/* * 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. */ package org.apache.lucene.search.similarity; import org.apache.lucene.index.FieldInvertState; import org.apache.lucene.search.CollectionStatistics; import org.apache.lucene.search.TermStatistics; import org.apache.lucene.search.similarities.BM25Similarity; import org.apache.lucene.search.similarities.Similarity; /** * Similarity that behaves like {@link BM25Similarity} while also applying * the k1+1 factor to the numerator of the scoring formula * * @see BM25Similarity * * @deprecated {@link BM25Similarity} should be used instead */ @Deprecated public final class LegacyBM25Similarity extends Similarity { private final BM25Similarity bm25Similarity; /** BM25 with these default values: * <ul> * <li>{@code k1 = 1.2}</li> * <li>{@code b = 0.75}</li> * </ul> */ public LegacyBM25Similarity() { this.bm25Similarity = new BM25Similarity(); } /** * BM25 with the supplied parameter values. * @param k1 Controls non-linear term frequency normalization (saturation). * @param b Controls to what degree document length normalizes tf values. * @throws IllegalArgumentException if {@code k1} is infinite or negative, or if {@code b} is * not within the range {@code [0..1]} */ public LegacyBM25Similarity(float k1, float b) { this.bm25Similarity = new BM25Similarity(k1, b); } @Override public long computeNorm(FieldInvertState state) { return bm25Similarity.computeNorm(state); } @Override public SimScorer scorer(float boost, CollectionStatistics collectionStats, TermStatistics... termStats) { return bm25Similarity.scorer(boost * (1 + bm25Similarity.getK1()), collectionStats, termStats); } /** * Returns the <code>k1</code> parameter * @see #LegacyBM25Similarity(float, float) */ public final float getK1() { return bm25Similarity.getK1(); } /** * Returns the <code>b</code> parameter * @see #LegacyBM25Similarity(float, float) */ public final float getB() { return bm25Similarity.getB(); } /** Sets 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. */ public void setDiscountOverlaps(boolean v) { bm25Similarity.setDiscountOverlaps(v); } /** * Returns true if overlap tokens are discounted from the document's length. * @see #setDiscountOverlaps */ public boolean getDiscountOverlaps() { return bm25Similarity.getDiscountOverlaps(); } @Override public String toString() { return bm25Similarity.toString(); } }