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RmFinalEpsilon: Use constexpr if to check if the semiring is left-distributive; if it is, we don't need to check the weight value, just for epsilon arcs. #138

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RmFinalEpsilon: Use constexpr if to check if the semiring is left-distributive; if it is, we don't need to check the weight value, just for epsilon arcs. #138

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23 changes: 15 additions & 8 deletions openfst/lib/rmfinalepsilon.h
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Original file line number Diff line number Diff line change
Expand Up @@ -71,15 +71,22 @@ void RmFinalEpsilon(MutableFst<Arc>* fst) {
const auto& arc = aiter.Value();
// Next state is in the list of finals.
if (finals.find(arc.nextstate) != finals.end()) {
// Sums up all epsilon arcs if the semiring is left distributive.
// When left distributivity does not hold, at most one arc can be
// removed.
if (arc.ilabel == 0 && arc.olabel == 0 &&
(weight == Weight::Zero() ||
(Weight::Properties() & kLeftSemiring))) {
weight = Plus(Times(arc.weight, fst->Final(arc.nextstate)), weight);
// If the semiring is left-distributive we don't need to check if the
// weight is zero.
constexpr bool kIsLeftSemiring =
(Weight::Properties() & kLeftSemiring) != 0;
if constexpr (kIsLeftSemiring) {
if (arc.ilabel == 0 && arc.olabel == 0) {
weight = Plus(Times(arc.weight, fst->Final(arc.nextstate)), weight);
} else {
arcs.push_back(arc);
}
} else {
arcs.push_back(arc);
if (arc.ilabel == 0 && arc.olabel == 0 && weight == Weight::Zero()) {
weight = Plus(Times(arc.weight, fst->Final(arc.nextstate)), weight);
} else {
arcs.push_back(arc);
}
}
} else {
arcs.push_back(arc);
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