Methods for precise timing of C + + in window

Well, the programmer's eternal quest is performance, right?

In order to measure performance, timing is naturally required.

However, regardless of the C standard library or C + + standard library, the time API accuracy is not high because of commonality . The basic is the millisecond level.

So if you want to really accurately measure the performance of a program, you still have to rely on the system API. The following timing method can be accurate to <1us.

If you do not want to know what the principle, you can directly copy the following simple timer class. Put it in a header file and include it when you use it.

#include <windows.h>class Mytimer{private:large_integer _freq; Large_integer _start; Large_integer _stop;public:mytimer () {queryperformancefrequency (&_freq);} inline void Start () {QueryPerformanceCounter (&_start);} inline void Stop () {QueryPerformanceCounter (&_stop);} Inline double elapse () {return 1e3* (_stop. QuadPart-_start. QuadPart)/_freq. QuadPart;} Inline long Long ticks () {return _stop. QuadPart-_start. QuadPart;}};

The way to use it is simple: three APIs: start, stop, elapse.

Example:        mytimer timer;        Timer.start ();        Matrixxd m3 = m1 * m2;        Critical Code here        timer.stop ();        printf ("Time Elapsed:%lf\n", Timer.elapse ());

The main system API used is as follows two.

QueryPerformanceCounter

From <http://msdn.microsoft.com/en-us/library/windows/desktop/ms644904 (v=vs.85). aspx>

QueryPerformanceFrequency function

From <http://msdn.microsoft.com/en-us/library/windows/desktop/ms644905 (v=vs.85). aspx>

Take a look at MSDN 's instructions.

Methods for precise timing of C + + in window