rtnewt.cpp

来自「工程算法 这是一个很有用的工程数值算法集锦」· C++ 代码 · 共 27 行

double  rtnewt(double x1, double x2,double xacc)
{
	int jmax,j;
	double temp1,f,df,dx;
    jmax = 20;
    temp1 = 0.5 * (x1 + x2);
	 for (j = 1; j<=jmax; j++)
	{
        funcd(temp1, f, df);
        dx = f / df;
        temp1 = temp1 - dx;
        if ((x1 - temp1) * (temp1 - x2) < 0 )
		{
            cout<< "jumped out of brackets"<<endl;
			return temp1;
            _c_exit();
        }
        if (fabs(dx) < xacc) 
		{
			return temp1;
            _c_exit();
		}
    }
    cout<< "rtnewt exceeding maximum iterations."<<endl;
	return 1;
}