Crude log benchmark code

#include <math.h>
#include <limits.h>
#include <iostream>
#include <time.h>

using namespace std;

timespec diff(timespec start, timespec end)
{
    timespec temp;
    if ((end.tv_nsec - start.tv_nsec) < 0)
    {
    temp.tv_sec = end.tv_sec - start.tv_sec - 1;
    temp.tv_nsec = 1000000000 + end.tv_nsec - start.tv_nsec;
    }
    else
    {
    temp.tv_sec = end.tv_sec - start.tv_sec;
    temp.tv_nsec = end.tv_nsec - start.tv_nsec;
    }
    return temp;
}

int main(void)
{
    timespec start, end;
    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start);
    double sum = 0;
    double m = 0.0;
    for (int n = 1; n < INT_MAX; ++n)
    {
    m = n * 10.1;
    sum += log(m);
    }
    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end);
    cout << "ln=";
    cout << diff(start, end).tv_sec << ":" << diff(start, end).tv_nsec << endl;


    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start);
    sum = 0, m = 0.0;
    for (int n = 1; n < INT_MAX; ++n)
    {
    m = n * 10.1;
    sum += log2(m);
    }
    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end);
    cout << "lb=";
    cout << diff(start, end).tv_sec << ":" << diff(start, end).tv_nsec << endl;


    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &start);
    sum = 0, m = 0.0;
    for (int n = 1; n < INT_MAX; ++n)
    {
    m = n * 10.1;
    sum += log10(n);
    }
    clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &end);
    cout << "lg=";
    cout << diff(start, end).tv_sec << ":" << diff(start, end).tv_nsec << endl;

    return 0;
}