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/*===============================================================================
 * Copyright (c) 2010-2012 University of Massachusetts.  All Rights Reserved.
 *
 * Use of the RankLib package is subject to the terms of the software license set
 * forth in the LICENSE file included with this software, and also available at
 * http://people.cs.umass.edu/~vdang/ranklib_license.html
 *===============================================================================
 */

package ciir.umass.edu.learning.neuralnet;

/**
 * @author vdang
 */
public class HyperTangentFunction implements TransferFunction {

    @Override
    public double compute(final double x) {
        return 1.7159 * Math.tanh(x * 2 / 3);
    }

    @Override
    public double computeDerivative(final double x) {
        final double output = Math.tanh(x * 2 / 3);
        return 1.7159 * (1.0 - output * output) * 2 / 3;
    }

}