令人意外的构造函数和析构函数

印象中构造函数和析构函数的使用不太会影响效率，但在实际开发中却遇到，一个函数频繁的调用一个类的构造函数和析构函数却很耗时

class TestA
{
public:
	TestA()
	{
		m_dX = m_dY = m_dZ = 0;
		m_dW = 0;
	}
	~TestA() {}
	double m_dX;
	double m_dY;
	double m_dZ;
	double m_dW;
};

class TestB
{
public:
	double m_dX;
	double m_dY;
	double m_dZ;
	double m_dW;
};

{
		int nSize = 50000000;

		double dATime = 0;
		{
			auto StartTime = std::chrono::steady_clock::now();

			for (int i = 0; i < nSize; ++i)
			{
				TestA A1[100];
			}

			auto EndTime = std::chrono::steady_clock::now();
			dATime += std::chrono::duration_cast<std::chrono::milliseconds>(EndTime - StartTime).count();//毫秒
		}

		double dBTime = 0;
		{
			auto StartTime = std::chrono::steady_clock::now();

			for (int i = 0; i < nSize; ++i)
			{
				TestB B1[100];
			}

			auto EndTime = std::chrono::steady_clock::now();
			dBTime += std::chrono::duration_cast<std::chrono::milliseconds>(EndTime - StartTime).count();//毫秒
		}
		dATime = dATime / 1000;
		dBTime = dBTime / 1000;
		CString strA;
		strA.Format(_T("%f"), dATime);

		CString strB;
		strB.Format(_T("%f"), dBTime);
		CString strAll;
		strAll = CString("A: ") + strA + CString("s\r\n") + CString("B: ") + strB + CString("s\r\n");
		MessageBox(strAll);
	}