| Namespace MathEx.ODESolver | |
| Public Class bulirschstoer | |
| Public fc As fdelegate | |
| Delegate Sub fdelegate(ByVal y As Double(), ByRef dy As Double()) | |
| Sub New() | |
| End Sub | |
| Sub DefineFuncDelegate(ByVal func As fdelegate) | |
| Me.fc = func | |
| End Sub | |
| Sub f(ByVal y As Double(), ByRef dy As Double()) | |
| fc.Invoke(y, dy) | |
| End Sub | |
| Public Sub solvesystembulirschstoer(ByVal x1 As Double, ByVal x2 As Double, ByRef y As Double(), ByVal n As Integer, ByVal h As Double, ByVal err As Double, ByVal isabserr As Boolean) | |
| Dim ya As Double() = New Double() {} | |
| Dim yl As Double() = New Double() {} | |
| Dim ym As Double() = New Double() {} | |
| Dim dy As Double() = New Double() {} | |
| Dim dz As Double() = New Double() {} | |
| Dim s As Double() = New Double() {} | |
| Dim dt(,) As Double | |
| Dim d As Double() | |
| Dim yg(,) As Double | |
| Dim yh(,) As Double | |
| Dim konv As Boolean = False | |
| Dim bo As Boolean = False | |
| Dim bh As Boolean = False | |
| Dim fin As Boolean = False | |
| Dim i As Integer = 0 | |
| Dim j As Integer = 0 | |
| Dim k As Integer = 0 | |
| Dim kk As Integer = 0 | |
| Dim l As Integer = 0 | |
| Dim m As Integer = 0 | |
| Dim jj As Integer = 0 | |
| Dim r As Integer = 0 | |
| Dim sr As Integer = 0 | |
| Dim ta As Double = 0 | |
| Dim xxfin As Double = 0 | |
| Dim a As Double = 0 | |
| Dim b As Double = 0 | |
| Dim c As Double = 0 | |
| Dim b1 As Double = 0 | |
| Dim fc As Double = 0 | |
| Dim g As Double = 0 | |
| Dim ho As Double = 0 | |
| Dim u As Double = 0 | |
| Dim v As Double = 0 | |
| Dim cycleflag As Integer = 0 | |
| ya = New Double((n + 1)) {} | |
| yl = New Double((n + 1)) {} | |
| ym = New Double((n + 1)) {} | |
| dy = New Double((n + 1)) {} | |
| dz = New Double((n + 1)) {} | |
| s = New Double((n + 1)) {} | |
| dt = New Double((n + 1), 8) {} | |
| d = New Double(8) {} | |
| yg = New Double(11, (n + 1)) {} | |
| yh = New Double(111, (n + 1)) {} | |
| xxfin = x2 | |
| cycleflag = -1 | |
| Do While True | |
| If ((cycleflag = -1) Or (cycleflag = 22)) Then | |
| Me.f(y, (dz)) | |
| bh = False | |
| fin = False | |
| i = 1 | |
| Do While (i <= n) | |
| s(i) = 0 | |
| ya(i) = y(i) | |
| k = 1 | |
| Do While (k <= 7) | |
| dt(i, k) = 0 | |
| k += 1 | |
| Loop | |
| i += 1 | |
| Loop | |
| ho = h | |
| If ((x1 + h) >= xxfin) Then | |
| ho = (x2 - x1) | |
| fin = True | |
| End If | |
| End If | |
| If (((cycleflag = -1) Or (cycleflag = 20)) Or (cycleflag = 22)) Then | |
| a = (ho + x1) | |
| If (a = x1) Then | |
| a = a | |
| Return | |
| End If | |
| fc = 1.5 | |
| bo = False | |
| m = 1 | |
| r = 2 | |
| sr = 3 | |
| jj = 0 | |
| End If | |
| cycleflag = -1 | |
| j = 1 | |
| Do While (j <= 10) | |
| If bo Then | |
| d(2) = 1.7777777777778 | |
| d(4) = 7.1111111111111 | |
| d(6) = 28.444444444444 | |
| Else | |
| d(2) = 2.25 | |
| d(4) = 9 | |
| d(6) = 36 | |
| End If | |
| konv = False | |
| If (j > 3) Then | |
| konv = True | |
| End If | |
| If (j > 7) Then | |
| l = 7 | |
| d(7) = 64 | |
| fc = (0.6 * fc) | |
| Else | |
| l = j | |
| d(l) = (m * m) | |
| End If | |
| m = (m * 2) | |
| g = (ho / Convert.ToDouble(m)) | |
| b = (g * 2) | |
| If (bh And (j < 9)) Then | |
| i = 1 | |
| Do While (i <= n) | |
| ym(i) = yh(j, i) | |
| yl(i) = yg(j, i) | |
| i += 1 | |
| Loop | |
| Else | |
| kk = ((m - 2) / 2) | |
| m -= 1 | |
| i = 1 | |
| Do While (i <= n) | |
| yl(i) = ya(i) | |
| ym(i) = (ya(i) + (g * dz(i))) | |
| i += 1 | |
| Loop | |
| k = 1 | |
| Do While (k <= m) | |
| Me.f(ym, (dy)) | |
| i = 1 | |
| Do While (i <= n) | |
| u = (yl(i) + (b * dy(i))) | |
| yl(i) = ym(i) | |
| ym(i) = u | |
| u = Math.Abs(u) | |
| If (u > s(i)) Then | |
| s(i) = u | |
| End If | |
| i += 1 | |
| Loop | |
| If ((k = kk) And (k <> 2)) Then | |
| jj = (1 + jj) | |
| i = 1 | |
| Do While (i <= n) | |
| yh(jj, i) = ym(i) | |
| yg(jj, i) = yl(i) | |
| i += 1 | |
| Loop | |
| End If | |
| k += 1 | |
| Loop | |
| End If | |
| Me.f(ym, (dy)) | |
| i = 1 | |
| Do While (i <= n) | |
| v = dt(i, 1) | |
| dt(i, 1) = (((ym(i) + yl(i)) + (g * dy(i))) * 0.5) | |
| c = dt(i, 1) | |
| ta = c | |
| If (l >= 2) Then | |
| k = 2 | |
| Do While (k <= l) | |
| b1 = (d(k) * v) | |
| b = (b1 - c) | |
| u = v | |
| If (b <> 0) Then | |
| b = ((c - v) / b) | |
| u = (c * b) | |
| c = (b1 * b) | |
| End If | |
| v = dt(i, k) | |
| dt(i, k) = u | |
| ta = (u + ta) | |
| k += 1 | |
| Loop | |
| End If | |
| If (Not isabserr And (Math.Abs(Convert.ToDouble((y(i) - ta))) > (err * s(i)))) Then | |
| konv = False | |
| End If | |
| If (isabserr And (Math.Abs(Convert.ToDouble((y(i) - ta))) > err)) Then | |
| konv = False | |
| End If | |
| y(i) = ta | |
| i += 1 | |
| Loop | |
| If konv Then | |
| x1 = a | |
| h = (fc * h) | |
| If fin Then | |
| Return | |
| End If | |
| cycleflag = 22 | |
| Exit Do | |
| End If | |
| d(3) = 4 | |
| d(5) = 16 | |
| bo = Not bo | |
| m = r | |
| r = sr | |
| sr = (m * 2) | |
| j += 1 | |
| Loop | |
| If (cycleflag = -1) Then | |
| bh = Not bh | |
| ho = (ho * 0.5) | |
| h = ho | |
| fin = False | |
| cycleflag = 20 | |
| End If | |
| Loop | |
| End Sub | |
| End Class | |
| End Namespace |