Tensorflow下的自編碼器
在TensorFlow下的autoEncoder(自編碼器):
預備條件:
(1)Python2。7
(2)預安裝TensorFlow
由於存在格式的問題,下面的程式存在顯示不正常,但是程式是可以正常執行的。
import numpy as np
import sklearn。preprocessing as prep
import tensorflow as tf
from tensorflow。examples。tutorials。mnist import input_data
# 建立一個均勻分佈的公式:(low,high)
def xavier_init(fan_in,fan_out,constant=1):
low = -constant * np。sqrt(6。0 / (fan_in + fan_out))
high = constant * np。sqrt(6。0 / (fan_in + fan_out))
return tf。random_uniform((fan_in,fan_out),minval=low,maxval=high,dtype=tf。float32)
# 定義了一個高斯白噪聲的自編碼器
class AdditiveGaussianNoiseAutoencoder(object):
# 初始化
def __init__(self,n_input,n_hidden,transfer_function=tf。nn。softplus,optimizer=tf。train。AdamOptimizer(),scale=0。1):
self。n_input = n_input
self。n_hidden = n_hidden
self。transfer = transfer_function
self。scale = tf。placeholder(tf。float32)
self。training_scale = scale
network_weights = self。_initialize_weights()
self。weights = network_weights
self。x = tf。placeholder(tf。float32,[None,self。n_input])
self。hidden = self。transfer(tf。add(tf。matmul(self。x + scale * tf。random_normal((n_input,)),self。weights[‘w1’]),self。weights[‘b1’]))
self。reconstruction = tf。add(tf。matmul(self。hidden,self。weights[‘w2’]),self。weights[‘b2’])
# cost function: 1/2 * (reconstruction - x)^2
self。cost = 0。5 * tf。reduce_sum(tf。pow(tf。subtract(self。reconstruction,self。x),2。0))
self。optimizer = optimizer。minimize(self。cost)
init = tf。global_variables_initializer()
self。sess = tf。Session()
self。sess。run(init)
# 初始化權值
def _initialize_weights(self):
all_weights = dict()
all_weights[‘w1’] = tf。Variable(xavier_init(self。n_input,self。n_hidden))
all_weights[‘b1’] = tf。Variable(tf。zeros([self。n_hidden],dtype = tf。float32))
all_weights[‘w2’] = tf。Variable(tf。zeros([self。n_hidden,self。n_input],dtype = tf。float32))
all_weights[‘b2’] = tf。Variable(tf。zeros([self。n_input],dtype=tf。float32))
return all_weights
# 擬合
def partial_fit(self,X):
cost,opt = self。sess。run((self。cost,self。optimizer),feed_dict={self。x:X,self。scale:self。training_scale})
return cost
# 計算整個的損失函式
def calc_total_cost(self,X):
return self。sess。run(self。cost,feed_dict={self。x:X,self。scale:self。training_scale})
# 變換
def transform(self,X):
return self。sess。run(self。hidden,feed_dict={self。x:X,self。scale:self。training_scale})
# 產生
def generate(self,hidden=None):
if hidden is None:
hidden = np。random。normal(size=self。weights[“b1”])
return self。sess。run(self。reconstruction,feed_dict={self。hidden:hidden})
# 重構
def reconstruct(self,X):
return self。sess。run(self。reconstruction,feed_dict={self。x:X,self。scale:self。training_scale})
# 獲取權值
def getWeights(self):
return self。sess。run(self。weights[“w1”])
# 獲取偏置量
def getBiases(self):
return self。sess。run(self。weights[“b1”])
# 標準化
def standard_scale(X_train,X_test):
preprocessor = prep。StandardScaler()。fit(X_train)
X_train = preprocessor。transform(X_train)
X_test = preprocessor。transform(X_test)
return X_train,X_test
# 隨機數
def get_random_block_from_data(data,batch_size):
start_index = np。random。randint(0,len(data) - batch_size)
return data[start_index:(start_index + batch_size)]
if __name__ == “__main__”:
mnist = input_data。read_data_sets(“MINIST_data/”,one_hot=True)
X_train,X_test = standard_scale(mnist。train。images,mnist。test。images)
n_samples = int(mnist。train。num_examples)
training_epochs = 20
batch_size = 128
display_step = 1
autoencoder = AdditiveGaussianNoiseAutoencoder(
n_input = 784,
n_hidden = 200,
transfer_function = tf。nn。softplus,
optimizer = tf。train。AdamOptimizer(learning_rate = 0。001),
scale = 0。01
)
for epoch in range(training_epochs):
avg_cost = 0。
total_batch = int(n_samples / batch_size)
for i in range(total_batch):
batch_xs = get_random_block_from_data(X_train,batch_size)
cost = autoencoder。partial_fit(batch_xs)
avg_cost += cost / n_samples * batch_size
if epoch % display_step == 0:
print(“Epoch:”,‘%04d’ % (epoch + 1),“cost=”,“{:。9f}”。format(avg_cost))