Re: CVS commit: src/lib/libc/string

[christos%astron.com@localhost (Christos Zoulas)]

In article <20080924152816.9680C5654E%rebar.astron.com@localhost>,
Christos Zoulas <christos%zoulas.com@localhost> wrote:
>On Sep 24,  5:09pm, netbsd%lists.veego.de@localhost (Bernd Ernesti) wrote:
>-- Subject: Re: CVS commit: src/lib/libc/string
>
>| On Wed, Sep 24, 2008 at 02:36:02PM +0000, Christos Zoulas wrote:
>| > 
>| > Module Name:       src
>| > Committed By:      christos
>| > Date:              Wed Sep 24 14:36:02 UTC 2008
>| > 
>| > Modified Files:
>| >    src/lib/libc/string: strpbrk.c
>| > 
>| > Log Message:
>| > From Ilya Dogolazky ilya.dogolazky at teleca dot fi:
>| > 
>| > The new algorithm does not use any array initialisation.
>| > Instead of that the only integer variable "index" is initialized.
>| > It is not using any bitwise operations and shifts as well.
>| 
>| And what about the concerns and questions that were raised on tech-userlevel?
>
>Will be addressed. I just wanted to get the code in.

The new code wins with gcc -O2, loses with gcc -O.

christos

#include <time.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>


#define ITERATIONS 10000

extern void foo(const char *, const char *);
extern void bar(const char *, const char *);

static size_t
incr(size_t x)
{
        return x < 100 ? 10 :
        x < 1000 ? 100 :
        1000;
}

static void
garbage(char *buf, size_t len)
{
        buf[len] = '\0';
        while (len--)
                while ((buf[len] = (unsigned char)rand()) == '\0')
                        continue;
}

int
main(int argc, char *argv[])
{
        size_t m, n, i;
        char ms[10240], ns[10240], *p;
#ifdef CLOCK_REALTIME
        struct timespec beforefoo, afterfoo, beforebar, afterbar;
#else
        struct timeval beforefoo, afterfoo, beforebar, afterbar;
#endif


        for (m = 1; m < sizeof(ms); m += incr(m)) {
                srand(1);
                garbage(ms, m);
                for (n = 1; n < sizeof(ns); n += incr(n)) {
                        garbage(ns, n);
#ifdef CLOCK_REALTIME
                        clock_gettime(CLOCK_REALTIME, &beforefoo);
#else
                        gettimeofday(&beforefoo, NULL);
#endif
                        for (i = 0; i < ITERATIONS; i++)
                                foo(ms, ns);
#ifdef CLOCK_REALTIME
                        clock_gettime(CLOCK_REALTIME, &afterfoo);
                        timespecsub(&afterfoo, &beforefoo, &afterfoo);
#else
                        gettimeofday(&afterfoo, NULL);
                        timersub(&afterfoo, &beforefoo, &afterfoo);
#endif
#ifdef CLOCK_REALTIME
                        clock_gettime(CLOCK_REALTIME, &beforebar);
#else
                        gettimeofday(&beforebar, NULL);
#endif
                        for (i = 0; i < ITERATIONS; i++)
                                bar(ms, ns);
#ifdef CLOCK_REALTIME
                        clock_gettime(CLOCK_REALTIME, &afterbar);
                        timespecsub(&afterbar, &beforebar, &afterbar);
#else
                        gettimeofday(&afterbar, NULL);
                        timersub(&afterbar, &beforebar, &afterbar);
#endif
                        printf("%.3d, %.3d: %lld.%lld %lld.%lld\n", m, n,
                            (long long)afterfoo.tv_sec,
#ifdef CLOCK_REALTIME
                            (long long)afterfoo.tv_nsec,
#else
                            (long long)afterfoo.tv_usec,
#endif
                            (long long)afterbar.tv_sec,
#ifdef CLOCK_REALTIME
                            (long long)afterbar.tv_nsec);
#else
                            (long long)afterbar.tv_usec);
#endif
                }
        }
        return 0;
}