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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.index.query.functionscore;
import org.apache.lucene.search.Explanation;
import org.elasticsearch.common.bytes.BytesReference;
import org.elasticsearch.common.io.stream.StreamInput;
import java.io.IOException;
public class ExponentialDecayFunctionBuilder extends DecayFunctionBuilder {
public static final String NAME = "exp";
public static final ScoreFunctionParser PARSER = new DecayFunctionParser<>(
ExponentialDecayFunctionBuilder::new
);
public static final DecayFunction EXP_DECAY_FUNCTION = new ExponentialDecayScoreFunction();
public ExponentialDecayFunctionBuilder(String fieldName, Object origin, Object scale, Object offset) {
super(fieldName, origin, scale, offset);
}
public ExponentialDecayFunctionBuilder(String fieldName, Object origin, Object scale, Object offset, double decay) {
super(fieldName, origin, scale, offset, decay);
}
ExponentialDecayFunctionBuilder(String fieldName, BytesReference functionBytes) {
super(fieldName, functionBytes);
}
/**
* Read from a stream.
*/
public ExponentialDecayFunctionBuilder(StreamInput in) throws IOException {
super(in);
}
@Override
public String getName() {
return NAME;
}
@Override
public DecayFunction getDecayFunction() {
return EXP_DECAY_FUNCTION;
}
private static final class ExponentialDecayScoreFunction implements DecayFunction {
@Override
public double evaluate(double value, double scale) {
return Math.exp(scale * value);
}
@Override
public Explanation explainFunction(String valueExpl, double value, double scale) {
return Explanation.match((float) evaluate(value, scale), "exp(- " + valueExpl + " * " + -1 * scale + ")");
}
@Override
public double processScale(double scale, double decay) {
return Math.log(decay) / scale;
}
@Override
public int hashCode() {
return this.getClass().hashCode();
}
@Override
public boolean equals(Object obj) {
if (super.equals(obj)) {
return true;
}
return obj != null && getClass() != obj.getClass();
}
}
}