LinearARDKernel.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.
 *
 * (W) 2012 Jacob Walker
 *
 * Adapted from WeightedDegreeRBFKernel.cpp
 *
 */

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

using namespace shogun;

CLinearARDKernel::CLinearARDKernel()
: CDotKernel()
{
    init();
}


CLinearARDKernel::CLinearARDKernel(int32_t size)
: CDotKernel(size)
{
    init();
}

CLinearARDKernel::CLinearARDKernel(CDenseFeatures<float64_t>* l,
        CDenseFeatures<float64_t>* r,
        int32_t size)
: CDotKernel(size)
{
    init();
    init(l,r);
}

void CLinearARDKernel::init()
{
    m_weights = SGVector<float64_t>();
    SG_ADD(&m_weights, "weights", "Feature Weights", MS_AVAILABLE);
}

CLinearARDKernel::~CLinearARDKernel()
{
    CKernel::cleanup();
}

bool CLinearARDKernel::init(CFeatures* l, CFeatures* r)
{
    CDotKernel::init(l, r);

    init_ft_weights();

    return init_normalizer();
}

void CLinearARDKernel::init_ft_weights()
{
    if (!lhs || !rhs)
        return;

    int32_t alen, blen;

    alen = ((CDenseFeatures<float64_t>*) lhs)->get_num_features();
    blen = ((CDenseFeatures<float64_t>*) rhs)->get_num_features();

    REQUIRE(alen==blen, "Number of Right and Left Hand "\
            "Features Must be the Same./n");

    if (m_weights.vlen != alen)
    {
        m_weights = SGVector<float64_t>(alen);

        for (int32_t i=0; i < alen; i++)
            m_weights[i]=1.0;
    }

    SG_DEBUG("Initialized weights for LinearARDKernel (%p).\n", this);

}

void CLinearARDKernel::set_weight(float64_t w, index_t i)
{
    if (i >= m_weights.vlen)
    {
        SG_ERROR("Index %i out of range for LinearARDKernel."\
                 "Number of features is %i.\n", i, m_weights.vlen);
    }

    m_weights[i]=w;
}

float64_t CLinearARDKernel::get_weight(index_t i)
{
    if (i >= m_weights.vlen)
    {
        SG_ERROR("Index %i out of range for LinearARDKernel."\
                 "Number of features is %i.\n", i, m_weights.vlen);
    }

    return m_weights[i];
}

float64_t CLinearARDKernel::compute(int32_t idx_a, int32_t idx_b)
{
    if (!lhs || !rhs)
        SG_ERROR("Features not set!\n");

    SGVector<float64_t> avec
        = ((CDenseFeatures<float64_t>*) lhs)->get_feature_vector(idx_a);
    SGVector<float64_t> bvec
        = ((CDenseFeatures<float64_t>*) rhs)->get_feature_vector(idx_b);

    REQUIRE(avec.vlen==bvec.vlen, "Number of Right and Left Hand "\
            "Features Must be the Same./n");

    float64_t result=0;

    for (index_t i = 0; i < avec.vlen; i++)
        result += avec[i]*bvec[i]*m_weights[i]*m_weights[i];

    return result;
}

SGMatrix<float64_t> CLinearARDKernel::get_parameter_gradient(TParameter* param,
        CSGObject* obj, index_t index)
{
    if (!lhs || !rhs)
        SG_ERROR("Features not set!\n");

    if (!strcmp(param->m_name, "weights") && obj == this)
    {
        SGMatrix<float64_t> derivative(num_lhs, num_rhs);

        for (index_t j = 0; j < num_lhs; j++)
        {
            for (index_t k = 0; k < num_rhs; k++)
            {
                SGVector<float64_t> avec
                    = ((CDenseFeatures<float64_t>*) lhs)->get_feature_vector(j);
                SGVector<float64_t> bvec
                    = ((CDenseFeatures<float64_t>*) rhs)->get_feature_vector(k);

                REQUIRE(avec.vlen==bvec.vlen, "Number of Right and Left Hand "\
                        "Features Must be the Same./n");

                derivative(j,k) = avec[index]*bvec[index]*m_weights[index];
            }
        }
        return derivative;
    }

    else
        return SGMatrix<float64_t>();
}