You should store in ellapsedtime
the number of microseconds elapsed since the fisrt call to QueryPerformanceCounter
, and you should not overwrite the first time stamp.
Working code:
// gets another stamp value
QueryPerformanceCounter(&T2);
// measures the difference between the two stamp
ellapsedtime += (T2.QuadPart - T1.QuadPart);
cout << "number of tick " << ellapsedtime << endl;
ellapsedtime *= 1000000.;
ellapsedtime /= freq.QuadPart;
cout << "number of Microseconds " << ellapsedtime << endl;
// checks if the elapsed time is bigger than or equal to the desired time
if(ellapsedtime/1000000.>=desiredtime) {
cout << "done!!!" << endl;
timing = 0; // breaks the loop
}
Be sure to read : Acquiring high-resolution time stamps