moyoaji wrote:Considering the board position, it is likely that every good white move will be sente. White is working to invade and/or reduce. Black is simply trying to defend his moyo. Playing a gote move for white would make the board position very sad indeed as black will get to solidify more.
It is true that you can get extended sente sequences in go. But generally speaking the size of plays declines gradually, which means that good gote are normally available. In this case, the very fact that there was no standout play for White suggests that most plays under consideration carry no great threat. Besides, while Black has a large sphere of influence, it is not a moyo.
Beyond that problem, I don't see why I need to have white play a gote move in order to evaluate a board position.
No, it is not necessary. But if such evaluation were possible we would not be having this discussion.
Are you not supposed to take who has sente into account when evaluating the board?
Sure. We assume that sente are played and responded to.
If you are saying that to evaluate the board you need an even number of stones then apparently a lot of go books get this wrong.
What I am saying is that when you do not have a precise evaluation function, but are relying upon judgement, comparing positions where different players got the last move is difficult, as a rule. Because you do not have an estimate for the difference in moves.
If so, Kato Masao made a mistake in "The Chinese Opening" by comparing these two joseki:
$$c Described as a failure
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$$ | . . . . . . . . . . . . . 7 5 4 6 . . |
$$ | . . . . . . . . . . . X . O . 1 O . . |
$$ | . . . O . . . . . , . . . . . X 2 . . |
$$ | . . . . . . . . . . . . . . . 3 . . . |
$$ | . . . . . . . . . . . . . . . . 8 . . |
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$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$c Described as a failure
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . 7 5 4 6 . . |
$$ | . . . . . . . . . . . X . O . 1 O . . |
$$ | . . . O . . . . . , . . . . . X 2 . . |
$$ | . . . . . . . . . . . . . . . 3 . . . |
$$ | . . . . . . . . . . . . . . . . 8 . . |
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$$ ---------------------------------------[/go]
$$c Described as correct
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$$ | . . . . . . . . . . . . . 4 . . . . . |
$$ | . . . . . . . . . . . X . O . 2 O . . |
$$ | . . . O . . . . . , . . . . 3 X 1 . . |
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$$ ---------------------------------------
- Click Here To Show Diagram Code
[go]$$c Described as correct
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$$ | . . . . . . . . . . . . . 4 . . . . . |
$$ | . . . . . . . . . . . X . O . 2 O . . |
$$ | . . . O . . . . . , . . . . 3 X 1 . . |
$$ | . . . . . . . . . . . . 5 . . . . . . |
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$$ ---------------------------------------[/go]
I am sure that Kato would not have had any trouble adding a Black gote to Diagram 1, and then be able to say, "Even if Black plays here, this is not as good for Black as Diagram 2."
Besides, Kato could have been wrong, you know.
Edit: Let me go into that possibility a little more.
If we are talking about judgement, then Kato's was better than anybody's here. But because of the different parity of the moves, we are also talking about the value of a play. Black has made an extra play in Diagram 2. There is a traditional value for an early play that is demonstrably too low, 10 points. We are reasonably certain that that is too low because it implies a komi of 5 points. People who have studied the statistics of go have known for four decades that a komi of 7 points is better, and maybe komi should be higher than that. But that does not mean that the pros have known that. In fact, Ishida's book about the value of plays is obviously based upon traditional values. Since Japanese komi went up to 6.5, maybe Japanese pros now believe that early moves are worth more. But Kato wrote his book before that, when komi was 5.5, and the value of 10 was consistent with that.
I am not claiming that Kato made a numerical calculation, but suppose that if you made him guess, he would say that Diagram 2 was worth around 15 pts. more for Black than Diagram 1. (I have an evaluation function that says just that. Not that I can claim that the function is correct.
) Then, since 15 is greater than 10, the assumed value of the extra play, Diagram 2 is preferable for Black. But what if the true value of the extra play is 14 or 15 points? Then there is not much to choose between the two diagrams, is there? (BTW, my evaluation function tends to overvalue outside influence, and may well be overvaluing Diagram 2. Then Diagram 1 would be preferable, wouldn't it?
)
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