nlnewtonamainmodule.bas

科学与工程数值计算算法（Visual Basic版） 附赠的光盘包含了本书中全部的源代码

Attribute VB_Name = "MainModule"
Sub Main()
    Dim n As Integer, nMaxIt As Integer
    Dim t As Double, h As Double
    Dim s As String
    
    ' 3次方程
    n = 3
    
    ' 分配初值和解的内存
    ReDim x(n) As Double
    
    ' 初值数组
    x(1) = 1
    x(2) = 1
    x(3) = 1
    
    ' 最大迭代次数
    nMaxIt = 100
    
    ' 增量及控制参数
    t = 0.1
    h = 0.1
    
    '求解
    If NLNewtonA(n, x, nMaxIt, 0.0000001, h, t) Then
        s = ""
        For i = 1 To n
            s = s & "x(" & i & ") = " & x(i) & Chr(13)
        Next i
        
        MsgBox "求解成功！" & Chr(13) & Chr(13) & s
    Else
        MsgBox "求解失败"
    End If
    
End Sub

Sub Func(x() As Double, y() As Double)
    y(1) = x(1) * x(1) + x(2) * x(2) + x(3) * x(3) - 1#
    y(2) = 2# * x(1) * x(1) + x(2) * x(2) - 4# * x(3)
    y(3) = 3# * x(1) * x(1) - 4# * x(2) + x(3) * x(3)
End Sub