auto_range_index.h

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#pragma once
 
#include <cstddef>
#include <cstdint>
#include <variant>
#include <vector>
 
#include "clustering/index/brute_force_pairwise.h"
#include "clustering/index/kdtree.h"
#include "clustering/math/thread.h"
#include "clustering/ndarray.h"
 
namespace clustering::index {

template <class T> class AutoRangeIndex {
public:
#ifdef CLUSTERING_DBSCAN_BRUTE_FORCE_DIM_FLOOR
  static constexpr std::size_t bruteForceDimFloor = CLUSTERING_DBSCAN_BRUTE_FORCE_DIM_FLOOR;
#else
  static constexpr std::size_t bruteForceDimFloor = 16;
#endif

  explicit AutoRangeIndex(const NDArray<T, 2> &points) : m_held(pick(points)) {}

  [[nodiscard]] std::vector<std::vector<std::int32_t>> query(T radius, math::Pool pool) const {
    return std::visit([&](const auto &idx) { return idx.query(radius, pool); }, m_held);
  }
 
private:
  using Tree = KDTree<T, KDTreeDistanceType::kEucledian>;
  using Brute = BruteForcePairwise<T>;
  using Held = std::variant<Tree, Brute>;
 
  static Held pick(const NDArray<T, 2> &points) {
    if (points.dim(1) >= bruteForceDimFloor) {
      return Held(std::in_place_type<Brute>, points);
    }
    return Held(std::in_place_type<Tree>, points);
  }
 
  Held m_held; 
};
 
} // namespace clustering::index