FST  openfst-1.6.1
OpenFst Library
replace.h
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1 // See www.openfst.org for extensive documentation on this weighted
2 // finite-state transducer library.
3 //
4 // Functions and classes for the recursive replacement of FSTs.
5 
6 #ifndef FST_LIB_REPLACE_H_
7 #define FST_LIB_REPLACE_H_
8 
9 #include <set>
10 #include <string>
11 #include <unordered_map>
12 #include <utility>
13 #include <vector>
14 
15 #include <fst/log.h>
16 
17 #include <fst/cache.h>
18 #include <fst/expanded-fst.h>
19 #include <fst/fst-decl.h> // For optional argument declarations.
20 #include <fst/fst.h>
21 #include <fst/matcher.h>
22 #include <fst/replace-util.h>
23 #include <fst/state-table.h>
24 #include <fst/test-properties.h>
25 
26 namespace fst {
27 
28 // Replace state tables have the form:
29 //
30 // template <class Arc, class P>
31 // class ReplaceStateTable {
32 // public:
33 // using Label = typename Arc::Label Label;
34 // using StateId = typename Arc::StateId;
35 //
36 // using PrefixId = P;
37 // using StateTuple = ReplaceStateTuple<StateId, PrefixId>;
38 // using StackPrefix = ReplaceStackPrefix<Label, StateId>;
39 //
40 // // Required constructor.
41 // ReplaceStateTable(
42 // const std::vector<std::pair<Label, const Fst<Arc> *>> &fst_list,
43 // Label root);
44 //
45 // // Required copy constructor that does not copy state.
46 // ReplaceStateTable(const ReplaceStateTable<Arc, PrefixId> &table);
47 //
48 // // Looks up state ID by tuple, adding it if it doesn't exist.
49 // StateId FindState(const StateTuple &tuple);
50 //
51 // // Looks up state tuple by ID.
52 // const StateTuple &Tuple(StateId id) const;
53 //
54 // // Lookus up prefix ID by stack prefix, adding it if it doesn't exist.
55 // PrefixId FindPrefixId(const StackPrefix &stack_prefix);
56 //
57 // // Looks up stack prefix by ID.
58 // const StackPrefix &GetStackPrefix(PrefixId id) const;
59 // };
60 
61 // Tuple that uniquely defines a state in replace.
62 template <class S, class P>
64  using StateId = S;
65  using PrefixId = P;
66 
70 
71  PrefixId prefix_id; // Index in prefix table.
72  StateId fst_id; // Current FST being walked.
73  StateId fst_state; // Current state in FST being walked (not to be
74  // confused with the thse StateId of the combined FST).
75 };
76 
77 // Equality of replace state tuples.
78 template <class StateId, class PrefixId>
81  return x.prefix_id == y.prefix_id && x.fst_id == y.fst_id &&
82  x.fst_state == y.fst_state;
83 }
84 
85 // Functor returning true for tuples corresponding to states in the root FST.
86 template <class StateId, class PrefixId>
88  public:
90  return tuple.prefix_id == 0;
91  }
92 };
93 
94 // Functor for fingerprinting replace state tuples.
95 template <class StateId, class PrefixId>
97  public:
98  explicit ReplaceFingerprint(const std::vector<uint64> *size_array)
99  : size_array_(size_array) {}
100 
102  return tuple.prefix_id * size_array_->back() +
103  size_array_->at(tuple.fst_id - 1) + tuple.fst_state;
104  }
105 
106  private:
107  const std::vector<uint64> *size_array_;
108 };
109 
110 // Useful when the fst_state uniquely define the tuple.
111 template <class StateId, class PrefixId>
113  public:
115  return tuple.fst_state;
116  }
117 };
118 
119 // A generic hash function for replace state tuples.
120 template <typename S, typename P>
121 class ReplaceHash {
122  public:
123  size_t operator()(const ReplaceStateTuple<S, P>& t) const {
124  static constexpr auto prime0 = 7853;
125  static constexpr auto prime1 = 7867;
126  return t.prefix_id + t.fst_id * prime0 + t.fst_state * prime1;
127  }
128 };
129 
130 // Container for stack prefix.
131 template <class Label, class StateId>
133  public:
134  struct PrefixTuple {
136  : fst_id(fst_id), nextstate(nextstate) {}
137 
138  Label fst_id;
140  };
141 
143 
145  : prefix_(other.prefix_) {}
146 
147  void Push(StateId fst_id, StateId nextstate) {
148  prefix_.push_back(PrefixTuple(fst_id, nextstate));
149  }
150 
151  void Pop() { prefix_.pop_back(); }
152 
153  const PrefixTuple &Top() const { return prefix_[prefix_.size() - 1]; }
154 
155  size_t Depth() const { return prefix_.size(); }
156 
157  public:
158  std::vector<PrefixTuple> prefix_;
159 };
160 
161 // Equality stack prefix classes.
162 template <class Label, class StateId>
165  if (x.prefix_.size() != y.prefix_.size()) return false;
166  for (size_t i = 0; i < x.prefix_.size(); ++i) {
167  if (x.prefix_[i].fst_id != y.prefix_[i].fst_id ||
168  x.prefix_[i].nextstate != y.prefix_[i].nextstate) {
169  return false;
170  }
171  }
172  return true;
173 }
174 
175 // Hash function for stack prefix to prefix id.
176 template <class Label, class StateId>
178  public:
179  size_t operator()(const ReplaceStackPrefix<Label, StateId> &prefix) const {
180  size_t sum = 0;
181  for (const auto &pair : prefix.prefix_) {
182  static constexpr auto prime = 7863;
183  sum += pair.fst_id + pair.nextstate * prime;
184  }
185  return sum;
186  }
187 };
188 
189 // Replace state tables.
190 
191 // A two-level state table for replace. Warning: calls CountStates to compute
192 // the number of states of each component FST.
193 template <class Arc, class P = ssize_t>
195  public:
196  using Label = typename Arc::Label;
197  using StateId = typename Arc::StateId;
198 
199  using PrefixId = P;
200 
202  using StateTable =
208  using StackPrefixTable =
211 
213  const std::vector<std::pair<Label, const Fst<Arc> *>> &fst_list,
214  Label root)
215  : root_size_(0) {
216  size_array_.push_back(0);
217  for (const auto &fst_pair : fst_list) {
218  if (fst_pair.first == root) {
219  root_size_ = CountStates(*(fst_pair.second));
220  size_array_.push_back(size_array_.back());
221  } else {
222  size_array_.push_back(size_array_.back() +
223  CountStates(*(fst_pair.second)));
224  }
225  }
226  state_table_.reset(
227  new StateTable(new ReplaceRootSelector<StateId, PrefixId>,
228  new ReplaceFstStateFingerprint<StateId, PrefixId>,
229  new ReplaceFingerprint<StateId, PrefixId>(&size_array_),
230  root_size_, root_size_ + size_array_.back()));
231  }
232 
235  : root_size_(table.root_size_),
236  size_array_(table.size_array_),
237  prefix_table_(table.prefix_table_) {
238  state_table_.reset(
239  new StateTable(new ReplaceRootSelector<StateId, PrefixId>,
240  new ReplaceFstStateFingerprint<StateId, PrefixId>,
241  new ReplaceFingerprint<StateId, PrefixId>(&size_array_),
242  root_size_, root_size_ + size_array_.back()));
243  }
244 
245  StateId FindState(const StateTuple &tuple) {
246  return state_table_->FindState(tuple);
247  }
248 
249  const StateTuple &Tuple(StateId id) const { return state_table_->Tuple(id); }
250 
251  PrefixId FindPrefixId(const StackPrefix &prefix) {
252  return prefix_table_.FindId(prefix);
253  }
254 
255  const StackPrefix& GetStackPrefix(PrefixId id) const {
256  return prefix_table_.FindEntry(id);
257  }
258 
259  private:
260  StateId root_size_;
261  std::vector<uint64> size_array_;
262  std::unique_ptr<StateTable> state_table_;
263  StackPrefixTable prefix_table_;
264 };
265 
266 // Default replace state table.
267 template <class Arc, class P /* = size_t */>
269  : public CompactHashStateTable<ReplaceStateTuple<typename Arc::StateId, P>,
270  ReplaceHash<typename Arc::StateId, P>> {
271  public:
272  using Label = typename Arc::Label;
273  using StateId = typename Arc::StateId;
274 
275  using PrefixId = P;
277  using StateTable =
280  using StackPrefixTable =
283 
284  using StateTable::FindState;
285  using StateTable::Tuple;
286 
288  const std::vector<std::pair<Label, const Fst<Arc> *>> &, Label) {}
289 
291  : StateTable(), prefix_table_(table.prefix_table_) {}
292 
293  PrefixId FindPrefixId(const StackPrefix &prefix) {
294  return prefix_table_.FindId(prefix);
295  }
296 
297  const StackPrefix &GetStackPrefix(PrefixId id) const {
298  return prefix_table_.FindEntry(id);
299  }
300 
301  private:
302  StackPrefixTable prefix_table_;
303 };
304 
305 // By default ReplaceFst will copy the input label of the replace arc.
306 // The call_label_type and return_label_type options specify how to manage
307 // the labels of the call arc and the return arc of the replace FST
308 template <class Arc, class StateTable = DefaultReplaceStateTable<Arc>,
309  class CacheStore = DefaultCacheStore<Arc>>
310 struct ReplaceFstOptions : CacheImplOptions<CacheStore> {
311  using Label = typename Arc::Label;
312 
313  // Index of root rule for expansion.
315  // How to label call arc.
317  // How to label return arc.
319  // Specifies output label to put on call arc; if kNoLabel, use existing label
320  // on call arc. Otherwise, use this field as the output label.
321  Label call_output_label = kNoLabel;
322  // Specifies label to put on return arc.
323  Label return_label = 0;
324  // Take ownership of input FSTs?
325  bool take_ownership = false;
326  // Pointer to optional pre-constructed state table.
327  StateTable *state_table = nullptr;
328 
330  Label root = kNoLabel)
331  : CacheImplOptions<CacheStore>(opts), root(root) {}
332 
333  explicit ReplaceFstOptions(const CacheOptions &opts, Label root = kNoLabel)
334  : CacheImplOptions<CacheStore>(opts), root(root) {}
335 
336  // FIXME(kbg): There are too many constructors here. Come up with a consistent
337  // position for call_output_label (probably the very end) so that it is
338  // possible to express all the remaining constructors with a single
339  // default-argument constructor. Also move clients off of the "backwards
340  // compatibility" constructor, for good.
341 
342  explicit ReplaceFstOptions(Label root) : root(root) {}
343 
344  explicit ReplaceFstOptions(Label root, ReplaceLabelType call_label_type,
345  ReplaceLabelType return_label_type,
346  Label return_label)
347  : root(root),
348  call_label_type(call_label_type),
349  return_label_type(return_label_type),
350  return_label(return_label) {}
351 
352  explicit ReplaceFstOptions(Label root, ReplaceLabelType call_label_type,
353  ReplaceLabelType return_label_type,
354  Label call_output_label, Label return_label)
355  : root(root),
356  call_label_type(call_label_type),
357  return_label_type(return_label_type),
358  call_output_label(call_output_label),
359  return_label(return_label) {}
360 
361  explicit ReplaceFstOptions(const ReplaceUtilOptions &opts)
362  : ReplaceFstOptions(opts.root, opts.call_label_type,
363  opts.return_label_type, opts.return_label) {}
364 
366 
367  // For backwards compatibility.
368  ReplaceFstOptions(int64 root, bool epsilon_replace_arc)
369  : root(root),
370  call_label_type(epsilon_replace_arc ? REPLACE_LABEL_NEITHER
372  call_output_label(epsilon_replace_arc ? 0 : kNoLabel) {}
373 };
374 
375 // Forward declaration.
376 template <class Arc, class StateTable, class CacheStore>
378 
379 template <class Arc>
380 using FstList = std::vector<std::pair<typename Arc::Label, const Fst<Arc> *>>;
381 
382 // Returns true if label type on arc results in epsilon input label.
383 inline bool EpsilonOnInput(ReplaceLabelType label_type) {
384  return label_type == REPLACE_LABEL_NEITHER ||
385  label_type == REPLACE_LABEL_OUTPUT;
386 }
387 
388 // Returns true if label type on arc results in epsilon input label.
389 inline bool EpsilonOnOutput(ReplaceLabelType label_type) {
390  return label_type == REPLACE_LABEL_NEITHER ||
391  label_type == REPLACE_LABEL_INPUT;
392 }
393 
394 // Returns true if for either the call or return arc ilabel != olabel.
395 template <class Label>
396 bool ReplaceTransducer(ReplaceLabelType call_label_type,
397  ReplaceLabelType return_label_type,
398  Label call_output_label) {
399  return call_label_type == REPLACE_LABEL_INPUT ||
400  call_label_type == REPLACE_LABEL_OUTPUT ||
401  (call_label_type == REPLACE_LABEL_BOTH &&
402  call_output_label != kNoLabel) ||
403  return_label_type == REPLACE_LABEL_INPUT ||
404  return_label_type == REPLACE_LABEL_OUTPUT;
405 }
406 
407 template <class Arc>
408 uint64 ReplaceFstProperties(typename Arc::Label root_label,
409  const FstList<Arc> &fst_list,
410  ReplaceLabelType call_label_type,
411  ReplaceLabelType return_label_type,
412  typename Arc::Label call_output_label,
413  bool *sorted_and_non_empty) {
414  using Label = typename Arc::Label;
415  std::vector<uint64> inprops;
416  bool all_ilabel_sorted = true;
417  bool all_olabel_sorted = true;
418  bool all_non_empty = true;
419  // All nonterminals are negative?
420  bool all_negative = true;
421  // All nonterminals are positive and form a dense range containing 1?
422  bool dense_range = true;
423  Label root_fst_idx = 0;
424  for (Label i = 0; i < fst_list.size(); ++i) {
425  const auto label = fst_list[i].first;
426  if (label >= 0) all_negative = false;
427  if (label > fst_list.size() || label <= 0) dense_range = false;
428  if (label == root_label) root_fst_idx = i;
429  const auto *fst = fst_list[i].second;
430  if (fst->Start() == kNoStateId) all_non_empty = false;
431  if (!fst->Properties(kILabelSorted, false)) all_ilabel_sorted = false;
432  if (!fst->Properties(kOLabelSorted, false)) all_olabel_sorted = false;
433  inprops.push_back(fst->Properties(kCopyProperties, false));
434  }
435  const auto props = ReplaceProperties(
436  inprops, root_fst_idx, EpsilonOnInput(call_label_type),
437  EpsilonOnInput(return_label_type), EpsilonOnOutput(call_label_type),
438  EpsilonOnOutput(return_label_type),
439  ReplaceTransducer(call_label_type, return_label_type, call_output_label),
440  all_non_empty, all_ilabel_sorted, all_olabel_sorted,
441  all_negative || dense_range);
442  const bool sorted = props & (kILabelSorted | kOLabelSorted);
443  *sorted_and_non_empty = all_non_empty && sorted;
444  return props;
445 }
446 
447 namespace internal {
448 
449 // The replace implementation class supports a dynamic expansion of a recursive
450 // transition network represented as label/FST pairs with dynamic replacable
451 // arcs.
452 template <class Arc, class StateTable, class CacheStore>
454  : public CacheBaseImpl<typename CacheStore::State, CacheStore> {
455  public:
456  using Label = typename Arc::Label;
457  using StateId = typename Arc::StateId;
458  using Weight = typename Arc::Weight;
459 
460  using State = typename CacheStore::State;
462  using PrefixId = typename StateTable::PrefixId;
465  using NonTerminalHash = std::unordered_map<Label, Label>;
466 
467  using FstImpl<Arc>::SetType;
474 
475  using CacheImpl::PushArc;
476  using CacheImpl::HasArcs;
477  using CacheImpl::HasFinal;
478  using CacheImpl::HasStart;
479  using CacheImpl::SetArcs;
480  using CacheImpl::SetFinal;
481  using CacheImpl::SetStart;
482 
483  friend class ReplaceFstMatcher<Arc, StateTable, CacheStore>;
484 
485  ReplaceFstImpl(const FstList<Arc> &fst_list,
487  : CacheImpl(opts),
488  call_label_type_(opts.call_label_type),
489  return_label_type_(opts.return_label_type),
490  call_output_label_(opts.call_output_label),
491  return_label_(opts.return_label),
492  state_table_(opts.state_table ? opts.state_table
493  : new StateTable(fst_list, opts.root)) {
494  SetType("replace");
495  // If the label is epsilon, then all replace label options are equivalent,
496  // so we set the label types to NEITHER for simplicity.
497  if (call_output_label_ == 0) call_label_type_ = REPLACE_LABEL_NEITHER;
498  if (return_label_ == 0) return_label_type_ = REPLACE_LABEL_NEITHER;
499  if (!fst_list.empty()) {
500  SetInputSymbols(fst_list[0].second->InputSymbols());
501  SetOutputSymbols(fst_list[0].second->OutputSymbols());
502  }
503  fst_array_.push_back(nullptr);
504  for (Label i = 0; i < fst_list.size(); ++i) {
505  const auto label = fst_list[i].first;
506  const auto *fst = fst_list[i].second;
507  nonterminal_hash_[label] = fst_array_.size();
508  nonterminal_set_.insert(label);
509  fst_array_.emplace_back(opts.take_ownership ? fst : fst->Copy());
510  if (i) {
511  if (!CompatSymbols(InputSymbols(), fst->InputSymbols())) {
512  FSTERROR() << "ReplaceFstImpl: Input symbols of FST " << i
513  << " do not match input symbols of base FST (0th FST)";
514  SetProperties(kError, kError);
515  }
516  if (!CompatSymbols(OutputSymbols(), fst->OutputSymbols())) {
517  FSTERROR() << "ReplaceFstImpl: Output symbols of FST " << i
518  << " do not match output symbols of base FST (0th FST)";
519  SetProperties(kError, kError);
520  }
521  }
522  }
523  const auto nonterminal = nonterminal_hash_[opts.root];
524  if ((nonterminal == 0) && (fst_array_.size() > 1)) {
525  FSTERROR() << "ReplaceFstImpl: No FST corresponding to root label "
526  << opts.root << " in the input tuple vector";
527  SetProperties(kError, kError);
528  }
529  root_ = (nonterminal > 0) ? nonterminal : 1;
530  bool all_non_empty_and_sorted = false;
531  SetProperties(ReplaceFstProperties(opts.root, fst_list, call_label_type_,
532  return_label_type_, call_output_label_,
533  &all_non_empty_and_sorted));
534  // Enables optional caching as long as sorted and all non-empty.
535  always_cache_ = !all_non_empty_and_sorted;
536  VLOG(2) << "ReplaceFstImpl::ReplaceFstImpl: always_cache = "
537  << (always_cache_ ? "true" : "false");
538  }
539 
541  : CacheImpl(impl),
542  call_label_type_(impl.call_label_type_),
543  return_label_type_(impl.return_label_type_),
544  call_output_label_(impl.call_output_label_),
545  return_label_(impl.return_label_),
546  always_cache_(impl.always_cache_),
547  state_table_(new StateTable(*(impl.state_table_))),
548  nonterminal_set_(impl.nonterminal_set_),
549  nonterminal_hash_(impl.nonterminal_hash_),
550  root_(impl.root_) {
551  SetType("replace");
552  SetProperties(impl.Properties(), kCopyProperties);
553  SetInputSymbols(impl.InputSymbols());
554  SetOutputSymbols(impl.OutputSymbols());
555  fst_array_.reserve(impl.fst_array_.size());
556  fst_array_.emplace_back(nullptr);
557  for (Label i = 1; i < impl.fst_array_.size(); ++i) {
558  fst_array_.emplace_back(impl.fst_array_[i]->Copy(true));
559  }
560  }
561 
562  // Computes the dependency graph of the replace class and returns
563  // true if the dependencies are cyclic. Cyclic dependencies will result
564  // in an un-expandable FST.
565  bool CyclicDependencies() const {
566  const ReplaceUtilOptions opts(root_);
567  ReplaceUtil<Arc> replace_util(fst_array_, nonterminal_hash_, opts);
568  return replace_util.CyclicDependencies();
569  }
570 
572  if (!HasStart()) {
573  if (fst_array_.size() == 1) {
574  SetStart(kNoStateId);
575  return kNoStateId;
576  } else {
577  const auto fst_start = fst_array_[root_]->Start();
578  if (fst_start == kNoStateId) return kNoStateId;
579  const auto prefix = GetPrefixId(StackPrefix());
580  const auto start =
581  state_table_->FindState(StateTuple(prefix, root_, fst_start));
582  SetStart(start);
583  return start;
584  }
585  } else {
586  return CacheImpl::Start();
587  }
588  }
589 
591  if (HasFinal(s)) return CacheImpl::Final(s);
592  const auto &tuple = state_table_->Tuple(s);
593  auto weight = Weight::Zero();
594  if (tuple.prefix_id == 0) {
595  const auto fst_state = tuple.fst_state;
596  weight = fst_array_[tuple.fst_id]->Final(fst_state);
597  }
598  if (always_cache_ || HasArcs(s)) SetFinal(s, weight);
599  return weight;
600  }
601 
602  size_t NumArcs(StateId s) {
603  if (HasArcs(s)) {
604  return CacheImpl::NumArcs(s);
605  } else if (always_cache_) { // If always caching, expands and caches state.
606  Expand(s);
607  return CacheImpl::NumArcs(s);
608  } else { // Otherwise computes the number of arcs without expanding.
609  const auto tuple = state_table_->Tuple(s);
610  if (tuple.fst_state == kNoStateId) return 0;
611  auto num_arcs = fst_array_[tuple.fst_id]->NumArcs(tuple.fst_state);
612  if (ComputeFinalArc(tuple, nullptr)) ++num_arcs;
613  return num_arcs;
614  }
615  }
616 
617  // Returns whether a given label is a non-terminal.
618  bool IsNonTerminal(Label label) const {
619  if (label < *nonterminal_set_.begin() ||
620  label > *nonterminal_set_.rbegin()) {
621  return false;
622  } else {
623  return nonterminal_hash_.count(label);
624  }
625  // TODO(allauzen): be smarter and take advantage of all_dense or
626  // all_negative. Also use this in ComputeArc. This would require changes to
627  // Replace so that recursing into an empty FST lead to a non co-accessible
628  // state instead of deleting the arc as done currently. The current use
629  // correct, since labels are sorted if all_non_empty is true.
630  }
631 
633  if (HasArcs(s)) {
634  return CacheImpl::NumInputEpsilons(s);
635  } else if (always_cache_ || !Properties(kILabelSorted)) {
636  // If always caching or if the number of input epsilons is too expensive
637  // to compute without caching (i.e., not ilabel-sorted), then expands and
638  // caches state.
639  Expand(s);
640  return CacheImpl::NumInputEpsilons(s);
641  } else {
642  // Otherwise, computes the number of input epsilons without caching.
643  const auto tuple = state_table_->Tuple(s);
644  if (tuple.fst_state == kNoStateId) return 0;
645  size_t num = 0;
646  if (!EpsilonOnInput(call_label_type_)) {
647  // If EpsilonOnInput(c) is false, all input epsilon arcs
648  // are also input epsilons arcs in the underlying machine.
649  num = fst_array_[tuple.fst_id]->NumInputEpsilons(tuple.fst_state);
650  } else {
651  // Otherwise, one need to consider that all non-terminal arcs
652  // in the underlying machine also become input epsilon arc.
653  ArcIterator<Fst<Arc>> aiter(*fst_array_[tuple.fst_id], tuple.fst_state);
654  for (; !aiter.Done() && ((aiter.Value().ilabel == 0) ||
655  IsNonTerminal(aiter.Value().olabel));
656  aiter.Next()) {
657  ++num;
658  }
659  }
660  if (EpsilonOnInput(return_label_type_) &&
661  ComputeFinalArc(tuple, nullptr)) {
662  ++num;
663  }
664  return num;
665  }
666  }
667 
669  if (HasArcs(s)) {
671  } else if (always_cache_ || !Properties(kOLabelSorted)) {
672  // If always caching or if the number of output epsilons is too expensive
673  // to compute without caching (i.e., not olabel-sorted), then expands and
674  // caches state.
675  Expand(s);
677  } else {
678  // Otherwise, computes the number of output epsilons without caching.
679  const auto tuple = state_table_->Tuple(s);
680  if (tuple.fst_state == kNoStateId) return 0;
681  size_t num = 0;
682  if (!EpsilonOnOutput(call_label_type_)) {
683  // If EpsilonOnOutput(c) is false, all output epsilon arcs are also
684  // output epsilons arcs in the underlying machine.
685  num = fst_array_[tuple.fst_id]->NumOutputEpsilons(tuple.fst_state);
686  } else {
687  // Otherwise, one need to consider that all non-terminal arcs in the
688  // underlying machine also become output epsilon arc.
689  ArcIterator<Fst<Arc>> aiter(*fst_array_[tuple.fst_id], tuple.fst_state);
690  for (; !aiter.Done() && ((aiter.Value().olabel == 0) ||
691  IsNonTerminal(aiter.Value().olabel));
692  aiter.Next()) {
693  ++num;
694  }
695  }
696  if (EpsilonOnOutput(return_label_type_) &&
697  ComputeFinalArc(tuple, nullptr)) {
698  ++num;
699  }
700  return num;
701  }
702  }
703 
704  uint64 Properties() const override { return Properties(kFstProperties); }
705 
706  // Sets error if found, and returns other FST impl properties.
707  uint64 Properties(uint64 mask) const override {
708  if (mask & kError) {
709  for (Label i = 1; i < fst_array_.size(); ++i) {
710  if (fst_array_[i]->Properties(kError, false)) {
711  SetProperties(kError, kError);
712  }
713  }
714  }
715  return FstImpl<Arc>::Properties(mask);
716  }
717 
718  // Returns the base arc iterator, and if arcs have not been computed yet,
719  // extends and recurses for new arcs.
721  if (!HasArcs(s)) Expand(s);
722  CacheImpl::InitArcIterator(s, data);
723  // TODO(allauzen): Set behaviour of generic iterator.
724  // Warning: ArcIterator<ReplaceFst<A>>::InitCache() relies on current
725  // behaviour.
726  }
727 
728  // Extends current state (walk arcs one level deep).
729  void Expand(StateId s) {
730  const auto tuple = state_table_->Tuple(s);
731  if (tuple.fst_state == kNoStateId) { // Local FST is empty.
732  SetArcs(s);
733  return;
734  }
735  ArcIterator<Fst<Arc>> aiter(*fst_array_[tuple.fst_id], tuple.fst_state);
736  Arc arc;
737  // Creates a final arc when needed.
738  if (ComputeFinalArc(tuple, &arc)) PushArc(s, arc);
739  // Expands all arcs leaving the state.
740  for (; !aiter.Done(); aiter.Next()) {
741  if (ComputeArc(tuple, aiter.Value(), &arc)) PushArc(s, arc);
742  }
743  SetArcs(s);
744  }
745 
746  void Expand(StateId s, const StateTuple &tuple,
747  const ArcIteratorData<Arc> &data) {
748  if (tuple.fst_state == kNoStateId) { // Local FST is empty.
749  SetArcs(s);
750  return;
751  }
752  ArcIterator<Fst<Arc>> aiter(data);
753  Arc arc;
754  // Creates a final arc when needed.
755  if (ComputeFinalArc(tuple, &arc)) AddArc(s, arc);
756  // Expands all arcs leaving the state.
757  for (; !aiter.Done(); aiter.Next()) {
758  if (ComputeArc(tuple, aiter.Value(), &arc)) AddArc(s, arc);
759  }
760  SetArcs(s);
761  }
762 
763  // If acpp is null, only returns true if a final arcp is required, but does
764  // not actually compute it.
765  bool ComputeFinalArc(const StateTuple &tuple, Arc *arcp,
766  uint32 flags = kArcValueFlags) {
767  const auto fst_state = tuple.fst_state;
768  if (fst_state == kNoStateId) return false;
769  // If state is final, pops the stack.
770  if (fst_array_[tuple.fst_id]->Final(fst_state) != Weight::Zero() &&
771  tuple.prefix_id) {
772  if (arcp) {
773  arcp->ilabel = (EpsilonOnInput(return_label_type_)) ? 0 : return_label_;
774  arcp->olabel =
775  (EpsilonOnOutput(return_label_type_)) ? 0 : return_label_;
776  if (flags & kArcNextStateValue) {
777  const auto &stack = state_table_->GetStackPrefix(tuple.prefix_id);
778  const auto prefix_id = PopPrefix(stack);
779  const auto &top = stack.Top();
780  arcp->nextstate = state_table_->FindState(
781  StateTuple(prefix_id, top.fst_id, top.nextstate));
782  }
783  if (flags & kArcWeightValue) {
784  arcp->weight = fst_array_[tuple.fst_id]->Final(fst_state);
785  }
786  }
787  return true;
788  } else {
789  return false;
790  }
791  }
792 
793  // Computes an arc in the FST corresponding to one in the underlying machine.
794  // Returns false if the underlying arc corresponds to no arc in the resulting
795  // FST.
796  bool ComputeArc(const StateTuple &tuple, const Arc &arc, Arc *arcp,
797  uint32 flags = kArcValueFlags) {
798  if (!EpsilonOnInput(call_label_type_) &&
799  (flags == (flags & (kArcILabelValue | kArcWeightValue)))) {
800  *arcp = arc;
801  return true;
802  }
803  if (arc.olabel == 0 || arc.olabel < *nonterminal_set_.begin() ||
804  arc.olabel > *nonterminal_set_.rbegin()) { // Expands local FST.
805  const auto nextstate =
806  flags & kArcNextStateValue
807  ? state_table_->FindState(
808  StateTuple(tuple.prefix_id, tuple.fst_id, arc.nextstate))
809  : kNoStateId;
810  *arcp = Arc(arc.ilabel, arc.olabel, arc.weight, nextstate);
811  } else {
812  // Checks for non-terminal.
813  const auto it = nonterminal_hash_.find(arc.olabel);
814  if (it != nonterminal_hash_.end()) { // Recurses into non-terminal.
815  const auto nonterminal = it->second;
816  const auto nt_prefix =
817  PushPrefix(state_table_->GetStackPrefix(tuple.prefix_id),
818  tuple.fst_id, arc.nextstate);
819  // If the start state is valid, replace; othewise, the arc is implicitly
820  // deleted.
821  const auto nt_start = fst_array_[nonterminal]->Start();
822  if (nt_start != kNoStateId) {
823  const auto nt_nextstate = flags & kArcNextStateValue
824  ? state_table_->FindState(StateTuple(
825  nt_prefix, nonterminal, nt_start))
826  : kNoStateId;
827  const auto ilabel =
828  (EpsilonOnInput(call_label_type_)) ? 0 : arc.ilabel;
829  const auto olabel =
830  (EpsilonOnOutput(call_label_type_))
831  ? 0
832  : ((call_output_label_ == kNoLabel) ? arc.olabel
833  : call_output_label_);
834  *arcp = Arc(ilabel, olabel, arc.weight, nt_nextstate);
835  } else {
836  return false;
837  }
838  } else {
839  const auto nextstate =
840  flags & kArcNextStateValue
841  ? state_table_->FindState(
842  StateTuple(tuple.prefix_id, tuple.fst_id, arc.nextstate))
843  : kNoStateId;
844  *arcp = Arc(arc.ilabel, arc.olabel, arc.weight, nextstate);
845  }
846  }
847  return true;
848  }
849 
850  // Returns the arc iterator flags supported by this FST.
852  uint32 flags = kArcValueFlags;
853  if (!always_cache_) flags |= kArcNoCache;
854  return flags;
855  }
856 
857  StateTable *GetStateTable() const { return state_table_.get(); }
858 
859  const Fst<Arc> *GetFst(Label fst_id) const {
860  return fst_array_[fst_id].get();
861  }
862 
863  Label GetFstId(Label nonterminal) const {
864  const auto it = nonterminal_hash_.find(nonterminal);
865  if (it == nonterminal_hash_.end()) {
866  FSTERROR() << "ReplaceFstImpl::GetFstId: Nonterminal not found: "
867  << nonterminal;
868  }
869  return it->second;
870  }
871 
872  // Returns true if label type on call arc results in epsilon input label.
873  bool EpsilonOnCallInput() { return EpsilonOnInput(call_label_type_); }
874 
875  private:
876  // The unique index into stack prefix table.
877  PrefixId GetPrefixId(const StackPrefix &prefix) {
878  return state_table_->FindPrefixId(prefix);
879  }
880 
881  // The prefix ID after a stack pop.
882  PrefixId PopPrefix(StackPrefix prefix) {
883  prefix.Pop();
884  return GetPrefixId(prefix);
885  }
886 
887  // The prefix ID after a stack push.
888  PrefixId PushPrefix(StackPrefix prefix, Label fst_id, StateId nextstate) {
889  prefix.Push(fst_id, nextstate);
890  return GetPrefixId(prefix);
891  }
892 
893  // Runtime options
894  ReplaceLabelType call_label_type_; // How to label call arc.
895  ReplaceLabelType return_label_type_; // How to label return arc.
896  int64 call_output_label_; // Specifies output label to put on call arc
897  int64 return_label_; // Specifies label to put on return arc.
898  bool always_cache_; // Disable optional caching of arc iterator?
899 
900  // State table.
901  std::unique_ptr<StateTable> state_table_;
902 
903  // Replace components.
904  std::set<Label> nonterminal_set_;
905  NonTerminalHash nonterminal_hash_;
906  std::vector<std::unique_ptr<const Fst<Arc>>> fst_array_;
907  Label root_;
908 };
909 
910 } // namespace internal
911 
912 //
913 // ReplaceFst supports dynamic replacement of arcs in one FST with another FST.
914 // This replacement is recursive. ReplaceFst can be used to support a variety of
915 // delayed constructions such as recursive
916 // transition networks, union, or closure. It is constructed with an array of
917 // FST(s). One FST represents the root (or topology) machine. The root FST
918 // refers to other FSTs by recursively replacing arcs labeled as non-terminals
919 // with the matching non-terminal FST. Currently the ReplaceFst uses the output
920 // symbols of the arcs to determine whether the arc is a non-terminal arc or
921 // not. A non-terminal can be any label that is not a non-zero terminal label in
922 // the output alphabet.
923 //
924 // Note that the constructor uses a vector of pairs. These correspond to the
925 // tuple of non-terminal Label and corresponding FST. For example to implement
926 // the closure operation we need 2 FSTs. The first root FST is a single
927 // self-loop arc on the start state.
928 //
929 // The ReplaceFst class supports an optionally caching arc iterator.
930 //
931 // The ReplaceFst needs to be built such that it is known to be ilabel- or
932 // olabel-sorted (see usage below).
933 //
934 // Observe that Matcher<Fst<A>> will use the optionally caching arc iterator
935 // when available (the FST is ilabel-sorted and matching on the input, or the
936 // FST is olabel -orted and matching on the output). In order to obtain the
937 // most efficient behaviour, it is recommended to set call_label_type to
938 // REPLACE_LABEL_INPUT or REPLACE_LABEL_BOTH and return_label_type to
939 // REPLACE_LABEL_OUTPUT or REPLACE_LABEL_NEITHER. This means that the call arc
940 // does not have epsilon on the input side and the return arc has epsilon on the
941 // input side) and matching on the input side.
942 //
943 // This class attaches interface to implementation and handles reference
944 // counting, delegating most methods to ImplToFst.
945 template <class A, class T /* = DefaultReplaceStateTable<A> */,
946  class CacheStore /* = DefaultCacheStore<A> */>
947 class ReplaceFst
948  : public ImplToFst<internal::ReplaceFstImpl<A, T, CacheStore>> {
949  public:
950  using Arc = A;
951  using Label = typename Arc::Label;
952  using StateId = typename Arc::StateId;
953  using Weight = typename Arc::Weight;
954 
955  using StateTable = T;
956  using Store = CacheStore;
957  using State = typename CacheStore::State;
960 
962 
963  friend class ArcIterator<ReplaceFst<Arc, StateTable, CacheStore>>;
964  friend class StateIterator<ReplaceFst<Arc, StateTable, CacheStore>>;
965  friend class ReplaceFstMatcher<Arc, StateTable, CacheStore>;
966 
967  ReplaceFst(const std::vector<std::pair<Label, const Fst<Arc> *>> &fst_array,
968  Label root)
969  : ImplToFst<Impl>(std::make_shared<Impl>(
970  fst_array, ReplaceFstOptions<Arc, StateTable, CacheStore>(root))) {}
971 
972  ReplaceFst(const std::vector<std::pair<Label, const Fst<Arc> *>> &fst_array,
974  : ImplToFst<Impl>(std::make_shared<Impl>(fst_array, opts)) {}
975 
976  // See Fst<>::Copy() for doc.
978  bool safe = false)
979  : ImplToFst<Impl>(fst, safe) {}
980 
981  // Get a copy of this ReplaceFst. See Fst<>::Copy() for further doc.
983  bool safe = false) const override {
984  return new ReplaceFst<Arc, StateTable, CacheStore>(*this, safe);
985  }
986 
987  inline void InitStateIterator(StateIteratorData<Arc> *data) const override;
988 
989  void InitArcIterator(StateId s, ArcIteratorData<Arc> *data) const override {
990  GetMutableImpl()->InitArcIterator(s, data);
991  }
992 
993  MatcherBase<Arc> *InitMatcher(MatchType match_type) const override {
994  if ((GetImpl()->ArcIteratorFlags() & kArcNoCache) &&
995  ((match_type == MATCH_INPUT && Properties(kILabelSorted, false)) ||
996  (match_type == MATCH_OUTPUT && Properties(kOLabelSorted, false)))) {
998  match_type);
999  } else {
1000  VLOG(2) << "Not using replace matcher";
1001  return nullptr;
1002  }
1003  }
1004 
1005  bool CyclicDependencies() const { return GetImpl()->CyclicDependencies(); }
1006 
1007  const StateTable &GetStateTable() const {
1008  return *GetImpl()->GetStateTable();
1009  }
1010 
1011  const Fst<Arc> &GetFst(Label nonterminal) const {
1012  return *GetImpl()->GetFst(GetImpl()->GetFstId(nonterminal));
1013  }
1014 
1015  private:
1018 
1019  ReplaceFst &operator=(const ReplaceFst &) = delete;
1020 };
1021 
1022 // Specialization for ReplaceFst.
1023 template <class Arc, class StateTable, class CacheStore>
1024 class StateIterator<ReplaceFst<Arc, StateTable, CacheStore>>
1025  : public CacheStateIterator<ReplaceFst<Arc, StateTable, CacheStore>> {
1026  public:
1028  : CacheStateIterator<ReplaceFst<Arc, StateTable, CacheStore>>(
1029  fst, fst.GetMutableImpl()) {}
1030 };
1031 
1032 // Specialization for ReplaceFst, implementing optional caching. It is be used
1033 // as follows:
1034 //
1035 // ReplaceFst<A> replace;
1036 // ArcIterator<ReplaceFst<A>> aiter(replace, s);
1037 // // Note: ArcIterator< Fst<A>> is always a caching arc iterator.
1038 // aiter.SetFlags(kArcNoCache, kArcNoCache);
1039 // // Uses the arc iterator, no arc will be cached, no state will be expanded.
1040 // // Arc flags can be used to decide which component of the arc need to be
1041 // computed.
1042 // aiter.SetFlags(kArcILabelValue, kArcValueFlags);
1043 // // Wants the ilabel for this arc.
1044 // aiter.Value(); // Does not compute the destination state.
1045 // aiter.Next();
1046 // aiter.SetFlags(kArcNextStateValue, kArcNextStateValue);
1047 // // Wants the ilabel and next state for this arc.
1048 // aiter.Value(); // Does compute the destination state and inserts it
1049 // // in the replace state table.
1050 // // No additional arcs have been cached at this point.
1051 template <class Arc, class StateTable, class CacheStore>
1052 class ArcIterator<ReplaceFst<Arc, StateTable, CacheStore>> {
1053  public:
1054  using StateId = typename Arc::StateId;
1055 
1056  using StateTuple = typename StateTable::StateTuple;
1057 
1059  : fst_(fst),
1060  s_(s),
1061  pos_(0),
1062  offset_(0),
1063  flags_(kArcValueFlags),
1064  arcs_(nullptr),
1065  data_flags_(0),
1066  final_flags_(0) {
1067  cache_data_.ref_count = nullptr;
1068  local_data_.ref_count = nullptr;
1069  // If FST does not support optional caching, forces caching.
1070  if (!(fst_.GetImpl()->ArcIteratorFlags() & kArcNoCache) &&
1071  !(fst_.GetImpl()->HasArcs(s_))) {
1072  fst_.GetMutableImpl()->Expand(s_);
1073  }
1074  // If state is already cached, use cached arcs array.
1075  if (fst_.GetImpl()->HasArcs(s_)) {
1076  (fst_.GetImpl())
1077  ->internal::template CacheBaseImpl<
1078  typename CacheStore::State,
1079  CacheStore>::InitArcIterator(s_, &cache_data_);
1080  num_arcs_ = cache_data_.narcs;
1081  arcs_ = cache_data_.arcs; // arcs_ is a pointer to the cached arcs.
1082  data_flags_ = kArcValueFlags; // All the arc member values are valid.
1083  } else { // Otherwise delay decision until Value() is called.
1084  tuple_ = fst_.GetImpl()->GetStateTable()->Tuple(s_);
1085  if (tuple_.fst_state == kNoStateId) {
1086  num_arcs_ = 0;
1087  } else {
1088  // The decision to cache or not to cache has been defered until Value()
1089  // or
1090  // SetFlags() is called. However, the arc iterator is set up now to be
1091  // ready for non-caching in order to keep the Value() method simple and
1092  // efficient.
1093  const auto *rfst = fst_.GetImpl()->GetFst(tuple_.fst_id);
1094  rfst->InitArcIterator(tuple_.fst_state, &local_data_);
1095  // arcs_ is a pointer to the arcs in the underlying machine.
1096  arcs_ = local_data_.arcs;
1097  // Computes the final arc (but not its destination state) if a final arc
1098  // is required.
1099  bool has_final_arc = fst_.GetMutableImpl()->ComputeFinalArc(
1100  tuple_, &final_arc_, kArcValueFlags & ~kArcNextStateValue);
1101  // Sets the arc value flags that hold for final_arc_.
1102  final_flags_ = kArcValueFlags & ~kArcNextStateValue;
1103  // Computes the number of arcs.
1104  num_arcs_ = local_data_.narcs;
1105  if (has_final_arc) ++num_arcs_;
1106  // Sets the offset between the underlying arc positions and the
1107  // positions
1108  // in the arc iterator.
1109  offset_ = num_arcs_ - local_data_.narcs;
1110  // Defers the decision to cache or not until Value() or SetFlags() is
1111  // called.
1112  data_flags_ = 0;
1113  }
1114  }
1115  }
1116 
1118  if (cache_data_.ref_count) --(*cache_data_.ref_count);
1119  if (local_data_.ref_count) --(*local_data_.ref_count);
1120  }
1121 
1122  void ExpandAndCache() const {
1123  // TODO(allauzen): revisit this.
1124  // fst_.GetImpl()->Expand(s_, tuple_, local_data_);
1125  // (fst_.GetImpl())->CacheImpl<A>*>::InitArcIterator(s_,
1126  // &cache_data_);
1127  //
1128  fst_.InitArcIterator(s_, &cache_data_); // Expand and cache state.
1129  arcs_ = cache_data_.arcs; // arcs_ is a pointer to the cached arcs.
1130  data_flags_ = kArcValueFlags; // All the arc member values are valid.
1131  offset_ = 0; // No offset.
1132  }
1133 
1134  void Init() {
1135  if (flags_ & kArcNoCache) { // If caching is disabled
1136  // arcs_ is a pointer to the arcs in the underlying machine.
1137  arcs_ = local_data_.arcs;
1138  // Sets the arcs value flags that hold for arcs_.
1139  data_flags_ = kArcWeightValue;
1140  if (!fst_.GetMutableImpl()->EpsilonOnCallInput()) {
1141  data_flags_ |= kArcILabelValue;
1142  }
1143  // Sets the offset between the underlying arc positions and the positions
1144  // in the arc iterator.
1145  offset_ = num_arcs_ - local_data_.narcs;
1146  } else {
1147  ExpandAndCache();
1148  }
1149  }
1150 
1151  bool Done() const { return pos_ >= num_arcs_; }
1152 
1153  const Arc &Value() const {
1154  // If data_flags_ is 0, non-caching was not requested.
1155  if (!data_flags_) {
1156  // TODO(allauzen): Revisit this.
1157  if (flags_ & kArcNoCache) {
1158  // Should never happen.
1159  FSTERROR() << "ReplaceFst: Inconsistent arc iterator flags";
1160  }
1161  ExpandAndCache();
1162  }
1163  if (pos_ - offset_ >= 0) { // The requested arc is not the final arc.
1164  const auto &arc = arcs_[pos_ - offset_];
1165  if ((data_flags_ & flags_) == (flags_ & kArcValueFlags)) {
1166  // If the value flags match the recquired value flags then returns the
1167  // arc.
1168  return arc;
1169  } else {
1170  // Otherwise, compute the corresponding arc on-the-fly.
1171  fst_.GetMutableImpl()->ComputeArc(tuple_, arc, &arc_,
1172  flags_ & kArcValueFlags);
1173  return arc_;
1174  }
1175  } else { // The requested arc is the final arc.
1176  if ((final_flags_ & flags_) != (flags_ & kArcValueFlags)) {
1177  // If the arc value flags that hold for the final arc do not match the
1178  // requested value flags, then
1179  // final_arc_ needs to be updated.
1180  fst_.GetMutableImpl()->ComputeFinalArc(tuple_, &final_arc_,
1181  flags_ & kArcValueFlags);
1182  final_flags_ = flags_ & kArcValueFlags;
1183  }
1184  return final_arc_;
1185  }
1186  }
1187 
1188  void Next() { ++pos_; }
1189 
1190  size_t Position() const { return pos_; }
1191 
1192  void Reset() { pos_ = 0; }
1193 
1194  void Seek(size_t pos) { pos_ = pos; }
1195 
1196  uint32 Flags() const { return flags_; }
1197 
1198  void SetFlags(uint32 flags, uint32 mask) {
1199  // Updates the flags taking into account what flags are supported
1200  // by the FST.
1201  flags_ &= ~mask;
1202  flags_ |= (flags & fst_.GetImpl()->ArcIteratorFlags());
1203  // If non-caching is not requested (and caching has not already been
1204  // performed), then flush data_flags_ to request caching during the next
1205  // call to Value().
1206  if (!(flags_ & kArcNoCache) && data_flags_ != kArcValueFlags) {
1207  if (!fst_.GetImpl()->HasArcs(s_)) data_flags_ = 0;
1208  }
1209  // If data_flags_ has been flushed but non-caching is requested before
1210  // calling Value(), then set up the iterator for non-caching.
1211  if ((flags & kArcNoCache) && (!data_flags_)) Init();
1212  }
1213 
1214  private:
1215  const ReplaceFst<Arc, StateTable, CacheStore> &fst_; // Reference to the FST.
1216  StateId s_; // State in the FST.
1217  mutable StateTuple tuple_; // Tuple corresponding to state_.
1218 
1219  ssize_t pos_; // Current position.
1220  mutable ssize_t offset_; // Offset between position in iterator and in arcs_.
1221  ssize_t num_arcs_; // Number of arcs at state_.
1222  uint32 flags_; // Behavorial flags for the arc iterator
1223  mutable Arc arc_; // Memory to temporarily store computed arcs.
1224 
1225  mutable ArcIteratorData<Arc> cache_data_; // Arc iterator data in cache.
1226  mutable ArcIteratorData<Arc> local_data_; // Arc iterator data in local FST.
1227 
1228  mutable const Arc *arcs_; // Array of arcs.
1229  mutable uint32 data_flags_; // Arc value flags valid for data in arcs_.
1230  mutable Arc final_arc_; // Final arc (when required).
1231  mutable uint32 final_flags_; // Arc value flags valid for final_arc_.
1232 
1233  ArcIterator(const ArcIterator &) = delete;
1234  ArcIterator &operator=(const ArcIterator &) = delete;
1235 };
1236 
1237 template <class Arc, class StateTable, class CacheStore>
1238 class ReplaceFstMatcher : public MatcherBase<Arc> {
1239  public:
1240  using Label = typename Arc::Label;
1241  using StateId = typename Arc::StateId;
1242  using Weight = typename Arc::Weight;
1243 
1246 
1247  using StateTuple = typename StateTable::StateTuple;
1248 
1250  MatchType match_type)
1251  : fst_(fst),
1252  impl_(fst_.GetMutableImpl()),
1253  s_(fst::kNoStateId),
1254  match_type_(match_type),
1255  current_loop_(false),
1256  final_arc_(false),
1257  loop_(kNoLabel, 0, Weight::One(), kNoStateId) {
1258  if (match_type_ == fst::MATCH_OUTPUT) {
1259  std::swap(loop_.ilabel, loop_.olabel);
1260  }
1261  InitMatchers();
1262  }
1263 
1266  bool safe = false)
1267  : fst_(matcher.fst_),
1268  impl_(fst_.GetMutableImpl()),
1269  s_(fst::kNoStateId),
1270  match_type_(matcher.match_type_),
1271  current_loop_(false),
1272  final_arc_(false),
1273  loop_(fst::kNoLabel, 0, Weight::One(), fst::kNoStateId) {
1274  if (match_type_ == fst::MATCH_OUTPUT) {
1275  std::swap(loop_.ilabel, loop_.olabel);
1276  }
1277  InitMatchers();
1278  }
1279 
1280  // Creates a local matcher for each component FST in the RTN. LocalMatcher is
1281  // a multi-epsilon wrapper matcher. MultiEpsilonMatcher is used to match each
1282  // non-terminal arc, since these non-terminal
1283  // turn into epsilons on recursion.
1284  void InitMatchers() {
1285  const auto &fst_array = impl_->fst_array_;
1286  matcher_.resize(fst_array.size());
1287  for (Label i = 0; i < fst_array.size(); ++i) {
1288  if (fst_array[i]) {
1289  matcher_[i].reset(
1290  new LocalMatcher(*fst_array[i], match_type_, kMultiEpsList));
1291  auto it = impl_->nonterminal_set_.begin();
1292  for (; it != impl_->nonterminal_set_.end(); ++it) {
1293  matcher_[i]->AddMultiEpsLabel(*it);
1294  }
1295  }
1296  }
1297  }
1298 
1300  bool safe = false) const override {
1301  return new ReplaceFstMatcher<Arc, StateTable, CacheStore>(*this, safe);
1302  }
1303 
1304  MatchType Type(bool test) const override {
1305  if (match_type_ == MATCH_NONE) return match_type_;
1306  const auto true_prop =
1307  match_type_ == MATCH_INPUT ? kILabelSorted : kOLabelSorted;
1308  const auto false_prop =
1309  match_type_ == MATCH_INPUT ? kNotILabelSorted : kNotOLabelSorted;
1310  const auto props = fst_.Properties(true_prop | false_prop, test);
1311  if (props & true_prop) {
1312  return match_type_;
1313  } else if (props & false_prop) {
1314  return MATCH_NONE;
1315  } else {
1316  return MATCH_UNKNOWN;
1317  }
1318  }
1319 
1320  const Fst<Arc> &GetFst() const override { return fst_; }
1321 
1322  uint64 Properties(uint64 props) const override { return props; }
1323 
1324  // Sets the state from which our matching happens.
1325  void SetState(StateId s) final {
1326  if (s_ == s) return;
1327  s_ = s;
1328  tuple_ = impl_->GetStateTable()->Tuple(s_);
1329  if (tuple_.fst_state == kNoStateId) {
1330  done_ = true;
1331  return;
1332  }
1333  // Gets current matcher, used for non-epsilon matching.
1334  current_matcher_ = matcher_[tuple_.fst_id].get();
1335  current_matcher_->SetState(tuple_.fst_state);
1336  loop_.nextstate = s_;
1337  final_arc_ = false;
1338  }
1339 
1340  // Searches for label from previous set state. If label == 0, first
1341  // hallucinate an epsilon loop; otherwise use the underlying matcher to
1342  // search for the label or epsilons. Note since the ReplaceFst recursion
1343  // on non-terminal arcs causes epsilon transitions to be created we use
1344  // MultiEpsilonMatcher to search for possible matches of non-terminals. If the
1345  // component FST
1346  // reaches a final state we also need to add the exiting final arc.
1347  bool Find(Label label) final {
1348  bool found = false;
1349  label_ = label;
1350  if (label_ == 0 || label_ == kNoLabel) {
1351  // Computes loop directly, avoiding Replace::ComputeArc.
1352  if (label_ == 0) {
1353  current_loop_ = true;
1354  found = true;
1355  }
1356  // Searches for matching multi-epsilons.
1357  final_arc_ = impl_->ComputeFinalArc(tuple_, nullptr);
1358  found = current_matcher_->Find(kNoLabel) || final_arc_ || found;
1359  } else {
1360  // Searches on a sub machine directly using sub machine matcher.
1361  found = current_matcher_->Find(label_);
1362  }
1363  return found;
1364  }
1365 
1366  bool Done() const final {
1367  return !current_loop_ && !final_arc_ && current_matcher_->Done();
1368  }
1369 
1370  const Arc &Value() const final {
1371  if (current_loop_) return loop_;
1372  if (final_arc_) {
1373  impl_->ComputeFinalArc(tuple_, &arc_);
1374  return arc_;
1375  }
1376  const auto &component_arc = current_matcher_->Value();
1377  impl_->ComputeArc(tuple_, component_arc, &arc_);
1378  return arc_;
1379  }
1380 
1381  void Next() final {
1382  if (current_loop_) {
1383  current_loop_ = false;
1384  return;
1385  }
1386  if (final_arc_) {
1387  final_arc_ = false;
1388  return;
1389  }
1390  current_matcher_->Next();
1391  }
1392 
1393  ssize_t Priority(StateId s) final { return fst_.NumArcs(s); }
1394 
1395  private:
1398  LocalMatcher *current_matcher_;
1399  std::vector<std::unique_ptr<LocalMatcher>> matcher_;
1400  StateId s_; // Current state.
1401  Label label_; // Current label.
1402  MatchType match_type_; // Supplied by caller.
1403  mutable bool done_;
1404  mutable bool current_loop_; // Current arc is the implicit loop.
1405  mutable bool final_arc_; // Current arc for exiting recursion.
1406  mutable StateTuple tuple_; // Tuple corresponding to state_.
1407  mutable Arc arc_;
1408  Arc loop_;
1409 
1410  ReplaceFstMatcher &operator=(const ReplaceFstMatcher &) = delete;
1411 };
1412 
1413 template <class Arc, class StateTable, class CacheStore>
1415  StateIteratorData<Arc> *data) const {
1416  data->base =
1418 }
1419 
1421 
1422 // Recursively replaces arcs in the root FSTs with other FSTs.
1423 // This version writes the result of replacement to an output MutableFst.
1424 //
1425 // Replace supports replacement of arcs in one Fst with another FST. This
1426 // replacement is recursive. Replace takes an array of FST(s). One FST
1427 // represents the root (or topology) machine. The root FST refers to other FSTs
1428 // by recursively replacing arcs labeled as non-terminals with the matching
1429 // non-terminal FST. Currently Replace uses the output symbols of the arcs to
1430 // determine whether the arc is a non-terminal arc or not. A non-terminal can be
1431 // any label that is not a non-zero terminal label in the output alphabet.
1432 //
1433 // Note that input argument is a vector of pairs. These correspond to the tuple
1434 // of non-terminal Label and corresponding FST.
1435 template <class Arc>
1436 void Replace(const std::vector<std::pair<typename Arc::Label, const Fst<Arc> *>>
1437  &ifst_array,
1438  MutableFst<Arc> *ofst,
1440  opts.gc = true;
1441  opts.gc_limit = 0; // Caches only the last state for fastest copy.
1442  *ofst = ReplaceFst<Arc>(ifst_array, opts);
1443 }
1444 
1445 template <class Arc>
1446 void Replace(const std::vector<std::pair<typename Arc::Label, const Fst<Arc> *>>
1447  &ifst_array,
1448  MutableFst<Arc> *ofst, const ReplaceUtilOptions &opts) {
1449  Replace(ifst_array, ofst, ReplaceFstOptions<Arc>(opts));
1450 }
1451 
1452 // For backwards compatibility.
1453 template <class Arc>
1454 void Replace(const std::vector<std::pair<typename Arc::Label, const Fst<Arc> *>>
1455  &ifst_array,
1456  MutableFst<Arc> *ofst, typename Arc::Label root,
1457  bool epsilon_on_replace) {
1458  Replace(ifst_array, ofst, ReplaceFstOptions<Arc>(root, epsilon_on_replace));
1459 }
1460 
1461 template <class Arc>
1462 void Replace(const std::vector<std::pair<typename Arc::Label, const Fst<Arc> *>>
1463  &ifst_array,
1464  MutableFst<Arc> *ofst, typename Arc::Label root) {
1465  Replace(ifst_array, ofst, ReplaceFstOptions<Arc>(root));
1466 }
1467 
1468 } // namespace fst
1469 
1470 #endif // FST_LIB_REPLACE_H_
ssize_t NumOutputEpsilons(const ExpandedFst< Arc > &fst, typename Arc::StateId s)
Definition: expanded-fst.h:98
ReplaceFstOptions(const CacheOptions &opts, Label root=kNoLabel)
Definition: replace.h:333
typename CacheStore::State State
Definition: replace.h:460
void SetState(StateId s) final
Definition: replace.h:1325
ArcIterator(const ReplaceFst< Arc, StateTable, CacheStore > &fst, StateId s)
Definition: replace.h:1058
const StateTuple & Tuple(StateId id) const
Definition: replace.h:249
constexpr int kNoLabel
Definition: fst.h:180
std::vector< PrefixTuple > prefix_
Definition: replace.h:158
MatcherBase< Arc > * InitMatcher(MatchType match_type) const override
Definition: replace.h:993
void Expand(StateId s, const StateTuple &tuple, const ArcIteratorData< Arc > &data)
Definition: replace.h:746
const StateTable & GetStateTable() const
Definition: replace.h:1007
const StackPrefix & GetStackPrefix(PrefixId id) const
Definition: replace.h:297
constexpr uint64 kNotOLabelSorted
Definition: properties.h:82
uint64_t uint64
Definition: types.h:32
void Next() final
Definition: replace.h:1381
const Fst< Arc > * GetFst(Label fst_id) const
Definition: replace.h:859
ReplaceStateTuple(PrefixId prefix_id=-1, StateId fst_id=kNoStateId, StateId fst_state=kNoStateId)
Definition: replace.h:67
typename StateTable::PrefixId PrefixId
Definition: replace.h:462
PrefixId FindPrefixId(const StackPrefix &prefix)
Definition: replace.h:293
ReplaceFstOptions(int64 root, bool epsilon_replace_arc)
Definition: replace.h:368
ReplaceFstOptions(const ReplaceUtilOptions &opts)
Definition: replace.h:361
PrefixId prefix_id
Definition: replace.h:71
size_t NumOutputEpsilons(StateId s)
Definition: replace.h:668
bool EpsilonOnOutput(ReplaceLabelType label_type)
Definition: replace.h:389
typename CacheStore::State State
Definition: replace.h:957
bool ComputeArc(const StateTuple &tuple, const Arc &arc, Arc *arcp, uint32 flags=kArcValueFlags)
Definition: replace.h:796
ReplaceLabelType
Definition: replace-util.h:27
Arc::Weight Final(const ExpandedFst< Arc > &fst, typename Arc::StateId s)
Definition: expanded-fst.h:81
const SymbolTable * OutputSymbols() const
Definition: fst.h:677
MatchType
Definition: fst.h:171
constexpr uint64 kILabelSorted
Definition: properties.h:75
ReplaceFst(const std::vector< std::pair< Label, const Fst< Arc > * >> &fst_array, const ReplaceFstOptions< Arc, StateTable, CacheStore > &opts)
Definition: replace.h:972
uint64 Properties(uint64 mask) const override
Definition: replace.h:707
void InitArcIterator(StateId s, ArcIteratorData< Arc > *data) const override
Definition: replace.h:989
bool ReplaceTransducer(ReplaceLabelType call_label_type, ReplaceLabelType return_label_type, Label call_output_label)
Definition: replace.h:396
void Push(StateId fst_id, StateId nextstate)
Definition: replace.h:147
VectorHashReplaceStateTable(const VectorHashReplaceStateTable< Arc, PrefixId > &table)
Definition: replace.h:233
MatchType Type(bool test) const override
Definition: replace.h:1304
typename Arc::Weight Weight
Definition: replace.h:1242
ReplaceFst< Arc, StateTable, CacheStore > * Copy(bool safe=false) const override
Definition: replace.h:982
typename ReplaceFst< Arc, StateTable, CacheStore >::Arc Arc
Definition: cache.h:1098
ssize_t NumArcs(const ExpandedFst< Arc > &fst, typename Arc::StateId s)
Definition: expanded-fst.h:87
constexpr uint64 kNotILabelSorted
Definition: properties.h:77
bool EpsilonOnInput(ReplaceLabelType label_type)
Definition: replace.h:383
void Replace(const std::vector< std::pair< typename Arc::Label, const Fst< Arc > * >> &ifst_array, MutableFst< Arc > *ofst, std::vector< std::pair< typename Arc::Label, typename Arc::Label >> *parens, const PdtReplaceOptions< Arc > &opts)
Definition: replace.h:785
bool CyclicDependencies() const
Definition: replace.h:1005
const uint32 kMultiEpsList
Definition: matcher.h:1134
VectorHashReplaceStateTable(const std::vector< std::pair< Label, const Fst< Arc > * >> &fst_list, Label root)
Definition: replace.h:212
ReplaceFstOptions(const CacheImplOptions< CacheStore > &opts, Label root=kNoLabel)
Definition: replace.h:329
bool Find(Label label) final
Definition: replace.h:1347
const PrefixTuple & Top() const
Definition: replace.h:153
const Fst< Arc > & GetFst(Label nonterminal) const
Definition: replace.h:1011
constexpr uint64 kFstProperties
Definition: properties.h:301
constexpr uint64 kCopyProperties
Definition: properties.h:138
constexpr int kNoStateId
Definition: fst.h:179
uint64 operator()(const ReplaceStateTuple< StateId, PrefixId > &tuple) const
Definition: replace.h:114
const Arc & Value() const
Definition: fst.h:500
DefaultReplaceStateTable(const DefaultReplaceStateTable< Arc, PrefixId > &table)
Definition: replace.h:290
void InitArcIterator(StateId s, ArcIteratorData< Arc > *data)
Definition: replace.h:720
std::vector< std::pair< typename Arc::Label, const Fst< Arc > * >> FstList
Definition: replace.h:380
int64_t int64
Definition: types.h:27
#define FSTERROR()
Definition: util.h:32
ReplaceFstImpl(const ReplaceFstImpl &impl)
Definition: replace.h:540
size_t operator()(const ReplaceStateTuple< S, P > &t) const
Definition: replace.h:123
StateIteratorBase< Arc > * base
Definition: fst.h:350
typename Arc::Weight Weight
Definition: replace.h:458
ssize_t NumInputEpsilons(const ExpandedFst< Arc > &fst, typename Arc::StateId s)
Definition: expanded-fst.h:92
void InitStateIterator(StateIteratorData< Arc > *data) const override
Definition: replace.h:1414
typename Arc::StateId StateId
Definition: replace.h:197
bool operator==(const PdtStateTuple< S, K > &x, const PdtStateTuple< S, K > &y)
Definition: pdt.h:132
const Fst< Arc > & GetFst() const override
Definition: replace.h:1320
Weight Final(StateId s)
Definition: replace.h:590
constexpr uint64 kOLabelSorted
Definition: properties.h:80
#define VLOG(level)
Definition: log.h:49
size_t NumArcs(StateId s)
Definition: replace.h:602
typename Arc::Label Label
Definition: replace.h:196
uint32 ArcIteratorFlags() const
Definition: replace.h:851
bool Done() const
Definition: fst.h:496
uint64 Properties(uint64 props) const override
Definition: replace.h:1322
PrefixId FindPrefixId(const StackPrefix &prefix)
Definition: replace.h:251
const StackPrefix & GetStackPrefix(PrefixId id) const
Definition: replace.h:255
ReplaceFst(const std::vector< std::pair< Label, const Fst< Arc > * >> &fst_array, Label root)
Definition: replace.h:967
ReplaceFstOptions(Label root, ReplaceLabelType call_label_type, ReplaceLabelType return_label_type, Label return_label)
Definition: replace.h:344
bool ComputeFinalArc(const StateTuple &tuple, Arc *arcp, uint32 flags=kArcValueFlags)
Definition: replace.h:765
uint64 operator()(const ReplaceStateTuple< StateId, PrefixId > &tuple) const
Definition: replace.h:101
typename Arc::Label Label
Definition: replace.h:311
ReplaceFstMatcher< Arc, StateTable, CacheStore > * Copy(bool safe=false) const override
Definition: replace.h:1299
void Expand(StateId s)
Definition: replace.h:729
ReplaceFst(const ReplaceFst< Arc, StateTable, CacheStore > &fst, bool safe=false)
Definition: replace.h:977
const Arc & Value() const final
Definition: replace.h:1370
uint32_t uint32
Definition: types.h:31
Label GetFstId(Label nonterminal) const
Definition: replace.h:863
typename internal::ReplaceFstImpl< Arc, StateTable, CacheStore >::Arc Arc
Definition: fst.h:188
size_t Depth() const
Definition: replace.h:155
const SymbolTable * InputSymbols() const
Definition: fst.h:675
Arc::StateId CountStates(const Fst< Arc > &fst)
Definition: expanded-fst.h:158
bool CyclicDependencies() const
Definition: replace-util.h:118
typename Arc::Label Label
Definition: replace.h:1240
size_t operator()(const ReplaceStackPrefix< Label, StateId > &prefix) const
Definition: replace.h:179
ReplaceFstMatcher(const ReplaceFstMatcher< Arc, StateTable, CacheStore > &matcher, bool safe=false)
Definition: replace.h:1264
size_t NumInputEpsilons(StateId s)
Definition: replace.h:632
ssize_t Priority(StateId s) final
Definition: replace.h:1393
ReplaceFstOptions(Label root, ReplaceLabelType call_label_type, ReplaceLabelType return_label_type, Label call_output_label, Label return_label)
Definition: replace.h:352
ReplaceFstOptions(Label root)
Definition: replace.h:342
constexpr uint64 kError
Definition: properties.h:33
bool CyclicDependencies() const
Definition: replace.h:565
typename StateTable::StateTuple StateTuple
Definition: replace.h:1247
ReplaceFstImpl(const FstList< Arc > &fst_list, const ReplaceFstOptions< Arc, StateTable, CacheStore > &opts)
Definition: replace.h:485
uint64 Properties() const override
Definition: replace.h:704
ReplaceFstMatcher(const ReplaceFst< Arc, StateTable, CacheStore > &fst, MatchType match_type)
Definition: replace.h:1249
typename Arc::StateId StateId
Definition: replace.h:273
bool CompatSymbols(const SymbolTable *syms1, const SymbolTable *syms2, bool warning=true)
void Expand(const Fst< Arc > &ifst, const std::vector< std::pair< typename Arc::Label, typename Arc::Label >> &parens, const std::vector< typename Arc::Label > &assignments, MutableFst< Arc > *ofst, const MPdtExpandOptions &opts)
Definition: expand.h:302
ReplaceFingerprint(const std::vector< uint64 > *size_array)
Definition: replace.h:98
uint64 ReplaceFstProperties(typename Arc::Label root_label, const FstList< Arc > &fst_list, ReplaceLabelType call_label_type, ReplaceLabelType return_label_type, typename Arc::Label call_output_label, bool *sorted_and_non_empty)
Definition: replace.h:408
ReplaceStackPrefix(const ReplaceStackPrefix &other)
Definition: replace.h:144
typename Arc::StateId StateId
Definition: replace.h:457
bool Done() const final
Definition: replace.h:1366
StateId FindState(const StateTuple &tuple)
Definition: replace.h:245
bool IsNonTerminal(Label label) const
Definition: replace.h:618
typename Arc::StateId StateId
Definition: replace.h:1241
DefaultReplaceStateTable(const std::vector< std::pair< Label, const Fst< Arc > * >> &, Label)
Definition: replace.h:287
StateIterator(const ReplaceFst< Arc, StateTable, CacheStore > &fst)
Definition: replace.h:1027
typename Arc::Label Label
Definition: replace.h:456
PrefixTuple(Label fst_id=kNoLabel, StateId nextstate=kNoStateId)
Definition: replace.h:135
bool operator()(const ReplaceStateTuple< StateId, PrefixId > &tuple) const
Definition: replace.h:89
StateTable * GetStateTable() const
Definition: replace.h:857
std::unordered_map< Label, Label > NonTerminalHash
Definition: replace.h:465
void Next()
Definition: fst.h:504
uint64 ReplaceProperties(const std::vector< uint64 > &inprops, ssize_t root, bool epsilon_on_call, bool epsilon_on_return, bool out_epsilon_on_call, bool out_epsilon_on_return, bool replace_transducer, bool no_empty_fst, bool all_ilabel_sorted, bool all_olabel_sorted, bool all_negative_or_dense)
Definition: properties.cc:233