diff options
Diffstat (limited to 'geom_bottleneck/bottleneck/src/ann/kd_pr_search.cpp')
| -rw-r--r-- | geom_bottleneck/bottleneck/src/ann/kd_pr_search.cpp | 221 |
1 files changed, 221 insertions, 0 deletions
diff --git a/geom_bottleneck/bottleneck/src/ann/kd_pr_search.cpp b/geom_bottleneck/bottleneck/src/ann/kd_pr_search.cpp new file mode 100644 index 0000000..73d643f --- /dev/null +++ b/geom_bottleneck/bottleneck/src/ann/kd_pr_search.cpp @@ -0,0 +1,221 @@ +//---------------------------------------------------------------------- +// File: kd_pr_search.cpp +// Programmer: Sunil Arya and David Mount +// Description: Priority search for kd-trees +// Last modified: 01/04/05 (Version 1.0) +//---------------------------------------------------------------------- +// 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 +//---------------------------------------------------------------------- + +#include "kd_pr_search.h" // kd priority search declarations + +namespace geom_bt { +//---------------------------------------------------------------------- +// Approximate nearest neighbor searching by priority search. +// The kd-tree is searched for an approximate nearest neighbor. +// The point is returned through one of the arguments, and the +// distance returned is the SQUARED distance to this point. +// +// The method used for searching the kd-tree is called priority +// search. (It is described in Arya and Mount, ``Algorithms for +// fast vector quantization,'' Proc. of DCC '93: Data Compression +// Conference}, eds. J. A. Storer and M. Cohn, IEEE Press, 1993, +// 381--390.) +// +// The cell of the kd-tree containing the query point is located, +// and cells are visited in increasing order of distance from the +// query point. This is done by placing each subtree which has +// NOT been visited in a priority queue, according to the closest +// distance of the corresponding enclosing rectangle from the +// query point. The search stops when the distance to the nearest +// remaining rectangle exceeds the distance to the nearest point +// seen by a factor of more than 1/(1+eps). (Implying that any +// point found subsequently in the search cannot be closer by more +// than this factor.) +// +// The main entry point is annkPriSearch() which sets things up and +// then call the recursive routine ann_pri_search(). This is a +// recursive routine which performs the processing for one node in +// the kd-tree. There are two versions of this virtual procedure, +// one for splitting nodes and one for leaves. When a splitting node +// is visited, we determine which child to continue the search on +// (the closer one), and insert the other child into the priority +// queue. When a leaf is visited, we compute the distances to the +// points in the buckets, and update information on the closest +// points. +// +// Some trickery is used to incrementally update the distance from +// a kd-tree rectangle to the query point. This comes about from +// the fact that which each successive split, only one component +// (along the dimension that is split) of the squared distance to +// the child rectangle is different from the squared distance to +// the parent rectangle. +//---------------------------------------------------------------------- + +//---------------------------------------------------------------------- +// To keep argument lists short, a number of global variables +// are maintained which are common to all the recursive calls. +// These are given below. +//---------------------------------------------------------------------- + +double ANNprEps; // the error bound +int ANNprDim; // dimension of space +ANNpoint ANNprQ; // query point +double ANNprMaxErr; // max tolerable squared error +ANNpointArray ANNprPts; // the points +ANNpr_queue *ANNprBoxPQ; // priority queue for boxes +ANNmin_k *ANNprPointMK; // set of k closest points + +//---------------------------------------------------------------------- +// annkPriSearch - priority search for k nearest neighbors +//---------------------------------------------------------------------- + +void ANNkd_tree::annkPriSearch( + ANNpoint q, // query point + int k, // number of near neighbors to return + ANNidxArray nn_idx, // nearest neighbor indices (returned) + ANNdistArray dd, // dist to near neighbors (returned) + double eps) // error bound (ignored) +{ + // max tolerable squared error + ANNprMaxErr = ANN_POW(1.0 + eps); + ANN_FLOP(2) // increment floating ops + + ANNprDim = dim; // copy arguments to static equivs + ANNprQ = q; + ANNprPts = pts; + ANNptsVisited = 0; // initialize count of points visited + + ANNprPointMK = new ANNmin_k(k); // create set for closest k points + + // distance to root box + ANNdist box_dist = annBoxDistance(q, + bnd_box_lo, bnd_box_hi, dim); + + ANNprBoxPQ = new ANNpr_queue(n_pts);// create priority queue for boxes + ANNprBoxPQ->insert(box_dist, root); // insert root in priority queue + + while (ANNprBoxPQ->non_empty() && + (!(ANNmaxPtsVisited != 0 && ANNptsVisited > ANNmaxPtsVisited))) { + ANNkd_ptr np; // next box from prior queue + + // extract closest box from queue + ANNprBoxPQ->extr_min(box_dist, (void *&) np); + + ANN_FLOP(2) // increment floating ops + if (box_dist*ANNprMaxErr >= ANNprPointMK->max_key()) + break; + + np->ann_pri_search(box_dist); // search this subtree. + } + + for (int i = 0; i < k; i++) { // extract the k-th closest points + dd[i] = ANNprPointMK->ith_smallest_key(i); + nn_idx[i] = ANNprPointMK->ith_smallest_info(i); + } + + delete ANNprPointMK; // deallocate closest point set + delete ANNprBoxPQ; // deallocate priority queue +} + +//---------------------------------------------------------------------- +// kd_split::ann_pri_search - search a splitting node +//---------------------------------------------------------------------- + +void ANNkd_split::ann_pri_search(ANNdist box_dist) +{ + ANNdist new_dist; // distance to child visited later + // distance to cutting plane + ANNcoord cut_diff = ANNprQ[cut_dim] - cut_val; + + if (cut_diff < 0) { // left of cutting plane + ANNcoord box_diff = cd_bnds[ANN_LO] - ANNprQ[cut_dim]; + if (box_diff < 0) // within bounds - ignore + box_diff = 0; + // distance to further box + new_dist = (ANNdist) ANN_SUM(box_dist, + ANN_DIFF(ANN_POW(box_diff), ANN_POW(cut_diff))); + + if (child[ANN_HI] != KD_TRIVIAL)// enqueue if not trivial + ANNprBoxPQ->insert(new_dist, child[ANN_HI]); + // continue with closer child + child[ANN_LO]->ann_pri_search(box_dist); + } + else { // right of cutting plane + ANNcoord box_diff = ANNprQ[cut_dim] - cd_bnds[ANN_HI]; + if (box_diff < 0) // within bounds - ignore + box_diff = 0; + // distance to further box + new_dist = (ANNdist) ANN_SUM(box_dist, + ANN_DIFF(ANN_POW(box_diff), ANN_POW(cut_diff))); + + if (child[ANN_LO] != KD_TRIVIAL)// enqueue if not trivial + ANNprBoxPQ->insert(new_dist, child[ANN_LO]); + // continue with closer child + child[ANN_HI]->ann_pri_search(box_dist); + } + ANN_SPL(1) // one more splitting node visited + ANN_FLOP(8) // increment floating ops +} + +//---------------------------------------------------------------------- +// kd_leaf::ann_pri_search - search points in a leaf node +// +// This is virtually identical to the ann_search for standard search. +//---------------------------------------------------------------------- + +void ANNkd_leaf::ann_pri_search(ANNdist box_dist) +{ + register ANNdist dist; // distance to data point + register ANNcoord* pp; // data coordinate pointer + register ANNcoord* qq; // query coordinate pointer + register ANNdist min_dist; // distance to k-th closest point + register ANNcoord t; + register int d; + + min_dist = ANNprPointMK->max_key(); // k-th smallest distance so far + + for (int i = 0; i < n_pts; i++) { // check points in bucket + + pp = ANNprPts[bkt[i]]; // first coord of next data point + qq = ANNprQ; // first coord of query point + dist = 0; + + for(d = 0; d < ANNprDim; d++) { + ANN_COORD(1) // one more coordinate hit + ANN_FLOP(4) // increment floating ops + + t = *(qq++) - *(pp++); // compute length and adv coordinate + // exceeds dist to k-th smallest? + if( (dist = ANN_SUM(dist, ANN_POW(t))) > min_dist) { + break; + } + } + + if (d >= ANNprDim && // among the k best? + (ANN_ALLOW_SELF_MATCH || dist!=0)) { // and no self-match problem + // add it to the list + ANNprPointMK->insert(dist, bkt[i]); + min_dist = ANNprPointMK->max_key(); + } + } + ANN_LEAF(1) // one more leaf node visited + ANN_PTS(n_pts) // increment points visited + ANNptsVisited += n_pts; // increment number of points visited +} +} |