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DougSGoBlogJune2003

 

Stone Counting Scoring
    Keywords: Rules

Ancient Chinese Rules involved playing until no more stones could be put on the board without jeopardizing life of the groups. Then the stones are simply counted. Since only stones are counted toward the score, one doesn't want to pass until all one's own territory is filled except for the two eyes required to give each group life.

In general, this imposes a two point 'tax' on each independent living group: The two points that are the eyes required for life don't count toward the score.

See Ancient Chinese Rules And Philosophy for more on this.

(If you are looking for information about the simple counting method for Area scoring rules, which is sometimes called "Stone Counting", see Stone Counting Method.)


BillSpight: There is ancient and there is ancient. ;-)

Stone counting was the norm in China during the Ming Dynasty. As Ancient Chinese Rules and Philosophy indicates, there is evidence that earlier scoring was territorial.


(What follows is a discussion of passing and the two point 'tax' vis-a-vis the ancient rules. Reading through to the end reaches a conclusion, and so this section still needs a WikiMasterEdit.
--MtnViewMark)

Stone scoring went out of general use in China in the early part of the 20th century, presumably because the strong players were learning from Japanese sources. An effect of the old Chinese rules was not to score 2 eye spaces per independently living group.
--RobertJasiek

In the ancient rules, passing is not allowed -- this translates to the "don't count the 2 spaces for eyes" rule -- also known as the [two-point group tax|group tax]. John Fairbairn could probably give you more details about this history.
--JonathanCano

[Diagram]
Passing disallowed?

I don't think the two point 'tax' is equivalent to disallowing passing (if you mean that you lose if you have no move other than passing). In the diagram shown, White has three points after tax, while Black has four. But I think White can win the no-pass game, whoever starts.

''There is no group tax in this diagram. What you are seeing, is that this kind of game is decided by number of distinct eyes, not by the size of the eyes. This kind of situation can occur when a MolassesKo is on the board --Bass''



In the position above, white has played 20 stones (that we can see, perhaps more if there have been captures) and black has played only eleven (again, 11 that we can see). Also notice that W occupies much more area than black. While black has more "Japanese" territory in the diagram above he white must have at least 9 prisoners (since black is not allowed to pass). By either Chinese area scoring or Japanese territory scoring white is way ahead and should win so saying that the diagram above proves that "2 point group tax" does not equal "no passing allowed" is false.

Of course black and white both have the same number of groups above (1 each) so any possible tax cancels out. A proper counter example to my claim would probably have an uneven number of black and white groups.

Cheers,

Jonathan Cano Robert Jasiek has replaced some "counting" by

"scoring".

[Diagram]
13x13 version

No. Consider this version on a 13x13 board. Each player has two groups and 77 stones. White has three points after tax. Black has four. Black to play, White wins.



Excellent! I had a suspicion I was wrong and __your last diagram proves it__.

Ah, I think I remember a modification to the ancient rules that do properly implement the 2 point group tax. Here it is:

  • both players must move. The first player who can not move loses.
  • A move consists of placing a stone on the board __or returning a

captured stone to your opponent__.

I believe these modified ancient rules give the desired 2-point group tax when used for your diagram above.

for example, if black has to move next then he should win by 1 move.

[Diagram]
black wins with modified ancient rules.

[Diagram]
black wins with modified ancient rules (cont).

Black 7: return the captured stone white 2.

When black plays 11 at A white has lost.

If we start the problem with white moving first then black wins by 2 points. (this is left as an exercise)

Thanks for helping remember the proper rules for implementing the 2- point group tax.

Jonathan Cano



[Diagram]
White wins.

This is group tax in effect. -- Bass



[Diagram]
W to play

Robert Pauli: You could have done it simpler, Bass.

White wins under no-pass rules, but area scoring leads to a tie.



This is a copy of the living page "Stone Counting Scoring" at Sensei's Library.
(OC) 2003 the Authors, published under the OpenContent License V1.0.