yes, I started out trying the following example from Practical
Clojure:
(defn make-heavy [f]
(fn [& args]
(Thread/sleep 1000)
(apply f args)))
user=> (time (+ 5 5))
"Elapsed time: 0.06403 msecs"
10
user=> (time ((make-heavy +) 5 5))
"Elapsed time: 1000.622706 msecs"
10
user=> (time (doall (map (make-heavy inc) [1 2 3 4 5])))
"Elapsed time: 5003.314909 msecs"
(2 3 4 5 6)
user=> (time (doall (pmap (make-heavy inc) [1 2 3 4 5])))
"Elapsed time: 1000.720951 msecs"
(2 3 4 5 6)
in this case, pmap is faster.
On Nov 7, 3:25 am, André Thieme <[email protected]> wrote:
> Am 06.11.2010 12:57, schrieb philip schwarz:
>
>
>
>
>
>
>
>
>
> > Hi all,
>
> > be gentle please: I have only just started using clojure.
>
> > I run the following on an Intel Core 2 Duo CPU (starting clojure with
> > "java -Xms1000m -Xmx1000m -jar clojure.jar"):
>
> > user=> (time (nth (doall (map inc (range 10000000))) 9999999))
> > "Elapsed time: 5944.068355 msecs"
> > 10000000
>
> > user=> (time (nth (doall (pmap inc (range 10000000))) 9999999))
> > "Elapsed time: 108837.451146 msecs"
> > 10000000
>
> > I was expecting pmap to take less time then map, instead it took much
> > much longer.
>
> > Any thoughts?
>
> Try
> (time (count (map (fn [_] (Thread/sleep 1)) (range 1000))))
> vs.
> (time (count (pmap (fn [_] (Thread/sleep 1)) (range 1000))))
>
> On my system this is 1002 msecs vs. 39 msecs.
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