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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.index.query.functionscore;
import org.apache.lucene.search.Explanation;
/**
* Implement this interface to provide a decay function that is executed on a
* distance. For example, this could be an exponential drop of, a triangle
* function or something of the kind. This is used, for example, by
* {@link GaussDecayFunctionBuilder}.
*
*/
public interface DecayFunction {
double evaluate(double value, double scale);
Explanation explainFunction(String valueString, double value, double scale);
/**
* The final scale parameter is computed from the scale parameter given by
* the user and a value. This value is the value that the decay function
* should compute if document distance and user defined scale equal. The
* scale parameter for the function must be adjusted accordingly in this
* function
*
* @param scale
* the raw scale value given by the user
* @param decay
* the value which decay function should take once the distance
* reaches this scale
* */
double processScale(double scale, double decay);
}