . . . . , . . O X . X O 4 .|\$\$ | . . . O . O . . . . . . a O X . O 6 .|\$\$ | . . . . . . . . . . . . b . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ +--------------------------------------+[/go]`

I'm pondering the forcing moves of A or B prior to this basic line of play, or leaving that as aji.

This is probably kvasir's solution and not the tesuji as challenged.

`[go]\$\$W\$\$ +--------------------------------------+\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . X X X . X . . . . . . . . . . . .|\$\$ | . O O X O X X . O . . . . O . . . . .|\$\$ | . . . O O X O . . , . . . . . X . . .|\$\$ | . . . . . O O . . . . . . . . . . . .|\$\$ | . . O . . . . . . . . . . . . X . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . X . . . . . . . . . . . . . . . .|\$\$ | . . . , . . . . . , . . . . . X . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . X . . . . . . . . . . . . . 5 .|\$\$ | . . X . . . . . . . . . . . . . 3 X .|\$\$ | . . O X . . . . . . . . . X . 4 X O .|\$\$ | . . O , . . . . . , . . O X . X O . .|\$\$ | . . . O . O . . . . . . . O X . O . .|\$\$ | . . . . . . . . . . . . . . 2 1 . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ +--------------------------------------+[/go]`

If White exchanges first then she can apply the same cut and capture suji but without losing the two stones in the corner.

`[go]\$\$W\$\$ +--------------------------------------+\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . X X X . X . . . . . . . . . . . .|\$\$ | . O O X O X X . O . . . . O . . . . .|\$\$ | . . . O O X O . . , . . . . . X . . .|\$\$ | . . . . . O O . . . . . . . . . . . .|\$\$ | . . O . . . . . . . . . . . . X . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . X . . . . . . . . . . . . . . . .|\$\$ | . . . , . . . . . , . . . . . X . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . X . . . . . . . . . . . . . . .|\$\$ | . . X . . . . . . . . . . . . . . X .|\$\$ | . . O X . . . . . . . . . X . . X O .|\$\$ | . . O , . . . . . , . d O X . X O 2 .|\$\$ | . . . O . O . . . . . c a O X . O . .|\$\$ | . . . . . . . . . . . . . b 3 1 . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ +--------------------------------------+[/go]`

But then Black can go this way and it's not clearly better for White than the first diagram. Next, Black can further reduce White with a-b-c/d

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 Post subject: Re: An interesting tesuji problem? #3 Posted: Thu May 23, 2024 4:19 am
 Dies with sente

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`[go]\$\$W White to play\$\$ . . . . . . . . . . .|\$\$ . , . . . . . X . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . 9 .|\$\$ . . . . . . . . 7 X .|\$\$ . . . . . X . 8 X O .|\$\$ . , . . O X 6 X O . .|\$\$ . . . . 3 O X 5 O . .|\$\$ . . . . . 2 1 4 . . .|\$\$ . . . . . . . . . . .|\$\$ ----------------------+[/go]`

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 Post subject: Re: An interesting tesuji problem? #4 Posted: Thu May 23, 2024 5:33 am
 Oza

Posts: 2420
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OK I see

`[go]\$\$B White to play\$\$ . . . . . . . . . . .|\$\$ . , . . . . . X . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . O .|\$\$ . . . . . . . . O X 2|\$\$ . . . . . X . X X O .|\$\$ . . . . O X X X O . .|\$\$ . 3 . . O O X O O . .|\$\$ . . . . . X O X . . .|\$\$ . . . . . . 1 . . . .|\$\$ ----------------------+[/go]`

`[go]\$\$B White to play\$\$ . . . . . . . . . . .|\$\$ . , . . . . . X . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . O .|\$\$ . . . . . . . . O X 2|\$\$ . . . . . X . X X O .|\$\$ . . . . O X X X O 1 6|\$\$ . 7 . . O O X O O 4 .|\$\$ . . . . . X O X 3 5 .|\$\$ . . . . . . . . . . .|\$\$ ----------------------+[/go]`

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 Post subject: Re: An interesting tesuji problem? #5 Posted: Fri May 24, 2024 3:56 pm
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Yeah, you got it.

In both whole board position the main line is something like what follows

`[go]\$\$W \$\$ +--------------------------------------+\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . 2 1 4 . . .|\$\$ | . . O . . . . . . . . . 3 O X 5 O . .|\$\$ | . . . , . . . . . 0 . . O X 6 X O . .|\$\$ | . . . . . . . . . . . . . X . 8 X O .|\$\$ | . . . . . . . . . . . . . . . . 7 X .|\$\$ | . . . . . . . . . . . . . . . . . 9 .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . , . . . . . , . . . . . X . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . O . . . X . . . . . . . . . . . .|\$\$ | . . . X . . . . . . . . . . . . . . .|\$\$ | . . O X . X . . . , . . . . . X . . .|\$\$ | . . O O O . O . . . . . X . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ +--------------------------------------+[/go]`

And in the first position it appears to be equally good for black to play in another way instead. I'd say the second way has some appeal, but it does look a little bit like a handicap joseki.

`[go]\$\$W \$\$ +--------------------------------------+\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . X X X . X . . . . . . . . . . . .|\$\$ | . O O X O X X . O . . . . O . . . . .|\$\$ | . . . O O X O . . , . . . . . X . . .|\$\$ | . . . . . O O . . . . . . . . . . . .|\$\$ | . . O . . . . . . . . . . . . X . . .|\$\$ | . . . 0 . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . X . . . . . . . . . . . . . . . .|\$\$ | . . . , . . . . . , . . . . . X . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ | . . . X . . . . . . . . . . . . . . .|\$\$ | . . X . . . . . . . . . . . . . . X .|\$\$ | . . O X . . . . . . . . 6 X . . X O .|\$\$ | . . O , 8 . . . . , . 7 O X 4 X O 2 .|\$\$ | . . . O 9 O . . . . . . . O X 3 O . .|\$\$ | . . . . . . . . . . . . 5 . 1 . . . .|\$\$ | . . . . . . . . . . . . . . . . . . .|\$\$ +--------------------------------------+[/go]`

The solution in the book was odd. It is like some moves were misplaced by a zealous copy editor.

`[go]\$\$W Wrong solution\$\$ ----------------------+\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . O X 1 O . .|\$\$ . , . . O X 2 X O . .|\$\$ . . . . . X . 4 X O .|\$\$ . . . . . . . . 3 X .|\$\$ . . . . . . . . . 5 .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . . .|\$\$ . , . . . . . X . . .|\$\$ . . . . . . . . . . .|[/go]`

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 Post subject: Re: An interesting tesuji problem? #6 Posted: Fri May 24, 2024 6:38 pm
 Oza

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kvasir wrote:
Yeah, you got it...

...

The solution in the book was odd. It is like some moves were misplaced by a zealous copy editor.

`[go]\$\$W Wrong solution\$\$ ----------------------+\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . O X 1 O . .|\$\$ . , . . O X 2 X O . .|\$\$ . . . . . X . 4 X O .|\$\$ . . . . . . . . 3 X .|\$\$ . . . . . . . . . 5 .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . . .|\$\$ . , . . . . . X . . .|\$\$ . . . . . . . . . . .|[/go]`

This position is in Ishida vol 3, with the comment, "(tricked) Black 2 is just what White wants. If Black makes a second hane at 4, White has the troublesome move at 5. Letting White connect is awful, but if Black plays 'a', white captures with 'b' and 'c'." See the diagram below for the numbering used here. No alternatives to 'a' are considered.

`[go]\$\$W Ishida diagram 49 on page 131 \$\$ ----------------------+\$\$ . . . . . . . . . . .|\$\$ . . . . c 4 3 . . . .|\$\$ . . . . . b 2 1 O . .|\$\$ . B . . . . . X 5 . .|\$\$ . . . . . . . a X . .|\$\$ . . . . . . X X O . .|\$\$ . . . . . . . O . . .|\$\$ . . . . . . . . . . .|\$\$ . . . . . . . . . . .|\$\$ . , . . . . . . . . .|\$\$ . . . . . . . . . . .|[/go]`

The same diagram appears in the Igo Daijiten with the exception that the marked extension is missing. These seem like untested lines, however, not actual joseki. There are no sample games given or mentioned. Are the reference positions from actual games?

_________________
Dave Sigaty
"Short-lived are both the praiser and the praised, and rememberer and the remembered..."
- Marcus Aurelius; Meditations, VIII 21

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 Post subject: Re: An interesting tesuji problem? #7 Posted: Fri May 24, 2024 11:57 pm
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ez4u wrote:
The same diagram appears in the Igo Daijiten with the exception that the marked extension is missing. These seem like untested lines, however, not actual joseki. There are no sample games given or mentioned. Are the reference positions from actual games?

`[go]\$\$W The usual joseki way.\$\$ | . . . . . . . . . . .\$\$ | . . . , . . . . . , .\$\$ | . . . . . . . . . . .\$\$ | . . . . . . . . . . .\$\$ | . . . O . . . . . . .\$\$ | . . O X X . . . . . .\$\$ | . . X . . . . . . . .\$\$ | . . . X . . . . . X .\$\$ | . . O . . . . . . . .\$\$ | . . . . 1 a . . . . .\$\$ | . . . . . . . . . . .\$\$ +----------------------[/go]`

I think the joseki is to play a keima a little bit earlier (or a large keima). All of the pro games I could find had this way of playing. As a tesuji problem it doesn't matter that the moves leading there aren't good.

BTW if you remove the star point on the side then the large keima was played by alpha zero.

You can take a look at the examples games and the alpha zero game if you are curious how they were played.

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