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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) 2007 Christian Gehl
* Copyright (C) 1999-2008 Fraunhofer Institute FIRST and Max-Planck-Society
*/
#include "lib/config.h"
#ifndef _DISTANCEKERNEL_H___
#define _DISTANCEKERNEL_H___
#include "lib/common.h"
#include "kernel/Kernel.h"
#include "distance/Distance.h"
/** The Distance kernel takes a distance as input and computes
*
* \f[
* k({\bf x}, {\bf x'}) = e^{-\frac{dist({\bf x}, {\bf x'})}{width}}
* \f]
*/
class CDistanceKernel: public CKernel
{
public:
/** constructor
*
* @param cache cache size
* @param width width
* @param dist distance
*/
CDistanceKernel(INT cache, DREAL width, CDistance* dist);
/** constructor
*
* @param l features of left-hand side
* @param r features of right-hand side
* @param width width
* @param dist distance
*/
CDistanceKernel(CFeatures *l, CFeatures *r, DREAL width, CDistance* dist);
virtual ~CDistanceKernel();
/** 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);
/** return what type of kernel we are
*
* @return kernel type DISTANCE
*/
inline virtual EKernelType get_kernel_type() { return K_DISTANCE; }
/** return feature type the kernel can deal with
*
* @return feature type of distance used
*/
inline virtual EFeatureType get_feature_type() { return distance->get_feature_type(); }
/** return feature class the kernel can deal with
*
* @return feature class of distance used
*/
inline virtual EFeatureClass get_feature_class() { return distance->get_feature_class(); }
/** return the kernel's name
*
* @return name Distance
*/
inline virtual const CHAR* get_name() { return distance->get_name(); }
/** load kernel init_data
*
* @param src file to load from
* @return if loading was successful
*/
bool load_init(FILE* src);
/** save kernel init_data
*
* @param dest file to save to
* @return if saving was successful
*/
bool save_init(FILE* dest);
protected:
/** compute kernel function for features a and b
* idx_{a,b} denote the index of the feature vectors
* in the corresponding feature object
*
* @param idx_a index a
* @param idx_b index b
* @return computed kernel function at indices a,b
*/
DREAL compute(INT idx_a, INT idx_b);
private:
/** distance */
CDistance* distance;
/** width */
DREAL width;
};
#endif /* _DISTANCEKERNEL_H__ */
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