Question

I do not really wish to profile because I was wanting to do many different small benchmarks on different simple functions. For the life of me I cannot find a way to record the amount of milliseconds in C++, I am using Linux by the way.

Can you suggest the method to get the system clock in milliseconds (I may settle with seconds if I cannot find an easy way..) and what header they are included in?

Answer 1

using gettimeofday function from sys/time.h header file, i use this class:

#include <cstdlib>
#include <sys/time.h>

class Timer
{
    timeval timer[2];

  public:

    timeval start()
    {
        gettimeofday(&this->timer[0], NULL);
        return this->timer[0];
    }

    timeval stop()
    {
        gettimeofday(&this->timer[1], NULL);
        return this->timer[1];
    }

    int duration() const
    {
        int secs(this->timer[1].tv_sec - this->timer[0].tv_sec);
        int usecs(this->timer[1].tv_usec - this->timer[0].tv_usec);

        if(usecs < 0)
        {
            --secs;
            usecs += 1000000;
        }

        return static_cast<int>(secs * 1000 + usecs / 1000.0 + 0.5);
    }
};

for example:

#include <iostream>
#include <string>
#include <sstream>

int main()
{
    Timer tm;
    std::ostringstream ooo;
    std::string str;

    tm.start();
    for(int i = 0; i < 10000000; ++i)
    {
        ooo << "This is a string. ";
    }
    tm.stop();
    std::cout << "std::ostingstream -> " << tm.duration() << std::endl;

    tm.start();
    for(int i = 0; i < 10000000; ++i)
    {
        str += "This is a string. ";
    }
    tm.stop();
    std::cout << "std::string -> " << tm.duration() << std::endl;
}