WeightedDegreeRBFKernel.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) 1999-2009 Soeren Sonnenburg
 * Copyright (C) 1999-2009 Fraunhofer Institute FIRST and Max-Planck-Society
 */

#include <shogun/lib/common.h>
#include <shogun/kernel/WeightedDegreeRBFKernel.h>
#include <shogun/features/Features.h>
#include <shogun/features/SimpleFeatures.h>
#include <shogun/io/SGIO.h>

using namespace shogun;

CWeightedDegreeRBFKernel::CWeightedDegreeRBFKernel()
: CDotKernel(), width(1), degree(1), weights(0)
{
}


CWeightedDegreeRBFKernel::CWeightedDegreeRBFKernel(int32_t size, float64_t w, int32_t d, int32_t nof_prop)
: CDotKernel(size), width(w), degree(d), nof_properties(nof_prop), weights(0)
{
    init_wd_weights();
}

CWeightedDegreeRBFKernel::CWeightedDegreeRBFKernel(
    CSimpleFeatures<float64_t>* l, CSimpleFeatures<float64_t>* r, float64_t w, int32_t d, int32_t nof_prop, int32_t size)
: CDotKernel(size), width(w), degree(d), nof_properties(nof_prop), weights(0)
{
    init_wd_weights();
    init(l,r);
}

CWeightedDegreeRBFKernel::~CWeightedDegreeRBFKernel()
{
    SG_FREE(weights);
    weights=NULL;
}

bool CWeightedDegreeRBFKernel::init(CFeatures* l, CFeatures* r)
{
    CDotKernel::init(l, r);
    SG_DEBUG("Initialized WeightedDegreeRBFKernel (%p).\n", this);
    return init_normalizer();
}

bool CWeightedDegreeRBFKernel::init_wd_weights()
{
    ASSERT(degree>0);

    if (weights!=0) SG_FREE(weights);
    weights=SG_MALLOC(float64_t, degree);
    if (weights)
    {
        int32_t i;
        float64_t sum=0;
        for (i=0; i<degree; i++)
        {
            weights[i]=degree-i;
            sum+=weights[i];
        }
        for (i=0; i<degree; i++)
            weights[i]/=sum;

        SG_DEBUG("Initialized weights for WeightedDegreeRBFKernel (%p).\n", this);
        return true;
    }
    else
        return false;
}


float64_t CWeightedDegreeRBFKernel::compute(int32_t idx_a, int32_t idx_b)
{
    int32_t alen, blen;
    bool afree, bfree;

    float64_t* avec=((CSimpleFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
    float64_t* bvec=((CSimpleFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);
    ASSERT(alen==blen);
    ASSERT(alen%nof_properties == 0);

    float64_t result=0;

    for (int32_t i=0; i<alen; i+=nof_properties)
    {
        float64_t resulti = 0.0;

        for (int32_t d=0; (i+(d*nof_properties)<alen) && (d<degree); d++)
        {
            float64_t resultid = 0.0;
            int32_t limit = (d + 1 ) * nof_properties;
            for (int32_t k=0; k < limit; k++)
            {
                resultid+=CMath::sq(avec[i+k]-bvec[i+k]);
            }
            
            resulti += weights[d] * exp(-resultid/width);
        }
    
        result+=resulti ;
    }

    return result;
}