irstlm/src/shiftlm.h

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/******************************************************************************
IrstLM: IRST Language Model Toolkit
Copyright (C) 2006 Marcello Federico, ITC-irst Trento, Italy

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 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
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301 USA

******************************************************************************/


// Non linear Shift based interpolated LMs

class shiftone: public mdiadaptlm{
protected:
  int prunethresh;
  double beta;   
public:
  shiftone(char* ngtfile,int depth=0,int prunefreq=0,TABLETYPE tt=SHIFTBETA_B);
  int train();
  int discount(ngram ng,int size,double& fstar,double& lambda,int cv=0);  
  ~shiftone(){}
};


class shiftbeta: public mdiadaptlm{
 protected:
  int prunethresh;
  double* beta;

 public:
  shiftbeta(char* ngtfile,int depth=0,int prunefreq=0,double beta=-1,TABLETYPE tt=SHIFTBETA_B);
  int train();
  int discount(ngram ng,int size,double& fstar,double& lambda,int cv=0);  
  ~shiftbeta(){delete [] beta;}

};


class symshiftbeta: public shiftbeta{
 public:
  symshiftbeta(char* ngtfile,int depth=0,int prunefreq=0,double beta=-1):
    shiftbeta(ngtfile,depth,prunefreq,beta){}
  int discount(ngram ng,int size,double& fstar,double& lambda,int cv=0);  
};


class mshiftbeta: public mdiadaptlm{
 protected:
  int prunethresh;
  double beta[3][MAX_NGRAM];
  ngramtable* tb[MAX_NGRAM];

  double oovsum;

 public:
  mshiftbeta(char* ngtfile,int depth=0,int prunefreq=0,TABLETYPE tt=MSHIFTBETA_B);
  int train();
  int discount(ngram ng,int size,double& fstar,double& lambda,int cv=0);  

  ~mshiftbeta(){}

  int mfreq(ngram& ng,int l){return (l<lmsize()?getfreq(ng.link,ng.pinfo,1):ng.freq);}

};

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