FairSimilarity.java

/**   
 * License Agreement for Jaeksoft OpenSearchServer
 *
 * Copyright (C) 2008-2013 Emmanuel Keller / Jaeksoft
 * 
 * http://www.open-search-server.com
 * 
 * This file is part of Jaeksoft OpenSearchServer.
 *
 * Jaeksoft OpenSearchServer is free software: you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 * Jaeksoft OpenSearchServer is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with Jaeksoft OpenSearchServer. 
 *  If not, see <http://www.gnu.org/licenses/>.
 **/

package com.jaeksoft.searchlib.schema;

import org.apache.lucene.index.FieldInvertState;
import org.apache.lucene.search.DefaultSimilarity;

public class FairSimilarity extends DefaultSimilarity {

	private static final long serialVersionUID = -6126387002471023744L;

	@Override
	final public float computeNorm(String field, FieldInvertState state) {
		final int numTerms;
		if (discountOverlaps)
			numTerms = state.getLength() - state.getNumOverlap();
		else
			numTerms = state.getLength();
		return state.getBoost() * ((float) (1.0 / numTerms));
	}
}