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Michi – 15×15 ~6k KGS in 540 lines of Python code

March 25th, 2015 Leave a comment Go to comments

So what’s the strongest program you can make with minimum effort and code size while keeping maximum clarity? Chess programers were exploring this for long time, e.g. with Sunfish, and that inspired me to try out something similar in Go over a few evening recently:

https://github.com/pasky/michi

Unfortunately, Chess rules are perhaps more complicated for humans, but much easier to play for computers! So the code is longer and more complicated than Sunfish, but hopefully it is still possible to understand it for a Computer Go newbie over a few hours. I will welcome any feedback and/or pull requests.

Contrary to other minimalistic UCT Go players, I wanted to create a program that actually plays reasonably. It can beat many beginners and on 15×15 fares about even with GNUGo; even on 19×19, it can win about 20% of its games with GNUGo on a beefier machine. Based on my observations, the limiting factor is time – Python is sloooow and a faster language with the exact same algorithm should be able to speed this up at least 5x, which should mean at least two ranks level-up. I attempt to leave the code also as my legacy, not sure if I’ll ever get back to Pachi – these parts of a Computer Go program I consider most essential. The biggest code omission wrt. strength is probably lack of 2-liberty semeai reading and more sophisticated self-atari detection.

P.S.: 6k KGS estimate has been based on playtesting against GNUGo over 40-60 games – winrate is about 50% with 4000 playouts/move. Best I can do… But you can connect the program itself to KGS too:

http://www.gokgs.com/gameArchives.jsp?user=michibot

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