numerics.cxx

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#include "numerics.hpp"

namespace numerics {

        std::vector< std::pair<uint32_t, float> > sparsify(const cv::Mat &dense) {
                std::vector< std::pair<uint32_t, float> > sparse;
                for(int i=0; i<dense.size().area(); i++) {
                        if( dense.at<float>(i) != 0.f) sparse.push_back( std::pair<uint32_t, float>(i, dense.at<float>(i)) );
                }
                return sparse;
        }

        float cos_sim(const std::vector<std::pair<uint32_t, float> > &weights0, 
                const std::vector<std::pair<uint32_t, float> > &weights1,
                const std::vector<float> &idfw) {
                float ab = 0.f, a2 = 0.f, b2 = 0.f;
                for(size_t i=0, j=0; i < weights0.size() || j < weights1.size();) {
                        if(i < weights0.size() && j < weights1.size()) {
                        if (weights0[i].first == weights1[j].first) {
                                float a = weights0[i].second * idfw[weights0[i].first];
                                float b = weights1[j].second * idfw[weights1[j].first];
                                ab += a*b;
                                        a2 += a*a;
                                        b2 += b*b;
                                        i++, j++;
                        } else if (weights0[i].first < weights1[j].first) {
                                float a = weights0[i].second * idfw[weights0[i].first];
                                a2 += a*a;
                                i++;
                        } else {
                                float b = weights1[j].second * idfw[weights1[j].first];
                                b2 += b*b;
                                j++;
                        }
                } else if(i < weights0.size()) {
                        float a = weights0[i].second * idfw[weights0[i].first];
                        a2 += a*a;
                        i++;
                } else {
                        float b = weights1[j].second * idfw[weights1[j].first];
                        b2 += b*b;
                        j++;
                }
                }
                return ab / (sqrtf(a2)*sqrtf(b2));
        }

        float min_hist(const std::vector<std::pair<uint32_t, float> > &weights0, 
                const std::vector<std::pair<uint32_t, float> > &weights1,
                const std::vector<float> &idfw) {
                float a = 0.f, b = 0.f, ab = 0.f;
                for(int k=0; k<weights0.size(); k++) {
                        a += weights0[k].second*idfw[weights0[k].first];
                }
                for(int k=0; k<weights1.size(); k++) {
                        b += weights1[k].second*idfw[weights1[k].first];
                }
                for(size_t i=0, j=0; i < weights0.size() && j < weights1.size();) {
                        if(i < weights0.size() && j < weights1.size()) {
                                if (weights0[i].first == weights1[j].first) {
                                        float min_val = weights0[i].second / a;
                                        if(min_val > (weights1[j].second / b))  {
                                                min_val = weights1[j].second / b;
                                        }
                                        ab += min_val * idfw[weights0[i].first];
                                        i++, j++;
                                } else if (weights0[i].first < weights1[j].first) {
                                        i++;
                                } else {
                                        j++;
                                }
                        }
                }
                return ab;
        }
}