def ctc_beam_search_decoder(inputs,
sequence_length,
beam_width=100,
top_paths=1,
merge_repeated=True):
"""Performs beam search decoding on the logits given in input.
**Note** The `ctc_greedy_decoder` is a special case of the
`ctc_beam_search_decoder` with `top_paths=1` and `beam_width=1` (but
that decoder is faster for this special case).
If `merge_repeated` is `True`, merge repeated classes in the output beams.
This means that if consecutive entries in a beam are the same,
only the first of these is emitted. That is, when the sequence is
`A B B * B * B` (where '*' is the blank label), the return value is:
* `A B` if `merge_repeated = True`.
* `A B B B` if `merge_repeated = False`.
Args:
inputs: 3-D `float` `Tensor`, size `[max_time x batch_size x num_classes]`.
The logits.
sequence_length: 1-D `int32` vector containing sequence lengths, having size
`[batch_size]`.
beam_width: An int scalar >= 0 (beam search beam width).
top_paths: An int scalar >= 0, <= beam_width (controls output size).
merge_repeated: Boolean. Default: True.
Returns:
A tuple `(decoded, log_probabilities)` where
decoded: A list of length top_paths, where `decoded[j]`
is a `SparseTensor` containing the decoded outputs:
`decoded[j].indices`: Indices matrix `(total_decoded_outputs[j] x 2)`
The rows store: [batch, time].
`decoded[j].values`: Values vector, size `(total_decoded_outputs[j])`.
The vector stores the decoded classes for beam j.
`decoded[j].dense_shape`: Shape vector, size `(2)`.
The shape values are: `[batch_size, max_decoded_length[j]]`.
log_probability: A `float` matrix `(batch_size x top_paths)` containing
sequence log-probabilities.
"""
decoded_ixs, decoded_vals, decoded_shapes, log_probabilities = (
gen_ctc_ops.ctc_beam_search_decoder(
inputs,
sequence_length,
beam_width=beam_width,
top_paths=top_paths,
merge_repeated=merge_repeated))
return ([
sparse_tensor.SparseTensor(ix, val, shape)
for (ix, val, shape) in zip(decoded_ixs, decoded_vals, decoded_shapes)
], log_probabilities)
def ctc_beam_search_decoder(inputs,
sequence_length,
beam_width=100,
top_paths=1,
merge_repeated=True):
"""Performs beam search decoding on the logits given in input.
**Note** The `ctc_greedy_decoder` is a special case of the
`ctc_beam_search_decoder` with `top_paths=1` and `beam_width=1` (but
that decoder is faster for this special case).
If `merge_repeated` is `True`, merge repeated classes in the output beams.
This means that if consecutive entries in a beam are the same,
only the first of these is emitted. That is, when the sequence is
`A B B * B * B` (where '*' is the blank label), the return value is:
* `A B` if `merge_repeated = True`.
* `A B B B` if `merge_repeated = False`.
Args:
inputs: 3-D `float` `Tensor`, size `[max_time x batch_size x num_classes]`.
The logits.
sequence_length: 1-D `int32` vector containing sequence lengths, having size
`[batch_size]`.
beam_width: An int scalar >= 0 (beam search beam width).
top_paths: An int scalar >= 0, <= beam_width (controls output size).
merge_repeated: Boolean. Default: True.
Returns:
A tuple `(decoded, log_probabilities)` where
decoded: A list of length top_paths, where `decoded[j]`
is a `SparseTensor` containing the decoded outputs:
`decoded[j].indices`: Indices matrix `(total_decoded_outputs[j] x 2)`
The rows store: [batch, time].
`decoded[j].values`: Values vector, size `(total_decoded_outputs[j])`.
The vector stores the decoded classes for beam j.
`decoded[j].dense_shape`: Shape vector, size `(2)`.
The shape values are: `[batch_size, max_decoded_length[j]]`.
log_probability: A `float` matrix `(batch_size x top_paths)` containing
sequence log-probabilities.
"""
decoded_ixs, decoded_vals, decoded_shapes, log_probabilities = (
gen_ctc_ops.ctc_beam_search_decoder(
inputs,
sequence_length,
beam_width=beam_width,
top_paths=top_paths,
merge_repeated=merge_repeated))
return ([
sparse_tensor.SparseTensor(ix, val, shape)
for (ix, val, shape) in zip(decoded_ixs, decoded_vals, decoded_shapes)
], log_probabilities)