This guide is modified from section (d) of the worksheet inside Module 10 of Phys 6810 Computational Physics (Spring 2023).

NOTE: gprof does not work on macOS. Please use a linux machine (such as OSC)

To use gprof, compile and link the relevant codes with the -pg option:
Take a look at the Makefile make_hello_world and modify both the CFLAGS and LDFLAGS lines to include -pg

Compile and link the script by typing
    make -f make_hello_world

Execute the program
    ./hello_world.x

With the -pg flags, the execution will generate a file called gmon.out that is used by gprof.
The program has to exit normally (e.g. we can't stop with a ctrl-C).
Warning: Any existing gmon.out file will be overwritten.

Run gprof and save the output to a file (e.g., gprof.out) by
    gprof hello_world.x > gprof.out

We should at this point see a text file called gprof.out which contains the profile of hello_world.cpp
    vim gprof.out

#include <iostream>
#include <thread>
#include <chrono>
#include <cmath>


using namespace std;

void nap(){
  // usleep(3000);
  // this_thread::sleep_for(30000ms);

  for (int i=0;i<1000000000;i++){
    double j = sqrt(i^2);
  }
}

int main(){

  cout << "taking a nap" << endl;

  nap();

  cout << "hello world" << endl;

}