Do Japanese Rules ( or their KGS implementation ) suck ?

[Cassandra]

For this, you need to define "local", of course.

I suppose that it is this need, together with some recursive elements needed to combine the single chains status results, that makes implementation so difficult.

This problem with "local" may be one reason, why Monte-Carlo-based programs are weeker in Semeai, compared to their overall performance.

[wms]

Japanese rules have a local view on status evaluation, there is no room to "play something out using the whole board" after the end of "play". The sole and only question to answer during status evaluation is "Can this one and only one chain of stones be taken of the board ?" for each chain of stones on the board separately.

It seems, then, that a server that implements "japanese rules", but does not implement such an analysis, actually has an incomplete rule set. In other words, one should not rely on the players to reach agreement through informal communication (as this only works when the players are sufficiently experienced), but, in the case of a dispute, start an analysis phase for each disputed string, probably with infinite takebacks. For this, you need to define "local", of course.

The problem is that for the server to all on its own determine life/death is about as hard as creating a perfect go player. And having the server step the users through the resolution at the end of the game is incredibly complicated; it is usually newer players who need it, and explaining how the system works is way, way too complex for anybody but a rules expert to use. The old cgoban 1 app had such a system, but I threw it out when I went to cgoban 2 because it was worthless - anybody who knew enough to step through the system would know at a glance that bent 4 was dead so it was just an ugly confusing trap for people to accidentally turn on.

[jts]

When people say that bent four in the corner is automatically dead under Japanese rules, what exactly do they mean? Japanese rules don't prevent you from playing out the ko, right? And if they don't prevent you from playing out the ko, what's the point of saying they're automatically dead? What could you do at the end of the game, other than play out the ko?

[oren]

When people say that bent four in the corner is automatically dead under Japanese rules, what exactly do they mean? Japanese rules don't prevent you from playing out the ko, right? And if they don't prevent you from playing out the ko, what's the point of saying they're automatically dead? What could you do at the end of the game, other than play out the ko?

This may help
http://www.cs.cmu.edu/~wjh/go/rules/Japanese.html

Life-and-Death Example 7-1: Bent Four in the Corner

[jts]

When people say that bent four in the corner is automatically dead under Japanese rules, what exactly do they mean? Japanese rules don't prevent you from playing out the ko, right? And if they don't prevent you from playing out the ko, what's the point of saying they're automatically dead? What could you do at the end of the game, other than play out the ko?

This may help
http://www.cs.cmu.edu/~wjh/go/rules/Japanese.html

Life-and-Death Example 7-1: Bent Four in the Corner

So in other words "automatically dead" means "after two passes, it's dead"?

[Dusk Eagle]

This is a bent-four position in this context:

$$Wc
$$ ---------------------------------------
$$ | O O O X O . . . . . . . . . . . . . . |
$$ | a X . X O . . . . . . . . . . . . . . |
$$ | X X X X O . . . . . . . . . . . . . . |
$$ | X O . O . O . . . , . . . . . , . . . |
$$ | O O . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |

Click Here To Show Diagram Code

[go]$$Wc
$$ ---------------------------------------
$$ | O O O X O . . . . . . . . . . . . . . |
$$ | a X . X O . . . . . . . . . . . . . . |
$$ | X X X X O . . . . . . . . . . . . . . |
$$ | X O . O . O . . . , . . . . . , . . . |
$$ | O O . O . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |[/go]

If we were to determine its status based on whole-board play, white could first remove all his ko threats one at a time and then remove all of black's external liberties, then play at 'a'. Note that black cannot prevent white from playing at 'a' without killing himself. So after white plays 'a', a ko starts after black captures and white plays B19, with black having to find the first ko threat. However, black will have no ko threats, as white has removed them all. So in Japanese rules, this shape is dead as it stands.

[flOvermind]

For this, you need to define "local", of course.

That's easy. For each disputed group, play out the situation on the whole board. When the group gets captured, it's dead. When it can't be captured, it's alive. Then, restore the board to the original position and remove the dead group.

That way, you can theoretically lose every other group on the board, as long as the disputed group stays alive. Also, when you look at it in that way, it becomes clear why in the hypothetical play phase of Japanese rules, only a pass is considered a valid ko threat. That rule, by the way, is also the real reason why bent four is dead in Japanese rules

[Cassandra]

... in the hypothetical play phase of Japanese rules, only a pass is considered a valid ko threat. That rule, by the way, is also the real reason why bent four is dead in Japanese rules

Unfortunately, it is not so simple.

$$W
$$ ----------------
$$ | O O O . X W C
$$ | . X X X X W C
$$ | X X W W W W C
$$ | W W W C C C C
$$ | C C C C C C C

Click Here To Show Diagram Code

[go]$$W
$$ ----------------
$$ | O O O . X W C
$$ | . X X X X W C
$$ | X X W W W W C
$$ | W W W C C C C
$$ | C C C C C C C[/go]

The 7.1-example of Nihon Kiin 1989 (with changed colors) assumes that White's outside group is alive, not showing the content of the circled area.

There are later examples, in which Bent-Four is alive in Seki or even alive with territory. This is due to the existence of some "local" Ko-treats.

Any unconditionally alive group (i. e. with two eyes) borders "local". No move beyond these "borders" does have any effect on the evaluation of life and death.

$$W
$$ --------------------
$$ | O O O . X O . O C
$$ | . X X X X O O O C
$$ | X X O O O O . O C
$$ | O O O C C O O O C
$$ | C C C C C C C C C

Click Here To Show Diagram Code

[go]$$W
$$ --------------------
$$ | O O O . X O . O C
$$ | . X X X X O O O C
$$ | X X O O O O . O C
$$ | O O O C C O O O C
$$ | C C C C C C C C C[/go]

Giving the outside group 2 eyes would have been better. Now it is really uninteresting, how the circled area looks like.

$$W
$$ --------------------
$$ | O O O 2 X O . O .
$$ | 1 X X X X O O O .
$$ | X X O O O O . O .
$$ | O O O . . O O O .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$W
$$ --------------------
$$ | O O O 2 X O . O .
$$ | 1 X X X X O O O .
$$ | X X O O O O . O .
$$ | O O O . . O O O .
$$ | . . . . . . . . .[/go]

White can take Black's stones off the board, ...

$$W
$$ --------------------
$$ | 4 3 7 X X O . O .
$$ | 5 X X X X O O O .
$$ | X X O O O O . O .
$$ | O O O . . O O O .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$W
$$ --------------------
$$ | 4 3 7 X X O . O .
$$ | 5 X X X X O O O .
$$ | X X O O O O . O .
$$ | O O O . . O O O .
$$ | . . . . . . . . .[/go]

6 = Pass or Tenuki
... independent from what happens in the rest of the board

$$W
$$ --------------------
$$ | W W W . Z W . W .
$$ | . Z Z Z Z W W W .
$$ | Z Z W W W W . W .
$$ | W W W . . W W W .
$$ | . . . . . . . . .

Click Here To Show Diagram Code

[go]$$W
$$ --------------------
$$ | W W W . Z W . W .
$$ | . Z Z Z Z W W W .
$$ | Z Z W W W W . W .
$$ | W W W . . W W W .
$$ | . . . . . . . . .[/go]

Returning to the original position, we have Black stones, which can be captured, between White stones, which cannot be captured (= are said to be "alive"). Concluding, Black's group is dead as it stands.


As you have written already, status assessment does not change the score (so it does not matter, if something may have been captured in the process). The results "cannot be captured" / "can be captured" are combined using the original position after the end of "play".

[RobertJasiek]

wms, after the filling of all teire, providing "having the server step the users through the resolution at the end of the game" is incredibly easy (not complicated, as you think) if you base it on the players' agreement:

1) Pressing Done invokes scoring iff both players have pressed Done successively without any intervening marking of a string or Undo.

2) Undo during the agreement phase requires the opponent's confirmation.

3) Optional: When a string is being marked, automatically mark also all same-coloured strings within the same empty-or-same-colour-string-region.


Kirk, with fake false sekis eyes I refer to a circular shape like in http://home.snafu.de/jasiek/j_verbal_status.pdf


Cassandra, repeating "Japanese style rules do not have global play in analysis" many times does not make it correct. - What is being analysed is local with respect to strings. How it is being analysed allows for global play.


jts, bent-4 belongs to the rules forum. In short, different Japanese rulesets treat it differently.

[Cassandra]

Cassandra, repeating "Japanese style rules do not have global play in analysis" many times does not make it correct. - What is being analysed is local with respect to strings. How it is being analysed allows for global play.

It's just a matter of taste. And doesn't really matter.

You cannot win a Semeai with moves, which are too far away. You have to play near by (= "local"), so that your moves can have an effect on the Semeai.

It may be possible that you receive compensation elsewhere on the board, when playing non-local, may be that you even win in this kind of exchange, because your moves gain more than those of your opponent. But you will not win the Semeai.

So the view on a Semeai is "local", not "global". It is possible to exclude part of the board from it's investigation.

The same is true for the status evaluation (typical Japanese style) of a single string of stones.

[RobertJasiek]

Under Japanese rules, it is not a matter of taste but (subject to ko rules etc.) a matter of the rules that global play is allowed.

[Cassandra]

Under Japanese rules, it is not a matter of taste but (subject to ko rules etc.) a matter of the rules that global play is allowed.

I hadn't stressed that any legal move might be forbidden.

Non-local moves do not have any effect on status evaluation or Semeai. You may even pass instead.

[RobertJasiek]

Cassandra, if you want to discuss (allegedly missing) effects of local moves, let's do it in the rules forum.