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 Post subject: Understanding a san-san joseki
Post #1 Posted: Wed Dec 01, 2021 10:23 am 
Lives in sente

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Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . a . . .
$$ | . . O O . b . . .
$$ | . . . X X . . . .
$$ | . O . . . . . . .
$$ | . . . . . . . . .
$$ | . . . X . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -----------------[/go]


In the position above the known continuation for white is to play at a. My qestion is the following: why not playing at b?

Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . a . . .
$$ | . . O O . b . . .
$$ | . . . X X . . . .
$$ | . O . . . . . . .
$$ | . c . . . . . . .
$$ | . . . X . . . . .
$$ | . . d . . . . . .
$$ | . . . . . . . . .
$$ -----------------[/go]


I read that "b" is not as good as "a" because, due to the potentiality to play:

Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . 3 2 4 . . .
$$ | . . O O 1 O . . .
$$ | . . . X X . . . .
$$ | . O . . . . . . .
$$ | . c . . . . . . .
$$ | . . . X . . . . .
$$ | . . d . . . . . .
$$ | . . . . . . . . .
$$ -----------------[/go]

black can play at "c" in sente and as a consequence, white cannot expect to play at "d".

Can someone clarify this point in order for me to understand why "a" is better than "b"

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

I tried to begin by :b1: :w2: above but I do not see how the push at "e" can help black.

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 Post subject: Re: Understanding a san-san joseki
Post #2 Posted: Wed Dec 01, 2021 11:44 am 
Oza

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A joseki is not a tsumego problem. You can't expect an instant refutation. Instead your approach should be to adopt a healthy life style and think of the future - make strings that can safely be welded into groups. This is what the knight's move 'b' does. The jump to 'a' allows Black to push in and leave White with four strings and three cutting points, and none of these strings will have the minimum 'five alive' liberties needed to survive an eventual contact fight.

To put it another way, White is just painting a bull's eye on his back (and front, and sides...). Compare Black's position - he is el toro. But again, just for the moment. He has to think about the future, too. Otherwise prime beef will end up as corned beef. (Black's main task is to make the two-sides-of-a-centre-rectangle position the Japanese describe as hoisting a flag (hata wo motsu)).

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 Post subject: Re: Understanding a san-san joseki
Post #3 Posted: Wed Dec 01, 2021 11:48 am 
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It comes down to forceful moves. With the keima there are follow-ups for black but they are not very forceful against the corner group. With the straight jump there are many forceful moves that black can use.

With the straight jump, if you want to block from the left side then I think you'd want to do something like :b1: - :b3:. It does depend on if :b1: is sente and the cutting fight. You may try to get :b1: in early to make sure it will be easy to block, otherwise it is possible that white plays a instead of :w2:.

Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . . . .
$$ | . . O O a O 2 . .
$$ | . . . X X 1 . . .
$$ | . O . . . . . . .
$$ | . . . . . . . . .
$$ | . 3 . X . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -----------------[/go]


With the keima one can play follow-ups at :b1: or a that help with blocking from either side but they are not forceful. Black could also play b but it is likely to be cut to pieces.

Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . O . .
$$ | . . O O . . b . .
$$ | . . . X X . . a .
$$ | . O . . . . . 1 .
$$ | . . . . . . . . .
$$ | . . . X . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -----------------[/go]


Alternatively you could try this but it may not work in general. It is also expensive and there is a ladder that may or may not be good to use.

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


Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . 2 . O . . .
$$ | . 1 O X O . O .
$$ | . X O O X O . . .
$$ | . O X X X . . . .
$$ | . O . . . . . . .
$$ | . 3 . . . . . . .
$$ | . a . X . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -----------------[/go]


===EDIT=== :b3: in the last diagram is actually still better at a so the nose-tsuki is maybe not very relevant.

The last diagrams also demonstrate some of the shortage of liberties involved with the straight jump move.

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


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


In case white refuses to capture then black has useful forceful moves around a - e.

Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . . .
$$ | . . . 4 2 3 a . . .
$$ | . . O O 1 O O b d .
$$ | . . . X X X . c e .
$$ | . O . . . . . . . .
$$ | . . O O X X . . . .
$$ | . X X X O . . . . .
$$ | . . . . O . . . . .
$$ | . . . X . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ -----------------[/go]

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 Post subject: Re: Understanding a san-san joseki
Post #4 Posted: Wed Dec 01, 2021 2:21 pm 
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kvasir wrote:
It comes down to forceful moves. With the keima there are follow-ups for black but they are not very forceful against the corner group. With the straight jump there are many forceful moves that black can use.

With the straight jump, if you want to block from the left side then I think you'd want to do something like :b1: - :b3:. It does depend on if :b1: is sente and the cutting fight. You may try to get :b1: in early to make sure it will be easy to block, otherwise it is possible that white plays a instead of :w2:.

Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . . . .
$$ | . . O O a O 2 . .
$$ | . . . X X 1 . . .
$$ | . O . . . . . . .
$$ | . . . . . . . . .
$$ | . 3 . X . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -----------------[/go]


With the keima one can play follow-ups at :b1: or a that help with blocking from either side but they are not forceful. Black could also play b but it is likely to be cut to pieces.

Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . O . .
$$ | . . O O . . b . .
$$ | . . . X X . . a .
$$ | . O . . . . . 1 .
$$ | . . . . . . . . .
$$ | . . . X . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -----------------[/go]


Alternatively you could try this but it may not work in general. It is also expensive and there is a ladder that may or may not be good to use.

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


Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . 2 . O . . .
$$ | . 1 O X O . O .
$$ | . X O O X O . . .
$$ | . O X X X . . . .
$$ | . O . . . . . . .
$$ | . 3 . . . . . . .
$$ | . a . X . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -----------------[/go]


===EDIT=== :b3: in the last diagram is actually still better at a so the nose-tsuki is maybe not very relevant.

The last diagrams also demonstrate some of the shortage of liberties involved with the straight jump move.

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


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


In case white refuses to capture then black has useful forceful moves around a - e.

Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . . .
$$ | . . . 4 2 3 a . . .
$$ | . . O O 1 O O b d .
$$ | . . . X X X . c e .
$$ | . O . . . . . . . .
$$ | . . O O X X . . . .
$$ | . X X X O . . . . .
$$ | . . . . O . . . . .
$$ | . . . X . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ -----------------[/go]


Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . O O . O O . .
$$ | . . . X X X . . .
$$ | . O . . . . . . .
$$ | . . O O X X . . .
$$ | . X X X O . . . .
$$ | . . . . O . . . .
$$ | . . . X . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -----------------[/go]

Your above example is very interesting Kvasir.

Click Here To Show Diagram Code
[go]$$B
$$ -------------------
$$ | . . . . . . . . .
$$ | . . . . . a . .
$$ | . . O O . b . . .
$$ | . . . X X . . . .
$$ | . O . . . . . . .
$$ | . . . c . . . . .
$$ | . . . X . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -------------------[/go]

IOW an advantage to play "a" instead of "b" is that white can more easily attack at "c" without being stressed by a damezumari.

Click Here To Show Diagram Code
[go]$$W
$$ -------------------
$$ | . . . . . . . . .
$$ | . . . . . . a . .
$$ | . . . O O . b d .
$$ | . . c . X X . . .
$$ | . . X . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -------------------[/go]

This other situation seems very different. This time if white chooses the low move at "a" then black pressing move at "d" is probably sente. If instead white chooses the move at "b" then a future white move at "c" do not seem to create a damezumari.

Is it correct understanding?

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 Post subject: Re: Understanding a san-san joseki
Post #5 Posted: Wed Dec 01, 2021 3:21 pm 
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Gérard TAILLE wrote:

Click Here To Show Diagram Code
[go]$$W
$$ -------------------
$$ | . . . . . . . . .
$$ | . . . . . . a . .
$$ | . . . O O . b d .
$$ | . . c . X X . . .
$$ | . . X . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -------------------[/go]


This other situation seems very different. This time if white chooses the low move at "a" then black pressing move at "d" is probably sente. If instead white chooses the move at "b" then a future white move at "c" do not seem to create a damezumari.

Is it correct understanding?


There is a shortage of liberties.

For example this exciting joseki that can happen with different pincers.

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


Click Here To Show Diagram Code
[go]$$Bcm11
$$ -------------------
$$ | . . . . . . . . .
$$ | . 1 X . O O . . .
$$ | 3 O X O O X O . .
$$ | . X O O X X . . .
$$ | . 2 X X 4 6 . . .
$$ | . 5 . . . . . . .
$$ | . . O . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ -------------------[/go]


And this less exciting joseki.

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


Click Here To Show Diagram Code
[go]$$Bcm11
$$ -------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . 2 X O O . . . . . . . . . . . . |
$$ | . . 1 O O X O O . . . . . . . . . . . |
$$ | . . . . X X X X O O . . . . . O . . . |
$$ | . . X . . . . . X . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ -------------------[/go]


Actually it is exciting for black (only) when it goes this way and black is strong in the other corner.

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


Isn't this the main reason for playing the keima? When black (the leaning player) has strong stones in the other corner the value of the straight jump is not as much as that of a stronger shape in the corner. Maybe there is something more to it?

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

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 Post subject: Re: Understanding a san-san joseki
Post #6 Posted: Thu Dec 02, 2021 10:03 am 
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kvasir wrote:
Click Here To Show Diagram Code
[go]$$W
$$ -------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O O . 1 . . . . . . . . O . . . . |
$$ | . . . X X . . . . , . . . . . , O . . |
$$ | . O . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ -------------------[/go]


Thank you Kvasir I begin to understand.
Comming back to san-san. If the upper right corner is strong for white as in the diagram above isn't it a good idea to play the jump instead of the keima in order to avoid a too low position:

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

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 Post subject: Re: Understanding a san-san joseki
Post #7 Posted: Thu Dec 02, 2021 10:41 am 
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I think this isn't that easy of a question and don't fully agree with the explanations. I saw a different one (on weiqitv?) years ago regarding a black move at a setting up the tesuji b if white plays the jump. But I suppose it is complicated enough that several variations are required.

But anyway:

Considering Iyama's surprising low keima in the recent Nongshim cup game vs Fan Tingyu, I would add a clarification. If W is very solid in the upper right, then W also has no interest in playing the jump on the 3rd line and letting B push on the 4th line in sente.

This is because even though the upper side is big, it is actually reduced if B gets to push for strength on the 4th line.

Imagine this sort of diagram.

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


White's moves at c and d remain big to attack and use the right thick shape though probably premature. It is normally better to attack from below/centre and try to cut only after black has added another move (so that capturing it is even more efficient).

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 Post subject: Re: Understanding a san-san joseki
Post #8 Posted: Thu Dec 02, 2021 11:06 am 
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dhu163 wrote:
I think this isn't that easy of a question and don't fully agree with the explanations. I saw a different one (on weiqitv?) years ago regarding a black move at a setting up the tesuji b if white plays the jump. But I suppose it is complicated enough that several variations are required.

But anyway:

Considering Iyama's surprising low keima in the recent Nongshim cup game vs Fan Tingyu, I would add a clarification. If W is very solid in the upper right, then W also has no interest in playing the jump on the 3rd line and letting B push on the 4th line in sente.

This is because even though the upper side is big, it is actually reduced if B gets to push for strength on the 4th line.

Imagine this sort of diagram.

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


White's moves at c and d remain big to attack and use the right thick shape though probably premature. It is normally better to attack from below/centre and try to cut only after black has added another move (so that capturing it is even more efficient).


With such very strong white position in the upper right corner I feel that black :b2: is an overplay. Isn't it better to play the following one (mentionned already by Kvasir):

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

that way it is not easy for white to use her strength efficiently.

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 Post subject: Re: Understanding a san-san joseki
Post #9 Posted: Sat Dec 04, 2021 1:24 pm 
Judan

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I would even question the description of this sequence as joseki these days:

Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . a . . .
$$ | . . O O c b . . .
$$ | . . . X X . . . .
$$ | . O . . . . . . .
$$ | . . . . . . . . .
$$ | . . . B . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]


From reviewing with AI, I learnt it is almost always better for black to turn at 'c' and switch to the side rather than the floaty marked jump. Corners then sides then centre. Standard theory, even more relevant now, is white should push from the side that makes them less sad if black does block, i.e. you don't want black's block to co-ordinate with black potential on the top side in this example, so if black did have a top side position you want to push from the left so that your knight slide undermines his top side potential. And from before AI (and they agree) I learnt that the shoulder hit joseki to a 3-3 is not really a general purpose joseki because it's normally good for the 3-3 player particuarly if you take gote: it's a special purpose joseki when moyos are important.

P.S. Another way to see how slack that black centre jump is a tewari and comparison to modern 3-3 invasion joseki: imagine white doesn't slide on the left but directly slides on the top, then for 5 black should block and we revert to the 3-3 invasion joseki with black starting at 4-4 (maybe pre-AI and direct 3-3 invasions we would think this position is slightly good for black). 5 is a really important point here to give black eye potential on the left and also crucially give white some shape/liberty troubles in future with a/b/c etc which can help black build shape for himself in future.
Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . c 4 . . .
$$ | . a O 2 . b . . .
$$ | . . 5 1 3 . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]


But instead black tenukid, and then white got the slide in sente which is huge for points and eyespace and liberties and fixes all those shape tactics black had against the white group.
Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . 4 . . .
$$ | . . O 2 . . . . .
$$ | . . . 1 3 . . . .
$$ | . 6 . . . . . . .
$$ | . . . . . . . . .
$$ | . . . 7 . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]


This post by Uberdude was liked by 2 people: ez4u, Joaz Banbeck
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 Post subject: Re: Understanding a san-san joseki
Post #10 Posted: Sun Dec 05, 2021 5:02 am 
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Uberdude wrote:
I would even question the description of this sequence as joseki these days:

Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . a . . .
$$ | . . O O c b . . .
$$ | . . . X X . . . .
$$ | . O . . . . . . .
$$ | . . . . . . . . .
$$ | . . . B . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]


From reviewing with AI, I learnt it is almost always better for black to turn at 'c' and switch to the side rather than the floaty marked jump. Corners then sides then centre. Standard theory, even more relevant now, is white should push from the side that makes them less sad if black does block, i.e. you don't want black's block to co-ordinate with black potential on the top side in this example, so if black did have a top side position you want to push from the left so that your knight slide undermines his top side potential. And from before AI (and they agree) I learnt that the shoulder hit joseki to a 3-3 is not really a general purpose joseki because it's normally good for the 3-3 player particuarly if you take gote: it's a special purpose joseki when moyos are important.

P.S. Another way to see how slack that black centre jump is a tewari and comparison to modern 3-3 invasion joseki: imagine white doesn't slide on the left but directly slides on the top, then for 5 black should block and we revert to the 3-3 invasion joseki with black starting at 4-4 (maybe pre-AI and direct 3-3 invasions we would think this position is slightly good for black). 5 is a really important point here to give black eye potential on the left and also crucially give white some shape/liberty troubles in future with a/b/c etc which can help black build shape for himself in future.
Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . c 4 . . .
$$ | . a O 2 . b . . .
$$ | . . 5 1 3 . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]


But instead black tenukid, and then white got the slide in sente which is huge for points and eyespace and liberties and fixes all those shape tactics black had against the white group.
Click Here To Show Diagram Code
[go]$$B
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . 4 . . .
$$ | . . O 2 . . . . .
$$ | . . . 1 3 . . . .
$$ | . 6 . . . . . . .
$$ | . . . . . . . . .
$$ | . . . 7 . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]


Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . 1 3 a . . . .
$$ | . . . 2 4 . . . .
$$ | . 5 . . . . . . .
$$ | . . . . . . . . .
$$ | . . . b . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

Interesting point Uberdude. How for black to choose between "a" and "b" ?
My feeling is the following: because it is white who choose the direction of :w3: I assume that in the diagram above the left side is more valuable than the upper side. If that is true then a black answer at "b" seems more natural than the block at "a.
Another view could be also to say that the upper right corner could be not really settled. In that case isn't it an interesting option for black to play tenuki and see how the upper right corner is settled before returning in this upper left corner and choose between "a" and "b"?

BTW it is the same idea in the following case:
Click Here To Show Diagram Code
[go]$$B
$$ -----------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O O X . . . . . . . . . . . . . |
$$ | . . O . X b a . . , . . . . . O . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

Before choosing between "a" and "b" it could be interesting for black to play a kakari in the upper right corner isn't it?

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 Post subject: Re: Understanding a san-san joseki
Post #11 Posted: Sun Dec 05, 2021 8:54 am 
Judan

Posts: 6706
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Gérard TAILLE wrote:

Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . 1 3 a . . . .
$$ | . . . 2 4 . . . .
$$ | . 5 . . . . . . .
$$ | . . . . . . . . .
$$ | . . . b . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

Interesting point Uberdude. How for black to choose between "a" and "b" ?
My feeling is the following: because it is white who choose the direction of :w3: I assume that in the diagram above the left side is more valuable than the upper side. If that is true then a black answer at "b" seems more natural than the block at "a.


But if the left side is valuable, neither a nor b is good. But at least a is locally ok; that's another lesson from AI: local efficiency is more important than direction, so to play a move that is locally bad for a global direction reason needs an even higher threshold than humans tended to think before.

If the left side is valuable, black should simply approach from the left side (a few choices around 2), rather than the centre with the shoulder hit.
Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . 1 . . . . . .
$$ | . . . , . . . . .
$$ | . . a b . . . . .
$$ | . . 2 c . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]


This post by Uberdude was liked by: Harleqin
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 Post subject: Re: Understanding a san-san joseki
Post #12 Posted: Mon Dec 06, 2021 9:36 am 
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Uberdude wrote:
Gérard TAILLE wrote:

Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . 1 3 a . . . .
$$ | . . . 2 4 . . . .
$$ | . 5 . . . . . . .
$$ | . . . . . . . . .
$$ | . . . b . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

Interesting point Uberdude. How for black to choose between "a" and "b" ?
My feeling is the following: because it is white who choose the direction of :w3: I assume that in the diagram above the left side is more valuable than the upper side. If that is true then a black answer at "b" seems more natural than the block at "a.


But if the left side is valuable, neither a nor b is good. But at least a is locally ok; that's another lesson from AI: local efficiency is more important than direction, so to play a move that is locally bad for a global direction reason needs an even higher threshold than humans tended to think before.

If the left side is valuable, black should simply approach from the left side (a few choices around 2), rather than the centre with the shoulder hit.
Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . 1 . . . . . .
$$ | . . . , . . . . .
$$ | . . a b . . . . .
$$ | . . 2 c . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]


I fully understand that an approach from the left side may be interesting but I have difficulty to understand what you mean with local efficiency.
Assume the left side is more valuable than the upper side:

Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . 1 3 a . . . .
$$ | . . . 2 4 . . . .
$$ | . 5 . . . . . . .
$$ | . . . . . . . . .
$$ | . . . 6 . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

Because you consider :b6: is not efficient locally you suggest instead to play

Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . 1 . . . . . .
$$ | . . . , . . . . .
$$ | . . a b . . . . .
$$ | . . 2 c . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]

It's not easy for me to see why such side approach is locally more efficient. Could you explain a little more?

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 Post subject: Re: Understanding a san-san joseki
Post #13 Posted: Tue Dec 07, 2021 3:42 pm 
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Uberdude wrote:
I would even question the description of this sequence as joseki these days:

Click Here To Show Diagram Code
[go]$$W
$$ -----------------
$$ | . . . . . . . . .
$$ | . . . . . a . . .
$$ | . . O O c b . . .
$$ | . . . X X . . . .
$$ | . O . . . . . . .
$$ | . . . . . . . . .
$$ | . . . B . . . . .
$$ | . . . . . . . . .
$$ | . . . . . . . . .[/go]


From reviewing with AI, I learnt it is almost always better for black to turn at 'c' and switch to the side rather than the floaty marked jump.


I get interested in these types of claims and have a tool I built just for my own amusement to try to get some data around this kind of thing.

I gathered 200 real board positions with this pattern in one of the quadrants (and no other stones in that 10x10 quadrant.) And noted the distribution of moves that Katago chooses (40b before community training).

Click Here To Show Diagram Code
[go]$$W
$$ -------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . O O a . . . . .
$$ | . . . X X . . . . d
$$ | . O . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . b e . . . . .
$$ | . . . f c . . . . .
$$ | . . . . . . . . . .[/go]


in 102 out of the 200 whole board positions, katago wants to tenuki (I wouldn't interpret this as meaning that katago thinks that this is the end of the natural local sequence in most cases - often katago just thinks that the humans have missed something and want's to come back to this corner after it's tidied the other part of the board up.)

For the remaining 98 positions where katago wants to play something local:
a is chosen 91 of those times.
b and c are chosen twice each
d, e and f are each chosen once each (perhaps d belongs in the tenuki bucket?)

I'd say this strongly supports Uberdude's point that A is almost always the move. However if b can be considered joseki is more a matter of personal definition. I'm guessing that some would call it a special purpose move and some would call it a rare joseki move.

here are the board positions where katago chooses b.
Click Here To Show Diagram Code
[go]$$ Unusual influence position for W.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . O . O . . |
$$ | . . . . . . . . . . . O . X X O O O X |
$$ | . . O O . . . . . . O . X . X X O X . |
$$ | . . . X X . . . . , . . . . . X O X . |
$$ | . O . . . . . . . . . O . . O O X X . |
$$ | . . . . . . . . . . . . . . . . O X . |
$$ | . . . B . . . . . . . . . . . . O X . |
$$ | . . . . . . . . . . . . . . . . O X . |
$$ | . . . . . . . . . . . . . . . . O . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , X . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

Click Here To Show Diagram Code
[go]$$ Both players may look to build boxes towards the centre.
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . O . . . . . . . . X . . . . |
$$ | . . . O . . . . . , . . . . . , X . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . X X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . X . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . O . . . |
$$ | . . O , . . . . . , . . W . . O X . . |
$$ | . . . . O . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . X . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]


also seems worth noting that in both of these specific board positions katago agrees with the human about the earlier moves in that quadrant including the 4-4 move ontop of the 3-3 stone and then the direction of the push.

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 Post subject: Re: Understanding a san-san joseki
Post #14 Posted: Tue Dec 07, 2021 4:38 pm 
Oza

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Click Here To Show Diagram Code
[go]$$W
$$ -------------------
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . O O a . . . . .
$$ | . . . X X . . . . .
$$ | . O . . . . . . . .
$$ | . . . . . . . . . .
$$ | . . . b . . . . . .
$$ | . . . . . . . . . .
$$ | . . . . . . . . . .[/go]


I haven't checked all joseki dictionaries, but I don't think AI is teaching the human pros anything here. Kitani says 'a' is the joseki move. 'b' is not labelled a joseki but is commonly used when you want to emphasise Black's low position. He also says 'b' is not a move you would necessarily want to pay at once.

He seems sniffy about the various kakaris (they strengthen Black too easily) but if one is needed he seems to prefer to the two two-space third-line kakaris (i.e. high and low), and of course in that case White is at least controlling the direction of play.

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