d14r4.txt

JAVA数值计算算法集随书源码

import java.text.*;
public class d14r4
{
	public static void main (String[] args)
	{
		//program d14r4
		//driver for routine odeint
		int i, nvar;
		double vstart[] = new double[5];
		double xp[] = new double[201];
		double yp[][] = new double[10][201];
		double x1, x2, eps, h1, hmin, nok, nbad;
		d14r4F g = new d14r4F();
		DecimalFormat form = new DecimalFormat("0.000000");
		nvar = 4;
		x1 = 1.0;
		x2 = 10.0;
		vstart[1] = g.bessj0(x1);
		vstart[2] = g.bessj1(x1);
		vstart[3] = g.bessj(2, x1);
		vstart[4] = g.bessj(3, x1);
		eps = 0.0001;
		h1 = 0.1;
		hmin = 0.0;
		int kmax = 100;
		double dxsav = (x2 - x1) / 20.0;
		g.kmax = kmax;
		g.dxsav = dxsav;
		nok = 0; nbad = 0;
		g.odeint(vstart, nvar, x1, x2, eps, h1, hmin, nok, nbad, xp, yp);
		eps = g.odeint_eps; h1 = g.odeint_h1; hmin = g.odeint_hmin;
		nbad = g.odeint_nbad; nok = g.odeint_nok; nvar = g.odeint_nvar;
		x1 = g.odeint_x1; x2 = g.odeint_x2;  
		g.kmax = kmax;
		g.dxsav = dxsav;
		System.out.println();
		System.out.println("Successful step: "+nok);
		System.out.println("Bad step: " + nbad);
		System.out.println("Stored intermediate values: " + g.kount);
		System.out.println();
        System.out.println("      x         Integral     Bessj(3,x)");
        for (i = 1; i <= g.kount; i++)
		{
            System.out.print("  "+form.format(xp[i]) + "    ");
            System.out.print(form.format(yp[4][i]) + "    ");
            System.out.println(form.format(g.bessj(3, xp[i])));
		}
	}
}
public class d14r4F 
{
	void derivs(double x,double y1[],double dydx[])
	{
		dydx[1] = -y1[2];
		dydx[2] = y1[1] - (1.0 / x) * y1[2];
		dydx[3] = y1[2] - (2.0 / x) * y1[3];
		dydx[4] = y1[3] - (3.0 / x) * y1[4];
	}
}