Measuring time in C

Question

I\'m trying to measure some activity in C (Matrix multiplying) and noticed that I should do something like this:

clock_t start = clock();
sleep(3);
clock_t e         


        

Answer 1

If you don't care about being tied to Windows, you can try the high resolution timer. It's is a lot more precise than time(), which only has a precision of a single second because it the uses UNIX format.

#include 
#include 

__int64 countspersec = 0;
double secpercount = 0.0;
__int64 starttime = 0;
__int64 curtime = 0;

int main() {

    // Get current time, and determine how fast the clock ticks
    QueryPerformanceCounter((LARGE_INTEGER*)&starttime);
    QueryPerformanceFrequency((LARGE_INTEGER*)&countspersec);
    secpercount = 1.0/(double)countspersec;

    /* calculate something */

    // Standard end-start stuff, account for clock speed
    QueryPerformanceCounter((LARGE_INTEGER*)&curtime);
    std::cout << "Time needed: " << (curtime-starttime)*secpercount << " sec\n";
    return 0;
}