org.elasticsearch.search.suggest.phrase.LaplaceScorer Maven / Gradle / Ivy
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package org.elasticsearch.search.suggest.phrase;
import java.io.IOException;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.util.BytesRef;
import org.elasticsearch.search.suggest.SuggestUtils;
import org.elasticsearch.search.suggest.phrase.DirectCandidateGenerator.Candidate;
//TODO public for tests
public final class LaplaceScorer extends WordScorer {
public static final WordScorerFactory FACTORY = new WordScorer.WordScorerFactory() {
@Override
public WordScorer newScorer(IndexReader reader, String field, double realWordLikelyhood, BytesRef separator) throws IOException {
return new LaplaceScorer(reader, field, realWordLikelyhood, separator, 0.5);
}
};
private double alpha;
public LaplaceScorer(IndexReader reader, String field,
double realWordLikelyhood, BytesRef separator, double alpha) throws IOException {
super(reader, field, realWordLikelyhood, separator);
this.alpha = alpha;
}
@Override
protected double scoreBigram(Candidate word, Candidate w_1) throws IOException {
SuggestUtils.join(separator, spare, w_1.term, word.term);
return (alpha + frequency(spare)) / (alpha + w_1.frequency + vocabluarySize);
}
@Override
protected double scoreTrigram(Candidate word, Candidate w_1, Candidate w_2) throws IOException {
SuggestUtils.join(separator, spare, w_2.term, w_1.term, word.term);
long trigramCount = frequency(spare);
SuggestUtils.join(separator, spare, w_1.term, word.term);
return (alpha + trigramCount) / (alpha + frequency(spare) + vocabluarySize);
}
}