chouser wrote a solution earlier. I and a buddy modified it (a very
little) bit and managed to get it pretty blazing:
ra...@ubuntu:~$ cake run ~/challenge.clj
Chars outputted: 460
Time (in nanoseconds): 5768.677
Here is the function:
(defn count-num-chars [^String s]
(let [len (.length s)
space (int 32)]
(loop [i (int 0), c (int 0)]
(if (< i len)
(recur
(inc i)
(if (== (.codePointAt s i) space)
c
(unchecked-inc c)))
c))))
On Dec 22, 11:52 am, Rayne <disciplera...@gmail.com> wrote:
> I have a piece of code, and I'd like to see how fast it can be.
>
> (defn count-num-chars [^String s]
> (loop [s s acc 0]
> (if (seq s)
> (recur (rest s) (if (= (first s) \space) acc (inc acc)))
> acc)))
>
> This is the fastest I've been able to get it. The function is very
> simple. It takes a string and counts the number of non-space
> characters inside of that string.
>
> I've been testing this code against a 460 non-space character string.
> Here is the entire source, benchmarking and all:
>
> (def s (apply str (repeat 20 "This is a really long string")))
>
> (defn count-num-chars [^String s]
> (loop [s s acc 0]
> (if (seq s)
> (recur (rest s) (if (= (first s) \space) acc (inc acc)))
> acc)))
>
> (println "Chars outputted:" (count-num-chars s))
>
> (let [before (System/nanoTime)]
> (dotimes [_ 1000]
> (count-num-chars s))
> (let [after (System/nanoTime)]
> (println "Time (in nanoseconds):" (/ (- after before) 1000.0))))
>
> Running it gives me around 137343.295 nanoseconds. I've seen some Java
> algorithms that could run at just under 3000 nanoseconds.
>
> Hide your children and hide your women; I want to see the direst,
> nastiest, rawest, fastest possible implementation of this function.
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