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Diffstat (limited to 'geom_bottleneck/bottleneck/src/ann/bd_tree.cpp')
| -rw-r--r-- | geom_bottleneck/bottleneck/src/ann/bd_tree.cpp | 419 |
1 files changed, 419 insertions, 0 deletions
diff --git a/geom_bottleneck/bottleneck/src/ann/bd_tree.cpp b/geom_bottleneck/bottleneck/src/ann/bd_tree.cpp new file mode 100644 index 0000000..8c1ef6d --- /dev/null +++ b/geom_bottleneck/bottleneck/src/ann/bd_tree.cpp @@ -0,0 +1,419 @@ +//---------------------------------------------------------------------- +// File: bd_tree.cpp +// Programmer: David Mount +// Description: Basic methods for bd-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 +// Revision l.0 04/01/05 +// Fixed centroid shrink threshold condition to depend on the +// dimension. +// Moved dump routine to kd_dump.cpp. +//---------------------------------------------------------------------- + +#include "bd_tree.h" // bd-tree declarations +#include "kd_util.h" // kd-tree utilities +#include "kd_split.h" // kd-tree splitting rules + +#include <ANN/ANNperf.h> // performance evaluation + +namespace geom_bt { +//---------------------------------------------------------------------- +// Printing a bd-tree +// These routines print a bd-tree. See the analogous procedure +// in kd_tree.cpp for more information. +//---------------------------------------------------------------------- + +void ANNbd_shrink::print( // print shrinking node + int level, // depth of node in tree + ostream &out) // output stream +{ + child[ANN_OUT]->print(level+1, out); // print out-child + + out << " "; + for (int i = 0; i < level; i++) // print indentation + out << ".."; + out << "Shrink"; + for (int j = 0; j < n_bnds; j++) { // print sides, 2 per line + if (j % 2 == 0) { + out << "\n"; // newline and indentation + for (int i = 0; i < level+2; i++) out << " "; + } + out << " ([" << bnds[j].cd << "]" + << (bnds[j].sd > 0 ? ">=" : "< ") + << bnds[j].cv << ")"; + } + out << "\n"; + + child[ANN_IN]->print(level+1, out); // print in-child +} + +//---------------------------------------------------------------------- +// kd_tree statistics utility (for performance evaluation) +// This routine computes various statistics information for +// shrinking nodes. See file kd_tree.cpp for more information. +//---------------------------------------------------------------------- + +void ANNbd_shrink::getStats( // get subtree statistics + int dim, // dimension of space + ANNkdStats &st, // stats (modified) + ANNorthRect &bnd_box) // bounding box +{ + ANNkdStats ch_stats; // stats for children + ANNorthRect inner_box(dim); // inner box of shrink + + annBnds2Box(bnd_box, // enclosing box + dim, // dimension + n_bnds, // number of bounds + bnds, // bounds array + inner_box); // inner box (modified) + // get stats for inner child + ch_stats.reset(); // reset + child[ANN_IN]->getStats(dim, ch_stats, inner_box); + st.merge(ch_stats); // merge them + // get stats for outer child + ch_stats.reset(); // reset + child[ANN_OUT]->getStats(dim, ch_stats, bnd_box); + st.merge(ch_stats); // merge them + + st.depth++; // increment depth + st.n_shr++; // increment number of shrinks +} + +//---------------------------------------------------------------------- +// bd-tree constructor +// This is the main constructor for bd-trees given a set of points. +// It first builds a skeleton kd-tree as a basis, then computes the +// bounding box of the data points, and then invokes rbd_tree() to +// actually build the tree, passing it the appropriate splitting +// and shrinking information. +//---------------------------------------------------------------------- + +ANNkd_ptr rbd_tree( // recursive construction of bd-tree + ANNpointArray pa, // point array + 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 + ANNshrinkRule shrink); // shrinking rule + +ANNbd_tree::ANNbd_tree( // construct from point array + ANNpointArray pa, // point array (with at least n pts) + int n, // number of points + int dd, // dimension + int bs, // bucket size + ANNsplitRule split, // splitting rule + ANNshrinkRule shrink) // shrinking rule + : ANNkd_tree(n, dd, bs) // build skeleton base tree +{ + pts = pa; // where the points are + if (n == 0) return; // no points--no sweat + + ANNorthRect bnd_box(dd); // bounding box for points + // construct bounding rectangle + annEnclRect(pa, pidx, n, dd, bnd_box); + // copy to tree structure + bnd_box_lo = annCopyPt(dd, bnd_box.lo); + bnd_box_hi = annCopyPt(dd, bnd_box.hi); + + switch (split) { // build by rule + case ANN_KD_STD: // standard kd-splitting rule + root = rbd_tree(pa, pidx, n, dd, bs, bnd_box, kd_split, shrink); + break; + case ANN_KD_MIDPT: // midpoint split + root = rbd_tree(pa, pidx, n, dd, bs, bnd_box, midpt_split, shrink); + break; + case ANN_KD_SUGGEST: // best (in our opinion) + case ANN_KD_SL_MIDPT: // sliding midpoint split + root = rbd_tree(pa, pidx, n, dd, bs, bnd_box, sl_midpt_split, shrink); + break; + case ANN_KD_FAIR: // fair split + root = rbd_tree(pa, pidx, n, dd, bs, bnd_box, fair_split, shrink); + break; + case ANN_KD_SL_FAIR: // sliding fair split + root = rbd_tree(pa, pidx, n, dd, bs, + bnd_box, sl_fair_split, shrink); + break; + default: + annError("Illegal splitting method", ANNabort); + } +} + +//---------------------------------------------------------------------- +// Shrinking rules +//---------------------------------------------------------------------- + +enum ANNdecomp {SPLIT, SHRINK}; // decomposition methods + +//---------------------------------------------------------------------- +// trySimpleShrink - Attempt a simple shrink +// +// We compute the tight bounding box of the points, and compute +// the 2*dim ``gaps'' between the sides of the tight box and the +// bounding box. If any of the gaps is large enough relative to +// the longest side of the tight bounding box, then we shrink +// all sides whose gaps are large enough. (The reason for +// comparing against the tight bounding box, is that after +// shrinking the longest box size will decrease, and if we use +// the standard bounding box, we may decide to shrink twice in +// a row. Since the tight box is fixed, we cannot shrink twice +// consecutively.) +//---------------------------------------------------------------------- +const float BD_GAP_THRESH = 0.5; // gap threshold (must be < 1) +const int BD_CT_THRESH = 2; // min number of shrink sides + +ANNdecomp trySimpleShrink( // try a simple shrink + ANNpointArray pa, // point array + ANNidxArray pidx, // point indices to store in subtree + int n, // number of points + int dim, // dimension of space + const ANNorthRect &bnd_box, // current bounding box + ANNorthRect &inner_box) // inner box if shrinking (returned) +{ + int i; + // compute tight bounding box + annEnclRect(pa, pidx, n, dim, inner_box); + + ANNcoord max_length = 0; // find longest box side + for (i = 0; i < dim; i++) { + ANNcoord length = inner_box.hi[i] - inner_box.lo[i]; + if (length > max_length) { + max_length = length; + } + } + + int shrink_ct = 0; // number of sides we shrunk + for (i = 0; i < dim; i++) { // select which sides to shrink + // gap between boxes + ANNcoord gap_hi = bnd_box.hi[i] - inner_box.hi[i]; + // big enough gap to shrink? + if (gap_hi < max_length*BD_GAP_THRESH) + inner_box.hi[i] = bnd_box.hi[i]; // no - expand + else shrink_ct++; // yes - shrink this side + + // repeat for high side + ANNcoord gap_lo = inner_box.lo[i] - bnd_box.lo[i]; + if (gap_lo < max_length*BD_GAP_THRESH) + inner_box.lo[i] = bnd_box.lo[i]; // no - expand + else shrink_ct++; // yes - shrink this side + } + + if (shrink_ct >= BD_CT_THRESH) // did we shrink enough sides? + return SHRINK; + else return SPLIT; +} + +//---------------------------------------------------------------------- +// tryCentroidShrink - Attempt a centroid shrink +// +// We repeatedly apply the splitting rule, always to the larger subset +// of points, until the number of points decreases by the constant +// fraction BD_FRACTION. If this takes more than dim*BD_MAX_SPLIT_FAC +// splits for this to happen, then we shrink to the final inner box +// Otherwise we split. +//---------------------------------------------------------------------- + +const float BD_MAX_SPLIT_FAC = 0.5; // maximum number of splits allowed +const float BD_FRACTION = 0.5; // ...to reduce points by this fraction + // ...This must be < 1. + +ANNdecomp tryCentroidShrink( // try a centroid shrink + ANNpointArray pa, // point array + ANNidxArray pidx, // point indices to store in subtree + int n, // number of points + int dim, // dimension of space + const ANNorthRect &bnd_box, // current bounding box + ANNkd_splitter splitter, // splitting procedure + ANNorthRect &inner_box) // inner box if shrinking (returned) +{ + int n_sub = n; // number of points in subset + int n_goal = (int) (n*BD_FRACTION); // number of point in goal + int n_splits = 0; // number of splits needed + // initialize inner box to bounding box + annAssignRect(dim, inner_box, bnd_box); + + while (n_sub > n_goal) { // keep splitting until goal reached + int cd; // cut dim from splitter (ignored) + ANNcoord cv; // cut value from splitter (ignored) + int n_lo; // number of points on low side + // invoke splitting procedure + (*splitter)(pa, pidx, inner_box, n_sub, dim, cd, cv, n_lo); + n_splits++; // increment split count + + if (n_lo >= n_sub/2) { // most points on low side + inner_box.hi[cd] = cv; // collapse high side + n_sub = n_lo; // recurse on lower points + } + else { // most points on high side + inner_box.lo[cd] = cv; // collapse low side + pidx += n_lo; // recurse on higher points + n_sub -= n_lo; + } + } + if (n_splits > dim*BD_MAX_SPLIT_FAC)// took too many splits + return SHRINK; // shrink to final subset + else + return SPLIT; +} + +//---------------------------------------------------------------------- +// selectDecomp - select which decomposition to use +//---------------------------------------------------------------------- + +ANNdecomp selectDecomp( // select decomposition method + ANNpointArray pa, // point array + ANNidxArray pidx, // point indices to store in subtree + int n, // number of points + int dim, // dimension of space + const ANNorthRect &bnd_box, // current bounding box + ANNkd_splitter splitter, // splitting procedure + ANNshrinkRule shrink, // shrinking rule + ANNorthRect &inner_box) // inner box if shrinking (returned) +{ + ANNdecomp decomp = SPLIT; // decomposition + + switch (shrink) { // check shrinking rule + case ANN_BD_NONE: // no shrinking allowed + decomp = SPLIT; + break; + case ANN_BD_SUGGEST: // author's suggestion + case ANN_BD_SIMPLE: // simple shrink + decomp = trySimpleShrink( + pa, pidx, // points and indices + n, dim, // number of points and dimension + bnd_box, // current bounding box + inner_box); // inner box if shrinking (returned) + break; + case ANN_BD_CENTROID: // centroid shrink + decomp = tryCentroidShrink( + pa, pidx, // points and indices + n, dim, // number of points and dimension + bnd_box, // current bounding box + splitter, // splitting procedure + inner_box); // inner box if shrinking (returned) + break; + default: + annError("Illegal shrinking rule", ANNabort); + } + return decomp; +} + +//---------------------------------------------------------------------- +// rbd_tree - recursive procedure to build a bd-tree +// +// This is analogous to rkd_tree, but for bd-trees. See the +// procedure rkd_tree() in kd_split.cpp for more information. +// +// If the number of points falls below the bucket size, then a +// leaf node is created for the points. Otherwise we invoke the +// procedure selectDecomp() which determines whether we are to +// split or shrink. If splitting is chosen, then we essentially +// do exactly as rkd_tree() would, and invoke the specified +// splitting procedure to the points. Otherwise, the selection +// procedure returns a bounding box, from which we extract the +// appropriate shrinking bounds, and create a shrinking node. +// Finally the points are subdivided, and the procedure is +// invoked recursively on the two subsets to form the children. +//---------------------------------------------------------------------- + +ANNkd_ptr rbd_tree( // recursive construction of bd-tree + ANNpointArray pa, // point array + 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 + ANNshrinkRule shrink) // shrinking rule +{ + ANNdecomp decomp; // decomposition method + + ANNorthRect inner_box(dim); // inner box (if shrinking) + + if (n <= bsp) { // n small, make a leaf node + if (n == 0) // empty leaf node + return KD_TRIVIAL; // return (canonical) empty leaf + else // construct the node and return + return new ANNkd_leaf(n, pidx); + } + + decomp = selectDecomp( // select decomposition method + pa, pidx, // points and indices + n, dim, // number of points and dimension + bnd_box, // current bounding box + splitter, shrink, // splitting/shrinking methods + inner_box); // inner box if shrinking (returned) + + if (decomp == SPLIT) { // split selected + int cd; // cutting dimension + ANNcoord cv; // cutting value + int n_lo; // number on low side of cut + // invoke splitting procedure + (*splitter)(pa, pidx, bnd_box, n, dim, cd, cv, n_lo); + + ANNcoord lv = bnd_box.lo[cd]; // save bounds for cutting dimension + ANNcoord hv = bnd_box.hi[cd]; + + bnd_box.hi[cd] = cv; // modify bounds for left subtree + ANNkd_ptr lo = rbd_tree( // build left subtree + pa, pidx, n_lo, // ...from pidx[0..n_lo-1] + dim, bsp, bnd_box, splitter, shrink); + bnd_box.hi[cd] = hv; // restore bounds + + bnd_box.lo[cd] = cv; // modify bounds for right subtree + ANNkd_ptr hi = rbd_tree( // build right subtree + pa, pidx + n_lo, n-n_lo,// ...from pidx[n_lo..n-1] + dim, bsp, bnd_box, splitter, shrink); + bnd_box.lo[cd] = lv; // restore bounds + // create the splitting node + return new ANNkd_split(cd, cv, lv, hv, lo, hi); + } + else { // shrink selected + int n_in; // number of points in box + int n_bnds; // number of bounding sides + + annBoxSplit( // split points around inner box + pa, // points to split + pidx, // point indices + n, // number of points + dim, // dimension + inner_box, // inner box + n_in); // number of points inside (returned) + + ANNkd_ptr in = rbd_tree( // build inner subtree pidx[0..n_in-1] + pa, pidx, n_in, dim, bsp, inner_box, splitter, shrink); + ANNkd_ptr out = rbd_tree( // build outer subtree pidx[n_in..n] + pa, pidx+n_in, n - n_in, dim, bsp, bnd_box, splitter, shrink); + + ANNorthHSArray bnds = NULL; // bounds (alloc in Box2Bnds and + // ...freed in bd_shrink destroyer) + + annBox2Bnds( // convert inner box to bounds + inner_box, // inner box + bnd_box, // enclosing box + dim, // dimension + n_bnds, // number of bounds (returned) + bnds); // bounds array (modified) + + // return shrinking node + return new ANNbd_shrink(n_bnds, bnds, in, out); + } +} +} |