/usr/include/fst/rmfinalepsilon.h is in libfst-dev 1.5.3+r3-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 | // See www.openfst.org for extensive documentation on this weighted
// finite-state transducer library.
//
// Function to remove of final states that have epsilon-only input arcs.
#ifndef FST_LIB_RMFINALEPSILON_H_
#define FST_LIB_RMFINALEPSILON_H_
#include <unordered_set>
#include <vector>
#include <fst/connect.h>
#include <fst/mutable-fst.h>
namespace fst {
template <class A>
void RmFinalEpsilon(MutableFst<A>* fst) {
typedef typename A::StateId StateId;
typedef typename A::Weight Weight;
// Determine the coaccesibility of states.
std::vector<bool> access;
std::vector<bool> coaccess;
uint64 props = 0;
SccVisitor<A> scc_visitor(0, &access, &coaccess, &props);
DfsVisit(*fst, &scc_visitor);
// Find potential list of removable final states. These are final states
// that have no outgoing transitions or final states that have a
// non-coaccessible future. Complexity O(S)
std::unordered_set<StateId> finals;
for (StateIterator<Fst<A>> siter(*fst); !siter.Done(); siter.Next()) {
StateId s = siter.Value();
if (fst->Final(s) != Weight::Zero()) {
bool future_coaccess = false;
for (ArcIterator<Fst<A>> aiter(*fst, s); !aiter.Done(); aiter.Next()) {
const A& arc = aiter.Value();
if (coaccess[arc.nextstate]) {
future_coaccess = true;
break;
}
}
if (!future_coaccess) {
finals.insert(s);
}
}
}
// Move the final weight. Complexity O(E)
std::vector<A> arcs;
for (StateIterator<Fst<A>> siter(*fst); !siter.Done(); siter.Next()) {
StateId s = siter.Value();
Weight w(fst->Final(s));
arcs.clear();
for (ArcIterator<Fst<A>> aiter(*fst, s); !aiter.Done(); aiter.Next()) {
const A& arc = aiter.Value();
// is next state in the list of finals
if (finals.find(arc.nextstate) != finals.end()) {
// sum up all epsilon arcs
if (arc.ilabel == 0 && arc.olabel == 0) {
w = Plus(Times(fst->Final(arc.nextstate), arc.weight), w);
} else {
arcs.push_back(arc);
}
} else {
arcs.push_back(arc);
}
}
// If some arcs (epsilon arcs) were deleted, delete all
// arcs and add back only the non epsilon arcs
if (arcs.size() < fst->NumArcs(s)) {
fst->DeleteArcs(s);
fst->SetFinal(s, w);
for (size_t i = 0; i < arcs.size(); ++i) {
fst->AddArc(s, arcs[i]);
}
}
}
Connect(fst);
}
} // namespace fst
#endif // FST_LIB_RMFINALEPSILON_H_
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