I know white is dead, but what matters is that the controller does not know.
The only way for the controller to know that white is dead is by requiring
black to capture white before ending the game.
And when 2 passes end the game, black is unable to do that. So the controller
will have to assume that white is alive.
Dave
________________________________
Van: [EMAIL PROTECTED] namens Li Li
Verzonden: vr 24-10-2008 11:23
Aan: computer-go
Onderwerp: Re: [computer-go] RE: Ending games by two passes
Wrong assertion: "all stones left on the board when the game ends are
considered alive."
The result has nothing to do with how many "pass". The white is dead when the
game is finished.
On Fri, Oct 24, 2008 at 4:02 PM, <[EMAIL PROTECTED]> wrote:
ERRATUM:
Sorry, I made a small mistake in my example.
The komi should be 3.5 so white wins by 0.5 if 2 passes end the game.
Dave
________________________________
Van: [EMAIL PROTECTED]
Verzonden: vr 24-10-2008 10:00
Aan: computer-go
Onderwerp: Ending games by two passes
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
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