I guess it would be a better guess if you could includethe cpu type/speed
for a rough reference...
Devrim Baris Acar
On Fri, Dec 24, 2010 at 09:55, Alan Busby <thebu...@thebusby.com> wrote:
> 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
>
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