我应该做的事情。我有一个黑白图像(100x100px):Backprop实施问题
我应该来训练backpropagation神经网络与此图像。输入是图像的x,y坐标(从0到99),输出是1(白色)或0(黑色)。
一旦网络已经学会了,我希望它能够根据图像的重量重现图像,并获得最接近原始图像的图像。
这里是我的backprop实现:
import os
import math
import Image
import random
from random import sample
#------------------------------ class definitions
class Weight:
def __init__(self, fromNeuron, toNeuron):
self.value = random.uniform(-0.5, 0.5)
self.fromNeuron = fromNeuron
self.toNeuron = toNeuron
fromNeuron.outputWeights.append(self)
toNeuron.inputWeights.append(self)
self.delta = 0.0 # delta value, this will accumulate and after each training cycle used to adjust the weight value
def calculateDelta(self, network):
self.delta += self.fromNeuron.value * self.toNeuron.error
class Neuron:
def __init__(self):
self.value = 0.0 # the output
self.idealValue = 0.0 # the ideal output
self.error = 0.0 # error between output and ideal output
self.inputWeights = []
self.outputWeights = []
def activate(self, network):
x = 0.0;
for weight in self.inputWeights:
x += weight.value * weight.fromNeuron.value
# sigmoid function
if x < -320:
self.value = 0
elif x > 320:
self.value = 1
else:
self.value = 1/(1 + math.exp(-x))
class Layer:
def __init__(self, neurons):
self.neurons = neurons
def activate(self, network):
for neuron in self.neurons:
neuron.activate(network)
class Network:
def __init__(self, layers, learningRate):
self.layers = layers
self.learningRate = learningRate # the rate at which the network learns
self.weights = []
for hiddenNeuron in self.layers[1].neurons:
for inputNeuron in self.layers[0].neurons:
self.weights.append(Weight(inputNeuron, hiddenNeuron))
for outputNeuron in self.layers[2].neurons:
self.weights.append(Weight(hiddenNeuron, outputNeuron))
def setInputs(self, inputs):
self.layers[0].neurons[0].value = float(inputs[0])
self.layers[0].neurons[1].value = float(inputs[1])
def setExpectedOutputs(self, expectedOutputs):
self.layers[2].neurons[0].idealValue = expectedOutputs[0]
def calculateOutputs(self, expectedOutputs):
self.setExpectedOutputs(expectedOutputs)
self.layers[1].activate(self) # activation function for hidden layer
self.layers[2].activate(self) # activation function for output layer
def calculateOutputErrors(self):
for neuron in self.layers[2].neurons:
neuron.error = (neuron.idealValue - neuron.value) * neuron.value * (1 - neuron.value)
def calculateHiddenErrors(self):
for neuron in self.layers[1].neurons:
error = 0.0
for weight in neuron.outputWeights:
error += weight.toNeuron.error * weight.value
neuron.error = error * neuron.value * (1 - neuron.value)
def calculateDeltas(self):
for weight in self.weights:
weight.calculateDelta(self)
def train(self, inputs, expectedOutputs):
self.setInputs(inputs)
self.calculateOutputs(expectedOutputs)
self.calculateOutputErrors()
self.calculateHiddenErrors()
self.calculateDeltas()
def learn(self):
for weight in self.weights:
weight.value += self.learningRate * weight.delta
def calculateSingleOutput(self, inputs):
self.setInputs(inputs)
self.layers[1].activate(self)
self.layers[2].activate(self)
#return round(self.layers[2].neurons[0].value, 0)
return self.layers[2].neurons[0].value
#------------------------------ initialize objects etc
inputLayer = Layer([Neuron() for n in range(2)])
hiddenLayer = Layer([Neuron() for n in range(10)])
outputLayer = Layer([Neuron() for n in range(1)])
learningRate = 0.4
network = Network([inputLayer, hiddenLayer, outputLayer], learningRate)
# let's get the training set
os.chdir("D:/stuff")
image = Image.open("backprop-input.gif")
pixels = image.load()
bbox = image.getbbox()
width = 5#bbox[2] # image width
height = 5#bbox[3] # image height
trainingInputs = []
trainingOutputs = []
b = w = 0
for x in range(0, width):
for y in range(0, height):
if (0, 0, 0, 255) == pixels[x, y]:
color = 0
b += 1
elif (255, 255, 255, 255) == pixels[x, y]:
color = 1
w += 1
trainingInputs.append([float(x), float(y)])
trainingOutputs.append([float(color)])
print "\nOriginal image ... Black:"+str(b)+" White:"+str(w)+"\n"
#------------------------------ let's train
for i in range(500):
for j in range(len(trainingOutputs)):
network.train(trainingInputs[j], trainingOutputs[j])
network.learn()
for w in network.weights:
w.delta = 0.0
#------------------------------ let's check
b = w = 0
for x in range(0, width):
for y in range(0, height):
out = network.calculateSingleOutput([float(x), float(y)])
if 0.0 == round(out):
color = (0, 0, 0, 255)
b += 1
elif 1.0 == round(out):
color = (255, 255, 255, 255)
w += 1
pixels[x, y] = color
#print out
print "\nAfter learning the network thinks ... Black:"+str(b)+" White:"+str(w)+"\n"
显然,有一些问题,我的执行。上面的代码返回:
原图...黑:21白:4
后学习网络认为... 黑:25白:0
它完成如果我尝试使用更大的训练集(为了测试目的,我正在测试上面的图像中的25个像素),那也是一样的。它返回所有像素在学习后应该是黑色的。现在
,如果我使用手动训练这样设置代替:
trainingInputs = [
[0.0,0.0],
[1.0,0.0],
[2.0,0.0],
[0.0,1.0],
[1.0,1.0],
[2.0,1.0],
[0.0,2.0],
[1.0,2.0],
[2.0,2.0]
]
trainingOutputs = [
[0.0],
[1.0],
[1.0],
[0.0],
[1.0],
[0.0],
[0.0],
[0.0],
[1.0]
]
#------------------------------ let's train
for i in range(500):
for j in range(len(trainingOutputs)):
network.train(trainingInputs[j], trainingOutputs[j])
network.learn()
for w in network.weights:
w.delta = 0.0
#------------------------------ let's check
for inputs in trainingInputs:
print network.calculateSingleOutput(inputs)
的输出是例如:
0.0330125791296 # this should be 0, OK
0.953539182136 # this should be 1, OK
0.971854575477 # this should be 1, OK
0.00046146137467 # this should be 0, OK
0.896699762781 # this should be 1, OK
0.112909223162 # this should be 0, OK
0.00034058462280 # this should be 0, OK
0.0929886299643 # this should be 0, OK
0.940489647869 # this should be 1, OK
换句话说网络猜到所有像素右侧(包括黑色和白色)。为什么说如果我使用图像中的实际像素而不是像上面那样的硬编码训练集,所有的像素应该是黑色的?
我试图改变隐藏层中的神经元数量(最多100个神经元),但没有成功。
这是一个家庭作业。
这也是我的关于backprop的previous question的延续。
为什么你把它标记为MATLAB?它看起来像你只使用Python。 – gnovice 2010-11-03 20:20:21
@gnovice嗯,我认为MATLAB常常用于编程神经网络和其他AI内容,所以我认为一些MATLAB程序员可能会发现我的算法中有一个错误,即使它是用Python编写的。 – 2010-11-03 20:33:49