public class SweetSpotSimilarity extends ClassicSimilarity
A similarity with a lengthNorm that provides for a "plateau" of equally good lengths, and tf helper functions.
For lengthNorm, A min/max can be specified to define the plateau of lengths that should all have a norm of 1.0. Below the min, and above the max the lengthNorm drops off in a sqrt function.
For tf, baselineTf and hyperbolicTf functions are provided, which subclasses can choose between.
Similarity.SimScorerdiscountOverlaps| Constructor and Description |
|---|
SweetSpotSimilarity() |
| Modifier and Type | Method and Description |
|---|---|
float |
baselineTf(float freq)
Implemented as:
(x <= min) ? base : sqrt(x+(base**2)-min)
...but with a special case check for 0. |
float |
hyperbolicTf(float freq)
Uses a hyperbolic tangent function that allows for a hard max...
|
float |
lengthNorm(int numTerms)
Implemented as:
1/sqrt( steepness * (abs(x-min) + abs(x-max) - (max-min)) + 1 )
. |
void |
setBaselineTfFactors(float base,
float min)
Sets the baseline and minimum function variables for baselineTf
|
void |
setHyperbolicTfFactors(float min,
float max,
double base,
float xoffset)
Sets the function variables for the hyperbolicTf functions
|
void |
setLengthNormFactors(int min,
int max,
float steepness,
boolean discountOverlaps)
Sets the default function variables used by lengthNorm when no field
specific variables have been set.
|
float |
tf(float freq)
Delegates to baselineTf
|
String |
toString() |
idf, idfExplaincomputeNorm, getDiscountOverlaps, idfExplain, scorer, setDiscountOverlapspublic void setBaselineTfFactors(float base,
float min)
baselineTf(float)public void setHyperbolicTfFactors(float min,
float max,
double base,
float xoffset)
min - the minimum tf value to ever be returned (default: 0.0)max - the maximum tf value to ever be returned (default: 2.0)base - the base value to be used in the exponential for the hyperbolic function (default: 1.3)xoffset - the midpoint of the hyperbolic function (default: 10.0)hyperbolicTf(float)public void setLengthNormFactors(int min,
int max,
float steepness,
boolean discountOverlaps)
lengthNorm(int)public float lengthNorm(int numTerms)
1/sqrt( steepness * (abs(x-min) + abs(x-max) - (max-min)) + 1 )
.
This degrades to 1/sqrt(x) when min and max are both 1 and
steepness is 0.5
:TODO: potential optimization is to just flat out return 1.0f if numTerms is between min and max.
lengthNorm in class ClassicSimilaritysetLengthNormFactors(int, int, float, boolean),
An SVG visualization of this functionpublic float tf(float freq)
tf in class ClassicSimilaritybaselineTf(float)public float baselineTf(float freq)
(x <= min) ? base : sqrt(x+(base**2)-min)
...but with a special case check for 0.
This degrates to sqrt(x) when min and base are both 0
public float hyperbolicTf(float freq)
tf(x)=min+(max-min)/2*(((base**(x-xoffset)-base**-(x-xoffset))/(base**(x-xoffset)+base**-(x-xoffset)))+1)
This code is provided as a convenience for subclasses that want to use a hyperbolic tf function.
public String toString()
toString in class ClassicSimilarityCopyright © 2000-2021 Apache Software Foundation. All Rights Reserved.