Measuring execution time of a function in C++

Question

I want to find out how much time a certain function takes in my C++ program to execute on Linux. Afterwards, I want to make a speed comparison . I saw several time function but ended up with this from boost. Chrono:

process_user_cpu_clock, captures user-CPU time spent by the current process 

Now, I am not clear if I use the above function, will I get the only time which CPU spent on that function?

Secondly, I could not find any example of using the above function. Can any one please help me how to use the above function?

P.S: Right now , I am using std::chrono::system_clock::now() to get time in seconds but this gives me different results due to different CPU load every time.

Answer 1

It is a very easy-to-use method in C++11. You have to use std::chrono::high_resolution_clock from <chrono> header.

Use it like so:

#include <chrono>  /* Only needed for the sake of this example. */ #include <iostream> #include <thread>      void long_operation() {     /* Simulating a long, heavy operation. */      using namespace std::chrono_literals;     std::this_thread::sleep_for(150ms); }  int main() {     using std::chrono::high_resolution_clock;     using std::chrono::duration_cast;     using std::chrono::duration;     using std::chrono::milliseconds;      auto t1 = high_resolution_clock::now();     long_operation();     auto t2 = high_resolution_clock::now();      /* Getting number of milliseconds as an integer. */     auto ms_int = duration_cast<milliseconds>(t2 - t1);      /* Getting number of milliseconds as a double. */     duration<double, std::milli> ms_double = t2 - t1;      std::cout << ms_int.count() << "ms\n";     std::cout << ms_double.count() << "ms\n";     return 0; } 

This will measure the duration of the function long_operation.

Possible output:

150ms 150.068ms 

Working example: https://godbolt.org/z/oe5cMd