The amount of work in each element of the pmap is so small that the overhead per element is dominating the CPU usage, e.g. overhead like constructing a future for each element of the collection you are mapping over. Try a test case where the computation being done in the function you supply to map is a lot more than inc.
Note that total CPU time for pmap will always have some extra overhead above the corresponding map - it is recommended to use it when that extra overhead is small compared to the total computation time required. Andy Sent from my iPhone On Nov 6, 2010, at 4:57 AM, philip schwarz <philip.johann.schw...@googlemail.com> wrote: > 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? > > -- > 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 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
