*assume all other corners are taken by the first 3 moves

I saw this joseki in josekipedia and I'm confused by the comment. It states that the position is even, but I don't see what white has gained from this. It is white's turn now but white still needs a move back in the corner to live right? It has no territory while black has stones on both sides.

Especially consider if black has a stone in the top left side (since white is the one that approached, D16?). I guess white can try to attack the M17 stone... I just have a hard time seeing how this position is not better for black.

Can someone tell me what white would try to do with this group? Thanks.

Obviously, this position is better for Black, because Black has one more stone than White. The question is, is it better for Black than the original 3-4 stone?

IMO, on an empty board it is slightly better for Black than that. In part because of the concentration of White stones, in part because the Black pincer stone is so far away from the White strength.

But, in fact, this is typical of pincer josekis. All we can ask from a joseki is rough equity.

Once upon a time, a few centuries ago, it was popular among top players to start with a 3-4 by Black, an approach by White, and a pincer by Black. Then White played somewhere else. Already they knew that for White to continue in the same corner was normally suboptimal. Sure, they had joseki for when White did continue, but those joseki typically favored Black, so White did not continue. So here is a joseki where White continues and the result favors Black. Nothing new here, folks.

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

Visualize whirled peas.

Everything with love. Stay safe.

White tenukis elsewhere, Black and White exchange for below. How does Black kill White?

Click Here To Show Diagram Code

[go]$$B
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . O 2 |
$$ | . . . . . . . . . . . X . . . O O X . |
$$ | . . . , . . . . . , . . . . O , X 1 . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . X . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . , . . . . . , . . . . . , . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ ---------------------------------------[/go]

PS: I cannot agree with Bill here. White is clearly better here. Black's plays do not work together. This can't be joseki!

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

Hi Dave,

@Ed - No need to strengthen Black by sacrificing 4. Simply 6 is enough since it threatens to capture 3, no?

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

Hi Dave,

The stone difference is 1 (Black has played 1 local excess play).

The territory count is 1 using the concept of current territory and, for only this purpose and counting White's current territory, assuming Black S16 - White N18 etc (not Black S16 - White T18).

The influence stone difference is 2 (3 black and 1 white influence stones).

Adjusting the stone difference 1 becoming the stone difference 0 and accounting 1 extra white influence stone elsewhere, we get the adjusted influence stone difference 1.

With the territory count 1 and the adjusted influence stone difference 1, the local position belongs to the value type "small values", i.e., values that are almost 0. This value type indicates a locally almost equal position, i.e., we can call it a joseki. Global considerations dominate.

Where is the evidence that this is joseki?

The position shown occurs just twice in the GoGoD database and in neither case was a pincer involved. The stone at M17 is played after the rest of the moves, and as a check (tsume), not as a pincer. The check is also played deep into the middle game with many stones close by. In neither case is the position remarked on in the accompanying commentaries in the sources.

M17 as an initial pincer is relatively uncommon in itself (though somewhat fashionable since 2000) but, when it does occur, a White attachment at the 3-3 point is rare (7 cases - which seems to suggest that White doesn't like how that might end up, e.g. as here?).

I think it's worth also thinking about what we mean by the word "even." It's true that (assuming Japanese sources - the most common) gokaku is glossed as "even" in dictionaries, but in go it seems to have its own nuance and could probably be rendered better as "mutually acceptable." This is mainly because the tag is applied so often to cases where one side has an extra stone, as here, but the fact that gokaku is used almost exclusively in go despite the existence of other possible ways of saying even (e.g. gobu) suggests that it is seen as a technical word, i.e. has the restricted meaning I have indicated.

That is a very weird pincer, if played as such. Did crop up in an AlphaGo self-play game with the Kobayashi opening though, and Redmond commented on the unusualness: https://youtu.be/TepPAXrz3-Q?t=4m28s.

Tried this is in some different board configurations with Leela Zero.

White is way better everytime.

But black surly has another way to play. Why should he play like this?

Yeah, I just accepted the idea that it was joseki without checking. Mea culpa!

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

Visualize whirled peas.

Everything with love. Stay safe.

How does this position compare with the single stone on the 3-4 pt.? (Top bots give the advantage to White, given the 7.5 komi.) Thanks.

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

Visualize whirled peas.

Everything with love. Stay safe.

Does it matter that white retains sente after this sequence?

My initial reaction to this position was that it seems like black has allowed white to settle in the corner in exchange for a slightly larger settled position on the right. In exchange, white gets sente and the vulnerable pincer stone. Black either needs to make a gote move to settle that stone or white can come back later and harass it. Given how much sente is supposed to be worth in the fuseki, that seems like adequate compensation for black's slightly larger position on the right.

In The 21st Century Dictionary of Basic Joseki, Shinji describes the following position as equal:

Click Here To Show Diagram Code

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

In this position, black seems even better off than in OP's example because black now has settled positions on the top and the right. Shinji just declares this position equal without explanation, but my interpretation has always been that white retaining sente is the compensation for black's territorial advantage.

The net number of stones matters. In both cases Black has one extra stone. For equity, early in the game Black should have around 14 pts. more than White, including pts. for influence. At the end of the game one extra stone may not be worth any territory at all.

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

Visualize whirled peas.

Everything with love. Stay safe.

I just looked this up as well in the GoGoD database (although my copy may be slightly out of date) and it is rare. However, the issue does not seem to be this particular joseki, but rather the low two-space pincer. There are only 40 games in which this position occurs with white to play. The low one-space pincer version of this with white to play, however, occurs in 2,465 games.

Stone difference = 1.
Influence stone difference = 1.
Territory count = 0.

Adjusted:

Stone difference = 0.
Influence stone difference = 0. (White plays 1 influence stone elsewhere.)
Territory count = 0.

This falls into the value type "equality" and therefore may be considered joseki.

However, this analysis presumes that we may count 3 white influence stones. White must be able to use them, e.g., by attacking the upper black group. If the alleged white influence stones are mostly neutral stones because in particular Black has strong support on the left upper side, White must not play this joseki (unless as an emergency quick settling during the middle game). Also only the central white stone as significant influence stone would be insufficient (except for emergency).

Usually, the strong white shape must have good use including the stone 5.

EDIT: count.

Like Gomoto did, I suggest to try to "settle" such questions by analyzing it with Leela and see how it plays for a while.
It is important to do this for both sides, to get a balanced perspective.
Needless to say, you would need to fill the other corners too (with some common-sense fuseki, and match the overall number of stones for black and white), since unlike humans, Leela doesn't know how to do "local analysis".

As for a pure local analysis, as it was already suggested, I would add an extra move for white (so both sides get an equal number of stones), most likely by capturing the black stone on the 2nd line, before trying to jump to any conclusion.
The result will be that white has a stronger position locally and more territory compared to black, so black's only way to balance is to develop the upper side and/or right sides.

_________________
Sorin - 361points.com

Bill, I'm not sure that I understand your point. I think you are saying that white needs another local move in order to equalize the number of local stones. But by that logic, one would never tenunki in joseki in which one is playing the approach stone.

My understanding of what it meant to have sente in this situation is that white can now consider the relative value of a move locally to the value of a move somewhere else. White retains the option of playing locally as you suggest, but it is the option of tenuki at this point that makes white's position valuable. Take the joseki from the Shinji dictionary. Through , white would suffer a VERY large local loss by tenuki-ing. So, in almost all circumstances, white will be better off playing the prescribed moves through 7. However, after , black has one more local stone, but black now needs two moves to either enclose or kill white. So, if white tenukis and black comes back to this area first, white suffers a loss, but a much more limited loss than if white tenukied through .

For example, consider white's move on this board after having finished the joseki above:

Click Here To Show Diagram Code

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

Would adding another stone in the top right be more valuable for white than a move in the top left at say A or B?

And just to be clear, I realize that one can usually create a board that justifies typically non-optimal play. I took the claim that white has sente in these positions to mean that the local loss from tenuki is small enough that white almost certainly needs to look around and decide whether another local move is bigger than a move somewhere else.

Why not? The question of whether to tenuki is separate. That White retains sente means that White played first locally and Black played last locally. That we started from the single Black stone on the 3-4 is indicated by the phrase retains sente. White had sente and keeps it.

The thing is that equity in a joseki does not mean equality. Rough equality depends upon each player playing the same number of stones locally. Equity does not. Black started off with around 14 pts. in the corner. After 10 more moves, 5 by each side, we expect the value of the corner to remain around 14 pts. (Edit: Correction: Actually, because the size of plays generally decreases as play proceeds, we normally expect White to have gained around ½ pt. or a little less in 10 consecutive plays, starting with White to play.) If Black had taken sente in the joseki, then, with correct play we would expect the local result to be around 0, plus a little bit for Black.

The longer the joseki, the less, on average, we expect each play to gain, until, in the extreme, each play gains nothing. In that case it does not matter whether White retains sente or not. (This is actually an argument in favor of tenuki, BTW. )

Leela and other strong bots are trained to take sente and komi into account, and so each correct move should have little effect on their evaluation.

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

Visualize whirled peas.

Everything with love. Stay safe.