Hi Dave, This is a well-known problem with overly simplified rulesets. TT-advocates don't care about the rare anomalies.
Did you notice that under positional superko you cannot take back the ko after *any* number of consecutive passes? This is yet another reason why in some cases filling an eye or playing in sure territory may be the best move... In your engine you don't want to use 3 passes unless absolutely necessary because of horizon effects. In my experience it is best to use 3 passes only if there is exactly one basic ko, and in all other cases use 2 passes to end the game. Erik On Fri, Oct 24, 2008 at 10:00 AM, <[EMAIL PROTECTED]> wrote: > Is it correct to end games by 2 consecutive passes? > > When I learned go 20 years ago I was taught that 3 consecutive passes are > required to end a game of go. > In practice 2 passes are sufficient in nearly all cases, but sometimes 2 > passes is not enough. > Suppose we have this position in a 5x5 game with area scoring and 2.5 komi: > > (0 = white, # = black) > > ABCDE > 5 00### > 4 00#+# > 3 +0### > 2 00##+ > 1 0#+## > > Black has just played C4. > > The controller is very simple. It only prohibits simple ko (superko is not > checked) and all stones left on the board when the game ends are considered > alive. > White now at C1. Black has no choice but pass and then white quickly passes > too. What happens now? > > If 2 passes end the game, the controller will award a win to white by the > komi. > If 3 passes are required to end the game, black captures at B1, white has no > choice but pass, then black captures at A3 and will (probably) win the game. > > On could argue that controllers are smarter than the controller in my > example, so 2 passes are usually sufficient in pactice, because the > controller will query the engines for dead stones. > But in my example, wouldn't both engines be justified to declare the white > stones alive because of the 2 pass rule? > > Also, if I am correct, (light) playouts are usually controlled by an > internal "controller" that is very similar to the controller in my example. > Wouldn't they be vulnerable to this type of situation? > > Why not avoid this issue simply by requiring 3 consecutive passes to end the > game? > > Am I missing something here? > > Dave > > > > > > > > > _______________________________________________ > computer-go mailing list > computer-go@computer-go.org > http://www.computer-go.org/mailman/listinfo/computer-go/ > _______________________________________________ computer-go mailing list computer-go@computer-go.org http://www.computer-go.org/mailman/listinfo/computer-go/
