| package org.apache.lucene.search; |
| |
| /** |
| * Copyright 2004 The Apache Software Foundation |
| * |
| * Licensed 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. |
| */ |
| |
| /** Expert: Default scoring implementation. */ |
| public class DefaultSimilarity extends Similarity { |
| /** Implemented as <code>1/sqrt(numTerms)</code>. */ |
| public float lengthNorm(String fieldName, int numTerms) { |
| return (float)(1.0 / Math.sqrt(numTerms)); |
| } |
| |
| /** Implemented as <code>1/sqrt(sumOfSquaredWeights)</code>. */ |
| public float queryNorm(float sumOfSquaredWeights) { |
| return (float)(1.0 / Math.sqrt(sumOfSquaredWeights)); |
| } |
| |
| /** Implemented as <code>sqrt(freq)</code>. */ |
| public float tf(float freq) { |
| return (float)Math.sqrt(freq); |
| } |
| |
| /** Implemented as <code>1 / (distance + 1)</code>. */ |
| public float sloppyFreq(int distance) { |
| return 1.0f / (distance + 1); |
| } |
| |
| /** Implemented as <code>log(numDocs/(docFreq+1)) + 1</code>. */ |
| public float idf(int docFreq, int numDocs) { |
| return (float)(Math.log(numDocs/(double)(docFreq+1)) + 1.0); |
| } |
| |
| /** Implemented as <code>overlap / maxOverlap</code>. */ |
| public float coord(int overlap, int maxOverlap) { |
| return overlap / (float)maxOverlap; |
| } |
| } |