transition-model.h

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// hmm/transition-model.h

// Copyright 2009-2012  Microsoft Corporation
//                      Johns Hopkins University (author: Guoguo Chen)

// 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_HMM_TRANSITION_MODEL_H_
#define KALDI_HMM_TRANSITION_MODEL_H_

#include "base/kaldi-common.h"
#include "util/const-integer-set.h"
#include "fst/fst-decl.h" // forward declarations.
#include "hmm/hmm-topology.h"
#include "itf/options-itf.h"
#include "itf/context-dep-itf.h"
#include "matrix/kaldi-vector.h"

namespace kaldi {


// The class TransitionModel is a repository for the transition probabilities.
// It also handles certain integer mappings.
// The basic model is as follows.  Each phone has a HMM topology defined in
// hmm-topology.h.  Each HMM-state of each of these phones has a number of
// transitions (and final-probs) out of it.  Each HMM-state defined in the
// HmmTopology class has an associated "pdf_class".  This gets replaced with
// an actual pdf-id via the tree.  The transition model associates the
// transition probs with the (phone, HMM-state, pdf-id).  We associate with
// each such triple a transition-state.  Each
// transition-state has a number of associated probabilities to estimate;
// this depends on the number of transitions/final-probs in the topology for
// that (phone, HMM-state).  Each probability has an associated transition-index.
// We associate with each (transition-state, transition-index) a unique transition-id.
// Each individual probability estimated by the transition-model is associated with a
// transition-id.
//
// List of the various types of quantity referred to here and what they mean:
//           phone:  a phone index (1, 2, 3 ...)
//       HMM-state:  a number (0, 1, 2...) that indexes TopologyEntry (see hmm-topology.h)
//          pdf-id:  a number output by the Compute function of ContextDependency (it
//                   indexes pdf's, either forward or self-loop).  Zero-based.
// transition-state:  the states for which we estimate transition probabilities for transitions
//                    out of them.  In some topologies, will map one-to-one with pdf-ids.
//                    One-based, since it appears on FSTs.
// transition-index:  identifier of a transition (or final-prob) in the HMM.  Indexes the
//                    "transitions" vector in HmmTopology::HmmState.  [if it is out of range,
//                    equal to transitions.size(), it refers to the final-prob.]
//                    Zero-based.
//   transition-id:   identifier of a unique parameter of the TransitionModel.
//                    Associated with a (transition-state, transition-index) pair.
//                    One-based, since it appears on FSTs.
//
// List of the possible mappings TransitionModel can do:
//   (phone, HMM-state, forward-pdf-id, self-loop-pdf-id) -> transition-state
//                   (transition-state, transition-index) -> transition-id
//  Reverse mappings:
//                        transition-id -> transition-state
//                        transition-id -> transition-index
//                     transition-state -> phone
//                     transition-state -> HMM-state
//                     transition-state -> forward-pdf-id
//                     transition-state -> self-loop-pdf-id
//
// The main things the TransitionModel object can do are:
//    Get initialized (need ContextDependency and HmmTopology objects).
//    Read/write.
//    Update [given a vector of counts indexed by transition-id].
//    Do the various integer mappings mentioned above.
//    Get the probability (or log-probability) associated with a particular transition-id.


// Note: this was previously called TransitionUpdateConfig.
struct MleTransitionUpdateConfig {
  BaseFloat floor;
  BaseFloat mincount;
  bool share_for_pdfs; // If true, share all transition parameters that have the same pdf.
  MleTransitionUpdateConfig(BaseFloat floor = 0.01,
                            BaseFloat mincount = 5.0,
                            bool share_for_pdfs = false):
      floor(floor), mincount(mincount), share_for_pdfs(share_for_pdfs) {}

  void Register (OptionsItf *opts) {
    opts->Register("transition-floor", &floor,
                   "Floor for transition probabilities");
    opts->Register("transition-min-count", &mincount,
                   "Minimum count required to update transitions from a state");
    opts->Register("share-for-pdfs", &share_for_pdfs,
                   "If true, share all transition parameters where the states "
                   "have the same pdf.");
  }
};

struct MapTransitionUpdateConfig {
  BaseFloat tau;
  bool share_for_pdfs; // If true, share all transition parameters that have the same pdf.
  MapTransitionUpdateConfig(): tau(5.0), share_for_pdfs(false) { }

  void Register (OptionsItf *opts) {
    opts->Register("transition-tau", &tau, "Tau value for MAP estimation of transition "
                   "probabilities.");
    opts->Register("share-for-pdfs", &share_for_pdfs,
                   "If true, share all transition parameters where the states "
                   "have the same pdf.");
  }
};

class TransitionModel {

 public:
  TransitionModel(const ContextDependencyInterface &ctx_dep,
                  const HmmTopology &hmm_topo);


  TransitionModel(): num_pdfs_(0) { }

  void Read(std::istream &is, bool binary);  // note, no symbol table: topo object always read/written w/o symbols.
  void Write(std::ostream &os, bool binary) const;


  const HmmTopology &GetTopo() const { return topo_; }


  int32 TupleToTransitionState(int32 phone, int32 hmm_state, int32 pdf, int32 self_loop_pdf) const;
  int32 PairToTransitionId(int32 trans_state, int32 trans_index) const;
  int32 TransitionIdToTransitionState(int32 trans_id) const;
  int32 TransitionIdToTransitionIndex(int32 trans_id) const;
  int32 TransitionStateToPhone(int32 trans_state) const;
  int32 TransitionStateToHmmState(int32 trans_state) const;
  int32 TransitionStateToForwardPdfClass(int32 trans_state) const;
  int32 TransitionStateToSelfLoopPdfClass(int32 trans_state) const;
  int32 TransitionStateToForwardPdf(int32 trans_state) const;
  int32 TransitionStateToSelfLoopPdf(int32 trans_state) const;
  int32 SelfLoopOf(int32 trans_state) const;  // returns the self-loop transition-id, or zero if
  // this state doesn't have a self-loop.

  inline int32 TransitionIdToPdf(int32 trans_id) const;
  // TransitionIdToPdfFast is as TransitionIdToPdf but skips an assertion
  // (unless we're in paranoid mode).
  inline int32 TransitionIdToPdfFast(int32 trans_id) const;

  int32 TransitionIdToPhone(int32 trans_id) const;
  int32 TransitionIdToPdfClass(int32 trans_id) const;
  int32 TransitionIdToHmmState(int32 trans_id) const;


  bool IsFinal(int32 trans_id) const;  // returns true if this trans_id goes to the final state
  // (which is bound to be nonemitting).
  bool IsSelfLoop(int32 trans_id) const;  // return true if this trans_id corresponds to a self-loop.

  inline int32 NumTransitionIds() const { return id2state_.size()-1; }

  int32 NumTransitionIndices(int32 trans_state) const;

  int32 NumTransitionStates() const { return tuples_.size(); }

  // NumPdfs() actually returns the highest-numbered pdf we ever saw, plus one.
  // In normal cases this should equal the number of pdfs in the system, but if you
  // initialized this object with fewer than all the phones, and it happens that
  // an unseen phone has the highest-numbered pdf, this might be different.
  int32 NumPdfs() const { return num_pdfs_; }

  // This loops over the tuples and finds the highest phone index present. If
  // the FST symbol table for the phones is created in the expected way, i.e.:
  // starting from 1 (<eps> is 0) and numbered contiguously till the last phone,
  // this will be the total number of phones.
  int32 NumPhones() const;

  const std::vector<int32> &GetPhones() const { return topo_.GetPhones(); }

  // Transition-parameter-getting functions:
  BaseFloat GetTransitionProb(int32 trans_id) const;
  BaseFloat GetTransitionLogProb(int32 trans_id) const;

  // The following functions are more specialized functions for getting
  // transition probabilities, that are provided for convenience.

  BaseFloat GetTransitionLogProbIgnoringSelfLoops(int32 trans_id) const;

  BaseFloat GetNonSelfLoopLogProb(int32 trans_state) const;

  void MleUpdate(const Vector<double> &stats,
                 const MleTransitionUpdateConfig &cfg,
                 BaseFloat *objf_impr_out,
                 BaseFloat *count_out);

  void MapUpdate(const Vector<double> &stats,
                 const MapTransitionUpdateConfig &cfg,
                 BaseFloat *objf_impr_out,
                 BaseFloat *count_out);

  void Print(std::ostream &os,
             const std::vector<std::string> &phone_names,
             const Vector<double> *occs = NULL);


  void InitStats(Vector<double> *stats) const { stats->Resize(NumTransitionIds()+1); }

  void Accumulate(BaseFloat prob, int32 trans_id, Vector<double> *stats) const {
    KALDI_ASSERT(trans_id <= NumTransitionIds());
    (*stats)(trans_id) += prob;
    // This is trivial and doesn't require class members, but leaves us more open
    // to design changes than doing it manually.
  }

  bool Compatible(const TransitionModel &other) const;

 private:
  void MleUpdateShared(const Vector<double> &stats,
                       const MleTransitionUpdateConfig &cfg,
                       BaseFloat *objf_impr_out, BaseFloat *count_out);
  void MapUpdateShared(const Vector<double> &stats,
                       const MapTransitionUpdateConfig &cfg,
                       BaseFloat *objf_impr_out, BaseFloat *count_out);
  void ComputeTuples(const ContextDependencyInterface &ctx_dep);  // called from constructor.  initializes tuples_.
  void ComputeTuplesIsHmm(const ContextDependencyInterface &ctx_dep);
  void ComputeTuplesNotHmm(const ContextDependencyInterface &ctx_dep);
  void ComputeDerived();  // called from constructor and Read function: computes state2id_ and id2state_.
  void ComputeDerivedOfProbs();  // computes quantities derived from log-probs (currently just
  // non_self_loop_log_probs_; called whenever log-probs change.
  void InitializeProbs();  // called from constructor.
  void Check() const;
  bool IsHmm() const;

  struct Tuple {
    int32 phone;
    int32 hmm_state;
    int32 forward_pdf;
    int32 self_loop_pdf;
    Tuple() { }
    Tuple(int32 phone, int32 hmm_state, int32 forward_pdf, int32 self_loop_pdf):
      phone(phone), hmm_state(hmm_state), forward_pdf(forward_pdf), self_loop_pdf(self_loop_pdf) { }
    bool operator < (const Tuple &other) const {
      if (phone < other.phone) return true;
      else if (phone > other.phone) return false;
      else if (hmm_state < other.hmm_state) return true;
      else if (hmm_state > other.hmm_state) return false;
      else if (forward_pdf < other.forward_pdf) return true;
      else if (forward_pdf > other.forward_pdf) return false;
      else return (self_loop_pdf < other.self_loop_pdf);
    }
    bool operator == (const Tuple &other) const {
      return (phone == other.phone && hmm_state == other.hmm_state
              && forward_pdf == other.forward_pdf && self_loop_pdf == other.self_loop_pdf);
    }
  };

  HmmTopology topo_;

  std::vector<Tuple> tuples_;

  std::vector<int32> state2id_;

  std::vector<int32> id2state_;

  std::vector<int32> id2pdf_id_;

  Vector<BaseFloat> log_probs_;

  Vector<BaseFloat> non_self_loop_log_probs_;

  int32 num_pdfs_;

  KALDI_DISALLOW_COPY_AND_ASSIGN(TransitionModel);
};

inline int32 TransitionModel::TransitionIdToPdf(int32 trans_id) const {
  KALDI_ASSERT(
      static_cast<size_t>(trans_id) < id2pdf_id_.size() &&
      "Likely graph/model mismatch (graph built from wrong model?)");
  return id2pdf_id_[trans_id];
}

inline int32 TransitionModel::TransitionIdToPdfFast(int32 trans_id) const {
  // Note: it's a little dangerous to assert this only in paranoid mode.
  // However, this function is called in the inner loop of decoders and
  // the assertion likely takes a significant amount of time.  We make
  // sure that past the end of the id2pdf_id_ array there are big
  // numbers, which will make the calling code more likely to segfault
  // (rather than silently die) if this is called for out-of-range values.
  KALDI_PARANOID_ASSERT(
      static_cast<size_t>(trans_id) < id2pdf_id_.size() &&
      "Likely graph/model mismatch (graph built from wrong model?)");
  return id2pdf_id_[trans_id];
}

bool GetPdfsForPhones(const TransitionModel &trans_model,
                      const std::vector<int32> &phones,
                      std::vector<int32> *pdfs);

bool GetPhonesForPdfs(const TransitionModel &trans_model,
                      const std::vector<int32> &pdfs,
                      std::vector<int32> *phones);


} // end namespace kaldi


#endif