I've been playing around with a generalised version of the N-Queens problem that handles other chess pieces. I have a Scala implementation that uses an eager depth-first search. Given enough RAM (around 12G - it's very memory hungry!) it can solve a 6x9 board with 6 pieces in around 2.5 minutes on my MacBook Pro.
I then created a Clojure version of the same algorithm with the intention of (eventually) using laziness to avoid the memory issue. However, the performance of the Clojure version is several orders of magnitude worse than the Scala version (I've left it running overnight on the problem that the Scala version solves in 2.5 minutes and it still hasn't completed). I'm struggling to see why the performance of the Clojure version is so much worse than the Scala. Profiling in YourKit suggests that it's spending 99% of its time in PersistentHashSet.cons, but I'm at a loss to explain why. I would be grateful for any insight. The code for the two different versions is on GitHub: https://github.com/paulbutcher/chess-scala https://github.com/paulbutcher/chess-clojure Notes: - I know that an exhaustive depth-first search isn't a great way to tackle this problem. But I'd like to understand why I see such a dramatic difference between the performance of the Scala and Clojure versions. - I believe that I've implemented the same algorithm in both Scala and Clojure - certainly they both generate the same results for small problems (there are 3x3 and 4x4 problems commented out in the source). But clearly I can't rule out the possibility that I've made a mistake in the Clojure implementation. If anyone can spot my stupid mistake, I'd greatly appreciate it. Thanks in advance for any insight that anyone can offer. -- paul.butcher->msgCount++ Snetterton, Castle Combe, Cadwell Park... Who says I have a one track mind? http://www.paulbutcher.com/ LinkedIn: http://www.linkedin.com/in/paulbutcher MSN: p...@paulbutcher.com AIM: paulrabutcher Skype: paulrabutcher -- -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to clojure@googlegroups.com Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to clojure+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/clojure?hl=en --- You received this message because you are subscribed to the Google Groups "Clojure" group. To unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
