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58 lines
2.4 KiB
58 lines
2.4 KiB
3 years ago
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// fstext/remove-eps-local.h
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// Copyright 2009-2011 Microsoft Corporation
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// 2014 Johns Hopkins University (author: Daniel Povey)
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// See ../../COPYING for clarification regarding multiple authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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// KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
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// WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
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// MERCHANTABLITY OR NON-INFRINGEMENT.
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// See the Apache 2 License for the specific language governing permissions and
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// limitations under the License.
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#ifndef KALDI_FSTEXT_REMOVE_EPS_LOCAL_H_
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#define KALDI_FSTEXT_REMOVE_EPS_LOCAL_H_
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#include <fst/fst-decl.h>
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#include <fst/fstlib.h>
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namespace fst {
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/// RemoveEpsLocal remove some (but not necessarily all) epsilons in an FST,
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/// using an algorithm that is guaranteed to never increase the number of arcs
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/// in the FST (and will also never increase the number of states). The
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/// algorithm is not optimal but is reasonably clever. It does not just remove
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/// epsilon arcs;it also combines pairs of input-epsilon and output-epsilon arcs
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/// into one.
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/// The algorithm preserves equivalence and stochasticity in the given semiring.
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/// If you want to preserve stochasticity in a different semiring (e.g. log),
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/// then use RemoveEpsLocalSpecial, which only works for StdArc but which
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/// preserves stochasticity, where possible (*) in the LogArc sense. The reason
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/// that we can't just cast to a different semiring is that in that case we
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/// would no longer be able to guarantee equivalence in the original semiring
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/// (this arises from what happens when we combine identical arcs).
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/// (*) by "where possible".. there are situations where we wouldn't be able to
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/// preserve stochasticity in the LogArc sense while maintaining equivalence in
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/// the StdArc sense, so in these situations we maintain equivalence.
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template <class Arc>
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void RemoveEpsLocal(MutableFst<Arc> *fst);
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/// As RemoveEpsLocal but takes care to preserve stochasticity
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/// when cast to LogArc.
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inline void RemoveEpsLocalSpecial(MutableFst<StdArc> *fst);
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} // namespace fst
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#include "fstext/remove-eps-local-inl.h"
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#endif // KALDI_FSTEXT_REMOVE_EPS_LOCAL_H_
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