DisjunctionSumScorer.java

package experiments.collective.entdoccentric.LTR;

/*
 * 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.
 */

import java.util.List;
import java.io.IOException;

import org.apache.lucene.search.Scorer;
import org.apache.lucene.search.Weight;

/**
 * A Scorer for OR like queries, counterpart of <code>ConjunctionScorer</code>.
 * This Scorer implements {@link Scorer#advance(int)} and uses advance() on the
 * given Scorers.
 */
class DisjunctionSumScorer extends DisjunctionScorer {
	/** The minimum number of scorers that should match. */
	private final int minimumNrMatchers;

	/** The document number of the current match. */
	private int doc = -1;

	/** The number of subscorers that provide the current match. */
	protected int nrMatchers = -1;

	private double score = Float.NaN;

	private final int docBase;

	private final LearnToRankClause[] clauses;

	/**
	 * Construct a <code>DisjunctionScorer</code>.
	 * 
	 * @param weight
	 *            The weight to be used.
	 * @param subScorers
	 *            A collection of at least two subscorers.
	 * @param minimumNrMatchers
	 *            The positive minimum number of subscorers that should match to
	 *            match this query. <br>
	 *            When <code>minimumNrMatchers</code> is bigger than the number
	 *            of <code>subScorers</code>, no matches will be produced. <br>
	 *            When minimumNrMatchers equals the number of subScorers, it
	 *            more efficient to use <code>ConjunctionScorer</code>.
	 */
	public DisjunctionSumScorer(Weight weight, List<Scorer> subScorers,
			int minimumNrMatchers, LearnToRankClause[] learnToRankWeights,
			int docBase) throws IOException {
		super(weight, subScorers.toArray(new Scorer[subScorers.size()]), learnToRankWeights,
				subScorers.size());

		if (minimumNrMatchers <= 0) {
			throw new IllegalArgumentException(
					"Minimum nr of matchers must be positive");
		}
		if (numScorers <= 1) {
			throw new IllegalArgumentException(
					"There must be at least 2 subScorers");
		}
		this.clauses = learnToRankWeights;
		this.minimumNrMatchers = minimumNrMatchers;
		this.docBase = docBase;
	}

	/**
	 * Construct a <code>DisjunctionScorer</code>, using one as the minimum
	 * number of matching subscorers.
	 */
	public DisjunctionSumScorer(Weight weight, List<Scorer> subScorers,
			LearnToRankClause[] learnToRankWeights, int docBase)
			throws IOException {
		this(weight, subScorers, 1, learnToRankWeights, docBase);
	}

	@Override
	public int nextDoc() throws IOException {
		assert doc != NO_MORE_DOCS;
		while (true) {
			while (subScorers[0].docID() == doc) {
				if (subScorers[0].nextDoc() != NO_MORE_DOCS) {
					heapAdjust(0);
				} else {
					heapRemoveRoot();
					if (numScorers < minimumNrMatchers) {
						return doc = NO_MORE_DOCS;
					}
				}
			}
			afterNext();
			if (nrMatchers >= minimumNrMatchers) {
				break;
			}
		}

		return doc;
	}

	private void afterNext() throws IOException {
		final Scorer sub = subScorers[0];
		doc = sub.docID();
		if (doc == NO_MORE_DOCS) {
			nrMatchers = Integer.MAX_VALUE; // stop looping
		} else {
			score = sub.score() * clauses[0].getWeight();
			clauses[0].addFeatureValue(docBase, doc, (float) score);
			nrMatchers = 1;
			countMatches(1);
			countMatches(2);
		}
	}

	// TODO: this currently scores, but so did the previous impl
	// TODO: remove recursion.
	// TODO: if we separate scoring, out of here, modify this
	// and afterNext() to terminate when nrMatchers == minimumNrMatchers
	// then also change freq() to just always compute it from scratch
	private void countMatches(int root) throws IOException {
		if (root < numScorers && subScorers[root].docID() == doc) {
			nrMatchers++;
			float val = subScorers[root].score() * clauses[root].getWeight();
//			if(root == 5) {
//				System.out.println("first"+doc);
//				System.out.println(subScorers[root].toString()+ " " +subScorers[root].score());
//			}
			score += val;
			clauses[root].addFeatureValue(docBase, doc, val);
			countMatches((root << 1) + 1);
			countMatches((root << 1) + 2);
		}
	}

	/**
	 * Returns the score of the current document matching the query. Initially
	 * invalid, until {@link #nextDoc()} is called the first time.
	 */
	@Override
	public float score() throws IOException {
		return (float) score;
	}

	@Override
	public int docID() {
		return doc;
	}

	@Override
	public int freq() throws IOException {
		return nrMatchers;
	}

	/**
	 * Advances to the first match beyond the current whose document number is
	 * greater than or equal to a given target. <br>
	 * The implementation uses the advance() method on the subscorers.
	 * 
	 * @param target
	 *            The target document number.
	 * @return the document whose number is greater than or equal to the given
	 *         target, or -1 if none exist.
	 */
	@Override
	public int advance(int target) throws IOException {
		if (numScorers == 0)
			return doc = NO_MORE_DOCS;
		while (subScorers[0].docID() < target) {
			if (subScorers[0].advance(target) != NO_MORE_DOCS) {
				heapAdjust(0);
			} else {
				heapRemoveRoot();
				if (numScorers == 0) {
					return doc = NO_MORE_DOCS;
				}
			}
		}

		afterNext();

		if (nrMatchers >= minimumNrMatchers) {
			return doc;
		} else {
			return nextDoc();
		}
	}
}