1 // push.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 // Author: allauzen (at) cs.nyu.edu (Cyril Allauzen) 16 // 17 // \file 18 // Class to reweight/push an FST. 19 20 #ifndef FST_LIB_PUSH_H__ 21 #define FST_LIB_PUSH_H__ 22 23 #include "fst/lib/factor-weight.h" 24 #include "fst/lib/fst.h" 25 #include "fst/lib/map.h" 26 #include "fst/lib/reweight.h" 27 #include "fst/lib/shortest-distance.h" 28 29 namespace fst { 30 31 // Pushes the weights in FST in the direction defined by TYPE. If 32 // pushing towards the initial state, the sum of the weight of the 33 // outgoing transitions and final weight at a non-initial state is 34 // equal to One() in the resulting machine. If pushing towards the 35 // final state, the same property holds on the reverse machine. 36 // 37 // Weight needs to be left distributive when pushing towards the 38 // initial state and right distributive when pushing towards the final 39 // states. 40 template <class Arc> 41 void Push(MutableFst<Arc> *fst, ReweightType type) { 42 vector<typename Arc::Weight> distance; 43 ShortestDistance(*fst, &distance, type == REWEIGHT_TO_INITIAL); 44 Reweight(fst, distance, type); 45 } 46 47 48 const uint32 kPushWeights = 0x0001; 49 const uint32 kPushLabels = 0x0002; 50 51 // OFST obtained from IFST by pushing weights and/or labels according 52 // to PTYPE in the direction defined by RTYPE. Weight needs to be 53 // left distributive when pushing weights towards the initial state 54 // and right distributive when pushing weights towards the final 55 // states. 56 template <class Arc, ReweightType rtype> 57 void Push(const Fst<Arc> &ifst, MutableFst<Arc> *ofst, uint32 ptype) { 58 59 if (ptype == kPushWeights) { 60 *ofst = ifst; 61 Push(ofst, rtype); 62 } else if (ptype & kPushLabels) { 63 const StringType stype = rtype == REWEIGHT_TO_INITIAL 64 ? STRING_LEFT 65 : STRING_RIGHT; 66 vector<typename GallicArc<Arc, stype>::Weight> gdistance; 67 VectorFst< GallicArc<Arc, stype> > gfst; 68 Map(ifst, &gfst, ToGallicMapper<Arc, stype>()); 69 if (ptype == (kPushWeights | kPushLabels)) { 70 ShortestDistance(gfst, &gdistance, rtype == REWEIGHT_TO_INITIAL); 71 } else { 72 MapFst<Arc, Arc, RmWeightMapper<Arc> > 73 uwfst(ifst, RmWeightMapper<Arc>()); 74 MapFst<Arc, GallicArc<Arc, stype>, ToGallicMapper<Arc, stype> > 75 guwfst(uwfst, ToGallicMapper<Arc, stype>()); 76 ShortestDistance(guwfst, &gdistance, rtype == REWEIGHT_TO_INITIAL); 77 } 78 Reweight(&gfst, gdistance, rtype); 79 FactorWeightFst< GallicArc<Arc, stype>, GallicFactor<typename Arc::Label, 80 typename Arc::Weight, stype> > fwfst(gfst); 81 Map(fwfst, ofst, FromGallicMapper<Arc, stype>()); 82 } else { 83 *ofst = ifst; 84 } 85 } 86 87 } // namespace fst 88 89 #endif /* FST_LIB_PUSH_H_ */ 90
