

Lucene example source code file (DefaultSimilarity.java)
The Lucene DefaultSimilarity.java source codepackage org.apache.lucene.search; import org.apache.lucene.index.FieldInvertState; /** * 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/LICENSE2.0 * * 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 * <code>state.getBoost()*lengthNorm(numTerms), where * <code>numTerms is {@link FieldInvertState#getLength()} if {@link * #setDiscountOverlaps} is false, else it's {@link * FieldInvertState#getLength()}  {@link * FieldInvertState#getNumOverlap()}. * * @lucene.experimental */ @Override public float computeNorm(String field, FieldInvertState state) { final int numTerms; if (discountOverlaps) numTerms = state.getLength()  state.getNumOverlap(); else numTerms = state.getLength(); return state.getBoost() * ((float) (1.0 / Math.sqrt(numTerms))); } /** Implemented as <code>1/sqrt(sumOfSquaredWeights). */ @Override public float queryNorm(float sumOfSquaredWeights) { return (float)(1.0 / Math.sqrt(sumOfSquaredWeights)); } /** Implemented as <code>sqrt(freq). */ @Override public float tf(float freq) { return (float)Math.sqrt(freq); } /** Implemented as <code>1 / (distance + 1). */ @Override public float sloppyFreq(int distance) { return 1.0f / (distance + 1); } /** Implemented as <code>log(numDocs/(docFreq+1)) + 1. */ @Override public float idf(int docFreq, int numDocs) { return (float)(Math.log(numDocs/(double)(docFreq+1)) + 1.0); } /** Implemented as <code>overlap / maxOverlap. */ @Override public float coord(int overlap, int maxOverlap) { return overlap / (float)maxOverlap; } // Default true protected boolean discountOverlaps = true; /** Determines whether overlap tokens (Tokens with * 0 position increment) are ignored when computing * norm. By default this is true, meaning overlap * tokens do not count when computing norms. * * @lucene.experimental * * @see #computeNorm */ public void setDiscountOverlaps(boolean v) { discountOverlaps = v; } /** @see #setDiscountOverlaps */ public boolean getDiscountOverlaps() { return discountOverlaps; } } Other Lucene examples (source code examples)Here is a short list of links related to this Lucene DefaultSimilarity.java source code file: 
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