Re: [gnugo-devel] Making GNU Go take advantage of multiple processors.

[Gunnar Farnebäck]

Dmitry Denisenko wrote:
> I'm a graduate student taking a course in parallel computer architecture 
> and programming and I'm looking for a program to parallelize. I noticed 
> that making GNU Go thread-safe is on your wish list. Have there been 
> previous attempts at making it parallel?

Not quite, but in that direction. There's an old branch to allow working 
with multiple boards at once, which would be a step towards parallelization.

> Are there any obvious reasons why it might be very hard (e.g. very large
> number of static variables in the program) or nobody just had time to 
do it?

Yes, there are lots of global and static variables, reading caches that 
should be shared between threads somehow, and of course the fact that 
there is a single global board state. Moreover it's not at all clear 
what tasks should be parallelized and how.

However, there's a strong trend towards using Monte-Carlo simulations in 
computer go, which is a technique where parallelization is reasonably 
straightforward and clearly beneficial. This has not been included in 
GNU Go yet, but you can get an idea how it may look from 
http://trac.gnugo.org/gnugo/ticket/150

There a different (simpler) board representation is used, which is 
designed from the start as a self-contained struct and all functions are 
intended to be thread-safe. Parallelization should probably be done with 
a shared UCT tree and a number of working threads to play out 
simulations from the leaves of the tree.

/Gunnar