Asbjxrn, One thing that leaps out to me performance-wise is the 3 nested loops (dotimes, dotimes, loop/recur). Whatever's inside the inner loop is getting run a lot of times! General advice about reducing loop depth and computation required inside the innermost loop aside... have you looked at clojure.parallel? Seems like it might be a good fit since your algorithm is doing a lot of array processing...
-Greg On Jan 14, 11:27 am, Asbjørn Bjørnstad <asbj...@gmail.com> wrote: > I'm not complaining, but I find the topic interesting as I just tried > translating a fluid dynamics algorithm to clojure. > (http://www.dgp.toronto.edu/people/stam/reality/Research/pdf/ > GDC03.pdf) > I got no experience with this kind of stuff, it's just something I > tried out for fun. So the performance I get may be as expected. Or > there may be obvious ways of speeding it up that I don't see. > > Anyway, here is a core part of the algorithm. It's a diffusion > step, this gets called 3 times and in total this takes up more than > one second of cpu time on my machine which makes framerates very > slow. If anyone got any improvements I'd be happy to hear about it: > > (def grid-size 300) > > (defn make-grid [] > (make-array Float/TYPE (* (+ grid-size 2) > (+ grid-size 2)))) > > (defn diffuse [grid diff-ratio dt] > (let [a (float (* dt diff-ratio grid-size grid-size)) > a4-1 (float (+ 1 (* 4 a))) > grid #^floats (deref grid) > diffused-grid #^floats (make-grid) > line-length (int (+ grid-size 2))] > (dotimes [n 20] > (dotimes [y grid-size] > (let [line-offset (* (inc y) line-length)] > (loop [x (int 1) > c (+ x line-offset)] > (aset diffused-grid c > (float (/ (+ (aget grid c) > (* a > (+ (+ (aget diffused-grid (dec > c)) > (aget diffused-grid (inc > c))) > (+ (aget diffused-grid (- c > line-length)) > (aget diffused-grid (+ c > line-length)))))) > a4-1))) > (when (< x grid-size) > (recur (inc x) > (inc c))))))) > diffused-grid)) > > (def foo (ref (make-grid))) > > (time (diffuse foo 0.00025 0.002)) > > -- > -asbjxrn --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
