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CosSimRetMethod.hpp

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/*==========================================================================
 * Copyright (c) 2002 University of Massachusetts.  All Rights Reserved.
 *
 * Use of the Lemur Toolkit for Language Modeling and Information Retrieval
 * is subject to the terms of the software license set forth in the LICENSE
 * file included with this software, and also available at
 * http://www.lemurproject.org/license.html
 *
 *==========================================================================
*/
/*
  Author: dmf 9/2002
 */

#ifndef _COSSIMRETMETHOD_HPP
#define _COSSIMRETMETHOD_HPP

#include "TextQueryRetMethod.hpp"

namespace CosSimParameter {
  struct FeedbackParam {
    int howManyTerms;
    double posCoeff;
  };    
  static int defaultHowManyTerms = 50;
  static double defaultPosCoeff = 0.5;
  static const string defaultL2File = "cos.L2";
};

class CosSimQueryRep : public ArrayQueryRep {
public:
  CosSimQueryRep(const TermQuery &qry, const Index &dbIndex, 
                 double *idfValue);
  CosSimQueryRep(DOCID_T docId, const Index &dbIndex, double *idfValue);
  virtual ~CosSimQueryRep() {}
protected:
  double *idf;
  const Index &ind;
};

class CosSimDocRep : public DocumentRep {
public:
  CosSimDocRep(DOCID_T docID, double *idfValue, double norm, int dl) : 
    DocumentRep(docID, dl), idf(idfValue), dNorm(norm) {
  }
  virtual ~CosSimDocRep() { }
  virtual double termWeight(TERMID_T termID, const DocInfo *info) const { 
    return (idf[termID]*info->termCount()); 
  }
  virtual double scoreConstant() const { return dNorm;}

private:
  double *idf;
  double dNorm; 
};

class CosSimScoreFunc : public ScoreFunction {
public:
  CosSimScoreFunc(const Index &dbIndex): ind(dbIndex) {}
  virtual double adjustedScore(double origScore, const TextQueryRep *qRep, 
                               const DocumentRep *dRep) const {
    return origScore/dRep->scoreConstant();
  }
protected:
  const Index &ind;
};

class CosSimRetMethod : public TextQueryRetMethod {
public:
  CosSimRetMethod(const Index &dbIndex, ScoreAccumulator &accumulator);
  CosSimRetMethod(const Index &dbIndex, const string &L2file,
                  ScoreAccumulator &accumulator);

  virtual ~CosSimRetMethod();

  virtual TextQueryRep *computeTextQueryRep(const TermQuery &qry) {
    return (new CosSimQueryRep(qry, ind, idfV));
  }

  virtual TextQueryRep *computeTextQueryRep(DOCID_T docid) {
    return (new CosSimQueryRep(docid, ind, idfV));
  }

  virtual DocumentRep *computeDocRep(DOCID_T docID) { 
    return (new CosSimDocRep(docID, idfV, docNorm(docID), 
                             ind.docLength(docID)));
  }
  virtual ScoreFunction *scoreFunc() {
    return (scFunc);
  }
  virtual void updateTextQuery(TextQueryRep &qryRep, 
                               const DocIDSet &relDocs);
  void setFeedbackParam(CosSimParameter::FeedbackParam &feedbackParam);
protected:
  
  double *idfV;
  ScoreFunction *scFunc;
  double * docNorms;
  int numDocs, numTerms;


  CosSimParameter::FeedbackParam fbParam;
  const string &L2FileName;

  double docNorm(DOCID_T docID);
  void loadDocNorms();
};

inline void CosSimRetMethod::setFeedbackParam(CosSimParameter::FeedbackParam 
                                              &feedbackParam) {
  fbParam = feedbackParam;
}
#endif /* _COSSIMRETMETHOD_HPP */

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