/**
* Add the points in the low utility cell to its closest cell. Split the high
* utility cell, putting the separate points in the (now empty) low utility
* cell.
*
* @param elbg Internal elbg data
* @param indexes {luc, huc, cluc}
* @param newcentroid A vector with the position of the new centroids
*/
static void shift_codebook(elbg_data *elbg, int *indexes,
int *newcentroid[3])
{
cell *tempdata;
cell **pp = &elbg->cells[indexes[2]];
while(*pp)
pp= &(*pp)->next;
*pp = elbg->cells[indexes[0]];
elbg->cells[indexes[0]] = NULL;
tempdata = elbg->cells[indexes[1]];
elbg->cells[indexes[1]] = NULL;
while(tempdata) {
cell *tempcell2 = tempdata->next;
int idx = distance_limited(elbg->points + tempdata->index*elbg->dim,
newcentroid[0], elbg->dim, INT_MAX) >
distance_limited(elbg->points + tempdata->index*elbg->dim,
newcentroid[1], elbg->dim, INT_MAX);
tempdata->next = elbg->cells[indexes[idx]];
elbg->cells[indexes[idx]] = tempdata;
tempdata = tempcell2;
}
}
static int eval_error_cell(elbg_data *elbg, int *centroid, cell *cells)
{
int error=0;
for (; cells; cells=cells->next)
error += distance_limited(centroid, elbg->points + cells->index*elbg->dim, elbg->dim, INT_MAX);
return error;
}
/**
* Implementation of the simple LBG algorithm for just two codebooks
*/
static int simple_lbg(elbg_data *elbg,
int dim,
int *centroid[3],
int newutility[3],
int *points,
cell *cells)
{
int i, idx;
int numpoints[2] = {0, 0};
int *newcentroid[2] =
{
elbg->scratchbuf + 3 * dim,
elbg->scratchbuf + 4 * dim
};
cell *tempcell;
memset(newcentroid[0], 0, 2 * dim * sizeof(*newcentroid[0]));
newutility[0] =
newutility[1] = 0;
for (tempcell = cells; tempcell; tempcell = tempcell->next)
{
idx = distance_limited(centroid[0], points + tempcell->index * dim, dim, INT_MAX) >=
distance_limited(centroid[1], points + tempcell->index * dim, dim, INT_MAX);
numpoints[idx]++;
for (i = 0; i < dim; i++)
newcentroid[idx][i] += points[tempcell->index*dim + i];
}
vect_division(centroid[0], newcentroid[0], numpoints[0], dim);
vect_division(centroid[1], newcentroid[1], numpoints[1], dim);
for (tempcell = cells; tempcell; tempcell = tempcell->next)
{
int dist[2] = {distance_limited(centroid[0], points + tempcell->index *dim, dim, INT_MAX),
distance_limited(centroid[1], points + tempcell->index *dim, dim, INT_MAX)
};
int idx = dist[0] > dist[1];
newutility[idx] += dist[idx];
}
return newutility[0] + newutility[1];
}
static int get_closest_codebook(elbg_data *elbg, int index)
{
int i, pick=0, diff, diff_min = INT_MAX;
for (i=0; i<elbg->numCB; i++)
if (i != index) {
diff = distance_limited(elbg->codebook + i*elbg->dim, elbg->codebook + index*elbg->dim, elbg->dim, diff_min);
if (diff < diff_min) {
pick = i;
diff_min = diff;
}
}
return pick;
}
void ff_do_elbg(int *points, int dim, int numpoints, int *codebook,
int numCB, int max_steps, int *closest_cb,
AVLFG *rand_state)
{
int dist;
elbg_data elbg_d;
elbg_data *elbg = &elbg_d;
int i, j, k, last_error, steps=0;
int *dist_cb = av_malloc(numpoints*sizeof(int));
int *size_part = av_malloc(numCB*sizeof(int));
cell *list_buffer = av_malloc(numpoints*sizeof(cell));
cell *free_cells;
int best_dist, best_idx = 0;
elbg->error = INT_MAX;
elbg->dim = dim;
elbg->numCB = numCB;
elbg->codebook = codebook;
elbg->cells = av_malloc(numCB*sizeof(cell *));
elbg->utility = av_malloc(numCB*sizeof(int));
elbg->nearest_cb = closest_cb;
elbg->points = points;
elbg->utility_inc = av_malloc(numCB*sizeof(int));
elbg->scratchbuf = av_malloc(5*dim*sizeof(int));
elbg->rand_state = rand_state;
do {
free_cells = list_buffer;
last_error = elbg->error;
steps++;
memset(elbg->utility, 0, numCB*sizeof(int));
memset(elbg->cells, 0, numCB*sizeof(cell *));
elbg->error = 0;
/* This loop evaluate the actual Voronoi partition. It is the most
costly part of the algorithm. */
for (i=0; i < numpoints; i++) {
best_dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + best_idx*elbg->dim, dim, INT_MAX);
for (k=0; k < elbg->numCB; k++) {
dist = distance_limited(elbg->points + i*elbg->dim, elbg->codebook + k*elbg->dim, dim, best_dist);
if (dist < best_dist) {
best_dist = dist;
best_idx = k;
}
}
elbg->nearest_cb[i] = best_idx;
dist_cb[i] = best_dist;
elbg->error += dist_cb[i];
elbg->utility[elbg->nearest_cb[i]] += dist_cb[i];
free_cells->index = i;
free_cells->next = elbg->cells[elbg->nearest_cb[i]];
elbg->cells[elbg->nearest_cb[i]] = free_cells;
free_cells++;
}
do_shiftings(elbg);
memset(size_part, 0, numCB*sizeof(int));
memset(elbg->codebook, 0, elbg->numCB*dim*sizeof(int));
for (i=0; i < numpoints; i++) {
size_part[elbg->nearest_cb[i]]++;
for (j=0; j < elbg->dim; j++)
elbg->codebook[elbg->nearest_cb[i]*elbg->dim + j] +=
elbg->points[i*elbg->dim + j];
}
for (i=0; i < elbg->numCB; i++)
vect_division(elbg->codebook + i*elbg->dim,
elbg->codebook + i*elbg->dim, size_part[i], elbg->dim);
} while(((last_error - elbg->error) > DELTA_ERR_MAX*elbg->error) &&
(steps < max_steps));
av_free(dist_cb);
av_free(size_part);
av_free(elbg->utility);
av_free(list_buffer);
av_free(elbg->cells);
av_free(elbg->utility_inc);
av_free(elbg->scratchbuf);
}
