Hi All,
On Fri, Dec 24, 2010 at 4:32 PM, Meikel Brandmeyer <m...@kotka.de> wrote:
> Most interesting is also the relation between the different versions on the
> given machine. Just the numbers of one algorithm aren't really comparable, I
> guess. (different machine, different load, different phase of moon, who
> knows...)
>
Did the below just for my own amusement on a 64bit linux box, and thought it
might be interesting to others. The fastest implementation was using areduce
with 1.3.0-alpha and unchecked ops for 2800ns. Unoptimized C was doing 700ns
though, and with -O2 it was 400ns. Reminds me why JNI can be so valuable
sometimes.
/* -O0 low of 700ns
-02 low of 400ns */
int char_count(char* ptr)
{
int count = 0;
int i;
for(i=0; ptr[i]; ptr++)
if(ptr[i]!=32)
count++;
return count;
}
;; 1.2.0 low of 65000ns
;; 1.3.0-alpha3 low of 46000ns
;;
(defn count-num-chars-v1 [^String s]
(loop [s s acc 0]
(if (seq s)
(recur (rest s) (if (= (first s) \space) acc (inc acc)))
acc)))
;; 1.2.0 low of 6200ns
;; 1.3.0-alpha3 low of 4800ns
;;
(defn count-num-chars-v2 [^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))))
;; 1.2.0 low of 12500ns
;; 1.3.0-alpha3 low of 4450ns
;; 1.3.0-alpha3 with *unchecked-math* enabled low of 2800ns
;;
(defn count-num-chars-v3 [^String s]
(let [as (.toCharArray s)]
(areduce as idx acc 0 (if (= (int (aget as idx)) (int \space)) acc
(inc acc)))))
;; 1.2.0 untested
;; 1.3.0-alpha3 low of 4500ns
;;
(defn count-num-chars-v4 ^long [^String s]
(let [l (.length s)
c \space]
(loop [i 0 acc 0]
(if (< i l)
(recur (inc i)
(if (identical? (.charAt s i) c) acc
(inc acc)))
acc))))
Hope this helps,
Alan
--
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
