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Apache Solr (module: core)
/*
* 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.AfterEffect;
import org.apache.lucene.search.similarities.AfterEffectB;
import org.apache.lucene.search.similarities.AfterEffectL;
import org.apache.lucene.search.similarities.BasicModel;
import org.apache.lucene.search.similarities.BasicModelG;
import org.apache.lucene.search.similarities.BasicModelIF;
import org.apache.lucene.search.similarities.BasicModelIn;
import org.apache.lucene.search.similarities.BasicModelIne;
import org.apache.lucene.search.similarities.DFRSimilarity;
import org.apache.lucene.search.similarities.Normalization;
import org.apache.lucene.search.similarities.Normalization.NoNormalization;
import org.apache.lucene.search.similarities.NormalizationH1;
import org.apache.lucene.search.similarities.NormalizationH2;
import org.apache.lucene.search.similarities.NormalizationH3;
import org.apache.lucene.search.similarities.NormalizationZ;
import org.apache.lucene.search.similarities.Similarity;
import org.apache.solr.common.params.SolrParams;
import org.apache.solr.schema.SimilarityFactory;
/**
* Factory for {@link DFRSimilarity}
*
* You must specify the implementations for all three components of DFR (strings). In general the
* models are parameter-free, but two of the normalizations take floating point parameters (see
* below):
*
*
* - {@link BasicModel basicModel}: Basic model of information content:
*
* - {@link BasicModelG G}: Geometric approximation of Bose-Einstein
*
- {@link BasicModelIn I(n)}: Inverse document frequency
*
- {@link BasicModelIne I(ne)}: Inverse expected document frequency [mixture of Poisson
* and IDF]
*
- {@link BasicModelIF I(F)}: Inverse term frequency [approximation of I(ne)]
*
* - {@link AfterEffect afterEffect}: First normalization of information gain:
*
* - {@link AfterEffectL L}: Laplace's law of succession
*
- {@link AfterEffectB B}: Ratio of two Bernoulli processes
*
* - {@link Normalization normalization}: Second (length) normalization:
*
* - {@link NormalizationH1 H1}: Uniform distribution of term frequency
*
* - parameter c (float): hyper-parameter that controls the term frequency
* normalization with respect to the document length. The default is
1
*
*
* - {@link NormalizationH2 H2}: term frequency density inversely related to length
*
* - parameter c (float): hyper-parameter that controls the term frequency
* normalization with respect to the document length. The default is
1
*
*
* - {@link NormalizationH3 H3}: term frequency normalization provided by Dirichlet prior
*
* - parameter mu (float): smoothing parameter μ. The default is
800
*
* - {@link NormalizationZ Z}: term frequency normalization provided by a Zipfian relation
*
* - parameter z (float): represents
A/(A+1)
where A measures the
* specificity of the language. The default is 0.3
*
* - {@link NoNormalization none}: no second normalization
*
*
*
* Optional settings:
*
*
* - discountOverlaps (bool): Sets {@link DFRSimilarity#setDiscountOverlaps(boolean)}
*
*
* @lucene.experimental
*/
public class DFRSimilarityFactory extends SimilarityFactory {
private boolean discountOverlaps;
private BasicModel basicModel;
private AfterEffect afterEffect;
private Normalization normalization;
@Override
public void init(SolrParams params) {
super.init(params);
discountOverlaps = params.getBool("discountOverlaps", true);
basicModel = parseBasicModel(params.get("basicModel"));
afterEffect = parseAfterEffect(params.get("afterEffect"));
normalization =
parseNormalization(
params.get("normalization"), params.get("c"), params.get("mu"), params.get("z"));
}
private BasicModel parseBasicModel(String expr) {
if ("G".equals(expr)) {
return new BasicModelG();
} else if ("I(F)".equals(expr)) {
return new BasicModelIF();
} else if ("I(n)".equals(expr)) {
return new BasicModelIn();
} else if ("I(ne)".equals(expr)) {
return new BasicModelIne();
} else {
throw new RuntimeException("Invalid basicModel: " + expr);
}
}
private AfterEffect parseAfterEffect(String expr) {
if ("B".equals(expr)) {
return new AfterEffectB();
} else if ("L".equals(expr)) {
return new AfterEffectL();
} else {
throw new RuntimeException("Invalid afterEffect: " + expr);
}
}
// also used by IBSimilarityFactory
static Normalization parseNormalization(String expr, String c, String mu, String z) {
if (mu != null && !"H3".equals(expr)) {
throw new RuntimeException("parameter mu only makes sense for normalization H3");
}
if (z != null && !"Z".equals(expr)) {
throw new RuntimeException("parameter z only makes sense for normalization Z");
}
if (c != null && !("H1".equals(expr) || "H2".equals(expr))) {
throw new RuntimeException("parameter c only makese sense for normalizations H1 and H2");
}
if ("H1".equals(expr)) {
return (c != null) ? new NormalizationH1(Float.parseFloat(c)) : new NormalizationH1();
} else if ("H2".equals(expr)) {
return (c != null) ? new NormalizationH2(Float.parseFloat(c)) : new NormalizationH2();
} else if ("H3".equals(expr)) {
return (mu != null) ? new NormalizationH3(Float.parseFloat(mu)) : new NormalizationH3();
} else if ("Z".equals(expr)) {
return (z != null) ? new NormalizationZ(Float.parseFloat(z)) : new NormalizationZ();
} else if ("none".equals(expr)) {
return new Normalization.NoNormalization();
} else {
throw new RuntimeException("Invalid normalization: " + expr);
}
}
@Override
public Similarity getSimilarity() {
DFRSimilarity sim = new DFRSimilarity(basicModel, afterEffect, normalization);
sim.setDiscountOverlaps(discountOverlaps);
return sim;
}
}