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epochs = 2
# Iterate over epochs.
for epoch in range(epochs):
print("Start of epoch %d" % (epoch,))
# Iterate over the batches of the dataset.
for step, x_batch_train in enumerate(train_dataset):
with tf.GradientTape() as tape:
reconstructed = vae(x_batch_train)
# Compute reconstruction loss
loss = mse_loss_fn(x_batch_train, reconstructed)
loss += sum(vae.losses) # Add KLD regularization loss
grads = tape.gradient(loss, vae.trainable_weights)
optimizer.apply_gradients(zip(grads, vae.trainable_weights))
loss_metric(loss)
if step % 100 == 0:
print("step %d: mean loss = %.4f" % (step, loss_metric.result()))
Start of epoch 0
step 0: mean loss = 0.3577
step 100: mean loss = 0.1258
step 200: mean loss = 0.0994
step 300: mean loss = 0.0893
step 400: mean loss = 0.0843
step 500: mean loss = 0.0809
step 600: mean loss = 0.0788
step 700: mean loss = 0.0772
step 800: mean loss = 0.0760
step 900: mean loss = 0.0750
Start of epoch 1
step 0: mean loss = 0.0747
step 100: mean loss = 0.0740
step 200: mean loss = 0.0735
step 300: mean loss = 0.0730
step 400: mean loss = 0.0727
step 500: mean loss = 0.0723
step 600: mean loss = 0.0720
step 700: mean loss = 0.0717
step 800: mean loss = 0.0715
step 900: mean loss = 0.0712
Note that since the VAE is subclassing Model, it features built-in training loops. So you could also have trained it like this:
vae = VariationalAutoEncoder(784, 64, 32)
optimizer = tf.keras.optimizers.Adam(learning_rate=1e-3)
vae.compile(optimizer, loss=tf.keras.losses.MeanSquaredError())
vae.fit(x_train, x_train, epochs=2, batch_size=64)
Epoch 1/2
938/938 [==============================] - 1s 1ms/step - loss: 0.0745
Epoch 2/2
938/938 [==============================] - 1s 1ms/step - loss: 0.0676
<tensorflow.python.keras.callbacks.History at 0x15f10e150>
Beyond object-oriented development: the Functional API
Was this example too much object-oriented development for you? You can also build models using the Functional API. Importantly, choosing one style or another does not prevent you from leveraging components written in the other style: you can always mix-and-match.
For instance, the Functional API example below reuses the same Sampling layer we defined in the example above:
original_dim = 784
intermediate_dim = 64
latent_dim = 32
# Define encoder model.
original_inputs = tf.keras.Input(shape=(original_dim,), name="encoder_input")
x = layers.Dense(intermediate_dim, activation="relu")(original_inputs)
z_mean = layers.Dense(latent_dim, name="z_mean")(x)
z_log_var = layers.Dense(latent_dim, name="z_log_var")(x)
z = Sampling()((z_mean, z_log_var))
encoder = tf.keras.Model(inputs=original_inputs, outputs=z, name="encoder")
# Define decoder model.
latent_inputs = tf.keras.Input(shape=(latent_dim,), name="z_sampling")
x = layers.Dense(intermediate_dim, activation="relu")(latent_inputs)
outputs = layers.Dense(original_dim, activation="sigmoid")(x)
decoder = tf.keras.Model(inputs=latent_inputs, outputs=outputs, name="decoder")
# Define VAE model.
outputs = decoder(z)
vae = tf.keras.Model(inputs=original_inputs, outputs=outputs, name="vae")
# Add KL divergence regularization loss.
kl_loss = -0.5 * tf.reduce_mean(z_log_var - tf.square(z_mean) - tf.exp(z_log_var) + 1)
vae.add_loss(kl_loss)
# Train.
optimizer = tf.keras.optimizers.Adam(learning_rate=1e-3)
vae.compile(optimizer, loss=tf.keras.losses.MeanSquaredError())
vae.fit(x_train, x_train, epochs=3, batch_size=64)
Epoch 1/3
938/938 [==============================] - 1s 1ms/step - loss: 0.0747
Epoch 2/3
938/938 [==============================] - 1s 1ms/step - loss: 0.0676
Epoch 3/3
938/938 [==============================] - 1s 1ms/step - loss: 0.0676