| /* |
| * 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.misc.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>{@code b = 0.75} |
| * <li>{@code discountOverlaps = true} |
| * </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); |
| } |
| |
| /** |
| * 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. |
| * @param discountOverlaps True if overlap tokens (tokens with a position of increment of zero) |
| * are discounted from the document's length. |
| * @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, boolean discountOverlaps) { |
| this.bm25Similarity = new BM25Similarity(k1, b, discountOverlaps); |
| } |
| |
| @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(); |
| } |
| |
| /** |
| * Returns true if overlap tokens are discounted from the document's length. |
| * |
| * @see #LegacyBM25Similarity(float, float, boolean) |
| */ |
| public boolean getDiscountOverlaps() { |
| return bm25Similarity.getDiscountOverlaps(); |
| } |
| |
| @Override |
| public String toString() { |
| return bm25Similarity.toString(); |
| } |
| } |