How to check the speed of code execution in C++?

Question

C++ / C#

#include <iostream>
using namespace std;

int main()
{

 int n = 12;
 int a[n];

 a[0]=-1;
 a[1]=5;
 a[2]=4;
 a[3]=6;
 a[4]=0;
 a[5]=9;
 a[6]=7;
 a[7]=10;
 a[8]=-5;
 a[9]=23;
 a[10]=-9;
 a[11]=1;

int i = 0;
int j = 0;
int buffer = 0;

for(i=0; i<n; ++i){
    for (j=0;j<(n-1-i); ++j){
      if (a[j]>a[j+1]) {
          buffer = a[j+1];
          a[j+1] = a[j];
          a[j] = buffer;
       }
    }
}

 for (i=0; i<n; ++i) {
     cout<<a[i]<<endl;
 }



 system("pause");
 return 0;
}

How to check the speed of the main() function? in micro (nano) seconds?

Answer 1

#include <iostream>
#include <cstdio>
#include <ctime>

int main() {
    std::clock_t start;
    double duration;

    start = std::clock();

    /* Сюда вставить тестируемый код */

    duration = ( std::clock() - start ) / (double) CLOCKS_PER_SEC;

    std::cout<<"printf: "<< duration <<'\n';
}

If the value is too small, then you can repeat the code being tested 1000 times and divide the total time by 1000.
In general, you need to increase the value of N to at least 10000, and fill the array with random values ​​in a loop.

Answer 2

One might assume O(1) for an optimizing compiler.

Answer 3

If on Linux, then you can use the time command.