Guys, thanks very much for the fast responses. Of course, this is an
unscientific and totally ad-hock benchmark. I am just *learning*
Clojure and functional programming and I wanted to get some feeling
of how fast Clojure is comparing to java when equivalent idioms are
used . Of course, loop and reduce are not really equivalent, but I
would use them for similar tasks, that 's why I wanted to compare them
(instead for example loop vs loop).
That's why it's great to hear those "duh" tips :)
On Jul 15, 5:39 pm, B Smith-Mannschott <bsmith.o...@gmail.com> wrote:
> On Wed, Jul 15, 2009 at 13:51, Dragan<draga...@gmail.com> wrote:
>
> > Hi,
>
> > I am trying to compare the performance of java loops to clojure reduce
> > function. Noting special, Since I am just learning.
> > Java code is something like:
>
> > [code]
> > long sum = 0;
> > for (int i = 1; i < 1000000; i++ ){
> > sum = sum + i;
> > }
> > [/code]
>
> > while in Clojure I used:
>
> > [code]
> > (reduce + (range 1 i))
> > [/code]
>
> > Execution time for the Java version is 7 ms, while Clojure needs 60 -
> > 160 ms.
> > Now, that is expected, since Clojure runs in REPL.
>
> Code run from the REPL won't run any slower (or faster) than code
> that's compile ahead of time. Clojure compiles all code to java
> classes before execution, regardless of how it is loaded.
>
> > Next, I tried the gen-class of the Clojure, and called that Class from
> > Java (so no REPL involved), but the code haven't speed up at all!
> > Am I missing something or such 10x performance penalty is usual for
> > such operations?
>
> You're probably seeing the cost of boxing the numbers and of using
> BigInteger to represent the sum. Being something of a newbie myself, I
> tried to speed up your code:
>
> (defn sum-of-range-1 [range-limit]
> (reduce + (range 1 range-limit)))
>
> When I ran (sum-of-range-1 1000000) one thousand times, it took 34.54
> s on my machine
>
> An explicit loop with some type hints is faster, though likely not as
> fast as Java:
>
> (defn sum-of-range-4 [range-limit]
> (loop [i (int 1) s (long 0)]
> (if (< i range-limit)
> (recur (inc i) (+ s i))
> s)))
>
> This took 20.275s for the same scenario.
>
> // Ben
>
> sum.clj
> < 1KViewDownload
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