Sometimes you can see this joseki in pro games.

The first variation is quite simple. Black takes sente corner territory and white gets thick.

The second variation is chosen by white to avoid giving black sente corner. Black has some choices later, but usually he secures the corner during the middlegame and leaves the aji to move the invasion stone.

I'd like to hear some thoughts about this position. Do you think it's playable for both? Better for one side? How would you evaluate this position?

Are there some known methods for such evaluation?

Click Here To Show Diagram Code

[go]$$
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[go]$$c var 1
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[go]$$c var 2
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$$ ---------------------------------------[/go]

Yes: my joseki evaluation method.



Stone difference = 6 - 6 = 0. // No adjustment is needed.
Territory count = 17 - 6 = 11.
Influence stone difference = 1 - 6 = -5.
Ratio = |11 / (-5)| = 2.2.

The ratio is within the valid range [1.5..3.5] for ordinary josekis without special advantages or disadvantages for a player so the result is equivalent to joseki.

Is that really enough to say that the position is even? What is your justification for 'the valid range' of an even joseki? Why do you not take into consideration the shape of influence stones but only their count?

Robert: This seems like a good opportunity to ask you something I've meant to ask before. (Readers not familiar with Robert's theory may need to know that the terms above belong to Volume 3 of his joseki trilogy. I am not specially familiar with the workings of the theory but at least I have bought the books ).

Influence stone difference. As I understand it, here you are counting Black's leftmost stone as 1 and all White's 6 stones as -6. But if we imagine that we remove Black 1 and White 6 and put White 2 on Black's intersection, we get an influence stone difference of 4 (i.e. counting White 4 as an influence stone, meaning it has significant impact on the outside). The stone count remains the same. On the face of it, this should be in Black's favour (i.e. White has less influence), yet I'd feel rather inclined to argue that it is actually better for White because he doesn't now have to worry about the aji of the Black stone 1. I think I am essentially just re-stating Minjae's point. Your view?

On a slightly different tack, though, it seems questionable also to include White 4 as an influence stone. In your Vol. 3 page 46 Example 1 there is a reasonably similar position where you do not count the second line blocking stone as an influence stone, even though it is arguably stronger than White 4 here.

MinjaeKim, my justification is having studied a representative selection of 400 josekis (that do not necessarily become middle game fights immediately) of which 399 comply to my theory and 1 does not comply because its judgement depends on a possible middle game ko, for which ko evaluation theory is required.

My method presumes that both players have strived to create good shapes. In this example, you can verify the existence of good shapes by the created thick shapes. WRT to numbers of influence stones, my method works with approximate counts, which tolerate counting 1 per stone despite different shapes. I have worked out the theory to distinguish significant influence stones to be counted from not counted stones.

John, the term 'territory count' is common in Western theory. For my theory, it relies on the players' 'current territory', whose name I invented and method I refined. 'Stone difference' is a concept many players must be aware of somehow but I have defined it explicitly and given it a name. 'Influence stone difference' is my invention.

Your imagined removal and placement of stones can be techniques of tewari, but by method is independent of tewari. If we execute your suggested tewari, the extension R10 becomes an overconcentrated stone. Therefore, I dislike your suggestion.

White 4 on the board or not on the board alters the degree of the white thickness greatly. Therefore, White 4 contributes to the great outside influence as much as the other white stones. The source you mention has not worked out the principles of distinguishing significant influence stones from other stones in the counts; I have worked out the principles so far privately and you can get access to them later.

I agree about the overconcentration, but that still looks better than having bad aji - or, at least, the aji loss and the overconcentration loss cancel each other out. Either way, I'd be a little surprised to see this called a (local) joseki.



This seems to tell me what I already suspected - that Vol. 3 is not sufficient for me to work out influence stones reliably for myself. I therefore (pro tem) simply have to accept only your evaluations in the dictionary without being able to work out theory-based ones for myself. Is that correct?

Incidentally, Minjae refers to this as a joseki, but the GoGoD database has only 12 examples (between 2005 and 2012) of the Black invasion and in only 4 cases does the above position result. I wouldn't have thought that was quite enough to declare it a joseki yet.

Uh, that's why I say "equivalent to joseki":)

As a first approximation, count the stones that contribute to outside influence significantly. So far, it is up to you to decide what is significant. (And yes, existing examples with declared numbers help, too.)

You studied non-joseki too, right?

_________________
Occupy Babel!

I think that this is the real answer.

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.

hyperpape, yes.

You cannot just talk about good or bad corner patterns without looking at the global positions. Here is my analysis based on professional games.

Game 1: http://www.go4go.net/go/games/sgfview/6215/49

Click Here To Show Diagram Code

[go]$$Bc
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . X O # . . . . . . O X 1 . . . . |
$$ | . O X X O # . . . O . X . O X . . . . |
$$ | . . O O X # . . . , . O . O . X . . . |
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$$ | . . . X . . . . . , . . . O . O X . . |
$$ | . . . . . X . . X . . . . . O X X X . |
$$ | . . . . . . . . . . . . . . . O X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

Black's decision to take the corner territory is clearly a sensible one. Because of the marked wall, white's thickness is unlikely to be effective. White apparently saw the same and he did not play M18 immediately, leaving it as a yose move to play later, which is also sensible. In this case, white's other groups are super-solid. So if black were to get M18 first, white would only need to deal with one weak group which isn't difficulty at all.

Game 2: http://www.go4go.net/go/games/sgfview/20881/38

Click Here To Show Diagram Code

[go]$$Wc
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$$ | . 1 O . . . . . . . . . . . . . . . . |
$$ | . O X X . . . . . . . . . . . . . . . |
$$ | . X . . . . . . . . . . . . . . O . . |
$$ | . a O X . . . . . . . . . . . . . . . |
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$$ | . . X , . . . . . , . . . . . , O . . |
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$$ | . . . . . . . . . . . . . . . X X . . |
$$ | . . . . . . . . . . . . O . . . . . . |
$$ | . . @ . . . . . . . X . . . . . . X . |
$$ | . . . . . . . . . . . O . . . O O X . |
$$ | . . . O . . . . . X . . . . O , X . . |
$$ | . . 2 . . X . . . . X O O . O X . . . |
$$ | . . . b . . . . . . . X . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

White's marked stone helps to reduce the influence of black's thickness. If black plays 'a', white would play 'b', making the corner very strong and black's thickness useless. That's why black needed to play urgently in the game.

Game 3: http://www.go4go.net/go/games/sgfview/22189/26

Click Here To Show Diagram Code

[go]$$Wc
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$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . X X . |
$$ | . . . . . . . . . . . . . . . O O X . |
$$ | . . . . . . . . . . . . . . . . . O . |
$$ | . . . . . . . . . . . . . . . O X a . |
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$$ | . . . , . . . . . , . . . . . , O . . |
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$$ | . . . . . . . . . . . . . . . . b . . |
$$ | . . X . . . . . . . . . . . . . 1 . . |
$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . X O . O . . . , . . . . . , X . . |
$$ | . . X O . X . O . . . . . . X . . . . |
$$ | . . X O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

For the same reason as covered in the previous game, white attempted to play more efficiently with . If he plays 'a', black would play a safe two-space extension at 'b', making white's thickness useless.

Game 4: http://www.go4go.net/go/games/sgfview/24872/46

Click Here To Show Diagram Code

[go]$$Wc
$$ +---------------------------------------+
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . 1 O X X . . . . |
$$ | . X O X X . . . . O . X . O X . . . . |
$$ | . . . O . . # . . , . O . O . X . . . |
$$ | . . O . . . . . . . . . . . . . . . . |
$$ | . . X O . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
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$$ | . . O . . . . . . . . . . . . . . . . |
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$$ | . . . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . O O . . . . . . . . . . . . . . . . |
$$ | . X X O . X . . . . . . . . . . X . . |
$$ | . X O O . . . . . , . . . . . , . . . |
$$ | . X X O . O . . . . O . . O . X . . . |
$$ | . X . X O . . . . . . . . . . . . . . |
$$ | . . X . . . . . . . . . . . . . . . . |
$$ +---------------------------------------+[/go]

Black's marked stone helps to reduce white's influence. So it's sensible for black to take the upper-right corner. So did white make a bad decision earlier? Not necessarily. Given that black spent one extra move earlier at B17, white defended happily at - if this place is taken by black white's whole group would be under attack.

As can be seen, we always need to have the global position in mind while deciding to play or not play a joseki or indeed any pattern. I am unimpressed by efforts to quantify the effectiveness of any pattern, unless the underlying mathematical model also takes the global position into account, which of course is really hard.

Global considerations are necessary for strategic planning incl. deciding whether a particular corner variation is appropriate. This does not prevent local joseki evaluation.

Without the shape completing move, the outside group is a group of influence stones but is not thickness, as you have called it.

Do you have numbers for that too? How many non-joseki did you study, how many of them were not considered joseki according to your theory and how many were?

A high recognition rate like 99.75% is meaningless unless you also have a low false positive rate.

The non-joseki variations fit equally well in the theory under the type "favourable for a particular player". What you need to understand is that there also are types permitting excess values if such an advantage is compensated by a different (strategic) advantage for the opponent, such as "enclosing the player's group in the corner".

Yes, but do you have numbers? How many such positions did you study, and how often did they conform to existing (professional) judgement?

I was taught it depends on the stones in the bottom right. In general it's not joseki but can be played depending on surrounding situations.

I do not have numbers for them. Probably I studied more non-joseki variations than joseki variations. I do not recall any (non-fighting, middle game like variation) not fitting my theory. Professional judgements hardly offer a systematic analysis applicable to several (even many) joseki positions. So all I could do was comparing to pro dictionary statements "this is joseki", study GoGod database frequencies etc. Apart from outdated josekis, everything agrees to my theory on the rough this-is-joseki-statement-level, where information is available.

Hmmm ... an empirical formula, based on one algorithmic number, one semi-algorithmic which charitably speaking wouldn't be too debatable, and one "fudge factor". I wasn't aware that this sort of data-mining had gone on.

I don't object to the three dimensions: from a teaching point of view including the "local tally" pleases me.

I tend to object on logical grounds to any confusion of necessary and sufficient conditions. This sort of formula can hardly be yielding a sufficient condition for joseki. My reasoning: pros would not play a line that clearly lost 1 point. But that would move the number only 0.2 in this example? So the calculated result cannot be robust enough to make those discriminations, if it is near the central value 2.0.

So, mainly a test for the plausibility of joseki-like exchanges, that can filter out the "funny looking kids"? But there is perhaps more, if there are discrete "niches" to be understood here.

The ratio type of josekis is part of the theory. There are a few other types, which are necessary. E.g., the influence stone difference 0 falls into other types also to avoid division by zero.

There are more than three dimensions, but three of them are numerical and involved in the calculations. Also therefore the numerical part is not sufficient.

Since the evaluation is an approximation, very similar local results cannot be distinguished in this manner. If everything else is equal (same stone difference, same outside shapes, similar inside aji) but one sequence is, say, 2 points of territory better than the other, it can happen that the method does not detect this. However, such is scarce in josekis or joseki-like sequences. Almost always, the outdated variation creates a different shape on the outside than the modern variation. Nevertheless, it can happen that the outdated variation is better in some global positional environments. Being 2 points better locally does not say "always better in the global context". My method is more tolerant, and this is a good thing because knowledge of a 2 points better variation must not inhibit strategic flexibility. What my method does not do is to find the 2 points better variation automatically. It is not a variations generator.

Excellent point!

_________________
The Adkins Principle:
At some point, doesn't thinking have to go on?
— Winona Adkins

Visualize whirled peas.

Everything with love. Stay safe.