d4r25.frm

来自「常用数值算法集哈」· FRM 代码 · 共 187 行

VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "Form1"
   ClientHeight    =   2865
   ClientLeft      =   60
   ClientTop       =   345
   ClientWidth     =   4140
   LinkTopic       =   "Form1"
   ScaleHeight     =   2865
   ScaleWidth      =   4140
   StartUpPosition =   3  'Windows Default
   Begin VB.CommandButton Command1 
      Caption         =   "Command1"
      Height          =   375
      Left            =   2400
      TabIndex        =   0
      Top             =   2280
      Width           =   1455
   End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Private Sub Command1_Click()
    'PROGRAM D4R25
    'Driver for routine BESSK
    Dim ACTUAL(5), X(5), N(5)
    ACTUAL(1) = 49.5124
    ACTUAL(2) = 7.10126
    ACTUAL(3) = 0.00829177
    ACTUAL(4) = 9.43105
    ACTUAL(5) = 9.75856
    N(1) = 2
    N(2) = 3
    N(3) = 3
    N(4) = 5
    N(5) = 10
    X(1) = 0.2
    X(2) = 1
    X(3) = 5
    X(4) = 2
    X(5) = 5
    Print
    Print "   N     X       Actual          BESSK(X)"
    For I = 1 To 5
        Print Tab(4); Format$(N(I), "#0.##");
        Print Tab(10); Format$(X(I), "#0.##");
        Print Tab(16); Format$(ACTUAL(I), ".000000E+00");
        Print Tab(32); Format$(BESSK(N(I), X(I)), ".000000E+00")
    Next I
End Sub
Function BESSK(N, X)
    If N < 2 Then
        Print "bad argument N in BESSK"
        Exit Function
    End If
    TOX = 2# / X
    BKM = BESSK0(X)
    BK = BESSK1(X)
    For J = 1 To N - 1
        BKP = BKM + J * TOX * BK
        BKM = BK
        BK = BKP
    Next J
    BESSK = BK
End Function
Function BESSK0(X)
    P1 = -0.57721566
    P2 = 0.4227842
    P3 = 0.23069756
    P4 = 0.0348859
    P5 = 0.00262698
    P6 = 0.0001075
    P7 = 0.0000074
    Q1 = 1.25331414
    Q2 = -0.07832358
    Q3 = 0.02189568
    Q4 = -0.01062446
    Q5 = 0.00587872
    Q6 = -0.0025154
    Q7 = 0.00053208
    If X <= 2# Then
        Y# = X * X / 4#
        BBB = Y * (P5 + Y * (P6 + Y * P7))
        AAA# = P1 + Y * (P2 + Y * (P3 + Y * (P4 + BBB)))
        BESSK0 = (-Log(X / 2#) * BESSI0(X)) + AAA#
    Else
        Y# = (2# / X)
        BBB = Y * (Q5 + Y * (Q6 + Y * Q7))
        AAA# = Q1 + Y * (Q2 + Y * (Q3 + Y * (Q4 + BBB)))
        BESSK0 = (Exp(-X) / Sqr(X)) * AAA#
    End If
End Function
   Function BESSK1(X)
      P1 = 1#
      P2 = 0.15443144
      P3 = -0.67278579
      P4 = -0.18156897
      P5 = -0.01919402
      P6 = -0.00110404
      P7 = -0.00004686
      Q1 = 1.25331414
      Q2 = 0.23498619
      Q3 = -0.0365562
      Q4 = 0.01504268
      Q5 = -0.00780353
      Q6 = 0.00325614
      Q7 = -0.00068245
      If X <= 2# Then
          Y# = X * X / 4#
          AAA# = Log(X / 2#) * BESSI1(X)
          CCC# = Y * (P5 + Y * (P6 + Y * P7))
          BBB# = P1 + Y * (P2 + Y * (P3 + Y * (P4 + CCC#)))
          BESSK1 = AAA# + (1# / X) * BBB#
      Else
          Y = (2# / X)
          BBB# = Y * (Q5 + Y * (Q6 + Y * Q7))
          AAA# = Q1 + Y * (Q2 + Y * (Q3 + Y * (Q4 + BBB#)))
          BESSK1 = (Exp(-X) / Sqr(X)) * AAA#
      End If
   End Function
   Function BESSI0(X)
      P1 = 1#
      P2 = 3.5156229
      P3 = 3.0899424
      P4 = 1.2067492
      P5 = 0.2659732
      P6 = 0.0360768
      P7 = 0.0045813
      Q1 = 0.39894228
      Q2 = 0.01328592
      Q3 = 0.00225319
      Q4 = -0.00157565
      Q5 = 0.00916281
      Q6 = -0.02057706
      Q7 = 0.02635537
      Q8 = -0.01647633
      Q9 = 0.00392377
      If Abs(X) < 3.75 Then
          Y = (X / 3.75) ^ 2
          AAA = Y * (P5 + Y * (P6 + Y * P7))
          BESSI0 = P1 + Y * (P2 + Y * (P3 + Y * (P4 + AAA)))
      Else
          AX = Abs(X)
          Y = 3.75 / AX
          AAA = Exp(AX) / Sqr(AX)
          BBB = Q4 + Y * (Q5 + Y * (Q6 + Y * (Q7 + Y * (Q8 + Y * Q9))))
          BESSI0 = AAA * (Q1 + Y * (Q2 + Y * (Q3 + Y * BBB)))
      End If
   End Function
   Function BESSI1(X)
      P1 = 0.5
      P2 = 0.87890594
      P3 = 0.51498869
      P4 = 0.15084934
      P5 = 0.02658733
      P6 = 0.00301532
      P7 = 0.00032411
      Q1 = 0.39894228
      Q2 = -0.03988024
      Q3 = -0.00362018
      Q4 = 0.00163801
      Q5 = -0.01031555
      Q6 = 0.02282967
      Q7 = -0.02895312
      Q8 = 0.01787654
      Q9 = -0.00420059
      If Abs(X) < 3.75 Then
          Y = (X / 3.75) ^ 2
          AAA = Y * (P4 + Y * (P5 + Y * (P6 + Y * P7)))
          BESSI1 = X * (P1 + Y * (P2 + Y * (P3 + AAA)))
      Else
          AX = Abs(X)
          Y = 3.75 / AX
          AAA = Exp(AX) / Sqr(AX)
          BBB = Y * (Q5 + Y * (Q6 + Y * (Q7 + Y * (Q8 + Y * Q9))))
          BESSI1 = AAA * (Q1 + Y * (Q2 + Y * (Q3 + Y * (Q4 + BBB))))
      End If
   End Function