Timing a for loop with clock - c++

Question

Hi so I am trying to do a program that sums 20 consecutive numbers and calculates the time that it took to do so... the problem is that when I run the program the time is always 0... any ideas?
this is what I have so far... thanks!
#include <iostream>
#include <time.h>
using namespace std;
int main()
{
int finish = 20;
int start = 1;
int result = 0;
double msecs;
clock_t init, end;
init = clock();
for (int i = start; i <= finish; i++)
{
result += i;
}
end = clock();
cout << ((float)(end - init)) *1000 / (CLOCKS_PER_SEC);
system ("PAUSE");
return 0;
}

Answer 1

No matter what technique you use for timing they all have some precision. This simply executes so fast that your timer isn't registering any time as having passed.
Aside #1: Use high_resolution_clock - maybe that will register something non-zero, probably not.
Aside #2: Don't name your variable null, in C++ that implies 0 or a null pointer

Answer 2

You can try this...but you might need version C++11.
This can get down to 0.000001 seconds.
#include <iostream>
#include <ctime>
#include <ratio>
#include <chrono>
//using namespace std;
int main()
{
using namespace std::chrono;
high_resolution_clock::time_point t1 = high_resolution_clock::now();
int finish = 20;
int start = 1;
for (int i = start; i <= finish; i++)
{
result += i;
}
high_resolution_clock::time_point t2 = high_resolution_clock::now();
duration<double> time_span = duration_cast<duration<double>>(t2 - t1);
cout << time_span.count() << " seconds" << endl;
end = clock();
system ("PAUSE");
return 0;
}