pzextr.cpp

提供了4种解常微分方程组的c++代码：定步长四阶龙格-库塔(Runge-Kutta)法(RK4->RKDUMP)； 自适应变步长的龙格-库塔(Runge-Kutta)法(RKQC->ODE

void pzextr(int iest, double xest,double yest[], double yz[],double dy[],int nv,int nuse)
{
    static double x[12], qcol[11][ 8];
	int j,ncol,nmax,m1,k1;
	double delta,f1,f2,q;
    ncol = 7;
    nmax = 10;
    double d[11];
    x[iest] = xest;
    for (j = 1; j<=nv; j++)
	{
        dy[j] = yest[j];
        yz[j] = yest[j];
    }
    if (iest == 1)
	{
        for (j = 1; j<=nv; j++)
		{
            qcol[j][1] = yest[j];
        }
	}
    else
	{
        m1 = iest;
        if (iest > nuse) m1 = nuse;
        for (j = 1; j<=nv; j++)
		{
            d[j] = yest[j];
		}
        for (k1 = 1; k1<=m1 - 1; k1++)
		{
            delta = 1.0 / (x[iest - k1] - xest);
            f1 = xest * delta;
            f2 = x[iest - k1] * delta;
            for (j = 1; j<=nv; j++)
			{
                q = qcol[j][k1];
                qcol[j][k1] = dy[j];
                delta = d[j] - q;
                dy[j] = f1 * delta;
                d[j] = f2 * delta;
                yz[j] = yz[j] + dy[j];
            }
        }
        for (j = 1; j<=nv; j++)
		{
            qcol[j][m1] = dy[j];
        }
    }
    for (j = 1; j<=10; j++)
	{
    d[j]=0.0;
	}
}