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Memory allocation nano-benchmark.
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Date: -- (:)
From: Frédéric_Gava <frederic.gava@w...>
Subject: Re: [Caml-list] Memory allocation nano-benchmark.
Hi,

I think it is due to tablesize^3 applications of functions that are not
present in the C code. But the number of line codes makes me prefer the
ocaml one.

Regards,
Frédéric Gava

> Let us look at another example where ocaml not really shines:
>
> mem.ml:
>
> let test tablesize =
>    let table =
>      Array.init tablesize (fun i ->
>        Array.init tablesize (fun j ->
>          Array.init tablesize (fun k ->
>            ((i+1)*(j+1)*(k+1))))) in ()
>
> let _ = test (int_of_string Sys.argv.(1))
>
>
> mem.c:
>
> void test(int tablesize)
> {
>
>     int i;
>     int ***table = (int ***)malloc(tablesize *sizeof(int **));
>
>     for( i=0; i<tablesize ; i++ )
>     {
>        int j;
>        table[i] = (int **)malloc(tablesize * sizeof(int *));
>
>        for ( j=0 ; j < tablesize ; j++ )
>        {
>           int k;
>           table[i][j] = (int *)malloc(tablesize * sizeof(int));
>
>           for ( k =0 ; k < tablesize ; k++ )
>           {
>              table[i][j][k] = (i+1)*(j+1)*(k+1);
>           }
>        }
>     }
> }
>
>
> int main(int argc,char *argv[])
> {
>     int i;
>
>     if( argc < 2 ) { return -1; }
>
>     test(atoi(argv[1]));
>
>     return 0;
> }
>
> On an old sub-Ghz Pentium laptop:
>
> ocamlopt -unsafe -inline 40 mem.ml
> time a.out 500
> real    0m4.229s
> user    0m3.870s
> sys     0m0.360s
>
>
> gcc -O3 -fomit-frame-pointer mem.c
> time a.out 300
> real    0m0.935s
> user    0m0.420s
> sys     0m0.500s
>
>
>
> On a new Opteron box (OK, it's cheating, becasuse OCamls ints
> are 64 bits, but there is still no disk-cache involved since
> it has 64gigs :)):
>
> gcc -O3 -fomit-frame-pointer mem.c
> time ./a.out 500
> real    0m0.803s
> user    0m0.224s
> sys     0m0.575s
>
>
> ocamlopt -unsafe -inline 40 mem.ml
> time ./a.out 500
> real    0m8.651s
> user    0m7.270s
> sys     0m1.357s
>
>
>
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