| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF 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.apache.lucene.search.similarities; |
| |
| |
| /** |
| * Log-logistic distribution. |
| * <p>Unlike for DFR, the natural logarithm is used, as |
| * it is faster to compute and the original paper does not express any |
| * preference to a specific base.</p> |
| * @lucene.experimental |
| */ |
| public class DistributionLL extends Distribution { |
| |
| /** Sole constructor: parameter-free */ |
| public DistributionLL() {} |
| |
| @Override |
| public final double score(BasicStats stats, double tfn, double lambda) { |
| return -Math.log(lambda / (tfn + lambda)); |
| } |
| |
| @Override |
| public String toString() { |
| return "LL"; |
| } |
| } |