d4r26.frm

VB常用数值算法集 内含有解线性代数方程组

VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "Form1"
   ClientHeight    =   6900
   ClientLeft      =   2055
   ClientTop       =   540
   ClientWidth     =   5280
   LinkTopic       =   "Form1"
   ScaleHeight     =   6900
   ScaleWidth      =   5280
   Begin VB.CommandButton Command1 
      Caption         =   "Command1"
      Height          =   375
      Left            =   3360
      TabIndex        =   0
      Top             =   6240
      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 D4R26
    'Driver for routine BESSI
    Open "D:\VB常用数值算法集\DATA\FNCVAL.DAT" For Input As #1
    Do
      Line Input #1, Text$
      Text$ = Left(Text$, 27)
    Loop While Text$ <> "Modified Bessel Function In"
    Line Input #1, NVAL$
    NVAL = Val(NVAL$)
    Print Text$
    Print
    Print "   N     X       Actual         BESSI(N,X)"
    For I = 1 To NVAL
        Line Input #1, DUM$
        N = Val(Mid(DUM$, 1, 6))
        X = Val(Mid(DUM$, 7, 6))
        Value = Val(Mid(DUM$, 13))
        Print Tab(4); Format$(N, "#0.##");
        Print Tab(10); Format$(X, "#0.##");
        Print Tab(16); Format$(Value, ".000000E+00");
        Print Tab(32); Format$(BESSI(N, X), ".000000E+00")
    Next I
    Close #1
End Sub
Function BESSI(N, X)
    IACC = 40
    BIGNO = 10000000000#
    BIGNI = 0.0000000001
    If N < 2 Then Print "bad argument N in BESSI"
    TOX = 2# / X
    BIP = 0#
    BI = 1#
    BESSI = 0#
    M = 2 * ((N + Int(Sqr(IACC * N))))
    For J = M To 1 Step -1
        BIM = BIP + J * TOX * BI
        BIP = BI
        BI = BIM
        If Abs(BI) > BIGNO Then
            BESSI = BESSI * BIGNI
            BI = BI * BIGNI
            BIP = BIP * BIGNI
        End If
        If J = N Then BESSI = BIP
    Next J
    BESSI = BESSI * BESSI0(X) / BI
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