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// itf/context-dep-itf.h
// Copyright 2009-2011 Microsoft Corporation; Go Vivace Inc.
// See ../../COPYING for clarification regarding multiple authors
//
// 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
//
// THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
// WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
// MERCHANTABLITY OR NON-INFRINGEMENT.
// See the Apache 2 License for the specific language governing permissions and
// limitations under the License.
#ifndef KALDI_ITF_CONTEXT_DEP_ITF_H_
#define KALDI_ITF_CONTEXT_DEP_ITF_H_
#include "base/kaldi-common.h"
namespace kaldi {
/// @ingroup tree_group
/// @{
/// context-dep-itf.h provides a link between
/// the tree-building code in ../tree/, and the FST code in ../fstext/
/// (particularly, ../fstext/context-dep.h). It is an abstract
/// interface that describes an object that can map from a
/// phone-in-context to a sequence of integer leaf-ids.
class ContextDependencyInterface {
public:
/// ContextWidth() returns the value N (e.g. 3 for triphone models) that says how many phones
/// are considered for computing context.
virtual int ContextWidth() const = 0;
/// Central position P of the phone context, in 0-based numbering, e.g. P = 1 for typical
/// triphone system. We have to see if we can do without this function.
virtual int CentralPosition() const = 0;
/// The "new" Compute interface. For typical topologies,
/// pdf_class would be 0, 1, 2.
/// Returns success or failure; outputs the pdf-id.
///
/// "Compute" is the main function of this interface, that takes a
/// sequence of N phones (and it must be N phones), possibly
/// including epsilons (symbol id zero) but only at positions other
/// than P [these represent unknown phone context due to end or
/// begin of sequence]. We do not insist that Compute must always
/// output (into stateseq) a nonempty sequence of states, but we
/// anticipate that stateseq will alyway be nonempty at output in
/// typical use cases. "Compute" returns false if expansion somehow
/// failed. Normally the calling code should raise an exception if
/// this happens. We can define a different interface later in
/// order to handle other kinds of information-- the underlying
/// data-structures from event-map.h are very flexible.
virtual bool Compute(const std::vector<int32> &phoneseq, int32 pdf_class,
int32 *pdf_id) const = 0;
/// NumPdfs() returns the number of acoustic pdfs (they are numbered 0.. NumPdfs()-1).
virtual int32 NumPdfs() const = 0;
virtual ~ContextDependencyInterface() {};
ContextDependencyInterface() {}
/// Returns pointer to new object which is copy of current one.
virtual ContextDependencyInterface *Copy() const = 0;
private:
KALDI_DISALLOW_COPY_AND_ASSIGN(ContextDependencyInterface);
};
/// @}
} // namespace Kaldi
#endif
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