Class ReciprocalSingleFunction

ReciprocalSingleFunction implements a reciprocal function f(x) = a/(mx+b), based on the float 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

object

ValueSource

ReciprocalSingleFunction

Inherited Members

ValueSource.ToString()

ValueSource.NewContext(IndexSearcher)

ValueSource.GetSortField(bool)

object.Equals(object, object)

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: Lucene.Net.Queries.Function.ValueSources

Assembly: Lucene.Net.Queries.dll

Syntax

public class ReciprocalSingleFunction : ValueSource

Constructors

ReciprocalSingleFunction(ValueSource, float, float, float)

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

Declaration

public ReciprocalSingleFunction(ValueSource source, float m, float a, float b)

Parameters

Type	Name	Description
ValueSource	source
float	m
float	a
float	b

See Also

FunctionQuery

Fields

m_a

ReciprocalSingleFunction implements a reciprocal function f(x) = a/(mx+b), based on the float 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

Declaration

protected readonly float m_a

Field Value

Type	Description
float

See Also

FunctionQuery

m_b

ReciprocalSingleFunction implements a reciprocal function f(x) = a/(mx+b), based on the float 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

Declaration

protected readonly float m_b

Field Value

Type	Description
float

See Also

FunctionQuery

m_m

ReciprocalSingleFunction implements a reciprocal function f(x) = a/(mx+b), based on the float 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

Declaration

protected readonly float m_m

Field Value

Type	Description
float

See Also

FunctionQuery

m_source

ReciprocalSingleFunction implements a reciprocal function f(x) = a/(mx+b), based on the float 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

Declaration

protected readonly ValueSource m_source

Field Value

Type	Description
ValueSource

See Also

FunctionQuery

Methods

CreateWeight(IDictionary, IndexSearcher)

Implementations should propagate CreateWeight to sub-ValueSources which can optionally store weight info in the context. The context object will be passed to GetValues() where this info can be retrieved.

Declaration

public override void CreateWeight(IDictionary context, IndexSearcher searcher)

Parameters

Type	Name	Description
IDictionary	context
IndexSearcher	searcher

Overrides

ValueSource.CreateWeight(IDictionary, IndexSearcher)

See Also

FunctionQuery

Equals(object)

Determines whether the specified object is equal to the current object.

Declaration

public override bool Equals(object o)

Parameters

Type	Name	Description
object	o

Returns

Type	Description
bool	true if the specified object is equal to the current object; otherwise, false.

Overrides

ValueSource.Equals(object)

See Also

FunctionQuery

GetDescription()

description of field, used in Explain()

Declaration

public override string GetDescription()

Returns

Type	Description
string

Overrides

ValueSource.GetDescription()

See Also

FunctionQuery

GetHashCode()

Serves as the default hash function.

Declaration

public override int GetHashCode()

Returns

Type	Description
int	A hash code for the current object.

Overrides

ValueSource.GetHashCode()

See Also

FunctionQuery

GetValues(IDictionary, AtomicReaderContext)

Gets the values for this reader and the context that was previously passed to CreateWeight(IDictionary, IndexSearcher)

Declaration

public override FunctionValues GetValues(IDictionary context, AtomicReaderContext readerContext)

Parameters

Type	Name	Description
IDictionary	context
AtomicReaderContext	readerContext

Returns

Type	Description
FunctionValues

Overrides

ValueSource.GetValues(IDictionary, AtomicReaderContext)

See Also

FunctionQuery

See Also

FunctionQuery