Odd Cases 🤔 in the Japanese Rules

After you mentioned it I could see it as a 6x1, because normally we can see the lines between the stones.

maybe instead of

:heavy_minus_sign::white_circle::heavy_minus_sign::white_circle::heavy_minus_sign::black_circle::heavy_minus_sign::black_circle::heavy_minus_sign:

have

:heavy_plus_sign: :heavy_minus_sign::white_circle::heavy_minus_sign::heavy_plus_sign: :heavy_minus_sign::white_circle::heavy_minus_sign::heavy_plus_sign: :heavy_minus_sign::black_circle::heavy_minus_sign::heavy_plus_sign: :heavy_minus_sign::black_circle::heavy_minus_sign::heavy_plus_sign:

[I know the pluses make no sense since there’s no intersection on the 9x1 or nx1 board.]

That’s kind of interesting actually. I was wondering how to interpret it. So it’s because the dame can’t be filled without some kind of capturing occurring. It’s kind of like that send two return one position kind of.

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Yes, playing at the dame point would be like sending two, returning one. Hence, neither player should do that since it would only lose a point.

If plus signs are preferred, I would rather use just a single symbol, since having three emojis spaces out the stones too much.

:heavy_plus_sign::white_circle::heavy_plus_sign::white_circle::heavy_plus_sign::black_circle::heavy_plus_sign::black_circle::heavy_plus_sign:

:heavy_plus_sign::white_circle::heavy_plus_sign::white_circle::heavy_plus_sign::black_circle::heavy_plus_sign::black_circle::heavy_plus_sign:

Note that there are no spaces between the emoji codes, which leads to them being placed closer together.

:heavy_plus_sign: :white_circle: :heavy_plus_sign: :black_circle: :heavy_plus_sign: leads to
:heavy_plus_sign: :white_circle: :heavy_plus_sign: :black_circle: :heavy_plus_sign:

Another 2D diagram example

:heavy_plus_sign::white_circle::white_circle::black_circle::heavy_plus_sign:
:white_circle::heavy_plus_sign::white_circle::black_circle::heavy_plus_sign:
:white_circle::white_circle::black_circle::heavy_plus_sign::heavy_plus_sign:
:black_circle::black_circle::heavy_plus_sign::black_circle::heavy_plus_sign:
:heavy_plus_sign::heavy_plus_sign::heavy_plus_sign::heavy_plus_sign::heavy_plus_sign:

Code:
:heavy_plus_sign::white_circle::white_circle::black_circle::heavy_plus_sign: :white_circle::heavy_plus_sign::white_circle::black_circle::heavy_plus_sign: :white_circle::white_circle::black_circle::heavy_plus_sign::heavy_plus_sign: :black_circle::black_circle::heavy_plus_sign::black_circle::heavy_plus_sign: :heavy_plus_sign::heavy_plus_sign::heavy_plus_sign::heavy_plus_sign::heavy_plus_sign:

However, one has to clarify that this is the top-left corner

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Could try and get the markdown that they use on Boardgame stack exchange where they $$ and it turns in to a go board image :slight_smile:

You can even do nx1 boards :slight_smile:

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So is this the most modern version of the Japanese rules linked in the OP?

Is there a formulation of the Japanese rules that are a bit cleaner and don’t involve a case where both players lose?

Actually in that link I don’t like

Article 7. Life and death

1. Stones are said to be " alive " if they cannot be captured by the opponent, or if capturing them would enable a new stone to be played that the opponent could not capture. Stones which are not alive are said to be " dead ."

I know one of the comments says that you can apply this recursively to various snapback situations - (which just seems like a pain that should be ironed out of the wording of the rules).

image

I really hate that wording however, in principle it’s supposed to tell me that in situations like the above blacks two stones are alive because when white goes to capture them black can play at 4-2 (row-column) and that stone can’t be captured. But actually couldn’t you just read it where black just adds any stone to an already alive group? It just doesn’t make any sense.

That and when you have to add a commentary on your list of rules that’s actually longer than the list of rules, maybe the rules aren’t very clear.

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In my original post, I linked to an English translation of the official 1989 Japanese rules. I believe that is the most recent official rules, as used by the Go associations in Japan.

Several people have proposed alternative territory scoring rules that at least loosely adhere to the traditions of the Japanese rules, although they excise certain parts they don’t like, which necessarily departs from the official Japanese rules.

See the “Other Japanese Style Rule Sets” section on this page:
https://senseis.xmp.net/?JapaneseRules#toc3

I think the “Japanese-like rules” used by KataGo are a particularly interesting example. These are influenced by the Spight Japanese Style Rules, and although they introduce a significant departure from the Japanese rules by adding the ability to “play on” (under special rules) to decide life/death, they aim to produce almost the same strategic results as the official Japanese rules (except in some relatively exotic cases).

These rules were mentioned earlier in this discussion, involving the author of KataGo (and those rules), @hexahedron.

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A Curious Position

In another thread, @S_Alexander offered an interesting position that occurred in one of their recent games.

Spoiler: strategically speaking, this local position most likely would ultimately be a seki, unless it turns out to be useful to sacrifice as a potential ko threat. However, even without an ongoing ko fight, understanding why this is a seki involves some interesting considerations in regards to the rules. Clearly, any further move by Black would be self-atari, although which self-atari crucially matters for finding an effective ko threat. White, on the other hand, could also self-atari to make a ko threat, but also have potential moves that would lead to some interesting considerations of the rules.

Possible Usage as a Ko Threat

Let’s first consider, hypothetically, if there was a large, ongoing ko fight elsewhere on the board.

By Black

If White has just taken the ko, and it’s Black’s turn to find a threat, then Black could potentially consider playing T3 as a ko threat. Of course, this would be self-atari, which would only strategically make sense if potentially winning the ko fight was worth offering the sacrifice of this large corner. If the ko fight elsewhere was indeed worth a very large amount of points, then White might even ignore this threat (to end the ko elsewhere), which would allow Black to then play T1, which would convert the status of this corner from a seki into another ko that would need to be settled.

Note that if Black instead attempted to play R2 as a ko threat, that would be a huge blunder that should be ignored by White, allowing White to win the ko fight elsewhere. Then, even if Black later followed up on the threat by playing at T1, White could just take back with S1, which would turn Black’s group into a dead “Bent Four in the Corner”. Hence, Black playing at R2 would only die in gote, since R2 by Black does not require an immediate answer by White.

By White

If Black has just taken a ko elsewhere, White might consider to play in this corner as a ko threat. White could do so by playing at T3, which would prompt a response by Black at T1, if responding to this threat is worth more than winning the ko elsewhere. White would now no longer have any immediate ko threats in this unsettled corner position. White could eventually take back at T2 to reset the local position into a seki, or Black might eventually follow-up with R2 to eliminate white from this corner (to gain some territory and captures), however, both of those moves are gote, which makes them ineffective as ko threats.

On the other hand, White could instead play a ko threat with R2, which would necessitate a response from Black at T1 (assuming that this threat is big enough). The seki position has now collapsed and White’s remaining stone in the corner is dead. However, White could eventually play at S1, perhaps as another ko threat, which would require Black to respond at R1 in order to prevent White from coming back alive (in seki) with a followup play at R1 to nullify Black’s territory in the corner.

Note that after the sequence W R2, B T1, W S1, B R1, White’s stones are dead, and Black is fully alive (not in seki) in that corner. This position is settled, and neither player should waste any more moves in that corner. However, it is of interest to note that this is an example of a “Dead Ko”, where playing on to actually capture the White stones could start a ko pattern, but White can never “win” this ko by resolving it in their favor. Ultimately, this position should be ruled dead during the confirmation phase, however, this situation becomes very peculiar when elsewhere on the board there is also a source of infinite ko threats (such as the double ko seki that we discussed earlier), which would cause this to become an example of Moonshine Life. I will discuss Moonshine Life in more detail in a future post.

A Cycle that Does Not End with “No Result”

Now let’s consider if there are no ko fights elsewhere and everything else on the board is fully settled, and imagine that White is behind in points (with this corner shape called as a seki).

In this case, although the position should locally be a seki, it is possible for White to still force the game to continue by playing the 3-move “sending two, returning one” cycle:

  1. White at T3
  2. Black at T1
  3. White at T2
  4. Black passes

Note that White yields two prisoners to Black in each cycle, while only getting one back, hence the name “sending two, returning one”.

Assuming that the game is close enough that Black cannot afford to lose those stones, this cycle is forced to continue (at least for a while), and thus White could force the whole-board position to repeat. White might mistakenly think that they could claim that this game is now a “no result” (which they might prefer over conceding the loss), however, recall the exact wording of article 12:

Article 12. No result

When the same whole-board position is repeated during a game, if the players agree, the game ends without result.

The crucial words are “if the players agree”. If White tried to pull such shenanigans of forcing a “sending two, returning one” cycle in order to attempt to claim a “no result” for cycling, Black should simply refuse. The Japanese rules do not have a superko rule, so this cycle can continue, if White persists, however, since Black gets a net gain of one prisoner in each cycle, eventually Black will gain enough points to simply abandon their stones in the corner and still win. Thus, there’s no strategic advantage for White in persisting with this cycle, as all they would accomplish is to lengthen a lost game, which would probably be viewed as rude (if White understood what they were doing).

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Ambiguous Article Regarding Which Stones are in Seki

In an earlier post regarding Compulsory Dame Filling to Prevent Technical Sekis , we discussed the consequences of this article 8 of the rules, which defines seki by the presence of dame:

However, note that the sentence “Stones which are alive but possess dame are said to be in seki.” is somewhat ambiguous as to what exactly is meant by “stones” (whether only a solidly connected chain, or possibly some larger strategic group) and “possess dame” (whether that only means a chain being directly adjacent to dame or some broader sense of possession).

We came across an actual situation in a game that both illustrates this ambiguity and where the outcome of the game hinges on the specific interpretation (i.e., it makes a one point difference that decides between B+0.5 and W+0.5). Here is the key position in the bottom-right of the game, where there are black and white stones in seki, due to the unfillable dame at Q1:

Under one reasonable seeming interpretation of Article 8 (in isolation), one could perhaps say that “stones” is meant to mean a solidly connect chain (e.g., Black has two separate chains in the bottom-right area, with one 6-stone chain around Q2, and the other 14-stone chain around S4) and that “possess dame” means for a chain to be directly adjacent to a dame point (i.e., only the 6-stone black is adjacent to the dame point at Q1). With this interpretation, the eye points at R3 and T1 would not count as territory, since the 6-stone Black chain and 5-stone White chain are in seki for being adjacent to Q1. However, one could argue that the 14-stone Black chain is not in seki, since it is not adjacent to (and hence does not “possess”) the dame point Q1, which would then allow one to count the eye point at S5 as territory.

However, despite the above interpretation seeming reasonable (and being relatively easier to clearly define), it is not the correct interpretation intended by the Japanese rules. In actuality, all 20 of the Black stones in that corner should be viewed as a group that collectively possess the dame at Q1, which invalidates both eye points R3 and S5 from being counted as territory.

This correct interpretation is not obvious from reading the main articles of the rules alone, however (as pointed out by Robert Jasiek in this LifeIn19x19 forum thread), this interpretation is implied by the commentary in Example 24 of the “Examples of Confirmation of Life and Death” addendum to the official Japanese rules. Further analysis of the Japanese rules to explain this in more formal detail can be found in Robert Jasiek’s extensive commentary on Japanese rules.

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Never Mind the Ko, Here’s the Dead Group

In another thread, @le_4TC threw down the proverbial, pedantic gauntlet…

Chinese Rules Analysis

In order to appreciate and understand how peculiar this position is under the Japanese rules, we should first analyze and make sense of it under the Chinese (or similar area-scoring) rules, where complicated life-and-death is settled by the principal of “playing it out” (which is not what is done under Japanese rules, of course).

Let’s first examine the position superficially, by imagining that either the left or right existed in complete isolation from the other. If we pretend that all of the black stones on the right side (on the D column) were alive (say, by imagining that there were no pesky white stones on the right side), then the white group on the left would clearly be dead, since black could almost-fill with the bulky-five shape. On the other hand, if we were to forget about the status of the left-side (imagining something different where the white stones on the C column were unconditionally alive), then the right side could either be converted to a simple seki, or potentially played out (or left as is) as a ten thousand year ko.

However, in this position, both sides simultaneously exist, which leads to some interesting complications.

Let’s consider all of White’s options if it were their turn to play. Of course, A1, A4, and F1 are all self-ataris that would lead to all White stones dying. White could play F4 to convert the right side into a (temporary) seki…

However, from this position, Black would simply proceed to capture the White stones on the left side and then be free to capture remaining White stones on the right side as well. Hence, F4 also clearly leads to all White stones dying.

The final option for White is to start the ko fight, however this is a ten thousand year ko, where Black gets to take first…

and since White does not have any ko threats, all White stones will eventually die. Hence, it does not seem that playing any stone for White is a good idea. To see if passing does any better, we need to see what Black’s options might lead to.

Now, let’s look at Black’s options if it were their turn to play. Of course, if Black were to consider starting the ko fight…

then White gets to take the ko first, and Black does not have any meaningful ko threat (since even an atari on the left side would simply be answered by capturing with F1), which now leads to all Black stones dying.

Another option for Black is to play at E1, but that is bad as well, leading down this path…

where this is a capturing race that Black would lose.

Finally, let’s consider what if Black simply just decided to try to capture the White stones on the left side first…

which requires Black to follow up to kill the bulky five, however this now allows White to start the ko fight and make a ko threat on the left…

It would be futile for Black to respond to the ko threat, since that would merely allow White to retake the ko, and eventually kill all Black stones…

Instead, Black should ignore the ko threat, which leads to this final settled position…

where both Black and White control 12 points of area. However, if we compare to the original position above, Black is worse off, since originally, Black had 10 stones and White only had 9, and neither player had any territory. If this contrived 4x6 game had a 0.5 komi, then playing out the above capture attempt and ko fight, would even cost Black the game!

Thus, it does not make sense for either Black or White to play any move from the original position. Under area-scoring rules (with the play-out disputes principle), neither player should try to assert and capture any of their opponents stones, and hence, all of the stones in the original position would be considered alive in seki, which leads to a outcome of B+1 (if there is no komi).

White is entirely dead under Japanese rules

The above analysis is still valid to consider, from the perspective of deciding that both players should pass. White can only lose everything by playing further another stone (and hence should pass). The best Black can do is split the board (as shown in the last figure above), which turns out to be now much worse than what would result if Black simply passed.

What makes the Japanese rules behave very differently, is that the life/death status of position has to then be evaluated under a very different sort of ko rule (which we also discussed earlier in this thread)…

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.

To decide upon life/death after both players have passed, the players consider the best possible hypothetical play outs, while applying a very different sort of ko rule that essentially nullifies ko threats. Thus, even though a group might not be killable during the normal course of the game (before passing) since the cost of the ko fight would be too great to make it worthwhile, that group could possibly be considered dead (after both players have passed) during the life/death confirmation phase since this special ko rule nullifies the potential cost of actually fighting the ko!

In our example, Black could demonstrate that all of the White stones are dead with this hypothetical play out that begins similarly to as discussed above…

However, now, White starting the ko threat with move 4 is futile, since the ko threat at 6, won’t let White take back the ko…

Black should now respond to the ko threat with 7 (keeping the left side White stones dead), and it would actually be illegal for White to play at 8 (taking back the ko)…

In order to take back the ko, White first needs to instead pass, which would allow Black to then win the ko with move 9 at F1, and thus lead to all White stones dying.

Thus, under Japanese rules, from the original position, both players should pass, and all White stones should be ruled as dead.

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Maybe this is better here, from this topic Comparing and contrasting to chess - rules complexities - #3 by bugcat

So why is it the case that Black needs to capture stones that appear to already be captured in a snapback?

If this position or the other linked position

showed up on a game on OGS, and it was scored manually or by Katago, and someone claims that it was scored incorrectly to count the stones as dead, and should be played out, would that be upheld by moderators?

Here’s a demo board for the first diagram

ignore the moves up to 33, and then white to play.

I guess one would say the position is seki by reading out the followups and yet in a normal snapback one wouldn’t bother calling it a seki and wouldn’t force Black say to capture the snapback stones.

I guess Black might be the one that wants to play here to avoid a seki, since B would lose, assuming the rules are clear regarding it, and both agree that it would be a seki as is.

Of course if B didn’t agree it was a seki, Black wouldn’t want to play and give White points from recaptures. White also wouldn’t want to play first because it would give B one extra capture than the sequence where B plays first (I think). I guess it has a seki feel to it.

(Maybe White should play F6 to be completely safe in the demo board, and let Black play first)

I guess it is covered in the examples here Article 1. The game of go

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More information about this particular position: Torazu sanmoku at Sensei's Library, which is also called “three points without capturing” (in translation)

It is specifically discussed in the “Examples of Life and Death Confirmation” part of the Japanese rules commentary. See “Positions Related to Article 7, Clause 1, Life-and-Death Example 1: Three Points Without Capturing”. Under the 1989 Japanese rules, it is treated like a seki if it is left as is by both players at the end of the game. See the explanation in linked commentary.

KataGo uses a formalized version of the Japanese rules that adds the ability to resolve life and death disputes by “playing it out” (albeit with complicated ko rules to mostly match the behavior of the Japanese 1989 rules). However, KataGo’s nearly-Japanese rules do not behave exactly the same.

From: https://lightvector.github.io/KataGo/rules.html

I believe the nearly-Japanese rules should correctly handle a wide variety of details, so long as both players play to rationally maximize their score. For example:

  • Bent-four-in-the-corner will die regardless of external ko threats.
  • No territory in seki, including no territory for one-sided dame (a common quirk of simpler territory rules).
  • Double-ko-seki and thousand-year-ko are sekis, double ko death is a death.
  • One should finish a direct ko rather than leave it open, even if there are enough ko threats to pass and still leave it open, but multi-step-ko need not be finished.

A known difference is with three-points-without-capturing, and a few other exotic rules beasts are also known that will cause a difference, but these should be very very rare.

*emphasis added

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That’s pretty interesting actually, thanks for that :slight_smile:

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Two-time British Champion Terry Stacey discussing the torazu sanmoku in his regular BGJ column Go Paradoxes, which seems to have been a lot like a printed version of this thread.

Remember that the torazu sanmoku was a current feature in the Japanese rules of the time (the 1949–89 version). Note also that (correct me if I’m wrong) the Japanese rules were the ruleset used officially all across Europe when this article was written.

So whilst the torazu sanmoku is a historical feature for us, for Terry’s readership it was a genuine occurrence which could potentially decide their games.

image

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In light of the rules which given British Go in the modern day, how is the torazu sanmoku treated by AGA scoring?

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So it is still confusing then, because there’s situations where either player to play loses, but a seki also loses for black?

Is one supposed to be able to claim 3 points for some reason?

I don’t know what the modern ruling is then.

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According to the senseis page that @yebellz linked to, scoring it as 3 points for black without capturing is obsolete since the 1989 version of the Japanese rules.
If black does not capture, it is now considered a seki (so no points for black). It’s better for black to capture before passing. After playing it out correctly, white loses 5 stones total and black loses 3 stones total, so black ends up scoring 2 points, instead of 3 points as it was before 1989.

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It’s always a mistake for white to capture.
Under area scoring, black should also capture at some point (otherwise white could claim a seki with 4 points for white vs 1 point for black) and with the same continuation as under Japanese rules, both players would end up with 3 stones in that block of 6 intersections. So it would be 0 points, but white lost 5 stones vs black 3 stones, so those 2 lost white stones are not elsewhere on the board and this is again a 2 point gain for black.

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Under area scoring, the result is the same whether white plays first or black plays first (white of course would prefer to leave it as seki). But the result in both cases is again “three points for black” when counting territory-wise. You can check it by verifying that “territory-scoring-rulesets” which decide territory “like chinese rules” (such as for example, Lasker-Maas rules) end up with three points for black in these position no matter who plays first.

The reason is that when black plays first, he has one less point of “normal” territory but he gets to play an additional extra dame, which unlike a normal true dame black can wait until the very end to create and so it works as a one sided dame, giving black one extra point of territory (if japanese counted one sided dames as actual territory, it would be one less difference between the Japanese and Chinese rules).

This means that black would have three points less by leaving it as seki. Which is indeed the true result we see when counting area: 4 stones vs 1 stones = 3 points for white initially, but 3 vs 3 = 0 net points after black (or white) plays the position.

I think that this paragraph is misleading, “mixing” so to speak different ways of counting. You can check that if you copy this position 10 times over the board, and play it out each time under area scoring (no matter who plays first), vs leave it as seki the 10 times, you will get 30 point difference, not 20 point difference.

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Also, the same three-territory-points can be observed when playing by AGA rules and territory-counting (thus, using passing stones): Since black gets the last dame in the line where black gets only two territory-points, white will pass first, and thus white will have to give a final extra passing-stone.

When the position is copied many times, if white does not want to play it out, black still can extract 3 points per position under AGA rules: black plays the first one out, gets 2 points playing the last dame, white PASSES (it is no use to play in another copy: that would directly give black the three points, and it would still be white’s turn), and now black starts playing out a different copy of the position. With this extra pass by white in each component when playing it out, white must give black an extra passing stone, making the total 3 points per copy of the position.

Basically, all rules give a net 3 points of territory to black here, except the modern 1989 Japanese rules :slight_smile:

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I see. Under area scoring, black’s capture loses sente and white would theoretically gain an opportunity to take an extra dame point.

So correct play under area scoring is for black to delay capture until there are no more dame points left (so losing sente does not lose points). Somewhat similar to playing dame before filling the last 0.5 point ko when you have a surplus of ko threats.

Interesting!

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The following is a problem that I composed, as part of studying special situations under Japanese rules (so, this should already be a “hint” at the solution :wink: ).

Japanese rules. 0.5 komi for white. Assume that no captures have been made. Black to play. What is the end result assuming perfect play by both players?

Hint (partial spoiler)

“White wins” is the wrong answer.

Solution (spoiler)

With perfect play by both, the game ends with No Result. I’ll probably add a detailed explanation later.

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