Sub-page of IkedasRule

Why should Ikeda's Rule be used in Area Scoring games?

This rule solves one of the most grave drawbacks that area scoring exhibits:

  • If in the Endgame there is an even amount of dame to be filled and it is blacks turn then black could mend his territory instead if filling a dame without fear of losing points of moku for this blunder.


It is not a grave disadvantage and it is not a disadvantage of only Area Scoring. Whenever a player is safely ahead (by more than 1 point), he can defend his territory instead of filling a dame. Even under the Japanese 1989 Rules, which use Traditional Territory Scoring and where filling of dame can be worth up to hundreds of points (by eliminating the rules-technical in-seki), defending one's territory can precede filling of dame. Furthermore, one should not discuss some arbitrary (dis)advantage but compare all (dis)advantages of scoring methods.

Ikeda Territory I Scoring is especially attractive for replacing Traditional Territory Scoring because, instead of complex life and death definitions, one and only one actually played move-sequence suffices to determine all statuses on the board.


Flower: As far as I understand if area scoring is used and there is an even amount of dame then the one whose turn it is, can mend his territory 'without risk' even if he is not in the lead. If I read your example correctly then you only refer to mending your territory if you are in the lead in combination with losing a small portion of this the lead. In a discussion on KGS I heard several people quoting this as a disadvantage of area scoring as suboptimal play has no consequences to the score in this singular case. --Flower, 2007-02-25

All [ext] objective advantages of the scoring methods should be discussed. Discussing only one aspect misses their mutual context. --RobertJasiek

Flower: Thanks for the link I will read it as soon as possible :) While I agree that all advantages should be discussed this is not possible if singular aspects of it (like my question) are not discussed. Though it is of course not your duty to answer them :) But let me read the link. Mayhap it contains the answer. --Flower, 2007-02-26

[ext] Nobrowser: A problem with the "more interesting" argument for Ikeda's Rule is that it can be turned around. Yes, unless the rule is adopted, the player with the move at the end of the game can "safely" (ie. without reading/thinking) make a reinforcement move if the balance of the score (including komi) favors her by 0.5. If the balance is more, reinforcement is always safe, Ikeda or no Ikeda. But if the rule is adopted and the balance is 0.5, the player can still avoid reading - reinforcement is a sure loss, so she may as well fill a dame point and hope she lives.

There may still be an argument for the rule, but it would have to appeal to fairness (ie. the usual 7.5 komi for area rules may be too much), not "interest".

--- Flower: Hmm after reading Mr Jasiek's link as well as his IGRF reports. I came to doubt that the term 'Ikeda's Rule' informally refers to Rule 7 Area Scoring III as it is too close to the term 'Ikeda Rules' which were used to refer to Ikeda Territory Scoring I. I thought about requesting that this page is to be renamed Ikeda's Button. Yet this would indirectly imply that Mr. Ikeda cloned Button Go and would do the honorable Mr. Toshio injustice. I am open for suggestions :D (for now I will change this article and note its ambigous name)

Bill: I just did a web search and the only place I found that clearly refers to Ikeda's Rule as is meant here, is this page! So maybe it is premature to say that Ikeda's Rule means his area III rule 7.

Flower: Aye that is what I thought too after I read Robert's IGRF reports. Before that I heard the use of 'Ikeda's rule as referal to A3 rule7, plenty of times though. But only on KGS.(primarily in discussions about Territory and Area Scoring (and or) Button Go) Of Ikeda's creations Ikeda Territory Rules I and Ikeda Area Rules III (of which Rule 7 is its essence) are certainly his most noteworhty. So both terms kind of deserve a mnemonic so that one is not forced to use the unwieldy name Ikeda defined. (No one wants to say "do we score using Ikeda Area Rules III rule 7?" whereas "do we use a Button?" or "do we use Ikeda's Rule" sounds more natural.) So our question would be:

  • How do we determine the spread of 'Ikeda's Rule' as synonym for Ikedas Area Rules III Rule 7?

and if we determine it is not spread far (as one might assume) What mnemonic shall we create for pagetitle and rule?

  • Ikeda's Button?
  • Rule Seven?
  • IA3R7?
  • Ikeda's Area Scoring Rule?
  • Ikeda's Taiwan Rule?
  • Taiwanese Rule? (allthough it differs as Ikeda defines it by passing)

Bill: Thanks for giving the source. I think that Ikeda's Rule is OK. That's how language works. Shall I try a Master Edit later today or tomorrow?

Flower: Master Edit sounds a bit harsh :) (like throwing away everything that was before) But feel free to try it. As written above I thought of doing it too (if I were not supposed to cook for my mate who will be home at 2015Z whereupon we will embark upon watching Star Trek TNG :) So if you like do it now :). Otherwise I will embark upon it as soon as convenient or the muse inspires me :)

Flower: I just tried to begin the edit, but I am too tired to be productive. It can be found under /wme. Feel free to edit it yourself :) (I hope I am in a better shape tomorrow) Good night!

Flower: Obviously I did not yet come around to do it :) (swamped with work) But eventually I'll do it :) (at least I want to)

Bill: I am not sure that it should not be called Davies' rule. I would like to see Ikeda's original Japanese text. My impression is that Ikeda focused on the last competitive move rather than the first pass. Perhaps Davies improved upon Ikeda.

Flower: I only have Davies Translation. Well and given my ignorance of Japanese this might not be so bad :) I had the impression though (without rereading it now) that Ikeda spoke about passing in order to detect the last competetive move directly. Of course Davies might have changed that by himself and for some reason omitted mention of it. Without the original we cannot be sure. Yet these are initial hypotheses that are worth investigating but not yet worth acting upon. It would only add to the confusion to swap Ikeda with Davies now (and without sufficient proof :)

Bill: Here is a quote from Ikeda's text about Area rules III in Section 4.1.

"It was also stated that this problem can be solved by deducting half a point from Black's score and adding half a point to White's score when Black makes the last competitive move.

"If we add this rule of half a point for the last competitive move to area rules II, we will have area rules III."

Since this is *not* Ikeda's Rule, I wondered about its true origin. However, just now I found this:

"We can accomplish our purpose by formulating the definition of the last competitive move in the rules in the following way. A player's score is the number of stones that player has on the board plus the number of empty points in that player's territory. If the first pass was made by White, however, then half a point is subtracted from Black's score and added to White's score. This is rule 7 (the rule of scoring) in area rules III."

That is Ikeda's Rule. :-)

Flower: Indeed :-) I note a uncanny similarity to a paragraph located in the middle of the main body though :) (Thanks for your research and double-checking)

This section is an archived past 'in-document' discussion about the clarity of the article. (will eventually be deleted)

Ikeda's Rule is a term sometimes encountered when discussing Territory vs. Area Scoring.

To be precise it should be called "Ikeda's Rules" as the term can be traced back to Ikeda Toshio's [ext] On the Rules of Go wherein he proposes six whole rulesets for Go and not a singular rule.

Bill: I think that muddies the waters instead of adding precision.

Flower: You mean it sacrifices clarity for precision? What would you propose then? (or do you think we should omit "to be precise it should be called Ikeda's Rules" here as it contradicts the usage on this page thus creating a inconsistency?)

Bill: There are six different sets of rules identified with Ikeda. Any of the rules in one of them could be called Ikeda's rule. However, natural language usage has singled one of them out for that honor. Not exactly logical, but there we are. I would propose a footnote to mention the rules.

Flower: Aye that sounds feasible :-) I will try to rework the body in the near future then. In order to do so I would move this thread (including a quote of the part you commented on) into a '----' fenced off section of the /discussion. You may cry 'Nooooooooo' if this ails you now :)

Bill: Please, go ahead. (And erase this exchange, as it will have served its purpose. ;-))

Flower: Would the added disambiguation help? (which would allow us to clean up the body of the article as the it is taken care of in front.

IkedasRule/discussion last edited by Nobrowser on March 29, 2021 - 23:30
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