Odd Cases in the Japanese Rules

In this thread, I will discuss some interesting, and sometimes bizarre, situations that can arise under the Japanese rules.

So, without further ado, let’s begin …

Rules Pedantry with yebellz!

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Both Players Lose

The Japanese rules state:

Article 13. Both players lose

1. After the game stops according to Article 9, if the players find an effective move, which would affect the result of the game, and therefore cannot agree to end the game, both players lose.

Note that article 9 (about resuming the game) also applies:

Article 9. End of the game


3. If a player requests resumption of a stopped game, his opponent must oblige and has the right to play first.

In the official commentary, they give two examples to explain:


both-lose-2

Suppose both players have passed, while leaving one of the above situations on the board.

In both of these situations, the life and death status of the surrounded group is unsettled (white playing at A in the second case can create a seki that nullifies black territory). Both players would like to play another move at A to maximize their score. However, asking to resume the game would let their opponent play first. Hence, if the outcome of the game swings on which player gets to play, neither player would want to resume to settle the position.

In such a case, the Japanese rules punish both players with a loss, for making the blunder of passing and leaving a decisive position unsettled.

Logically speaking, the unsettled position left unresolved could be much simpler (provided that its worth enough points to swing the outcome):

both-lose-3

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Anti-Seki

The official commentary gives this position as example where both black and white stones could be considered dead:

antiseki

If both players pass, while leaving the above position on the board, then all of the black stones and the single white stone are considered dead, however, they are NOT removed from the board for scoring.

The white stone is considered dead, since it can be captured by a hypothetical move at A. Black is dead, since white can play at B and then A to capture, since black cannot use any ko threats win the ko fight (see later post about the special ko rules that apply only during the confirmation phase).

Despite being considered dead, they do not count as prisoners and white does not get any corner territory, since they are not removed. The commentary makes this clear by saying:

If the game ends like this, Black and White are both dead but none of the stones can be removed. According to Article 8 there is no territory. Compared with playing A, Black loses 3 points.

I find this to be confusing and unclear how it follows from the seemingly relevant articles in the rules:

Article 8. Territory

Empty points surrounded by the live stones of just one player are called “eye points.” Other empty points are called “dame.” Stones which are alive but possess dame are said to be in “seki.” Eye points surrounded by stones that are alive but not in seki are called “territory,” each eye point counting as one point of territory.

Article 10. Determining the result

1. After agreement that the game has ended, each player removes any opposing dead stones from his territory as is, and adds them to his prisoners.

So, it seems that the explanation might be that despite the stones being dead, they are not removed since the corner is not considered territory, which is the case since the points are either: 1) not considered surrounded by the live stones of white, or 2) the points are considered dame? I’m not sure.

Note: the phrase “anti-seki” is not coined in the official commentary, but is used on Sensei’s Library. This article also explains the double-ko seki position as an example of anti-seki.

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A Fine Line between Anti-Seki vs Both Players Lose?

This anti-seki position discussed earlier also begs the question: why shouldn’t both players lose?

antiseki

After all, if there are no ko threats, then it seems that this would be an unsettled position, with whoever getting to play first upon resumption gaining the possible decisive advantage. Hence, neither may want to resume to resolve it. However, since this position is ruled as an anti-seki, it would seem that the players could be saved by calling both the black stones and white stones dead (while not removing them and not counting any territory for white), which would limit black’s loss from making this blunder to only 3 points, which might or might not cost black the game, but still provide a clear result with one of the players winning. EDITED: The original wording of this paragraph was wrong, since I had though that the anti-seki situation could override the “both players lose” rule. However, something can be both anti-seki and both players lose.

On the other hand, if there are big enough ko threats such that black would win the ko fight, then black should ask for a resumption (which lets white play first), win the ko fight, and eventually play at A to gain those three points (especially if they change the outcome).

It would seem that purpose of this special rule is to compel black to play at A (even if black is ko master) before ending the game, preventing black from arguing for one more point (i.e., for 3 points of territory plus 1 capture).

However, from the official commentary, whether or not ko threats exist elsewhere on the board does not seem to be required for this position to be considered anti-seki. It would appear that the key feature that distinguishes this position is that there are both black and white stones that can be captured by whoever moves first.

If we accept this logic, would the following positions also be anti-seki (if both players pass and leave them unsettled)?
Or would that result in both players losing (if their status affects the outcome of the game)?

EDIT: The below positions are indeed anti-seki, however they can also result in both players losing if the game close enough that the outcome swings on their unresolved status.

antiseki-2

antiseki-3

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Ok, that’s enough pedantry for tonight, but I still have other topics that I would like to discuss, including at least:

  1. Special ko rules when determining life and death after passing.
  2. Moonshine life.
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i got a big head after reading this.

just want to ask: do these kinds of situations happen in chinese rule? or they just resume game. and incidentally, does the “other side play first” rule apply in chinese?

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I believe the above situations are unique to the Japanese rules, and maybe also the Korean rules, which are a similar territory scoring rules set. However, I’m completely uncertain about the technical details of the Korean rules, since I have not looked into those.

Under the various area scoring rules, if the game has to be resumed after both sides have passed, I believe they all simply continue with whichever player’s turn it would naturally be. So if white passed second, black gets to play first at resumption, and vice versa.

Special Ko Rules when Determining Life and Death After Passing

During the normal course of play, the basic ko rule (which is universal across all go rules) is in effect:

Article 6. Ko

A shape in which the players can alternately capture and recapture one opposing stone is called a “ko.” A player whose stone has been captured in a ko cannot recapture in that ko on the next move.

When a ko arises that both players want to win (e.g., the life/death of a large group may depend on ko), they must fight for it by making ko threats elsewhere in order to retake it. Thus, the existence, size, and balance of ko threats across the whole board will determine who wins a ko fight and ultimately how key positions will be settled.

A classic example to illustrate this point is the “Bent Four in the Corner”. In particular, let’s consider the below shape, which is a temporary seki, where white could play at A in order to force black to capture 4 stones, but be left with the bent four in the corner shape with white to play.

7-seki

From the bent four in the corner position, white can start a ko fight in an attempt to capture the black stones:

3-ko

Whether this would be successful depends on the status of ko threats on the rest of board. Black may even have enough large unremovable ko threats, such that white would never be able to favorably win the ko threat. This would make black’s stones (in the first figure above) seemingly invincible, and white should not collapse the seki to start the ko fight.

However, in spite of this, black’s stones are still dead under Japanese rules.

White should never actually play at A in (the first figure), since the position will be ruled to be dead, regardless of what ko threats black has. This is the case, since the life and death confirmation phase introduces a special ko rule different than that used during normal play:

Article 7. Life and death


2. In the confirmation of life and death after the game stops in Article 9, recapturing in the same ko is prohibited. A player whose stone has been captured in a ko may, however, capture in that ko again after passing once for that particular ko capture.

This rule has the effect of nullifying normal ko threats. Whether or not black has other ko threats becomes essentially irrelevant, since these threats would not allow black to retake the ko.

Note: the life and death confirmation phase are not actual additional plays, but rather the consideration of hypothetical, ideal play, just for the purpose of resolving life and death. For scoring, the board position, from immediately after the two passes, is restored, but with dead stones removed as prisoners (except for the case of anti-seki as discussed earlier).

Article 9. End of the game


2. After stopping, the game ends through confirmation and agreement by the two players about the life and death of stones and territory. This is called “the end of the game.

Article 10. Determining the result

1. After agreement that the game has ended, each player removes any opposing dead stones from his territory as is, and adds them to his prisoners.

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Compulsory Dame Filling to Prevent Technical Sekis

In Japanese rules, eyes of groups in seki do not count as territory. This quirk of the Japanese rules could possibly be a holdover from the group tax effect of stone scoring rules, a historical forebear of the Japanese rules, (see this post in Pondering Upon The Rules Of Go which also links to an article discussing the history of the rules of go), although certainty of its origin is likely lost to history.

However, this rule is loaded with complexity since one must define what is seki in order to distinguish whether eyes should count as territory. It can be very difficult to distinguish between seki and living groups. The concept is difficult to pin down with a definition that attempts to count eyes, false eyes, etc., since there all sorts of contrived positions like non-seki living groups the only appear to have false eyes, or complicated hanezekis and hanezeki-like positons. Ultimately, the Japanese rules simply define seki as living stones that are adjacent to dame:

Article 8. Territory

Empty points surrounded by the live stones of just one player are called “eye points.” Other empty points are called “dame.” Stones which are alive but possess dame are said to be in “seki.” Eye points surrounded by stones that are alive but not in seki are called “territory,” each eye point counting as one point of territory.

This rule has the side effect of compelling players to fill nearly all dame (except those that must be left unfilled to preserve actual sekis), since otherwise any non-seki living stones that are adjacent those dame points would be considered seki and have their territory nullified.

It’s common practice for players to leave dame unfilled when playing with Japanese rules. This is a result of the common misconception that dame do not have to be filled under Japanese rules, however, as we see from the discussion above, the opposite is technically the case! I’ve previously discussed this discrepancy between this common practice and the actual Japanese rules here: Japanese Rules Popularity

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Compulsory Capture of Dead Stones

In most situations, the Japanese rules compel players to pass before capturing all strategically dead stones, since playing additional moves to actually remove dead stones would reduce one’s points under territory scoring. For example, consider the following position.

dead%20stone

In this corner, black has 4 points (3 from territory plus 1 for the white prisoner). However, if black were to play an additional move here (at the end of the game, when they should pass) to capture the white stone, black would only get 3 points (2 from territory plus 1 for the prisoner).

It is the following rule that allows black to simply remove the single white stone without capturing it, since it is a dead stone within black’s territory.

Article 10. Determining the result

1. After agreement that the game has ended, each player removes any opposing dead stones from his territory as is, and adds them to his prisoners.

However, the fine print of this rule is that dead stones are only removed from territory, as we just discussed in the previous post, eyes from groups in seki do not count as territory.

Consider this example from How does this get scored (Japanese)?

The position is a seki, and the single white is dead, but it is not removed and not counted as a prisoner, if black does not play another move to actually capture it. Hence, black should play another move (which should be delayed until the very end of the game, since it is not urgent) to actually capture that white stone, in order to a get net gain of 1 point. Note that there is already zero territory to lose (from self-filling), since it is an eye from a group in seki.

The Japanese rules commentary actually gives a slightly more complicated example to illustrate this concept:

Here, not only should white capture the two black prisoners, black is then compelled to throw in another stone (to prevent the seki from collapsing), which white should then capture again before ending the game. Thus, white should extract 3 points (all from prisoners) from this position.

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Tankyou yebellz fo both of you replies. They were very helpfull
.

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