org.apache.lucene.search.similarities.Axiomatic Maven / Gradle / Ivy
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package org.apache.lucene.search.similarities;
import java.util.List;
import org.apache.lucene.search.Explanation;
/**
* Axiomatic approaches for IR. From Hui Fang and Chengxiang Zhai
* 2005. An Exploration of Axiomatic Approaches to Information Retrieval.
* In Proceedings of the 28th annual international ACM SIGIR
* conference on Research and development in information retrieval
* (SIGIR '05). ACM, New York, NY, USA, 480-487.
*
* There are a family of models. All of them are based on BM25,
* Pivoted Document Length Normalization and Language model with
* Dirichlet prior. Some components (e.g. Term Frequency,
* Inverted Document Frequency) in the original models are modified
* so that they follow some axiomatic constraints.
*
*
* @lucene.experimental
*/
public abstract class Axiomatic extends SimilarityBase {
/**
* hyperparam for the growth function
*/
protected final float s;
/**
* hyperparam for the primitive weighthing function
*/
protected final float k;
/**
* the query length
*/
protected final int queryLen;
/**
* Constructor setting all Axiomatic hyperparameters
* @param s hyperparam for the growth function
* @param queryLen the query length
* @param k hyperparam for the primitive weighting function
*/
public Axiomatic(float s, int queryLen, float k) {
if (Float.isFinite(s) == false || Float.isNaN(s) || s < 0 || s > 1) {
throw new IllegalArgumentException("illegal s value: " + s + ", must be between 0 and 1");
}
if (Float.isFinite(k) == false || Float.isNaN(k) || k < 0 || k > 1) {
throw new IllegalArgumentException("illegal k value: " + k + ", must be between 0 and 1");
}
if (queryLen < 0 || queryLen > Integer.MAX_VALUE) {
throw new IllegalArgumentException("illegal query length value: "
+ queryLen + ", must be larger 0 and smaller than MAX_INT");
}
this.s = s;
this.queryLen = queryLen;
this.k = k;
}
/**
* Constructor setting only s, letting k and queryLen to default
* @param s hyperparam for the growth function
*/
public Axiomatic(float s) {
this(s, 1, 0.35f);
}
/**
* Constructor setting s and queryLen, letting k to default
* @param s hyperparam for the growth function
* @param queryLen the query length
*/
public Axiomatic(float s, int queryLen) {
this(s, queryLen, 0.35f);
}
/**
* Default constructor
*/
public Axiomatic() {
this(0.25f, 1, 0.35f);
}
@Override
public float score(BasicStats stats, float freq, float docLen) {
return tf(stats, freq, docLen)
* ln(stats, freq, docLen)
* tfln(stats, freq, docLen)
* idf(stats, freq, docLen)
- gamma(stats, freq, docLen);
}
@Override
protected void explain(List subs, BasicStats stats, int doc,
float freq, float docLen) {
if (stats.getBoost() != 1.0f) {
subs.add(Explanation.match(stats.getBoost(), "boost"));
}
subs.add(Explanation.match(this.k, "k"));
subs.add(Explanation.match(this.s, "s"));
subs.add(Explanation.match(this.queryLen, "queryLen"));
subs.add(Explanation.match(tf(stats, freq, docLen), "tf"));
subs.add(Explanation.match(ln(stats, freq, docLen), "ln"));
subs.add(Explanation.match(tfln(stats, freq, docLen), "tfln"));
subs.add(Explanation.match(idf(stats, freq, docLen), "idf"));
subs.add(Explanation.match(gamma(stats, freq, docLen), "gamma"));
super.explain(subs, stats, doc, freq, docLen);
}
/**
* Name of the axiomatic method.
*/
@Override
public abstract String toString();
/**
* compute the term frequency component
*/
protected abstract float tf(BasicStats stats, float freq, float docLen);
/**
* compute the document length component
*/
protected abstract float ln(BasicStats stats, float freq, float docLen);
/**
* compute the mixed term frequency and document length component
*/
protected abstract float tfln(BasicStats stats, float freq, float docLen);
/**
* compute the inverted document frequency component
*/
protected abstract float idf(BasicStats stats, float freq, float docLen);
/**
* compute the gamma component (only for F3EXp and F3LOG)
*/
protected abstract float gamma(BasicStats stats, float freq, float docLen);
}