NanoFlannIndex.h

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#pragma once

#include <vector>

#include "open3d/core/Tensor.h"
#include "open3d/core/nns/NNSIndex.h"
#include "open3d/utility/Console.h"

// Forward declarations.
namespace nanoflann {

template <class T, class DataSource, typename _DistanceType>
struct L2_Adaptor;

template <class T, class DataSource, typename _DistanceType>
struct L1_Adaptor;

template <typename Distance, class DatasetAdaptor, int DIM, typename IndexType>
class KDTreeSingleIndexAdaptor;

struct SearchParams;
};  // namespace nanoflann

namespace open3d {
namespace core {
namespace nns {

enum Metric { L1, L2, Linf };

struct NanoFlannIndexHolderBase {
    virtual ~NanoFlannIndexHolderBase() {}
};

template <int METRIC, class T>
struct NanoFlannIndexHolder : NanoFlannIndexHolderBase {
    struct DataAdaptor {
        DataAdaptor(size_t dataset_size, int dimension, const T *const data_ptr)
            : dataset_size_(dataset_size),
              dimension_(dimension),
              data_ptr_(data_ptr) {}

        inline size_t kdtree_get_point_count() const { return dataset_size_; }

        inline T kdtree_get_pt(const size_t idx, const size_t dim) const {
            return data_ptr_[idx * dimension_ + dim];
        }

        template <class BBOX>
        bool kdtree_get_bbox(BBOX &) const {
            return false;
        }

        size_t dataset_size_ = 0;
        int dimension_ = 0;
        const T *const data_ptr_;
    };

    template <int M, typename fake = void>
    struct SelectNanoflannAdaptor {};

    template <typename fake>
    struct SelectNanoflannAdaptor<L2, fake> {
        typedef nanoflann::L2_Adaptor<T, DataAdaptor, T> adaptor_t;
    };

    template <typename fake>
    struct SelectNanoflannAdaptor<L1, fake> {
        typedef nanoflann::L1_Adaptor<T, DataAdaptor, T> adaptor_t;
    };

    typedef nanoflann::KDTreeSingleIndexAdaptor<
            typename SelectNanoflannAdaptor<METRIC>::adaptor_t,
            DataAdaptor,
            -1,
            int64_t>
            KDTree_t;

    NanoFlannIndexHolder(size_t dataset_size,
                         int dimension,
                         const T *data_ptr) {
        adaptor_.reset(new DataAdaptor(dataset_size, dimension, data_ptr));
        index_.reset(new KDTree_t(dimension, *adaptor_.get()));
        index_->buildIndex();
    }

    std::unique_ptr<KDTree_t> index_;
    std::unique_ptr<DataAdaptor> adaptor_;
};

class NanoFlannIndex : public NNSIndex {
public:
    NanoFlannIndex();

    NanoFlannIndex(const Tensor &dataset_points);
    ~NanoFlannIndex();
    NanoFlannIndex(const NanoFlannIndex &) = delete;
    NanoFlannIndex &operator=(const NanoFlannIndex &) = delete;

public:
    bool SetTensorData(const Tensor &dataset_points) override;

    bool SetTensorData(const Tensor &dataset_points, double radius) override {
        utility::LogError(
                "NanoFlannIndex::SetTensorData with radius not implemented.");
    }

    std::pair<Tensor, Tensor> SearchKnn(const Tensor &query_points,
                                        int knn) const override;

    std::tuple<Tensor, Tensor, Tensor> SearchRadius(
            const Tensor &query_points, const Tensor &radii) const override;

    std::tuple<Tensor, Tensor, Tensor> SearchRadius(
            const Tensor &query_points, double radius) const override;

    std::pair<Tensor, Tensor> SearchHybrid(const Tensor &query_points,
                                           float radius,
                                           int max_knn) const override;

protected:
    // Tensor dataset_points_;
    std::unique_ptr<NanoFlannIndexHolderBase> holder_;
};
}  // namespace nns
}  // namespace core
}  // namespace open3d