代码执行时间的计算（c++11)

这是c++11的一个新的库，可以用于计算代码执行的时间。
下面使用了chrono计算各种运算所花费的时间。

#include 
#include 
#include 
using namespace std;

void test_exec_time()
{
	//------------------------------- * 
	auto start = std::chrono::steady_clock::now();
	double res = 25622556 * 1230256;
	auto end = std::chrono::steady_clock::now();

	std::chrono::duration elapsed1 = end - start;
	std::chrono::duration elapsed2 = end - start;

	

	std::cout << "* exec time = " << elapsed1.count() << " 微秒" << std::endl;
	std::cout << "* exec time = " << elapsed2.count() << " 纳秒" << std::endl;

	//----------------------------------- /
	start = std::chrono::steady_clock::now();
	res = 25622556 / 648;
	end = std::chrono::steady_clock::now();

	elapsed1 = end - start;
	elapsed2 = end - start;

	std::cout << "/ exec time = " << elapsed1.count() << " 微秒" << std::endl;
	std::cout << "/ exec time = " << elapsed2.count() << " 纳秒" << std::endl;

	//-------------------------------------- -
	start = std::chrono::steady_clock::now();
	res = 25622556 - 648;
	end = std::chrono::steady_clock::now();

	elapsed1 = end - start;
	elapsed2 = end - start;

	std::cout << "- exec time = " << elapsed1.count() << " 微秒" << std::endl;
	std::cout << "- exec time = " << elapsed2.count() << " 纳秒" << std::endl;

	//--------------------------------------- +
	start = std::chrono::steady_clock::now();
	res = 25622556 + 648;
	end = std::chrono::steady_clock::now();

	elapsed1 = end - start;
	elapsed2 = end - start;

	std::cout << "+ exec time = " << elapsed1.count() << " 微秒" << std::endl;
	std::cout << "+ exec time = " << elapsed2.count() << " 纳秒" << std::endl;

	//--------------------------------------- |
	start = std::chrono::steady_clock::now();
	res = 25622556 | 648;
	end = std::chrono::steady_clock::now();

	elapsed1 = end - start;
	elapsed2 = end - start;

	std::cout << "| exec time = " << elapsed1.count() << " 微秒" << std::endl;
	std::cout << "| exec time = " << elapsed2.count() << " 纳秒" << std::endl;

	//--------------------------------------- &
	start = std::chrono::steady_clock::now();
	res = 25622556 & 648;
	end = std::chrono::steady_clock::now();

	elapsed1 = end - start;
	elapsed2 = end - start;

	std::cout << "& exec time = " << elapsed1.count() << " 微秒" << std::endl;
	std::cout << "& exec time = " << elapsed2.count() << " 纳秒" << std::endl;

}

int main()
{
	test_exec_time();

	return 0;
}