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test.py
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test.py
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import numpy as np
import matplotlib.pylab as plt
import gzip
import cPickle
import tensorflow as tf
import input_data
def xavier_init(fan_in, fan_out, constant=1):
""" Xavier initialization of network weights"""
# https://stackoverflow.com/questions/33640581/how-to-do-xavier-initialization-on-tensorflow
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)
class VariationalAutoencoder(object):
""" Variation Autoencoder (VAE) with an sklearn-like interface implemented using TensorFlow.
This implementation uses probabilistic encoders and decoders using Gaussian
distributions and realized by multi-layer perceptrons. The VAE can be learned
end-to-end.
See "Auto-Encoding Variational Bayes" by Kingma and Welling for more details.
"""
def __init__(self, network_architecture, transfer_fct=tf.nn.softplus,
learning_rate=0.001, batch_size=100):
self.network_architecture = network_architecture
self.transfer_fct = transfer_fct
self.learning_rate = learning_rate
self.batch_size = batch_size
# tf Graph input
self.x = tf.placeholder(tf.float32, [None, network_architecture["n_input"]])
# Create autoencoder network
self._create_network()
# Define loss function based variational upper-bound and
# corresponding optimizer
self._create_loss_optimizer()
# Initializing the tensor flow variables
init = tf.initialize_all_variables()
# Launch the session
self.sess = tf.InteractiveSession()
self.sess.run(init)
def _create_network(self):
# Initialize autoencode network weights and biases
network_weights = self._initialize_weights(**self.network_architecture)
# Use recognition network to determine mean and
# (log) variance of Gaussian distribution in latent
# space
self.z_mean, self.z_log_sigma_sq = \
self._recognition_network(network_weights["weights_recog"],
network_weights["biases_recog"])
# Draw one sample z from Gaussian distribution
n_z = self.network_architecture["n_z"]
eps = tf.random_normal((self.batch_size, n_z), 0, 1,
dtype=tf.float32)
# z = mu + sigma*epsilon
self.z = tf.add(self.z_mean,
tf.mul(tf.sqrt(tf.exp(self.z_log_sigma_sq)), eps))
# Use generator to determine mean of
# Bernoulli distribution of reconstructed input
self.x_reconstr_mean = \
self._generator_network(network_weights["weights_gener"],
network_weights["biases_gener"])
def _initialize_weights(self, n_hidden_recog_1, n_hidden_recog_2,
n_hidden_gener_1, n_hidden_gener_2,
n_input, n_z):
all_weights = dict()
all_weights['weights_recog'] = {
'h1': tf.Variable(xavier_init(n_input, n_hidden_recog_1)),
'h2': tf.Variable(xavier_init(n_hidden_recog_1, n_hidden_recog_2)),
'out_mean': tf.Variable(xavier_init(n_hidden_recog_2, n_z)),
'out_log_sigma': tf.Variable(xavier_init(n_hidden_recog_2, n_z))}
all_weights['biases_recog'] = {
'b1': tf.Variable(tf.zeros([n_hidden_recog_1], dtype=tf.float32)),
'b2': tf.Variable(tf.zeros([n_hidden_recog_2], dtype=tf.float32)),
'out_mean': tf.Variable(tf.zeros([n_z], dtype=tf.float32)),
'out_log_sigma': tf.Variable(tf.zeros([n_z], dtype=tf.float32))}
all_weights['weights_gener'] = {
'h1': tf.Variable(xavier_init(n_z, n_hidden_gener_1)),
'h2': tf.Variable(xavier_init(n_hidden_gener_1, n_hidden_gener_2)),
'out_mean': tf.Variable(xavier_init(n_hidden_gener_2, n_input)),
'out_log_sigma': tf.Variable(xavier_init(n_hidden_gener_2, n_input))}
all_weights['biases_gener'] = {
'b1': tf.Variable(tf.zeros([n_hidden_gener_1], dtype=tf.float32)),
'b2': tf.Variable(tf.zeros([n_hidden_gener_2], dtype=tf.float32)),
'out_mean': tf.Variable(tf.zeros([n_input], dtype=tf.float32)),
'out_log_sigma': tf.Variable(tf.zeros([n_input], dtype=tf.float32))}
return all_weights
def _recognition_network(self, weights, biases):
# Generate probabilistic encoder (recognition network), which
# maps inputs onto a normal distribution in latent space.
# The transformation is parametrized and can be learned.
layer_1 = self.transfer_fct(tf.add(tf.matmul(self.x, weights['h1']),
biases['b1']))
layer_2 = self.transfer_fct(tf.add(tf.matmul(layer_1, weights['h2']),
biases['b2']))
z_mean = tf.add(tf.matmul(layer_2, weights['out_mean']),
biases['out_mean'])
z_log_sigma_sq = \
tf.add(tf.matmul(layer_2, weights['out_log_sigma']),
biases['out_log_sigma'])
return (z_mean, z_log_sigma_sq)
def _generator_network(self, weights, biases):
# Generate probabilistic decoder (decoder network), which
# maps points in latent space onto a Bernoulli distribution in data space.
# The transformation is parametrized and can be learned.
layer_1 = self.transfer_fct(tf.add(tf.matmul(self.z, weights['h1']),
biases['b1']))
layer_2 = self.transfer_fct(tf.add(tf.matmul(layer_1, weights['h2']),
biases['b2']))
x_reconstr_mean = \
tf.nn.sigmoid(tf.add(tf.matmul(layer_2, weights['out_mean']),
biases['out_mean']))
return x_reconstr_mean
def _create_loss_optimizer(self):
# The loss is composed of two terms:
# 1.) The reconstruction loss (the negative log probability
# of the input under the reconstructed Bernoulli distribution
# induced by the decoder in the data space).
# This can be interpreted as the number of "nats" required
# for reconstructing the input when the activation in latent
# is given.
# Adding 1e-10 to avoid evaluatio of log(0.0)
reconstr_loss = \
-tf.reduce_sum(self.x * tf.log(1e-10 + self.x_reconstr_mean)
+ (1-self.x) * tf.log(1e-10 + 1 - self.x_reconstr_mean),
1)
# 2.) The latent loss, which is defined as the Kullback Leibler divergence
## between the distribution in latent space induced by the encoder on
# the data and some prior. This acts as a kind of regularizer.
# This can be interpreted as the number of "nats" required
# for transmitting the the latent space distribution given
# the prior.
latent_loss = -0.5 * tf.reduce_sum(1 + self.z_log_sigma_sq
- tf.square(self.z_mean)
- tf.exp(self.z_log_sigma_sq), 1)
self.cost = tf.reduce_mean(reconstr_loss + latent_loss) # average over batch
# Use ADAM optimizer
self.optimizer = \
tf.train.AdamOptimizer(learning_rate=self.learning_rate).minimize(self.cost)
def partial_fit(self, X):
"""Train model based on mini-batch of input data.
Return cost of mini-batch.
"""
opt, cost = self.sess.run((self.optimizer, self.cost),
feed_dict={self.x: X})
return cost
def transform(self, X):
"""Transform data by mapping it into the latent space."""
# Note: This maps to mean of distribution, we could alternatively
# sample from Gaussian distribution
return self.sess.run(self.z_mean, feed_dict={self.x: X})
def generate(self, z_mu=None):
""" Generate data by sampling from latent space.
If z_mu is not None, data for this point in latent space is
generated. Otherwise, z_mu is drawn from prior in latent
space.
"""
if z_mu is None:
z_mu = np.random.normal(size=self.network_architecture["n_z"])
# Note: This maps to mean of distribution, we could alternatively
# sample from Gaussian distribution
return self.sess.run(self.x_reconstr_mean,
feed_dict={self.z: z_mu})
def reconstruct(self, X):
""" Use VAE to reconstruct given data. """
return self.sess.run(self.x_reconstr_mean,
feed_dict={self.x: X})
def train(network_architecture, learning_rate=0.001,
batch_size=100, training_epochs=10, display_step=5):
vae = VariationalAutoencoder(network_architecture,
learning_rate=learning_rate,
batch_size=batch_size)
# Training cycle
for epoch in range(training_epochs):
avg_cost = 0.
total_batch = int(n_samples / batch_size)
# Loop over all batches
for i in range(total_batch):
batch_xs, _ = mnist.train.next_batch(batch_size)
# Fit training using batch data
cost = vae.partial_fit(batch_xs)
# Compute average loss
avg_cost += cost / n_samples * batch_size
# Display logs per epoch step
if epoch % display_step == 0:
print "Epoch:", '%04d' % (epoch+1), \
"cost=", "{:.9f}".format(avg_cost)
return vae
#f = gzip.open('mnist.pkl.gz', 'rb')
#train_set, valid_set, test_set = cPickle.load(f)
#f.close()
#data = train_set[0]
#labels = train_set[1]
#n_samples = data.shape[0]
mnist = input_data.read_data_sets('MNIST_data', one_hot=True)
n_samples = mnist.train.num_examples
network_architecture = \
dict(n_hidden_recog_1=500, # 1st layer encoder neurons
n_hidden_recog_2=500, # 2nd layer encoder neurons
n_hidden_gener_1=500, # 1st layer decoder neurons
n_hidden_gener_2=500, # 2nd layer decoder neurons
n_input=784, # MNIST data input (img shape: 28*28)
n_z=20) # dimensionality of latent space
vae = train(network_architecture, training_epochs=100)
#saver = tf.train.Saver()
#saver.save(vae.sess, '500.ckpt')