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package com.wcohen.ss;
import com.wcohen.ss.api.*;
import java.util.*;
/**
* Abstract StringDistanceLearner class which averages results of a number of
* inner distance metrics, learned by a number of inner distance learners.
*/
public class AveragedStringDistanceLearner extends CombinedStringDistanceLearner
{
MultiStringWrapper prototype = null;
public AveragedStringDistanceLearner() { super(); }
public AveragedStringDistanceLearner(StringDistanceLearner[] innerLearners, String delim) { super(innerLearners,delim); }
protected void comboSetStringWrapperPool(Iterator it) {
if (it.hasNext()) prototype = asMultiStringWrapper( (StringWrapper) it.next() );
}
protected boolean comboHasNextQuery() { return false; }
protected DistanceInstance comboNextQuery() { return null; }
protected void comboAddExample(DistanceInstance di) { ; }
protected void comboSetDistanceInstancePool(Iterator i) {
// use the first example to build a prototype
}
public StringDistance getDistance() {
if (prototype==null) throw new IllegalStateException("need to be trained first");
return new AveragedStringDistance(getInnerDistances(), prototype);
}
//
// average of some string distances
//
private class AveragedStringDistance extends CombinedStringDistance
{
public AveragedStringDistance(StringDistance[] innerDistances, MultiStringWrapper prototype)
{
super(innerDistances,prototype);
}
protected double doScore(MultiStringWrapper ms,MultiStringWrapper mt)
{
double totScore = 0.0;
for (int i=0; i<ms.size(); i++) {
StringDistance d = innerDistances[ ms.getDistanceLearnerIndex(i) ];
totScore += d.score( ms.get(i), mt.get(i) );
}
return totScore/ms.size();
}
protected String explainCombination(MultiStringWrapper ms,MultiStringWrapper mt)
{
return "Final score is the average\n";
}
public String toString()
{
return "[Average of:"+innerDistanceString()+"]";
}
}
}
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