Stone scoring and AGA rules
Posted: Sun Apr 30, 2023 10:26 pm
This is probably not a new idea (and may be incorrect, of course). It concerns a (hopefully) faster and more convenient method of calculating the difference of Black's and White's scores in a game that uses stone scoring.
Stone scoring has an appealing codition for deciding the winner: Play until no more stones can be played on the board. Then the player with more stones on the board wins (adjusting for komi).
However, playing out the game to this point can be tedious for some players, and counting all the stones can take a while. One can avoid some of this by agreeing to end play earlier, and then use area scoring with group tax. But this counting also may take a while. The question is, is there a faster procedure to determine the final score?
Now, in the case of pure area scoring, i.e., with no group tax, the problem was, in my opinion, solved by the designers of the AGA rules. Probably most people are familiar with these rules already, so I will just mention that they use pass stones, and require White to make the final pass. Prisoners are then placed in their respective territories, and territory counting is used. Then it can be shown that the difference between Black and White's area scores is exactly equal to the difference in their territory counts. For those (like me) who find territory counting more convenient, this is very nice idea.
For stone scoring, we could follow a similar procedure: First, use AGA rules to find the difference in area scores. We could then subtract two points for each group, as well as deduct any points that had been given for sekis. But this strikes me as a somewhat bothersome extra calculation. It would be better if we could make this more automatic, avoiding the need to compute the group tax.
Accordingly, a better method, I think, would be to add two extra stones (black or white, according to the colour of the group) to each group, as well as filling in any points in seki. This will automatically reduce each territory by two points, as well as removing any points in seki. Then compute the territory scores of what remains.
However, this may not work out so well in practice: The players could become uncertain if the two tax stones had been added to every group. (One could instead try placing white stones in black groups, and black stones in white groups, to help distinguish them from the other stones in their group. But then one might perhaps mistake them for dead stones that can be removed.)
I would therefore suggest that these group tax stones be of a third colour, blue for example, different from black and white. This would have the advantage that one could see at a glance if the tax had been applied to each group. Of course, one could use other objects for this purpose, such as buttons or coins, as long as they are easily distinguished from the black and white stones.
(One could even use three different colours for the group tax stones: one for the Black territories, a second for the White, and a third for any points in seki. But I do not think this is really necessary. Though it would make the final state of the board more colourful.)
So that is my suggestion, to make the ancient method of stone scoring (hopefully) more convenient:
1) Use pass stones, as in the AGA rules.
2) At the end of the game, add the special (blue) group tax stones to the groups.
3) Finally, as in the AGA rules, use territory counting.
And so, you should then know the exact difference in scores under stone scoring rules.
It is, I think, almost as simple as using AGA rules to find the area score.
I admit, this is a rather simple idea, perhaps even trivial. But I cannot find it suggested anywhere, in particular in any of the relevant sections of Senseis Library. So at the risk of some ridicule, this is sent out, in the hope that it may encourage more people to try a few games with the old method of stone scoring.
Stone scoring has an appealing codition for deciding the winner: Play until no more stones can be played on the board. Then the player with more stones on the board wins (adjusting for komi).
However, playing out the game to this point can be tedious for some players, and counting all the stones can take a while. One can avoid some of this by agreeing to end play earlier, and then use area scoring with group tax. But this counting also may take a while. The question is, is there a faster procedure to determine the final score?
Now, in the case of pure area scoring, i.e., with no group tax, the problem was, in my opinion, solved by the designers of the AGA rules. Probably most people are familiar with these rules already, so I will just mention that they use pass stones, and require White to make the final pass. Prisoners are then placed in their respective territories, and territory counting is used. Then it can be shown that the difference between Black and White's area scores is exactly equal to the difference in their territory counts. For those (like me) who find territory counting more convenient, this is very nice idea.
For stone scoring, we could follow a similar procedure: First, use AGA rules to find the difference in area scores. We could then subtract two points for each group, as well as deduct any points that had been given for sekis. But this strikes me as a somewhat bothersome extra calculation. It would be better if we could make this more automatic, avoiding the need to compute the group tax.
Accordingly, a better method, I think, would be to add two extra stones (black or white, according to the colour of the group) to each group, as well as filling in any points in seki. This will automatically reduce each territory by two points, as well as removing any points in seki. Then compute the territory scores of what remains.
However, this may not work out so well in practice: The players could become uncertain if the two tax stones had been added to every group. (One could instead try placing white stones in black groups, and black stones in white groups, to help distinguish them from the other stones in their group. But then one might perhaps mistake them for dead stones that can be removed.)
I would therefore suggest that these group tax stones be of a third colour, blue for example, different from black and white. This would have the advantage that one could see at a glance if the tax had been applied to each group. Of course, one could use other objects for this purpose, such as buttons or coins, as long as they are easily distinguished from the black and white stones.
(One could even use three different colours for the group tax stones: one for the Black territories, a second for the White, and a third for any points in seki. But I do not think this is really necessary. Though it would make the final state of the board more colourful.)
So that is my suggestion, to make the ancient method of stone scoring (hopefully) more convenient:
1) Use pass stones, as in the AGA rules.
2) At the end of the game, add the special (blue) group tax stones to the groups.
3) Finally, as in the AGA rules, use territory counting.
And so, you should then know the exact difference in scores under stone scoring rules.
It is, I think, almost as simple as using AGA rules to find the area score.
I admit, this is a rather simple idea, perhaps even trivial. But I cannot find it suggested anywhere, in particular in any of the relevant sections of Senseis Library. So at the risk of some ridicule, this is sent out, in the hope that it may encourage more people to try a few games with the old method of stone scoring.