kd_tree.h

Go to the documentation of this file.

//----------------------------------------------------------------------
// File:                        kd_tree.h
// Programmer:          Sunil Arya and David Mount
// Description:         Declarations for standard kd-tree routines
// Last modified:       05/03/05 (Version 1.1)
//----------------------------------------------------------------------
// Copyright (c) 1997-2005 University of Maryland and Sunil Arya and
// David Mount.  All Rights Reserved.
//
// This software and related documentation is part of the Approximate
// Nearest Neighbor Library (ANN).  This software is provided under
// the provisions of the Lesser GNU Public License (LGPL).  See the
// file ../ReadMe.txt for further information.
//
// The University of Maryland (U.M.) and the authors make no
// representations about the suitability or fitness of this software for
// any purpose.  It is provided "as is" without express or implied
// warranty.
//----------------------------------------------------------------------
// History:
//      Revision 0.1  03/04/98
//              Initial release
//      Revision 1.1  05/03/05
//              Added fixed radius kNN search
//----------------------------------------------------------------------

#ifndef ANN_kd_tree_H
#define ANN_kd_tree_H

#include <ANN/ANNx.h>                                   // all ANN includes

using namespace std;                                    // make std:: available

//----------------------------------------------------------------------
//      Generic kd-tree node
//
//              Nodes in kd-trees are of two types, splitting nodes which contain
//              splitting information (a splitting hyperplane orthogonal to one
//              of the coordinate axes) and leaf nodes which contain point
//              information (an array of points stored in a bucket).  This is
//              handled by making a generic class kd_node, which is essentially an
//              empty shell, and then deriving the leaf and splitting nodes from
//              this.
//----------------------------------------------------------------------

class ANNkd_node{                                               // generic kd-tree node (empty shell)
public:
        virtual ~ANNkd_node() {}                                        // virtual distroyer

        virtual void ann_search(ANNdist) = 0;           // tree search
        virtual void ann_pri_search(ANNdist) = 0;       // priority search
        virtual void ann_FR_search(ANNdist) = 0;        // fixed-radius search

        virtual void getStats(                                          // get tree statistics
                                int dim,                                                // dimension of space
                                ANNkdStats &st,                                 // statistics
                                ANNorthRect &bnd_box) = 0;              // bounding box
                                                                                                // print node
        virtual void print(int level, ostream &out) = 0;
        virtual void dump(ostream &out) = 0;            // dump node

        friend class ANNkd_tree;                                        // allow kd-tree to access us
};

//----------------------------------------------------------------------
//      kd-splitting function:
//              kd_splitter is a pointer to a splitting routine for preprocessing.
//              Different splitting procedures result in different strategies
//              for building the tree.
//----------------------------------------------------------------------

typedef void (*ANNkd_splitter)(                 // splitting routine for kd-trees
        ANNpointArray           pa,                             // point array (unaltered)
        ANNidxArray                     pidx,                   // point indices (permuted on return)
        const ANNorthRect       &bnds,                  // bounding rectangle for cell
        int                                     n,                              // number of points
        int                                     dim,                    // dimension of space
        int                                     &cut_dim,               // cutting dimension (returned)
        ANNcoord                        &cut_val,               // cutting value (returned)
        int                                     &n_lo);                 // num of points on low side (returned)

//----------------------------------------------------------------------
//      Leaf kd-tree node
//              Leaf nodes of the kd-tree store the set of points associated
//              with this bucket, stored as an array of point indices.  These
//              are indices in the array points, which resides with the
//              root of the kd-tree.  We also store the number of points
//              that reside in this bucket.
//----------------------------------------------------------------------

class ANNkd_leaf: public ANNkd_node             // leaf node for kd-tree
{
        int                                     n_pts;                  // no. points in bucket
        ANNidxArray                     bkt;                    // bucket of points
public:
        ANNkd_leaf(                                                     // constructor
                int                             n,                              // number of points
                ANNidxArray             b)                              // bucket
                {
                        n_pts           = n;                    // number of points in bucket
                        bkt                     = b;                    // the bucket
                }

        ~ANNkd_leaf() { }                                       // destructor (none)

        virtual void getStats(                                          // get tree statistics
                                int dim,                                                // dimension of space
                                ANNkdStats &st,                                 // statistics
                                ANNorthRect &bnd_box);                  // bounding box
        virtual void print(int level, ostream &out);// print node
        virtual void dump(ostream &out);                        // dump node

        virtual void ann_search(ANNdist);                       // standard search
        virtual void ann_pri_search(ANNdist);           // priority search
        virtual void ann_FR_search(ANNdist);            // fixed-radius search
};

//----------------------------------------------------------------------
//              KD_TRIVIAL is a special pointer to an empty leaf node. Since
//              some splitting rules generate many (more than 50%) trivial
//              leaves, we use this one shared node to save space.
//
//              The pointer is initialized to NULL, but whenever a kd-tree is
//              created, we allocate this node, if it has not already been
//              allocated. This node is *never* deallocated, so it produces
//              a small memory leak.
//----------------------------------------------------------------------

extern ANNkd_leaf *KD_TRIVIAL;                                  // trivial (empty) leaf node

//----------------------------------------------------------------------
//      kd-tree splitting node.
//              Splitting nodes contain a cutting dimension and a cutting value.
//              These indicate the axis-parellel plane which subdivide the
//              box for this node. The extent of the bounding box along the
//              cutting dimension is maintained (this is used to speed up point
//              to box distance calculations) [we do not store the entire bounding
//              box since this may be wasteful of space in high dimensions].
//              We also store pointers to the 2 children.
//----------------------------------------------------------------------

class ANNkd_split : public ANNkd_node   // splitting node of a kd-tree
{
        int                                     cut_dim;                // dim orthogonal to cutting plane
        ANNcoord                        cut_val;                // location of cutting plane
        ANNcoord                        cd_bnds[2];             // lower and upper bounds of
                                                                                // rectangle along cut_dim
        ANNkd_ptr                       child[2];               // left and right children
public:
        ANNkd_split(                                            // constructor
                int cd,                                                 // cutting dimension
                ANNcoord cv,                                    // cutting value
                ANNcoord lv, ANNcoord hv,                               // low and high values
                ANNkd_ptr lc=NULL, ANNkd_ptr hc=NULL)   // children
                {
                        cut_dim         = cd;                                   // cutting dimension
                        cut_val         = cv;                                   // cutting value
                        cd_bnds[ANN_LO] = lv;                           // lower bound for rectangle
                        cd_bnds[ANN_HI] = hv;                           // upper bound for rectangle
                        child[ANN_LO]   = lc;                           // left child
                        child[ANN_HI]   = hc;                           // right child
                }

        ~ANNkd_split()                                          // destructor
                {
                        if (child[ANN_LO]!= NULL && child[ANN_LO]!= KD_TRIVIAL)
                                delete child[ANN_LO];
                        if (child[ANN_HI]!= NULL && child[ANN_HI]!= KD_TRIVIAL)
                                delete child[ANN_HI];
                }

        virtual void getStats(                                          // get tree statistics
                                int dim,                                                // dimension of space
                                ANNkdStats &st,                                 // statistics
                                ANNorthRect &bnd_box);                  // bounding box
        virtual void print(int level, ostream &out);// print node
        virtual void dump(ostream &out);                        // dump node

        virtual void ann_search(ANNdist);                       // standard search
        virtual void ann_pri_search(ANNdist);           // priority search
        virtual void ann_FR_search(ANNdist);            // fixed-radius search
};

//----------------------------------------------------------------------
//              External entry points
//----------------------------------------------------------------------

ANNkd_ptr rkd_tree(                             // recursive construction of kd-tree
        ANNpointArray           pa,                             // point array (unaltered)
        ANNidxArray                     pidx,                   // point indices to store in subtree
        int                                     n,                              // number of points
        int                                     dim,                    // dimension of space
        int                                     bsp,                    // bucket space
        ANNorthRect                     &bnd_box,               // bounding box for current node
        ANNkd_splitter          splitter);              // splitting routine

#endif