CosineDistance.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) 2008-2009 Christian Gehl
 * Copyright (C) 2008-2009 Fraunhofer Institute FIRST
 */

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

using namespace shogun;

CCosineDistance::CCosineDistance()
: CDenseDistance<float64_t>()
{
}

CCosineDistance::CCosineDistance(CDenseFeatures<float64_t>* l, CDenseFeatures<float64_t>* r)
: CDenseDistance<float64_t>()
{
    init(l, r);
}

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

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

void CCosineDistance::cleanup()
{
}

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

    float64_t* avec=
        ((CDenseFeatures<float64_t>*) lhs)->get_feature_vector(idx_a, alen, afree);
    float64_t* bvec=
        ((CDenseFeatures<float64_t>*) rhs)->get_feature_vector(idx_b, blen, bfree);

    ASSERT(alen==blen)
    float64_t s=0;
    float64_t ab=0;
    float64_t sa=0;
    float64_t sb=0;
    {
        for (int32_t i=0; i<alen; i++)
        {
            ab+=avec[i]*bvec[i];
            sa+=pow(fabs(avec[i]),2);
            sb+=pow(fabs(bvec[i]),2);
        }
    }

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

    s=sqrt(sa)*sqrt(sb);

    // trap division by zero
    if(s==0)
        return 0;

    s=1-ab/s;
    if(s<0)
        return 0;
    else
        return s ;
}