JensenMetric.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) 2006-2009 Christian Gehl
 * Copyright (C) 2006-2009 Fraunhofer Institute FIRST
 */

#include <shogun/lib/config.h>
#include <shogun/lib/common.h>
#include <shogun/io/SGIO.h>
#include <shogun/distance/JensenMetric.h>
#include <shogun/features/Features.h>
#include <shogun/features/SimpleFeatures.h>

using namespace shogun;

CJensenMetric::CJensenMetric() : CSimpleDistance<float64_t>()
{
}

CJensenMetric::CJensenMetric(CSimpleFeatures<float64_t>* l, CSimpleFeatures<float64_t>* r)
: CSimpleDistance<float64_t>()
{
    init(l, r);
}

CJensenMetric::~CJensenMetric()
{
    cleanup();
}

bool CJensenMetric::init(CFeatures* l, CFeatures* r)
{
    return CSimpleDistance<float64_t>::init(l,r);
}

void CJensenMetric::cleanup()
{
}

float64_t CJensenMetric::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);

    float64_t absTmp = 0;
    float64_t result=0;
    {
        for (int32_t i=0; i<alen; i++)
        {
            absTmp=0.5*(avec[i]+bvec[i]);
            if (absTmp>0)
            {
                if(avec[i]>0)
                    result+=avec[i]*log(avec[i]/absTmp);
                if(bvec[i]>0)
                    result+=bvec[i]*log(bvec[i]/absTmp);
            }
        }

    }

    ((CSimpleFeatures<float64_t>*) lhs)->free_feature_vector(avec, idx_a, afree);
    ((CSimpleFeatures<float64_t>*) rhs)->free_feature_vector(bvec, idx_b, bfree);


    return result;
}