How to calculate the time of a function? [duplicate] - c++

Question

This question already has answers here:
Measuring execution time of a function in C++
(14 answers)
Closed 6 years ago.
I want to know the time of the quickSort function in my code, I used clock() and it get 0 .. and I also tried to use chrono and it still get me 0 .
I also made my array is large .
I don't know if my code is wrong or not !
this is my code
#include <iostream>
#include <chrono>
#include <ctime>
#include <ratio>
using namespace std;
using namespace chrono;
void quick_sort(int *arr,int left,int right){
int i=left,j=right;
int pivot=arr[(left+right)/2];
while(i<=j){
while(arr[i]<pivot)
i++;
while(arr[j]>pivot)
j--;
if(i<=j){
swap(arr[i],arr[j]);
i++;
j--;
}
}
if(left<j)
quick_sort(arr,left,j);
if(right>i)
quick_sort(arr,i,right);
}
int main()
{
int arr[30]={4,2,5,3,8,9,7,10,54,23,65,78,10,44,56,91,75,79,42,81,10,57,23,651,78,100,47,50,71,715};
high_resolution_clock::time_point t1 = high_resolution_clock::now();
quick_sort(arr,0,29);
high_resolution_clock::time_point t2 = high_resolution_clock::now();
duration<double>time_span = duration_cast<duration<double> >(t2-t1);
cout<<"it takes "<<time_span.count()<<" seconds"<<endl;
return 0;
}

Answer 1

Simple implementation:
#include <iostream>
#include <iomanip>
#include <string>
// benchmak
#include <limits>
#include <random>
#include <chrono>
#include <algorithm>
#include <functional>
class Clock
{
std::chrono::time_point<std::chrono::steady_clock> _start;
public:
static inline std::chrono::time_point<std::chrono::steady_clock> now() { return std::chrono::steady_clock::now(); }
Clock() : _start(now())
{
}
template<class DurationUnit>
std::size_t end()
{
return std::chrono::duration_cast<DurationUnit>(now() - _start).count();
}
};
Usage:
int main()
{
{
Clock clock;
business();
const double unit_time = clock.end<std::chrono::nanoseconds>();
std::cout << std::setw(40) << "business(): " << std::setprecision(3) << unit_time << " ns\n";
}
}