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package it.unimi.di.law.vector;

/*		 
 * Copyright (C) 2008-2013 Paolo Boldi, Massimo Santini and Sebastiano Vigna 
 *
 *  This library is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU Lesser General Public License as published by the Free
 *  Software Foundation; either version 3 of the License, or (at your option)
 *  any later version.
 *
 *  This library 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 Lesser General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, see .
 *
 */

//RELEASE-STATUS: DIST

/** A class that compute the similarity between pattern using cosine similarity. */
public class CosineSimilarityStrategy implements SimilarityStrategy {
	
	static final long serialVersionUID = 2006001L;

	public double similarity(Vector v0, Vector v1) {
		double dot = v0.dotProduct( v1 );
		return dot == 0.0 ? 0.0 : dot / ( v0.ell2Norm() * v1.ell2Norm() );
	}

}