PowerKernel.cpp

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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) 2011 Jakub Jirku
 * Copyright (C) 2007-2011 Fraunhofer Institute FIRST and Max-Planck-Society
 */

#include <shogun/kernel/PowerKernel.h>
#include <shogun/mathematics/Math.h>

using namespace shogun;

CPowerKernel::CPowerKernel(): CKernel(0), distance(NULL), m_degree(1.8)
{
    init();
}

CPowerKernel::CPowerKernel(int32_t cache, float64_t degree, CDistance* dist)
: CKernel(cache), distance(dist), m_degree(degree)
{
    init();
    ASSERT(distance);
    SG_REF(distance);
}

CPowerKernel::CPowerKernel(CFeatures *l, CFeatures *r, float64_t degree, CDistance* dist)
: CKernel(10), distance(dist), m_degree(degree)
{
    init();
    ASSERT(distance);
    SG_REF(distance);
    init(l, r);
}

CPowerKernel::~CPowerKernel()
{
    cleanup();
    SG_UNREF(distance);
}

bool CPowerKernel::init(CFeatures* l, CFeatures* r)
{
    ASSERT(distance);
    CKernel::init(l,r);
    distance->init(l,r);
    return init_normalizer();
}

void CPowerKernel::init()
{
    SG_ADD(&m_degree, "degree", "Degree kernel parameter.", MS_AVAILABLE);
    SG_ADD((CSGObject**) &distance, "distance", "Distance to be used.",
            MS_AVAILABLE);
}

float64_t CPowerKernel::compute(int32_t idx_a, int32_t idx_b)
{
    float64_t dist = distance->distance(idx_a, idx_b);  
    float64_t temp = pow(dist, m_degree);
    return -temp;
}