meta::index::language_model_ranker Class Reference

Scores documents according to one of three different smoothed language model scoring methods described in "A Study of Smoothing Methods for Language Models Applied to Ad Hoc Information Retrieval" by Zhai and Lafferty, 2001. More...

#include <lm_ranker.h>

Inheritance diagram for meta::index::language_model_ranker:

Public Member Functions
double	score_one (const score_data &sd) override
double	initial_score (const score_data &sd) const override
	Computes the constant contribution to the score of a particular document. More...
virtual double	smoothed_prob (const score_data &sd) const =0
	Calculates the smoothed probability of a term. More...
virtual double	doc_constant (const score_data &sd) const =0
	A document-dependent constant. More...
virtual	~language_model_ranker ()=default
	Default destructor.
Public Member Functions inherited from meta::index::ranker
std::vector< std::pair< doc_id, double > >	score (inverted_index &idx, corpus::document &query, uint64_t num_results=10, const std::function< bool(doc_id d_id)> &filter=[](doc_id){return true;})
virtual	~ranker ()=default
	Default destructor.

Static Public Attributes
static const std::string	id = "language-model"
	The identifier for this ranker.

Detailed Description

Scores documents according to one of three different smoothed language model scoring methods described in "A Study of Smoothing Methods for Language Models Applied to Ad Hoc Information Retrieval" by Zhai and Lafferty, 2001.

Member Function Documentation

double meta::index::language_model_ranker::score_one ( const score_data &  sd )

overridevirtual

Parameters

sd

Implements meta::index::ranker.

double meta::index::language_model_ranker::initial_score ( const score_data &  sd ) const

overridevirtual

Computes the constant contribution to the score of a particular document.

Parameters

sd	The score_data for the query

Reimplemented from meta::index::ranker.

virtual double meta::index::language_model_ranker::smoothed_prob ( const score_data &  sd ) const

pure virtual

Calculates the smoothed probability of a term.

Parameters

sd

Implemented in meta::index::jelinek_mercer, meta::index::absolute_discount, and meta::index::dirichlet_prior.

virtual double meta::index::language_model_ranker::doc_constant ( const score_data &  sd ) const

pure virtual

A document-dependent constant.

Parameters

sd

Implemented in meta::index::jelinek_mercer, meta::index::absolute_discount, and meta::index::dirichlet_prior.

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The documentation for this class was generated from the following files:

• /home/chase/projects/meta/include/index/ranker/lm_ranker.h
• /home/chase/projects/meta/src/index/ranker/lm_ranker.cpp