错误：尚未声明“ high_resolution_clock”

问题描述

我在Windows 10上使用的是g ++版本8.1.0，但在尝试编译时仍然如此

auto start=high_resolution_clock::Now();
rd(n);
auto stop=high_resolution_clock::Now();
auto duration = duration_cast<microseconds>(stop-start);
cout<<duration.count()<<endl;

我收到错误信息

error: 'high_resolution_clock' has not been declared
 auto start=high_resolution_clock::Now();
            ^~~~~~~~~~~~~~~~~~~~~

我同时包含了chrono和time.h

解决方法

您需要在std::chrono::，high_resolution_clock和microseconds前面指定duration_cast命名空间限定符，例如：

#include <chrono>

auto start = std::chrono::high_resolution_clock::now();
rd(n);
auto stop = std::chrono::high_resolution_clock::now();
auto duration = std::chrono::duration_cast<std::chrono::microseconds>(stop-start);
std::cout << duration.count() << std::endl;

否则，您可以改用using语句，例如：

#include <chrono>
using namespace std::chrono;

auto start = high_resolution_clock::now();
rd(n);
auto stop = high_resolution_clock::now();
auto duration = duration_cast<microseconds>(stop-start);
std::cout << duration.count() << std::endl;

或：

#include <chrono>
using std::chrono::high_resolution_clock;
using std::chrono::microseconds;
using std::chrono::duration_cast;

auto start = high_resolution_clock::now();
rd(n);
auto stop = high_resolution_clock::now();
auto duration = duration_cast<microseconds>(stop-start);
std::cout << duration.count() << std::endl;

,

哦，我刚找到解决方案， 我忘了使用chrono名称空间 因此代码应为：

auto start=chrono::high_resolution_clock::now();
rd(n);
auto stop=chrono::high_resolution_clock::now();
auto duration = chrono::duration_cast<chrono::microseconds>(stop-start);
cout<<duration.count()<<endl;