| package org.apache.lucene.search.similarities; |
| |
| /* |
| * 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. |
| */ |
| |
| import org.apache.lucene.search.Explanation; |
| |
| /** |
| * Model of the information gain based on the ratio of two Bernoulli processes. |
| * @lucene.experimental |
| */ |
| public class AfterEffectB extends AfterEffect { |
| |
| /** Sole constructor: parameter-free */ |
| public AfterEffectB() {} |
| |
| @Override |
| public final float score(BasicStats stats, float tfn) { |
| long F = stats.getTotalTermFreq()+1; |
| long n = stats.getDocFreq()+1; |
| return (F + 1) / (n * (tfn + 1)); |
| } |
| |
| @Override |
| public final Explanation explain(BasicStats stats, float tfn) { |
| Explanation result = new Explanation(); |
| result.setDescription(getClass().getSimpleName() + ", computed from: "); |
| result.setValue(score(stats, tfn)); |
| result.addDetail(new Explanation(tfn, "tfn")); |
| result.addDetail(new Explanation(stats.getTotalTermFreq(), "totalTermFreq")); |
| result.addDetail(new Explanation(stats.getDocFreq(), "docFreq")); |
| return result; |
| } |
| |
| @Override |
| public String toString() { |
| return "B"; |
| } |
| } |
