public static (double Y, double Error, int Iterations) Step2(
Func <double, double, double> f,
double t, double dt,
double y, double YPrev1, double YPrev2,
double Eps, int IterationsCount)
{
double y1 = AdamsBashforth.Step2(f, t, dt, y, YPrev1, YPrev2), y2, delta;
var t1 = t + dt;
var t_1 = t - dt;
var t_2 = t - 2 * dt;
var i = 0;
do
{
y2 = y + dt * (
9 / 24d * f(t1, y1) +
19 / 24d * f(t, y) -
5 / 24d * f(t_1, YPrev1) +
24 / 24d * f(t_2, YPrev2));
delta = y2 - y1;
y1 = y2;
}while (Abs(delta) > Eps && i++ < IterationsCount);
return(y2, delta, i);
}
public static (double Y, double Error, int Iterations) Step3(
Func <double, double, double> f,
double t, double dt,
double y, double YPrev1, double YPrev2, double YPrev3,
double Eps, int IterationsCount)
{
double y1 = AdamsBashforth.Step3(f, t, dt, y, YPrev1, YPrev2, YPrev3), y2, delta;
var t1 = t + dt;
var t_1 = t - dt;
var t_2 = t - 2 * dt;
var t_3 = t - 3 * dt;
var i = 0;
do
{
y2 = y + dt * (
251 / 720d * f(t1, y1) +
646 / 720d * f(t, y) -
264 / 720d * f(t_1, YPrev1) +
106 / 720d * f(t_2, YPrev2) -
19 / 720d * f(t_3, YPrev3));
delta = y2 - y1;
y1 = y2;
}while (Abs(delta) > Eps && i++ < IterationsCount);
return(y2, delta, i);
}
public static (double Y, double Error, int Iterations) Step0(
Func <double, double, double> f,
double t, double dt,
double y,
double Eps, int IterationsCount)
{
double y1 = AdamsBashforth.Step0(f, t, dt, y), y2, delta;
var t1 = t + dt;
var i = 0;
do
{
y2 = y + dt * (
0.5 * f(t1, y1) +
0.5 * f(t, y));
delta = y2 - y1;
y1 = y2;
}while (Abs(delta) > Eps && i++ < IterationsCount);
return(y2, delta, i);
}