OligoStringKernel.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 Christian Igel, Tobias Glasmachers
 * Copyright (C) 2008 Christian Igel, Tobias Glasmachers
 *
 * Shogun adjustments (W) 2008-2009 Soeren Sonnenburg
 * Copyright (C) 2008-2009 Fraunhofer Institute FIRST and Max-Planck-Society
 *
 */
#include "kernel/OligoStringKernel.h"
#include "kernel/SqrtDiagKernelNormalizer.h"
#include "features/StringFeatures.h"

#include <map>
#include <vector>
#include <algorithm>

using namespace shogun;

COligoStringKernel::COligoStringKernel(int32_t cache_sz, int32_t kmer_len, float64_t w)
: CStringKernel<char>(cache_sz), k(kmer_len), width(w), gauss_table(NULL)
{
    set_normalizer(new CSqrtDiagKernelNormalizer());
}

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

void COligoStringKernel::cleanup()
{
    delete[] gauss_table;
    gauss_table=NULL;

    CKernel::cleanup();
}

bool COligoStringKernel::init(CFeatures* l, CFeatures* r)
{
    cleanup();

    CStringKernel<char>::init(l,r);
    int32_t max_len=CMath::max(
            ((CStringFeatures<char>*) l)->get_max_vector_length(),
            ((CStringFeatures<char>*) r)->get_max_vector_length()
            );

    getExpFunctionCache(max_len);
    return init_normalizer();
}

void COligoStringKernel::encodeOligo(
    const std::string& sequence, uint32_t k_mer_length,
    const std::string& allowed_characters,
    std::vector< std::pair<int32_t, float64_t> >& values)
{
    float64_t oligo_value = 0.;
    float64_t factor      = 1.;
    std::map<std::string::value_type, uint32_t> residue_values;
    uint32_t counter = 0;
    uint32_t number_of_residues = allowed_characters.size();
    uint32_t sequence_length = sequence.size();
    bool sequence_ok = true;

    // checking if sequence contains illegal characters
    for (uint32_t i = 0; i < sequence.size(); ++i)
    {
        if (allowed_characters.find(sequence.at(i)) == std::string::npos)
            sequence_ok = false;
    }

    if (sequence_ok && k_mer_length <= sequence_length)
    {
        values.resize(sequence_length - k_mer_length + 1,
            std::pair<int32_t, float64_t>());
        for (uint32_t i = 0; i < number_of_residues; ++i)
        {   
            residue_values.insert(std::make_pair(allowed_characters[i], counter));
            ++counter;
        }
        for (int32_t k = k_mer_length - 1; k >= 0; k--)
        {
            oligo_value += factor * residue_values[sequence[k]];
            factor *= number_of_residues;
        }
        factor /= number_of_residues;
        counter = 0;
        values[counter].first = 1;
        values[counter].second = oligo_value;
        ++counter;

        for (uint32_t j = 1; j < sequence_length - k_mer_length + 1; j++)
        {
            oligo_value -= factor * residue_values[sequence[j - 1]];
            oligo_value = oligo_value * number_of_residues +
                residue_values[sequence[j + k_mer_length - 1]];

            values[counter].first = j + 1;
            values[counter].second = oligo_value ;
            ++counter;
        }
        stable_sort(values.begin(), values.end(), cmpOligos_);
    }
    else
    {
        values.clear();
    }   
}

void COligoStringKernel::getSequences(
    const std::vector<std::string>& sequences, uint32_t k_mer_length,
    const std::string& allowed_characters,
    std::vector< std::vector< std::pair<int32_t, float64_t> > >& encoded_sequences)
{
    std::vector< std::pair<int32_t, float64_t> > temp_vector;
    encoded_sequences.resize(sequences.size(),
        std::vector< std::pair<int32_t, float64_t> >());

    for (uint32_t i = 0; i < sequences.size(); ++i)
    {
        encodeOligo(sequences[i], k_mer_length, allowed_characters, temp_vector);
        encoded_sequences[i] = temp_vector;
    }
}

void COligoStringKernel::getExpFunctionCache(uint32_t sequence_length)
{
    delete[] gauss_table;
    gauss_table=new float64_t[sequence_length];

    gauss_table[0] = 1;
    for (uint32_t i = 1; i < sequence_length - 1; i++)
        gauss_table[i] = exp((-1 / (CMath::sq(width))) * CMath::sq(i));
}

float64_t COligoStringKernel::kernelOligoFast(
    const std::vector< std::pair<int32_t, float64_t> >& x,
    const std::vector< std::pair<int32_t, float64_t> >& y,
    int32_t max_distance)
{
    float64_t result = 0;
    int32_t  i1     = 0;
    int32_t  i2     = 0;
    int32_t  c1     = 0;
    uint32_t x_size = x.size();
    uint32_t y_size = y.size();

    while ((uint32_t) i1 < x_size && (uint32_t) i2 < y_size)
    {
        if (x[i1].second == y[i2].second)
        {
            if (max_distance < 0
                    || (abs(x[i1].first - y[i2].first)) <= max_distance)
            {
                result += gauss_table[abs((x[i1].first - y[i2].first))];
                if (x[i1].second == x[i1 + 1].second)
                {
                    i1++;
                    c1++;
                }
                else if (y[i2].second == y[i2 + 1].second)
                {
                    i2++;
                    i1 -= c1;
                    c1 = 0;
                }
                else
                {
                    i1++;
                    i2++;
                }
            }
            else
            {
                if (x[i1].first < y[i2].first)
                {
                    if (x[i1].second == x[i1 + 1].second)
                    {
                        i1++;
                    }
                    else if (y[i2].second == y[i2 + 1].second)
                    {
                        while(y[i2++].second == y[i2].second)
                        {
                            ;
                        }
                        ++i1;
                        c1 = 0;
                    }
                    else
                    {
                        i1++;
                        i2++;
                        c1 = 0;
                    }
                }
                else
                {
                    i2++;
                    i1 -= c1;
                    c1 = 0;
                }
            }
        }
        else
        {
            if (x[i1].second < y[i2].second)
                i1++;
            else
                i2++;
            c1 = 0;
        }
    }
    return result;
}       


float64_t COligoStringKernel::compute(int32_t idx_a, int32_t idx_b)
{
    int32_t alen, blen;
    bool free_a, free_b;
    char* avec=((CStringFeatures<char>*) lhs)->get_feature_vector(idx_a, alen, free_a);
    char* bvec=((CStringFeatures<char>*) rhs)->get_feature_vector(idx_b, blen, free_b);
    std::vector< std::pair<int32_t, float64_t> > aenc;
    std::vector< std::pair<int32_t, float64_t> > benc;
    encodeOligo(std::string(avec, alen), k, "ACGT", aenc);
    encodeOligo(std::string(bvec, alen), k, "ACGT", benc);
    float64_t result=kernelOligoFast(aenc, benc);
    ((CStringFeatures<char>*) lhs)->free_feature_vector(avec, idx_a, free_a);
    ((CStringFeatures<char>*) rhs)->free_feature_vector(bvec, idx_b, free_b);
    return result;
}