ode_gillvariationalstep.cpp

是《计算机常用数值计算算法与程序 C++版》一书的配套C++程序源代码文件

//ODE_GillVariationalStep.cpp	
//变步长积分一步基尔法

#include <iostream>							//输入输出流头文件
#include "OrdinaryDifferentialEguation.h"	//求解常微分方程(组)头文件
using namespace std;						//名字空间

void main(void)
{	
	double q[3] = {0.0, 0.0, 0.0};
	double y[3] = {0.0, 1.0, 1.0};
	double t(0.0), h(0.1), eps(FLOATERROR);
	valarray<double> vy(y, 3), vq(q, 3);
			
  	cout.setf(ios::fixed);	//输出数据为定点法
	cout.precision(6);		//精度6位

	cout << "t = " << t << endl;
	for(int i=0; i<3; i++)
		cout << "    y(" << i << ") = " << y[i] << "\t";
	cout << endl;

	for(i=1; i<11; i++)
	{
		ODE_GillVariationalStep(t,h,vy,eps,vq);
		t = h * i;
		cout << "t = " << t << endl;
		for(int j=0; j<3; j++)
			cout << "    y(" << j << ") = " << vy[j] << "\t";
		cout << endl;
    }
}

//计算微分方程组中各方程右端函数值
template <class _Ty>
void FunctionValueGVS(_Ty t, valarray<_Ty>& y, valarray<_Ty>& d)
{
	int n = y.size();	//微分方程组中方程的个数，也是未知函数的个数

    d[0] = y[1];
	d[1] = -y[0]; 
	d[2] = -y[2];
}