/usr/include/fst/compose.h is in libfst-dev 1.5.3+r3-2.
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// finite-state transducer library.
//
// Class to compute the composition of two FSTs.
#ifndef FST_LIB_COMPOSE_H_
#define FST_LIB_COMPOSE_H_
#include <algorithm>
#include <string>
#include <vector>
#include <fst/cache.h>
#include <fst/compose-filter.h>
#include <fst/fst-decl.h> // For optional argument declarations
#include <fst/lookahead-filter.h>
#include <fst/matcher.h>
#include <fst/state-table.h>
#include <fst/test-properties.h>
namespace fst {
// Delayed composition options templated on the arc type, the matcher,
// the composition filter, and the composition state table. By
// default, the matchers, filter, and state table are constructed by
// composition. If set below, the user can instead pass in these
// objects; in that case, ComposeFst takes their ownership. This
// version controls composition implemented between generic Fst<Arc>
// types and a shared matcher type M for Fst<Arc>. This should be
// adequate for most applications, giving a reasonable tradeoff
// between efficiency and code sharing (but see ComposeFstImplOptions).
template <class A, class M = Matcher<Fst<A>>,
class F = SequenceComposeFilter<M>,
class T = GenericComposeStateTable<A, typename F::FilterState>>
struct ComposeFstOptions : public CacheOptions {
M *matcher1; // FST1 matcher (see matcher.h)
M *matcher2; // FST2 matcher
F *filter; // Composition filter (see compose-filter.h)
T *state_table; // Composition state table (see compose-state-table.h)
explicit ComposeFstOptions(const CacheOptions &opts, M *mat1 = 0, M *mat2 = 0,
F *filt = 0, T *sttable = 0)
: CacheOptions(opts),
matcher1(mat1),
matcher2(mat2),
filter(filt),
state_table(sttable) {}
ComposeFstOptions() : matcher1(0), matcher2(0), filter(0), state_table(0) {}
};
// Delayed composition options templated on the two matcher types, the
// composition filter, the composition state table and the cache
// store. By default, the matchers, filter, state table and cache
// store are constructed by composition. If set below, the user can
// instead pass in these objects; in that case, ComposeFst takes their
// ownership. This version controls composition implemented using
// arbitrary matchers (of the same Arc type but otherwise arbitrary
// Fst type). The user must ensure the matchers are compatible. These
// options permit the most efficient use, but shares the least
// code. This is for advanced use only in the most demanding or
// specialized applications that can benefit from it (o.w. prefer
// ComposeFstOptions).
template <class M1, class M2, class F = SequenceComposeFilter<M1, M2>,
class T = GenericComposeStateTable<typename M1::Arc,
typename F::FilterState>,
class C = DefaultCacheStore<typename M1::Arc>>
struct ComposeFstImplOptions : public CacheImplOptions<C> {
M1 *matcher1; // FST1 matcher (see matcher.h)
M2 *matcher2; // FST2 matcher
F *filter; // Composition filter (see compose-filter.h)
T *state_table; // Composition state table (see compose-state-table.h)
bool own_state_table; // ComposeFstImpl takes ownership of 'state_table'?
explicit ComposeFstImplOptions(const CacheOptions &opts,
M1 *mat1 = 0, M2 *mat2 = 0,
F *filt = 0, T *sttable = 0)
: CacheImplOptions<C>(opts),
matcher1(mat1),
matcher2(mat2),
filter(filt),
state_table(sttable),
own_state_table(true) {}
explicit ComposeFstImplOptions(const CacheImplOptions<C> &opts,
M1 *mat1 = 0, M2 *mat2 = 0,
F *filt = 0, T *sttable = 0)
: CacheImplOptions<C>(opts),
matcher1(mat1),
matcher2(mat2),
filter(filt),
state_table(sttable),
own_state_table(true) {}
ComposeFstImplOptions()
: matcher1(0), matcher2(0), filter(0), state_table(0),
own_state_table(true) {}
};
// Implementation of delayed composition. This base class is
// common to the variants with different matchers, composition filters
// and state tables.
template <class A, class C = DefaultCacheStore<A>>
class ComposeFstImplBase : public CacheBaseImpl<typename C::State, C> {
public:
typedef typename A::Label Label;
typedef typename A::Weight Weight;
typedef typename A::StateId StateId;
typedef typename C::State State;
typedef CacheBaseImpl<State, C> CImpl;
using FstImpl<A>::SetType;
using FstImpl<A>::SetProperties;
using FstImpl<A>::Properties;
using FstImpl<A>::SetInputSymbols;
using FstImpl<A>::SetOutputSymbols;
using CImpl::HasStart;
using CImpl::HasFinal;
using CImpl::HasArcs;
using CImpl::SetFinal;
using CImpl::SetStart;
ComposeFstImplBase(const Fst<A> &fst1, const Fst<A> &fst2,
const CacheImplOptions<C> &opts)
: CImpl(opts) {
InitBase(fst1, fst2);
}
ComposeFstImplBase(const Fst<A> &fst1, const Fst<A> &fst2,
const CacheOptions &opts)
: CImpl(opts) {
InitBase(fst1, fst2);
}
ComposeFstImplBase(const ComposeFstImplBase<A, C> &impl) : CImpl(impl, true) {
SetType(impl.Type());
SetProperties(impl.Properties(), kCopyProperties);
SetInputSymbols(impl.InputSymbols());
SetOutputSymbols(impl.OutputSymbols());
}
virtual ComposeFstImplBase<A, C> *Copy() const = 0;
~ComposeFstImplBase() override {}
StateId Start() {
if (!HasStart()) {
StateId start = ComputeStart();
if (start != kNoStateId) {
SetStart(start);
}
}
return CImpl::Start();
}
Weight Final(StateId s) {
if (!HasFinal(s)) {
Weight final = ComputeFinal(s);
SetFinal(s, final);
}
return CImpl::Final(s);
}
virtual void Expand(StateId s) = 0;
size_t NumArcs(StateId s) {
if (!HasArcs(s)) Expand(s);
return CImpl::NumArcs(s);
}
size_t NumInputEpsilons(StateId s) {
if (!HasArcs(s)) Expand(s);
return CImpl::NumInputEpsilons(s);
}
size_t NumOutputEpsilons(StateId s) {
if (!HasArcs(s)) Expand(s);
return CImpl::NumOutputEpsilons(s);
}
void InitArcIterator(StateId s, ArcIteratorData<A> *data) {
if (!HasArcs(s)) Expand(s);
CImpl::InitArcIterator(s, data);
}
virtual MatcherBase<A> *InitMatcher(const ComposeFst<A, C> &fst,
MatchType match_type) const {
// Use the default matcher if no override is provided.
return 0;
}
protected:
virtual StateId ComputeStart() = 0;
virtual Weight ComputeFinal(StateId s) = 0;
void InitBase(const Fst<A> &fst1, const Fst<A> &fst2) {
SetType("compose");
if (!CompatSymbols(fst2.InputSymbols(), fst1.OutputSymbols())) {
FSTERROR() << "ComposeFst: Output symbol table of 1st argument "
<< "does not match input symbol table of 2nd argument";
SetProperties(kError, kError);
}
SetInputSymbols(fst1.InputSymbols());
SetOutputSymbols(fst2.OutputSymbols());
}
};
// Forward declaration of ComposeFstMatcher
template <class C, class F, class T>
class ComposeFstMatcher;
// Implementaion of delayed composition templated on the matchers (see
// matcher.h), composition filter (see compose-filter.h) and
// the composition state table (see compose-state-table.h).
template <class C, class F, class T>
class ComposeFstImpl : public ComposeFstImplBase<typename C::Arc, C> {
typedef typename F::Matcher1 M1;
typedef typename F::Matcher2 M2;
friend class ComposeFstMatcher<C, F, T>;
typedef typename M1::FST FST1;
typedef typename M2::FST FST2;
typedef typename M1::Arc Arc;
typedef typename Arc::StateId StateId;
typedef typename Arc::Label Label;
typedef typename Arc::Weight Weight;
typedef typename F::FilterState FilterState;
typedef typename C::State State;
typedef CacheBaseImpl<State, C> CImpl;
typedef typename T::StateTuple StateTuple;
using FstImpl<Arc>::SetType;
using FstImpl<Arc>::SetProperties;
public:
template <class Mat1, class Mat2>
ComposeFstImpl(const FST1 &fst1, const FST2 &fst2,
const ComposeFstImplOptions<Mat1, Mat2, F, T, C> &opts);
ComposeFstImpl(const ComposeFstImpl<C, F, T> &impl)
: ComposeFstImplBase<Arc, C>(impl),
filter_(new F(*impl.filter_, true)),
matcher1_(filter_->GetMatcher1()),
matcher2_(filter_->GetMatcher2()),
fst1_(matcher1_->GetFst()),
fst2_(matcher2_->GetFst()),
state_table_(new T(*impl.state_table_)),
own_state_table_(true),
match_type_(impl.match_type_) {}
~ComposeFstImpl() override {
delete filter_;
if (own_state_table_) delete state_table_;
}
ComposeFstImpl<C, F, T> *Copy() const override {
return new ComposeFstImpl<C, F, T>(*this);
}
uint64 Properties() const override { return Properties(kFstProperties); }
// Set error if found; return FST impl properties.
uint64 Properties(uint64 mask) const override {
if ((mask & kError) &&
(fst1_.Properties(kError, false) || fst2_.Properties(kError, false) ||
(matcher1_->Properties(0) & kError) ||
(matcher2_->Properties(0) & kError) |
(filter_->Properties(0) & kError) ||
state_table_->Error())) {
SetProperties(kError, kError);
}
return FstImpl<Arc>::Properties(mask);
}
// Arranges it so that the first arg to OrderedExpand is the Fst
// that will be matched on.
void Expand(StateId s) override {
const StateTuple &tuple = state_table_->Tuple(s);
const StateId s1 = tuple.StateId1();
const StateId s2 = tuple.StateId2();
filter_->SetState(s1, s2, tuple.GetFilterState());
if (MatchInput(s1, s2)) {
OrderedExpand(s, fst2_, s2, fst1_, s1, matcher2_, true);
} else {
OrderedExpand(s, fst1_, s1, fst2_, s2, matcher1_, false);
}
}
const FST1 &GetFst1() const { return fst1_; }
const FST2 &GetFst2() const { return fst2_; }
const M1 *GetMatcher1() const { return matcher1_; }
M1 *GetMatcher1() { return matcher1_; }
const M2 *GetMatcher2() const { return matcher2_; }
M2 *GetMatcher2() { return matcher2_; }
const F *GetFilter() const { return filter_; }
F *GetFilter() { return filter_; }
const T *GetStateTable() const { return state_table_; }
T *GetStateTable() { return state_table_; }
MatcherBase<Arc> *InitMatcher(const ComposeFst<Arc, C> &fst,
MatchType match_type) const override {
uint64 test_props = match_type == MATCH_INPUT
? kFstProperties & ~kILabelInvariantProperties
: kFstProperties & ~kOLabelInvariantProperties;
// If both matchers support 'match_type' and we have
// a guarantee that a call to 'filter_->FilterArc(arc1, arc2)' will
// not modify the ilabel of arc1 when MATCH_INPUT or the olabel
// or arc2 when MATCH_OUTPUT, then ComposeFstMatcher can be used.
if ((matcher1_->Type(false) == match_type) &&
(matcher2_->Type(false) == match_type) &&
(filter_->Properties(test_props) == test_props)) {
return new ComposeFstMatcher<C, F, T>(fst, this, match_type);
}
return 0;
}
private:
// This does that actual matching of labels in the composition. The
// arguments are ordered so matching is called on state 'sa' of
// 'fsta' for each arc leaving state 'sb' of 'fstb'. The 'match_input' arg
// determines whether the input or output label of arcs at 'sb' is
// the one to match on.
template <class FST, class Matcher>
void OrderedExpand(StateId s, const Fst<Arc> &, StateId sa, const FST &fstb,
StateId sb, Matcher *matchera, bool match_input) {
matchera->SetState(sa);
// First process non-consuming symbols (e.g., epsilons) on FSTA.
Arc loop(match_input ? 0 : kNoLabel, match_input ? kNoLabel : 0,
Weight::One(), sb);
MatchArc(s, matchera, loop, match_input);
// Then process matches on FSTB.
for (ArcIterator<FST> iterb(fstb, sb); !iterb.Done(); iterb.Next())
MatchArc(s, matchera, iterb.Value(), match_input);
CImpl::SetArcs(s);
}
// Matches a single transition from 'fstb' against 'fata' at 's'.
template <class Matcher>
void MatchArc(StateId s, Matcher *matchera, const Arc &arc,
bool match_input) {
if (matchera->Find(match_input ? arc.olabel : arc.ilabel)) {
for (; !matchera->Done(); matchera->Next()) {
Arc arca = matchera->Value();
Arc arcb = arc;
if (match_input) {
const FilterState &f = filter_->FilterArc(&arcb, &arca);
if (f != FilterState::NoState()) AddArc(s, arcb, arca, f);
} else {
const FilterState &f = filter_->FilterArc(&arca, &arcb);
if (f != FilterState::NoState()) AddArc(s, arca, arcb, f);
}
}
}
}
// Add a matching transition at 's'.
void AddArc(StateId s, const Arc &arc1, const Arc &arc2,
const FilterState &f) {
StateTuple tuple(arc1.nextstate, arc2.nextstate, f);
Arc oarc(arc1.ilabel, arc2.olabel, Times(arc1.weight, arc2.weight),
state_table_->FindState(tuple));
CImpl::PushArc(s, oarc);
}
StateId ComputeStart() override {
StateId s1 = fst1_.Start();
if (s1 == kNoStateId) return kNoStateId;
StateId s2 = fst2_.Start();
if (s2 == kNoStateId) return kNoStateId;
const FilterState &f = filter_->Start();
StateTuple tuple(s1, s2, f);
return state_table_->FindState(tuple);
}
Weight ComputeFinal(StateId s) override {
const StateTuple &tuple = state_table_->Tuple(s);
const StateId s1 = tuple.StateId1();
Weight final1 = matcher1_->Final(s1);
if (final1 == Weight::Zero()) return final1;
const StateId s2 = tuple.StateId2();
Weight final2 = matcher2_->Final(s2);
if (final2 == Weight::Zero()) return final2;
filter_->SetState(s1, s2, tuple.GetFilterState());
filter_->FilterFinal(&final1, &final2);
return Times(final1, final2);
}
// Determines which side to match on per composition state.
bool MatchInput(StateId s1, StateId s2) {
switch (match_type_) {
case MATCH_INPUT:
return true;
case MATCH_OUTPUT:
return false;
default: // MATCH_BOTH
ssize_t priority1 = matcher1_->Priority(s1);
ssize_t priority2 = matcher2_->Priority(s2);
if (priority1 == kRequirePriority && priority2 == kRequirePriority) {
FSTERROR() << "ComposeFst: Both sides can't require match";
SetProperties(kError, kError);
return true;
}
if (priority1 == kRequirePriority) return false;
if (priority2 == kRequirePriority) {
return true;
}
return priority1 <= priority2;
}
}
// Identifies and verifies the capabilities of the matcher to be used for
// composition.
void SetMatchType();
F *filter_;
M1 *matcher1_;
M2 *matcher2_;
const FST1 &fst1_;
const FST2 &fst2_;
T *state_table_;
bool own_state_table_;
MatchType match_type_;
void operator=(const ComposeFstImpl<C, F, T> &); // disallow
};
template <class C, class F, class T>
template <class Mat1, class Mat2>
ComposeFstImpl<C, F, T>::ComposeFstImpl(
const FST1 &fst1, const FST2 &fst2,
const ComposeFstImplOptions<Mat1, Mat2, F, T, C> &opts)
: ComposeFstImplBase<Arc, C>(fst1, fst2, opts),
filter_(opts.filter ? opts.filter
: new F(fst1, fst2, opts.matcher1, opts.matcher2)),
matcher1_(filter_->GetMatcher1()),
matcher2_(filter_->GetMatcher2()),
fst1_(matcher1_->GetFst()),
fst2_(matcher2_->GetFst()),
state_table_(opts.state_table ? opts.state_table : new T(fst1_, fst2_)),
own_state_table_(opts.state_table ? opts.own_state_table : true) {
SetMatchType();
if (match_type_ == MATCH_NONE) SetProperties(kError, kError);
uint64 fprops1 = fst1.Properties(kFstProperties, false);
uint64 fprops2 = fst2.Properties(kFstProperties, false);
uint64 mprops1 = matcher1_->Properties(fprops1);
uint64 mprops2 = matcher2_->Properties(fprops2);
uint64 cprops = ComposeProperties(mprops1, mprops2);
SetProperties(filter_->Properties(cprops), kCopyProperties);
if (state_table_->Error()) SetProperties(kError, kError);
}
template <class C, class F, class T>
void ComposeFstImpl<C, F, T>::SetMatchType() {
// Ensures any required matching is possible and known.
if ((matcher1_->Flags() & kRequireMatch) &&
matcher1_->Type(true) != MATCH_OUTPUT) {
FSTERROR() << "ComposeFst: 1st argument cannot perform required matching.";
match_type_ = MATCH_NONE;
return;
}
if ((matcher2_->Flags() & kRequireMatch) &&
matcher2_->Type(true) != MATCH_INPUT) {
FSTERROR() << "ComposeFst: 2nd argument cannot perform required matching.";
match_type_ = MATCH_NONE;
return;
}
// Finds which sides to match on (favoring minimal testing of capabilities).
MatchType type1 = matcher1_->Type(false);
MatchType type2 = matcher2_->Type(false);
if (type1 == MATCH_OUTPUT && type2 == MATCH_INPUT) {
match_type_ = MATCH_BOTH;
} else if (type1 == MATCH_OUTPUT) {
match_type_ = MATCH_OUTPUT;
} else if (type2 == MATCH_INPUT) {
match_type_ = MATCH_INPUT;
} else if (matcher1_->Type(true) == MATCH_OUTPUT) {
match_type_ = MATCH_OUTPUT;
} else if (matcher2_->Type(true) == MATCH_INPUT) {
match_type_ = MATCH_INPUT;
} else {
FSTERROR() << "ComposeFst: 1st argument cannot match on output labels "
<< "and 2nd argument cannot match on input labels (sort?).";
match_type_ = MATCH_NONE;
}
}
// Computes the composition of two transducers. This version is a
// delayed Fst. If FST1 transduces string x to y with weight a and FST2
// transduces y to z with weight b, then their composition transduces
// string x to z with weight Times(x, z).
//
// The output labels of the first transducer or the input labels of
// the second transducer must be sorted (with the default matcher).
// The weights need to form a commutative semiring (valid for
// TropicalWeight and LogWeight).
//
// Complexity:
// Assuming the first FST is unsorted and the second is sorted:
// - Time: O(v1 v2 d1 (log d2 + m2)),
// - Space: O(v1 v2)
// where vi = # of states visited, di = maximum out-degree, and mi the
// maximum multiplicity of the states visited for the ith
// FST. Constant time and space to visit an input state or arc is
// assumed and exclusive of caching.
//
// Caveats:
// - ComposeFst does not trim its output (since it is a delayed operation).
// - The efficiency of composition can be strongly affected by several factors:
// - the choice of which transducer is sorted - prefer sorting the FST
// that has the greater average out-degree.
// - the amount of non-determinism
// - the presence and location of epsilon transitions - avoid epsilon
// transitions on the output side of the first transducer or
// the input side of the second transducer or prefer placing
// them later in a path since they delay matching and can
// introduce non-coaccessible states and transitions.
//
// This class attaches interface to implementation and handles
// reference counting, delegating most methods to ImplToFst.
// The type C specifies the cache store (default declared in fst-decl.h).
template <class A, class C /* = DefaultCacheStore<A> */>
class ComposeFst : public ImplToFst<ComposeFstImplBase<A, C>> {
public:
friend class ArcIterator<ComposeFst<A, C>>;
friend class StateIterator<ComposeFst<A, C>>;
typedef A Arc;
typedef C Store;
typedef typename A::Weight Weight;
typedef typename A::StateId StateId;
typedef typename C::State State;
typedef ComposeFstImplBase<A, C> Impl;
// Compose specifying only caching options.
ComposeFst(const Fst<A> &fst1, const Fst<A> &fst2,
const CacheOptions &opts = CacheOptions())
: ImplToFst<Impl>(CreateBase(fst1, fst2, opts)) {}
// Compose specifying one shared matcher type M. Requires input
// Fsts and matcher FST type (M::FST) be Fst<A>. Recommended for
// best code-sharing and matcher compatiblity.
template <class M, class F, class T>
ComposeFst(const Fst<A> &fst1, const Fst<A> &fst2,
const ComposeFstOptions<A, M, F, T> &opts)
: ImplToFst<Impl>(CreateBase1(fst1, fst2, opts)) {}
// Compose specifying two matcher types M1 and M2. Requires input
// Fsts (of the same Arc type but o.w. arbitrary) match the
// corresponding matcher FST types (M1::FST, M2::FST). Recommended
// only for advanced use in demanding or specialized applications
// due to potential code bloat and matcher incompatibilities.
template <class M1, class M2, class F, class T>
ComposeFst(const typename M1::FST &fst1, const typename M2::FST &fst2,
const ComposeFstImplOptions<M1, M2, F, T, C> &opts)
: ImplToFst<Impl>(CreateBase2(fst1, fst2, opts)) {}
// See Fst<>::Copy() for doc.
ComposeFst(const ComposeFst<A, C> &fst, bool safe = false)
: ImplToFst<Impl>(safe ? std::shared_ptr<Impl>(fst.GetImpl()->Copy())
: fst.GetSharedImpl()) {}
// Get a copy of this ComposeFst. See Fst<>::Copy() for further doc.
ComposeFst<A, C> *Copy(bool safe = false) const override {
return new ComposeFst<A, C>(*this, safe);
}
inline void InitStateIterator(StateIteratorData<A> *data) const override;
void InitArcIterator(StateId s, ArcIteratorData<A> *data) const override {
GetMutableImpl()->InitArcIterator(s, data);
}
MatcherBase<A> *InitMatcher(MatchType match_type) const override {
return GetImpl()->InitMatcher(*this, match_type);
}
protected:
using ImplToFst<Impl>::GetImpl;
using ImplToFst<Impl>::GetMutableImpl;
explicit ComposeFst(std::shared_ptr<Impl> impl) : ImplToFst<Impl>(impl) {}
// Create compose implementation specifying two matcher types.
template <class M1, class M2, class F, class T>
static std::shared_ptr<Impl> CreateBase2(
const typename M1::FST &fst1, const typename M2::FST &fst2,
const ComposeFstImplOptions<M1, M2, F, T, C> &opts) {
std::shared_ptr<Impl> impl =
std::make_shared<ComposeFstImpl<C, F, T>>(fst1, fst2, opts);
if (!(Weight::Properties() & kCommutative)) {
int64 props1 = fst1.Properties(kUnweighted, true);
int64 props2 = fst2.Properties(kUnweighted, true);
if (!(props1 & kUnweighted) && !(props2 & kUnweighted)) {
FSTERROR() << "ComposeFst: Weights must be a commutative semiring: "
<< Weight::Type();
impl->SetProperties(kError, kError);
}
}
return impl;
}
// Create compose implementation specifying one matcher type.
// Requires input Fsts and matcher FST type (M::FST) be Fst<A>
template <class M, class F, class T>
static std::shared_ptr<Impl> CreateBase1(
const Fst<A> &fst1, const Fst<A> &fst2,
const ComposeFstOptions<A, M, F, T> &opts) {
ComposeFstImplOptions<M, M, F, T, C> nopts(
opts, opts.matcher1, opts.matcher2, opts.filter, opts.state_table);
return CreateBase2(fst1, fst2, nopts);
}
// Create compose implementation specifying no matcher type.
static std::shared_ptr<Impl> CreateBase(const Fst<A> &fst1,
const Fst<A> &fst2,
const CacheOptions &opts) {
switch (LookAheadMatchType(fst1, fst2)) { // Check for lookahead matchers
default:
case MATCH_NONE: { // Default composition (no look-ahead)
ComposeFstOptions<Arc> nopts(opts);
return CreateBase1(fst1, fst2, nopts);
}
case MATCH_OUTPUT: { // Lookahead on fst1
typedef typename DefaultLookAhead<Arc, MATCH_OUTPUT>::FstMatcher M;
typedef typename DefaultLookAhead<Arc, MATCH_OUTPUT>::ComposeFilter F;
ComposeFstOptions<Arc, M, F> nopts(opts);
return CreateBase1(fst1, fst2, nopts);
}
case MATCH_INPUT: { // Lookahead on fst2
typedef typename DefaultLookAhead<Arc, MATCH_INPUT>::FstMatcher M;
typedef typename DefaultLookAhead<Arc, MATCH_INPUT>::ComposeFilter F;
ComposeFstOptions<Arc, M, F> nopts(opts);
return CreateBase1(fst1, fst2, nopts);
}
}
}
private:
void operator=(const ComposeFst<A, C> &fst); // disallow
};
// Specialization for ComposeFst.
template <class A, class C>
class StateIterator<ComposeFst<A, C>>
: public CacheStateIterator<ComposeFst<A, C>> {
public:
explicit StateIterator(const ComposeFst<A, C> &fst)
: CacheStateIterator<ComposeFst<A, C>>(fst, fst.GetMutableImpl()) {}
};
// Specialization for ComposeFst.
template <class A, class C>
class ArcIterator<ComposeFst<A, C>>
: public CacheArcIterator<ComposeFst<A, C>> {
public:
typedef typename A::StateId StateId;
ArcIterator(const ComposeFst<A, C> &fst, StateId s)
: CacheArcIterator<ComposeFst<A, C>>(fst.GetMutableImpl(), s) {
if (!fst.GetImpl()->HasArcs(s)) fst.GetMutableImpl()->Expand(s);
}
private:
DISALLOW_COPY_AND_ASSIGN(ArcIterator);
};
template <class A, class C>
inline void ComposeFst<A, C>::InitStateIterator(
StateIteratorData<A> *data) const {
data->base = new StateIterator<ComposeFst<A, C>>(*this);
}
// Specialized matcher for ComposeFst.
// Supports MATCH_INPUT (resp. MATCH_OUTPUT) iff the underlying
// matchers for the two Fsts being composed support
// MATCH_INPUT (resp. MATCH_OUTPUT)
template <class C, class F, class T>
class ComposeFstMatcher : public MatcherBase<typename C::Arc> {
public:
typedef typename C::Arc Arc;
typedef typename Arc::Label Label;
typedef typename Arc::StateId StateId;
typedef typename F::FilterState FilterState;
typedef typename F::Matcher1 Matcher1;
typedef typename F::Matcher2 Matcher2;
typedef typename T::StateTuple StateTuple;
ComposeFstMatcher(const ComposeFst<Arc, C> &fst,
const ComposeFstImpl<C, F, T> *impl, MatchType match_type)
: fst_(fst),
impl_(impl),
s_(kNoStateId),
match_type_(match_type),
matcher1_(impl->matcher1_->Copy()),
matcher2_(impl->matcher2_->Copy()),
current_loop_(false),
loop_(kNoLabel, 0, Arc::Weight::One(), kNoStateId),
error_(false) {
if (match_type == MATCH_OUTPUT) std::swap(loop_.ilabel, loop_.olabel);
}
ComposeFstMatcher(const ComposeFstMatcher<C, F, T> &matcher,
bool safe = false)
: fst_(matcher.fst_),
impl_(matcher.impl_),
s_(fst::kNoStateId),
match_type_(matcher.match_type_),
matcher1_(matcher.matcher1_->Copy(safe)),
matcher2_(matcher.matcher2_->Copy(safe)),
current_loop_(false),
loop_(fst::kNoLabel, 0, Arc::Weight::One(), fst::kNoStateId),
error_(matcher.error_) {
if (safe == true) {
FSTERROR() << "ComposeFstMatcher: Safe copy not supported";
error_ = true;
}
if (match_type_ == MATCH_OUTPUT) std::swap(loop_.ilabel, loop_.olabel);
}
ComposeFstMatcher<C, F, T> *Copy(bool safe = false) const override {
return new ComposeFstMatcher<C, F, T>(*this, safe);
}
~ComposeFstMatcher() override {
delete matcher1_;
delete matcher2_;
}
MatchType Type(bool test) const override {
if ((matcher1_->Type(test) == MATCH_NONE) ||
(matcher2_->Type(test) == MATCH_NONE)) {
return MATCH_NONE;
}
if (((matcher1_->Type(test) == MATCH_UNKNOWN) &&
(matcher2_->Type(test) == MATCH_UNKNOWN)) ||
((matcher1_->Type(test) == MATCH_UNKNOWN) &&
(matcher2_->Type(test) == match_type_)) ||
((matcher1_->Type(test) == match_type_) &&
(matcher2_->Type(test) == MATCH_UNKNOWN))) {
return MATCH_UNKNOWN;
}
if ((matcher1_->Type(test) == match_type_) &&
(matcher2_->Type(test) == match_type_)) {
return match_type_;
}
return MATCH_NONE;
}
const Fst<Arc> &GetFst() const override { return fst_; }
uint64 Properties(uint64 inprops) const override {
uint64 outprops = inprops;
if (error_) outprops |= kError;
return outprops;
}
// Processes a match with the filter and creates resulting arc.
bool MatchArc(StateId s, Arc arc1, Arc arc2) {
const FilterState &f = impl_->filter_->FilterArc(&arc1, &arc2);
if (f == FilterState::NoState()) return false;
StateTuple tuple(arc1.nextstate, arc2.nextstate, f);
arc_.ilabel = arc1.ilabel;
arc_.olabel = arc2.olabel;
arc_.weight = Times(arc1.weight, arc2.weight);
arc_.nextstate = impl_->state_table_->FindState(tuple);
return true;
}
// Finds the first match allowed by the filter.
template <class MatcherA, class MatcherB>
bool FindLabel(Label label, MatcherA *matchera, MatcherB *matcherb) {
if (matchera->Find(label)) {
matcherb->Find(match_type_ == MATCH_INPUT ? matchera->Value().olabel
: matchera->Value().ilabel);
return FindNext(matchera, matcherb);
}
return false;
}
// Finds the next match allowed by the filter:
// Returns true if such a match is found.
template <class MatcherA, class MatcherB>
bool FindNext(MatcherA *matchera, MatcherB *matcherb) {
// State when entering this function:
// 'matchera' is pointed to a match (x,y) for label x, and a match for y was
// requested on 'matcherb'.
while (!matchera->Done() || !matcherb->Done()) {
if (matcherb->Done()) {
// If no more matches for y on 'matcherb'
// move forward on 'matchera' until a match (x,y') is found
// such that there is a match for y' on 'matcherb'.
matchera->Next();
while (!matchera->Done() &&
!matcherb->Find(match_type_ == MATCH_INPUT
? matchera->Value().olabel
: matchera->Value().ilabel)) {
matchera->Next();
}
}
while (!matcherb->Done()) {
// 'matchera' is pointing to a match (x,y') ('arca') and
// 'matcherb' is pointing to a match (y',z') ('arcb').
// If combining these two arcs is allowed by the filter
// (hence resulting in an arc (x,z')) return true.
// Position 'matcherb' on the next potential match for y' before
// returning.
const Arc &arca = matchera->Value();
const Arc &arcb = matcherb->Value();
// Position 'matcherb' on the next potential match for y'.
matcherb->Next();
// If combining these two arcs is allowed by the filter
// (hence resulting in an arc (x,z')) return true.
// returning. Otherwise consider next match for y' on 'matcherb'.
if (MatchArc(s_, match_type_ == MATCH_INPUT ? arca : arcb,
match_type_ == MATCH_INPUT ? arcb : arca)) {
return true;
}
}
}
// Both 'matchera' and 'matcherb' are done, no more match to analyse.
return false;
}
private:
void SetState_(StateId s) override {
if (s_ == s) return;
s_ = s;
StateTuple tuple = impl_->state_table_->Tuple(s);
matcher1_->SetState(tuple.StateId1());
matcher2_->SetState(tuple.StateId2());
loop_.nextstate = s_;
}
bool Find_(Label label) override {
bool found = false;
current_loop_ = false;
if (label == 0) {
current_loop_ = true;
found = true;
}
if (match_type_ == MATCH_INPUT)
found = found || FindLabel(label, matcher1_, matcher2_);
else // match_type_ == MATCH_OUTPUT
found = found || FindLabel(label, matcher2_, matcher1_);
return found;
}
bool Done_() const override {
return !current_loop_ && matcher1_->Done() && matcher2_->Done();
}
const Arc &Value_() const override { return current_loop_ ? loop_ : arc_; }
void Next_() override {
if (current_loop_)
current_loop_ = false;
else if (match_type_ == MATCH_INPUT)
FindNext(matcher1_, matcher2_);
else // match_type_ == MATCH_OUTPUT
FindNext(matcher2_, matcher1_);
}
ssize_t Priority_(StateId s) override { return fst_.NumArcs(s); }
private:
const ComposeFst<Arc, C> &fst_;
const ComposeFstImpl<C, F, T> *impl_;
StateId s_;
MatchType match_type_;
Matcher1 *matcher1_;
Matcher2 *matcher2_;
bool current_loop_;
Arc loop_;
Arc arc_;
bool error_;
};
// Useful alias when using StdArc.
typedef ComposeFst<StdArc> StdComposeFst;
enum ComposeFilter {
AUTO_FILTER,
NULL_FILTER,
TRIVIAL_FILTER,
SEQUENCE_FILTER,
ALT_SEQUENCE_FILTER,
MATCH_FILTER
};
struct ComposeOptions {
bool connect; // Connect output
ComposeFilter filter_type; // Which pre-defined filter to use
ComposeOptions(bool c, ComposeFilter ft = AUTO_FILTER)
: connect(c), filter_type(ft) {}
ComposeOptions() : connect(true), filter_type(AUTO_FILTER) {}
};
// Computes the composition of two transducers. This version writes
// the composed FST into a MutableFst. If FST1 transduces string x to
// y with weight a and FST2 transduces y to z with weight b, then
// their composition transduces string x to z with weight
// Times(x, z).
//
// The output labels of the first transducer or the input labels of
// the second transducer must be sorted. The weights need to form a
// commutative semiring (valid for TropicalWeight and LogWeight).
//
// Complexity:
// Assuming the first FST is unsorted and the second is sorted:
// - Time: O(V1 V2 D1 (log D2 + M2)),
// - Space: O(V1 V2 D1 M2)
// where Vi = # of states, Di = maximum out-degree, and Mi is
// the maximum multiplicity for the ith FST.
//
// Caveats:
// - Compose trims its output.
// - The efficiency of composition can be strongly affected by several factors:
// - the choice of which transducer is sorted - prefer sorting the FST
// that has the greater average out-degree.
// - the amount of non-determinism
// - the presence and location of epsilon transitions - avoid epsilon
// transitions on the output side of the first transducer or
// the input side of the second transducer or prefer placing
// them later in a path since they delay matching and can
// introduce non-coaccessible states and transitions.
template <class Arc>
void Compose(const Fst<Arc> &ifst1, const Fst<Arc> &ifst2,
MutableFst<Arc> *ofst,
const ComposeOptions &opts = ComposeOptions()) {
typedef Matcher<Fst<Arc>> M;
if (opts.filter_type == AUTO_FILTER) {
CacheOptions nopts;
nopts.gc_limit = 0; // Cache only the last state for fastest copy.
*ofst = ComposeFst<Arc>(ifst1, ifst2, nopts);
} else if (opts.filter_type == NULL_FILTER) {
ComposeFstOptions<Arc, M, NullComposeFilter<M>> copts;
copts.gc_limit = 0; // Cache only the last state for fastest copy.
*ofst = ComposeFst<Arc>(ifst1, ifst2, copts);
} else if (opts.filter_type == SEQUENCE_FILTER) {
ComposeFstOptions<Arc, M, SequenceComposeFilter<M>> copts;
copts.gc_limit = 0; // Cache only the last state for fastest copy.
*ofst = ComposeFst<Arc>(ifst1, ifst2, copts);
} else if (opts.filter_type == ALT_SEQUENCE_FILTER) {
ComposeFstOptions<Arc, M, AltSequenceComposeFilter<M>> copts;
copts.gc_limit = 0; // Cache only the last state for fastest copy.
*ofst = ComposeFst<Arc>(ifst1, ifst2, copts);
} else if (opts.filter_type == MATCH_FILTER) {
ComposeFstOptions<Arc, M, MatchComposeFilter<M>> copts;
copts.gc_limit = 0; // Cache only the last state for fastest copy.
*ofst = ComposeFst<Arc>(ifst1, ifst2, copts);
} else if (opts.filter_type == TRIVIAL_FILTER) {
ComposeFstOptions<Arc, M, TrivialComposeFilter<M>> copts;
copts.gc_limit = 0; // Cache only the last state for fastest copy.
*ofst = ComposeFst<Arc>(ifst1, ifst2, copts);
}
if (opts.connect) Connect(ofst);
}
} // namespace fst
#endif // FST_LIB_COMPOSE_H_
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