Tensorflow CNN(两层卷积+全连接+softmax)

由于卷积用于分类的方法非常固定，因此直接贴上源码以及链接，有需要的直接稍加修改就可以了。
传送门
简单写一下心得体会

卷积层+pooling层

#定义变量，初始化为截断正态分布的变量
def weight_variable(shape):initial = tf.truncated_normal(shape, stddev=0.1)return tf.Variable(initial)#定义变量，初始化为常量
def bias_variable(shape):initial = tf.constant(0.1, shape=shape)return tf.Variable(initial)# W为核函数，strides为步长，strides=[1, 1, 1, 1]，中间两个为x方向的步长和y方向的步长
# padding='SAME'表示输出的大小和输入的大小一样
def conv2d(x, W):# stride [1, x_movement, y_movement, 1]# Must have strides[0] = strides[3] = 1return tf.nn.conv2d(x, W, strides=[1, 1, 1, 1], padding='SAME')#2x2的pooling，虽然这里padding也是same，但是下采样了。
def max_pool_2x2(x):# stride [1, x_movement, y_movement, 1]return tf.nn.max_pool(x, ksize=[1,2,2,1], strides=[1,2,2,1], padding='SAME')#定义卷积核的值，设置初始值。其中[5,5, 1,32]为卷积核的shape
W_conv1 = weight_variable([5,5, 1,32]) # patch 5x5, in size 1, out size 32
b_conv1 = bias_variable([32])
h_conv1 = tf.nn.relu(conv2d(x_image, W_conv1) + b_conv1) # output size 28x28x32
h_pool1 = max_pool_2x2(h_conv1)

原始代码如下

# View more python tutorial on my Youtube and Youku channel!!!# Youtube video tutorial: https://www.youtube.com/channel/UCdyjiB5H8Pu7aDTNVXTTpcg
# Youku video tutorial: http://i.youku.com/pythontutorial"""
Please note, this code is only for python 3+. If you are using python 2+, please modify the code accordingly.
"""
from __future__ import print_function
import tensorflow as tf
from tensorflow.examples.tutorials.mnist import input_data
# number 1 to 10 data
mnist = input_data.read_data_sets('MNIST_data', one_hot=True)def compute_accuracy(v_xs, v_ys):global predictiony_pre = sess.run(prediction, feed_dict={xs: v_xs, keep_prob: 1})correct_prediction = tf.equal(tf.argmax(y_pre,1), tf.argmax(v_ys,1))accuracy = tf.reduce_mean(tf.cast(correct_prediction, tf.float32))result = sess.run(accuracy, feed_dict={xs: v_xs, ys: v_ys, keep_prob: 1})return resultdef weight_variable(shape):initial = tf.truncated_normal(shape, stddev=0.1)return tf.Variable(initial)def bias_variable(shape):initial = tf.constant(0.1, shape=shape)return tf.Variable(initial)def conv2d(x, W):# stride [1, x_movement, y_movement, 1]# Must have strides[0] = strides[3] = 1return tf.nn.conv2d(x, W, strides=[1, 1, 1, 1], padding='SAME')def max_pool_2x2(x):# stride [1, x_movement, y_movement, 1]return tf.nn.max_pool(x, ksize=[1,2,2,1], strides=[1,2,2,1], padding='SAME')# define placeholder for inputs to network
xs = tf.placeholder(tf.float32, [None, 784])/255.   # 28x28
ys = tf.placeholder(tf.float32, [None, 10])
keep_prob = tf.placeholder(tf.float32)

# print(x_image.shape)  # [n_samples, 28,28,1]## conv1 layer ##
W_conv1 = weight_variable([5,5, 1,32]) # patch 5x5, in size 1, out size 32
b_conv1 = bias_variable([32])
h_conv1 = tf.nn.relu(conv2d(x_image, W_conv1) + b_conv1) # output size 28x28x32
h_pool1 = max_pool_2x2(h_conv1)                                         # output size 14x14x32## conv2 layer ##
W_conv2 = weight_variable([5,5, 32, 64]) # patch 5x5, in size 32, out size 64
b_conv2 = bias_variable([64])
h_conv2 = tf.nn.relu(conv2d(h_pool1, W_conv2) + b_conv2) # output size 14x14x64
h_pool2 = max_pool_2x2(h_conv2)                                         # output size 7x7x64## fc1 layer ##
W_fc1 = weight_variable([7*7*64, 1024])
b_fc1 = bias_variable([1024])
# [n_samples, 7, 7, 64] ->> [n_samples, 7*7*64]
h_pool2_flat = tf.reshape(h_pool2, [-1, 7*7*64])
h_fc1 = tf.nn.relu(tf.matmul(h_pool2_flat, W_fc1) + b_fc1)
h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob)## fc2 layer ##
W_fc2 = weight_variable([1024, 10])
b_fc2 = bias_variable([10])
prediction = tf.nn.softmax(tf.matmul(h_fc1_drop, W_fc2) + b_fc2)# the error between prediction and real data
cross_entropy = tf.reduce_mean(-tf.reduce_sum(ys * tf.log(prediction),reduction_indices=[1]))       # loss
train_step = tf.train.AdamOptimizer(1e-4).minimize(cross_entropy)sess = tf.Session()
# important step
# tf.initialize_all_variables() no long valid from
# 2017-03-02 if using tensorflow >= 0.12
if int((tf.__version__).split('.')[1]) < 12 and int((tf.__version__).split('.')[0]) < 1:init = tf.initialize_all_variables()
else:init = tf.global_variables_initializer()
sess.run(init)for i in range(1000):batch_xs, batch_ys = mnist.train.next_batch(100)sess.run(train_step, feed_dict={xs: batch_xs, ys: batch_ys, keep_prob: 0.5})if i % 50 == 0:print(compute_accuracy(mnist.test.images, mnist.test.labels))

从红色部分可推断：神经网络输入层的个数是由输入的图片的像素个数，对组成的指定的矩阵（如上面xs = tf.placeholder(tf.float32, [None, 784])/255. # 28x28所示），对该矩阵进行指定像素大小的图片分割（28*28）得到矩阵，x_image = tf.reshape(xs, [-1, 28, 28, 1])，该矩阵与W_conv1连接的反推，可与确定输入层神经元个数相关，需要进一步实验解决h_conv1 = tf.nn.relu(conv2d(x_image, W_conv1) + b_conv1) # output size 28x28x32

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