meta::index::jelinek_mercer Class Reference

Implements the Jelinek-Mercer smoothed ranking model. More...

#include <jelinek_mercer.h>

Inheritance diagram for meta::index::jelinek_mercer:

Public Member Functions
	jelinek_mercer (double lambda=default_lambda)
double	smoothed_prob (const score_data &sd) const override
	Calculates the smoothed probability of a term. More...
double	doc_constant (const score_data &sd) const override
	A document-dependent constant. More...
Public Member Functions inherited from meta::index::language_model_ranker
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	~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 = "jelinek-mercer"
	The identifier for this ranker.
static const constexpr double	default_lambda = 0.7
	Default value of lambda.
Static Public Attributes inherited from meta::index::language_model_ranker
static const std::string	id = "language-model"
	The identifier for this ranker.

Private Attributes
const double	lambda_
	the JM parameter

Detailed Description

Implements the Jelinek-Mercer smoothed ranking model.

This smoothing method can be viewed as a linear interpolation between the query term probablity and the collection term probability. The model parameter lambda is the weighting of this interpolation.

Constructor & Destructor Documentation

meta::index::jelinek_mercer::jelinek_mercer

(

double

lambda = default_lambda

)

Parameters

lambda

Member Function Documentation

double meta::index::jelinek_mercer::smoothed_prob ( const score_data &  sd ) const

overridevirtual

Calculates the smoothed probability of a term.

Parameters

sd

Implements meta::index::language_model_ranker.

double meta::index::jelinek_mercer::doc_constant ( const score_data &  sd ) const

overridevirtual

A document-dependent constant.

Parameters

sd

Implements meta::index::language_model_ranker.

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

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