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 Post subject: Shape question NUMBER 2
Post #1 Posted: Tue Aug 25, 2020 5:35 am 
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Hi all,

Another sequence not that clear to me.
The sequence is of course NOT joseki and even to me doesn't sound good. The problem is understand why. Suppose that after 3-3 invasion the player wants AT ALL COST get the corner and plays joseki until move 13, that joseki was played by Kato Masao against Cho Chikun. Move 14 is NOT joseki and I explored that move by myself. After the almost-forced sequence black is at almost 80% winning, and that sounds about right of course but I cannot fully understand why. Clearly the tortoise shape is radiating influence and that's ok but white has sente and with 18 erase totally the influence and the corner is more or less even... can you make some evaluation to fully understand why black is winning there? thans


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 Post subject: Re: Shape question NUMBER 2
Post #2 Posted: Tue Aug 25, 2020 6:01 am 
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The tortoise shape is not just influence, it's influence + safe group (by comparison, a simple wall makes influence but has no eyes so can be attacked). On the other hand, White made mostly second-line territory on the top, that's not enough of a eompensation.


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 Post subject: Re: Shape question NUMBER 2
Post #3 Posted: Tue Aug 25, 2020 6:05 am 
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After your move 18, both sides have two stones outside the upper left (i.e. equality). But in the upper left Black clearly has more points (including captures) and more influence and better shape - and he has the initiative. QED.


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 Post subject: Re: Shape question NUMBER 2
Post #4 Posted: Tue Aug 25, 2020 6:46 am 
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Yeah, as John noted: after W18, black and white played an equal number of moves in total at the end, and have played exactly 2 moves each elsewhere in big open areas. Just pair those moves off for now, and focus on the upper left alone.

Both player spent an equal number of moves there. The "local tally" of moves invested is even. Who is better? Both black and white are stable for now, and each have some territory - white has a few points on the top, black has a few points from capturing and some of the left points like B15 and A15 are likely to end up as points, although nothing is surrounded. The corner is shared. So maybe white has just a little more points.

But black has fifth-line power on the left, while white only has third-line power on the top. So black clearly got the upper hand in outer influence, by a lot.

--------------------------

Or, to go with your reasoning: You say white 18 completely erases black's influence, making the upper left feel even again. So you're counting white's extra stone in the upper left situation. Sure we can do that, that means that that the local tally (the count of net how many moves each side has invested) is now +1 move of white instead of even.

If a configuration of stones where white has spent +1 move ends up feeling even to you... then that's still good for black! White spend 1 more move, but despite that, only got an even result! Black will presumably have an extra stone elsewhere then, putting black ahead. Where? Well, black has 2 corners, and white has 1. There you have it.

----------------

Generally, you can pick whatever configurations of stones you like to consider "local" to a given situation, but then when you evaluate it, you need to do so relative to the local tally. If you say that white's stone reduces black's influence, you have to dock white for that move, and evaluate the situation knowing the local tally is now +1 more move you're counting for white, or else you need to add another black stone in to your consideration to make it even again (*without* adding another white stone in, that would just make it uneven again).

An example to get the point across:

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


Here, assuming it's still the opening both black and white have spent a little too much time playing the endgame moves in the upper left. But anyways, who is the position overall good for? Well, both black and white have extended out to the side a similar distance. They're both 4-th line high, extending down to the third line. But black owns the corner and white doesn't - black has more points. So it's good for black?

No, Black has spent more moves here than white. The local tally is +1 move for B. So we need to judge the position against that. Or, we could make the position even again.

Suppose in that opening the upper right corner had a white stone. Let's bring that in to the picture, *without* compensating black, because now we're considering an even number of stones by each side. Now who do you like?
Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . . X O O . . O . . . . . . . . . . . |
$$ | . . X X O . . . . , . . . . . O . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


Or alternatively, let's just imagine white played a reasonable extra stone, which would also make the local tally even:

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


Now who do you like? Certainly at least as good for white, right?


Last edited by lightvector on Tue Aug 25, 2020 6:50 am, edited 1 time in total.

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 Post subject: Re: Shape question NUMBER 2
Post #5 Posted: Tue Aug 25, 2020 6:49 am 
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lightvector wrote:
Yeah, as John noted: after W18, black and white played an equal number of moves in total at the end, and have played exactly 2 moves each elsewhere in big open areas. Just pair those moves off for now, and focus on the upper left alone.

Both player spent an equal number of moves there. The "local tally" of moves invested is even. Who is better? Both black and white are stable for now, and each have some territory - white has a few points on the top, black has a few points from capturing and some of the left points like B15 and A15 are likely to end up as points, although nothing is surrounded. The corner is shared. So maybe white has just a little more points.

But black has fifth-line power on the left, while white only has third-line power on the top. So black clearly got the upper hand in outer influence, by a lot.

--------------------------

Or, to go with your reasoning: You say white 18 completely erases black's influence, making the upper left feel even again. So you're counting white's extra stone in the upper left situation. Sure we can do that, that means that that the local tally (the count of net how many moves each side has invested) is now +1 move of white instead of even.

If a configuration of stones where white has spent +1 move ends up feeling even to you... then that's still good for black! White spend 1 more move, but despite that, only got an even result! Black will presumably have an extra stone elsewhere then, putting black ahead. Where? Well, black has 2 corners, and white has 1. There you have it.

----------------

Generally, you can pick whatever configurations of stones you like to consider "local" to a given situation, but then when you evaluate it, you need to do so relative to the local tally. If you say that white's stone reduces black's influence, you have to dock white for that move, and evaluate the situation knowing the local tally is now +1 more move you're counting for white, or else you need to add another black stone in to your consideration to make it even again (*without* adding another white stone in, that would just make it uneven again).

An example to get the point across:

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


Here, assuming it's still the opening both black and white have spent a little too much time playing the endgame moves in the upper left. But anyways, who is the position overall good for? Well, both black and white have extended out to the side a similar distance. They're both 4-th line high, extending down to the third line. But black owns the corner and white doesn't - black has more points. So it's good for black?

No, Black has spent more move here for white. The local tally is +1 move for B. So we need to judge the position against that. Or, we could make the position even again.

Suppose in that opening the upper right corner had a white stone. Let's bring that in to the picture, *without* compensating black, because now we're considering an even number of stones by each side. Now who do you like?
Click Here To Show Diagram Code
[go]$$Wc
$$ ---------------------------------------
$$ | . X . . . . . . . . . . . . . . . . . |
$$ | . X O O . . . . . . . . . . . . . . . |
$$ | . . X O O . . O . . . . . . . . . . . |
$$ | . . X X O . . . . , . . . . . O . . . |
$$ | . . . X . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]


Or alternatively, let's just imagine white played a reasonable extra stone, which would also make the local tally even:

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


Now who do you like? Much closer, right?


quite good point here! Many thanks

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 Post subject: Re: Shape question NUMBER 2
Post #6 Posted: Tue Aug 25, 2020 9:29 am 
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Move 11 is not joseki, whoever may have played that move.

Perhaps it is a good move in a concrete game regarding the other stones on the board, but is not joseki. :-)

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 Post subject: Re: Shape question NUMBER 2
Post #7 Posted: Fri Aug 28, 2020 6:51 am 
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Thank you, more clear now!

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