There are primitive vectors. Extraordinary clever. http://clojuredocs.org/clojure.core/vector-of
/Linus Den 16 okt 2014 00:02 skrev "Jony Hudson" <jonyepsi...@gmail.com>: > Thanks, that's really useful! > > > Jony > > > On Wednesday, 15 October 2014 20:53:40 UTC+1, 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. > -- 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.
