# Questions tagged [ko]

The situation in go in which immediate recapture of a single stone is forbidden and one must therefore make a threat in order to be allowed to do so. This tag is definitely appropriate to questions about the principles and rules of kos and about a ko in a particular position. For positions that might lead to a ko and positions where a ko is a small part it is probably only useful if the ko plays a significant role.

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

In the 8th game of the series1 between AlphaGo Zero and AlphaGo Lee the following position with a double ko at {A,C}×{13,14} arises: On the next move AlphaGo Lee (Black) plays the double ko exchange ...
• 1,358
5 votes
2 answers
212 views

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

In the game of Go, there is the ko rule, which basically states that immediately recapturing a single stone is not a valid move. I am working on a Go computer program and am trying to implement the ...
• 6,972
12 votes
3 answers
351 views

### Why do asymmetric ko fights exist?

When I play teaching games with much stronger go players, situations often come up where one side must win a ko fight in order to survive. In these situations, my opponent will explain to me that ...
• 485
2 votes
2 answers
251 views

### Does playing a ko add a dimension to the game?

Playing a game of Baduk I was thinking that playing a Ko adds a dimension to the Tree of possibilities. Meaning it at least double the number of next moves the player may think of. Am I kind of right ...
• 475
9 votes
1 answer
285 views

### What's the longest possible forced repetition in Go?

Assume no superko rules so the game would end with no result. And both players are willing to play the shortest possible cycle as long as they don't give their opponent a chance to win. There are 4 ...
• 193
3 votes
1 answer
109 views

### Tsumego intermediate problem 11 - possible without winning ko two times?

This tsumego (intermediate problem 11) gave me hard time: I actually only found a solution where black must win the ko two times, which is nasty. Is there a better solution? It actually looks like "...
• 651
8 votes
4 answers
1k views

### How to apply the ko rule (Go)

I’m having trouble understanding how to apply the ko rule. For instance, in the description in Wikipedia, there is an example where the ko rule can potentially apply. But suppose there were two, or ...
• 183
8 votes
4 answers
646 views

### What happens in Go if you "take back" a ko before making a ko threat?

In Go, there is a potentially repetitive sequence of moves called a "ko." So if your opponent takes a ko from you, you have to make a move elsewhere on the board, called a ko threat, before "taking ...
• 21.8k
7 votes
2 answers
239 views

### Tsumego only solvable under NZ rules?

The most significant difference between the New Zealand rules and the other rules for Go is that suicide is not forbidden. In most cases, the only time this can come in handy is that you can suicide ...