package org.apache.lucene.search;
/**
* 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.
*/
/** Expert: Default scoring implementation. */
public class DefaultSimilarity extends Similarity {
/** Implemented as `1/sqrt(numTerms)`

. */
public float lengthNorm(String fieldName, int numTerms) {
return (float)(1.0 / Math.sqrt(numTerms));
}
/** Implemented as `1/sqrt(sumOfSquaredWeights)`

. */
public float queryNorm(float sumOfSquaredWeights) {
return (float)(1.0 / Math.sqrt(sumOfSquaredWeights));
}
/** Implemented as `sqrt(freq)`

. */
public float tf(float freq) {
return (float)Math.sqrt(freq);
}
/** Implemented as `1 / (distance + 1)`

. */
public float sloppyFreq(int distance) {
return 1.0f / (distance + 1);
}
/** Implemented as `log(numDocs/(docFreq+1)) + 1`

. */
public float idf(int docFreq, int numDocs) {
return (float)(Math.log(numDocs/(double)(docFreq+1)) + 1.0);
}
/** Implemented as `overlap / maxOverlap`

. */
public float coord(int overlap, int maxOverlap) {
return overlap / (float)maxOverlap;
}
}