GaussianKernel.h

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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) 1999-2010 Soeren Sonnenburg
 * Written (W) 2011 Abhinav Maurya
 * Written (W) 2012 Heiko Strathmann
 * Copyright (C) 1999-2009 Fraunhofer Institute FIRST and Max-Planck-Society
 * Copyright (C) 2010 Berlin Institute of Technology
 */

#ifndef _GAUSSIANKERNEL_H___
#define _GAUSSIANKERNEL_H___

#include <shogun/lib/common.h>
#include <shogun/kernel/Kernel.h>
#include <shogun/kernel/DotKernel.h>
#include <shogun/features/DotFeatures.h>

namespace shogun
{
    class CDotFeatures;
class CGaussianKernel: public CDotKernel
{
    public:
        CGaussianKernel();

        CGaussianKernel(int32_t size, float64_t width);

        CGaussianKernel(CDotFeatures* l, CDotFeatures* r,
            float64_t width, int32_t size=10);

        virtual ~CGaussianKernel();

        static CGaussianKernel* obtain_from_generic(CKernel* kernel);

        virtual CSGObject *shallow_copy() const;

        virtual bool init(CFeatures* l, CFeatures* r);

        virtual void cleanup();

        virtual EKernelType get_kernel_type() { return K_GAUSSIAN; }

        virtual const char* get_name() const { return "GaussianKernel"; }

        virtual void set_width(float64_t w)
        {
            width=w;
        }

        virtual float64_t get_width() const
        {
            return width;
        }

        inline void set_compact_enabled(bool compact)
        {
            m_compact = compact;
        }

        inline bool get_compact_enabled()
        {
            return m_compact;
        }
        
        virtual SGMatrix<float64_t> get_parameter_gradient(TParameter* param,
                CSGObject* obj, index_t index = -1);


    protected:
        virtual float64_t compute(int32_t idx_a, int32_t idx_b);

        virtual void load_serializable_post() throw (ShogunException);

    private:
        void precompute_squared();

        void precompute_squared_helper(float64_t* &buf, CDotFeatures* df);

        void init();

    protected:
        float64_t width;
        float64_t* sq_lhs;
        float64_t* sq_rhs;
        bool m_compact;
};
}
#endif /* _GAUSSIANKERNEL_H__ */