python_deeplearning04_手書き数字のデータセットMNIST下

6482 ワード

20180423 qzd

ch 04-手書き数字のデータセットMNIST下


Tip:フルデータセットを使用したトレーニングとテスト
(前回の実験はtrain_100.csv,test_10.csvに基づいており,今回の実験は完全なmnistデータセットに基づいている)
  • ネットワークモデル
  • # python notebook for Make Your Own Neural Network
    # code for a 3-layer neural network, and code for learning the MNIST dataset
    
    import numpy
    # scipy.special for the sigmoid function expit()
    import scipy.special
    # library for plotting arrays
    import matplotlib.pyplot
    # ensure the plots are inside this notebook, not an external window
    %matplotlib inline
    
    # neural network class definition
    class neuralNetwork:
        
        
        # initialise the neural network
        def __init__(self, inputnodes, hiddennodes, outputnodes, learningrate):
            # set number of nodes in each input, hidden, output layer
            self.inodes = inputnodes
            self.hnodes = hiddennodes
            self.onodes = outputnodes
            
            # link weight matrices, wih and who
            # weights inside the arrays are w_i_j, where link is from node i to node j in the next layer
            # w11 w21
            # w12 w22 etc 
            self.wih = numpy.random.normal(0.0, pow(self.inodes, -0.5), (self.hnodes, self.inodes))
            self.who = numpy.random.normal(0.0, pow(self.hnodes, -0.5), (self.onodes, self.hnodes))
    
            # learning rate
            self.lr = learningrate
            
            # activation function is the sigmoid function
            self.activation_function = lambda x: scipy.special.expit(x)
            
            pass
    
        
        # train the neural network
        def train(self, inputs_list, targets_list):
            # convert inputs list to 2d array
            inputs = numpy.array(inputs_list, ndmin=2).T
            targets = numpy.array(targets_list, ndmin=2).T
            
            # calculate signals into hidden layer
            hidden_inputs = numpy.dot(self.wih, inputs)
            # calculate the signals emerging from hidden layer
            hidden_outputs = self.activation_function(hidden_inputs)
            
            # calculate signals into final output layer
            final_inputs = numpy.dot(self.who, hidden_outputs)
            # calculate the signals emerging from final output layer
            final_outputs = self.activation_function(final_inputs)
            
            # output layer error is the (target - actual)
            output_errors = targets - final_outputs
            # hidden layer error is the output_errors, split by weights, recombined at hidden nodes
            hidden_errors = numpy.dot(self.who.T, output_errors) 
            
            # update the weights for the links between the hidden and output layers
            self.who += self.lr * numpy.dot((output_errors * final_outputs * (1.0 - final_outputs)), numpy.transpose(hidden_outputs))
            
            # update the weights for the links between the input and hidden layers
            self.wih += self.lr * numpy.dot((hidden_errors * hidden_outputs * (1.0 - hidden_outputs)), numpy.transpose(inputs))
            
            pass
    
        
        # query the neural network
        def query(self, inputs_list):
            # convert inputs list to 2d array
            inputs = numpy.array(inputs_list, ndmin=2).T
            
            # calculate signals into hidden layer
            hidden_inputs = numpy.dot(self.wih, inputs)
            # calculate the signals emerging from hidden layer
            hidden_outputs = self.activation_function(hidden_inputs)
            
            # calculate signals into final output layer
            final_inputs = numpy.dot(self.who, hidden_outputs)
            # calculate the signals emerging from final output layer
            final_outputs = self.activation_function(final_inputs)
            
            return final_outputs  
    
    
  • 初期値の設定(一部の改良1:学習率の調整、ネットワーク形状の変更)
  • # number of input, hidden and output nodes
    input_nodes = 784
    hidden_nodes = 200
    output_nodes = 10
    
    # learning rate
    learning_rate = 0.1
    
    # create instance of neural network
    n = neuralNetwork(input_nodes,hidden_nodes,output_nodes, learning_rate)
    
  • 完全なトレーニングデータ
  • を取得
    # load the mnist training data CSV file into a list
    training_data_file = open("mnist_dataset/mnist_train.csv", 'r')
    training_data_list = training_data_file.readlines()
    training_data_file.close()
    
  • トレーニングネットワーク(いくつかの改良2:複数回実行)
  • # train the neural network
    
    # epochs is the number of times the training data set is used for training
    epochs = 5
    
    for e in range(epochs):
        # go through all records in the training data set
        for record in training_data_list:
            # split the record by the ',' commas
            all_values = record.split(',')
            # scale and shift the inputs
            inputs = (numpy.asfarray(all_values[1:]) / 255.0 * 0.99) + 0.01
            # create the target output values (all 0.01, except the desired label which is 0.99)
            targets = numpy.zeros(output_nodes) + 0.01
            # all_values[0] is the target label for this record
            targets[int(all_values[0])] = 0.99
            n.train(inputs, targets)
            pass
        pass
    
  • 完全なテストデータ
  • を取得
    # load the mnist test data CSV file into a list
    test_data_file = open("mnist_dataset/mnist_test.csv", 'r')
    test_data_list = test_data_file.readlines()
    test_data_file.close()
    
  • テストネットワーク
  • # test the neural network
    
    # scorecard for how well the network performs, initially empty
    scorecard = []
    
    # go through all the records in the test data set
    for record in test_data_list:
        # split the record by the ',' commas
        all_values = record.split(',')
        # correct answer is first value
        correct_label = int(all_values[0])
        # scale and shift the inputs
        inputs = (numpy.asfarray(all_values[1:]) / 255.0 * 0.99) + 0.01
        # query the network
        outputs = n.query(inputs)
        # the index of the highest value corresponds to the label
        label = numpy.argmax(outputs)
        # append correct or incorrect to list
        if (label == correct_label):
            # network's answer matches correct answer, add 1 to scorecard
            scorecard.append(1)
        else:
            # network's answer doesn't match correct answer, add 0 to scorecard
            scorecard.append(0)
            pass
        
        pass
    
  • 表示精度
  • # calculate the performance score, the fraction of correct answers
    scorecard_array = numpy.asarray(scorecard)
    print ("performance = ", scorecard_array.sum() / scorecard_array.size)
    
  • 出力結果(epochs=1の場合):performance=0.9578