SigmoidalKernel.java

  1. /*
  2.  * MIT License
  3.  *
  4.  * Copyright (c) 2009-2016 Ignacio Calderon <https://github.com/kronenthaler>
  5.  *
  6.  * Permission is hereby granted, free of charge, to any person obtaining a copy
  7.  * of this software and associated documentation files (the "Software"), to deal
  8.  * in the Software without restriction, including without limitation the rights
  9.  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  10.  * copies of the Software, and to permit persons to whom the Software is
  11.  * furnished to do so, subject to the following conditions:
  12.  *
  13.  * The above copyright notice and this permission notice shall be included in all
  14.  * copies or substantial portions of the Software.
  15.  *
  16.  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  17.  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  18.  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  19.  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  20.  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  21.  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  22.  * SOFTWARE.
  23.  */
  24. package libai.common.kernels;

  25. import libai.common.matrix.Matrix;

  26. /**
  27.  * Sigmoid Kernel. Follows the form: K(x,y) = tanh(a * xy + b), where a &amp; b are
  28.  * parameters of this kernel.
  29.  *
  30.  * @author kronenthaler
  31.  */
  32. public class SigmoidalKernel implements Kernel {

  33.     private static final long serialVersionUID = 5132845207274843125L;

  34.     private final double a;
  35.     private final double b;

  36.     public SigmoidalKernel(double a, double b) {
  37.         this.a = a;
  38.         this.b = b;
  39.     }

  40.     @Override
  41.     public double eval(Matrix A, Matrix B) {
  42.         double dotProduct = A.dotProduct(B);
  43.         return Math.tanh(a * dotProduct + b);
  44.     }
  45. }