Digits number bench

bench.c

#include <limits.h>
#include <math.h>
#include <stdio.h>
#include <stdint.h>
#include <sys/time.h>

int digits_new(int num)
{
    int digits = 1;

    if (num == 0)
        return 1;
    if (num < 0)
    {
        if (num == INT_MIN)
            // special case for -2^31 because 2^31 can't fit in a two's complement 32-bit integer
            return 11;
        digits++;
        num = -num;
    }

    digits += floor(log10(num));
    return digits;
}

int digits_old(int num)
{
    int sign = 0;
    if (num < 0)
    {
        if (num == INT_MIN)
            // special case for -2^31 because 2^31 can't fit in a two's complement 32-bit integer
            return 12;
        sign = 1;
        num  = -num;
    }

    if (num < 1e5)
    {
        if (num < 1e3)
        {
            if (num < 10)
                return 1 + sign;
            else if (num < 1e2)
                return 2 + sign;
            else
                return 3 + sign;
        }
        else
        {
            if (num < 1e4)
                return 4 + sign;
            else
                return 5 + sign;
        }
    }
    else
    {
        if (num < 1e7)
        {
            if (num < 1e6)
                return 6 + sign;
            else
                return 7 + sign;
        }
        else
        {
            if (num < 1e8)
                return 8 + sign;
            else if (num < 1e9)
                return 9 + sign;
            else
                return 10 + sign;
        }
    }
}

#define bench(func)                             \
do {                                            \
    struct timespec start, end;                 \
    uint64_t delta_us;                          \
    int i;                                      \
    printf("checking %s... ", #func);           \
    clock_gettime(CLOCK_MONOTONIC_RAW, &start); \
    for (i = 0; i < INT_MAX; i++)               \
        func(i);                                \
    clock_gettime(CLOCK_MONOTONIC_RAW, &end);   \
    delta_us = (end.tv_sec - start.tv_sec) * 1000 + (end.tv_nsec - start.tv_nsec) / 1000000; \
    printf("%llu ms\n", delta_us); \
} while (0)

int main()
{
        bench(digits_old);
        bench(digits_new);
}

gcc -O0 -ggdb bench.c -o bench
./bench