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.
