/**
* Evaluate if a shift lower the error. If it does, call shift_codebooks
* and update elbg->error, elbg->utility and elbg->nearest_cb.
*
* @param elbg Internal elbg data
* @param idx {luc (low utility cell, huc (high utility cell), cluc (closest cell to low utility cell)}
*/
static void try_shift_candidate(elbg_data *elbg, int idx[3])
{
int j, k, olderror = 0, newerror, cont = 0;
int newutility[3];
int *newcentroid[3] =
{
elbg->scratchbuf,
elbg->scratchbuf + elbg->dim,
elbg->scratchbuf + 2 * elbg->dim
};
cell *tempcell;
for (j = 0; j < 3; j++)
olderror += elbg->utility[idx[j]];
memset(newcentroid[2], 0, elbg->dim * sizeof(int));
for (k = 0; k < 2; k++)
for (tempcell = elbg->cells[idx[2*k]]; tempcell; tempcell = tempcell->next)
{
cont++;
for (j = 0; j < elbg->dim; j++)
newcentroid[2][j] += elbg->points[tempcell->index*elbg->dim + j];
}
vect_division(newcentroid[2], newcentroid[2], cont, elbg->dim);
get_new_centroids(elbg, idx[1], newcentroid[0], newcentroid[1]);
newutility[2] = eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[0]]);
newutility[2] += eval_error_cell(elbg, newcentroid[2], elbg->cells[idx[2]]);
newerror = newutility[2];
newerror += simple_lbg(elbg, elbg->dim, newcentroid, newutility, elbg->points,
elbg->cells[idx[1]]);
if (olderror > newerror)
{
shift_codebook(elbg, idx, newcentroid);
elbg->error += newerror - olderror;
for (j = 0; j < 3; j++)
update_utility_and_n_cb(elbg, idx[j], newutility[j]);
evaluate_utility_inc(elbg);
}
}
/**
* Implementation of the ELBG block
*/
static void do_shiftings(elbg_data *elbg)
{
int idx[3];
evaluate_utility_inc(elbg);
for (idx[0]=0; idx[0] < elbg->numCB; idx[0]++)
if (elbg->numCB*elbg->utility[idx[0]] < elbg->error) {
if (elbg->utility_inc[elbg->numCB-1] == 0)
return;
idx[1] = get_high_utility_cell(elbg);
idx[2] = get_closest_codebook(elbg, idx[0]);
try_shift_candidate(elbg, idx);
}
}
