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def generate_batch(X = X_train, y = y_train, batch_size = 128):
''' Generate a batch of data '''
while True:
for j in range(0, len(X), batch_size):
encoder_input_data = np.zeros((batch_size, max_length_src),dtype='float32')
decoder_input_data = np.zeros((batch_size, max_length_tar),dtype='float32')
decoder_target_data = np.zeros((batch_size, max_length_tar, num_decoder_tokens),dtype='float32')
for i, (input_text, target_text) in enumerate(zip(X[j:j+batch_size], y[j:j+batch_size])):
for t, word in enumerate(input_text.split()):
encoder_input_data[i, t] = input_token_index[word] # encoder input seq
for t, word in enumerate(target_text.split()):
if t<len(target_text.split())-1:
decoder_input_data[i, t] = target_token_index[word] # decoder input seq
if t>0:
# decoder target sequence (one hot encoded)
# does not include the START_ token
# Offset by one timestep
decoder_target_data[i, t - 1, target_token_index[word]] = 1.
yield([encoder_input_data, decoder_input_data], decoder_target_data)
latent_dim=300
encoder_inputs = Input(shape=(None,))
enc_emb = Embedding(num_encoder_tokens, latent_dim, mask_zero = True)(encoder_inputs)
encoder_lstm = LSTM(latent_dim, return_state=True)
encoder_outputs, state_h, state_c = encoder_lstm(enc_emb)
# We discard `encoder_outputs` and only keep the states.
encoder_states = [state_h, state_c]
decoder_inputs = Input(shape=(None,))
dec_emb_layer = Embedding(num_decoder_tokens, latent_dim, mask_zero = True)
dec_emb = dec_emb_layer(decoder_inputs)
# We set up our decoder to return full output sequences,
# and to return internal states as well. We don't use the
# return states in the training model, but we will use them in inference.
decoder_lstm = LSTM(latent_dim, return_sequences=True, return_state=True)
decoder_outputs, _, _ = decoder_lstm(dec_emb,
initial_state=encoder_states)
decoder_dense = Dense(num_decoder_tokens, activation='softmax')
decoder_outputs = decoder_dense(decoder_outputs)
# Define the model that will turn
# `encoder_input_data` & `decoder_input_data` into `decoder_target_data`
model = Model([encoder_inputs, decoder_inputs], decoder_outputs)
model.compile(optimizer='rmsprop', loss='categorical_crossentropy')
model.summary()
train_samples = len(X_train)
val_samples = len(X_test)
batch_size = 128
epochs = 100
model.fit_generator(generator = generate_batch(X_train, y_train, batch_size = batch_size),
steps_per_epoch = train_samples//batch_size,
epochs=epochs,
validation_data = generate_batch(X_test, y_test, batch_size = batch_size),
validation_steps = val_samples//batch_size)
model.save_weights('nmt_weights.h5')
# Encode the input sequence to get the "thought vectors"
encoder_model = Model(encoder_inputs, encoder_states)
# Decoder setup
# Below tensors will hold the states of the previous time step
decoder_state_input_h = Input(shape=(latent_dim,))
decoder_state_input_c = Input(shape=(latent_dim,))
decoder_states_inputs = [decoder_state_input_h, decoder_state_input_c]
dec_emb2= dec_emb_layer(decoder_inputs) # Get the embeddings of the decoder sequence
# To predict the next word in the sequence, set the initial states to the states from the previous time step
decoder_outputs2, state_h2, state_c2 = decoder_lstm(dec_emb2, initial_state=decoder_states_inputs)
decoder_states2 = [state_h2, state_c2]
decoder_outputs2 = decoder_dense(decoder_outputs2) # A dense softmax layer to generate prob dist. over the target vocabulary
# Final decoder model
decoder_model = Model(
[decoder_inputs] + decoder_states_inputs,
[decoder_outputs2] + decoder_states2)
def decode_sequence(input_seq):
# Encode the input as state vectors.
states_value = encoder_model.predict(input_seq)
# Generate empty target sequence of length 1.
target_seq = np.zeros((1,1))
# Populate the first character of target sequence with the start character.
target_seq[0, 0] = target_token_index['START_']
# Sampling loop for a batch of sequences
# (to simplify, here we assume a batch of size 1).
stop_condition = False
decoded_sentence = ''
while not stop_condition:
output_tokens, h, c = decoder_model.predict([target_seq] + states_value)
# Sample a token
sampled_token_index = np.argmax(output_tokens[0, -1, :])
sampled_char = reverse_target_char_index[sampled_token_index]
decoded_sentence += ' '+sampled_char
# Exit condition: either hit max length
# or find stop character.
if (sampled_char == '_END' or
len(decoded_sentence) > 50):
stop_condition = True
# Update the target sequence (of length 1).
target_seq = np.zeros((1,1))
target_seq[0, 0] = sampled_token_index
# Update states
states_value = [h, c]
return decoded_sentence
train_gen = generate_batch(X_train, y_train, batch_size = 1)
k=-1
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