6

In a game, the following board position remained after both parties passed:

$$ -----------
$$ .XO.X.X.OX.
$$ .XO.....OX.
$$ .XOOOOOOOX.
$$ .XXXXXXXXX.
$$ ...........

In the post game analysis it turned out that

  • Black on the move can create a seki by connecting her two stones inside the white group
  • White on the move can create a ko to prohibit the Seki. When black wins the ko, the result is a seki.
$$W
$$ -----------
$$ .XO4X1X6OX.
$$ .XO.325.OX.
$$ .XOOOOOOOX.
$$ .XXXXXXXXX.
$$ ...........

White takes the ko first with 7.

But the situation was left as it is on the board, how is it counted (under Japanese rules or European rules)? When playing resumes, who has the first move? Do ko threats on the board count?

4

I will only discuss the Japanese pro rules, since as far as I know there are no official European rules. The tournament of the European Go Congress 2015, for example, was played with AGA rules. I think most European tournaments are played with "Verbal European-Japanese Rules" which usually require to fill all dame points and kos before the end of the game. Then I think the position would be counted as a Seki by the referee.


Senseis claims that these are the official Japanese pro rules in a translation of James Davies.

Two paragraphs are relevant for the question:

9.2 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."

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

and

13.1 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.


As you already noted the best B can get is a Seki and the best W can get is killing the black stones. Therefore the only interesting situation is when B wins in case of the Seki and W wins if W can kill. Then it is important which player has more ko threats, though most likely the kos where already played as the situation appeared after both players passed.

My interpretation is the following:

  • B has more ko threats: B claims resumption according to Article 9.3 and W plays first. W can play the ko but cannot win it. B wins.
  • W has more ko threats or no ko threats: B does not want to resume the match since B will lose the ko. In the case of no ko threats W takes first and B looses the ko as well. W does not want to resume the match since it would be B's turn and B will complete the Seki which results in a loss of W. Thus both players lose according to Article 13.1

On Senseis you can also find commentaries on these rules pointing out some ambiguities around these Articles and adding interpretation.

Edit: One of the comments there is this one which I think clarifies that the position in the question would result in a loss of both players. The relevant paragraph is §13 - Interpretation of the Rules of Play. The example there is similar to the position in the question. The point is that both players will agree that there is an effective move. Therefore Article 13.1 is to be used. W cannot claim that the stones are dead as long as this effective move exists. It is not important that this move will not be played as no player will ask for resumption.

  • How does the resumption of 9.3 interact with the double loss of 13.1? It now seems as if resumption is always pointless as both players will automatically lose by 13.1. Surely that cannot be right? – hkBst Jun 19 '16 at 10:48
  • After reading through the rulesets and their commentaries, I am struck again: When black asks for resumption of play, White moves first, captures the ko first, Black has to pass on the ko, so White can secure it no matter how many ko threats are on the board. When White asks for the resumption of play, Black secures the seki. But when noone asks for resumption of play, both players loose? Or can White claim that the white string is alive and the two black stones are dead, because the sequence 1-7 proves that? – jknappen Jun 21 '16 at 10:03
  • @jknappen To your first question: I don't see why black passes on the ko? – havogt Jun 21 '16 at 12:08
  • @jknappen: To your second question I will expand my interpretation but let me say first that I am not an expert for these rules, I just found the question interesting and tried to answer them by gathering available material. In my matches I would resolve the situation as explained in the beginning: fill all dame and kos and it would be seki. – havogt Jun 21 '16 at 12:09
  • According to the Japanese pro rules is has to pass on the ko once before it is allowed to take it back–at least this is my understanding from reading them here cs.cmu.edu/~wjh/go/rules/Japanese.html . This makes sense to keep the evaluation of the position local. – jknappen Jun 21 '16 at 12:14

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