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<FONT color="green">001</FONT> /*<a name="line.1"></a>
<FONT color="green">002</FONT> * JNI_SVM-light - A Java Native Interface for SVM-light<a name="line.2"></a>
<FONT color="green">003</FONT> * <a name="line.3"></a>
<FONT color="green">004</FONT> * Copyright (C) 2005 <a name="line.4"></a>
<FONT color="green">005</FONT> * Tom Crecelius & Martin Theobald <a name="line.5"></a>
<FONT color="green">006</FONT> * Max-Planck Institute for Computer Science<a name="line.6"></a>
<FONT color="green">007</FONT> * <a name="line.7"></a>
<FONT color="green">008</FONT> * This program is free software; you can redistribute it and/or modify it under<a name="line.8"></a>
<FONT color="green">009</FONT> * the terms of the GNU General Public License as published by the Free Software<a name="line.9"></a>
<FONT color="green">010</FONT> * Foundation.<a name="line.10"></a>
<FONT color="green">011</FONT> * <a name="line.11"></a>
<FONT color="green">012</FONT> * This program is distributed in the hope that it will be useful, but WITHOUT<a name="line.12"></a>
<FONT color="green">013</FONT> * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS<a name="line.13"></a>
<FONT color="green">014</FONT> * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more<a name="line.14"></a>
<FONT color="green">015</FONT> * details.<a name="line.15"></a>
<FONT color="green">016</FONT> * <a name="line.16"></a>
<FONT color="green">017</FONT> * You should have received a copy of the GNU General Public License along with<a name="line.17"></a>
<FONT color="green">018</FONT> * this program; if not, write to the Free Software Foundation, Inc., 51<a name="line.18"></a>
<FONT color="green">019</FONT> * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA<a name="line.19"></a>
<FONT color="green">020</FONT> */<a name="line.20"></a>
<FONT color="green">021</FONT> <a name="line.21"></a>
<FONT color="green">022</FONT> package jnisvmlight;<a name="line.22"></a>
<FONT color="green">023</FONT> <a name="line.23"></a>
<FONT color="green">024</FONT> /**<a name="line.24"></a>
<FONT color="green">025</FONT> * A kernel with sigmoid smoothing.<a name="line.25"></a>
<FONT color="green">026</FONT> * <a name="line.26"></a>
<FONT color="green">027</FONT> * @author Tom Crecelius & Martin Theobald<a name="line.27"></a>
<FONT color="green">028</FONT> */<a name="line.28"></a>
<FONT color="green">029</FONT> public class SigmoidKernel extends ExtendedKernel {<a name="line.29"></a>
<FONT color="green">030</FONT> <a name="line.30"></a>
<FONT color="green">031</FONT> protected SigmoidKernel() {<a name="line.31"></a>
<FONT color="green">032</FONT> super(new LinearKernel(), 1.0, 0.0);<a name="line.32"></a>
<FONT color="green">033</FONT> }<a name="line.33"></a>
<FONT color="green">034</FONT> <a name="line.34"></a>
<FONT color="green">035</FONT> public SigmoidKernel(Kernel nestedKernel, double a, double c) {<a name="line.35"></a>
<FONT color="green">036</FONT> super(nestedKernel, a, c);<a name="line.36"></a>
<FONT color="green">037</FONT> }<a name="line.37"></a>
<FONT color="green">038</FONT> <a name="line.38"></a>
<FONT color="green">039</FONT> public double evaluate(FeatureVector v1, FeatureVector v2) {<a name="line.39"></a>
<FONT color="green">040</FONT> return tanh(m_a * m_kernel.evaluate(v1, v2) + m_c);<a name="line.40"></a>
<FONT color="green">041</FONT> }<a name="line.41"></a>
<FONT color="green">042</FONT> <a name="line.42"></a>
<FONT color="green">043</FONT> private double tanh(double a) {<a name="line.43"></a>
<FONT color="green">044</FONT> double x = Math.exp(a);<a name="line.44"></a>
<FONT color="green">045</FONT> double y = Math.exp(-a);<a name="line.45"></a>
<FONT color="green">046</FONT> return (x - y) / (x + y);<a name="line.46"></a>
<FONT color="green">047</FONT> }<a name="line.47"></a>
<FONT color="green">048</FONT> <a name="line.48"></a>
<FONT color="green">049</FONT> public String toString() {<a name="line.49"></a>
<FONT color="green">050</FONT> return "Sigmoid kernel K(x, k) = tanh(" + m_a + ".k(x) + " + m_c + ")"<a name="line.50"></a>
<FONT color="green">051</FONT> + ". k = " + m_kernel.toString();<a name="line.51"></a>
<FONT color="green">052</FONT> }<a name="line.52"></a>
<FONT color="green">053</FONT> }<a name="line.53"></a>
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