/usr/include/shogun/kernel/AvgDiagKernelNormalizer.h is in libshogun-dev 1.1.0-4ubuntu2.
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* 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 3 of the License, or
* (at your option) any later version.
*
* Written (W) 2009 Soeren Sonnenburg
* Copyright (C) 2009 Fraunhofer Institute FIRST and Max-Planck-Society
*/
#ifndef _AVGDIAGKERNELNORMALIZER_H___
#define _AVGDIAGKERNELNORMALIZER_H___
#include <shogun/kernel/KernelNormalizer.h>
namespace shogun
{
/** @brief Normalize the kernel by either a constant or the average value of the
* diagonal elements (depending on argument c of the constructor).
*
* In case c <= 0 compute scale as
* \f[
* \mbox{scale} = \frac{1}{N}\sum_{i=1}^N k(x_i,x_i)
* \f]
*
* otherwise use scale=c and normalize the kernel via
*
* \f[
* k'(x,x')= \frac{k(x,x')}{scale}
* \f]
*/
class CAvgDiagKernelNormalizer : public CKernelNormalizer
{
public:
/** constructor
*
* @param c scale parameter, if <= 0 scaling will be computed from the
* avg of the kernel diagonal elements
*/
CAvgDiagKernelNormalizer(float64_t c=0.0) : CKernelNormalizer()
{
scale=c;
m_parameters->add(&scale, "scale",
"Scale quotient by which kernel is scaled.");
}
/** default destructor */
virtual ~CAvgDiagKernelNormalizer()
{
}
/** initialization of the normalizer (if needed)
* @param k kernel */
virtual bool init(CKernel* k)
{
if (scale<=0)
{
ASSERT(k);
int32_t num=k->get_num_vec_lhs();
ASSERT(num>0);
CFeatures* old_lhs=k->lhs;
CFeatures* old_rhs=k->rhs;
k->lhs=old_lhs;
k->rhs=old_lhs;
float64_t sum=0;
for (int32_t i=0; i<num; i++)
sum+=k->compute(i, i);
scale=sum/num;
k->lhs=old_lhs;
k->rhs=old_rhs;
}
return true;
}
/** normalize the kernel value
* @param value kernel value
* @param idx_lhs index of left hand side vector
* @param idx_rhs index of right hand side vector
*/
inline virtual float64_t normalize(
float64_t value, int32_t idx_lhs, int32_t idx_rhs)
{
return value/scale;
}
/** normalize only the left hand side vector
* @param value value of a component of the left hand side feature vector
* @param idx_lhs index of left hand side vector
*/
inline virtual float64_t normalize_lhs(float64_t value, int32_t idx_lhs)
{
return value/sqrt(scale);
}
/** normalize only the right hand side vector
* @param value value of a component of the right hand side feature vector
* @param idx_rhs index of right hand side vector
*/
inline virtual float64_t normalize_rhs(float64_t value, int32_t idx_rhs)
{
return value/sqrt(scale);
}
/** @return object name */
inline virtual const char* get_name() const { return "AvgDiagKernelNormalizer"; }
protected:
/// the constant scaling factor (avg of diagonal or user given const)
float64_t scale;
};
}
#endif
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