libtorch-runtime/fst/script/determinize.h

// Copyright 2005-2024 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the 'License');
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an 'AS IS' BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// See www.openfst.org for extensive documentation on this weighted
// finite-state transducer library.

#ifndef FST_SCRIPT_DETERMINIZE_H_
#define FST_SCRIPT_DETERMINIZE_H_

#include <cstdint>
#include <tuple>

#include <fst/determinize.h>
#include <fst/fst.h>
#include <fst/mutable-fst.h>
#include <fst/script/fst-class.h>
#include <fst/script/weight-class.h>

namespace fst {
namespace script {

struct DeterminizeOptions {
  const float delta;
  const WeightClass &weight_threshold;
  const int64_t state_threshold;
  const int64_t subsequential_label;
  const DeterminizeType det_type;
  const bool increment_subsequential_label;

  DeterminizeOptions(float delta, const WeightClass &weight_threshold,
                     int64_t state_threshold = kNoStateId,
                     int64_t subsequential_label = 0,
                     DeterminizeType det_type = DETERMINIZE_FUNCTIONAL,
                     bool increment_subsequential_label = false)
      : delta(delta),
        weight_threshold(weight_threshold),
        state_threshold(state_threshold),
        subsequential_label(subsequential_label),
        det_type(det_type),
        increment_subsequential_label(increment_subsequential_label) {}
};

using FstDeterminizeArgs =
    std::tuple<const FstClass &, MutableFstClass *, const DeterminizeOptions &>;

template <class Arc>
void Determinize(FstDeterminizeArgs *args) {
  using Weight = typename Arc::Weight;
  const Fst<Arc> &ifst = *std::get<0>(*args).GetFst<Arc>();
  MutableFst<Arc> *ofst = std::get<1>(*args)->GetMutableFst<Arc>();
  const auto &opts = std::get<2>(*args);
  const auto weight_threshold = *opts.weight_threshold.GetWeight<Weight>();
  const fst::DeterminizeOptions<Arc> detargs(
      opts.delta, weight_threshold, opts.state_threshold,
      opts.subsequential_label, opts.det_type,
      opts.increment_subsequential_label);
  Determinize(ifst, ofst, detargs);
}

void Determinize(const FstClass &ifst, MutableFstClass *ofst,
                 const DeterminizeOptions &opts);

}  // namespace script
}  // namespace fst

#endif  // FST_SCRIPT_DETERMINIZE_H_