Class CombinedMatchEngine
- java.lang.Object
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- uk.ac.starlink.table.join.CombinedMatchEngine
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- All Implemented Interfaces:
MatchEngine
public class CombinedMatchEngine extends java.lang.Object implements MatchEngine
A matching engine which provides matching facilities by combining the characteristics of a number of other matching engines. Because of the way it calculates bins (effectively multiplying one bin array by another), it is a good idea for efficiency's sake to keep down the number of bins returned by theMatchKit.getBins(java.lang.Object[])
method of the component match engines.The match score is formed by taking the scaled match scores of the constituent engines and adding them in quadrature (if no scaling is available, unscaled values are used). Versions of this class before 2017 did not do that, it just added unscaled match scores together, which doesn't make much sense.
- Author:
- Mark Taylor (Starlink)
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Constructor Summary
Constructors Constructor Description CombinedMatchEngine(MatchEngine[] engines)
Constructs a new MatchEngine based on a sequence of others.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description java.util.function.Supplier<Coverage>
createCoverageFactory()
Returns a supplier for coverage objects.java.util.function.Supplier<MatchKit>
createMatchKitFactory()
Returns a factory for MatchKit instances corresponding to the current settings of this object.uk.ac.starlink.table.DescribedValue[]
getMatchParameters()
Returns a set of DescribedValue objects whose values can be modified to modify the matching criteria.uk.ac.starlink.table.ValueInfo
getMatchScoreInfo()
Returns a description of the value returned by theMatchKit.matchScore(java.lang.Object[], java.lang.Object[])
method.double
getScoreScale()
Returns the square root of the number of constituent matchers if they all have definite score scaling values.uk.ac.starlink.table.DescribedValue[]
getTuningParameters()
Returns a set of DescribedValue objects whose values can be modified to tune the performance of the match.uk.ac.starlink.table.ValueInfo[]
getTupleInfos()
Returns a set of ValueInfo objects indicating what is required for the elements of each tuple.void
setName(java.lang.String name)
java.lang.String
toString()
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Constructor Detail
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CombinedMatchEngine
public CombinedMatchEngine(MatchEngine[] engines)
Constructs a new MatchEngine based on a sequence of others. The tuples accepted by this engine are composed of the tuples of its constituent engines (as specified by engines) concatenated in sequence.- Parameters:
engines
- match engine sequence to be combined
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Method Detail
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createMatchKitFactory
public java.util.function.Supplier<MatchKit> createMatchKitFactory()
Description copied from interface:MatchEngine
Returns a factory for MatchKit instances corresponding to the current settings of this object.The returned value is immutable, and is not affected by subsequent changes of the settings of this object.
- Specified by:
createMatchKitFactory
in interfaceMatchEngine
- Returns:
- match kit supplier
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createCoverageFactory
public java.util.function.Supplier<Coverage> createCoverageFactory()
Description copied from interface:MatchEngine
Returns a supplier for coverage objects. Each such coverage can be used to characterise a region of tuple space. When populated with a set of tuples A, any tuple for which the inclusion function defined by itsCoverage.createTestFactory()
method returns false is guaranteed not to match any tuple in A according to this object's match criteria.The returned value is immutable, and is not affected by subsequent changes of the settings of this object.
If no suitable implementation is available, null may be returned.
- Specified by:
createCoverageFactory
in interfaceMatchEngine
- Returns:
- supplier of coverage objects, or null
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getScoreScale
public double getScoreScale()
Returns the square root of the number of constituent matchers if they all have definite score scaling values. Otherwise, returns NaN.- Specified by:
getScoreScale
in interfaceMatchEngine
- Returns:
- scale of successful match scores, a positive finite number or NaN
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getMatchScoreInfo
public uk.ac.starlink.table.ValueInfo getMatchScoreInfo()
Description copied from interface:MatchEngine
Returns a description of the value returned by theMatchKit.matchScore(java.lang.Object[], java.lang.Object[])
method. The content class should be numeric (though need not beDouble
), and the name, description and units should be descriptive of whatever the physical significance of the value is. If the result ofmatchScore
is not interesting (for instance, if it's always either 0 or -1),null
may be returned.- Specified by:
getMatchScoreInfo
in interfaceMatchEngine
- Returns:
- metadata for the match score results
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getTupleInfos
public uk.ac.starlink.table.ValueInfo[] getTupleInfos()
Description copied from interface:MatchEngine
Returns a set of ValueInfo objects indicating what is required for the elements of each tuple. The length of this array is the number of elements in the tuple. Each element should at least have a defined name and content class. The info's nullable attribute has a special meaning: if true it means that it makes sense for this element of the tuple to be always blank (for instance assigned to no column).- Specified by:
getTupleInfos
in interfaceMatchEngine
- Returns:
- array of objects describing the requirements on each element of the tuples used for matching
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getMatchParameters
public uk.ac.starlink.table.DescribedValue[] getMatchParameters()
Description copied from interface:MatchEngine
Returns a set of DescribedValue objects whose values can be modified to modify the matching criteria. Typically at least one of these will be some sort of tolerance separation which determines how close tuples must be to count as a match. This match engine's behaviour can be modified by callingDescribedValue.setValue(java.lang.Object)
on the returned objects.- Specified by:
getMatchParameters
in interfaceMatchEngine
- Returns:
- array of described values which influence the match
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getTuningParameters
public uk.ac.starlink.table.DescribedValue[] getTuningParameters()
Description copied from interface:MatchEngine
Returns a set of DescribedValue objects whose values can be modified to tune the performance of the match. This match engine's performance can be influenced by callingDescribedValue.setValue(java.lang.Object)
on the returned objects.Changing these values will make no difference to the output of
MatchKit.matchScore(java.lang.Object[], java.lang.Object[])
, but may change the output ofMatchKit.getBins(java.lang.Object[])
. This may change the CPU and memory requirements of the match, but will not change the result. The default value should be something sensible, so that setting the value of these parameters is not in general required.- Specified by:
getTuningParameters
in interfaceMatchEngine
- Returns:
- array of described values which may influence match performance
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setName
public void setName(java.lang.String name)
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toString
public java.lang.String toString()
- Overrides:
toString
in classjava.lang.Object
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