tf.reverse_sequence(input, seq_lengths, seq_axis=None, batch_axis=None, name=None, seq_dim=None, batch_dim=None)
See the guide: Tensor Transformations > Slicing and Joining
Reverses variable length slices.
This op first slices input
along the dimension batch_axis
, and for each slice i
, reverses the first seq_lengths[i]
elements along the dimension seq_axis
.
The elements of seq_lengths
must obey seq_lengths[i] < input.dims[seq_dim]
, and seq_lengths
must be a vector of length input.dims[batch_dim]
.
The output slice i
along dimension batch_axis
is then given by input slice i
, with the first seq_lengths[i]
slices along dimension seq_axis
reversed.
For example:
# Given this: batch_dim = 0 seq_dim = 1 input.dims = (4, 8, ...) seq_lengths = [7, 2, 3, 5] # then slices of input are reversed on seq_dim, but only up to seq_lengths: output[0, 0:7, :, ...] = input[0, 7:0:-1, :, ...] output[1, 0:2, :, ...] = input[1, 2:0:-1, :, ...] output[2, 0:3, :, ...] = input[2, 3:0:-1, :, ...] output[3, 0:5, :, ...] = input[3, 5:0:-1, :, ...] # while entries past seq_lens are copied through: output[0, 7:, :, ...] = input[0, 7:, :, ...] output[1, 2:, :, ...] = input[1, 2:, :, ...] output[2, 3:, :, ...] = input[2, 3:, :, ...] output[3, 2:, :, ...] = input[3, 2:, :, ...]
In contrast, if:
# Given this: batch_dim = 2 seq_dim = 0 input.dims = (8, ?, 4, ...) seq_lengths = [7, 2, 3, 5] # then slices of input are reversed on seq_dim, but only up to seq_lengths: output[0:7, :, 0, :, ...] = input[7:0:-1, :, 0, :, ...] output[0:2, :, 1, :, ...] = input[2:0:-1, :, 1, :, ...] output[0:3, :, 2, :, ...] = input[3:0:-1, :, 2, :, ...] output[0:5, :, 3, :, ...] = input[5:0:-1, :, 3, :, ...] # while entries past seq_lens are copied through: output[7:, :, 0, :, ...] = input[7:, :, 0, :, ...] output[2:, :, 1, :, ...] = input[2:, :, 1, :, ...] output[3:, :, 2, :, ...] = input[3:, :, 2, :, ...] output[2:, :, 3, :, ...] = input[2:, :, 3, :, ...]
input
: A Tensor
. The input to reverse.seq_lengths
: A Tensor
. Must be one of the following types: int32
, int64
. 1-D with length input.dims(batch_dim)
and max(seq_lengths) < input.dims(seq_dim)
seq_axis
: An int
. The dimension which is partially reversed.batch_axis
: An optional int
. Defaults to 0
. The dimension along which reversal is performed.name
: A name for the operation (optional).A Tensor
. Has the same type as input
. The partially reversed input. It has the same shape as input
.
Defined in tensorflow/python/ops/array_ops.py
.
© 2017 The TensorFlow Authors. All rights reserved.
Licensed under the Creative Commons Attribution License 3.0.
Code samples licensed under the Apache 2.0 License.
https://www.tensorflow.org/api_docs/python/tf/reverse_sequence