arcsum.h revision 4a68b3365c8c50aa93505e99ead2565ab73dcdb0
1// arcsum.h 2// 3// Licensed under the Apache License, Version 2.0 (the "License"); 4// you may not use this file except in compliance with the License. 5// You may obtain a copy of the License at 6// 7// http://www.apache.org/licenses/LICENSE-2.0 8// 9// Unless required by applicable law or agreed to in writing, software 10// distributed under the License is distributed on an "AS IS" BASIS, 11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12// See the License for the specific language governing permissions and 13// limitations under the License. 14// 15// 16// \file 17// Functions to sum arcs (sum weights) in an fst. 18 19#ifndef FST_LIB_ARCSUM_H__ 20#define FST_LIB_ARCSUM_H__ 21 22#include "fst/lib/mutable-fst.h" 23#include "fst/lib/weight.h" 24 25namespace fst { 26 27template <class A> 28class ArcSumCompare { 29 public: 30 bool operator()(const A& x, const A& y) { 31 if (x.ilabel < y.ilabel) return true; 32 if (x.ilabel > y.ilabel) return false; 33 if (x.olabel < y.olabel) return true; 34 if (x.olabel < y.olabel) return false; 35 if (x.nextstate < y.nextstate) return true; 36 if (x.nextstate > y.nextstate) return false; 37 return false; 38 } 39}; 40 41 42template <class A> 43class ArcSumEqual { 44 public: 45 bool operator()(const A& x, const A& y) { 46 return (x.ilabel == y.ilabel && 47 x.olabel == y.olabel && 48 x.nextstate == y.nextstate); 49 } 50}; 51 52 53// Combines identically labeled arcs, summing weights. For each state 54// we combine arcs with the same input and output label, summing their 55// weights using Weight:::Plus(). 56template <class A> 57void ArcSum(MutableFst<A>* fst) { 58 typedef typename A::StateId StateId; 59 60 vector<A> arcs; 61 for (StateIterator<Fst<A> > siter(*fst); !siter.Done(); siter.Next()) { 62 StateId s = siter.Value(); 63 if (fst->NumArcs(s) == 0) continue; 64 65 // Sums arcs into arcs array. 66 arcs.clear(); 67 arcs.reserve(fst->NumArcs(s)); 68 for (ArcIterator<Fst<A> > aiter(*fst, s); !aiter.Done(); 69 aiter.Next()) 70 arcs.push_back(aiter.Value()); 71 72 // At each state, first sorts the exiting arcs by input label, output label 73 // and destination state and then combines arcs identical in these 74 // attributes. 75 ArcSumCompare<A> comp; 76 sort(arcs.begin(), arcs.end(), comp); 77 78 // Deletes current arcs and copy in sumed arcs. 79 fst->DeleteArcs(s); 80 A current_arc = arcs[0]; 81 ArcSumEqual<A> equal; 82 for (size_t i = 1; i < arcs.size(); ++i) { 83 if (equal(current_arc, arcs[i])) { 84 current_arc.weight = Plus(current_arc.weight, arcs[i].weight); 85 } else { 86 fst->AddArc(s, current_arc); 87 current_arc = arcs[i]; 88 } 89 } 90 fst->AddArc(s, current_arc); 91 } 92} 93 94} 95 96#endif // FST_LIB_ARCSUM_H__ 97