On Fri, Feb 18, 2011 at 7:03 AM, Daniel Werner <daniel.d.wer...@googlemail.com> wrote: > On Feb 16, 6:20 am, Nick <npatric...@gmail.com> wrote: >> (let [ newv1 (time (doall (map (fn [v u I] (+ ^java.lang.Double v (* >> 0.5 (+ (* (+ (* 0.04 ^java.lang.Double v) 5) ^java.lang.Double v) 140 >> (- ^java.lang.Double u) ^java.lang.Double I)))) v u I))) >> newv (time (doall (map (fn [v u I] (+ v (* 0.5 (+ (* (+ (* 0.04 v) >> 5) v) 140 (- u) I)))) newv1 u I)))] >> >> I've tried without type hints, with type hints, different ways of >> doing the type hints, but I cannot explain the results that I'm >> seeing. With all of the variations I've tried, I've always seen >> timing like this: >> >> "Elapsed time: 49.876243 msecs" >> "Elapsed time: 0.179701 msecs" >> >> What am I missing here? Is the compiler getting some advantage to >> executing the same function twice that cannot be gained in the first >> execution? > > Since nobody has replied so far: One explanation I could imagine is > that your type-hints in the first invocation force the compiler to use > object types for all the nitty-gritty calculations, whereas the second > invocation is able to use primitives for calculations, having to box > them only when the final sequence is produced.
Yes, that's exactly right. Some operators like + Clojure's compiler knows to inline and then they don't have to box primitives. The type hints force boxing in this case. -- 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
