FirstElementKernelNormalizer.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) 2008-2009 Soeren Sonnenburg
 * Copyright (C) 2008-2009 Fraunhofer Institute FIRST and Max-Planck-Society
 */

#ifndef _FIRSTELEMENTKERNELNORMALIZER_H___
#define _FIRSTELEMENTKERNELNORMALIZER_H___

#include <shogun/lib/config.h>

#include <shogun/kernel/normalizer/KernelNormalizer.h>

namespace shogun
{
class CFirstElementKernelNormalizer : public CKernelNormalizer
{
    public:
        CFirstElementKernelNormalizer() : CKernelNormalizer(), scale(1.0)
        {
            SG_ADD(&scale, "scale", "Scale quotient by which kernel is scaled.",
                MS_AVAILABLE);
        }

        virtual ~CFirstElementKernelNormalizer()
        {
        }

        virtual bool init(CKernel* k)
        {
            CFeatures* old_lhs=k->lhs;
            CFeatures* old_rhs=k->rhs;
            k->lhs=old_lhs;
            k->rhs=old_lhs;

            scale=k->compute(0, 0);

            k->lhs=old_lhs;
            k->rhs=old_rhs;

            return true;
        }

        virtual float64_t normalize(
            float64_t value, int32_t idx_lhs, int32_t idx_rhs)
        {
            return value/scale;
        }

        virtual float64_t normalize_lhs(float64_t value, int32_t idx_lhs)
        {
            return value/sqrt(scale);
        }

        virtual float64_t normalize_rhs(float64_t value, int32_t idx_rhs)
        {
            return value/sqrt(scale);
        }

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

    protected:
        float64_t scale;
};
}
#endif