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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you under
* the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
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;
//TODO public for tests
public final class LinearInterpoatingScorer extends WordScorer {
private final double unigramLambda;
private final double bigramLambda;
private final double trigramLambda;
public LinearInterpoatingScorer(IndexReader reader, Terms terms, String field, double realWordLikelyhood, BytesRef separator,
double trigramLambda, double bigramLambda, double unigramLambda) throws IOException {
super(reader, terms, field, realWordLikelyhood, separator);
double sum = unigramLambda + bigramLambda + trigramLambda;
this.unigramLambda = unigramLambda / sum;
this.bigramLambda = bigramLambda / sum;
this.trigramLambda = trigramLambda / sum;
}
double trigramLambda() {
return this.trigramLambda;
}
double bigramLambda() {
return this.bigramLambda;
}
double unigramLambda() {
return this.unigramLambda;
}
@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 unigramLambda * scoreUnigram(word);
}
return bigramLambda * (count / (0.5d+w_1.frequency)) + unigramLambda * scoreUnigram(word);
}
@Override
protected double scoreTrigram(Candidate w, Candidate w_1, Candidate w_2) throws IOException {
SuggestUtils.join(separator, spare, w.term, w_1.term, w_2.term);
final long count = frequency(spare.get());
if (count < 1) {
return scoreBigram(w, w_1);
}
SuggestUtils.join(separator, spare, w.term, w_1.term);
return trigramLambda * (count / (1.d+frequency(spare.get()))) + scoreBigram(w, w_1);
}
}
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