Capturing bulky fives


#1

So I’m a little confused about the rules regarding dead shapes. For example the bulky five below is dead:
bulky%20five
So at the end of the game, the black stone should be removed, which results in 22 points for white (9 prisoners + 13 territory)

However, if white were to play out the sequence of actually capturing the stones, we get a different result
BulkyFive
Namely, black can capture 10 of white’s stones in the process, so the result is only 16 points (13 black prisoners + 13 territory - 10 white prisoners).

What is this dead group actually worth? Does this vary under different rule sets?


Question about scoring
#2

Start with Chinese rules in your head. That’s how it began. They are dead and it makes no difference to the score if that needs to be demonstrated by actual play.
Then some bright spark notices that when the same number of stones has been played by both sides, it’s easier to just count the open spaces. Especially for estimating the score before the game ends. After that almost all the special rules about what is automatically dead are designed to prevent score distortion under the ‘new’ scoring method. So under Japanese rules it has to be ruled dead to avoid the problem you have demonstrated.

ps. Same score under both rule sets. All rule sets as far as I know.


#3

Under Japanese rules (or any rules I know actually) you are NOT required to actually capture dead stones.

If that was the case, then all you had to do to win under Japanese would be to keep throwing sones into opponents territory forcing him to fill 4 points to capture. This is the same case, just slightly more complicated :slight_smile:

This should still be obvious to both sides that the group is dead, but if there ever was a disagreement under japanese rules you should decide it on a separate board and then count from the original position where the game ended.
(or for simplicity you can just say both player have to make a local move, or give the other player a prisoner if they do not want to make a move…)


#4

Both are correct. This shows why White shouldn’t bother putting stones in there to prove death…the capture of more stones invested by white then the number of black stones results in a net loss for white.

So, I guess this would be a question of black disputing and forcing a play thru…but, if black is challenging, then black should bear the burden of proving it by moving next, not white. If black and white have equal exchanges, it would no longer be a net loss in value for white.


#5

Thanks, it does make a lot of sense, both the Japanese and the Chinese rules.

I feel the Chinese rules are more robust to this kind of situations, whereas the Japanese rules feel more intuitive to me, and are more clear about the reason not to play in your own territory.


#6

But forcing black to move first could be the reason of black’s death, for example if black is convinced the position is seki, while white is convinced the black group is dead.


#7

True. In the case of black claiming seki, white could play first and then the burden is on black again to prove that white would die. A real seki tends to be whoever moves first, dies, so if black thought it was seki, they should follow up after a white move to prove that white made a mistake.

So I guess if after white playing one move, and if black decided they were in the wrong and didn’t follow up, white will have lost a point, per Japanese rules…? Which brings us back to your point…

AGA rules says: “In principle, resolving such end-of-game disputes requires the players–or some competent authority in attendance–to have the capacity to resolve life-and-death problems of arbitrary complexity!”

https://www.cs.cmu.edu/~wjh/go/rules/AGA.commentary.html

So, call a ref, I guess? :smiley: In a friendly match, I like AdamR’s suggestion of working out on a separate play area.

Thank goodness this is usually just a theoretical scenario…commonly disputing board position outside of gameplay would be exhausting…to me at least. Maybe a thrill for others…? :slight_smile:


#8

Well, per Japanese rules, white does not lose any points, since the end position will remain unchanged even after playing out debatable positions. (“Resolving disputes about life and death or protective plays depends upon hypothetical play with special ko rules”, as is written in senseis)

And you’re right in that it is a theoretical scenario, but as someone who studies mathematics, that’s one of my pleasures in Go: the weird mathematical anomalies that are technically possible, but probably never happen.


#9

Under japanese rules as used in europe. Extreme solution for disagreement about life and death is that the board is copied and the death of the group is proved by capturing. under AGA I believe opponent gets extra prisoner for every pass to solve this problem.


#10

Out of curiosity. What software did you use to create the capturing animation?


#11

Sabaki for the goban, and LICEcap for the gif


#12

Off-topic FYI re: creation of animated GIF from SGF

This Chrome/Firefox/Opera extension can export animated GIF from SGF files:

https://addons.mozilla.org/en-US/firefox/addon/web-gobaduk-board/
(sadly not compatible w/ Firefox Quantum)