Hi,
This may be silly, but I tried to code a simmulated annealing method to solve the travelling salesman prblem, by adapting the algorithm described in "Numerical Recipes in C".
Doesn't seem silly so far! :-)
The problem is that there are so many iterations, that the program gets killed (kill -9) by the system.
I'm not sure what you mean here - I've never encountered a system that kills processes with -9, other than at shutdown time. Are you sure it's -9? How do you know it's because there are too many iterations?
I use the State monad to code the optimisation algorithm, and a simple configurations generator for generating the each path. After profiling with -hc, the heap profile shows that the top-level function of the algorithm uses about 40Mb of heap space.
That sounds fine to me - I have plenty of programs that use well over 100MB of heap. How much memory do you have? (you say later that it eats up all the available space - I find it hard to believe 40MB is all you have!).
How can I improve this awful program?
You probably have a space leak. This is usually caused by p or f not forcing the evaluation of all of m0. Since the next m0 depends on the previous one, and so on, this causes all values of m0 to be held in the heap until the end of the program. Add strictness annotations in the right places[*] until heap usage is constant, rather than increasing with each iteration.
untilM :: (Monad m) => (m a -> m Bool) -> (a -> m a) -> m a -> m a untilM p f m0 = do isOver <- p m0 if isOver then m0 else untilM p f (m0 >>= f)
[*] of course, this is an entirely non-trivial task, and involves art as well as skill... Hope this helps. Cheers, --KW 8-)