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DistributionLL.cs
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DistributionLL.cs
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using System;
namespace Lucene.Net.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.
*/
/// <summary>
/// Log-logistic distribution.
/// <para>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.</para>
/// @lucene.experimental
/// </summary>
public class DistributionLL : Distribution
{
/// <summary>
/// Sole constructor: parameter-free </summary>
public DistributionLL()
{
}
public override sealed float Score(BasicStats stats, float tfn, float lambda)
{
return (float)-Math.Log(lambda / (tfn + lambda));
}
public override string ToString()
{
return "LL";
}
}
}