Context Navigation

← Previous Revision
Latest Revision
Next Revision →
Blame
Revision Log

bd_tree.cpp @ 37

Last change on this file since 37 was 37, checked in by (none), 14 years ago
Added original make3d
File size: 15.8 KB

Line
1	//----------------------------------------------------------------------
2	// File: bd_tree.cpp
3	// Programmer: David Mount
4	// Description: Basic methods for bd-trees.
5	// Last modified: 01/04/05 (Version 1.0)
6	//----------------------------------------------------------------------
7	// Copyright (c) 1997-2005 University of Maryland and Sunil Arya and
8	// David Mount. All Rights Reserved.
9	//
10	// This software and related documentation is part of the Approximate
11	// Nearest Neighbor Library (ANN). This software is provided under
12	// the provisions of the Lesser GNU Public License (LGPL). See the
13	// file ../ReadMe.txt for further information.
14	//
15	// The University of Maryland (U.M.) and the authors make no
16	// representations about the suitability or fitness of this software for
17	// any purpose. It is provided "as is" without express or implied
18	// warranty.
19	//----------------------------------------------------------------------
20	// History:
21	// Revision 0.1 03/04/98
22	// Initial release
23	// Revision l.0 04/01/05
24	// Fixed centroid shrink threshold condition to depend on the
25	// dimension.
26	// Moved dump routine to kd_dump.cpp.
27	//----------------------------------------------------------------------
28
29	#include "bd_tree.h" // bd-tree declarations
30	#include "kd_util.h" // kd-tree utilities
31	#include "kd_split.h" // kd-tree splitting rules
32
33	#include <ANN/ANNperf.h> // performance evaluation
34
35	//----------------------------------------------------------------------
36	// Printing a bd-tree
37	// These routines print a bd-tree. See the analogous procedure
38	// in kd_tree.cpp for more information.
39	//----------------------------------------------------------------------
40
41	void ANNbd_shrink::print( // print shrinking node
42	int level, // depth of node in tree
43	ostream &out) // output stream
44	{
45	child[ANN_OUT]->print(level+1, out); // print out-child
46
47	out << " ";
48	for (int i = 0; i < level; i++) // print indentation
49	out << "..";
50	out << "Shrink";
51	for (int j = 0; j < n_bnds; j++) { // print sides, 2 per line
52	if (j % 2 == 0) {
53	out << "\n"; // newline and indentation
54	for (int i = 0; i < level+2; i++) out << " ";
55	}
56	out << " ([" << bnds[j].cd << "]"
57	<< (bnds[j].sd > 0 ? ">=" : "< ")
58	<< bnds[j].cv << ")";
59	}
60	out << "\n";
61
62	child[ANN_IN]->print(level+1, out); // print in-child
63	}
64
65	//----------------------------------------------------------------------
66	// kd_tree statistics utility (for performance evaluation)
67	// This routine computes various statistics information for
68	// shrinking nodes. See file kd_tree.cpp for more information.
69	//----------------------------------------------------------------------
70
71	void ANNbd_shrink::getStats( // get subtree statistics
72	int dim, // dimension of space
73	ANNkdStats &st, // stats (modified)
74	ANNorthRect &bnd_box) // bounding box
75	{
76	ANNkdStats ch_stats; // stats for children
77	ANNorthRect inner_box(dim); // inner box of shrink
78
79	annBnds2Box(bnd_box, // enclosing box
80	dim, // dimension
81	n_bnds, // number of bounds
82	bnds, // bounds array
83	inner_box); // inner box (modified)
84	// get stats for inner child
85	ch_stats.reset(); // reset
86	child[ANN_IN]->getStats(dim, ch_stats, inner_box);
87	st.merge(ch_stats); // merge them
88	// get stats for outer child
89	ch_stats.reset(); // reset
90	child[ANN_OUT]->getStats(dim, ch_stats, bnd_box);
91	st.merge(ch_stats); // merge them
92
93	st.depth++; // increment depth
94	st.n_shr++; // increment number of shrinks
95	}
96
97	//----------------------------------------------------------------------
98	// bd-tree constructor
99	// This is the main constructor for bd-trees given a set of points.
100	// It first builds a skeleton kd-tree as a basis, then computes the
101	// bounding box of the data points, and then invokes rbd_tree() to
102	// actually build the tree, passing it the appropriate splitting
103	// and shrinking information.
104	//----------------------------------------------------------------------
105
106	ANNkd_ptr rbd_tree( // recursive construction of bd-tree
107	ANNpointArray pa, // point array
108	ANNidxArray pidx, // point indices to store in subtree
109	int n, // number of points
110	int dim, // dimension of space
111	int bsp, // bucket space
112	ANNorthRect &bnd_box, // bounding box for current node
113	ANNkd_splitter splitter, // splitting routine
114	ANNshrinkRule shrink); // shrinking rule
115
116	ANNbd_tree::ANNbd_tree( // construct from point array
117	ANNpointArray pa, // point array (with at least n pts)
118	int n, // number of points
119	int dd, // dimension
120	int bs, // bucket size
121	ANNsplitRule split, // splitting rule
122	ANNshrinkRule shrink) // shrinking rule
123	: ANNkd_tree(n, dd, bs) // build skeleton base tree
124	{
125	pts = pa; // where the points are
126	if (n == 0) return; // no points--no sweat
127
128	ANNorthRect bnd_box(dd); // bounding box for points
129	// construct bounding rectangle
130	annEnclRect(pa, pidx, n, dd, bnd_box);
131	// copy to tree structure
132	bnd_box_lo = annCopyPt(dd, bnd_box.lo);
133	bnd_box_hi = annCopyPt(dd, bnd_box.hi);
134
135	switch (split) { // build by rule
136	case ANN_KD_STD: // standard kd-splitting rule
137	root = rbd_tree(pa, pidx, n, dd, bs, bnd_box, kd_split, shrink);
138	break;
139	case ANN_KD_MIDPT: // midpoint split
140	root = rbd_tree(pa, pidx, n, dd, bs, bnd_box, midpt_split, shrink);
141	break;
142	case ANN_KD_SUGGEST: // best (in our opinion)
143	case ANN_KD_SL_MIDPT: // sliding midpoint split
144	root = rbd_tree(pa, pidx, n, dd, bs, bnd_box, sl_midpt_split, shrink);
145	break;
146	case ANN_KD_FAIR: // fair split
147	root = rbd_tree(pa, pidx, n, dd, bs, bnd_box, fair_split, shrink);
148	break;
149	case ANN_KD_SL_FAIR: // sliding fair split
150	root = rbd_tree(pa, pidx, n, dd, bs,
151	bnd_box, sl_fair_split, shrink);
152	break;
153	default:
154	annError("Illegal splitting method", ANNabort);
155	}
156	}
157
158	//----------------------------------------------------------------------
159	// Shrinking rules
160	//----------------------------------------------------------------------
161
162	enum ANNdecomp {SPLIT, SHRINK}; // decomposition methods
163
164	//----------------------------------------------------------------------
165	// trySimpleShrink - Attempt a simple shrink
166	//
167	// We compute the tight bounding box of the points, and compute
168	// the 2*dim ``gaps'' between the sides of the tight box and the
169	// bounding box. If any of the gaps is large enough relative to
170	// the longest side of the tight bounding box, then we shrink
171	// all sides whose gaps are large enough. (The reason for
172	// comparing against the tight bounding box, is that after
173	// shrinking the longest box size will decrease, and if we use
174	// the standard bounding box, we may decide to shrink twice in
175	// a row. Since the tight box is fixed, we cannot shrink twice
176	// consecutively.)
177	//----------------------------------------------------------------------
178	const float BD_GAP_THRESH = 0.5; // gap threshold (must be < 1)
179	const int BD_CT_THRESH = 2; // min number of shrink sides
180
181	ANNdecomp trySimpleShrink( // try a simple shrink
182	ANNpointArray pa, // point array
183	ANNidxArray pidx, // point indices to store in subtree
184	int n, // number of points
185	int dim, // dimension of space
186	const ANNorthRect &bnd_box, // current bounding box
187	ANNorthRect &inner_box) // inner box if shrinking (returned)
188	{
189	int i;
190	// compute tight bounding box
191	annEnclRect(pa, pidx, n, dim, inner_box);
192
193	ANNcoord max_length = 0; // find longest box side
194	for (i = 0; i < dim; i++) {
195	ANNcoord length = inner_box.hi[i] - inner_box.lo[i];
196	if (length > max_length) {
197	max_length = length;
198	}
199	}
200
201	int shrink_ct = 0; // number of sides we shrunk
202	for (i = 0; i < dim; i++) { // select which sides to shrink
203	// gap between boxes
204	ANNcoord gap_hi = bnd_box.hi[i] - inner_box.hi[i];
205	// big enough gap to shrink?
206	if (gap_hi < max_length*BD_GAP_THRESH)
207	inner_box.hi[i] = bnd_box.hi[i]; // no - expand
208	else shrink_ct++; // yes - shrink this side
209
210	// repeat for high side
211	ANNcoord gap_lo = inner_box.lo[i] - bnd_box.lo[i];
212	if (gap_lo < max_length*BD_GAP_THRESH)
213	inner_box.lo[i] = bnd_box.lo[i]; // no - expand
214	else shrink_ct++; // yes - shrink this side
215	}
216
217	if (shrink_ct >= BD_CT_THRESH) // did we shrink enough sides?
218	return SHRINK;
219	else return SPLIT;
220	}
221
222	//----------------------------------------------------------------------
223	// tryCentroidShrink - Attempt a centroid shrink
224	//
225	// We repeatedly apply the splitting rule, always to the larger subset
226	// of points, until the number of points decreases by the constant
227	// fraction BD_FRACTION. If this takes more than dim*BD_MAX_SPLIT_FAC
228	// splits for this to happen, then we shrink to the final inner box
229	// Otherwise we split.
230	//----------------------------------------------------------------------
231
232	const float BD_MAX_SPLIT_FAC = 0.5; // maximum number of splits allowed
233	const float BD_FRACTION = 0.5; // ...to reduce points by this fraction
234	// ...This must be < 1.
235
236	ANNdecomp tryCentroidShrink( // try a centroid shrink
237	ANNpointArray pa, // point array
238	ANNidxArray pidx, // point indices to store in subtree
239	int n, // number of points
240	int dim, // dimension of space
241	const ANNorthRect &bnd_box, // current bounding box
242	ANNkd_splitter splitter, // splitting procedure
243	ANNorthRect &inner_box) // inner box if shrinking (returned)
244	{
245	int n_sub = n; // number of points in subset
246	int n_goal = (int) (n*BD_FRACTION); // number of point in goal
247	int n_splits = 0; // number of splits needed
248	// initialize inner box to bounding box
249	annAssignRect(dim, inner_box, bnd_box);
250
251	while (n_sub > n_goal) { // keep splitting until goal reached
252	int cd; // cut dim from splitter (ignored)
253	ANNcoord cv; // cut value from splitter (ignored)
254	int n_lo; // number of points on low side
255	// invoke splitting procedure
256	(*splitter)(pa, pidx, inner_box, n_sub, dim, cd, cv, n_lo);
257	n_splits++; // increment split count
258
259	if (n_lo >= n_sub/2) { // most points on low side
260	inner_box.hi[cd] = cv; // collapse high side
261	n_sub = n_lo; // recurse on lower points
262	}
263	else { // most points on high side
264	inner_box.lo[cd] = cv; // collapse low side
265	pidx += n_lo; // recurse on higher points
266	n_sub -= n_lo;
267	}
268	}
269	if (n_splits > dim*BD_MAX_SPLIT_FAC)// took too many splits
270	return SHRINK; // shrink to final subset
271	else
272	return SPLIT;
273	}
274
275	//----------------------------------------------------------------------
276	// selectDecomp - select which decomposition to use
277	//----------------------------------------------------------------------
278
279	ANNdecomp selectDecomp( // select decomposition method
280	ANNpointArray pa, // point array
281	ANNidxArray pidx, // point indices to store in subtree
282	int n, // number of points
283	int dim, // dimension of space
284	const ANNorthRect &bnd_box, // current bounding box
285	ANNkd_splitter splitter, // splitting procedure
286	ANNshrinkRule shrink, // shrinking rule
287	ANNorthRect &inner_box) // inner box if shrinking (returned)
288	{
289	ANNdecomp decomp = SPLIT; // decomposition
290
291	switch (shrink) { // check shrinking rule
292	case ANN_BD_NONE: // no shrinking allowed
293	decomp = SPLIT;
294	break;
295	case ANN_BD_SUGGEST: // author's suggestion
296	case ANN_BD_SIMPLE: // simple shrink
297	decomp = trySimpleShrink(
298	pa, pidx, // points and indices
299	n, dim, // number of points and dimension
300	bnd_box, // current bounding box
301	inner_box); // inner box if shrinking (returned)
302	break;
303	case ANN_BD_CENTROID: // centroid shrink
304	decomp = tryCentroidShrink(
305	pa, pidx, // points and indices
306	n, dim, // number of points and dimension
307	bnd_box, // current bounding box
308	splitter, // splitting procedure
309	inner_box); // inner box if shrinking (returned)
310	break;
311	default:
312	annError("Illegal shrinking rule", ANNabort);
313	}
314	return decomp;
315	}
316
317	//----------------------------------------------------------------------
318	// rbd_tree - recursive procedure to build a bd-tree
319	//
320	// This is analogous to rkd_tree, but for bd-trees. See the
321	// procedure rkd_tree() in kd_split.cpp for more information.
322	//
323	// If the number of points falls below the bucket size, then a
324	// leaf node is created for the points. Otherwise we invoke the
325	// procedure selectDecomp() which determines whether we are to
326	// split or shrink. If splitting is chosen, then we essentially
327	// do exactly as rkd_tree() would, and invoke the specified
328	// splitting procedure to the points. Otherwise, the selection
329	// procedure returns a bounding box, from which we extract the
330	// appropriate shrinking bounds, and create a shrinking node.
331	// Finally the points are subdivided, and the procedure is
332	// invoked recursively on the two subsets to form the children.
333	//----------------------------------------------------------------------
334
335	ANNkd_ptr rbd_tree( // recursive construction of bd-tree
336	ANNpointArray pa, // point array
337	ANNidxArray pidx, // point indices to store in subtree
338	int n, // number of points
339	int dim, // dimension of space
340	int bsp, // bucket space
341	ANNorthRect &bnd_box, // bounding box for current node
342	ANNkd_splitter splitter, // splitting routine
343	ANNshrinkRule shrink) // shrinking rule
344	{
345	ANNdecomp decomp; // decomposition method
346
347	ANNorthRect inner_box(dim); // inner box (if shrinking)
348
349	if (n <= bsp) { // n small, make a leaf node
350	if (n == 0) // empty leaf node
351	return KD_TRIVIAL; // return (canonical) empty leaf
352	else // construct the node and return
353	return new ANNkd_leaf(n, pidx);
354	}
355
356	decomp = selectDecomp( // select decomposition method
357	pa, pidx, // points and indices
358	n, dim, // number of points and dimension
359	bnd_box, // current bounding box
360	splitter, shrink, // splitting/shrinking methods
361	inner_box); // inner box if shrinking (returned)
362
363	if (decomp == SPLIT) { // split selected
364	int cd; // cutting dimension
365	ANNcoord cv; // cutting value
366	int n_lo; // number on low side of cut
367	// invoke splitting procedure
368	(*splitter)(pa, pidx, bnd_box, n, dim, cd, cv, n_lo);
369
370	ANNcoord lv = bnd_box.lo[cd]; // save bounds for cutting dimension
371	ANNcoord hv = bnd_box.hi[cd];
372
373	bnd_box.hi[cd] = cv; // modify bounds for left subtree
374	ANNkd_ptr lo = rbd_tree( // build left subtree
375	pa, pidx, n_lo, // ...from pidx[0..n_lo-1]
376	dim, bsp, bnd_box, splitter, shrink);
377	bnd_box.hi[cd] = hv; // restore bounds
378
379	bnd_box.lo[cd] = cv; // modify bounds for right subtree
380	ANNkd_ptr hi = rbd_tree( // build right subtree
381	pa, pidx + n_lo, n-n_lo,// ...from pidx[n_lo..n-1]
382	dim, bsp, bnd_box, splitter, shrink);
383	bnd_box.lo[cd] = lv; // restore bounds
384	// create the splitting node
385	return new ANNkd_split(cd, cv, lv, hv, lo, hi);
386	}
387	else { // shrink selected
388	int n_in; // number of points in box
389	int n_bnds; // number of bounding sides
390
391	annBoxSplit( // split points around inner box
392	pa, // points to split
393	pidx, // point indices
394	n, // number of points
395	dim, // dimension
396	inner_box, // inner box
397	n_in); // number of points inside (returned)
398
399	ANNkd_ptr in = rbd_tree( // build inner subtree pidx[0..n_in-1]
400	pa, pidx, n_in, dim, bsp, inner_box, splitter, shrink);
401	ANNkd_ptr out = rbd_tree( // build outer subtree pidx[n_in..n]
402	pa, pidx+n_in, n - n_in, dim, bsp, bnd_box, splitter, shrink);
403
404	ANNorthHSArray bnds = NULL; // bounds (alloc in Box2Bnds and
405	// ...freed in bd_shrink destroyer)
406
407	annBox2Bnds( // convert inner box to bounds
408	inner_box, // inner box
409	bnd_box, // enclosing box
410	dim, // dimension
411	n_bnds, // number of bounds (returned)
412	bnds); // bounds array (modified)
413
414	// return shrinking node
415	return new ANNbd_shrink(n_bnds, bnds, in, out);
416	}
417	}

Note: See TracBrowser for help on using the repository browser.

Context Navigation

source: proiecte/pmake3d/make3d_original/Make3dSingleImageStanford_version0.1/third_party/ann_1.1.1/src/bd_tree.cpp @ 37

Download in other formats: