ludcmp.txt

VB常用数值算法集1 VB常用数值算法集1

Sub LUDCMP(A(), N, INDX(), D)
    NMAX = 100
    TINY = 1E-20
    Dim VV(100)
    D = 1#
    For I = 1 To N
        AAMAX = 0#
        For J = 1 To N
            If Abs(A(I, J)) > AAMAX Then AAMAX = Abs(A(I, J))
        Next J
        If AAMAX = 0# Then Print "Singular matrix."
        VV(I) = 1# / AAMAX
    Next I
    For J = 1 To N
        If J > 1 Then
            For I = 1 To J - 1
                Sum = A(I, J)
                If I > 1 Then
                    For K = 1 To I - 1
                        Sum = Sum - A(I, K) * A(K, J)
                    Next K
                    A(I, J) = Sum
                End If
            Next I
        End If
        AAMAX = 0#
        For I = J To N
            Sum = A(I, J)
            If J > 1 Then
                For K = 1 To J - 1
                    Sum = Sum - A(I, K) * A(K, J)
                Next K
                A(I, J) = Sum
            End If
            DUM = VV(I) * Abs(Sum)
            If DUM >= AAMAX Then
                IMAX = I
                AAMAX = DUM
            End If
        Next I
        If J <> IMAX Then
            For K = 1 To N
                DUM = A(IMAX, K)
                A(IMAX, K) = A(J, K)
                A(J, K) = DUM
            Next K
            D = -D
            VV(IMAX) = VV(J)
        End If
        INDX(J) = IMAX
        If J <> N Then
            If A(J, J) = 0# Then A(J, J) = TINY
            DUM = 1# / A(J, J)
            For I = J + 1 To N
                A(I, J) = A(I, J) * DUM
            Next I
        End If
    Next J
    If A(N, N) = 0# Then A(N, N) = TINY
End Sub