CanberraWordDistance.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) Christian Gehl
 * Written (W) 1999-2009 Soeren Sonnenburg
 * Copyright (C) 1999-2009 Fraunhofer Institute FIRST and Max-Planck-Society
 */

#include <shogun/lib/common.h>
#include <shogun/distance/CanberraWordDistance.h>
#include <shogun/features/Features.h>
#include <shogun/features/StringFeatures.h>
#include <shogun/io/SGIO.h>

using namespace shogun;

CCanberraWordDistance::CCanberraWordDistance()
: CStringDistance<uint16_t>()
{
    SG_DEBUG("CCanberraWordDistance created")
}

CCanberraWordDistance::CCanberraWordDistance(
    CStringFeatures<uint16_t>* l, CStringFeatures<uint16_t>* r)
: CStringDistance<uint16_t>()
{
    SG_DEBUG("CCanberraWordDistance created")

    init(l, r);
}

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

bool CCanberraWordDistance::init(CFeatures* l, CFeatures* r)
{
    return CStringDistance<uint16_t>::init(l,r);
}

void CCanberraWordDistance::cleanup()
{
}

float64_t CCanberraWordDistance::compute(int32_t idx_a, int32_t idx_b)
{
    int32_t alen, blen;
    bool free_avec, free_bvec;

    uint16_t* avec=((CStringFeatures<uint16_t>*) lhs)->
        get_feature_vector(idx_a, alen, free_avec);
    uint16_t* bvec=((CStringFeatures<uint16_t>*) rhs)->
        get_feature_vector(idx_b, blen, free_bvec);

    float64_t result=0;

    int32_t left_idx=0;
    int32_t right_idx=0;

    while (left_idx < alen && right_idx < blen)
    {
        uint16_t sym=avec[left_idx];
        if (avec[left_idx]==bvec[right_idx])
        {
            int32_t old_left_idx=left_idx;
            int32_t old_right_idx=right_idx;

            while (left_idx< alen && avec[left_idx]==sym)
                left_idx++;

            while (right_idx< blen && bvec[right_idx]==sym)
                right_idx++;

            result +=
                CMath::abs((float64_t)
                    ((left_idx-old_left_idx)-(right_idx-old_right_idx)))/
                ((float64_t)
                    ((left_idx-old_left_idx) + (right_idx-old_right_idx)));
        }
        else if (avec[left_idx]<bvec[right_idx])
        {
            result++;

            while (left_idx< alen && avec[left_idx]==sym)
                left_idx++;
        }
        else
        {
            sym=bvec[right_idx];
            result++;

            while (right_idx< blen && bvec[right_idx]==sym)
                right_idx++;
        }
    }

    while (left_idx < alen)
    {
        uint16_t sym=avec[left_idx];
        result++;

        while (left_idx< alen && avec[left_idx]==sym)
            left_idx++;
    }

    while (right_idx < blen)
    {
        uint16_t sym=bvec[right_idx];
        result++;

        while (right_idx< blen && bvec[right_idx]==sym)
            right_idx++;
    }
    ((CStringFeatures<uint16_t>*) lhs)->
        free_feature_vector(avec, idx_a, free_avec);
    ((CStringFeatures<uint16_t>*) rhs)->
        free_feature_vector(bvec, idx_b, free_bvec);

    return result;
}