uk.ac.gla.dcs.renaissance.mg4j.scorers
Class HiemstraLMScorer

java.lang.Object
  it.unimi.dsi.fastutil.ints.AbstractIntIterator
      it.unimi.dsi.mg4j.search.score.AbstractScorer
          it.unimi.dsi.mg4j.search.score.AbstractIndexScorer
              it.unimi.dsi.mg4j.search.score.AbstractWeightedScorer
                  uk.ac.gla.dcs.renaissance.mg4j.scorers.HiemstraLMScorer

All Implemented Interfaces:

it.unimi.dsi.fastutil.ints.IntIterator, it.unimi.dsi.lang.FlyweightPrototype<it.unimi.dsi.mg4j.search.score.Scorer>, it.unimi.dsi.mg4j.search.score.DelegatingScorer, it.unimi.dsi.mg4j.search.score.Scorer, Iterator<Integer>

public class HiemstraLMScorer
extends it.unimi.dsi.mg4j.search.score.AbstractWeightedScorer
implements it.unimi.dsi.mg4j.search.score.DelegatingScorer

A scorer implementing the Hiemstra Language Modelling Approach. See Hiemstra, Djord. Using Language Models for Information Retrieval. PhD Thesis, 2001, chapters 4+5.

Currently it only supports the variant with document frequencies and document length normalisation.

Author:

Ingo Frommholz

Field Summary

Fields inherited from class it.unimi.dsi.mg4j.search.score.AbstractWeightedScorer

currWeight, index2Weight

Fields inherited from class it.unimi.dsi.mg4j.search.score.AbstractIndexScorer

currIndex, n

Fields inherited from class it.unimi.dsi.mg4j.search.score.AbstractScorer

documentIterator

Constructor Summary

HiemstraLMScorer()
Constructor.

HiemstraLMScorer(double lambda, boolean collFreqBackgroundModel, IndexConfiguration[] indexConfs)
Constructor.

HiemstraLMScorer(IndexConfiguration[] indexConfs)
Constructor.

Method Summary

it.unimi.dsi.mg4j.search.score.Scorer	copy()
double	score()
double	score(it.unimi.dsi.mg4j.index.Index index)
void	setIndexConfiguration(IndexConfiguration[] indexConfs) This may be our only chance to set the index configurations
boolean	usesIntervals()
void	wrap(it.unimi.dsi.mg4j.search.DocumentIterator d)

Methods inherited from class it.unimi.dsi.mg4j.search.score.AbstractWeightedScorer

getWeights, setWeights

Methods inherited from class it.unimi.dsi.mg4j.search.score.AbstractScorer

hasNext, nextDocument, nextInt, skip

Methods inherited from class it.unimi.dsi.fastutil.ints.AbstractIntIterator

next, remove

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface it.unimi.dsi.mg4j.search.score.Scorer

getWeights, nextDocument, nextInt, setWeights

Methods inherited from interface it.unimi.dsi.fastutil.ints.IntIterator

skip

Methods inherited from interface java.util.Iterator

hasNext, next, remove

Constructor Detail

HiemstraLMScorer

public HiemstraLMScorer(double lambda,
                        boolean collFreqBackgroundModel,
                        IndexConfiguration[] indexConfs)

Constructor. Besides setting the lambda parameter, there is also the choice if the background model P(t_i|M_c) should be based on the collection frequency (number of times a term appears in the collection) or document frequency (number of documents a term appears in). NOTE: Collection frequency is not supported yet!

Parameters:

lambda - the lambda value to use

collFreqBackgroundModel - true if the collection frequency should be used to calculate the background model P(t_i|M_d), false if the document frequency should be used for this model.

indexConfs - the index configurations. This must go along with the indexes we get from the term iterator!

HiemstraLMScorer

public HiemstraLMScorer(IndexConfiguration[] indexConfs)

Constructor. Uses default lambda value and the document frequency for the background model P(t_i|M_d)

Parameters:

indexConfs - the index configurations. This must go along with the indexes we get from the term iterator!

HiemstraLMScorer

public HiemstraLMScorer()

Constructor. Uses default lambda value and the document frequency for the background model P(t_i|M_d). You MUST add an indexConfiguration later with setIndexConfiguration(uk.ac.gla.dcs.renaissance.iqir.config.IndexConfiguration[])!

Method Detail

setIndexConfiguration

public void setIndexConfiguration(IndexConfiguration[] indexConfs)

This may be our only chance to set the index configurations

Parameters:

indexConfs - the index configurations. This must go along with the indexes we get from the term iterator!

score

public double score()
             throws IOException

Specified by:

score in interface it.unimi.dsi.mg4j.search.score.Scorer

Overrides:

score in class it.unimi.dsi.mg4j.search.score.AbstractWeightedScorer

Throws:

IOException

score

public double score(it.unimi.dsi.mg4j.index.Index index)
             throws IOException

Specified by:

score in interface it.unimi.dsi.mg4j.search.score.Scorer

Throws:

IOException

usesIntervals

public boolean usesIntervals()

Specified by:

usesIntervals in interface it.unimi.dsi.mg4j.search.score.Scorer

copy

public it.unimi.dsi.mg4j.search.score.Scorer copy()

Specified by:

copy in interface it.unimi.dsi.lang.FlyweightPrototype<it.unimi.dsi.mg4j.search.score.Scorer>

Specified by:

copy in interface it.unimi.dsi.mg4j.search.score.Scorer

wrap

public void wrap(it.unimi.dsi.mg4j.search.DocumentIterator d)
          throws IOException

Specified by:

wrap in interface it.unimi.dsi.mg4j.search.score.Scorer

Overrides:

wrap in class it.unimi.dsi.mg4j.search.score.AbstractWeightedScorer

Throws:

IOException