Some would also argue that any parallelism system is going to slow down code as trivial as this. Never underestimate the power of properly optimized single threaded code :-).
But yes, futures are the way to go if you want to execute a given expression on a different thread. On Thu, Apr 10, 2014 at 8:45 AM, Andy Fingerhut <andy.finger...@gmail.com>wrote: > Forcing small bits of computation to be done in parallel using the tools > Clojure and the JVM have at hand, e.g. pmap, future, etc., which rely on > creating JVM Thread objects, tends to slow things down rather than speed > things up, because the extra overhead of creating threads and waiting for > them to finish is higher than the cost of sequentially doing the small bits > of computation. > > If you want to force parallelism in your example anyway, to compare the > most-likely-slower-performance against what you have now, you can try this: > > (let [val (Math/sqrt i) > a1 (future (Math/pow val 2)) > a2 (future (* val val)) > diff (Math/abs (- @a1 @a2))] > > Andy > > > On Thu, Apr 10, 2014 at 7:35 AM, Cecil Westerhof > <cldwester...@gmail.com>wrote: > >> I have the following in my code: >> (let [val (Math/sqrt i) >> diff (Math/abs (- (Math/pow val 2) (* val val)))] >> >> I expect that calculating the difference is the most expensive part of my >> code. I understood that Clojure is very good in parallellisation. How would >> I let (Math/pow val 2) and (* val val) be calculated in parallel? >> >> -- >> Cecil Westerhof >> >> -- >> 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. > -- "One of the main causes of the fall of the Roman Empire was that-lacking zero-they had no way to indicate successful termination of their C programs." (Robert Firth) -- 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.
