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Diffstat (limited to 'kaldi_io/src/tools/openfst/include/fst/epsnormalize.h')
-rw-r--r-- | kaldi_io/src/tools/openfst/include/fst/epsnormalize.h | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/kaldi_io/src/tools/openfst/include/fst/epsnormalize.h b/kaldi_io/src/tools/openfst/include/fst/epsnormalize.h new file mode 100644 index 0000000..9d178b1 --- /dev/null +++ b/kaldi_io/src/tools/openfst/include/fst/epsnormalize.h @@ -0,0 +1,73 @@ +// epsnormalize.h + +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. +// +// Copyright 2005-2010 Google, Inc. +// Author: [email protected] (Cyril Allauzen) +// +// \file +// Function that implements epsilon normalization. + +#ifndef FST_LIB_EPSNORMALIZE_H__ +#define FST_LIB_EPSNORMALIZE_H__ + +#include <tr1/unordered_map> +using std::tr1::unordered_map; +using std::tr1::unordered_multimap; + + +#include <fst/factor-weight.h> +#include <fst/invert.h> +#include <fst/arc-map.h> +#include <fst/rmepsilon.h> + + +namespace fst { + +enum EpsNormalizeType {EPS_NORM_INPUT, EPS_NORM_OUTPUT}; + +// Returns an equivalent FST that is epsilon-normalized. An acceptor is +// epsilon-normalized if it is epsilon-removed. A transducer is input +// epsilon-normalized if additionally if on each path any epsilon input +// label follows all non-epsilon input labels. Output epsilon-normalized +// is defined similarly. +// +// The input FST needs to be functional. +// +// References: +// - Mehryar Mohri. "Generic epsilon-removal and input epsilon-normalization +// algorithms for weighted transducers", International Journal of Computer +// Science, 13(1): 129-143, 2002. +template <class Arc> +void EpsNormalize(const Fst<Arc> &ifst, MutableFst<Arc> *ofst, + EpsNormalizeType type = EPS_NORM_INPUT) { + VectorFst< GallicArc<Arc, STRING_RIGHT_RESTRICT> > gfst; + if (type == EPS_NORM_INPUT) + ArcMap(ifst, &gfst, ToGallicMapper<Arc, STRING_RIGHT_RESTRICT>()); + else // type == EPS_NORM_OUTPUT + ArcMap(InvertFst<Arc>(ifst), &gfst, + ToGallicMapper<Arc, STRING_RIGHT_RESTRICT>()); + RmEpsilon(&gfst); + FactorWeightFst< GallicArc<Arc, STRING_RIGHT_RESTRICT>, + GallicFactor<typename Arc::Label, + typename Arc::Weight, STRING_RIGHT_RESTRICT> > + fwfst(gfst); + ArcMap(fwfst, ofst, FromGallicMapper<Arc, STRING_RIGHT_RESTRICT>()); + ofst->SetOutputSymbols(ifst.OutputSymbols()); + if(type == EPS_NORM_OUTPUT) + Invert(ofst); +} + +} // namespace fst + +#endif // FST_LIB_EPSNORMALIZE_H__ |