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ReverseSequence

public final class ReverseSequence

Reverses variable length slices.

This op first slices `input` along the dimension `batch_dim`, and for each slice `i`, reverses the first `seq_lengths[i]` elements along the dimension `seq_dim`.

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_dim` is then given by input slice `i`, with the first `seq_lengths[i]` slices along dimension `seq_dim` 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, :, ...]
 

Nested Classes

class ReverseSequence.Options Optional attributes for ReverseSequence  

Public Methods

Output<T>
asOutput()
Returns the symbolic handle of a tensor.
static ReverseSequence.Options
batchDim(Long batchDim)
static <T, U extends Number> ReverseSequence<T>
create(Scope scope, Operand<T> input, Operand<U> seqLengths, Long seqDim, Options... options)
Factory method to create a class wrapping a new ReverseSequence operation.
Output<T>
output()
The partially reversed input.

Inherited Methods

Public Methods

public Output<T> asOutput ()

Returns the symbolic handle of a tensor.

Inputs to TensorFlow operations are outputs of another TensorFlow operation. This method is used to obtain a symbolic handle that represents the computation of the input.

public static ReverseSequence.Options batchDim (Long batchDim)

Parameters
batchDim The dimension along which reversal is performed.

public static ReverseSequence<T> create (Scope scope, Operand<T> input, Operand<U> seqLengths, Long seqDim, Options... options)

Factory method to create a class wrapping a new ReverseSequence operation.

Parameters
scope current scope
input The input to reverse.
seqLengths 1-D with length `input.dims(batch_dim)` and `max(seq_lengths) <= input.dims(seq_dim)`
seqDim The dimension which is partially reversed.
options carries optional attributes values
Returns
  • a new instance of ReverseSequence

public Output<T> output ()

The partially reversed input. It has the same shape as `input`.