John Fairbairn wrote:I remain unconvinced by Bill on Kano. For the avoidance of doubt, I am not saying Bill's way of counting boundary plays is in any way flawed (nor am I able to say whether it useful or correct).
Except perhaps with some ko positions, my evaluations of local positions and plays will give the same results as O Meien's, barring arithmetic errors.
But my feeling is that Kano is being criticised for something he never said or intended.
My criticism of Kano is about his presenting this position
$$ Double sente???
$$ --------------------
$$ | . . . . . . . O X .
$$ | . . . X O . . O X .
$$ | X X . X O . O O X .
$$ | . X . X X O . O X ,
$$ | X X X X O O O O X .
$$ | O O O O X X X X X .
$$ | . . . O O O . . . .
$$ | . . . . . . . . . .
- Click Here To Show Diagram Code
[go]$$ Double sente???
$$ --------------------
$$ | . . . . . . . O X .
$$ | . . . X O . . O X .
$$ | X X . X O . O O X .
$$ | . 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]
as a double sente when it is, in fact, a 7 point sente for Black,
and for presenting this position
$$B Two point double sente???
$$ -----------------------
$$ | . . . . . . . . . O .
$$ | . . . . . . . . . O .
$$ | X X X X X . O O O O .
$$ | . . . , . . . . . , .
- Click Here To Show Diagram Code
[go]$$B Two point double sente???
$$ -----------------------
$$ | . . . . . . . . . O .
$$ | . . . . . . . . . O .
$$ | X X X X X . O O O O .
$$ | . . . , . . . . . , .[/go]
as a double sente (assuming the existing stones to be alive and safe) when it is, in fact, a gote that gains around 3 2/3 points. (It may possibly be a White sente if I have made an error with the White follow-up after White plays the kosumi.)
Kano probably had a ghost writer, but he put his stamp on both of these examples.
First and foremost the idea of double sente has been around since at least Shi Dingan referred to it in the Qing dynasty, and it is alive and kicking today in each of the oriental go-playing countries. Kano sticks to his guns in the 1985 edition of his book, and although it's a different example he still uses a large-scale one where the value of the respective sente moves is very different.
It sounds like, as with the gote with the huge replies that gain 19 points and 17 points, it would be very likely that either player could make the play with sente. IMO, that is not worth quibbling about.
The huge Chinese "Practical Comprehensive Manual of Go" of 1997 gives an example with a totally different position but likewise a huge discrepancy in the value of the two sentes. One allows killing of a group if unanswered, the other just allows a non-fatal incursion, i.e. the same idea as in Kano's big 1974 example. Yang Jinhua and Wang Qun also give examples in Chinese, large and small scale, in all cases with different values for each side's plays.
The Taiwanese author Li Song gives examples, too, and also has a good introduction on the history of boundary plays going back to Guo Bailing, i.e. early 17th century.
It sounds like these are also plays where the follow-ups gain more than 15 points. If so, not worth quibbling about.
I'll skip Korean examples, as I think the picture is clear enough: we have had in place a method of talking about boundary plays for centuries. It beggars belief that if this was flawed, someone - even if he had to be a genius like Go Seigen - would not have mentioned it.
It was my study of pro games that first made me question the idea of double sente, because the pros so often left what the textbooks call double sente unplayed or unanswered. The idea of double sente, understood correctly, is not a problem. The problem comes with identifying certain local positions and plays as double sente. Why do the books persist in doing so? Especially as the pros do not play that way? I can only guess. (One reason is that the pros do not follow the textbooks. But then, they are not expected to.
) O Meien's book has broken that mold, fortunately.
So has Bill defied the odds? Maybe, and the novelty of CGT gives some grounds for believing in a platform for new insights. But as with conspiracy theories, I always think Occam's Razor is a better tool.
Oh, I identified the 7 point sente and the 20 point gote in 1975, some 19 years before I heard of combinatorial game theory.
All it takes is the traditional go evaluation.
I did not bother calculating the other example, as it was obviously not a double sente.
I believe the Oriental usage of double sente is nothing more than a description, that works in the same rough-and ready way that I say my wife's dress is red but accept she may call it burgundy, cherry, salmon, fuchsia, etc. (and in the way of the world I have accept I'm wrong while knowing I'm right enough). In contrast, while Bill will have to speak for himself as to exactly what he means by double sente, what comes over to me is that he sees it as a cog in a mechanism, and if that cog isn't exactly machined the whole mechanism will grind to a halt. Great if he can do it, but it's hardly fair to Kano and the others to blame them for non-working cogs.
John, ask yourself this. If Bill is wrong, why doesn't O Meien include double sente in his book, like every other writer on yose? Double sente being such a useful cog and all.
He does not need to, does he? As you point out, practical, global double sente arise in nearly every game, often more than once; they are played and answered, and nobody blinks an eye. They are not the problem. It is the textbooks that are the problem.
Imagine the situation in the aforementioned 20-point + 7-point double sente at which Bill took umbrage where one side has an area large enough not to have its life affected, but where that position arises only because that side has just made a move to create that area. Obviously he has gote. Just as obviously the other side will grab the sente. As he plays it he will perhaps think of it only as sente play, but if he was given that position cold and told he had sente, and he wants to know where to play, it is useful to be able, descriptively, to give general advice along the lines of "give priority to double sentes".
The 7 point sente position is so far from a practical double sente it's not funny. If you presented it to O Meien and asked him if it was a 7 point sente for Black, I am reasonably certain that he would agree, barring an error on my part. He would not say, Oh no, it is really a double sente. Why should it be given priority over other sente where the reverse sente gains around 7 points?
And if you presented the gote that gains 20 points, I doubt if he would disagree. He might well say, why bother with calculations, when it will almost always be double sente?
And if you presented the "two point double sente" position and asked if it was double sente, I hope that he would just laugh. Or he might just look at you funny, like Jujo did to me when we were kibitzing a game and I pointed out that one of the players had not responded to a "double sente".
- 
(not shown), gains zero points. But that just means that each move in the exchange gains the same number of points.