As others have pointed out using per-thread java.util.Random objects is probably the best way to go in this particular case. However, I'm curious if the following code could give any speed gain on your machine:
(defn rand-seq [] (repeatedly #(. Math (random)))) (def rand-seq-ref (ref (rand-seq))) (nth @rand-seq-ref 100) ;; pre-cache random values; evaluate it every some time ;;btw, how to do it automatically? (defn next-rand-val [] (dosync (commute rand-seq-ref next) (first @rand-seq-ref))) user=> (next-random-val) 0.5558267606843464 user=> (next-random-val) 0.32353157456467474 Cheers, Andrzej On Fri, Mar 26, 2010 at 11:35 AM, Lee Spector <[email protected]> wrote: > > I'm trying to track down the reason that I sometimes see a lot of concurrency > in my system (up to 1200% CPU utilization on a dual quadcore mac that also > has some kind of hyperthreading, allegedly allowing a maximum of 1600% CPU) > while other times it gets stuck at around 100-200%. My system (a genetic > programming system) has a *lot* of randomness in it, so it's hard to repeat > runs and get a firm handle on what's going on. > > But after a bunch of testing I'm beginning to suspect that it might be the > random number generator itself (clojure-core/rand-int in this case, which > calls (. Math (random))). This seems at least somewhat plausible to me > because I guess that the underlying Java random method must be accessing and > updating a random number generator state, and so this would be a concurrency > bottleneck. So if I'm in a condition in which lots of concurrent threads are > all calling rand-int a lot then all of the accesses to the state have to be > serialized and my concurrency suffers (a lot). > > Does this sound plausible to you? If so, is there a straightforward way to > avoid it? It is not important to me that the random numbers being generated > in different threads be generated from the same generator or > coordinated/seeded in any way. I just need lots of numbers that are "random > enough." I guess I could roll my own random number generator(s) and either > have a lot of them with independent states or maybe even make them stateless > (always generating numbers by scrambling the clock?). But I would hope there > would be something simpler. > > Thanks, > > -Lee > > -- > Lee Spector, Professor of Computer Science > School of Cognitive Science, Hampshire College > 893 West Street, Amherst, MA 01002-3359 > [email protected], http://hampshire.edu/lspector/ > Phone: 413-559-5352, Fax: 413-559-5438 > > Check out Genetic Programming and Evolvable Machines: > http://www.springer.com/10710 - http://gpemjournal.blogspot.com/ -- You received this message because you are subscribed to the Google Groups "Clojure" group. To post to this group, send email to [email protected] Note that posts from new members are moderated - please be patient with your first post. To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/clojure?hl=en To unsubscribe from this group, send email to clojure+unsubscribegooglegroups.com or reply to this email with the words "REMOVE ME" as the subject.
