Spight Rules

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I have proposed these two rules which address the questions of endless repetition and stopping play at the end of the game.

  • A board play may not repeat a previous whole board position unless a pass has intervened since its last occurrence.
  • Play stops when the same player passes a second time in the same board position.

With area scoring play ends when play stops. With territory scoring play stops twice. After the first stop there is an encore in which a pass costs one point and each player makes the same number of plays (considering a pass a play). Also, passes before the encore do not count for stopping play in the encore. After the second stop play ends if each player has made the same number of plays. If not, the second player in the encore makes an obligatory pass and play ends.

/Discussion

-- Bill Spight


Feedback request

Bill: I am thinking of making a complete set of rules that people might actually play by. I would like to get some feedback on different rules for stopping play. While I think that my original idea, above, is adequate, there are other possibilities that people might like better. Here are the current alternatives I have in mind. Please comment below. Thanks. :-)

1) Play stops when the same player passes a second time in the same position. Play may resume with the passer to play, with ko bans lifted.

Or

2) Play stops when a player plays to a position where his opponent has passed before or passes in that position. Play may resume in turn, with ko bans lifted.

Or

3) Play stops with two consecutive passes. Play may resume in turn, with ko bans lifted, except as provided next. If a player has made the last pass in a particular position, his opponent may never make a board play that returns to that position.

Note for all alternatives: There may still be a ko or superko ban against returning to the current position.


Comments here, please.

The Count: Because rules 1 and 2 don't say "never" and resumptions are possible, can't you have endless cycles? For rule 2, say there is a single stone ko. Black takes, White passes, Black passes. Game ends. Game resumes. White takes, Black passes, White passes. Game ends. Game resumes. At this point, the cycle take-pass-pass-take-pass-pass could go on forever with the game ending and resuming after every move. Have I got this right? Maybe play can resume only once.

Anyway, I think rule 3 is conceptually the easiest, especially if you phrase it, "No player may ever return the board to the position in which the game temporarily stopped."

How about this, though. On their turn, a player can make a board play, pass, or "lift" (lift all ko bans). A player cannot "lift" a second time in the same position; all other rules the same. Similar to rule 1, but conceptually easier? Maybe you would object to adding a new type of move, "lift". The thing is, I think the consecutive-pass end rule is very nice. In my opinion, a pass should imply a player has nothing left to do, and two passes should imply an infinite pass cycle is about to begin, so the game can safely end.

In addition you could apply your rules to no-pass go with prisoner return, because when a player makes the special "lift" move, the rule could be that they give their opponent one of their own stones instead of returning one of their opponents. Otherwise, a player may not have the luxary of passing if they have no prisoners.

By the way, I'm not at all convinced that passes should lift ko bans.

Bill: Many thanks to The Count for your perceptive comments. :-) As for endless cycles, they do need another rule to say when a stop is final. I wanted to allow non-final stops to let the players agree about dead stones without having to play everything out.


{Explanatory discussion under construction.}

Spight rules are based upon the idea of evaluation. First, play should stop in a position that has a definite value (score). Second, the score of such a position may be determined by play with passes that have a value.

Using passes to evaluate positions is based upon the idea that if one player makes a play that gains a certain amount, and then the other player makes a play that gains the same amount, the result is the same as the value of the original position. If we treat a pass like a play and the value of a pass is the same as the value of best play (under these conditions) in a position, the resulting position after a sequence of best plays and passes with the second player passing last will have the same value as the original position.

[Diagram]

Half point

By convention the framing stones are alive. We count the Black territory in the corner as 1/2 point. (OC, at the end of the game it will be worth 0 or 1.) The miai value of a move at a is also 1/2.

Suppose that the value of a pass is 1/2 point, that Black plays at a, and then White passes. Black gets 1 point in the corner but White gets 1/2 point for the pass, so the result is 1/2 point, the same as the original value of the corner.

[Diagram]

Ko

Here the corner is worth 1/3 point, and the miai value of a play is also worth 1/3 point.

Suppose that passes are worth 1/3 point. Then Black may take the ko, White passes, Black fills the ko, and finally White passes. Black gets 1 point for the captured White stone and White gets 2/3 point for the two passes, for a result of 1/3 point, the same as the original value.

Note that this works only if White's first pass lifts the ko ban, just as a board play would. Otherwise Black is not obliged to fill the ko.

All of this, of course, depends upon the value of a pass and the value of a play being the same. If passes are worth zero, and plays are worth zero or less, correct play in this environment of passes will not change the value of the position. The value of the position will remain the same. Thus, we can say that the position has a score.

Of course, it may be possible to calculate a score for some non-terminal positions, but only some positions are such that that calculation would produce the same result, even if play were to continue. Only such positions have a constant value that coincides with the score. They are scorable.

By area scoring, if we treat each stone on the board as alive, we can count one point for each stone on the board and one point for each point of surrounded territory. If some of the stones are dead, the result of that procedure will not be the value of the position. Provision may be made to remove dead stones by agreement, but continuing play should also lead to their removal, to reach a position with a constant score.

In the next example, under some area rules the game may end in a position where the current result is different from the one if play were to continue.

[Diagram]

What result?

This example is a variant of one of Ing's. White to play.

[Diagram]

Diagram 1

B4 = pass.

By AGA rules and some others, White can now pass and win the game by two points.



This result has its defenders, but it is anomalous. The game has stopped in the middle of a ko fight. It is a kind of Moonshine seki.

Under Spight rules play continues. Black's pass has lifted his ko ban.

[Diagram]

Diagram 2

[Diagram]

Diagram 3

[Diagram]

Black wins

Usually rules differences produce small score differences. Here the difference is 27 points.


Since Wilton Kee has shown how his rules apply to the 2x2, I am following suit.

[Diagram]

Greedy Black

With area scoring, Black may get greedy and try to win by one point. (This is possible under some rules, I believe.)

[Diagram]

W6 = pass

[Diagram]

B9 = pass

[Diagram]

W2 = pass

Note: If B1 were in the top right corner, White could pass and end the game favorably.

[Diagram]

B5 = pass

Now Black is in a dilemma. No matter where he plays, White can pass and end the game favorably.

So Black loses if he passes at move 15. Instead,

[Diagram]

Black takes

[Diagram]

White takes

[Diagram]

Game ends

W8, B9, W10 = pass.

Since neither player can make headway, they pass, ending the game as seki. (Note that Black loses by 2 under territory scoring.)



This is a copy of the living page "Spight Rules" at Sensei's Library.
(OC) 2007 the Authors, published under the OpenContent License V1.0.
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