package Others;
public class GuassLegendre {
public static void main(String[] args) {
for (int i = 1; i <= 3; ++i) System.out.println(pi(i));
}
static double pi(int l) {
double a = 1, b = Math.pow(2, -0.5), t = 0.25, p = 1;
for (int i = 0; i < l; ++i) {
double temp[] = update(a, b, t, p);
a = temp[0];
b = temp[1];
t = temp[2];
p = temp[3];
}
return Math.pow(a + b, 2) / (4 * t);
}
static double[] update(double a, double b, double t, double p) {
double values[] = new double[4];
values[0] = (a + b) / 2;
values[1] = Math.sqrt(a * b);
values[2] = t - p * Math.pow(a - values[0], 2);
values[3] = 2 * p;
return values;
}
}