tf.reverse_sequence(
input,
seq_lengths,
seq_axis=None,
batch_axis=None,
name=None,
seq_dim=None,
batch_dim=None
)
Defined in tensorflow/python/ops/array_ops.py
.
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, :, ...]
Args:
input
: ATensor
. The input to reverse.seq_lengths
: ATensor
. Must be one of the following types:int32
,int64
. 1-D with lengthinput.dims(batch_dim)
andmax(seq_lengths) <= input.dims(seq_dim)
seq_axis
: Anint
. The dimension which is partially reversed.batch_axis
: An optionalint
. Defaults to0
. The dimension along which reversal is performed.name
: A name for the operation (optional).
Returns:
A Tensor
. Has the same type as input
.