Stop Timer At Any Time and Start Timer Again in C++

Question

I am doing in C++. For example, I want to calculate the time taken for process A, reset the timer and start the timer again to calculate the time for process B. How do I reset the timer and start it again for my second process?

Answer 1

Use ctime library.

Code:

#include <iostream>
#include <ctime>
using namespace std;
int main()
{
    time_t time_1;
    time_t time_2;

    time ( &time_1 );
    processA();
    time ( &time_2 );

    cout<<Time Taken by A: << time_2 - time_1<< seconds<<endl;

    time ( &time_1 );
    processB();
    time ( &time_2 );

    cout<<Time Taken by B: << time_2 - time_1<< seconds<<endl;
}

Similar question here:- Trying to calculate difference between two times, won't subtract.

Edit: There is clock() function which is an approximate measure taken by a process in execution. Whereas time() function gives you the system time. So depends on what you need, you might use one of them. As these two functions will return different values. Use time() when you need the exact time taken, including the time when the process was in wait queue for resource but if you need time taken by your process in execution then use clock(). clock() will be faster (multiple threads executing in parallel which will speed up the clock) or slower (resources are scarce).

Clock Code:

It is used in the same manner as time. Each call to clock returns the clock value and reset the time

c_start = clock();
processA();
c_end = clock();

cout<<Time Taken by A: << c_end - c_start<< seconds<<endl;

c_start = clock();
processB();
c_end = clock();

cout<<Time Taken by B: << c_end - c_start<< seconds<<endl;

Great reference on clock(): http://en.cppreference.com/w/cpp/chrono/c/clock

Time in milliseconds:

#include <chrono>


using namespace std::chrono;
milliseconds ms = duration_cast< milliseconds >(system_clock::now().time_since_epoch()

Again subract the times as in previous codes!