std::chrono::high_resolution_clock::now

 

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std::chrono::high_resolution_clock

成员函数

high_resolution_clock::now

 

static std::chrono::time_point<std::chrono::high_resolution_clock> now() noexcept;		(C++11 起)

返回表示当前时间的时间点。

参数

（无）

返回值

表示当前时间的时间点。

示例

运行此代码

#include <iostream>
#include <vector>
#include <numeric>
#include <chrono>
 
volatile int sink;
int main()
{
    for (auto size = 1ull; size < 1000000000ull; size *= 100) {
        // 记录开始时间
        auto start = std::chrono::high_resolution_clock::now();
        // 做一些工作
        std::vector<int> v(size, 42);
        sink = std::accumulate(v.begin(), v.end(), 0u); // 确保其副效应
        // 记录结束时间
        auto end = std::chrono::high_resolution_clock::now();
        std::chrono::duration<double> diff = end-start;
        std::cout << "Time to fill and iterate a vector of " 
                  << size << " ints : " << diff.count() << " s\n";
    }
}

可能的输出：

Time to fill and iterate a vector of 1 ints : 2.43e-07 s
Time to fill and iterate a vector of 100 ints : 4.1e-07 s
Time to fill and iterate a vector of 10000 ints : 2.519e-05 s
Time to fill and iterate a vector of 1000000 ints : 0.00207669 s
Time to fill and iterate a vector of 100000000 ints : 0.423087 s