To get the benefit of memoization, you need to store the memoized function and use it again. (memoize fib-nocur) returns a function that contains an internal memory of past results. If you call (memoize fib-nocur) again you get a second function with an (empty!) internal memory. If you don't use the first one more than once you don't see any benefit from its memory.
So, try this: (let [f (memoize fib-nocur)] (time (f 30)) (time (f 30)) (time (f 30))) and see if the second and third times are much shorter than the first one. On Sat, Apr 13, 2013 at 12:52 AM, Liao Pengyu <arise...@gmail.com> wrote: > Hi, there. I have a question about the memoization in clojure. > I compare two functions to test the performance improvement of memoization: > (defn fib [n] > (if (or (zero? n) (= n 1)) > 1 > (+ (fib (dec n) ) (fib (- n 2))))) > > (time (fib 30)) > get the result: > "Elapsed time: 316.65 msecs" > 1346269 > > And then test for memoization: > user> (time ((memoize fib-nocur) 30)) > "Elapsed time: 308.729 msecs" > 1346269 > user> (time ((memoize fib-nocur) 30)) > "Elapsed time: 314.942 msecs" > 1346269 > user> (time ((memoize fib-nocur) 30)) > "Elapsed time: 308.657 msecs" > 1346269 > > Seems no effect. Since I just test it in nrepl and have no experience > about using clojure in project, I wander was the memoization really works? > Look forward to your responses > > -- > -- > 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 unsubscribe from this group and stop receiving emails from it, send an > email to clojure+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- -- 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 unsubscribe from this group and stop receiving emails from it, send an email to clojure+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
