kernels.cpp

Go to the documentation of this file.

/*********************************************************************
 * Software License Agreement (BSD License)
 *
 *  Copyright (c) 2013, Georgia Institute of Technology
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions
 *  are met:
 *
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above
 *     copyright notice, this list of conditions and the following
 *     disclaimer in the documentation and/or other materials provided
 *     with the distribution.
 *   * Neither the name of the Georgia Institute of Technology nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 *  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 *  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 *  FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 *  COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 *  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 *  BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 *  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 *  CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 *  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 *  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 *********************************************************************/

#include <cpl_visual_features/features/kernels.h>
#include <math.h>

namespace cpl_visual_features
{

double chiSqaureKernel(std::vector<double> x, std::vector<double> y)
{
  double kernel_sum = 0.0;
  for (unsigned int i = 0; i < x.size(); ++i)
  {
    double numerator = x[i]-y[i];
    double a_plus_b = x[i]+y[i];
    if (a_plus_b > 0.0)
    {
      kernel_sum += (numerator*numerator)/a_plus_b;
    }
  }
  return kernel_sum;
}

std::vector<std::vector<double> > chiSquareKernelBatch(std::vector<std::vector<double> >& X,
                                                       std::vector<std::vector<double> >& Y, double gamma)
{
  std::vector<std::vector<double> > K;

  // Compute chi-square elementwise
  for (int i = 0; i < X.size(); ++i)
  {
    std::vector<double> x = X[i];
    std::vector<double> row;
    K.push_back(row);
    for (int j = 0; j < Y.size(); ++j)
    {
      std::vector<double> y = Y[j];
      K[i].push_back(cpl_visual_features::chiSqaureKernel(x, y));
    }
  }
  if (gamma > 0.0)
  {
    for (int i = 0; i < K.size(); ++i)
    {
      for (int j = 0; j < K[i].size(); ++j)
      {
        K[i][j] = exp(-gamma*K[i][j]);
      }
    }
  }
  return K;
}

};