TensorFlow实战框架Chp10--Keras在MNIST数据集上实现LeNet-5模型

• Keras在MNIST数据集上实现LeNet-5模型

# -*- coding: utf-8 -*-
"""
Created on Tue Jul 10 20:04:03 2018

@author: muli
"""

import keras
from keras.datasets import mnist
from keras.models import Sequential
from keras.layers import Dense, Flatten, Conv2D, MaxPooling2D
from keras import backend as K

num_classes = 10
img_rows, img_cols = 28, 28

# 通过Keras封装好的API加载MNIST数据。其中trainX就是一个60000 * 28 * 28的数组，
# trainY是每一张图片对应的数字。
(trainX, trainY), (testX, testY) = mnist.load_data()

# 根据对图像编码的格式要求来设置输入层的格式。
if K.image_data_format() == 'channels_first':
    trainX = trainX.reshape(trainX.shape[0], 1, img_rows, img_cols)
    testX = testX.reshape(testX.shape[0], 1, img_rows, img_cols)
    input_shape = (1, img_rows, img_cols)
else:
    trainX = trainX.reshape(trainX.shape[0], img_rows, img_cols, 1)
    testX = testX.reshape(testX.shape[0], img_rows, img_cols, 1)
    input_shape = (img_rows, img_cols, 1)

trainX = trainX.astype('float32')
testX = testX.astype('float32')
trainX /= 255.0
testX /= 255.0

# 将标准答案转化为需要的格式（one-hot编码）。
trainY = keras.utils.to_categorical(trainY, num_classes)
testY = keras.utils.to_categorical(testY, num_classes)


# 2. 通过Keras的API定义卷机神经网络
# 使用Keras API定义模型。
model = Sequential()
model.add(Conv2D(32, kernel_size=(5, 5), activation='relu', input_shape=input_shape))
model.add(MaxPooling2D(pool_size=(2, 2)))
model.add(Conv2D(64, (5, 5), activation='relu'))
model.add(MaxPooling2D(pool_size=(2, 2)))
model.add(Flatten())
model.add(Dense(500, activation='relu'))
model.add(Dense(num_classes, activation='softmax'))

# 定义损失函数、优化函数和评测方法。
model.compile(loss=keras.losses.categorical_crossentropy,
              optimizer=keras.optimizers.SGD(),
              metrics=['accuracy'])

# 3. 通过Keras的API训练模型并计算在测试数据上的准确率
model.fit(trainX, trainY,
          batch_size=128,
          epochs=10,
          validation_data=(testX, testY))

# 在测试数据上计算准确率。
score = model.evaluate(testX, testY)
print('Test loss:', score[0])
print('Test accuracy:', score[1])