DenseSubsetFeatures.h

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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) 2012 Chiyuan Zhang
 * Copyright (C) 2012 Chiyuan Zhang
 */

#ifndef DENSESUBSETFEATURES_H__
#define DENSESUBSETFEATURES_H__

#include <shogun/features/DenseFeatures.h>
#include <shogun/features/DotFeatures.h>

namespace shogun
{

template<class ST> class CDenseFeatures;
template<class ST> class SGVector;
class CDotFeatures;

template<class ST> class CDenseSubsetFeatures: public CDotFeatures
{
public:
    CDenseSubsetFeatures():m_fea(NULL) { set_generic<ST>(); }

    CDenseSubsetFeatures(CDenseFeatures<ST> *fea, SGVector<int32_t> idx)
        :m_fea(fea), m_idx(idx) { SG_REF(m_fea); set_generic<ST>(); }

    virtual ~CDenseSubsetFeatures() { SG_UNREF(m_fea); }

    virtual const char* get_name() const { return "DenseSubsetFeatures"; }

    void set_features(CDenseFeatures<ST> *fea)
    {
        SG_REF(fea);
        SG_UNREF(m_fea);
        m_fea = fea;
    }

    void set_subset_idx(SGVector<int32_t> idx)
    {
        m_idx = idx;
    }

    virtual CFeatures* duplicate() const
    {
        return new CDenseSubsetFeatures(m_fea, m_idx);
    }

    virtual EFeatureType get_feature_type() const
    {
        return m_fea->get_feature_type();
    }

    virtual EFeatureClass get_feature_class() const
    {
        return m_fea->get_feature_class();
    }

    virtual int32_t get_num_vectors() const
    {
        return m_fea->get_num_vectors();
    }

    virtual int32_t get_dim_feature_space() const
    {
        return m_idx.vlen;
    }

    virtual float64_t dot(int32_t vec_idx1, CDotFeatures* df, int32_t vec_idx2)
    {
        CDenseSubsetFeatures<ST> *dsf = dynamic_cast<CDenseSubsetFeatures<ST> *>(df);
        if (dsf == NULL)
            SG_ERROR("Require DenseSubsetFeatures of the same kind to perform dot\n")

        if (m_idx.vlen != dsf->m_idx.vlen)
            SG_ERROR("Cannot dot vectors of different length\n")

        SGVector<ST> vec1 = m_fea->get_feature_vector(vec_idx1);
        SGVector<ST> vec2 = dsf->m_fea->get_feature_vector(vec_idx2);
        
        float64_t sum = 0;
        for (int32_t i=0; i < m_idx.vlen; ++i)
            sum += vec1[m_idx[i]] * vec2[dsf->m_idx[i]];

        return sum;
    }

    virtual float64_t dense_dot(int32_t vec_idx1, const float64_t* vec2, int32_t vec2_len)
    {
        if (m_idx.vlen != vec2_len)
            SG_ERROR("Cannot dot vectors of different length\n")
        SGVector<ST> vec1 = m_fea->get_feature_vector(vec_idx1);

        float64_t sum=0;
        for (int32_t i=0; i < vec2_len; ++i)
            sum += vec1[m_idx[i]] * vec2[i];

        return sum;
    }

    virtual void add_to_dense_vec(float64_t alpha, int32_t vec_idx1, float64_t* vec2, int32_t vec2_len, bool abs_val=false)
    {
        if (m_idx.vlen != vec2_len)
            SG_ERROR("Cannot add_to_dense_vec vectors of different length\n")

        SGVector<ST> vec1 = m_fea->get_feature_vector(vec_idx1);
        if (abs_val)
        {
            for (int32_t i=0; i < vec2_len; ++i)
                vec2[i] += alpha * CMath::abs(vec1[m_idx[i]]);
        }
        else
        {
            for (int32_t i=0; i < vec2_len; ++i)
                vec2[i] += alpha * vec1[m_idx[i]];
        }
    }

    virtual int32_t get_nnz_features_for_vector(int32_t num)
    {
        return m_idx.vlen;
    }

    virtual void* get_feature_iterator(int32_t vector_index)
    {
        SG_NOTIMPLEMENTED
        return NULL;
    }

    virtual bool get_next_feature(int32_t& index, float64_t& value, void* iterator)
    {
        SG_NOTIMPLEMENTED
        return false;
    }

    virtual void free_feature_iterator(void* iterator)
    {
        SG_NOTIMPLEMENTED
    }
private:
    CDenseFeatures<ST> *m_fea;
    SGVector<int32_t> m_idx;
};
} /*  shogun */ 

#endif /* end of include guard: DENSESUBSETFEATURES_H__ */