// Copyright (C) 2007 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_SVm_KERNEL
#define DLIB_SVm_KERNEL
#include "kernel_abstract.h"
#include <cmath>
#include <limits>
#include <sstream>
#include "../matrix.h"
#include "../algs.h"
#include "../serialize.h"
namespace dlib
{
// ----------------------------------------------------------------------------------------
template < typename kernel_type > struct kernel_derivative;
// ----------------------------------------------------------------------------------------
template <
typename T
>
struct radial_basis_kernel
{
typedef typename T::type scalar_type;
typedef T sample_type;
typedef typename T::mem_manager_type mem_manager_type;
// T must be capable of representing a column vector.
COMPILE_TIME_ASSERT(T::NC == 1 || T::NC == 0);
radial_basis_kernel(const scalar_type g) : gamma(g) {}
radial_basis_kernel() : gamma(0.1) {}
radial_basis_kernel(
const radial_basis_kernel& k
) : gamma(k.gamma) {}
const scalar_type gamma;
scalar_type operator() (
const sample_type& a,
const sample_type& b
) const
{
const scalar_type d = trans(a-b)*(a-b);
return std::exp(-gamma*d);
}
radial_basis_kernel& operator= (
const radial_basis_kernel& k
)
{
const_cast<scalar_type&>(gamma) = k.gamma;
return *this;
}
bool operator== (
const radial_basis_kernel& k
) const
{
return gamma == k.gamma;
}
};
template <
typename T
>
void serialize (
const radial_basis_kernel<T>& item,
std::ostream& out
)
{
try
{
serialize(item.gamma, out);
}
catch (serialization_error& e)
{
throw serialization_error(e.info + "\n while serializing object of type radial_basis_kernel");
}
}
template <
typename T
>
void deserialize (
radial_basis_kernel<T>& item,
std::istream& in
)
{
typedef typename T::type scalar_type;
try
{
deserialize(const_cast<scalar_type&>(item.gamma), in);
}
catch (serialization_error& e)
{
throw serialization_error(e.info + "\n while deserializing object of type radial_basis_kernel");
}
}
template <
typename T
>
struct kernel_derivative<radial_basis_kernel<T> >
{
typedef typename T::type scalar_type;
typedef T sample_type;
typedef typename T::mem_manager_type mem_manager_type;
kernel_derivative(const radial_basis_kernel<T>& k_) : k(k_){}
const sample_type& operator() (const sample_type& x, const sample_type& y) const
{
// return the derivative of the rbf kernel
temp = 2*k.gamma*(x-y)*k(x,y);
return temp;
}
const radial_basis_kernel<T>& k;
mutable sample_type temp;
};
// ----------------------------------------------------------------------------------------
template <
typename T
>
struct polynomial_kernel
{
typedef typename T::type scalar_type;
typedef T sample_type;
typedef typename T::mem_manager_type mem_manager_type;
// T must be capable of representing a column vector.
COMPILE_TIME_ASSERT(T::NC == 1 || T::NC == 0);
polynomial_kernel(const scalar_type g, const scalar_type c, const scalar_type d) : gamma(g), coef(c), degree(d) {}
polynomial_kernel() : gamma(1), coef(0), degree(1) {}
polynomial_kernel(
const polynomial_kernel& k
) : gamma(k.gamma), coef(k.coef), degree(k.degree) {}
typedef T type;
const scalar_type gamma;
const scalar_type coef;
const scalar_type degree;
scalar_type operator() (
const sample_type& a,
const sample_type& b
) const
{
return std::pow(gamma*(trans(a)*b) + coef, degree);
}
polynomial_kernel& operator= (
const polynomial_kernel& k
)
{
const_cast<scalar_type&>(gamma) = k.gamma;
const_cast<scalar_type&>(coef) = k.coef;
const_cast<scalar_type&>(degree) = k.degree;
return *this;
}
bool operator== (
const polynomial_kernel& k
) const
{
return (gamma == k.gamma) && (coef == k.coef) && (degree == k.degree);
}
};
template <
typename T
>
void serialize (
const polynomial_kernel<T>& item,
std::ostream& out
)
{
try
{
serialize(item.gamma, out);
serialize(item.coef, out);
serialize(item.degree, out);
}
catch (serialization_error& e)
{
throw serialization_error(e.info + "\n while serializing object of type polynomial_kernel");
}
}
template <
typename T
>
void deserialize (
polynomial_kernel<T>& item,
std::istream& in
)
{
typedef typename T::type scalar_type;
try
{
deserialize(const_cast<scalar_type&>(item.gamma), in);
deserialize(const_cast<scalar_type&>(item.coef), in);
deserialize(const_cast<scalar_type&>(item.degree), in);
}
catch (serialization_error& e)
{
throw serialization_error(e.info + "\n while deserializing object of type polynomial_kernel");
}
}
template <
typename T
>
struct kernel_derivative<polynomial_kernel<T> >
{
typedef typename T::type scalar_type;
typedef T sample_type;
typedef typename T::mem_manager_type mem_manager_type;
kernel_derivative(const polynomial_kernel<T>& k_) : k(k_){}
const sample_type& operator() (const sample_type& x, const sample_type& y) const
{
// return the derivative of the rbf kernel
temp = k.degree*k.gamma*x*std::pow(k.gamma*(trans(x)*y) + k.coef, k.degree-1);
return temp;
}
const polynomial_kernel<T>& k;
mutable sample_type temp;
};
// ----------------------------------------------------------------------------------------
template <
typename T
>
struct sigmoid_kernel
{
typedef typename T::type scalar_type;
typedef T sample_type;
typedef typename T::mem_manager_type mem_manager_type;
// T must be capable of representing a column vector.
COMPILE_TIME_ASSERT(T::NC == 1 || T::NC == 0);
sigmoid_kernel(const scalar_type g, const scalar_type c) : gamma(g), coef(c) {}
sigmoid_kernel() : gamma(0.1), coef(-1.0) {}
sigmoid_kernel(
const sigmoid_kernel& k
) : gamma(k.gamma), coef(k.coef) {}
typedef T type;
const scalar_type gamma;
const scalar_type coef;
scalar_type operator() (
const sample_type& a,
const sample_type& b
) const
{
return std::tanh(gamma*(trans(a)*b) + coef);
}
sigmoid_kernel& operator= (
const sigmoid_kernel& k
)
{
const_cast<scalar_type&>(gamma) = k.gamma;
const_cast<scalar_type&>(coef) = k.coef;
return *this;
}
bool operator== (
const sigmoid_kernel& k
) const
{
return (gamma == k.gamma) && (coef == k.coef);
}
};
template <
typename T
>
void serialize (
const sigmoid_kernel<T>& item,
std::ostream& out
)
{
try
{
serialize(item.gamma, out);
serialize(item.coef, out);
}
catch (serialization_error& e)
{
throw serialization_error(e.info + "\n while serializing object of type sigmoid_kernel");
}
}
template <
typename T
>
void deserialize (
sigmoid_kernel<T>& item,
std::istream& in
)
{
typedef typename T::type scalar_type;
try
{
deserialize(const_cast<scalar_type&>(item.gamma), in);
deserialize(const_cast<scalar_type&>(item.coef), in);
}
catch (serialization_error& e)
{
throw serialization_error(e.info + "\n while deserializing object of type sigmoid_kernel");
}
}
template <
typename T
>
struct kernel_derivative<sigmoid_kernel<T> >
{
typedef typename T::type scalar_type;
typedef T sample_type;
typedef typename T::mem_manager_type mem_manager_type;
kernel_derivative(const sigmoid_kernel<T>& k_) : k(k_){}
const sample_type& operator() (const sample_type& x, const sample_type& y) const
{
// return the derivative of the rbf kernel
temp = k.gamma*x*(1-std::pow(k(x,y),2));
return temp;
}
const sigmoid_kernel<T>& k;
mutable sample_type temp;
};
// ----------------------------------------------------------------------------------------
template <typename T>
struct linear_kernel
{
typedef typename T::type scalar_type;
typedef T sample_type;
typedef typename T::mem_manager_type mem_manager_type;
// T must be capable of representing a column vector.
COMPILE_TIME_ASSERT(T::NC == 1 || T::NC == 0);
scalar_type operator() (
const sample_type& a,
const sample_type& b
) const
{
return trans(a)*b;
}
bool operator== (
const linear_kernel&
) const
{
return true;
}
};
template <
typename T
>
void serialize (
const linear_kernel<T>& ,
std::ostream&
){}
template <
typename T
>
void deserialize (
linear_kernel<T>& ,
std::istream&
){}
template <
typename T
>
struct kernel_derivative<linear_kernel<T> >
{
typedef typename T::type scalar_type;
typedef T sample_type;
typedef typename T::mem_manager_type mem_manager_type;
kernel_derivative(const linear_kernel<T>& k_) : k(k_){}
const sample_type& operator() (const sample_type& x, const sample_type& ) const
{
return x;
}
const linear_kernel<T>& k;
};
// ----------------------------------------------------------------------------------------
template <typename T>
struct histogram_intersection_kernel
{
typedef typename T::type scalar_type;
typedef T sample_type;
typedef typename T::mem_manager_type mem_manager_type;
scalar_type operator() (
const sample_type& a,
const sample_type& b
) const
{
scalar_type temp = 0;
for (long i = 0; i < a.size(); ++i)
{
temp += std::min(a(i), b(i));
}
return temp;
}
bool operator== (
const histogram_intersection_kernel&
) const
{
return true;
}
};
template <
typename T
>
void serialize (
const histogram_intersection_kernel<T>& ,
std::ostream&
){}
template <
typename T
>
void deserialize (
histogram_intersection_kernel<T>& ,
std::istream&
){}
// ----------------------------------------------------------------------------------------
template <typename T>
struct offset_kernel
{
typedef typename T::scalar_type scalar_type;
typedef typename T::sample_type sample_type;
typedef typename T::mem_manager_type mem_manager_type;
offset_kernel(const T& k, const scalar_type& offset_
) : kernel(k), offset(offset_) {}
offset_kernel() : kernel(T()), offset(0.01) {}
offset_kernel(
const offset_kernel& k
) : kernel(k.kernel), offset(k.offset) {}
const T kernel;
const scalar_type offset;
scalar_type operator() (
const sample_type& a,
const sample_type& b
) const
{
return kernel(a,b) + offset;
}
offset_kernel& operator= (
const offset_kernel& k
)
{
const_cast<T&>(kernel) = k.kernel;
const_cast<scalar_type&>(offset) = k.offset;
return *this;
}
bool operator== (
const offset_kernel& k
) const
{
return k.kernel == kernel && offset == k.offset;
}
};
template <
typename T
>
void serialize (
const offset_kernel<T>& item,
std::ostream& out
)
{
try
{
serialize(item.offset, out);
serialize(item.kernel, out);
}
catch (serialization_error& e)
{
throw serialization_error(e.info + "\n while serializing object of type offset_kernel");
}
}
template <
typename T
>
void deserialize (
offset_kernel<T>& item,
std::istream& in
)
{
typedef typename offset_kernel<T>::scalar_type scalar_type;
try
{
deserialize(const_cast<scalar_type&>(item.offset), in);
deserialize(const_cast<T&>(item.kernel), in);
}
catch (serialization_error& e)
{
throw serialization_error(e.info + "\n while deserializing object of type offset_kernel");
}
}
template <
typename T
>
struct kernel_derivative<offset_kernel<T> >
{
typedef typename T::scalar_type scalar_type;
typedef typename T::sample_type sample_type;
typedef typename T::mem_manager_type mem_manager_type;
kernel_derivative(const offset_kernel<T>& k) : der(k.kernel){}
const sample_type operator() (const sample_type& x, const sample_type& y) const
{
return der(x,y);
}
kernel_derivative<T> der;
};
// ----------------------------------------------------------------------------------------
}
#endif // DLIB_SVm_KERNEL