thanks for pointing this out, and I absolutely appreciate the example. I'm still new to functional approach and I always like to see how things are done properly.
On Dec 13, 1:15 pm, Chouser <chou...@gmail.com> wrote: > On Sat, Dec 13, 2008 at 10:41 AM, Dmitri <dmitri.sotni...@gmail.com> wrote: > > > I wrote a simple word counter described herehttp://ptrace.fefe.de/wp/ > > it reads stdin and counts the occurrences of words, however I notice > > that it runs significantly slower than the java version in the link. > > There are several differences that could be factors. For example, the > Java version uses StreamTokenizer, while your Clojure version uses > String.split with a regex that gets recompiled for each line read. > > > I've also noticed that there is a significant speed difference between > > conj and assoc, why is that? > > If I understand correctly both should only create the delta of the new > > elements and the old structure, however assoc appears to perform much > > better. > > user=> (let [c 1000000 p [1 1]] (time (reduce #(conj % [%2 %2]) {} > (range c))) (time (reduce #(assoc % %2 %2) {} (range c))) nil) > "Elapsed time: 1544.180472 msecs" > "Elapsed time: 1894.318809 msecs" > nil > user=> (let [c 1000000 p [1 1]] (time (reduce #(conj % [%2 %2]) {} > (range c))) (time (reduce #(assoc % %2 %2) {} (range c))) nil) > "Elapsed time: 1549.159812 msecs" > "Elapsed time: 1594.18912 msecs" > > That's a million items added to a hash-map each way in about 1.5 > seconds -- not too shabby. And the speeds for conj vs. assoc seem > very close, though I'm actually seeing a slight advantage for conj. > > And I'm sorry for what follows -- it's like a compulsion for me, and I > hope it doesn't put you off. Each of these functions takes the same > input and produces the same output as your original code, but each is > implemented a bit more succinctly: > > (import '(java.io BufferedReader InputStreamReader)) > > (defn inc-count [words word] > (if (seq word) > (assoc words word (inc (words word 0))) > words)) > > (defn sort-words [words] > (reverse (sort (map (fn [[k v]] [v k]) words)))) > > (defn print-words [words] > (doseq [head words] > (println head))) > > (defn read-words [words line] > (reduce inc-count words line)) > > (defn read-input [] > (with-open [buf (BufferedReader. (InputStreamReader. System/in))] > (let [words (for [line (line-seq buf)] (.split line " "))] > (print-words (sort-words (reduce read-words {} words)))))) > > (time (read-input)) > > --Chouser --~--~---------~--~----~------------~-------~--~----~ 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 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 -~----------~----~----~----~------~----~------~--~---
