/* * 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. */ using System; namespace Lucene.Net.Search { /// Expert: Default scoring implementation. public class DefaultSimilarity:Similarity { /// Implemented as 1/sqrt(numTerms). public override float LengthNorm(System.String fieldName, int numTerms) { return (float) (1.0 / System.Math.Sqrt(numTerms)); } /// Implemented as 1/sqrt(sumOfSquaredWeights). public override float QueryNorm(float sumOfSquaredWeights) { return (float) (1.0 / System.Math.Sqrt(sumOfSquaredWeights)); } /// Implemented as sqrt(freq). public override float Tf(float freq) { return (float) System.Math.Sqrt(freq); } /// Implemented as 1 / (distance + 1). public override float SloppyFreq(int distance) { return 1.0f / (distance + 1); } /// Implemented as log(numDocs/(docFreq+1)) + 1. public override float Idf(int docFreq, int numDocs) { return (float) (System.Math.Log(numDocs / (double) (docFreq + 1)) + 1.0); } /// Implemented as overlap / maxOverlap. public override float Coord(int overlap, int maxOverlap) { return overlap / (float) maxOverlap; } } }