library.py 文件源码

def _reverse_seq(input_seq, lengths):
  """Reverse a list of Tensors up to specified lengths.

  Args:
    input_seq: Sequence of seq_len tensors of dimension (batch_size, depth)
    lengths:   A tensor of dimension batch_size, containing lengths for each
               sequence in the batch. If "None" is specified, simply reverses
               the list.

  Returns:
    time-reversed sequence
  """
  if lengths is None:
    return list(reversed(input_seq))

  input_shape = tensor_shape.matrix(None, None)
  for input_ in input_seq:
    input_shape.merge_with(input_.get_shape())
    input_.set_shape(input_shape)

  # Join into (time, batch_size, depth)
  s_joined = tf.stack(input_seq)

  if lengths is not None:
    lengths = tf.to_int64(lengths)

  # Reverse along dimension 0
  s_reversed = tf.reverse_sequence(s_joined, lengths, 0, 1)
  # Split again into list
  result = tf.unstack(s_reversed)
  for r in result:
    r.set_shape(input_shape)
  return result