/*
* This program 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 2 of the License, or
* (at your option) any later version.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* L1.java
* Copyright (C) 2004 Mikhail Bilenko and Sugato Basu
*
*/
package weka.clusterers.regularizers;
import java.io.Serializable;
/**
* L1-norm regularization of metric weights
*
* @author Mikhail Bilenko (mbilenko@cs.utexas.edu) and Sugato Basu
* (sugato@cs.utexas.edu)
* @version $Revision: 1.1 $ */
public class L1 extends Regularizer {
/** Compute the regularizer value for given weights */
public double computeRegularizer(double[] weights) {
double val = 0;
for (int i = 0; i < weights.length; i++) {
if (weights[i] != 0) {
val -= 1/Math.abs(weights[i]);
} else {
val = -Double.MAX_VALUE;
break;
}
}
return val;
}
/** Compute the gradient of regularizer wrt to given weight */
public double gradient(double weight) {
if (weight != 0) {
return -1.0 / (weight * weight);
} else {
return 0;
}
}
}