chrono--高精度计时

在C++中使用chrono标准库进行高精度计时。示例如下：

 1 #include<iostream>
 2 #include<ctime>
 3 #include<ratio>
 4 #include<chrono>
 5 
 6 int main(int argc, char* argv[])
 7 {
 8     using namespace std::chrono;
 9     high_resolution_clock::time_point t = high_resolution_clock::now(); 
10 
11     std::cout << "printing out 1000 stars...
";
12     for (int i = 0; i < 1000; i++)
13     {
14         std::cout << "*";
15 
16     }
17     std::cout << std::endl;
18 
19     high_resolution_clock::time_point t2 = high_resolution_clock::now();
20     duration<double> time_span = duration_cast<duration<double>>(t2 - t);
21 
22     std::cout << "It tooks me " << time_span.count() << "seconds";
23     std::cout << std::endl;
24 
25     return 0;
26 }

参考： http://www.cplusplus.com/reference/chrono/high_resolution_clock/now/