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/*
 * 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.solr.search.similarities;

import org.apache.lucene.search.similarities.DFISimilarity;
import org.apache.lucene.search.similarities.Independence;
import org.apache.lucene.search.similarities.IndependenceChiSquared;
import org.apache.lucene.search.similarities.IndependenceSaturated;
import org.apache.lucene.search.similarities.IndependenceStandardized;
import org.apache.lucene.search.similarities.Similarity;
import org.apache.solr.common.params.SolrParams;
import org.apache.solr.schema.SimilarityFactory;

/**
 * Factory for {@link DFISimilarity}
 * 

* You must specify the measure of divergence from independence ("independenceMeasure") *

    *
  • "Standardized": {@link IndependenceStandardized}
  • *
  • "Saturated": {@link IndependenceSaturated}
  • *
  • "ChiSquared": {@link IndependenceChiSquared}
  • *
* Optional settings: *
    *
  • discountOverlaps (bool): Sets {@link org.apache.lucene.search.similarities.SimilarityBase#setDiscountOverlaps(boolean)}
  • *
* * @lucene.experimental */ public class DFISimilarityFactory extends SimilarityFactory { private boolean discountOverlaps; private Independence independenceMeasure; @Override public void init(SolrParams params) { super.init(params); discountOverlaps = params.getBool(ClassicSimilarityFactory.DISCOUNT_OVERLAPS, true); independenceMeasure = parseIndependenceMeasure(params.get("independenceMeasure")); } @Override public Similarity getSimilarity() { DFISimilarity sim = new DFISimilarity(independenceMeasure); sim.setDiscountOverlaps(discountOverlaps); return sim; } private Independence parseIndependenceMeasure(String expr) { if ("ChiSquared".equals(expr)) { return new IndependenceChiSquared(); } else if ("Standardized".equals(expr)) { return new IndependenceStandardized(); } else if ("Saturated".equals(expr)) { return new IndependenceSaturated(); } else { throw new RuntimeException("Invalid independence measure: " + expr); } } }




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