ImplicitWeightedSpecFeatures.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) 2009 Soeren Sonnenburg
 * Copyright (C) 2009 Fraunhofer Institute FIRST and Max-Planck-Society
 */

#include "features/ImplicitWeightedSpecFeatures.h"
#include "lib/io.h"

using namespace shogun;

CImplicitWeightedSpecFeatures::CImplicitWeightedSpecFeatures(CStringFeatures<uint16_t>* str, bool normalize) : CDotFeatures()
{
    ASSERT(str);
    strings=str;
    SG_REF(strings)
    normalization_factors=NULL;
    spec_weights=NULL;
    num_strings = str->get_num_vectors();
    alphabet_size = str->get_original_num_symbols();
    degree=str->get_order();
    set_wd_weights();

    SG_DEBUG("WEIGHTED SPEC alphasz=%d, size=%d, num_str=%d\n", alphabet_size,
            spec_size, num_strings);

    if (normalize)
        compute_normalization_const();
}

void CImplicitWeightedSpecFeatures::compute_normalization_const()
{
    float64_t* factors=new float64_t[num_strings];

    for (int32_t i=0; i<num_strings; i++)
        factors[i]=1.0/CMath::sqrt(dot(i,i));

    normalization_factors=factors;
    //CMath::display_vector(normalization_factors, num_strings, "n");
}

bool CImplicitWeightedSpecFeatures::set_wd_weights()
{
    delete[] spec_weights;
    spec_weights=new float64_t[degree];

    int32_t i;
    float64_t sum=0;
    spec_size=0;

    for (i=0; i<degree; i++)
    {
        spec_size+=CMath::pow(alphabet_size, i+1);
        spec_weights[i]=degree-i;
        sum+=spec_weights[i];
    }
    for (i=0; i<degree; i++)
        spec_weights[i]=CMath::sqrt(spec_weights[i]/sum);

    return spec_weights!=NULL;
}

bool CImplicitWeightedSpecFeatures::set_weights(float64_t* w, int32_t d)
{
    ASSERT(d==degree);

    delete[] spec_weights;
    spec_weights=new float64_t[degree];
    for (int32_t i=0; i<degree; i++)
        spec_weights[i]=CMath::sqrt(w[i]);
    return true;
}

CImplicitWeightedSpecFeatures::CImplicitWeightedSpecFeatures(const CImplicitWeightedSpecFeatures& orig) : CDotFeatures(orig), 
    num_strings(orig.num_strings), 
    alphabet_size(orig.alphabet_size), spec_size(orig.spec_size)
{
    SG_NOTIMPLEMENTED;
    SG_REF(strings);
}

CImplicitWeightedSpecFeatures::~CImplicitWeightedSpecFeatures()
{
    SG_UNREF(strings);
    delete[] spec_weights;
    delete[] normalization_factors;
}

float64_t CImplicitWeightedSpecFeatures::dot(int32_t vec_idx1, int32_t vec_idx2)
{
    ASSERT(vec_idx1 < num_strings);
    ASSERT(vec_idx2 < num_strings);

    int32_t len1=-1;
    int32_t len2=-1;
    bool free_vec1;
    bool free_vec2;
    uint16_t* vec1=strings->get_feature_vector(vec_idx1, len1, free_vec1);
    uint16_t* vec2=strings->get_feature_vector(vec_idx2, len2, free_vec2);

    float64_t result=0;
    uint8_t mask=0;

    for (int32_t d=0; d<degree; d++)
    {
        mask = mask | (1 << (degree-d-1));
        uint16_t masked=strings->get_masked_symbols(0xffff, mask);

        int32_t left_idx=0;
        int32_t right_idx=0;
        float64_t weight=spec_weights[d]*spec_weights[d];

        while (left_idx < len1 && right_idx < len2)
        {
            uint16_t lsym=vec1[left_idx] & masked;
            uint16_t rsym=vec2[right_idx] & masked;

            if (lsym == rsym)
            {
                int32_t old_left_idx=left_idx;
                int32_t old_right_idx=right_idx;

                while (left_idx<len1 && (vec1[left_idx] & masked) ==lsym)
                    left_idx++;

                while (right_idx<len2 && (vec2[right_idx] & masked) ==lsym)
                    right_idx++;

                result+=weight*(left_idx-old_left_idx)*(right_idx-old_right_idx);
            }
            else if (lsym<rsym)
                left_idx++;
            else
                right_idx++;
        }
    }

    strings->free_feature_vector(vec1, vec_idx1, free_vec1);
    strings->free_feature_vector(vec2, vec_idx2, free_vec2);

    if (normalization_factors)
        return result*normalization_factors[vec_idx1]*normalization_factors[vec_idx2];
    else
        return result;
}

float64_t CImplicitWeightedSpecFeatures::dense_dot(int32_t vec_idx1, float64_t* vec2, int32_t vec2_len)
{
    ASSERT(vec2_len == spec_size);
    ASSERT(vec_idx1 < num_strings);

    float64_t result=0;
    int32_t len1=-1;
    bool free_vec1;
    uint16_t* vec1=strings->get_feature_vector(vec_idx1, len1, free_vec1);

    if (vec1 && len1>0)
    {
        for (int32_t j=0; j<len1; j++)
        {
            uint8_t mask=0;
            int32_t offs=0;
            uint16_t v=*vec1++;

            for (int32_t d=0; d<degree; d++)
            {
                mask = mask | (1 << (degree-d-1));
                int32_t idx=strings->get_masked_symbols(v, mask);
                idx=strings->shift_symbol(idx, degree-d-1);
                result += vec2[offs + idx]*spec_weights[d];
                offs+=strings->shift_offset(1,d+1);
            }
        }

        strings->free_feature_vector(vec1, vec_idx1, free_vec1);

        if (normalization_factors)
            result*=normalization_factors[vec_idx1];
    }
    else
        SG_ERROR("huh?\n");

    return result;
}

void CImplicitWeightedSpecFeatures::add_to_dense_vec(float64_t alpha, int32_t vec_idx1, float64_t* vec2, int32_t vec2_len, bool abs_val)
{
    int32_t len1=-1;
    bool free_vec1;
    uint16_t* vec=strings->get_feature_vector(vec_idx1, len1, free_vec1);

    if (normalization_factors)
        alpha*=normalization_factors[vec_idx1];

    if (vec && len1>0)
    {
        for (int32_t j=0; j<len1; j++)
        {
            uint8_t mask=0;
            int32_t offs=0;
            for (int32_t d=0; d<degree; d++)
            {
                mask = mask | (1 << (degree-d-1));
                int32_t idx=strings->get_masked_symbols(vec[j], mask);
                idx=strings->shift_symbol(idx, degree-d-1);
                if (abs_val)
                    vec2[offs + idx] += CMath::abs(alpha*spec_weights[d]);
                else
                    vec2[offs + idx] += alpha*spec_weights[d];
                offs+=strings->shift_offset(1,d+1);
            }
        }
    }

    strings->free_feature_vector(vec, vec_idx1, free_vec1);
}

CFeatures* CImplicitWeightedSpecFeatures::duplicate() const
{
    return new CImplicitWeightedSpecFeatures(*this);
}

void* CImplicitWeightedSpecFeatures::get_feature_iterator(int32_t vector_index)
{
    if (vector_index>=num_strings)
    {
        SG_ERROR("Index out of bounds (number of strings %d, you "
                "requested %d)\n", num_strings, vector_index);
    }

    wspec_feature_iterator* it=new wspec_feature_iterator[1];
    it->vec= strings->get_feature_vector(vector_index, it->vlen, it->vfree);
    it->vidx=vector_index;

    it->offs=0;
    it->d=0;
    it->j=0;
    it->mask=0;
    it->alpha=normalization_factors[vector_index];

    return it;
}

bool CImplicitWeightedSpecFeatures::get_next_feature(int32_t& index, float64_t& value, void* iterator)
{
    wspec_feature_iterator* it=(wspec_feature_iterator*) iterator;

    if (it->d>=degree)
    {
        if (it->j < it->vlen-1)
        {
            it->j++;
            it->d=0;
            it->mask=0;
            it->offs=0;
        }
        else
            return false;
    }

    int32_t d=it->d;

    it->mask = it->mask | (1 << (degree-d-1));
    int32_t idx=strings->get_masked_symbols(it->vec[it->j], it->mask);
    idx=strings->shift_symbol(idx, degree-d-1);
    value=it->alpha*spec_weights[d];
    index=it->offs + idx;
    it->offs+=strings->shift_offset(1,d+1);

    it->d=d+1;
    return true;
}

void CImplicitWeightedSpecFeatures::free_feature_iterator(void* iterator)
{
    ASSERT(iterator);
    wspec_feature_iterator* it=(wspec_feature_iterator*) iterator;
    strings->free_feature_vector(it->vec, it->vidx, it->vfree);
    delete[] it;
}