/*
* 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.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<ExponentialDecayFunctionBuilder> {
public static final String NAME = "exp";
public static final ScoreFunctionParser<ExponentialDecayFunctionBuilder> 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();
}
}
}