Aleksey | High accuracy timer

class HRTimer {
public:
    HRTimer() : frequency(GetFrequency()) { }
    LONGLONG GetFrequency()
    {
        LARGE_INTEGER proc_freq;
        QueryPerformanceFrequency(&proc_freq);
        return proc_freq.QuadPart;
    }
    void Reset()
    {
        DWORD_PTR oldmask = SetThreadAffinityMask(GetCurrentThread(), 0);
        QueryPerformanceCounter(&start);
        SetThreadAffinityMask(GetCurrentThread(), oldmask);
    }
    double GetElapsed()
    {
        DWORD_PTR oldmask = SetThreadAffinityMask(GetCurrentThread(), 0);
        QueryPerformanceCounter(&stop);
        SetThreadAffinityMask(GetCurrentThread(), oldmask);
        return ((stop.QuadPart - start.QuadPart) / (double)frequency);
    }
private:
    LARGE_INTEGER start;
    LARGE_INTEGER stop;
    LONGLONG frequency;
};