Capturing a time in milliseconds

To have millisecond precision you have to use system calls specific to your OS.

In Linux you can use

#include <sys/time.h>

timeval tv;
gettimeofday(&tv, 0);
// then convert struct tv to your needed ms precision

timeval has microsecond precision.

In Windows you can use:

#include <Windows.h>

SYSTEMTIME st;
GetSystemTime(&st);
// then convert st to your precision needs

Of course you can use Boost to do that for you :)

//C++11 Style:

cout << "Time in Milliseconds =" << 
 chrono::duration_cast<chrono::milliseconds>(chrono::steady_clock::now().time_since_epoch()).count() 
 << std::endl;

cout << "Time in MicroSeconds=" << 
 chrono::duration_cast<chrono::microseconds>(chrono::steady_clock::now().time_since_epoch()).count() 
 << std::endl;

You need a timer with a higher resolution in order to capture milliseconds. Try this:

int cloc = clock();
//do something that takes a few milliseconds
cout << (clock() - cloc) << endl;

This is of course dependent on your OS.

The high resolution timers are usually gettimeofday on Linux style platforms and QueryPerformanceCounter on Windows.

You should be aware that timing the duration of a single operation (even with a high resolution timer) will not yield accurate results. There are too many random factors at play. To get reliable timing information, you should run the task to be timed in a loop and compute the average task time. For this type of timing, the clock() function should be sufficient.