What is Go?

Go is a 4000-year-old board game that originated in China. It’s played on a 19x19 board, and the two players take turns placing stones in an effort to surround territory. The game is often known as igo in Japan, as wei ch'i in China, and as baduk in Korea. To learn more about the history and rules of the game, you can check out Wikipedia or the web site of the American Go Association. Or learn to play Go interactively at The Interactive Way To Go. Or explore links to other interesting web sites about Go and computer Go.

Rules

Go is played on a 19x19 board with black and white stones. The game starts with the empty board; the object of the game is to control more board points than the opponent at the end of the game. Black plays first; the players move alternately by placing a stone of their color on an empty point. Once played, stones are never moved, but they may be captured if they're completely surrounded by opponent stones.

You're not allowed to repeat previous positions; the rule of Ko prohibits you from playing a move that would cause the position to be repeated.

A player can pass at any time; the game ends when both players pass. The occupied points as well as the points completely surrounded by a player count as territory; the player with most territory wins the game. There are small differences in how special situations are scored, but there's no need to worry about that while you're learning the game.

Computer Go

Unlike chess, computer programs playing Go still have a long way to go. Their current level of play is somewhere between 5 and 10 kyu (weak amateur play), with the playing strength dropping significantly as you learn the weaknesses of a particular program.

Writing a strong Go program is one of the most challenging and exciting problems in computer science. It’s a well-defined problem, expert knowledge is readily available, progress is clearly measurable, and yet programs are still weak. If we can’t make progress on such a clear-cut problem, how can we trust computers to excel in other domains?

Part of the challenge is that the approach that worked so well in computer chess doesn’t work in Go. Brute force search worked well for chess thanks to a relatively simple evaluation function combined with a limited number of moves at every turn. In Go, the average number of legal moves is 200 rather than 38, and there’s no simple evaluation function. Also, the visual nature of Go helps humans more than computers. However, while brute force can’t be applied directly, we think some of the lessons learned from chess can be applied to Go.

What is Go?

Rules

Computer Go

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