nanoflann.hpp

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/***********************************************************************
 * Software License Agreement (BSD License)
 *
 * Copyright 2008-2009  Marius Muja (mariusm@cs.ubc.ca). All rights reserved.
 * Copyright 2008-2009  David G. Lowe (lowe@cs.ubc.ca). All rights reserved.
 * Copyright 2011 Jose Luis Blanco (joseluisblancoc@gmail.com).
 *   All rights reserved.
 *
 * THE BSD LICENSE
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#ifndef  NANOFLANN_HPP_
#define  NANOFLANN_HPP_

#include <vector>
#include <cassert>
#include <algorithm>
#include <stdexcept>
#include <cstdio>  // for fwrite()
#include <cmath>   // for fabs(),...
#include <limits>

// Avoid conflicting declaration of min/max macros in windows headers
#if !defined(NOMINMAX) && (defined(_WIN32) || defined(_WIN32_)  || defined(WIN32) || defined(_WIN64))
# define NOMINMAX
# ifdef max
#  undef   max
#  undef   min
# endif
#endif

namespace nanoflann
{
        #define NANOFLANN_VERSION 0x113

        template <typename DistanceType, typename IndexType = size_t, typename CountType = size_t>
        class KNNResultSet
        {
                IndexType * indices;
                DistanceType* dists;
                CountType capacity;
                CountType count;

        public:
                inline KNNResultSet(CountType capacity_) : capacity(capacity_), count(0)
                {
                }

                inline void init(IndexType* indices_, DistanceType* dists_)
                {
                        indices = indices_;
                        dists = dists_;
                        count = 0;
                        dists[capacity-1] = (std::numeric_limits<DistanceType>::max)();
                }

                inline CountType size() const
                {
                        return count;
                }

                inline bool full() const
                {
                        return count == capacity;
                }


                inline void addPoint(DistanceType dist, IndexType index)
                {
                        CountType i;
                        for (i=count; i>0; --i) {
#ifdef NANOFLANN_FIRST_MATCH   // If defined and two poins have the same distance, the one with the lowest-index will be returned first.
                                if ( (dists[i-1]>dist) || ((dist==dists[i-1])&&(indices[i-1]>index)) ) {
#else
                                if (dists[i-1]>dist) {
#endif
                                        if (i<capacity) {
                                                dists[i] = dists[i-1];
                                                indices[i] = indices[i-1];
                                        }
                                }
                                else break;
                        }
                        if (i<capacity) {
                                dists[i] = dist;
                                indices[i] = index;
                        }
                        if (count<capacity) count++;
                }

                inline DistanceType worstDist() const
                {
                        return dists[capacity-1];
                }
        };


        template <typename DistanceType, typename IndexType = size_t>
        class RadiusResultSet
        {
        public:
                const DistanceType radius;

                std::vector<std::pair<IndexType,DistanceType> >& m_indices_dists;

                inline RadiusResultSet(DistanceType radius_, std::vector<std::pair<IndexType,DistanceType> >& indices_dists) : radius(radius_), m_indices_dists(indices_dists)
                {
                        init();
                }

                inline ~RadiusResultSet() { }

                inline void init() { clear(); }
                inline void clear() { m_indices_dists.clear(); }

                inline size_t size() const { return m_indices_dists.size(); }

                inline bool full() const { return true; }

                inline void addPoint(DistanceType dist, IndexType index)
                {
                        if (dist<radius)
                                m_indices_dists.push_back(std::make_pair<IndexType,DistanceType>(index,dist));
                }

                inline DistanceType worstDist() const { return radius; }

                inline void set_radius_and_clear( const DistanceType r )
                {
                        radius = r;
                        clear();
                }

                std::pair<IndexType,DistanceType> worst_item() const
                {
                   if (m_indices_dists.empty()) throw std::runtime_error("Cannot invoke RadiusResultSet::worst_item() on an empty list of results.");
                   typedef typename std::vector<std::pair<IndexType,DistanceType> >::const_iterator DistIt;
                   DistIt it = std::max_element(m_indices_dists.begin(), m_indices_dists.end());
                   return *it;
                }
        };

        struct IndexDist_Sorter
        {
                template <typename PairType>
                inline bool operator()(const PairType &p1, const PairType &p2) const {
                        return p1.second < p2.second;
                }
        };

        template<typename T>
        void save_value(FILE* stream, const T& value, size_t count = 1)
        {
                fwrite(&value, sizeof(value),count, stream);
        }

        template<typename T>
        void save_value(FILE* stream, const std::vector<T>& value)
        {
                size_t size = value.size();
                fwrite(&size, sizeof(size_t), 1, stream);
                fwrite(&value[0], sizeof(T), size, stream);
        }

        template<typename T>
        void load_value(FILE* stream, T& value, size_t count = 1)
        {
                size_t read_cnt = fread(&value, sizeof(value), count, stream);
                if (read_cnt != count) {
                        throw std::runtime_error("Cannot read from file");
                }
        }


        template<typename T>
        void load_value(FILE* stream, std::vector<T>& value)
        {
                size_t size;
                size_t read_cnt = fread(&size, sizeof(size_t), 1, stream);
                if (read_cnt!=1) {
                        throw std::runtime_error("Cannot read from file");
                }
                value.resize(size);
                read_cnt = fread(&value[0], sizeof(T), size, stream);
                if (read_cnt!=size) {
                        throw std::runtime_error("Cannot read from file");
                }
        }
        template<typename T> inline T abs(T x) { return (x<0) ? -x : x; }
        template<> inline int abs<int>(int x) { return ::abs(x); }
        template<> inline float abs<float>(float x) { return fabsf(x); }
        template<> inline double abs<double>(double x) { return fabs(x); }
        template<> inline long double abs<long double>(long double x) { return fabsl(x); }

        template<class T, class DataSource, typename _DistanceType = T>
        struct L1_Adaptor
        {
                typedef T ElementType;
                typedef _DistanceType DistanceType;

                const DataSource &data_source;

                L1_Adaptor(const DataSource &_data_source) : data_source(_data_source) { }

                inline DistanceType operator()(const T* a, const size_t b_idx, size_t size, DistanceType worst_dist = -1) const
                {
                        DistanceType result = DistanceType();
                        const T* last = a + size;
                        const T* lastgroup = last - 3;
                        size_t d = 0;

                        /* Process 4 items with each loop for efficiency. */
                        while (a < lastgroup) {
                                const DistanceType diff0 = nanoflann::abs(a[0] - data_source.kdtree_get_pt(b_idx,d++));
                                const DistanceType diff1 = nanoflann::abs(a[1] - data_source.kdtree_get_pt(b_idx,d++));
                                const DistanceType diff2 = nanoflann::abs(a[2] - data_source.kdtree_get_pt(b_idx,d++));
                                const DistanceType diff3 = nanoflann::abs(a[3] - data_source.kdtree_get_pt(b_idx,d++));
                                result += diff0 + diff1 + diff2 + diff3;
                                a += 4;
                                if ((worst_dist>0)&&(result>worst_dist)) {
                                        return result;
                                }
                        }
                        /* Process last 0-3 components.  Not needed for standard vector lengths. */
                        while (a < last) {
                                result += nanoflann::abs( *a++ - data_source.kdtree_get_pt(b_idx,d++) );
                        }
                        return result;
                }

                template <typename U, typename V>
                inline DistanceType accum_dist(const U a, const V b, int dim) const
                {
                        return (a-b)*(a-b);
                }
        };

        template<class T, class DataSource, typename _DistanceType = T>
        struct L2_Adaptor
        {
                typedef T ElementType;
                typedef _DistanceType DistanceType;

                const DataSource &data_source;

                L2_Adaptor(const DataSource &_data_source) : data_source(_data_source) { }

                inline DistanceType operator()(const T* a, const size_t b_idx, size_t size, DistanceType worst_dist = -1) const
                {
                        DistanceType result = DistanceType();
                        const T* last = a + size;
                        const T* lastgroup = last - 3;
                        size_t d = 0;

                        /* Process 4 items with each loop for efficiency. */
                        while (a < lastgroup) {
                                const DistanceType diff0 = a[0] - data_source.kdtree_get_pt(b_idx,d++);
                                const DistanceType diff1 = a[1] - data_source.kdtree_get_pt(b_idx,d++);
                                const DistanceType diff2 = a[2] - data_source.kdtree_get_pt(b_idx,d++);
                                const DistanceType diff3 = a[3] - data_source.kdtree_get_pt(b_idx,d++);
                                result += diff0 * diff0 + diff1 * diff1 + diff2 * diff2 + diff3 * diff3;
                                a += 4;
                                if ((worst_dist>0)&&(result>worst_dist)) {
                                        return result;
                                }
                        }
                        /* Process last 0-3 components.  Not needed for standard vector lengths. */
                        while (a < last) {
                                const DistanceType diff0 = *a++ - data_source.kdtree_get_pt(b_idx,d++);
                                result += diff0 * diff0;
                        }
                        return result;
                }

                template <typename U, typename V>
                inline DistanceType accum_dist(const U a, const V b, int dim) const
                {
                        return (a-b)*(a-b);
                }
        };

        template<class T, class DataSource, typename _DistanceType = T>
        struct L2_Simple_Adaptor
        {
                typedef T ElementType;
                typedef _DistanceType DistanceType;

                const DataSource &data_source;

                L2_Simple_Adaptor(const DataSource &_data_source) : data_source(_data_source) { }

                inline DistanceType operator()(const T* a, const size_t b_idx, size_t size) const {
                        return data_source.kdtree_distance(a,b_idx,size);
                }

                template <typename U, typename V>
                inline DistanceType accum_dist(const U a, const V b, int dim) const
                {
                        return (a-b)*(a-b);
                }
        };

        struct metric_L1 {
                template<class T, class DataSource>
                struct traits {
                        typedef L1_Adaptor<T,DataSource> distance_t;
                };
        };
        struct metric_L2 {
                template<class T, class DataSource>
                struct traits {
                        typedef L2_Adaptor<T,DataSource> distance_t;
                };
        };
        struct metric_L2_Simple {
                template<class T, class DataSource>
                struct traits {
                        typedef L2_Simple_Adaptor<T,DataSource> distance_t;
                };
        };

        struct KDTreeSingleIndexAdaptorParams
        {
                KDTreeSingleIndexAdaptorParams(size_t _leaf_max_size = 10, int dim_ = -1) :
                        leaf_max_size(_leaf_max_size), dim(dim_)
                {}

                size_t leaf_max_size;
                int dim;
        };

        struct SearchParams
        {
                SearchParams(int checks_IGNORED_ = 32, float eps_ = 0, bool sorted_ = true ) :
                        eps(eps_), sorted(sorted_) {}

                int   checks;  
                float eps;  
                bool sorted; 
        };
        template <typename T>
        inline T* allocate(size_t count = 1)
        {
                T* mem = (T*) ::malloc(sizeof(T)*count);
                return mem;
        }


        const size_t     WORDSIZE=16;
        const size_t     BLOCKSIZE=8192;

        class PooledAllocator
        {
                /* We maintain memory alignment to word boundaries by requiring that all
                    allocations be in multiples of the machine wordsize.  */
                /* Size of machine word in bytes.  Must be power of 2. */
                /* Minimum number of bytes requested at a time from     the system.  Must be multiple of WORDSIZE. */


                size_t  remaining;  /* Number of bytes left in current block of storage. */
                void*   base;     /* Pointer to base of current block of storage. */
                void*   loc;      /* Current location in block to next allocate memory. */
                size_t  blocksize;


        public:
                size_t  usedMemory;
                size_t  wastedMemory;

                PooledAllocator(const size_t blocksize = BLOCKSIZE)
                {
                        this->blocksize = blocksize;
                        remaining = 0;
                        base = NULL;

                        usedMemory = 0;
                        wastedMemory = 0;
                }

                ~PooledAllocator()
                {
                        while (base != NULL) {
                                void *prev = *((void**) base); /* Get pointer to prev block. */
                                ::free(base);
                                base = prev;
                        }
                }

                void* malloc(const size_t req_size)
                {
                        /* Round size up to a multiple of wordsize.  The following expression
                            only works for WORDSIZE that is a power of 2, by masking last bits of
                            incremented size to zero.
                         */
                        const size_t size = (req_size + (WORDSIZE - 1)) & ~(WORDSIZE - 1);

                        /* Check whether a new block must be allocated.  Note that the first word
                            of a block is reserved for a pointer to the previous block.
                         */
                        if (size > remaining) {

                                wastedMemory += remaining;

                                /* Allocate new storage. */
                                const size_t blocksize = (size + sizeof(void*) + (WORDSIZE-1) > BLOCKSIZE) ?
                                                        size + sizeof(void*) + (WORDSIZE-1) : BLOCKSIZE;

                                // use the standard C malloc to allocate memory
                                void* m = ::malloc(blocksize);
                                if (!m) {
                                        fprintf(stderr,"Failed to allocate memory.\n");
                                        return NULL;
                                }

                                /* Fill first word of new block with pointer to previous block. */
                                ((void**) m)[0] = base;
                                base = m;

                                size_t shift = 0;
                                //int size_t = (WORDSIZE - ( (((size_t)m) + sizeof(void*)) & (WORDSIZE-1))) & (WORDSIZE-1);

                                remaining = blocksize - sizeof(void*) - shift;
                                loc = ((char*)m + sizeof(void*) + shift);
                        }
                        void* rloc = loc;
                        loc = (char*)loc + size;
                        remaining -= size;

                        usedMemory += size;

                        return rloc;
                }

                template <typename T>
                T* allocate(const size_t count = 1)
                {
                        T* mem = (T*) this->malloc(sizeof(T)*count);
                        return mem;
                }

        };
        template <typename Distance, class DatasetAdaptor,int DIM = -1, typename IndexType = size_t>
        class KDTreeSingleIndexAdaptor
        {
        public:
                typedef typename Distance::ElementType  ElementType;
                typedef typename Distance::DistanceType DistanceType;
        protected:

                std::vector<IndexType> vind;

                size_t m_leaf_max_size;


                const DatasetAdaptor &dataset; 

                const KDTreeSingleIndexAdaptorParams index_params;

                size_t m_size;
                int dim;  


                /*--------------------- Internal Data Structures --------------------------*/
                struct Node
                {
                        union {
                                struct
                                {
                                        IndexType left, right;
                                } lr;
                                struct
                                {
                                        int divfeat;
                                        DistanceType divlow, divhigh;
                                } sub;
                        };
                        Node* child1, * child2;
                };
                typedef Node* NodePtr;


                struct Interval
                {
                        ElementType low, high;
                };

                typedef std::vector<Interval> BoundingBox;


                template <typename T, typename DistanceType>
                struct BranchStruct
                {
                        T node;           /* Tree node at which search resumes */
                        DistanceType mindist;     /* Minimum distance to query for all nodes below. */

                        BranchStruct() {}
                        BranchStruct(const T& aNode, DistanceType dist) : node(aNode), mindist(dist) {}

                        inline bool operator<(const BranchStruct<T, DistanceType>& rhs) const
                        {
                                return mindist<rhs.mindist;
                        }
                };

                NodePtr root_node;
                typedef BranchStruct<NodePtr, DistanceType> BranchSt;
                typedef BranchSt* Branch;

                BoundingBox root_bbox;

                PooledAllocator pool;

        public:

                Distance distance;

                KDTreeSingleIndexAdaptor(const int dimensionality, const DatasetAdaptor& inputData, const KDTreeSingleIndexAdaptorParams& params = KDTreeSingleIndexAdaptorParams() ) :
                        dataset(inputData), index_params(params), distance(inputData)
                {
                        m_size = dataset.kdtree_get_point_count();
                        dim = dimensionality;
                        if (DIM>0) dim=DIM;
                        else {
                                if (params.dim>0) dim = params.dim;
                        }
                        m_leaf_max_size = params.leaf_max_size;

                        // Create a permutable array of indices to the input vectors.
                        init_vind();
                }

                ~KDTreeSingleIndexAdaptor()
                {
                }

                void buildIndex()
                {
                        init_vind();
                        computeBoundingBox(root_bbox);
                        root_node = divideTree(0, m_size, root_bbox );   // construct the tree
                }

                size_t size() const
                {
                        return m_size;
                }

                size_t veclen() const
                {
                        return static_cast<size_t>(DIM>0 ? DIM : dim);
                }

                size_t usedMemory() const
                {
                        return pool.usedMemory+pool.wastedMemory+dataset.kdtree_get_point_count()*sizeof(IndexType);  // pool memory and vind array memory
                }

                template <typename RESULTSET>
                void findNeighbors(RESULTSET& result, const ElementType* vec, const SearchParams& searchParams) const
                {
                        assert(vec);
                        float epsError = 1+searchParams.eps;

                        std::vector<DistanceType> dists( (DIM>0 ? DIM : dim) ,0);
                        DistanceType distsq = computeInitialDistances(vec, dists);
                        searchLevel(result, vec, root_node, distsq, dists, epsError);  // "count_leaf" parameter removed since was neither used nor returned to the user.
                }

                inline void knnSearch(const ElementType *query_point, const size_t num_closest, IndexType *out_indices, DistanceType *out_distances_sq, const int nChecks_IGNORED = 10) const
                {
                        nanoflann::KNNResultSet<DistanceType,IndexType> resultSet(num_closest);
                        resultSet.init(out_indices, out_distances_sq);
                        this->findNeighbors(resultSet, query_point, nanoflann::SearchParams());
                }

                size_t radiusSearch(const ElementType *query_point,const DistanceType radius, std::vector<std::pair<IndexType,DistanceType> >& IndicesDists, const SearchParams& searchParams) const
                {
                        RadiusResultSet<DistanceType,IndexType> resultSet(radius,IndicesDists);
                        this->findNeighbors(resultSet, query_point, searchParams);

                        if (searchParams.sorted)
                                std::sort(IndicesDists.begin(),IndicesDists.end(), IndexDist_Sorter() );

                        return resultSet.size();
                }

        private:
                void init_vind()
                {
                        // Create a permutable array of indices to the input vectors.
                        m_size = dataset.kdtree_get_point_count();
                        if (vind.size()!=m_size)
                        {
                                vind.resize(m_size);
                                for (size_t i = 0; i < m_size; i++) vind[i] = i;
                        }
                }

                inline ElementType dataset_get(size_t idx, int component) const {
                        return dataset.kdtree_get_pt(idx,component);
                }


                void save_tree(FILE* stream, NodePtr tree)
                {
                        save_value(stream, *tree);
                        if (tree->child1!=NULL) {
                                save_tree(stream, tree->child1);
                        }
                        if (tree->child2!=NULL) {
                                save_tree(stream, tree->child2);
                        }
                }


                void load_tree(FILE* stream, NodePtr& tree)
                {
                        tree = pool.allocate<Node>();
                        load_value(stream, *tree);
                        if (tree->child1!=NULL) {
                                load_tree(stream, tree->child1);
                        }
                        if (tree->child2!=NULL) {
                                load_tree(stream, tree->child2);
                        }
                }


                void computeBoundingBox(BoundingBox& bbox)
                {
                        bbox.resize((DIM>0 ? DIM : dim));
                        if (dataset.kdtree_get_bbox(bbox))
                        {
                                // Done! It was implemented in derived class
                        }
                        else
                        {
                                for (int i=0; i<(DIM>0 ? DIM : dim); ++i) {
                                        bbox[i].low =
                                                bbox[i].high = dataset_get(0,i);
                                }
                                const size_t N = dataset.kdtree_get_point_count();
                                for (size_t k=1; k<N; ++k) {
                                        for (int i=0; i<(DIM>0 ? DIM : dim); ++i) {
                                                if (dataset_get(k,i)<bbox[i].low) bbox[i].low = dataset_get(k,i);
                                                if (dataset_get(k,i)>bbox[i].high) bbox[i].high = dataset_get(k,i);
                                        }
                                }
                        }
                }


                NodePtr divideTree(const IndexType left, const IndexType right, BoundingBox& bbox)
                {
                        NodePtr node = pool.allocate<Node>(); // allocate memory

                        /* If too few exemplars remain, then make this a leaf node. */
                        if ( (right-left) <= m_leaf_max_size) {
                                node->child1 = node->child2 = NULL;    /* Mark as leaf node. */
                                node->lr.left = left;
                                node->lr.right = right;

                                // compute bounding-box of leaf points
                                for (int i=0; i<(DIM>0 ? DIM : dim); ++i) {
                                        bbox[i].low = dataset_get(vind[left],i);
                                        bbox[i].high = dataset_get(vind[left],i);
                                }
                                for (IndexType k=left+1; k<right; ++k) {
                                        for (int i=0; i<(DIM>0 ? DIM : dim); ++i) {
                                                if (bbox[i].low>dataset_get(vind[k],i)) bbox[i].low=dataset_get(vind[k],i);
                                                if (bbox[i].high<dataset_get(vind[k],i)) bbox[i].high=dataset_get(vind[k],i);
                                        }
                                }
                        }
                        else {
                                IndexType idx;
                                int cutfeat;
                                DistanceType cutval;
                                middleSplit_(&vind[0]+left, right-left, idx, cutfeat, cutval, bbox);

                                node->sub.divfeat = cutfeat;

                                BoundingBox left_bbox(bbox);
                                left_bbox[cutfeat].high = cutval;
                                node->child1 = divideTree(left, left+idx, left_bbox);

                                BoundingBox right_bbox(bbox);
                                right_bbox[cutfeat].low = cutval;
                                node->child2 = divideTree(left+idx, right, right_bbox);

                                node->sub.divlow = left_bbox[cutfeat].high;
                                node->sub.divhigh = right_bbox[cutfeat].low;

                                for (int i=0; i<(DIM>0 ? DIM : dim); ++i) {
                                        bbox[i].low = std::min(left_bbox[i].low, right_bbox[i].low);
                                        bbox[i].high = std::max(left_bbox[i].high, right_bbox[i].high);
                                }
                        }

                        return node;
                }

                void computeMinMax(IndexType* ind, IndexType count, int element, ElementType& min_elem, ElementType& max_elem)
                {
                        min_elem = dataset_get(ind[0],element);
                        max_elem = dataset_get(ind[0],element);
                        for (IndexType i=1; i<count; ++i) {
                                ElementType val = dataset_get(ind[i],element);
                                if (val<min_elem) min_elem = val;
                                if (val>max_elem) max_elem = val;
                        }
                }

                void middleSplit(IndexType* ind, IndexType count, IndexType& index, int& cutfeat, DistanceType& cutval, const BoundingBox& bbox)
                {
                        // find the largest span from the approximate bounding box
                        ElementType max_span = bbox[0].high-bbox[0].low;
                        cutfeat = 0;
                        cutval = (bbox[0].high+bbox[0].low)/2;
                        for (int i=1; i<(DIM>0 ? DIM : dim); ++i) {
                                ElementType span = bbox[i].low-bbox[i].low;
                                if (span>max_span) {
                                        max_span = span;
                                        cutfeat = i;
                                        cutval = (bbox[i].high+bbox[i].low)/2;
                                }
                        }

                        // compute exact span on the found dimension
                        ElementType min_elem, max_elem;
                        computeMinMax(ind, count, cutfeat, min_elem, max_elem);
                        cutval = (min_elem+max_elem)/2;
                        max_span = max_elem - min_elem;

                        // check if a dimension of a largest span exists
                        size_t k = cutfeat;
                        for (size_t i=0; i<(DIM>0 ? DIM : dim); ++i) {
                                if (i==k) continue;
                                ElementType span = bbox[i].high-bbox[i].low;
                                if (span>max_span) {
                                        computeMinMax(ind, count, i, min_elem, max_elem);
                                        span = max_elem - min_elem;
                                        if (span>max_span) {
                                                max_span = span;
                                                cutfeat = i;
                                                cutval = (min_elem+max_elem)/2;
                                        }
                                }
                        }
                        IndexType lim1, lim2;
                        planeSplit(ind, count, cutfeat, cutval, lim1, lim2);

                        if (lim1>count/2) index = lim1;
                        else if (lim2<count/2) index = lim2;
                        else index = count/2;
                }


                void middleSplit_(IndexType* ind, IndexType count, IndexType& index, int& cutfeat, DistanceType& cutval, const BoundingBox& bbox)
                {
                        const DistanceType EPS=static_cast<DistanceType>(0.00001);
                        ElementType max_span = bbox[0].high-bbox[0].low;
                        for (int i=1; i<(DIM>0 ? DIM : dim); ++i) {
                                ElementType span = bbox[i].high-bbox[i].low;
                                if (span>max_span) {
                                        max_span = span;
                                }
                        }
                        ElementType max_spread = -1;
                        cutfeat = 0;
                        for (int i=0; i<(DIM>0 ? DIM : dim); ++i) {
                                ElementType span = bbox[i].high-bbox[i].low;
                                if (span>(1-EPS)*max_span) {
                                        ElementType min_elem, max_elem;
                                        computeMinMax(ind, count, cutfeat, min_elem, max_elem);
                                        ElementType spread = max_elem-min_elem;;
                                        if (spread>max_spread) {
                                                cutfeat = i;
                                                max_spread = spread;
                                        }
                                }
                        }
                        // split in the middle
                        DistanceType split_val = (bbox[cutfeat].low+bbox[cutfeat].high)/2;
                        ElementType min_elem, max_elem;
                        computeMinMax(ind, count, cutfeat, min_elem, max_elem);

                        if (split_val<min_elem) cutval = min_elem;
                        else if (split_val>max_elem) cutval = max_elem;
                        else cutval = split_val;

                        IndexType lim1, lim2;
                        planeSplit(ind, count, cutfeat, cutval, lim1, lim2);

                        if (lim1>count/2) index = lim1;
                        else if (lim2<count/2) index = lim2;
                        else index = count/2;
                }


                void planeSplit(IndexType* ind, const IndexType count, int cutfeat, DistanceType cutval, IndexType& lim1, IndexType& lim2)
                {
                        /* Move vector indices for left subtree to front of list. */
                        IndexType left = 0;
                        IndexType right = count-1;
                        for (;; ) {
                                while (left<=right && dataset_get(ind[left],cutfeat)<cutval) ++left;
                                while (right && left<=right && dataset_get(ind[right],cutfeat)>=cutval) --right;
                                if (left>right || !right) break;  // "!right" was added to support unsigned Index types
                                std::swap(ind[left], ind[right]);
                                ++left;
                                --right;
                        }
                        /* If either list is empty, it means that all remaining features
                         * are identical. Split in the middle to maintain a balanced tree.
                         */
                        lim1 = left;
                        right = count-1;
                        for (;; ) {
                                while (left<=right && dataset_get(ind[left],cutfeat)<=cutval) ++left;
                                while (right && left<=right && dataset_get(ind[right],cutfeat)>cutval) --right;
                                if (left>right || !right) break;  // "!right" was added to support unsigned Index types
                                std::swap(ind[left], ind[right]);
                                ++left;
                                --right;
                        }
                        lim2 = left;
                }

                DistanceType computeInitialDistances(const ElementType* vec, std::vector<DistanceType>& dists) const
                {
                        assert(vec);
                        DistanceType distsq = 0.0;

                        for (int i = 0; i < (DIM>0 ? DIM : dim); ++i) {
                                if (vec[i] < root_bbox[i].low) {
                                        dists[i] = distance.accum_dist(vec[i], root_bbox[i].low, i);
                                        distsq += dists[i];
                                }
                                if (vec[i] > root_bbox[i].high) {
                                        dists[i] = distance.accum_dist(vec[i], root_bbox[i].high, i);
                                        distsq += dists[i];
                                }
                        }

                        return distsq;
                }

                template <class RESULTSET>
                void searchLevel(RESULTSET& result_set, const ElementType* vec, const NodePtr node, DistanceType mindistsq,
                                                 std::vector<DistanceType>& dists, const float epsError) const
                {
                        /* If this is a leaf node, then do check and return. */
                        if ((node->child1 == NULL)&&(node->child2 == NULL)) {
                                //count_leaf += (node->lr.right-node->lr.left);  // Removed since was neither used nor returned to the user.
                                DistanceType worst_dist = result_set.worstDist();
                                for (IndexType i=node->lr.left; i<node->lr.right; ++i) {
                                        const IndexType index = vind[i];// reorder... : i;
                                        DistanceType dist = distance(vec, index, (DIM>0 ? DIM : dim));
                                        if (dist<worst_dist) {
                                                result_set.addPoint(dist,vind[i]);
                                        }
                                }
                                return;
                        }

                        /* Which child branch should be taken first? */
                        int idx = node->sub.divfeat;
                        ElementType val = vec[idx];
                        DistanceType diff1 = val - node->sub.divlow;
                        DistanceType diff2 = val - node->sub.divhigh;

                        NodePtr bestChild;
                        NodePtr otherChild;
                        DistanceType cut_dist;
                        if ((diff1+diff2)<0) {
                                bestChild = node->child1;
                                otherChild = node->child2;
                                cut_dist = distance.accum_dist(val, node->sub.divhigh, idx);
                        }
                        else {
                                bestChild = node->child2;
                                otherChild = node->child1;
                                cut_dist = distance.accum_dist( val, node->sub.divlow, idx);
                        }

                        /* Call recursively to search next level down. */
                        searchLevel(result_set, vec, bestChild, mindistsq, dists, epsError);

                        DistanceType dst = dists[idx];
                        mindistsq = mindistsq + cut_dist - dst;
                        dists[idx] = cut_dist;
                        if (mindistsq*epsError<=result_set.worstDist()) {
                                searchLevel(result_set, vec, otherChild, mindistsq, dists, epsError);
                        }
                        dists[idx] = dst;
                }


                void saveIndex(FILE* stream)
                {
                        save_value(stream, m_size);
                        save_value(stream, dim);
                        save_value(stream, root_bbox);
                        save_value(stream, m_leaf_max_size);
                        save_value(stream, vind);
                        save_tree(stream, root_node);
                }

                void loadIndex(FILE* stream)
                {
                        load_value(stream, m_size);
                        load_value(stream, dim);
                        load_value(stream, root_bbox);
                        load_value(stream, m_leaf_max_size);
                        load_value(stream, vind);
                        load_tree(stream, root_node);
                }

        };   // class KDTree


        template <class MatrixType, int DIM = -1, class Distance = nanoflann::metric_L2, typename IndexType = size_t>
        struct KDTreeEigenMatrixAdaptor
        {
                typedef KDTreeEigenMatrixAdaptor<MatrixType,DIM,Distance> self_t;
                typedef typename MatrixType::Scalar              num_t;
                typedef typename Distance::template traits<num_t,self_t>::distance_t metric_t;
                typedef KDTreeSingleIndexAdaptor< metric_t,self_t,DIM,IndexType>  index_t;

                index_t* index; 

                KDTreeEigenMatrixAdaptor(const int dimensionality, const MatrixType &mat, const int leaf_max_size = 10) : m_data_matrix(mat)
                {
                        const size_t dims = mat.cols();
                        if (DIM>0 && static_cast<int>(dims)!=DIM)
                                throw std::runtime_error("Data set dimensionality does not match the 'DIM' template argument");
                        index = new index_t( dims, *this /* adaptor */, nanoflann::KDTreeSingleIndexAdaptorParams(leaf_max_size, dims ) );
                        index->buildIndex();
                }

                ~KDTreeEigenMatrixAdaptor() {
                        delete index;
                }

                const MatrixType &m_data_matrix;

                inline void query(const num_t *query_point, const size_t num_closest, IndexType *out_indices, num_t *out_distances_sq, const int nChecks_IGNORED = 10) const
                {
                        nanoflann::KNNResultSet<typename MatrixType::Scalar,IndexType> resultSet(num_closest);
                        resultSet.init(out_indices, out_distances_sq);
                        index->findNeighbors(resultSet, query_point, nanoflann::SearchParams());
                }

                const self_t & derived() const {
                        return *this;
                }
                self_t & derived()       {
                        return *this;
                }

                // Must return the number of data points
                inline size_t kdtree_get_point_count() const {
                        return m_data_matrix.rows();
                }

                // Returns the distance between the vector "p1[0:size-1]" and the data point with index "idx_p2" stored in the class:
                inline num_t kdtree_distance(const num_t *p1, const size_t idx_p2,size_t size) const
                {
                        num_t s=0;
                        for (size_t i=0; i<size; i++) {
                                const num_t d= p1[i]-m_data_matrix.coeff(idx_p2,i);
                                s+=d*d;
                        }
                        return s;
                }

                // Returns the dim'th component of the idx'th point in the class:
                inline num_t kdtree_get_pt(const size_t idx, int dim) const {
                        return m_data_matrix.coeff(idx,dim);
                }

                // Optional bounding-box computation: return false to default to a standard bbox computation loop.
                //   Return true if the BBOX was already computed by the class and returned in "bb" so it can be avoided to redo it again.
                //   Look at bb.size() to find out the expected dimensionality (e.g. 2 or 3 for point clouds)
                template <class BBOX>
                bool kdtree_get_bbox(BBOX &bb) const {
                        return false;
                }

        }; // end of KDTreeEigenMatrixAdaptor // end of grouping
} // end of NS


#endif /* NANOFLANN_HPP_ */