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11 votes
Accepted

What's the longest possible forced repetition in Go?

Molasses ko: http://denisfeldmann.fr/bestiary3.htm#mol "The semeai in figure 11 is probably the worst known case of repetition. Known as "molasses ko", ..." Denis Feldmann's Go Bestiary is a ...
Olivier Dulac's user avatar
10 votes
Accepted

Why do asymmetric ko fights exist?

I think the easiest way to think of this is in terms of options, and the freedom to take whatever options benefit me. In your example, you have no options: You need to win this ko, or you will lose. ...
goldPseudo's user avatar
  • 6,682
8 votes
Accepted

Is this a correct formal heuristic for invalid moves due to Ko?

No, this logic unfortunately doesn't work: It prevents moves that are in fact legal, because they include a snapback. $$ white to play $$ . . . . . . . $$ . . X O X . . $$ . X O X . X . $$ . X O O O ...
balpha's user avatar
  • 597
4 votes
Accepted

Does playing a ko add a dimension to the game?

"Ko" is effectively one of those situations where you can hope to get two moves in a row (e.g. if your opponent spends his next move filling, or otherwise removing the ko). On the other hand, if your ...
Tom Au's user avatar
  • 22.1k
3 votes

Is this double ko played reasonably by AlphaGo Zero and AlphaGo Lee?

There is a difference between the two semi-stable double ko positions, although a rather small one. C14 reduces the immediate number of liberties of the G13 leg. This means that black will have a free ...
Stéphane Gimenez's user avatar
2 votes

Does playing a ko add a dimension to the game?

I would say the added dimension comes from the "long-range" nature of kos. It is possible, through a ko, for two, otherwise loosely linked regions to be directly compared. Each ko evaluates the entire ...
Shape's user avatar
  • 121
2 votes
Accepted

How to apply the ko rule (Go)

The theoretical answer depends whose rules you are using, because different countries use different rules, and have different ways of dealing with the multi-ko1 situation you describe. In practice ...
PJTraill's user avatar
  • 1,438
2 votes

How to apply the ko rule (Go)

Super Ko can be detected efficiently using Zobrist hashing. https://en.wikipedia.org/wiki/Zobrist_hashing https://www.gnu.org/software/gnugo/gnugo_11.html#SEC144 The idea is to pick a random 64-bit ...
satnhak's user avatar
  • 321
2 votes

Is this a correct formal heuristic for invalid moves due to Ko?

Your rule is adequate to detect simple kos but not all forbidden repetitions. EDIT: It incorrectly forbids snapbacks, as observed in balpha’s answer, and thus fails your condition (2). It is unclear ...
PJTraill's user avatar
  • 1,438
1 vote

Why do asymmetric ko fights exist?

Short answer How can a ko fight be “asymmetric”? By offering one player a strong incentive to start it. When a ko is asymmetric You are right that once the ko is started, the result is equally ...
PJTraill's user avatar
  • 1,438

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