public static void RungeKutta4(ODE ode, double ds)
{
var s = ode.IndependentVariable;
var q = ode.GetAllDependentVariables();
var dq1 = ode.GetRightHandSide(s, q, q, ds, 0.0);
var dq2 = ode.GetRightHandSide(s + .5 * ds, q, dq1, ds, .5);
var dq3 = ode.GetRightHandSide(s + .5 * ds, q, dq2, ds, .5);
var dq4 = ode.GetRightHandSide(s + ds, q, dq3, ds, 1.0);
ode.IndependentVariable = s + ds;
for (var i = 0; i < ode.NumberOfEquationsToSolve; i++)
{
q[i] = q[i] + (dq1[i] + 2.0 * dq2[i] + 2.0 * dq3[i] + dq4[i]) / 6.0;
ode.SetDependentVariable(i, q[i]);
}
}
// Fourth-order Runge-Kutta ODE solver.
public static void RungeKutta4(ODE ode, double ds) //ds represent the increment (e.g., time)
// Define some convenience variables to make the
// code more readable
{
int j;
int numEqns = ode.NumEqns;
double s;
double[] q;
double[] dq1 = new double[numEqns];
double[] dq2 = new double[numEqns];
double[] dq3 = new double[numEqns];
double[] dq4 = new double[numEqns];
// Retrieve the current values of the dependent
// and independent variables.
s = ode.S;
q = ode.GetAllQ();
// Compute the four Runge-Kutta steps, The return
// value of getRightHandSide method is an array of
// delta-q values for each of the four steps.
dq1 = ode.GetRightHandSide(s, q, q, ds, 0.0);
dq2 = ode.GetRightHandSide(s + 0.5 * ds, q, dq1, ds, 0.5);
dq3 = ode.GetRightHandSide(s + 0.5 * ds, q, dq2, ds, 0.5);
dq4 = ode.GetRightHandSide(s + ds, q, dq3, ds, 1.0);
// Update the dependent and independent variable values
// at the new dependent variable location and store the
// values in the ODE object arrays.
ode.S = s + ds;
for (j = 0; j < numEqns; ++j)
{
q[j] = q[j] + (dq1[j] + 2.0 * dq2[j] + 2.0 * dq3[j] + dq4[j]) / 6.0;
ode.SetQ(q[j], j);
}
return;
}
// Fourth-order Runge-Kutta ODE solver.
public static void RungeKutta4(ODE ode, double ds)
{
// 방정식 풀이를 위한 변수들 정의
int j;
int numEqns = ode.NumEqns;
double s;
double[] q;
double[] dq1 = new double[numEqns];
double[] dq2 = new double[numEqns];
double[] dq3 = new double[numEqns];
double[] dq4 = new double[numEqns];
// 현재 종속 변수와 독립 변수를 찾음
s = ode.S; //독립변수
q = ode.GetAllQ(); // 종속 변수
// 4개의 Runge-Kutta 단계를 계산합니다.
// getRightHandSide 메서드의 반환 값은 각 4단계에 대한 델타-q 값의 배열입니다.
// 0.5, 1.0 등은 가중치를 나타내고 있음
dq1 = ode.GetRightHandSide(s, q, q, ds, 0.0);
dq2 = ode.GetRightHandSide(s + 0.5 * ds, q, dq1, ds, 0.5);
dq3 = ode.GetRightHandSide(s + 0.5 * ds, q, dq2, ds, 0.5);
dq4 = ode.GetRightHandSide(s + ds, q, dq3, ds, 1.0);
// 새 종속 변수 위치에서 종속 변수 및 독립 변수 값을 업데이트하고
// 값을 ODE 객체 배열에 저장합니다.
ode.S = s + ds;
for (j = 0; j < numEqns; ++j)
{
q[j] = q[j] + (dq1[j] + 2.0 * dq2[j] + 2.0 * dq3[j] + dq4[j]) / 6.0;
ode.SetQ(q[j], j);
}
return;
}