LinearStringKernel.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/io/SGIO.h>
#include <shogun/mathematics/Math.h>
#include <shogun/kernel/string/LinearStringKernel.h>
#include <shogun/features/StringFeatures.h>

using namespace shogun;

CLinearStringKernel::CLinearStringKernel()
: CStringKernel<char>(0), normal(NULL)
{
}

CLinearStringKernel::CLinearStringKernel(
    CStringFeatures<char>* l, CStringFeatures<char>* r)
: CStringKernel<char>(0), normal(NULL)
{
    init(l, r);
}

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

bool CLinearStringKernel::init(CFeatures *l, CFeatures *r)
{
    CStringKernel<char>::init(l, r);
    return init_normalizer();
}

void CLinearStringKernel::cleanup()
{
    delete_optimization();

    CKernel::cleanup();
}

void CLinearStringKernel::clear_normal()
{
    memset(normal, 0, lhs->get_num_vectors()*sizeof(float64_t));
}

void CLinearStringKernel::add_to_normal(int32_t idx, float64_t weight)
{
    int32_t vlen;
    bool vfree;
    char* vec = ((CStringFeatures<char>*) lhs)->get_feature_vector(idx, vlen, vfree);

    for (int32_t i=0; i<vlen; i++)
        normal[i] += weight*normalizer->normalize_lhs(vec[i], idx);

    ((CStringFeatures<char>*) lhs)->free_feature_vector(vec, idx, vfree);
}

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

    char* avec = ((CStringFeatures<char>*) lhs)->get_feature_vector(idx_a, alen, free_avec);
    char* bvec = ((CStringFeatures<char>*) rhs)->get_feature_vector(idx_b, blen, free_bvec);
    ASSERT(alen==blen)
    float64_t result=CMath::dot(avec, bvec, alen);
    ((CStringFeatures<char>*) lhs)->free_feature_vector(avec, idx_a, free_avec);
    ((CStringFeatures<char>*) rhs)->free_feature_vector(bvec, idx_b, free_bvec);
    return result;
}

bool CLinearStringKernel::init_optimization(
    int32_t num_suppvec, int32_t *sv_idx, float64_t *alphas)
{
    int32_t num_feat = ((CStringFeatures<char>*) lhs)->get_max_vector_length();
    ASSERT(num_feat)

    normal = SG_MALLOC(float64_t, num_feat);
    ASSERT(normal)
    clear_normal();

    for (int32_t i = 0; i<num_suppvec; i++)
    {
        int32_t alen;
        bool free_avec;
        char *avec = ((CStringFeatures<char>*) lhs)->get_feature_vector(sv_idx[i], alen, free_avec);
        ASSERT(avec)

        for (int32_t j = 0; j<num_feat; j++)
        {
            normal[j] += alphas[i]*
                normalizer->normalize_lhs(((float64_t) avec[j]), sv_idx[i]);
        }
        ((CStringFeatures<char>*) lhs)->free_feature_vector(avec, sv_idx[i], free_avec);
    }
    set_is_initialized(true);
    return true;
}

bool CLinearStringKernel::delete_optimization()
{
    SG_FREE(normal);
    normal = NULL;
    set_is_initialized(false);
    return true;
}

float64_t CLinearStringKernel::compute_optimized(int32_t idx_b)
{
    int32_t blen;
    bool free_bvec;
    char* bvec = ((CStringFeatures<char>*) rhs)->get_feature_vector(idx_b, blen, free_bvec);
    float64_t result=normalizer->normalize_rhs(CMath::dot(normal, bvec, blen), idx_b);
    ((CStringFeatures<char>*) rhs)->free_feature_vector(bvec, idx_b, free_bvec);
    return result;
}