我已经在Tensorflow（python）中使用Seq2Seq进行了几周的实验，我有一个工作模型使用双向编码器和基于注意力的解码器工作正常，我今天添加了Beam搜索，但我有我注意到现在推断的光束宽度为1或更长，当我只使用双向编码器和注意力解码器时，推断只需几秒钟。
环境细节： TensorFlow版本：1.3.0 MacOS 10.12.4
下面的是我的代码的相关部分：
def decoding_layer(dec_input, encoder_state,
target_sequence_length, max_target_sequence_length,
rnn_size,
num_layers, target_vocab_to_int, target_vocab_size,
batch_size, keep_prob, decoding_embedding_size , encoder_outputs):
"""
Create decoding layer
:param dec_input: Decoder input
:param encoder_state: Encoder state
:param target_sequence_length: The lengths of each sequence in the target batch
:param max_target_sequence_length: Maximum length of target sequences
:param rnn_size: RNN Size
:param num_layers: Number of layers
:param target_vocab_to_int: Dictionary to go from the target words to an id
:param target_vocab_size: Size of target vocabulary
:param batch_size: The size of the batch
:param keep_prob: Dropout keep probability
:param decoding_embedding_size: Decoding embedding size
:encoder_outputs : encoder's output
:return: Tuple of (Training BasicDecoderOutput, Inference BasicDecoderOutput)
"""
encoder_outputs_tr =encoder_outputs #tf.transpose(encoder_outputs,[1,0,2])
# 1. Decoder Embedding
dec_embeddings = tf.Variable(tf.random_uniform([target_vocab_size, decoding_embedding_size]))
dec_embed_input = tf.nn.embedding_lookup(dec_embeddings, dec_input)
# 2. Construct the decoder cell
def create_cell(rnn_size):
lstm_cell = tf.contrib.rnn.LSTMCell(rnn_size,
initializer=tf.random_uniform_initializer(-0.1,0.1,seed=2))
drop = tf.contrib.rnn.DropoutWrapper(lstm_cell, output_keep_prob=keep_prob)
return drop
def create_complete_cell(rnn_size,num_layers,encoder_outputs_tr,batch_size,encoder_state , infer ):
if infer and beam_width >0:
encoder_outputs_tr = tf.contrib.seq2seq.tile_batch(encoder_outputs_tr, multiplier=beam_width)
encoder_state = tf.contrib.seq2seq.tile_batch(encoder_state, multiplier=beam_width)
batch_size = batch_size * beam_width
dec_cell = tf.contrib.rnn.MultiRNNCell([create_cell(rnn_size) for _ in range(num_layers)])
attention_mechanism = tf.contrib.seq2seq.BahdanauAttention(num_units=rnn_size, memory=encoder_outputs_tr)
attn_cell = tf.contrib.seq2seq.AttentionWrapper(dec_cell, attention_mechanism , attention_layer_size=rnn_size , output_attention=False)
attn_zero = attn_cell.zero_state(batch_size , tf.float32 )
attn_zero = attn_zero.clone(cell_state = encoder_state)
return attn_zero , attn_cell
intial_train_state , train_cell = create_complete_cell(rnn_size,num_layers,encoder_outputs_tr,batch_size,encoder_state , False )
intial_infer_state , infer_cell = create_complete_cell(rnn_size,num_layers,encoder_outputs_tr,batch_size,encoder_state , True )
output_layer = Dense(target_vocab_size,
kernel_initializer = tf.truncated_normal_initializer(mean = 0.0, stddev=0.1))
with tf.variable_scope("decode"):
train_decoder_out = decoding_layer_train(intial_train_state, train_cell, dec_embed_input,
target_sequence_length, max_target_sequence_length, output_layer, keep_prob)
with tf.variable_scope("decode", reuse=True):
if beam_width == 0 :
infer_decoder_out = decoding_layer_infer(intial_infer_state, infer_cell, dec_embeddings,
target_vocab_to_int['<GO>'], target_vocab_to_int['<EOS>'], max_target_sequence_length,
target_vocab_size, output_layer, batch_size, keep_prob)
else :
infer_decoder_out = decoding_layer_infer_with_Beam(intial_infer_state, infer_cell, dec_embeddings,
target_vocab_to_int['<GO>'], target_vocab_to_int['<EOS>'], max_target_sequence_length,
target_vocab_size, output_layer, batch_size, keep_prob)
print('beam search')
return (train_decoder_out, infer_decoder_out)
"""
DON'T MODIFY ANYTHING IN THIS CELL THAT IS BELOW THIS LINE
"""
#tests.test_decoding_layer(decoding_layer)
def decoding_layer_infer_with_Beam(encoder_state, dec_cell, dec_embeddings, start_of_sequence_id,
end_of_sequence_id, max_target_sequence_length,
vocab_size, output_layer, batch_size, keep_prob):
"""
Create a decoding layer for inference
:param encoder_state: Encoder state
:param dec_cell: Decoder RNN Cell
:param dec_embeddings: Decoder embeddings
:param start_of_sequence_id: GO ID
:param end_of_sequence_id: EOS Id
:param max_target_sequence_length: Maximum length of target sequences
:param vocab_size: Size of decoder/target vocabulary
:param decoding_scope: TenorFlow Variable Scope for decoding
:param output_layer: Function to apply the output layer
:param batch_size: Batch size
:param keep_prob: Dropout keep probability
:return: BasicDecoderOutput containing inference logits and sample_id
"""
start_tokens = tf.tile(tf.constant([start_of_sequence_id], dtype=tf.int32), [batch_size], name='start_tokens')
inference_decoder = tf.contrib.seq2seq.BeamSearchDecoder(
cell=dec_cell,
embedding=dec_embeddings,
start_tokens=start_tokens,
end_token=end_of_sequence_id,
initial_state=encoder_state,
beam_width=beam_width,
output_layer=output_layer)
inference_decoder_output = tf.contrib.seq2seq.dynamic_decode(inference_decoder,
impute_finished=False
)[0]
return inference_decoder_output
"""
DON'T MODIFY ANYTHING IN THIS CELL THAT IS BELOW THIS LINE
"""
#tests.test_decoding_layer_infer(decoding_layer_infer)
以下是模型参数：
# Number of Epochs
epochs = 200
# Batch Size
batch_size = 30
# RNN Size
rnn_size = 512
# Number of Layers
num_layers = 2
# Embedding Size
encoding_embedding_size = 100
decoding_embedding_size = 100
# Learning Rate
learning_rate = 0.001
# Dropout Keep Probability
keep_probability = 0.55
display_step = 10
beam_width=1
我真的很感谢你的帮助，我不确定究竟是什么问题。
谢谢
答案 0 :(得分：2)
好吧所以我发现我做错了什么。
我只需要在动态解码函数中设置最大迭代值，如下所示：
inference_decoder_output = tf.contrib.seq2seq.dynamic_decode(inference_decoder,
impute_finished=False,
maximum_iterations=max_target_sequence_length)[0]