| 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> |
| /// This class acts as the base class for the implementations of the term |
| /// frequency normalization methods in the DFR framework. |
| /// <para/> |
| /// @lucene.experimental |
| /// </summary> |
| /// <seealso cref="DFRSimilarity"/> |
| public abstract class Normalization |
| { |
| /// <summary> |
| /// Sole constructor. (For invocation by subclass |
| /// constructors, typically implicit.) |
| /// </summary> |
| public Normalization() |
| { |
| } |
| |
| /// <summary> |
| /// Returns the normalized term frequency. </summary> |
| /// <param name="len"> the field length. </param> |
| public abstract float Tfn(BasicStats stats, float tf, float len); |
| |
| /// <summary> |
| /// Returns an explanation for the normalized term frequency. |
| /// <para>The default normalization methods use the field length of the document |
| /// and the average field length to compute the normalized term frequency. |
| /// This method provides a generic explanation for such methods. |
| /// Subclasses that use other statistics must override this method.</para> |
| /// </summary> |
| public virtual Explanation Explain(BasicStats stats, float tf, float len) |
| { |
| Explanation result = new Explanation(); |
| result.Description = this.GetType().Name + ", computed from: "; |
| result.Value = Tfn(stats, tf, len); |
| result.AddDetail(new Explanation(tf, "tf")); |
| result.AddDetail(new Explanation(stats.AvgFieldLength, "avgFieldLength")); |
| result.AddDetail(new Explanation(len, "len")); |
| return result; |
| } |
| |
| /// <summary> |
| /// Implementation used when there is no normalization. </summary> |
| public sealed class NoNormalization : Normalization |
| { |
| /// <summary> |
| /// Sole constructor: parameter-free </summary> |
| public NoNormalization() |
| { |
| } |
| |
| public override float Tfn(BasicStats stats, float tf, float len) |
| { |
| return tf; |
| } |
| |
| public override Explanation Explain(BasicStats stats, float tf, float len) |
| { |
| return new Explanation(1, "no normalization"); |
| } |
| |
| public override string ToString() |
| { |
| return ""; |
| } |
| } |
| |
| /// <summary> |
| /// Subclasses must override this method to return the code of the |
| /// normalization formula. Refer to the original paper for the list. |
| /// </summary> |
| public override abstract string ToString(); |
| } |
| } |