NullReranker.java

/* 
 * Copyright (C) 2015 Information Retrieval Group at Universidad Autónoma
 * de Madrid, http://ir.ii.uam.es
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */
package es.uam.eps.ir.ranksys.novdiv.reranking;

import es.uam.eps.ir.ranksys.core.Recommendation;

import static java.lang.Math.min;

/**
 * Null re-ranker that does not perform an actual re-ranking.
 *
 * @author Saúl Vargas (saul.vargas@uam.es)
 * 
 * @param <U> type of the users
 * @param <I> type of the items
 */
public class NullReranker<U, I> extends PermutationReranker<U, I> {

    /**
     * Returns the permutation that is applied to the input recommendation
     * to generate the re-ranked recommendation.
     *
     * @param recommendation input recommendation
     * @param maxLength maximum length of the permutation
     * @return permutation that encodes the re-ranking
     */
    @Override
    public int[] rerankPermutation(Recommendation<U, I> recommendation, int maxLength) {
        return getBasePerm(min(maxLength, recommendation.getItems().size()));
    }

}