does java.security.SecureRandom have the same problem?
I have been using it for evolutionary algorithms, but have noticed
bottlenecks (likely mostly because my fitness evaluations are
computationally expensive).
You can implement it as such:
(import '(java.security SecureRandom))
(defn srand
"Returns a random floating point number between 0 (inclusive) and n
(default 1) (exclusive)."
([]
(let [sr (SecureRandom/getInstance "SHA1PRNG")]
(.nextDouble sr)
)
)
([n] (* n (srand))))
(defn srand-int
"Returns a random integer between 0 (inclusive) and n (exclusive)."
[n] (int (srand n)))
then just replace rand-int with srand-int
Scott
On Mar 25, 10:35 pm, 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/
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