I should add, "oops, ignore what I wrote". :) see:
https://groups.google.com/group/clojure/tree/browse_frm/thread/33366bccc6df7756/415072576d83b757?rnum=11&_done=%2Fgroup%2Fclojure%2Fbrowse_frm%2Fthread%2F33366bccc6df7756%3F#doc_0d0a3759a0a10328 Carson On Jul 17, 3:58 pm, Carson <c.sci.b...@gmail.com> wrote: > Hi, Try this: > > (defn stationary-convolve [n fs gs] > (let [window-size (count fs) > padding (repeat window-size 0) > padded-gs (concat padding gs padding) > new-center (+ n window-size) > window-of-gs (subvec (vec padded-gs) > (- (inc new-center) window-size) > (inc new-center)) > reverse-window-fn (fn [i] (nth window-of-gs > (mod (- -1 i) > window-size))) > reverse-window (map reverse-window-fn (range 0 window-size))] > (reduce + (map * fs reverse-window)))) > > (defn convolve [fs gs] > (map #(stationary-convolve % fs gs) > (range 0 (+ (count fs) (count gs))))) > > (let [xs (for [i (range 1000000)] (rand 100)) > ys (for [i (range 1000000)] (rand 100))] > (time (dotimes [_ 3] (convolve xs ys)))) > > "Elapsed time: 2540.967482 msecs" > > Seems to run pretty fast and seems to be the kind of convolution you > want. > > Thanks for the interesting problem! > > Carson > > On Jul 16, 12:57 pm, Isaac Hodes <iho...@mac.com> wrote: > > > I posted this on StackOverflow yesterday, but to no avail: I don't > > think many people looked at it, or least I didn't get much feedback. > > > I am trying to create a lazy/functional/efficient/Clojuresque function > > to carry out convolution on two lists/vectors of (ideally BigDecimals > > but that may be inefficient) doubles. > > > It is turning out to be very difficult. I have four or five versions > > in my buffer right now, and none of them are acceptable. I've even > > tried a number of versions using into-array etc, e.g. mutables. > > > Instead of posting a lot of links to pastie, I'm just copying the SO > > link here, where my code and the algorithms can be found. > > > Right now, it seems as though this is something Clojure cannot do. > > David Nolen mentioned that the appropriate Java-interop functionality > > may come in Clojure 1.3, but aside from eschewing the functional style > > by using arrays, it seems as though there should be a better answer. > > (As an aside, where can I find out about 1.3?) > > > I have a Python implementation to show how nicely it can be expressed > > in an imperitive language (though I suppose I dabbled in the > > functional style initializing my return array). > > > Is it possible to do this, and do it well? > > > Thank you so much, in advance. -- 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
