BP神经网络实例含源码

1、BP神经网络实例含源码BP神经网络算法实现一：关于BP网络BP (Back Propagation)神经网络，即误差反传误差反向传播算法的学习过程，由信息的正向传播和误差的反向传播两个过程组成。输入层各神经元负责接收 来自外界的输入信息，并传递给中间层各神经元；中间层是内部信息处理层，负责 信息变换，根据信息变化能力的需求，中间层可以设计为单隐层或者多隐层结构；最后一个隐层传递到输出层各神经元的信息，经进一步处理后，完成一次学习的正 向传播处理过程，由输出层向外界输出信息处理结果。当实际输出与期望输出不符时，进入误差的反向传播阶段。误差通过输出层， 按误差梯度下降的方式修正各层权值，向隐层、输

2、入层逐层反传。周而复始的信息 正向传播和误差反向传播过程，是各层权值不断调整的过程，也是神经网络学习训 练的过程，此过程一直进行到网络输出的误差减少到可以接受的程度，或者预先设 定的学习次数为止。BP网络主要应用于以下方面：函数逼近、模式识别和分类、数据压缩。 BP神经 网络有较强的泛化性能，使网络平滑的逼近函数，能合理的响应被训练以外的输 入。同时，BP网络又有自己的限制与不足，主要表现在：需要较长的训练时间、网 络训练的结果可能使得权值逼近局部最优、训练数据范围外的数据泛化能力较差。为了避免训练陷入局部最优解，本程序采用改进的BP网络训练，既加入动量因子，使得网络在最优解附近有一定的震荡，

3、跳出局部最优的范围。BP网络训练中学习速率与动量因子的选择很重要，在后面的内容中将进行详细 的讨论。二：训练的函数程序中训练的函数为一个三输入一输出的非线性函数，如下所示x3xR,yxxe, , , , 2sin() , , 12网络结构为：35 1三：程序及相关界面(VB)1主界面1代码：Private Sub Command1_Click() form2.Visible = FalseForm3.Visible = TrueEnd SubPrivate Sub Command2_Click() form2.Visible = FalseForm1.Visible = TrueEnd Sub

4、Private Sub Command3_Click() form2.Visible = FalseForm4.Visible = TrueEnd SubPrivate Sub Command4_Click() form2.Visible = FalseForm5.Visible = TrueEnd SubPrivate Sub Command5_Click() EndEnd SubPrivate Sub Form_Load() Command3.Enabled = False Command4.Enabled =False End Sub2查看网络结构2代码：Private Sub Comm

5、and1_Click()Form3.Visible = False form2.Visible = True End Sub3网络训练代码：3Private Sub Command1_Click()Forml.Visible = Falseform2.Visible = TrueEnd SubPrivate Sub Command2_Click()Label2.Caption ="样本训练中”Dim i As Integer, j As Integer, k As Integer, p As Integer, s AsSingleDim Maxx(1 To 3) As Single,

6、 Minx(1 To 3) As Single, Meanx(1 To 3) AsSingleDim x(1 To 3, 1 To 100) As Single, sumx(1 To 3) As Single, Temp AsSingleDim Datex(1 To 3, 1 To 100) As Single, inputx(1 To 3) As Single, outputx(1 To 100) As SingleDim Ex(1 To 100) As SingleDim time(1 To 5000) As Integer, cishu(1 To 100) As IntegerDim D

7、v_1(1 To 5, 1 To 3) As Single, Dw_1(1 To 5) As SingleDim R As SingleDim Maxd As Single, Mind As SingleDim s1(1 To 5) As Single, y1(1 To 5, 1 To 100) As Single, s2 AsSingle, y2(1 To 100) As SingleDim deltW(1 To 100) As Single, deltV(1 To 5, 1 To 100) As SingleDim Dw(1 To 5) As Single, Dv(1 To 5, 1 To

8、 3) As SingleDim MyIn(1 To 3) As SingleDim Errorx(1 To 5000) As SingleRandomizeFor i = 1 To 3Maxx(i) = 0Minx(i) = 0Meanx(i) = 0Next iTemp = 0Maxd = 0Mind = 0For i = 1 To 5For j = 1 To 3Dv_1(i, j) = 0v(i, j) = 2 * Rnd - 1Next jDw_1(i) = 0w(i) = 2 * Rnd - 1Next iForj = 1 To 3For i = 1 To 100x(j, i) =

9、4 * (2 * Rnd - 1)Next isumx(j) = 0Next j,求最值Forj = 1 To 3For i = 1 To 100If x(j, i) >= Maxx(j) ThenMaxx(j) = x(j, i)End IfIf x(j, i) <= Minx(j) ThenMinx(j) = x(j, i)Temp = Temp + x(j, i)End IfNext isumx(j) = Temp4Temp = 0Meanx(j) = sumx(j) / 100 Next j'归一化Forj = 1 To 3For i = 1 To 100If Ma

10、xx(j) - x(j, i) >= x(j, i) - Minx(j) ThenR = Maxx(j) - x(j, i)ElseR = x(j, i) - Minx(j)End IfDatex(j, i) = (x(j, i) - Meanx(j) / RNext iNext j'期望输出For i = 1 To 100Forj = 1 To 3inputx(j) = Datex(j, i)Next joutputx(i) = 2 * (inputx(1) + Sin(inputx(2) + Exp(inputx(3)Next i'输出归一化For i = 1 To

11、100If Maxd <= outputx(i) ThenMaxd = outputx(i)End IfIf Mind >= outputx(i) ThenMind = outputx(i)End IfNext iFor i = 1 To 100Ex(i) = (outputx(i) - Mind) / (Maxd - Mind)Next i'训练For s = 1 To 5000 Step 1time(s) = sFor p = 1 To 100cishu(p) = pFori = 1 To 3MyIn(i) = Datex(i, p)Next iFor i = 1 To

12、 5Forj = 1 To 3Temp = Temp + v(i, j) * MyIn(j)Next js1(i) = TempTemp = 0Next iFori = 1 To 5y1(i, p) = 1 / (1 + Exp(-s1(i)Next iFori = 1 To 3Temp = y1(i, p) * w(i) + TempNext is2 = TempTemp = 0y2(p) = 1 / (1 + Exp(-s2)deltW(p) = (Ex(p) - y2(p) * y2(p) * (1 - y2(p)For i = 1 To 5deltV(i, p) = deltW(p)

13、* w(i) * y1(i, p) * (1 - y1(i, p)Next iNext p误差For i = 1 To 100Temp = Temp + (Ex(i) - y2(i) A 2Next iErrorx(s) = TempTemp = 0'调整权值For i = 1 To 5Dw_1(i) = Dw(i)Next iFori = 1 To 5For j = 1 To 100Temp = Temp + deltW(j) * y1(i, j)Next jDw(i) = TempTemp = 0Next iFor i = 1 To 5Forj = 1 To 3Dv_1(i, j)

14、 = Dv(i, j)Next jNext iFor i = 1 To 5Forj = 1 To 3For k = 1 To 100Temp = Temp + deltV(i, k) * Datex(j, k)Next kDv(i, j) = TempTemp = 0Next jNext iFor i = 1 To 5w(i) = 0.2 * Dw(i) + 0.2 * Dw_1(i) + w(i)Next iFori = 1 To 3Forj = 1 To 5v(j, i) = 0.2 * Dv(j, i) + 0.2 * Dv_1(j, i) + v(j, i)Next jNext i&#

15、39;画图Picture1.ClsPicture1.ScaleTop = 1.5Picture1.ScaleHeight = -2Picturel.ScaleLeft = -10Picturel.ScaleWidth = 120Picturel.Line (-9, 0)-(110, 0)Picturel.Line (0, 0)-(0, 1.5)For i = 1 To 100Picture1.PSet (cishu(i), Ex(i), RGB(128, 128, 0)Picture1.PSet (cishu(i), y2(i), RGB(128, 0, 0)Next iFor i = 1 T

16、o 99Picture1.Line (cishu(i), Ex(i)-(cishu(i + 1), Ex(i + 1), RGB(128, 128, 0)Picture1.Line (cishu(i), y2(i)-(cishu(i + 1), y2(i + 1), RGB(128, 0, 0)6Next i延时For j = 1 To 1000For k = 1 To 50Next kNext jPicture2.ClsPicture2.Print sDoEventsNext sLabel2.Caption =""form2.Command3.Enabled = True

17、 form2.Command4.Enabled = True ' 泛化Dim test(1 To 3, 1 To 20) As Single, sumE(1 To 3) As SingleDim MaxE(1 To 3) As Single, MinE(1 To 3) As Single, MeanE(1 To 3) AsSingleDim MaxxE As Single, MinxE As Single Dim des(1 To 3) As Single,outE(1 To 20) As SingleDim MIn(1 To 3) As Single, s11(1 To 5) As

18、Single, y11(1 To 5, 1 To20) As Single, s22 As SingleDim DateE(1 To 3, 1 To 20) As SingleFor i = 1 To 20Forj = 1 To 3test(j, i) = 4 * (2 * Rnd - 1)Next jNext iForj = 1 To 3For i = 1 To 20If test(j, i) >= MaxE(j) ThenMaxE(j) = test(j, i)End IfIf test(j, i) <= MinE(j) ThenMinE(j) = test(j, i)Temp

19、 = Temp + test(j, i)End IfNext isumE(j) = TempTemp = 0MeanE(j) = sumE(j) / 100Next j'归一化Forj = 1 To 3For i = 1 To 20If MaxE(j) - test(j, i) >= test(j, i) - MinE(j) ThenR = MaxE(j) - test(j, i)ElseR = test(j, i) - MinE(j)End IfDateE(j, i) = (test(j, i) - MeanE(j) / RNext iNext j'求输出For p =

20、 1 To 20Ti(p) = pFori = 1 To 3MIn(i) = DateE(i, p)Next iFor i = 1 To 5Forj = 1 To 3Temp = Temp + v(i, j) * MIn(j)Next js11(i) = TempTemp = 0Next iFor i = 1 To 5y11(i, p) = 1 / (1 + Exp(-s11(i)Next iFori = 1 To 3Temp = y11(i, p) * w(i) + TempNext is22 = TempTemp = 0y22(p) = 1 / (1 + Exp(-s22)Next p,输

21、出及归一化For j = 1 To 20Fori = 1 To 3des(i) = DateE(i, j)Next ioutE(j) = 2 * (des(1) + Sin(des(2) + Exp(des(3)Next j'输出归一化For i = 1 To 20If MaxxE <= outE(i) ThenMaxxE = outE(i)End IfIf MinxE >= outE(i) ThenMinxE = outE(i)End IfNext iFor i = 1 To 20outD(i) = (outE(i) - MinxE) / (MaxxE - MinxE)N

22、ext iEnd Sub4查看训练结果代码:Private Sub Command1_Click() Form5.Visible = Falseform2.Visible = TrueEnd SubPrivate Sub Command2_Click() Picturel.ClsPicture2.ClsDim i As Integer, j As Integer For i = 1 To 5Forj = 1 To 3Picture2.Print v(i, j); Spc；Next jPicture2.PrintPicture2.PrintPicture1.Print w(i); Next iE

23、nd Sub5泛化代码：Private Sub Command1_Click() Form4.Visible = Falseform2.Visible = TrueEnd SubPrivate Sub Command2_Click() For s = 1 To 20Picturel.ScaleTop = 1.5Picturel.ScaleHeight = -2Picturel.ScaleLeft = -5Picturel.ScaleWidth = 30Picture1.Line (-5, 0)-(25, 0)Picture1.Line (0, -0.5)-(0, 1.5)For i = 1 To 20Picture1.PSet (Ti(i), outD(i), RGB(128, 128, 0)Picture1.PSet (Ti(i), y22(i), RGB(128, 0, 0)9Next iFor i = 1 To 19Picture1.Line (Ti(i), outD(i)-(Ti(i + 1), outD(i + 1), RGB(128, 128, 0)Picture1.Line (Ti(i), y22(i)-(Ti(i + 1), y22(i + 1), RGB(128, 0, 0)Next iNext sE