Class ReciprocalSingleFunction

ReciprocalSingleFunction implements a reciprocal function f(x) = a/(mx+b), based on the value of a field or function as exported by ValueSource.

When a and b are equal, and x>=0, this function has a maximum value of 1 that drops as x increases. Increasing the value of a and b together results in a movement of the entire function to a flatter part of the curve.

These properties make this an idea function for boosting more recent documents.

Example: recip(ms(NOW,mydatefield),3.16e-11,1,1)

A multiplier of 3.16e-11 changes the units from milliseconds to years (since there are about 3.16e10 milliseconds per year). Thus, a very recent date will yield a value close to 1/(0+1) or 1, a date a year in the past will get a multiplier of about 1/(1+1) or 1/2, and date two years old will yield 1/(2+1) or 1/3.

NOTE: This was ReciprocalFloatFunction in Lucene

Inheritance
System.Object
ValueSource
ReciprocalSingleFunction
Inherited Members
Namespace: Lucene.Net.Queries.Function.ValueSources
Assembly: Lucene.Net.Queries.dll
Syntax
public class ReciprocalSingleFunction : ValueSource

Constructors

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ReciprocalSingleFunction(ValueSource, Single, Single, Single)

f(source) = a/(m*float(source)+b)

Declaration
public ReciprocalSingleFunction(ValueSource source, float m, float a, float b)
Parameters
Type Name Description
ValueSource source
System.Single m
System.Single a
System.Single b

Fields

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m_a

Declaration
protected readonly float m_a
Field Value
Type Description
System.Single
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m_b

Declaration
protected readonly float m_b
Field Value
Type Description
System.Single
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m_m

Declaration
protected readonly float m_m
Field Value
Type Description
System.Single
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m_source

Declaration
protected readonly ValueSource m_source
Field Value
Type Description
ValueSource

Methods

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CreateWeight(IDictionary, IndexSearcher)

Declaration
public override void CreateWeight(IDictionary context, IndexSearcher searcher)
Parameters
Type Name Description
IDictionary context
IndexSearcher searcher
Overrides
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Equals(Object)

Declaration
public override bool Equals(object o)
Parameters
Type Name Description
System.Object o
Returns
Type Description
System.Boolean
Overrides
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GetDescription()

Declaration
public override string GetDescription()
Returns
Type Description
System.String
Overrides
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GetHashCode()

Declaration
public override int GetHashCode()
Returns
Type Description
System.Int32
Overrides
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GetValues(IDictionary, AtomicReaderContext)

Declaration
public override FunctionValues GetValues(IDictionary context, AtomicReaderContext readerContext)
Parameters
Type Name Description
IDictionary context
AtomicReaderContext readerContext
Returns
Type Description
FunctionValues
Overrides

See Also