Slowdowns wrt math are caused mainly by boxing and range check, see this thread [1]
[1] https://groups.google.com/d/msg/clojure/kcx5eKdMxcs/Wy4_IHrSEaMJ Jozef On Wednesday, October 15, 2014 9:53:40 PM UTC+2, Jony Hudson wrote: > > Hi all, > > another performance question ... this time about arithmetic on vectors > :-) Let's say I have two vectors of numbers (specifically, things with type > clojure.lang.PersistentVector, containing things of type java.lang.Double). > And let's say I want to sum the differences [1] between corresponding > elements of the lists i.e. (a1 - b1) + (a2 - b2) + ... > > Any suggestions on how to do this quickly. What I find is that if I use > the 'obvious' high-level construction: > > (reduce + (mapv #(- %1 %2) a b)) > > > then it goes pretty slowly. On my laptop I measure about 180us for 1000 > element lists. > > If I try using `loop`: > > (loop [sum 0.0 i 0] > (if (< i 1000) > (recur (+ sum (- (nth a i) (nth b i))) (inc i)) > sum)) > > it does better, at about 100us. > > But these are still a ways off what I might think is the best that could > be done. If I run a similar computation in Java, it takes about 8us, which > ties up with what my gut feeling would be. > > So ... does anyone have any advice on closing the gap here? > > Thanks in advance, again, > > > Jony > > > [1] Actually I want to sum the absolute differences, but that brings in > java interop which I want to leave out lest it confuse matters. > -- 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/d/optout.
