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Subject[Test Case] performance enhancement for simple_strtoul
Date
Hello,

Here's the test case for the suggested simple_strtoul function. I just
finished testing on a P3 where it seems to show a 16-20% speed improvement
over the current algorithm.

compile it as:

gcc /usr/src/linux/lib/ctype.c strtoul_test.c -o strtoul_test

You can change the numeric base value with this define to 8, 10, or 16 to
see the speed change for each numeric representation:

#define BASE 10

Have fun,
Steve Grubb

------strtoul_test.c----------

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/resource.h>
#include <linux/ctype.h>

struct timeval last_stopwatch_time;


void stopwatch()
{
struct timeval now;
int delta;

gettimeofday(&now, 0);
delta = (now.tv_sec - last_stopwatch_time.tv_sec) * 1000000 +
(now.tv_usec - last_stopwatch_time.tv_usec);
printf ("Stopwatch: elapsed time %d.%03d seconds\n\n",
delta / 1000000, (delta / 1000) % 1000);


last_stopwatch_time = now;
}

unsigned long old_simple_strtoul(const char *cp,char **endp,unsigned int
base)
{
unsigned long result = 0,value;
if (!base) {
base = 10;
if (*cp == '0') {
base = 8;
cp++;
if ((*cp == 'x') && isxdigit(cp[1])) {
cp++;
base = 16;
}
}
}
while (isxdigit(*cp) && (value = isdigit(*cp) ? *cp-'0' : (islower(*cp)
? toupper(*cp) : *cp)-'A'+10) < base) {
result = result*base + value;
cp++;
}
if (endp)
*endp = (char *)cp;
return result;
}

unsigned long new_simple_strtoul2(const char *cp,char **endp,unsigned int
base)
{
unsigned char c;
unsigned long result = 0;
if (!base) {
base = 10;
if (*cp == '0') {
base = 8;
cp++;
if ((*cp == 'x') && isxdigit(cp[1])) {
cp++;
base = 16;
}
}
}
c = *cp;
switch (base) {
case 10:
while (isdigit(c)) {
result = (result*10) + (c & 0x0f);
c = *(++cp);
}
break;
case 16:
while (isxdigit(c)) {
result = (result<<4);
if (c&0x40)
result += (c & 0x07) + 9;
else
result += (c & 0x0f);
c = *(++cp);
}
break;
case 8:
while (isdigit(c)) {
if ((c&0x37) == c)
result = (result<<3) + (c & 0x07);
else
break;
c = *(++cp);
}
}
if (endp)
*endp = (char *)cp;
return result;
}

#define NUMBER_TO_TEST 32768
#define BASE 10
char f[3][3] = { "%d", "%X", "%o"};
char str[NUMBER_TO_TEST][32];
unsigned long r[NUMBER_TO_TEST];

int main()
{
int rn, i, j, iterations = 1000;
time_t tm;

time(&tm);
srand((unsigned) tm);
rn = rand();

// do setup here
for (i=0; i<NUMBER_TO_TEST; i++) {
r[i] = rand()%0x7FFFFFF;
switch (BASE) {
case 10:
sprintf(&str[i][0], &f[0][0], r[i]);
break;
case 16:
sprintf(&str[i][0], &f[1][0], r[i]);
break;
case 8:
sprintf(&str[i][0], &f[2][0], r[i]);
}
}

puts("Starting old algorithm");
sleep(5); // let the system settle down
gettimeofday(&last_stopwatch_time, 0);
for (i=0; i<iterations; i++) {
for (j=0; j<NUMBER_TO_TEST; j++) {
old_simple_strtoul(&str[j][0], NULL, BASE);
}
}
stopwatch();

puts("New algorithm");
sleep(5); // let the system settle down
gettimeofday(&last_stopwatch_time, 0);
for (i=0; i<iterations; i++) {
for (j=0; j<NUMBER_TO_TEST; j++) {
new_simple_strtoul2(&str[j][0], NULL, BASE);
}
}
stopwatch();

puts("Now checking values");
for (i=0; i<NUMBER_TO_TEST; i++) {
unsigned long t = new_simple_strtoul2(&str[i][0], NULL, BASE);
if (r[i] != t) {
switch (BASE) {
case 10:
printf("is %s conv %d\n", &str[i][0], t);
break;
case 16:
printf("is %s conv %x\n", &str[i][0], t);
break;
case 8:
printf("is %s conv %o\n", &str[i][0], t);
}
break;
}
}

return 0;
}


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