report_all_neighbors.hpp

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#ifndef KNNCOLLE_REPORT_ALL_NEIGHBORS_HPP
#define KNNCOLLE_REPORT_ALL_NEIGHBORS_HPP
 
#include <algorithm>
#include <vector>
 
namespace knncolle {
 
template<typename Index_>
Index_ count_all_neighbors_without_self(Index_ count) {
    return (count ? count - 1 : 0);
}
 
namespace internal {
 
template<bool do_indices_, bool do_distances_, typename Distance_, typename Index_>
void report_all_neighbors_raw(std::vector<std::pair<Distance_, Index_> >& all_neighbors, std::vector<Index_>* output_indices, std::vector<Distance_>* output_distances, Index_ i) {
    std::sort(all_neighbors.begin(), all_neighbors.end());
 
    auto target_size = count_all_neighbors_without_self(all_neighbors.size());
    if constexpr(do_indices_) {
        output_indices->clear();
        output_indices->reserve(target_size);
    }
    if constexpr(do_distances_) {
        output_distances->clear();
        output_distances->reserve(target_size);
    }
 
    for (const auto& an : all_neighbors) {
        if (an.second != i) {
            if constexpr(do_indices_) {
                output_indices->push_back(an.second);
            }
            if constexpr(do_distances_) {
                output_distances->push_back(an.first);
            }
        }
    }
}
 
template<bool do_indices_, bool do_distances_, typename Distance_, typename Index_>
void report_all_neighbors_raw(std::vector<std::pair<Distance_, Index_> >& all_neighbors, std::vector<Index_>* output_indices, std::vector<Distance_>* output_distances) {
    std::sort(all_neighbors.begin(), all_neighbors.end());
 
    auto target_size = all_neighbors.size();
    if constexpr(do_indices_) {
        output_indices->clear();
        output_indices->reserve(target_size);
    }
    if constexpr(do_distances_) {
        output_distances->clear();
        output_distances->reserve(target_size);
    }
 
    for (const auto& an : all_neighbors) {
        if constexpr(do_indices_) {
            output_indices->push_back(an.second);
        }
        if constexpr(do_distances_) {
            output_distances->push_back(an.first);
        }
    }
}
 
}
template<typename Distance_, typename Index_>
void report_all_neighbors(std::vector<std::pair<Distance_, Index_> >& all_neighbors, std::vector<Index_>* output_indices, std::vector<Distance_>* output_distances, Index_ self) {
    if (output_indices && output_distances) {
        internal::report_all_neighbors_raw<true, true>(all_neighbors, output_indices, output_distances, self);
    } else if (output_indices) {
        internal::report_all_neighbors_raw<true, false>(all_neighbors, output_indices, output_distances, self);
    } else if (output_distances) {
        internal::report_all_neighbors_raw<false, true>(all_neighbors, output_indices, output_distances, self);
    }
}
 
template<typename Distance_, typename Index_>
void report_all_neighbors(std::vector<std::pair<Distance_, Index_> >& all_neighbors, std::vector<Index_>* output_indices, std::vector<Distance_>* output_distances) {
    if (output_indices && output_distances) {
        internal::report_all_neighbors_raw<true, true>(all_neighbors, output_indices, output_distances);
    } else if (output_indices) {
        internal::report_all_neighbors_raw<true, false>(all_neighbors, output_indices, output_distances);
    } else if (output_distances) {
        internal::report_all_neighbors_raw<false, true>(all_neighbors, output_indices, output_distances);
    }
}
 
}
 
#endif