Class CombinedMatchEngine

  • 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 the MatchKit.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)
    • Constructor Summary

      Constructors 
      Constructor Description
      CombinedMatchEngine​(MatchEngine[] engines)
      Constructs a new MatchEngine based on a sequence of others.
    • 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 the MatchKit.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()  
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
    • Constructor Detail

      • 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
    • Method Detail

      • 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 interface MatchEngine
        Returns:
        match kit supplier
      • 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 its Coverage.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 interface MatchEngine
        Returns:
        supplier of coverage objects, or null
      • 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 interface MatchEngine
        Returns:
        scale of successful match scores, a positive finite number or NaN
      • getMatchScoreInfo

        public uk.ac.starlink.table.ValueInfo getMatchScoreInfo()
        Description copied from interface: MatchEngine
        Returns a description of the value returned by the MatchKit.matchScore(java.lang.Object[], java.lang.Object[]) method. The content class should be numeric (though need not be Double), and the name, description and units should be descriptive of whatever the physical significance of the value is. If the result of matchScore is not interesting (for instance, if it's always either 0 or -1), null may be returned.
        Specified by:
        getMatchScoreInfo in interface MatchEngine
        Returns:
        metadata for the match score results
      • 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 interface MatchEngine
        Returns:
        array of objects describing the requirements on each element of the tuples used for matching
      • 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 calling DescribedValue.setValue(java.lang.Object) on the returned objects.
        Specified by:
        getMatchParameters in interface MatchEngine
        Returns:
        array of described values which influence the match
      • 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 calling DescribedValue.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 of MatchKit.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 interface MatchEngine
        Returns:
        array of described values which may influence match performance
      • setName

        public void setName​(java.lang.String name)
      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object