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/*
* Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
* or more contributor license agreements. Licensed under the Elastic License
* 2.0 and the Server Side Public License, v 1; you may not use this file except
* in compliance with, at your election, the Elastic License 2.0 or the Server
* Side Public License, v 1.
*/
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.common.io.stream.StreamInput;
import org.elasticsearch.common.io.stream.StreamOutput;
import org.elasticsearch.search.suggest.phrase.WordScorer.WordScorerFactory;
import org.elasticsearch.xcontent.ParseField;
import org.elasticsearch.xcontent.XContentBuilder;
import org.elasticsearch.xcontent.XContentParser;
import org.elasticsearch.xcontent.XContentParser.Token;
import java.io.IOException;
import java.util.Objects;
/**
* An additive
* smoothing model.
*
* See N-Gram
* Smoothing for details.
*
*/
public final class Laplace extends SmoothingModel {
public static final String NAME = "laplace";
private static final ParseField ALPHA_FIELD = new ParseField("alpha");
static final ParseField PARSE_FIELD = new ParseField(NAME);
/**
* Default alpha parameter for laplace smoothing
*/
public static final double DEFAULT_LAPLACE_ALPHA = 0.5;
private double alpha = DEFAULT_LAPLACE_ALPHA;
/**
* Creates a Laplace smoothing model.
*
*/
public Laplace(double alpha) {
this.alpha = alpha;
}
/**
* Read from a stream.
*/
public Laplace(StreamInput in) throws IOException {
alpha = in.readDouble();
}
@Override
public void writeTo(StreamOutput out) throws IOException {
out.writeDouble(alpha);
}
/**
* @return the laplace model alpha parameter
*/
public double getAlpha() {
return this.alpha;
}
@Override
protected XContentBuilder innerToXContent(XContentBuilder builder, Params params) throws IOException {
builder.field(ALPHA_FIELD.getPreferredName(), alpha);
return builder;
}
@Override
public String getWriteableName() {
return NAME;
}
@Override
protected boolean doEquals(SmoothingModel other) {
Laplace otherModel = (Laplace) other;
return Objects.equals(alpha, otherModel.alpha);
}
@Override
protected int doHashCode() {
return Objects.hash(alpha);
}
public static SmoothingModel fromXContent(XContentParser parser) throws IOException {
XContentParser.Token token;
String fieldName = null;
double alpha = DEFAULT_LAPLACE_ALPHA;
while ((token = parser.nextToken()) != Token.END_OBJECT) {
if (token == XContentParser.Token.FIELD_NAME) {
fieldName = parser.currentName();
}
if (token.isValue() && ALPHA_FIELD.match(fieldName, parser.getDeprecationHandler())) {
alpha = parser.doubleValue();
}
}
return new Laplace(alpha);
}
@Override
public WordScorerFactory buildWordScorerFactory() {
return (IndexReader reader, Terms terms, String field, double realWordLikelihood, BytesRef separator) -> new LaplaceScorer(
reader,
terms,
field,
realWordLikelihood,
separator,
alpha
);
}
}