Auto Timer in OGL

June 02, 2013

For the performance tuning, the simplest way is to record how many time is elapsed in a function. The only difficulty we’re facing is that: there maybe many exit for a function. Thanks to C++’s constructor/deconstructor feature, it’s easy for developer to record the elsaped time.

auto timer in C++

Compared to C, constructor/deconstructor is an important improvement of C++. It’s not only make sure that the object/struct will be automatically initialized, but also keep C++ developer far away from MLK issue by Smart Pointer. And it’s also a good guidance for developer to do simple performance tuning; here is a implemention of the auto timer:

class AutoTimer
{
    public:
        AutoTimer(const char* label) : m_label(label)
        {
            m_start = new timeval();
            gettimeofday((timeval*)m_start, NULL);
        }

        ~AutoTimer()
        {
            m_end = new timeval();
            gettimeofday((timeval*)m_end, NULL);

            double start, end;

            start = ((timeval*)m_start)->tv_sec * 1000 + ((timeval*)m_start)->tv_usec / 1000.0;
            end = ((timeval*)m_end)->tv_sec * 1000 + ((timeval*)m_end)->tv_usec / 1000.0;

            if (logger) {
                loggerDrv->log2(__FILE__, __LINE__, "%s : start: <%lf>, end: <%lf>, duration: <%lf>.", 
                        m_label.c_str(), start, end, end - start);
            }

            delete (timeval*) m_start;
            delete (timeval*) m_end;
        }

    private:
        timeval* m_start;
        timeval* m_end;
        std::string m_label;
};

How to use

Now, we have a simple performance testing tool: auto timeer; and the it’s easy to use as follow:

int handle_input(ogl::Handler fd)
{
    AutoTimer timer("handle_input");
    ....
}