Libav
elbg.c
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1 /*
2  * Copyright (C) 2007 Vitor Sessak <vitor1001@gmail.com>
3  *
4  * This file is part of Libav.
5  *
6  * Libav is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU Lesser General Public
8  * License as published by the Free Software Foundation; either
9  * version 2.1 of the License, or (at your option) any later version.
10  *
11  * Libav is distributed in the hope that it will be useful,
12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14  * Lesser General Public License for more details.
15  *
16  * You should have received a copy of the GNU Lesser General Public
17  * License along with Libav; if not, write to the Free Software
18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
19  */
20 
26 #include <string.h>
27 
28 #include "libavutil/common.h"
29 #include "libavutil/lfg.h"
30 #include "elbg.h"
31 #include "avcodec.h"
32 
33 #define DELTA_ERR_MAX 0.1
34 
35 
38 typedef struct cell_s {
39  int index;
40  struct cell_s *next;
41 } cell;
42 
46 typedef struct{
47  int error;
48  int dim;
49  int numCB;
50  int *codebook;
52  int *utility;
54  int *nearest_cb;
55  int *points;
57  int *scratchbuf;
58 } elbg_data;
59 
60 static inline int distance_limited(int *a, int *b, int dim, int limit)
61 {
62  int i, dist=0;
63  for (i=0; i<dim; i++) {
64  dist += (a[i] - b[i])*(a[i] - b[i]);
65  if (dist > limit)
66  return INT_MAX;
67  }
68 
69  return dist;
70 }
71 
72 static inline void vect_division(int *res, int *vect, int div, int dim)
73 {
74  int i;
75  if (div > 1)
76  for (i=0; i<dim; i++)
77  res[i] = ROUNDED_DIV(vect[i],div);
78  else if (res != vect)
79  memcpy(res, vect, dim*sizeof(int));
80 
81 }
82 
83 static int eval_error_cell(elbg_data *elbg, int *centroid, cell *cells)
84 {
85  int error=0;
86  for (; cells; cells=cells->next)
87  error += distance_limited(centroid, elbg->points + cells->index*elbg->dim, elbg->dim, INT_MAX);
88 
89  return error;
90 }
91 
92 static int get_closest_codebook(elbg_data *elbg, int index)
93 {
94  int i, pick=0, diff, diff_min = INT_MAX;
95  for (i=0; i<elbg->numCB; i++)
96  if (i != index) {
97  diff = distance_limited(elbg->codebook + i*elbg->dim, elbg->codebook + index*elbg->dim, elbg->dim, diff_min);
98  if (diff < diff_min) {
99  pick = i;
100  diff_min = diff;
101  }
102  }
103  return pick;
104 }
105 
107 {
108  int i=0;
109  /* Using linear search, do binary if it ever turns to be speed critical */
110  int r = av_lfg_get(elbg->rand_state)%elbg->utility_inc[elbg->numCB-1] + 1;
111  while (elbg->utility_inc[i] < r)
112  i++;
113 
114  assert(elbg->cells[i]);
115 
116  return i;
117 }
118 
122 static int simple_lbg(elbg_data *elbg,
123  int dim,
124  int *centroid[3],
125  int newutility[3],
126  int *points,
127  cell *cells)
128 {
129  int i, idx;
130  int numpoints[2] = {0,0};
131  int *newcentroid[2] = {
132  elbg->scratchbuf + 3*dim,
133  elbg->scratchbuf + 4*dim
134  };
135  cell *tempcell;
136 
137  memset(newcentroid[0], 0, 2 * dim * sizeof(*newcentroid[0]));
138 
139  newutility[0] =
140  newutility[1] = 0;
141 
142  for (tempcell = cells; tempcell; tempcell=tempcell->next) {
143  idx = distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX)>=
144  distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX);
145  numpoints[idx]++;
146  for (i=0; i<dim; i++)
147  newcentroid[idx][i] += points[tempcell->index*dim + i];
148  }
149 
150  vect_division(centroid[0], newcentroid[0], numpoints[0], dim);
151  vect_division(centroid[1], newcentroid[1], numpoints[1], dim);
152 
153  for (tempcell = cells; tempcell; tempcell=tempcell->next) {
154  int dist[2] = {distance_limited(centroid[0], points + tempcell->index*dim, dim, INT_MAX),
155  distance_limited(centroid[1], points + tempcell->index*dim, dim, INT_MAX)};
156  int idx = dist[0] > dist[1];
157  newutility[idx] += dist[idx];
158  }
159 
160  return newutility[0] + newutility[1];
161 }
162 
163 static void get_new_centroids(elbg_data *elbg, int huc, int *newcentroid_i,
164  int *newcentroid_p)
165 {
166  cell *tempcell;
167  int *min = newcentroid_i;
168  int *max = newcentroid_p;
169  int i;
170 
171  for (i=0; i< elbg->dim; i++) {
172  min[i]=INT_MAX;
173  max[i]=0;
174  }
175 
176  for (tempcell = elbg->cells[huc]; tempcell; tempcell = tempcell->next)
177  for(i=0; i<elbg->dim; i++) {
178  min[i]=FFMIN(min[i], elbg->points[tempcell->index*elbg->dim + i]);
179  max[i]=FFMAX(max[i], elbg->points[tempcell->index*elbg->dim + i]);
180  }
181 
182  for (i=0; i<elbg->dim; i++) {
183  int ni = min[i] + (max[i] - min[i])/3;
184  int np = min[i] + (2*(max[i] - min[i]))/3;
185  newcentroid_i[i] = ni;
186  newcentroid_p[i] = np;
187  }
188 }
189 
199 static void shift_codebook(elbg_data *elbg, int *indexes,
200  int *newcentroid[3])
201 {
202  cell *tempdata;
203  cell **pp = &elbg->cells[indexes[2]];
204 
205  while(*pp)
206  pp= &(*pp)->next;
207 
208  *pp = elbg->cells[indexes[0]];
209 
210  elbg->cells[indexes[0]] = NULL;
211  tempdata = elbg->cells[indexes[1]];
212  elbg->cells[indexes[1]] = NULL;
213 
214  while(tempdata) {
215  cell *tempcell2 = tempdata->next;
216  int idx = distance_limited(elbg->points + tempdata->index*elbg->dim,
217  newcentroid[0], elbg->dim, INT_MAX) >
218  distance_limited(elbg->points + tempdata->index*elbg->dim,
219  newcentroid[1], elbg->dim, INT_MAX);
220 
221  tempdata->next = elbg->cells[indexes[idx]];
222  elbg->cells[indexes[idx]] = tempdata;
223  tempdata = tempcell2;
224  }
225 }
226 
227 static void evaluate_utility_inc(elbg_data *elbg)
228 {
229  int i, inc=0;
230 
231  for (i=0; i < elbg->numCB; i++) {
232  if (elbg->numCB*elbg->utility[i] > elbg->error)
233  inc += elbg->utility[i];
234  elbg->utility_inc[i] = inc;
235  }
236 }
237 
238 
239 static void update_utility_and_n_cb(elbg_data *elbg, int idx, int newutility)
240 {
241  cell *tempcell;
242 
243  elbg->utility[idx] = newutility;
244  for (tempcell=elbg->cells[idx]; tempcell; tempcell=tempcell->next)
245  elbg->nearest_cb[tempcell->index] = idx;
246 }
247 
255 static void try_shift_candidate(elbg_data *elbg, int idx[3])
256 {
257  int j, k, olderror=0, newerror, cont=0;
258  int newutility[3];
259  int *newcentroid[3] = {
260  elbg->scratchbuf,
261  elbg->scratchbuf + elbg->dim,
262  elbg->scratchbuf + 2*elbg->dim
263  };
264  cell *tempcell;
265 
266  for (j=0; j<3; j++)
267  olderror += elbg->utility[idx[j]];
268 
269  memset(newcentroid[2], 0, elbg->dim*sizeof(int));
270 
271  for (k=0; k<2; k++)
272  for (tempcell=elbg->cells[idx[2*k]]; tempcell; tempcell=tempcell->next) {
273  cont++;
274  for (j=0; j<elbg->dim; j++)
275  newcentroid[2][j] += elbg->points[tempcell->index*elbg->dim + j];
276  }
277 
278  vect_division(newcentroid[2], newcentroid[2], cont, elbg->dim);
279 
280  get_new_centroids(elbg, idx[1], newcentroid[0], newcentroid[1]);
281 
282  newutility[2] = eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[0]]);
283  newutility[2] += eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[2]]);
284 
285  newerror = newutility[2];
286 
287  newerror += simple_lbg(elbg, elbg->dim, newcentroid, newutility, elbg->points,
288  elbg->cells[idx[1]]);
289 
290  if (olderror > newerror) {
291  shift_codebook(elbg, idx, newcentroid);
292 
293  elbg->error += newerror - olderror;
294 
295  for (j=0; j<3; j++)
296  update_utility_and_n_cb(elbg, idx[j], newutility[j]);
297 
298  evaluate_utility_inc(elbg);
299  }
300  }
301 
305 static void do_shiftings(elbg_data *elbg)
306 {
307  int idx[3];
308 
309  evaluate_utility_inc(elbg);
310 
311  for (idx[0]=0; idx[0] < elbg->numCB; idx[0]++)
312  if (elbg->numCB*elbg->utility[idx[0]] < elbg->error) {
313  if (elbg->utility_inc[elbg->numCB-1] == 0)
314  return;
315 
316  idx[1] = get_high_utility_cell(elbg);
317  idx[2] = get_closest_codebook(elbg, idx[0]);
318 
319  if (idx[1] != idx[0] && idx[1] != idx[2])
320  try_shift_candidate(elbg, idx);
321  }
322 }
323 
324 #define BIG_PRIME 433494437LL
325 
326 void ff_init_elbg(int *points, int dim, int numpoints, int *codebook,
327  int numCB, int max_steps, int *closest_cb,
328  AVLFG *rand_state)
329 {
330  int i, k;
331 
332  if (numpoints > 24*numCB) {
333  /* ELBG is very costly for a big number of points. So if we have a lot
334  of them, get a good initial codebook to save on iterations */
335  int *temp_points = av_malloc(dim*(numpoints/8)*sizeof(int));
336  for (i=0; i<numpoints/8; i++) {
337  k = (i*BIG_PRIME) % numpoints;
338  memcpy(temp_points + i*dim, points + k*dim, dim*sizeof(int));
339  }
340 
341  ff_init_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state);
342  ff_do_elbg(temp_points, dim, numpoints/8, codebook, numCB, 2*max_steps, closest_cb, rand_state);
343 
344  av_free(temp_points);
345 
346  } else // If not, initialize the codebook with random positions
347  for (i=0; i < numCB; i++)
348  memcpy(codebook + i*dim, points + ((i*BIG_PRIME)%numpoints)*dim,
349  dim*sizeof(int));
350 
351 }
352 
353 void ff_do_elbg(int *points, int dim, int numpoints, int *codebook,
354  int numCB, int max_steps, int *closest_cb,
355  AVLFG *rand_state)
356 {
357  int dist;
358  elbg_data elbg_d;
359  elbg_data *elbg = &elbg_d;
360  int i, j, k, last_error, steps=0;
361  int *dist_cb = av_malloc(numpoints*sizeof(int));
362  int *size_part = av_malloc(numCB*sizeof(int));
363  cell *list_buffer = av_malloc(numpoints*sizeof(cell));
364  cell *free_cells;
365  int best_dist, best_idx = 0;
366 
367  elbg->error = INT_MAX;
368  elbg->dim = dim;
369  elbg->numCB = numCB;
370  elbg->codebook = codebook;
371  elbg->cells = av_malloc(numCB*sizeof(cell *));
372  elbg->utility = av_malloc(numCB*sizeof(int));
373  elbg->nearest_cb = closest_cb;
374  elbg->points = points;
375  elbg->utility_inc = av_malloc(numCB*sizeof(int));
376  elbg->scratchbuf = av_malloc(5*dim*sizeof(int));
377 
378  elbg->rand_state = rand_state;
379 
380  do {
381  free_cells = list_buffer;
382  last_error = elbg->error;
383  steps++;
384  memset(elbg->utility, 0, numCB*sizeof(int));
385  memset(elbg->cells, 0, numCB*sizeof(cell *));
386 
387  elbg->error = 0;
388 
389  /* This loop evaluate the actual Voronoi partition. It is the most
390  costly part of the algorithm. */
391  for (i=0; i < numpoints; i++) {
392  best_dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + best_idx*elbg->dim, dim, INT_MAX);
393  for (k=0; k < elbg->numCB; k++) {
394  dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + k*elbg->dim, dim, best_dist);
395  if (dist < best_dist) {
396  best_dist = dist;
397  best_idx = k;
398  }
399  }
400  elbg->nearest_cb[i] = best_idx;
401  dist_cb[i] = best_dist;
402  elbg->error += dist_cb[i];
403  elbg->utility[elbg->nearest_cb[i]] += dist_cb[i];
404  free_cells->index = i;
405  free_cells->next = elbg->cells[elbg->nearest_cb[i]];
406  elbg->cells[elbg->nearest_cb[i]] = free_cells;
407  free_cells++;
408  }
409 
410  do_shiftings(elbg);
411 
412  memset(size_part, 0, numCB*sizeof(int));
413 
414  memset(elbg->codebook, 0, elbg->numCB*dim*sizeof(int));
415 
416  for (i=0; i < numpoints; i++) {
417  size_part[elbg->nearest_cb[i]]++;
418  for (j=0; j < elbg->dim; j++)
419  elbg->codebook[elbg->nearest_cb[i]*elbg->dim + j] +=
420  elbg->points[i*elbg->dim + j];
421  }
422 
423  for (i=0; i < elbg->numCB; i++)
424  vect_division(elbg->codebook + i*elbg->dim,
425  elbg->codebook + i*elbg->dim, size_part[i], elbg->dim);
426 
427  } while(((last_error - elbg->error) > DELTA_ERR_MAX*elbg->error) &&
428  (steps < max_steps));
429 
430  av_free(dist_cb);
431  av_free(size_part);
432  av_free(elbg->utility);
433  av_free(list_buffer);
434  av_free(elbg->cells);
435  av_free(elbg->utility_inc);
436  av_free(elbg->scratchbuf);
437 }
#define FFMAX(a, b)
Definition: common.h:55
Definition: lfg.h:25
struct cell_s * next
Definition: elbg.c:40
static void do_shiftings(elbg_data *elbg)
Implementation of the ELBG block.
Definition: elbg.c:305
static int simple_lbg(elbg_data *elbg, int dim, int *centroid[3], int newutility[3], int *points, cell *cells)
Implementation of the simple LBG algorithm for just two codebooks.
Definition: elbg.c:122
cell ** cells
Definition: elbg.c:51
static int distance_limited(int *a, int *b, int dim, int limit)
Definition: elbg.c:60
static void get_new_centroids(elbg_data *elbg, int huc, int *newcentroid_i, int *newcentroid_p)
Definition: elbg.c:163
ELBG internal data.
Definition: elbg.c:46
static void evaluate_utility_inc(elbg_data *elbg)
Definition: elbg.c:227
AVLFG * rand_state
Definition: elbg.c:56
static unsigned int av_lfg_get(AVLFG *c)
Get the next random unsigned 32-bit number using an ALFG.
Definition: lfg.h:38
#define b
Definition: input.c:52
int index
Definition: elbg.c:39
#define ROUNDED_DIV(a, b)
Definition: common.h:51
#define r
Definition: input.c:51
int * codebook
Definition: elbg.c:50
void av_free(void *ptr)
Free a memory block which has been allocated with av_malloc(z)() or av_realloc(). ...
Definition: mem.c:186
int * utility_inc
Definition: elbg.c:53
static void vect_division(int *res, int *vect, int div, int dim)
Definition: elbg.c:72
int * nearest_cb
Definition: elbg.c:54
Libavcodec external API header.
void ff_do_elbg(int *points, int dim, int numpoints, int *codebook, int numCB, int max_steps, int *closest_cb, AVLFG *rand_state)
Implementation of the Enhanced LBG Algorithm Based on the paper "Neural Networks 14:1219-1237" that c...
Definition: elbg.c:353
int dim
Definition: elbg.c:48
In the ELBG jargon, a cell is the set of points that are closest to a codebook entry.
Definition: elbg.c:38
static int get_high_utility_cell(elbg_data *elbg)
Definition: elbg.c:106
void * av_malloc(size_t size) av_malloc_attrib 1(1)
Allocate a block of size bytes with alignment suitable for all memory accesses (including vectors if ...
Definition: mem.c:62
#define BIG_PRIME
Definition: elbg.c:324
static int get_closest_codebook(elbg_data *elbg, int index)
Definition: elbg.c:92
int * scratchbuf
Definition: elbg.c:57
static void update_utility_and_n_cb(elbg_data *elbg, int idx, int newutility)
Definition: elbg.c:239
int * points
Definition: elbg.c:55
NULL
Definition: eval.c:55
int index
Definition: gxfenc.c:72
int dim
void ff_init_elbg(int *points, int dim, int numpoints, int *codebook, int numCB, int max_steps, int *closest_cb, AVLFG *rand_state)
Initialize the **codebook vector for the elbg algorithm.
Definition: elbg.c:326
static void shift_codebook(elbg_data *elbg, int *indexes, int *newcentroid[3])
Add the points in the low utility cell to its closest cell.
Definition: elbg.c:199
static int eval_error_cell(elbg_data *elbg, int *centroid, cell *cells)
Definition: elbg.c:83
int error
Definition: elbg.c:47
#define DELTA_ERR_MAX
Precision of the ELBG algorithm (as percentual error)
Definition: elbg.c:33
int numCB
Definition: elbg.c:49
static void try_shift_candidate(elbg_data *elbg, int idx[3])
Evaluate if a shift lower the error.
Definition: elbg.c:255
int * utility
Definition: elbg.c:52
float min
#define FFMIN(a, b)
Definition: common.h:57