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133 lines
4.1 KiB
C++
133 lines
4.1 KiB
C++
#ifndef CTC_BEAM_SEARCH_DECODER_H_
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#define CTC_BEAM_SEARCH_DECODER_H_
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#include <memory>
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#include <string>
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#include <vector>
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#include "scorer.h"
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#include "output.h"
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#include "alphabet.h"
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class DecoderState {
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int abs_time_step_;
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int space_id_;
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int blank_id_;
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size_t beam_size_;
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double cutoff_prob_;
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size_t cutoff_top_n_;
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std::shared_ptr<Scorer> ext_scorer_;
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std::vector<PathTrie*> prefixes_;
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std::unique_ptr<PathTrie> prefix_root_;
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public:
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DecoderState() = default;
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~DecoderState() = default;
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// Disallow copying
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DecoderState(const DecoderState&) = delete;
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DecoderState& operator=(DecoderState&) = delete;
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/* Initialize CTC beam search decoder
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*
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* Parameters:
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* alphabet: The alphabet.
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* beam_size: The width of beam search.
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* cutoff_prob: Cutoff probability for pruning.
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* cutoff_top_n: Cutoff number for pruning.
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* ext_scorer: External scorer to evaluate a prefix, which consists of
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* n-gram language model scoring and word insertion term.
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* Default null, decoding the input sample without scorer.
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* Return:
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* Zero on success, non-zero on failure.
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*/
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int init(const Alphabet& alphabet,
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size_t beam_size,
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double cutoff_prob,
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size_t cutoff_top_n,
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std::shared_ptr<Scorer> ext_scorer);
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/* Send data to the decoder
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*
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* Parameters:
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* probs: 2-D vector where each element is a vector of probabilities
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* over alphabet of one time step.
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* time_dim: Number of timesteps.
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* class_dim: Number of classes (alphabet length + 1 for space character).
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*/
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void next(const double *probs,
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int time_dim,
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int class_dim);
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/* Get transcription from current decoder state
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*
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* Return:
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* A vector where each element is a pair of score and decoding result,
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* in descending order.
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*/
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std::vector<Output> decode() const;
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};
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/* CTC Beam Search Decoder
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* Parameters:
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* probs: 2-D vector where each element is a vector of probabilities
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* over alphabet of one time step.
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* time_dim: Number of timesteps.
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* class_dim: Alphabet length (plus 1 for space character).
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* alphabet: The alphabet.
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* beam_size: The width of beam search.
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* cutoff_prob: Cutoff probability for pruning.
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* cutoff_top_n: Cutoff number for pruning.
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* ext_scorer: External scorer to evaluate a prefix, which consists of
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* n-gram language model scoring and word insertion term.
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* Default null, decoding the input sample without scorer.
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* Return:
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* A vector where each element is a pair of score and decoding result,
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* in descending order.
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*/
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std::vector<Output> ctc_beam_search_decoder(
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const double* probs,
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int time_dim,
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int class_dim,
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const Alphabet &alphabet,
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size_t beam_size,
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double cutoff_prob,
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size_t cutoff_top_n,
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std::shared_ptr<Scorer> ext_scorer);
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/* CTC Beam Search Decoder for batch data
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* Parameters:
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* probs: 3-D vector where each element is a 2-D vector that can be used
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* by ctc_beam_search_decoder().
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* alphabet: The alphabet.
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* beam_size: The width of beam search.
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* num_processes: Number of threads for beam search.
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* cutoff_prob: Cutoff probability for pruning.
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* cutoff_top_n: Cutoff number for pruning.
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* ext_scorer: External scorer to evaluate a prefix, which consists of
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* n-gram language model scoring and word insertion term.
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* Default null, decoding the input sample without scorer.
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* Return:
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* A 2-D vector where each element is a vector of beam search decoding
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* result for one audio sample.
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*/
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std::vector<std::vector<Output>>
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ctc_beam_search_decoder_batch(
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const double* probs,
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int batch_size,
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int time_dim,
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int class_dim,
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const int* seq_lengths,
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int seq_lengths_size,
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const Alphabet &alphabet,
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size_t beam_size,
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size_t num_processes,
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double cutoff_prob,
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size_t cutoff_top_n,
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std::shared_ptr<Scorer> ext_scorer);
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#endif // CTC_BEAM_SEARCH_DECODER_H_
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