org.elasticsearch.search.suggest.phrase.StupidBackoffScorer Maven / Gradle / Ivy
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* the Apache License, Version 2.0 (the "License"); you may
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*
* http://www.apache.org/licenses/LICENSE-2.0
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package org.elasticsearch.search.suggest.phrase;
import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Terms;
import org.apache.lucene.util.BytesRef;
import org.elasticsearch.search.suggest.SuggestUtils;
import org.elasticsearch.search.suggest.phrase.DirectCandidateGenerator.Candidate;
import java.io.IOException;
class StupidBackoffScorer extends WordScorer {
private final double discount;
public StupidBackoffScorer(IndexReader reader, Terms terms,String field, double realWordLikelyhood, BytesRef separator, double discount)
throws IOException {
super(reader, terms, field, realWordLikelyhood, separator);
this.discount = discount;
}
double discount() {
return this.discount;
}
@Override
protected double scoreBigram(Candidate word, Candidate w_1) throws IOException {
SuggestUtils.join(separator, spare, w_1.term, word.term);
final long count = frequency(spare.get());
if (count < 1) {
return discount * scoreUnigram(word);
}
return count / (w_1.frequency + 0.00000000001d);
}
@Override
protected double scoreTrigram(Candidate w, Candidate w_1, Candidate w_2) throws IOException {
// First see if there are bigrams. If there aren't then skip looking up the trigram. This saves lookups
// when the bigrams and trigrams are rare and we need both anyway.
SuggestUtils.join(separator, spare, w_1.term, w.term);
long bigramCount = frequency(spare.get());
if (bigramCount < 1) {
return discount * scoreUnigram(w);
}
SuggestUtils.join(separator, spare, w_2.term, w_1.term, w.term);
long trigramCount = frequency(spare.get());
if (trigramCount < 1) {
return discount * (bigramCount / (w_1.frequency + 0.00000000001d));
}
return trigramCount / (bigramCount + 0.00000000001d);
}
}