Yose question

Bill Spight · **#21**

John Fairbairn wrote:

Bill

If I may be a terrier chasing the quarry first flushed out by Ed...

1. You say the problems with double sente has been known for at least 40 years. I infer from your quotation of Kano's 1974 book that this is the source for "40 years".

Yes. I also expect that Davies was aware of the divide by zero problem before 1974. Smart man.

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You add that his text is confusing.

1a. Two points to that. First, I didn't find his text confusing. He is not teaching anything in that section. He is just defining terms, and he gives an example of a "pure" double sente before the one you cite.

Here is the diagram.

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

By absolute counting a play has a value of 20, with follow-ups worth 17 points for Black and 19 points for White. In theory this is a gote, but in practice it will almost certainly be a double sente, because plays worth 17 points or more are rare in go. The opening move gains only about 14 points, for instance.

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The one you cite he presents to make a clear point: "However, although this is likewise called double sente you need to recognise that here a difference may arise in the right [to play it] depending on the position." He then goes on to explain that if Black has a higher priority move elsewhere, he may take that instead of fully answering in the cited position in gote. Assuming that's the portion you found confusing (and there's little else in the source), I'm puzzled because it seems straightforward to me - it's double sente but in practice White is more likely to get it.

I consider it confusing because it is Black sente, but in practice sometimes White can play with sente, too. Kano gets it backwards.

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Also, it may be worth adding that he does not use the phrase unconditional double sente, though I accept that some such sort of qualification can be inferred.

Back in the 1980s I submitted an article to Go World entitled "There is No Such Thing as Double Sente". I had written it some years earlier, but had recently reestablished contact with Bozulich, so I thought I would give it a try. As of 2000 I had come to see that there is a well defined sense of double sente which depends upon the whole board. IOW, it is conditional. That's why I used the term, unconditional, for the traditional usage of double sente.

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1b. However, I may have missed something, and in support of that, the 1985 edition of Kano's dictionary reworks this section entirely, which perhaps indicates that he saw a problem with his first effort. But the problem may not have been in the position cited. Rather it may be because he appears to have taken a completely different approach to boundary play counting in general, and to my inexpert eye he has moved a long way towards O Meien, even using some of the same "rights" vocabulary. In the 1985 book Kano also goes well beyond his first effort in explaining why we need to be cautious about regarding the components of a double sente position as sente, and in support of that he cites a completely different kind of position where life & death are not involved, but aji is, and he adds a section on ajikeshi. However, he also clearly explains that this is really a middle game issue and not a boundary play issue and adds that "In a sense it can be called a pre-boundary play problem, but if we do classify it as a boundary play, it is one to which we will give the highest order of priority." And, also worth adding, he tends to be scrupulous in saying "double sente boundary play" and not just "double sente." Again, I see no confusion in this. So my question boils down to this: why should I care about things like dividing by zero, why should I believe there is any practical value in accepting there may (or may not) be some pedantic flaw in the concept of "double sente", especially when I do not add "unconditional" to the term and I do recognise the difference between middle game and endgame?

IMO, the value is clarity of thought. O Meien does not need the theoretical concept of double sente. Neither does CGT. (I think that the proverb about double sente is valuable, but needs interpretation. In practice, such positions do arise.) I remember, as a 4 kyu, seeing a "double sente", a second line kosumi, go unanswered in a pro game. Tilt! Had I been playing a teaching game with, say, a 7 kyu who ignored that play, I would have said, "No, that's a double sente. You have to answer." Wrong! If pros ever believed that that play was double sente, they overcame that notion. Better not to learn it in the first place.

I do not think that Kano was the only one who was reevaluating the idea of double sente at that time. That it was problematical was already in the air.

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2. As I just mentioned, Kano appears to have moved towards the O Meien position even before O did. But O took it further and presents a completely different system - Absolute Counting. I'm in no position to judge on the relative merits of any system, but I think I can judge when one system is starkly different from another. On that basis, I fail to see how lack of mention of double sente in O's system is relevant. He doesn't see the need to use it, so he doesn't seem to regard it as relevant either. He doesn't even bother dismissing it. It's like a paper spoon. He just doesn't need it in his system, so why mention it. He's not saying it's not relevant to other systems of boundary play counting. Instead, he is saying his whole system is better than other systems, but he doesn't appear to have convinced the whole go world yet. Is that a fair summary?

I have touched on this above. O knows what he is doing. He even evaluates reverse sente but not sente, which is a clarification.

I don't know about his influence on others, but by demonstrating that you do not need the concept of double sente for evaluation, I think that others will come around to that way of thinking, sooner or later.

I have the 1995 version (3d printing in 2000) of the Nihon Kiin's Small Yose Dictionary. Unfortunately, it starts out with double sente, and even follows up with a whole board position with a number of "double sente". It shows two lines of play, one with Black playing first and one with White playing first. In each line of play the first player plays all of the double sente with sente. Tilt! Sakata would never have answered each "double sente", nor would Go Seigen, nor would Fujisawa Hideyuki, nor would Cho Chikun, nor would Gu Li, nor would Lee Sedol, nor, I trust, would any Chinese, Korean, or Japanese pro at the time. That is a prime example that shows the value of clear thinking about so-called double sente.

So far, so bad. But! There is a section showing a number of plays and evaluations. Unlike such sections in earlier editions, no double sente are evaluated. Why not? Surely because it was known that there is something wrong with evaluating double sente.

oren · **#22**

During a big board commentary for a major title match, O Meien's absolute counting book was being given away as part of the gift lottery. Takao Shinji was asked if he understood the book and he just said not at all.

I found it amusing.

Bill Spight · **#23**

Here is an example using Kano's practical double sente, which nearly always should be answered, no matter who plays first. But if there are four copies of it on the board, they are miai. Correct play (when there is no ko) is for each player to make a threat in two corners and to answer the opponent's threat in one corner, regardless of who plays first. IOW, to treat the opponent's play as gote. I have included enough variations to illustrate that the plays are not sente, I think.

Cassandra · **#24**

Bill Spight wrote:

Here is an example using Kano's practical double sente, which nearly always should be answered, no matter who plays first. But if there are four copies of it on the board, they are miai.

This is either a contradiction in terms, or leaving the scope of action.

Considering "Sente" (especially "Double-Sente") in usual books on "Yose" has nothing to do with whole-board considerations, but has to be seen locally only.

For whole-board considerations you will have to consult a book on "Ô-Yose".

It should be very evident that the "Sente"- / "Gote"-relationship (when seen more globally) depends on the surrounding conditions.

oca · **#25**

Bill Spight wrote:

Double sente depends upon the rest of the board. Typically each player's threat must be greater than anything else on the board. One flaw with older yose books is that they present certain positions as inherently double sente. It has been known for well over 40 years that there is something wrong with the idea of unconditional double sente. Still, writers often follow tradition and classify some positions as double sente. One who does not is O Meien, 9 dan, who does not even mention double sente in his recent yose book.

In the begining of the book I mentioned, there is actualy a kind of general advice that explains that sente is not necesserly "absolute".

Bill Spight · **#26**

Cassandra wrote:

Bill Spight wrote:

Here is an example using Kano's practical double sente, which nearly always should be answered, no matter who plays first. But if there are four copies of it on the board, they are miai.

This is either a contradiction in terms, or leaving the scope of action.

Considering "Sente" (especially "Double-Sente") in usual books on "Yose" has nothing to do with whole-board considerations, but has to be seen locally only.

For whole-board considerations you will have to consult a book on "Ô-Yose".

It should be very evident that the "Sente"- / "Gote"-relationship (when seen more globally) depends on the surrounding conditions.

It sounds like you are criticizing what I said, but I am not sure why. The problem with the textbook treatment of double sente (O Meien excluded, OC) is that, even though both sente and gote have both practical, global definitions, and technical, "local" definitions, double sente only has a practical, global definition. Yet they treat it as though it had a technical, local meaning.

As I said to John Fairbairn, Kano got it backwards about his 1974 example. It is not a double sente, but, depending on circumstances, Black might not reply locally to White, rather it is a Black sente, but, depending on circumstances, Black might reply locally to White.

Cassandra · **#27**

Bill Spight wrote:

Cassandra wrote:

Bill Spight wrote:

Here is an example using Kano's practical double sente, which nearly always should be answered, no matter who plays first. But if there are four copies of it on the board, they are miai.

This is either a contradiction in terms, or leaving the scope of action.

Considering "Sente" (especially "Double-Sente") in usual books on "Yose" has nothing to do with whole-board considerations, but has to be seen locally only.

For whole-board considerations you will have to consult a book on "Ô-Yose".

It should be very evident that the "Sente"- / "Gote"-relationship (when seen more globally) depends on the surrounding conditions.

It sounds like you are criticizing what I said, but I am not sure why. The problem with the textbook treatment of double sente (O Meien excluded, OC) is that, even though both sente and gote have both practical, global definitions, and technical, "local" definitions, double sente only has a practical, global definition. Yet they treat it as though it had a technical, local meaning.

As I said to John Fairbairn, Kano got it backwards about his 1974 example. It is not a double sente, but, depending on circumstances, Black might not reply locally to White, rather it is a Black sente, but, depending on circumstances, Black might reply locally to White.

A large Japanese Go Encyclopedia shows (and explains) "Double-Sente" in the local context only. There are one surrounded group each, which will both die after ignoring the "Sente" move of their opponent (this is similar to your example).

I suppose that it will be evident that "Sente" characterises a move (the one and only) that is the largest one on the board (otherwise there is no need to answer "locally", just because answering would be a mistake).
This means that ignoring a move of "Sente" kind must always lose more than answering it. This evaluation might become extremely difficult, as a matter of course, if executed over the entire board. ;-)

If a local position is shown, we have to assume that -- for both players -- there are no larger spots on the board to play their first move. In this case, enlarging (or reducing) the number of a group's stones (in the problem's setup) will not affect the discussion on the endgame.

This is similar to the fundamental assumption in Tsume-Go that -- in principle -- all outside groups are alive.

oca · **#28**

While we are talking about Yose, here is a link to a new "free" video about endgame on badukMouies
https://badukmovies.com/episodes/endgam ... ?play=true

snorri · **#29**

Uberdude wrote:

What is this theory of O Meien? Is there anything about it in English? Maybe that Zone Press Park book?

Zone Press Park doesn't touch on it in any way that I noticed.

mitsun · **#30**

I must be missing something in this discussion. How can the position below be called anything but "double sente"? And how can there be any ambiguity in assigning a value of 4 points to a play here?

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

Of course it is possible to construct a global position where playing or replying here is incorrect, but yose theory and terminology are all about evaluating local positions.

Tesuji dictionaries do not seem to find it necessary to include the disclaimer "this move is a mistake if there is a larger play elsewhere on the board".

If we look at the similar position below, it seems everyone would be comfortable calling a play here sente for W, or at least reverse sente for B. But again, there are certainly global positions where these plays would be incorrect.

Click Here To Show Diagram Code: [go]$$B "Reverse" sente for B $$ -------------------- $$ | . . . . . . . O X . $$ | . . . X O O . O X . $$ | . . . X O . O O X . $$ | . . . X X O . O X , $$ | X X X X O O O O X . $$ | O O O O X X X X X . $$ | . . . O O O . . . . $$ | . . . . . . . . . .[/go]

What is the distinction which makes "reverse sente" reasonable and "double sente" problematic? Is it just the ability to assign a value in points per move (rather than absolute points)?

Uberdude · **#31**

If I was faced with such a position in an OGS game where I was doing detailed yose analysis and such a position was not obviously double sente, I would classify that position as:
black 4 points gote with 32 points follow-up,
white 4 points gote with 30 points follow-up.

Then I can easily look at the tree for answer and tenuki, and decide the best time to play it.

Bill Spight · **#32**

Click Here To Show Diagram Code: [go]$$Bc A - +5 (for Black) $$ -------------------- $$ | . . . . . . . O X . $$ | . . . X O . . O X . $$ | . . . X O . O O X . $$ | . . . X X O . O X , $$ | X X X X O O O O X . $$ | O O O O X X X X X . $$ | . . . O O O . . . . $$ | . . . . . . . . . .[/go]

Click Here To Show Diagram Code: [go]$$Bc B - +25 $$ -------------------- $$ | . . . . B . . O X . $$ | . . . X O . . O X . $$ | . . . X O . O O X . $$ | . . . X X O . O X , $$ | X X X X O O O O X . $$ | O O O O X X X X X . $$ | . . . O O O . . . . $$ | . . . . . . . . . .[/go]

Click Here To Show Diagram Code: [go]$$Bc C - +42 $$ -------------------- $$ | . . . . B . . O X . $$ | . . . X O B . O X . $$ | . . . X O . O O X . $$ | . . . X X O . O X , $$ | X X X X O O O O X . $$ | O O O O X X X X X . $$ | . . . O O O . . . . $$ | . . . . . . . . . .[/go]

Click Here To Show Diagram Code: [go]$$Bc D - +8 $$ -------------------- $$ | . . . B B W . O X . $$ | . . . X O W . O X . $$ | . . . X O . O O X . $$ | . . . X X O . O X , $$ | X X X X O O O O X . $$ | O O O O X X X X X . $$ | . . . O O O . . . . $$ | . . . . . . . . . .[/go]

Click Here To Show Diagram Code: [go]$$Bc E - -15 $$ -------------------- $$ | . . . W . . . O X . $$ | . . . X O . . O X . $$ | . . . X O . O O X . $$ | . . . X X O . O X , $$ | X X X X O O O O X . $$ | O O O O X X X X X . $$ | . . . O O O . . . . $$ | . . . . . . . . . .[/go]

Click Here To Show Diagram Code: [go]$$Bc F - +4 $$ -------------------- $$ | . . B W W . . O X . $$ | . . B X O . . O X . $$ | . . . X O . O O X . $$ | . . . X X O . O X , $$ | X X X X O O O O X . $$ | O O O O X X X X X . $$ | . . . O O O . . . . $$ | . . . . . . . . . .[/go]

Click Here To Show Diagram Code: [go]$$Bc G - -34 $$ -------------------- $$ | . . . W . . . O X . $$ | . . W X O . . O X . $$ | . . . X O . O O X . $$ | . . . X X O . O X , $$ | X X X X O O O O X . $$ | O O O O X X X X X . $$ | . . . O O O . . . . $$ | . . . . . . . . . .[/go]

It is plain that the gain for the next play after Black plays first is 17 points, and that the average value of the position is +25. It is also plain that after White plays first the gain of the next play is 19 points, and that the average value of the position is -15. That means that the first play gains 20 points, more than the next play by either side. Therefore this is a gote.

lightvector · **#33**

To add what might be a further helpful comment in understanding this for people who are confused:

Bill is defining a "gote" move in a particular way - namely one where the urgency of play is decreased after the move.

Except for ko threats and such, this position is exactly equivalent to any position with the following properties:
* If black plays first, black gains 20 points and leaves behind one more move that either player can make that gains 17 points.
* If white plays first, white gains 20 points and leaves behind one more move that either player can make that gains 19 points.

In particular, if there are a wide variety of moves on the board of all different values, including plenty of moves with values between 17 and 20 points, and even moves with values between 19 and 20 points (ex: a position where a player can connect 19 dead-weight stones and make zero territory and where the other player can cut and kill them and also make 1 point of empty territory is worth 19.5 points under this counting method), then once the value of a move drops to 20 points, it will become correct for one player to play the hane, and for the other player not to respond. Not because of some weird tactical reason, not because of some weird thing involving tedomari, not because the endgame was crafted specially somehow, but simply because the position literally does become less valuable to play after a hane, and other moves whose values are in between will be worth more.

Morally, the position is no different than the following:

Click Here To Show Diagram Code: [go]$$Bc $$ --------------- $$ . . . . . . . . $$ . . . . . . . . $$ X X X X O O O O $$ . . . . . . . .[/go]

Click Here To Show Diagram Code: [go]$$Bc $$ --------------- $$ . . . . . . . . $$ . . . 3 1 2 . . $$ X X X X O O O O $$ . . . . . . . .[/go]

Click Here To Show Diagram Code: [go]$$Wc $$ --------------- $$ . . . . . . . . $$ . . 2 1 3 . . . $$ X X X X O O O O $$ . . . . . . . .[/go]

Where:
* If black plays first, black gains 3 points and leaves behind one more move that either player can make that gains 1 point.
* If white plays first, white gains 3 points and leaves behind one more move that either player can make that gains 1 point.

It's just that the numbers involved are larger and it's harder to see at a glance that the urgency does actually drop.

The way I understand Bill's point is that if you define "gote move" as "move that decreases the local temperature" and "sente move" as "move that increases the local temperature", which are sensible purely local definitions, then every position is either gote for both sides, sente for black only, sente for white only, or settled (ex: such as a seki, where a move by either side is "sente" but is a losing move).

In particular, with these local definitions there should be no such thing as a genuine "double-sente" position - every position that people would normally think of as double sente, just like the one discussed here, is actually secretly gote for both sides, sente for black only, or sente for white only. The reason that these positions seem like double sente is due to a more global fact, such as the absence of other moves on the board with values between 17 and 20 points, as well as the implicit meta-knowledge that moves with such values are rare (so that if one side plays, the other side will respond because it's the next biggest move). Without these extra global assumptions, locally they are no different than ordinary gotes and one-sided sentes, it's just that the numbers involved are larger. This is what Bill means when he claims that you can define "sente" and "gote" both locally and globally in different ways, but "double sente" only makes sense defined globally.

mitsun · **#34**

Bill Spight wrote:

It is plain that the gain for the next play after Black plays first is 17 points, and that the average value of the position is +25. It is also plain that after White plays first the gain of the next play is 19 points, and that the average value of the position is -15. That means that the first play gains 20 points, more than the next play by either side. Therefore this is a gote.

Those values are based on calculating the "average" value of the position, under the assumption that it is equally probable for either player to get the next move. Would it not make more sense to calculate the "likely" value of the position, using a better estimate of the probability for each branch of the decision tree? Classifying this position as "sente" for B means I assign a probability of 1 to the branch where W defends (because I consider it highly likely that on the rest of the board there will be nothing larger for W to play).

Both of these evaluations of the local position are uncertain approximations, but if we cannot solve the full-board problem, we rely on them to guide our play. In a real game, which weighting of the decision tree is more likely to be represent optimum play?

Bill Spight · **#35**

Calling a gote that gains 20 points with a reply that gains 17 points for one player and one that gains 19 points for the other a double sente does little harm. In practice such moves appear on the go board and disappear in a few moves, with sente. The problem comes with plays that are not played right away because they are too small.

Click Here To Show Diagram Code: [go]$$Bc Double sente -- Not! $$ -------------------- $$ | . . . . . . . O X . $$ | . . . X O . . O X . $$ | X X . X O . O O X . $$ | . . . X X O . O X , $$ | X X X X O O O O X . $$ | O O O O X X X X X . $$ | . . . O O O . . . . $$ | . . . . . . . . . .[/go]

This is not a double sente. Nor is the double kosumi on the second line, nor are any number of plays identified as such. Thinking of them as double sente leads to confusion, at best.

Look at :w62:

, for instance. How many amateurs would answer such a play because they have been taught that it was double sente?

Uberdude · **#36**

Bill Spight wrote:

How many amateurs would answer such a play because they have been taught that it was double sente?

Not me. It's middle game not endgame. It doesn't make territory as 3-3 still has a problem. White's purpose was to allow q10 peep to be answered at q9 and I'm not letting you do that in sente. I do perhaps have more fighting spirit than average, sometimes to my own detriment, but are there really many dan players who would answer that?

John Fairbairn · **#37**

Quote:

How many amateurs would answer such a play because they have been taught that it was double sente?

But where are amateurs being taught this is double sente? Surely only in a localised problem where there is no global override.

Agreed that you can see many amateurs answer, but I suspect the reason is not because of double sente. It's more likely a problem of a bigger magnitude, such as being unable to find a better move. If they could see one (e.g. killing a big group at one stroke) they'd make it, double sente or no.

My experience is that even DDK learn for themselves for principle that an opponent's move is only sente if you answer it.

What they are crying out for is advice on finding good moves. In hat connection I was interested to read last night, as I continue my investigations into Soltis's book on studying chess, his observation that even weak players find it easy to identify many moves as bad. However, they find it very hard to identify good moves. The explanation seems to be that you just need one reason to identify a move as bad and then you can prune it off at once. But for good moves there are usually several competing reasons to identify them as good and you have to juggle them all around and prioritise them in some way. Not easy. Anyway, I think this adequately explains the double sente problem without any need for deriving endgame theorems. Such moves get a high priority in the confused mind simply because you can see you get at least something out of them.

Bill Spight · **#38**

Uberdude wrote:

Bill Spight wrote:

How many amateurs would answer such a play because they have been taught that it was double sente?

Not me. It's middle game not endgame.

Unless there is some special tactical aspect to the local situation, it is even less likely to be sente in the endgame. The whole point of teaching that the double kosumi on the second line is double sente is to encourage amateurs to follow the proverb and make the play early (i. e., not to wait for the endgame) because it is sente. And not only sente, but double sente, because if you don't play it (with sente) early, your opponent will.

Edit: Is it bigger than it looks? Yes. And that is what should be taught.

Bill Spight · **#39**

John Fairbairn wrote:

Quote:

How many amateurs would answer such a play because they have been taught that it was double sente?

But where are amateurs being taught this is double sente? Surely only in a localised problem where there is no global override.

But then it is even worse. Sorry to pick on Kano, but he is representative. From p. 31 of the 1974 edition of his Yose Dictionary. Edit: BTW, it is obvious from the diagrams that Kano is following the usual convention and treating the Black and White stones as unconditionally alive.

Click Here To Show Diagram Code: [go]$$B Double sente -- Not! $$ ----------------------- $$ | . . . . . . . . . O . $$ | . . . . . a . . . O . $$ | X X X X X . O O O O . $$ | . . . , . . . . . , .[/go]

"a" is indeed the right play for each player. And it is a middling endgame gote. However, Kano says that it is double sente and gives only play diagrams where the opponent answers. He goes on to say that because each side makes a profit with sente, a double sente is the largest kind of boundary play.

See http://senseis.xmp.net/DoubleSenteIsRelative for a discussion of this position.

Quote:

My experience is that even DDK learn for themselves for principle that an opponent's move is only sente if you answer it.

That is one meaning of sente. As they advance, they need to learn more about sente.

Quote:

What they are crying out for is advice on finding good moves.

Yes. And they should be taught that the double kosumi on the second line is bigger than it looks.

They should not be confused with talk about double sente.

John Fairbairn · **#40**

Bill

Thanks for taking the time to go over what you must have had to repeat many times before, but I confess it's entirely over my head. But is that entirely due to me? I have to admit that I think you are giving Kano too much of a bashing. He does say the position you quote is double sente, but nowhere can I see any statement that tells me I must rush to play double sentes willy nilly. He does cite the proverb ryosente yuzurubekarazu, I know, but that and the position cited are firmly embedded in a section entitled "two-point moves" (as opposed to other sections on one-point moves, three-point moves, five point moves and so on). Japanese writers, as you know, are used to expecting readers to think for themselves (which may be a nuisance: I know I always prefer to get an American "For Dummies" style book), and in this case it doesn't seem too onerous even for me to recognise that his double sente applies only in that context.

Similarly, the excellent Mokusu Shojiten makes it plain that even in a position described as a double sente it is often the case that one side cannot necessarily expect the other to answer, adding that such plays are typically decided as part of the middle game negotiations.

I really do think the mutual damage kind of kosumi is in a different category altogether, and I personally find the attempt to drag it into the same box as Kano's kind of move just to have a pop at Kano (and then kick it out again!) is what causes confusion, at least for me.

Maybe the history of the term "double sente" in English has compromised it for the western audience, but it seems well enough presented in Japanese, to me, and there have been enough mathematically minded and well qualified Japanese amateurs contributing to Kido and the like to make me wonder why they don't see it as a problem. Maybe the difference is that the Japanese use the term as a description; westerners want to use it as a definition (or something like that).

I find the western agonising over the meaning of 'forcing moves' and sente misplaced for similar reasons.

Am I speaking for other confused souls, or is it just me?

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