qgaus.cpp

数值积分常用算法

void qgaus(double a, double b, double& ss)
{
	double xm,xr,dx;
    double x[6], w[6];
    x[1] = 0.1488743389;
    x[2] = 0.4333953941;
    x[3] = 0.6794095682;
    x[4] = 0.8650633666;
    x[5] = 0.9739065285;
    w[1] = 0.2955242247;
    w[2] = 0.2692667193;
    w[3] = 0.2190863625;
    w[4] = 0.1494513491;
    w[5] = 0.0666713443;
    xm = 0.5 * (a + b);
    xr = 0.5 * (b - a);
    ss = 0.0;
    for (int j = 1; j<=5; j++)
	{
        dx = xr * x[j];
        ss = ss + w[j] * (func(xm + dx) + func(xm - dx));
    }
    ss = xr * ss;
}