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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.AfterEffect;
import org.apache.lucene.search.similarities.AfterEffect.NoAfterEffect; // javadoc
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.BasicModelBE;
import org.apache.lucene.search.similarities.BasicModelD;
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.BasicModelP;
import org.apache.lucene.search.similarities.DFRSimilarity;
import org.apache.lucene.search.similarities.Normalization;
import org.apache.lucene.search.similarities.Normalization.NoNormalization; // javadoc
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}
* <p>
* 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):
* <ol>
* <li>{@link BasicModel basicModel}: Basic model of information content:
* <ul>
* <li>{@link BasicModelBE Be}: Limiting form of Bose-Einstein
* <li>{@link BasicModelG G}: Geometric approximation of Bose-Einstein
* <li>{@link BasicModelP P}: Poisson approximation of the Binomial
* <li>{@link BasicModelD D}: Divergence approximation of the Binomial
* <li>{@link BasicModelIn I(n)}: Inverse document frequency
* <li>{@link BasicModelIne I(ne)}: Inverse expected document
* frequency [mixture of Poisson and IDF]
* <li>{@link BasicModelIF I(F)}: Inverse term frequency
* [approximation of I(ne)]
* </ul>
* <li>{@link AfterEffect afterEffect}: First normalization of information
* gain:
* <ul>
* <li>{@link AfterEffectL L}: Laplace's law of succession
* <li>{@link AfterEffectB B}: Ratio of two Bernoulli processes
* <li>{@link NoAfterEffect none}: no first normalization
* </ul>
* <li>{@link Normalization normalization}: Second (length) normalization:
* <ul>
* <li>{@link NormalizationH1 H1}: Uniform distribution of term
* frequency
* <ul>
* <li>parameter c (float): hyper-parameter that controls
* the term frequency normalization with respect to the
* document length. The default is <code>1</code>
* </ul>
* <li>{@link NormalizationH2 H2}: term frequency density inversely
* related to length
* <ul>
* <li>parameter c (float): hyper-parameter that controls
* the term frequency normalization with respect to the
* document length. The default is <code>1</code>
* </ul>
* <li>{@link NormalizationH3 H3}: term frequency normalization
* provided by Dirichlet prior
* <ul>
* <li>parameter mu (float): smoothing parameter μ. The
* default is <code>800</code>
* </ul>
* <li>{@link NormalizationZ Z}: term frequency normalization provided
* by a Zipfian relation
* <ul>
* <li>parameter z (float): represents <code>A/(A+1)</code>
* where A measures the specificity of the language.
* The default is <code>0.3</code>
* </ul>
* <li>{@link NoNormalization none}: no second normalization
* </ul>
* </ol>
* <p>
* Optional settings:
* <ul>
* <li>discountOverlaps (bool): Sets
* {@link DFRSimilarity#setDiscountOverlaps(boolean)}</li>
* </ul>
* @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 ("Be".equals(expr)) {
return new BasicModelBE();
} else if ("D".equals(expr)) {
return new BasicModelD();
} else 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 if ("P".equals(expr)) {
return new BasicModelP();
} 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 if ("none".equals(expr)) {
return new AfterEffect.NoAfterEffect();
} 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;
}
}