c++/cpp 计时函数/高精度计时

#include <iostream>
#include <ctime>
#include <ratio>
#include <chrono>

int main()
{
    
    
auto start = std::chrono::high_resolution_clock::now();
for (int i = 0; i < 1000000; i++)
         std::cout<<i<<std::endl;
auto end = std::chrono::high_resolution_clock::now();

// 以秒为单位，返回所用时间
std::cout<<"in millisecond time:";
std::chrono::duration<double, std::ratio<1, 1000>> diff = end - start;
std::cout << "Time is " << diff.count() << " ms\n";

// 以毫秒为单位，返回所用时间
std::cout<<"in seconds time:";
duration<double,std::ratio<1,1>> duration_s(t2-t1);
std::cout<<duration_s.count()<<" seconds"<<std::endl;

}