东南大学 数值分析 第三章高斯消元 VB编程.doc

第3章 （vb编程）39、列主元高斯消去法（1）通用程序：Public Function guass(n As Integer, a() As Single, b() As Single, x() As Single)Dim i As Integer, j As Integer, k As IntegerDim amax As Single, imax As Integer, s As SingleDim m As Single, t As Single, mm As SingleFor j = 1 To (n - 1)amax = Abs(a(j, j)imax = j比较对应于主元所在列中的各行数的绝对值大小For i = j + 1 To nIf (Abs(a(i, j) amax) Thenamax = Abs(a(i, j)imax = iEnd IfNext i 比较完毕将在主元所在列中绝对值比主元大的数对应的行与主元所在行互换If (imax j) ThenFor k = j To nt = a(imax, k)a(imax, k) = a(j, k)a(j, k) = tNext kbmax = b(imax)b(imax) = b(j)b(j) = bmaxEnd If互换完毕消去对应主元所在列的元For i = j + 1 To nt = 1# / a(j, j)t = t * a(i, j)For k = j To na(i, k) = a(i, k) - a(j, k) * tNext kb(i) = b(i) - b(j) * tNext i消元完毕Next j判断是否有等价方程，如果有则显示“无穷多解”For i = 1 To nm = 0mm = 0For j = i To nm = m + a(i, j)mm = mm - a(i, j)Next jIf (m 0.000001 And mm 0.000001) ThenMsgBox 无穷多解EndEnd IfNext i判断完毕回代，求解xx(n) = b(n) / a(n, n)For i = n - 1 To 1 Step -1m = 0For j = n To i + 1 Step -1m = m + a(i, j) * x(j)Next jx(i) = (b(i) - m) / a(i, i)Next i求解x 完毕End FunctionPrivate Sub Command2_Click()EndEnd SubPrivate Sub Command1_Click()Dim s() As Single, x() As SingleDim a() As Single, b() As SingleDim i As Integer, j As Integer, k As IntegerDim amax As Single, imax As IntegerDim m As Single, n As Integer, c As SingleDim p As StringIf Text1.Text = ThenMsgBox (请输入系数矩阵的阶数)Else:again:n = Val(Text1.Text)ReDim a(n, n) As SingleReDim b(n) As Single, x(n) As Single输入并在相应图框中输出系数矩阵a(i,j)For i = 1 To nFor j = 1 To na(i, j) = Val(InputBox(系数矩阵a( & i & & j & )数值:, 输入框)Picture1.Print a(i, j); vbTab; ;Next jPicture1.Print Chr(13)Next i系数矩阵a(i,j)读入完毕输入并在相应图框中输出矩阵b(j)For i = 1 To nb(i) = Val(InputBox(列向量b( & i & )数值:, 输入框)Picture2.Print b(i); ;Picture2.Print Chr(13)Next i矩阵b(j)读入完毕Call guass(n, a, b, x) 调用求解函数输出计算结果For j = 1 To np = x( & Str(j) & )= & Format(Str(x(j), #0.0000)Picture3.Print p; ;Picture3.Print Chr(13)Next j计算结果输出完毕On Error GoTo again:End IfEnd SubPrivate Sub Command3_Click()Picture1.Cls