Computing CPU time in C++ on Windows

Question

Is there any way in C++ to calculate how long does it take to run a given program or routine in CPU time?

I work with Visual Studio 2008 running on Wind

Answer 1

The clock() function [as provided by Visual C++ 2008] doesn't return processor time used by the program, while it should (according to the C standard and/or C++ standard). That said, to measure CPU time on Windows, I have this helper class (which is inevitably non-portable):

class ProcessorTimer
{
  public:
    ProcessorTimer() { start(); }
    void start() { ::GetProcessTimes(::GetCurrentProcess(), &ft_[3], &ft_[2], &ft_[1], &ft_[0]); }
    std::tuple stop()
    {
        ::GetProcessTimes(::GetCurrentProcess(), &ft_[5], &ft_[4], &ft_[3], &ft_[2]);
        ULARGE_INTEGER u[4];
        for (size_t i = 0; i < 4; ++i)
        {
            u[i].LowPart = ft_[i].dwLowDateTime;
            u[i].HighPart = ft_[i].dwHighDateTime;
        }
        double user = (u[2].QuadPart - u[0].QuadPart) / 10000000.0;
        double kernel = (u[3].QuadPart - u[1].QuadPart) / 10000000.0;
        return std::make_tuple(user, kernel);
    }
  private:
    FILETIME ft_[6];
};


class ScopedProcessorTimer
{
  public:
    ScopedProcessorTimer(std::ostream& os = std::cerr) : timer_(ProcessorTimer()), os_(os) { }
    ~ScopedProcessorTimer()
    {
        std::tuple t = timer_.stop();
        os_ << "user " << std::get<0>(t) << "\n";
        os_ << "kernel " << std::get<1>(t) << "\n";
    }
  private:
    ProcessorTimer timer_;
    std::ostream& os_;
}

For example, one can measure how long it takes a block to execute, by defining a ScopedProcessorTimer at the beginning of that {} block.