On 10/23/06, Don Dailey <[EMAIL PROTECTED]> wrote:
I don't believe in positional superko. I know that 99.9% of the time it makes little or no difference, but I don't see how it can be correct. 2 identical configuration - each with different color to move are simply NOT the same position.
They are by definition. The other superko rule is called Situational SuperKo for a reason. It uses the word situation to denote the combination of position and turn. As a chess player, you must be used to the phrase "in this position, with white to move..." There also, turn is considered a piece of additional information. Turn is just one piece of information about the past that you can add to position to make you feel it better describes the possible futures. In chess there are many other such pieces of information, such as castling rights and possibility of en-passent captures. You may feel that these are also an inherent part of the position, because they affect the future. But why stop there? The future also depends on when 3-fold repetition occurs, so maybe past occurances should also be included in the notion of position? Clearly, this leads us astray. In Go, the forbidden ko point is another piece of information you could add, being similar to en-passent capture possibilities in that it is only about what happened in the last move. You may well say "2 identical configuration - one with a forbidden ko point and one without, are simply NOT the same position." But the approach of including bits of information about the past is inherently flawed since it cannot be taken to its extreme. We cannot say "it is illegal to repeat an entire history of positions". That's why the simplest approach to superko is to include no information whatsoever, not even turn. I don't understand how you can argue that this is more complicated than considering configuration+turn. If you consider superko to be the rule that you cannot repeat a STATE of the game, then what's the simplest possible choice of state? I'd argue it's whatever entails the minimum amount of information. You can't include less information than the board configuration, obviously. And that by itself is good enough for all practical purposes, as you admit. And that is why I consider PSK the most logical choice. In my paper on the combinatorics of Go, I discovered that PSK also leads to the simplest mathematical characterization of a game of go. The game graph consist of all legal positions (configurations) with edges between them corresponding to non-pass-moves. A game of Go is precisely a simple path through this graph, starting at the empty node. Using SSK would lead to a far less elegant characterization.
Your example may illustrate a problem with superko. It's my belief that superko can create bizarre and anomalous situations like this
The occurance of bizarre situations appears to be a very common phenomenon in Go, whether you have PSK or not. Go is such a rich and subtle game that you cannot expect too many rules to hold without their share of exceptions. For instance, a group with 2 "false" eyes can be unconditionally alive in some cases. We may admire this richness rather than view it as something anomalous that needs fixing. Who is to say that SSK doesn't lead to similarly bizarre situations? My guess is that they exist there as well, just harder to find... regards, -John _______________________________________________ computer-go mailing list computer-go@computer-go.org http://www.computer-go.org/mailman/listinfo/computer-go/
