f0960342ad
This PR integrates LODR (Level-Ordered Deterministic Rescoring) support from Icefall into both online and offline recognizers, enabling LODR for LM shallow fusion and LM rescore. - Extended OnlineLMConfig and OfflineLMConfig to include lodr_fst, lodr_scale, and lodr_backoff_id. - Implemented LodrFst and LodrStateCost classes and wired them into RNN LM scoring in both online and offline code paths. - Updated Python bindings, CLI entry points, examples, and CI test scripts to accept and exercise the new LODR options.
76 lines
1.7 KiB
C++
76 lines
1.7 KiB
C++
// sherpa-onnx/csrc/lodr-fst.h
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//
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// Contains code copied from icefall/utils/ngram_lm.py
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// Copyright (c) 2023 Xiaomi Corporation
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//
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// Copyright (c) 2025 Tilde SIA (Askars Salimbajevs)
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#ifndef SHERPA_ONNX_CSRC_LODR_FST_H_
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#define SHERPA_ONNX_CSRC_LODR_FST_H_
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#include <memory>
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#include <string>
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#include <vector>
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#include <optional>
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#include <tuple>
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#include <unordered_map>
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#include <limits>
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#include <algorithm>
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#include <utility>
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#include "kaldifst/csrc/kaldi-fst-io.h"
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namespace sherpa_onnx {
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class Hypothesis;
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class LodrFst {
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public:
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explicit LodrFst(const std::string &fst_path, int32_t backoff_id = -1);
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std::pair<std::vector<int32_t>, std::vector<float>> GetNextStateCosts(
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int32_t state, int32_t label);
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float GetFinalCost(int32_t state);
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void ComputeScore(float scale, Hypothesis *hyp, int32_t offset);
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private:
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fst::StdVectorFst YsToFst(const std::vector<int64_t> &ys, int32_t offset);
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std::vector<std::tuple<int32_t, float>> ProcessBackoffArcs(
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int32_t state, float cost);
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std::optional<std::tuple<int32_t, float>> GetNextStatesCostsNoBackoff(
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int32_t state, int32_t label);
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int32_t FindBackoffId();
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int32_t backoff_id_ = -1;
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std::unique_ptr<fst::StdConstFst> fst_; // owned by this class
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};
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class LodrStateCost {
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public:
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explicit LodrStateCost(
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LodrFst* fst,
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const std::unordered_map<int32_t, float> &state_cost = {});
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LodrStateCost ForwardOneStep(int32_t label);
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float Score() const;
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float FinalScore() const;
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private:
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// The fst_ is not owned by this class and borrowed from the caller
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// (e.g. OnlineRnnLM).
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LodrFst* fst_;
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std::unordered_map<int32_t, float> state_cost_;
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};
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} // namespace sherpa_onnx
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#endif // SHERPA_ONNX_CSRC_LODR_FST_H_
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