http://www.haskell.org/haskellwiki/Performance
These are the performance tips I was referring to. (4. General techniques, laziness, space leaks.) On Sep 18, 5:03 pm, Jonathan Smith <jonathansmith...@gmail.com> wrote: > Hi! > > This is happening because you have integers saved to a global > variable. > > (iterate inc 1) creates an infinite lazy seq. > > Def-fing it to a global says 'Hey, i might want this later!' to > Clojure. > > This means that as you take numbers from integers; > they get saved in memory rather than being garbage collected. > > This is why you run out of memory. > > You'll notice that this version: > > (limited-reduce + (iterate inc 1) 1000000) > > Runs (in a nice constant memory) even though yours (which almost > appears equivalent) will not! > > In fact, even this version: > (limited-reduce + (iterate inc 1) 1000000000) > Runs in a nice constant space memory, although it takes a long time. > > Nothing is wrong with the code, its that darn data! > > If you are interested in this stuff, read about 'Haskell performance > tips'. A lot of people would make references to 'holding on to the > head' and such, and it would pretty much go 'whoooosh' right over /my/ > head. Then I read a bit about how Haskell and how laziness there > worked, and it started to make sense. > > Hope this helps, > -Jon > > On Sep 18, 3:52 pm, Patrik Fredriksson <patri...@gmail.com> wrote: > > > Hi! > > > Could someone please help me understand why the following causes a > > java.lang.OutOfMemoryError: Java heap space for large n:s (100000 > > works fine, 1000000 does not). > > > (def integers (iterate inc 1)) > > > (defn limited-reduce [fn coll n] > > (loop [c coll i n result 0] > > (if (zero? i) > > result > > (recur > > (rest c) > > (dec i) > > (fn result (first c)))))) > > > (limited-reduce + integers 100000) > > > Many thanks! > > > /Patrik > > --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
