Nice code chouser, always nice to see a succinct functional example.
On Dec 13, 10:15 am, 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
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