hmm_tagger.h

Go to the documentation of this file.

//
//    FreeLing - Open Source Language Analyzers
//
//    Copyright (C) 2014   TALP Research Center
//                         Universitat Politecnica de Catalunya
//
//    This library is free software; you can redistribute it and/or
//    modify it under the terms of the GNU Affero General Public
//    License as published by the Free Software Foundation; either
//    version 3 of the License, or (at your option) any later version.
//
//    This library is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//    Affero General Public License for more details.
//
//    You should have received a copy of the GNU Affero General Public
//    License along with this library; if not, write to the Free Software
//    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//
//    contact: Lluis Padro (padro@lsi.upc.es)
//             TALP Research Center
//             despatx C6.212 - Campus Nord UPC
//             08034 Barcelona.  SPAIN
//

#ifndef _TAGGER
#define _TAGGER

#include <map>
#include <list>
#include <set>

#include "freeling/windll.h"
#include "freeling/safe_map.h"
#include "freeling/morfo/language.h"
#include "freeling/morfo/tagger.h"
#include "freeling/morfo/tagset.h"

namespace freeling {


  typedef std::pair<std::wstring, std::wstring> bigram;

  class trellis {     
  private:

    class element {
    public:
      bigram state;
      int kbest;
      double prob;

      element(const bigram &, int, double);
      ~element();
      bool operator<(const element &) const;
      bool operator>(const element &) const;
      bool operator==(const element &) const;
    };

    typedef std::multiset<element,std::greater<element> > path_elements;
    std::vector<std::map <bigram, path_elements > > trl;

    unsigned int kbest;

  public:
    trellis(int, unsigned int kb=1);
    ~trellis();

    void insert(int, const bigram &, const bigram &, int kb, double);
    double delta(int, const bigram &, unsigned int k=0) const;
    std::pair<bigram, int> phi(int, const bigram &, unsigned int k=0) const;
    int nbest(int, const bigram &) const;

    static const float ZERO_logprob;
    static const bigram initState;
    static const bigram endState;
  };



  class emission_states: public std::set<bigram > {};


  class WINDLL hmm_tagger: public POS_tagger {
  private:
    // Tagset description
    const tagset *Tags;

    std::map <std::wstring, double> PTag;
    std::map <bigram, double> PBg;
    std::map <std::wstring, double> PTrg;
    std::map <bigram, double> PInitial;
    std::map <std::wstring, double> PWord;

    std::multimap <std::wstring, std::wstring> Forbidden;

    // probability for unobserved sentence initial trigrams
    double probInitial;
    // probability for unobserved words  
    double probUnobserved;

    safe_map<std::wstring,double> *pA_cache;
    //prob_cache *pB_cache;

    unsigned int kbest;

    double c[3];

    bool is_forbidden(const std::wstring &, sentence::const_iterator) const;
    double ProbA_log(const bigram &, const bigram &, sentence::const_iterator) const;
    double ProbB_log(const bigram &, const word &) const;
    double ProbPi_log(const bigram &) const;

    std::list<emission_states> FindStates(const sentence &) const;

  public:
    hmm_tagger(const std::wstring &, bool, unsigned int, unsigned int kb=1);
    ~hmm_tagger();

    void annotate(sentence &) const;
    double SequenceProb_log(const sentence &, int k=0) const;

  };

} // namespace

#endif