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// union.h
// 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.
//
// Copyright 2005-2010 Google, Inc.
// Author: riley@google.com (Michael Riley)
//
// \file
// Functions and classes to compute the union of two FSTs.
#ifndef FST_LIB_UNION_H__
#define FST_LIB_UNION_H__
#include <vector>
using std::vector;
#include <algorithm>
#include <fst/mutable-fst.h>
#include <fst/rational.h>
namespace fst {
// Computes the union (sum) of two FSTs. This version writes the
// union to an output MurableFst. If A transduces string x to y with
// weight a and B transduces string w to v with weight b, then their
// union transduces x to y with weight a and w to v with weight b.
//
// Complexity:
// - Time: (V2 + E2)
// - Space: O(V2 + E2)
// where Vi = # of states and Ei = # of arcs of the ith FST.
template <class Arc>
void Union(MutableFst<Arc> *fst1, const Fst<Arc> &fst2) {
typedef typename Arc::StateId StateId;
typedef typename Arc::Label Label;
typedef typename Arc::Weight Weight;
// TODO(riley): restore when voice actions issues fixed
// Check that the symbol table are compatible
if (!CompatSymbols(fst1->InputSymbols(), fst2.InputSymbols()) ||
!CompatSymbols(fst1->OutputSymbols(), fst2.OutputSymbols())) {
LOG(ERROR) << "Union: input/output symbol tables of 1st argument "
<< "do not match input/output symbol tables of 2nd argument";
// fst1->SetProperties(kError, kError);
// return;
}
StateId numstates1 = fst1->NumStates();
bool initial_acyclic1 = fst1->Properties(kInitialAcyclic, true);
uint64 props1 = fst1->Properties(kFstProperties, false);
uint64 props2 = fst2.Properties(kFstProperties, false);
StateId start2 = fst2.Start();
if (start2 == kNoStateId) {
if (props2 & kError) fst1->SetProperties(kError, kError);
return;
}
if (fst2.Properties(kExpanded, false)) {
fst1->ReserveStates(
numstates1 + CountStates(fst2) + (initial_acyclic1 ? 0 : 1));
}
for (StateIterator< Fst<Arc> > siter(fst2);
!siter.Done();
siter.Next()) {
StateId s1 = fst1->AddState();
StateId s2 = siter.Value();
fst1->SetFinal(s1, fst2.Final(s2));
fst1->ReserveArcs(s1, fst2.NumArcs(s2));
for (ArcIterator< Fst<Arc> > aiter(fst2, s2);
!aiter.Done();
aiter.Next()) {
Arc arc = aiter.Value();
arc.nextstate += numstates1;
fst1->AddArc(s1, arc);
}
}
StateId start1 = fst1->Start();
if (start1 == kNoStateId) {
fst1->SetStart(start2);
fst1->SetProperties(props2, kCopyProperties);
return;
}
if (initial_acyclic1) {
fst1->AddArc(start1, Arc(0, 0, Weight::One(), start2 + numstates1));
} else {
StateId nstart1 = fst1->AddState();
fst1->SetStart(nstart1);
fst1->AddArc(nstart1, Arc(0, 0, Weight::One(), start1));
fst1->AddArc(nstart1, Arc(0, 0, Weight::One(), start2 + numstates1));
}
fst1->SetProperties(UnionProperties(props1, props2), kFstProperties);
}
// Computes the union of two FSTs; this version modifies its
// RationalFst argument.
template<class Arc>
void Union(RationalFst<Arc> *fst1, const Fst<Arc> &fst2) {
fst1->GetImpl()->AddUnion(fst2);
}
typedef RationalFstOptions UnionFstOptions;
// Computes the union (sum) of two FSTs. This version is a delayed
// Fst. If A transduces string x to y with weight a and B transduces
// string w to v with weight b, then their union transduces x to y
// with weight a and w to v with weight b.
//
// Complexity:
// - Time: O(v1 + e1 + v2 + e2)
// - Sapce: O(v1 + v2)
// where vi = # of states visited and ei = # of arcs visited of the
// ith FST. Constant time and space to visit an input state or arc
// is assumed and exclusive of caching.
template <class A>
class UnionFst : public RationalFst<A> {
public:
using ImplToFst< RationalFstImpl<A> >::GetImpl;
typedef A Arc;
typedef typename A::Weight Weight;
typedef typename A::StateId StateId;
UnionFst(const Fst<A> &fst1, const Fst<A> &fst2) {
GetImpl()->InitUnion(fst1, fst2);
}
UnionFst(const Fst<A> &fst1, const Fst<A> &fst2, const UnionFstOptions &opts)
: RationalFst<A>(opts) {
GetImpl()->InitUnion(fst1, fst2);
}
// See Fst<>::Copy() for doc.
UnionFst(const UnionFst<A> &fst, bool safe = false)
: RationalFst<A>(fst, safe) {}
// Get a copy of this UnionFst. See Fst<>::Copy() for further doc.
virtual UnionFst<A> *Copy(bool safe = false) const {
return new UnionFst<A>(*this, safe);
}
};
// Specialization for UnionFst.
template <class A>
class StateIterator< UnionFst<A> > : public StateIterator< RationalFst<A> > {
public:
explicit StateIterator(const UnionFst<A> &fst)
: StateIterator< RationalFst<A> >(fst) {}
};
// Specialization for UnionFst.
template <class A>
class ArcIterator< UnionFst<A> > : public ArcIterator< RationalFst<A> > {
public:
typedef typename A::StateId StateId;
ArcIterator(const UnionFst<A> &fst, StateId s)
: ArcIterator< RationalFst<A> >(fst, s) {}
};
// Useful alias when using StdArc.
typedef UnionFst<StdArc> StdUnionFst;
} // namespace fst
#endif // FST_LIB_UNION_H__
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