tensorflow 实现卷及神经网络(5.2)

最新推荐文章于 2025-02-18 01:38:00 发布

wuguangbin1230

最新推荐文章于 2025-02-18 01:38:00 发布

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本文介绍使用TensorFlow实现手写数字识别的全过程。从搭建卷积神经网络开始，逐步介绍如何利用MNIST数据集进行训练，并评估模型的准确性。通过设置不同的超参数，最终达到较高的识别准确率。

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### tensorflow实战教材_5.2

from tensorflow.examples.tutorials.mnist import input_data
import tensorflow as tf
mnist = input_data.read_data_sets("MNIST_data/", one_hot =True )

sess = tf.InteractiveSession()

def 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):
    return tf.nn.conv2d(x,w,strides=[1,1,1,1], padding = 'SAME')

def max_pool_2x2(x):
    return tf.nn.max_pool(x, ksize = [1,2,2,1], strides = [1,2,2,1], padding = 'SAME')

x = tf.placeholder(tf.float32, [None, 784])
y_ = tf.placeholder(tf.float32, [None, 10])
x_image = tf.reshape(x,[-1,28,28,1])

w_conv1 = weight_variable([5,5,1,32])
b_conv1 = bias_variable([32])
h_conv1 = tf.nn.relu(conv2d(x_image, w_conv1) + b_conv1)
h_pool1 = max_pool_2x2(h_conv1)

w_conv2 = weight_variable([5,5,32,64])
b_conv2 = bias_variable([64])
h_conv2 = tf.nn.relu(conv2d(h_pool1, w_conv2) + b_conv2)
h_pool2 = max_pool_2x2(h_conv2)

w_fc1 = weight_variable([7*7*64, 1024])
b_fc1 = bias_variable([1024])
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)
    
keep_prob = tf.placeholder(tf.float32) 
h_fc1_drop = tf.nn.dropout(h_fc1, keep_prob)

w_fc2 = weight_variable([1024,10])
b_fc2 = bias_variable([10])
y_conv = tf.nn.softmax(tf.matmul(h_fc1_drop, w_fc2)+ b_fc2)

cross_entropy = tf.reduce_mean(-tf.reduce_sum(y_ * tf.log(y_conv), reduction_indices = [1]))
train_step = tf.train.AdamOptimizer(1e-4).minimize(cross_entropy)

    
correct_prediction = tf.equal(tf.argmax(y_conv,1), tf.argmax(y_,1))
accuracy = tf.reduce_mean(tf.cast(correct_prediction, tf.float32))

tf.global_variables_initializer().run()

for i in range(10):
    batch = mnist.train.next_batch(50)
    if i%100 == 0:
        train_accuracy =  accuracy.eval(feed_dict = {x:batch[0], y_: batch[1], keep_prob: 1.0})
        print('step %d, training accuracy %g'%(i, train_accuracy))
    train_step.run(feed_dict={x:batch[0], y_: batch[1], keep_prob: 0.5})


print("test accuracy %g"%accuracy.eval(feed_dict={x:mnist.test.images, y_: mnist.test.labels, keep_prob: 1.0}))

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