In that case isn't context switching dominating your test? .isArray isn't expensive enough to warrant the use of pmap
Leonardo Borges www.leonardoborges.com On Dec 29, 2012 10:29 AM, "cameron" <cdor...@gmail.com> wrote: > Hi Lee, > I've done some more digging and seem to have found the root of the > problem, > it seems that java native methods are much slower when called in parallel. > The following code illustrates the problem: > > (letfn [(time-native [f] > (let [c (class [])] > (time (dorun (f > (fn [_] (.isArray c)) > (range 10000000))))))] > (println "Sequential Test:") > (time-native map) > (println "Parallel Test:") > (time-native pmap)) > > On a dual quad-core xeon box I get the following results: > Sequential Test: > "Elapsed time: 1054.807725 msecs" > Parallel Test: > "Elapsed time: 15302.605697 msecs" > > ie. the code executed in parallel was 15 times slower than the sequential > version. > The same can be seen with isInstance and isArray members of > java.lang.Class. > > I'm not sure where to go from here, these functions are frequently used by > clojure.core > Perhaps someone with more JVM implementation knowledge can help? > > Cameron. > > -- > 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 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
