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Territory and Area Scoring
Keywords: Rules
There is a more general discussion on the Scoring page. If you are learning the rules, start there. This page contains some finer points and comparisons of Territory and Area Scoring. It assumes that you've read the Scoring page. The most obvious difference between Territory and Area scoring is the handling of Dame and playing into your own area: With Territory Scoring:
Whereas in Area Scoring:
This may seem like a big difference: Area Scoring lets you reinforce your own territory at no disadvantage, while under Territory Scoring you'd be penalized a point. However, this isn't true unless you do it after all Dame points are filled in. Why? Because if there are dame (or real) points left on the board, a play in your own territory (which gets you zero points), lets your opponent play one of the dame (which gets them one point). Do this ten times and your opponent has ten more points than you. A more important difference between Territory and Area Scoring is that if there is a dispute about the life of stones, Area Scoring allows it to be played out. Territory Scoring requires these situations to be handled by special rulings: If you played into your own area to prove a group is dead, you'd be losing points. See Japanese Scoring Special Rulings for more info. Bill: The preceding paragraph repeats folklore that is ancient history. The Japanese rules has special rulings for 40 years, until 1989. Now they are just difficult to understand. Besides, there are territory rules that allow disputes to be settled by play, such as the Lasker-Maas rules. A small advantage of Area Scoring is that you don't have to keep track of prisoners. When removed from the board, prisoners can simply be returned to the bowls. It is a false belief that Area scoring requires a lot more counting than Territory scoring. In practice, at the end of the game Chinese Counting is used, and only Black's stones need be counted. For estimating the score during the middle game, there is no need to change methods: stones are placed in alternation, so except for prisoners, Black and White have the same number of stones on the board. Hence, only the prisoners and potential territory sizes need to be taken into account for strategic yose calculations. Charles But you can't have it both ways, if the prisoners have been returned to the bowls. I think this amounts to saying that for purposes of positional judgement the territory method is convenient. Equivalence scoring is a form of area scoring used by AGA rules and French rules. It makes use of pass stones: When a player passes, they give one stone as a prisoner to the opponent. In addition, White must make the last pass. With the addition of these two rules, you can use either Japanese Counting or Chinese Counting. The pass stones and White's playing last ensure that the winner and the difference in scores will be exactly the same with either counting method. Since there are rarely passes in the middle of a game, the pass stones don't really alter the score. White's passing last may seem like a determent to White, but since prisoners don't count under Area scoring, it doesn't change the outcome at all. The only effect of White's last passing stone it help ensure that the score using Japanese Counting is the same as it would be under Chinese Counting. In handicap games, Equivalence scoring also requires that Black give White one prisoner for each handicap stone except the first. (The remainder of this page is still in need of a WikiMasterEdit. --MtnViewMark) The EGF and the EGCC promote simple rules (either based on stone scoring or based on Ing rules with superko) or the pretence of simple rules (some sort of transforming atari go into traditional territory scoring). Stone scoring scores only each player's stones on the board. It was used centuries ago in China. For teaching it has the merit that beginners would not even notice that the game differs from normal area scoring go because reducing the number of own groups by one is worth two extra points - the two eyes that can be filled with stones. In most cases the method of scoring does not matter, as is shown by the following theorem: Theorem: In a game, where
the following holds: If White made the last move, territory and area scoring give the same result. Otherwise there is a difference of one point (to Black's advantage under area scoring and in White's under territory scoring). Proof of the theorem: First assume that White has made the last move. We will use the following notation:
(and similar form We, Wc, Ws). The result (positive if Black wins) under territory scoring will be Be+Wc-We-Bc, while under area scoring it will be Be+Bs-We-Ws Now, the fact that White has made the last move, combined with the first two conditions, means that both players have made the same number of moves. Thus, Bs+Bc=Ws+Wc. Call this total T. Simple mathematics now gives: territory result= Be+Wc-We-Bc = Be+(T-Ws)-We-(T-Bs) = Be-Ws-We+Bs = Be+Bs-(We+Ws) = area result And thus, the two outcomes are the same. If Black made the last move, a similar calculation gives: territory result = area result-1 The phrase "sekis with eyes" must be reworded more precisely. Some generalizations of such a theorem are possible. In particular a wording can be independent of such terms like "seki" and "eye" if we speak of "empty intersections not surrounded by stones of only one colour".
The third requirement in this theorem is there because of positions like this: Under area scoring the marked space is a point for white. Under Japanese rules it is not, although there are other types of territory scoring (like on some go servers) where it is. Although usually the difference is unimportant, there are some cases where the type of scoring does matter. In a handicap game, Black is better by one point per handicap stone (except the first) under area scoring than under territory scoring. For strategy, the difference only matters during the very last stage of the game. Under territory scoring one can pass rather than play a dame. Under area scoring one should always fill up the dame, because they are worth points. Reversely, under area scoring playing inside one's own or the opponent's territory instead of passing does not matter, under territory scoring it costs a point. Thus, under area scoring once all dame have been filled, you can defend a weak spot without checking whether it is really necessary to do so.
A more interesting case where the two differ is when there is one last half-point ko to be connected as well as an odd number of dame points. In this diagram, with no stones captured and Black to play, under territory scoring, Black has little choice but to connect at a, and lose by one point. Under area scoring connecting at a will also make him lose by one point, but now he has a better way to play. Under area scoring black should play the last dame at b. White can then capture at a, but Black has a ko threat at c. After White captures (or connects), and Black retakes the ko, White does not have a ko threat, so she will have to pass (or make some inconsequential move), and Black can connect at a. The reason the theorem above does not apply is of course that Black is 'forcing' White to take a premature pass move. In real go, this type of situation is rare because there are often many dame points, and in this position White could use filling up a dame as a ko threat (if Black connects the ko, White continues filling up dame and there is no forced pass, but if Black fills up a dame himself, White may retake the ko), but it can still be something to watch out for if you are in the late endgame, playing by area scoring. Above it is stated that "Equivalence Scoring" leads to the same difference in score regardless if Chinese or Japanese Counting is used. This doesn't seem to be correct in all situations: If there is a seki with a white eye with 2 empty points inside it, and Black has no eye, chinese counting should give 2 points more to White than japanese counting, correct ? (By the way: It seems that the descripions of Japanese and Chinese counting simply don't cover Seki.)
Jasonred How about killing a dead group by "filling in" its eye space at the end of a game? Or, come to think of it, dead groups... And, I think there's a significant difference in stategy in the endgame, in terms of deciding whether to place a few more stones to secure against invasion, or whether to leave it alone since it increases territory... Charles No - these comments are most likely based on misconceptions. Such changes in correct play as are require to 'convert' between scoring systems are generally minor and relate only to the very final plays.
Bill: Let me second what Charles has to say. The main strategic difference between Chinese-style and Japanese-style scoring has to do with counting eyes in seki. When there is a choice of plays one or some of which lead to such a seki vs. one or some that do not, correct play may differ between scoring styles if one player scores more points in the seki by Chinese-style scoring than by Japanese-style scoring. (I do not say area vs. territory because there are territory scoring rules that do count eyes in seki.) However, such instances are rare.
The ability of the komonster for the final ko to delay winning the ko until the opponent must pass, while it may make for a larger score difference than 1 point between the different scoring styles, rarely affects strategy. The difference would come before the ko fight. In fact, it is very difficult to come up with an example that does not involve a seki that favors one side or a final ko in which every correct option for a play under one scoring style is incorrect under the other. A few years ago I constructed one, but it was not at all easy to do. [1] However, the dame must nevertheless be filled anyway. If any dame are left unfilled, by the 1989 Nihon Kiin rules the groups they are next to are in seki, and the empty points surrounded by them are not territory and are not counted. Dame filling may be postponed until the confirmation phase after both players pass. --DougRidgway This is a copy of the living page "Territory and Area Scoring" at Sensei's Library. ![]() |