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* 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.lin;
import org.apache.lucene.search.Explanation;
import org.elasticsearch.index.query.functionscore.DecayFunction;
import org.elasticsearch.index.query.functionscore.DecayFunctionParser;
public class LinearDecayFunctionParser extends DecayFunctionParser {
public static final String[] NAMES = { "linear" };
@Override
public String[] getNames() {
return NAMES;
}
public static final DecayFunction decayFunction = new LinearDecayScoreFunction();
@Override
public DecayFunction getDecayFunction() {
return decayFunction;
}
final static class LinearDecayScoreFunction implements DecayFunction {
@Override
public double evaluate(double value, double scale) {
return Math.max(0.0, (scale - value) / scale);
}
@Override
public Explanation explainFunction(String valueExpl, double value, double scale) {
return Explanation.match(
(float) evaluate(value, scale),
"max(0.0, ((" + scale + " - " + valueExpl + ")/" + scale + ")");
}
@Override
public double processScale(double scale, double decay) {
return scale / (1.0 - decay);
}
}
}