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ShiftInvariantKernel.h
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ShiftInvariantKernel.h
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/*
* Copyright (c) The Shogun Machine Learning Toolbox
* Written (w) 2016 Soumyajit De
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice, this
* list of conditions and the following disclaimer.
* 2. 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.
*
* 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.
*
* The views and conclusions contained in the software and documentation are those
* of the authors and should not be interpreted as representing official policies,
* either expressed or implied, of the Shogun Development Team.
*/
#include <shogun/lib/config.h>
#ifndef SHIFT_INVARIANT_KERNEL_H_
#define SHIFT_INVARIANT_KERNEL_H_
#include <shogun/kernel/Kernel.h>
#include <shogun/distance/CustomDistance.h>
namespace shogun
{
/** @brief Base class for the family of kernel functions that only depend on
* the difference of the inputs, i.e. whose values does not change if the
* inputs are shifted by the same amount. More precisely,
* \f[
* k(\mathbf{x}, \mathbf{x'}) = k(\mathbf{x-x'})
* \f]
* For example, Gaussian (RBF) kernel is a shfit invariant kernel.
*/
class CShiftInvariantKernel: public CKernel
{
public:
/** Default constructor. */
CShiftInvariantKernel();
/**
* Constructor that initializes the kernel with two feature instances.
*
* @param l features of left-hand side
* @param r features of right-hand side
*/
CShiftInvariantKernel(CFeatures *l, CFeatures *r);
/** Destructor. */
virtual ~CShiftInvariantKernel();
/**
* Initialize kernel.
*
* @param l features of left-hand side
* @param r features of right-hand side
* @return if initializing was successful
*/
virtual bool init(CFeatures* l, CFeatures* r);
/** Method that precomputes the distance */
virtual void precompute_distance();
/**
* Method that releases any precomputed distance instance in addition to
* clean up the base class methods.
*/
virtual void cleanup();
/** @return kernel type */
virtual EKernelType get_kernel_type()=0;
/** @return feature type of distance used */
virtual EFeatureType get_feature_type()=0;
/** @return feature class of distance used */
virtual EFeatureClass get_feature_class()=0;
/** @return the distance type */
virtual EDistanceType get_distance_type() const;
/** @return name Distance */
virtual const char* get_name() const
{
return "ShiftInvariantKernel";
}
protected:
/**
* Computes distance between features a and b, where idx_{a,b} denote the indices
* of the feature vectors in the corresponding feature object.
*
* @param idx_a index a
* @param idx_b index b
* @return distance between features a and b
*/
virtual float64_t distance(int32_t idx_a, int32_t idx_b) const;
/** Distance instance for the kernel. MUST be initialized by the subclasses */
CDistance* m_distance;
private:
/** Registers the parameters (serialization support). */
virtual void register_params();
/** Precomputed distance instance */
CCustomDistance* m_precomputed_distance;
/**
* Method that sets a precomputed distance.
*
* @param precomputed_distance The precomputed distance object.
*/
void set_precomputed_distance(CCustomDistance* precomputed_distance);
/** @return the precomputed distance. */
CCustomDistance* get_precomputed_distance() const;
};
}
#endif // SHIFT_INVARIANT_KERNEL_H__