/*
* 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{
/// <summary>Expert: Default scoring implementation. </summary>
[Serializable]
public class DefaultSimilarity : Similarity
{
/// <summary>Implemented as <code>1/sqrt(numTerms)</code>. </summary>
public override float LengthNorm(System.String fieldName, int numTerms)
{
return (float) (1.0 / System.Math.Sqrt(numTerms));
}
/// <summary>Implemented as <code>1/sqrt(sumOfSquaredWeights)</code>. </summary>
public override float QueryNorm(float sumOfSquaredWeights)
{
return (float) (1.0 / System.Math.Sqrt(sumOfSquaredWeights));
}
/// <summary>Implemented as <code>sqrt(freq)</code>. </summary>
public override float Tf(float freq)
{
return (float) System.Math.Sqrt(freq);
}
/// <summary>Implemented as <code>1 / (distance + 1)</code>. </summary>
public override float SloppyFreq(int distance)
{
return 1.0f / (distance + 1);
}
/// <summary>Implemented as <code>log(numDocs/(docFreq+1)) + 1</code>. </summary>
public override float Ldf(int docFreq, int numDocs)
{
return (float) (System.Math.Log(numDocs / (double) (docFreq + 1)) + 1.0);
}
/// <summary>Implemented as <code>overlap / maxOverlap</code>. </summary>
public override float Coord(int overlap, int maxOverlap)
{
return overlap / (float) maxOverlap;
}
}
}
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