void annPlaneSplit( // split points by a plane
ANNpointArray pa, // points to split
ANNidxArray pidx, // point indices
int n, // number of points
int d, // dimension along which to split
ANNcoord cv, // cutting value
int &br1, // first break (values < cv)
int &br2) // second break (values == cv)
{
int l = 0;
int r = n-1;
for(;;) { // partition pa[0..n-1] about cv
while (l < n && PA(l,d) < cv) l++;
while (r >= 0 && PA(r,d) >= cv) r--;
if (l > r) break;
PASWAP(l,r);
l++; r--;
}
br1 = l; // now: pa[0..br1-1] < cv <= pa[br1..n-1]
r = n-1;
for(;;) { // partition pa[br1..n-1] about cv
while (l < n && PA(l,d) <= cv) l++;
while (r >= br1 && PA(r,d) > cv) r--;
if (l > r) break;
PASWAP(l,r);
l++; r--;
}
br2 = l; // now: pa[br1..br2-1] == cv < pa[br2..n-1]
}
void annMedianSplit(
ANNpointArray pa, // points to split
ANNidxArray pidx, // point indices
int n, // number of points
int d, // dimension along which to split
ANNcoord &cv, // cutting value
int n_lo) // split into n_lo and n-n_lo
{
int l = 0; // left end of current subarray
int r = n-1; // right end of current subarray
while (l < r) {
register int i = (r+l)/2; // select middle as pivot
register int k;
if (PA(i,d) > PA(r,d)) // make sure last > pivot
PASWAP(i,r)
PASWAP(l,i); // move pivot to first position
ANNcoord c = PA(l,d); // pivot value
i = l;
k = r;
for(;;) { // pivot about c
while (PA(++i,d) < c) ;
while (PA(--k,d) > c) ;
if (i < k) PASWAP(i,k) else break;
}
PASWAP(l,k); // pivot winds up in location k
if (k > n_lo) r = k-1; // recurse on proper subarray
else if (k < n_lo) l = k+1;
else break; // got the median exactly
}
if (n_lo > 0) { // search for next smaller item
ANNcoord c = PA(0,d); // candidate for max
int k = 0; // candidate's index
for (int i = 1; i < n_lo; i++) {
if (PA(i,d) > c) {
c = PA(i,d);
k = i;
}
}
PASWAP(n_lo-1, k); // max among pa[0..n_lo-1] to pa[n_lo-1]
}
// cut value is midpoint value
cv = (PA(n_lo-1,d) + PA(n_lo,d))/2.0;
}
void annBoxSplit( // split points by a box
ANNpointArray pa, // points to split
ANNidxArray pidx, // point indices
int n, // number of points
int dim, // dimension of space
ANNorthRect &box, // the box
int &n_in) // number of points inside (returned)
{
int l = 0;
int r = n-1;
for(;;) { // partition pa[0..n-1] about box
while (l < n && box.inside(dim, PP(l))) l++;
while (r >= 0 && !box.inside(dim, PP(r))) r--;
if (l > r) break;
PASWAP(l,r);
l++; r--;
}
n_in = l; // now: pa[0..n_in-1] inside and rest outside
}
void annPlaneSplit( // split points by a plane
ES_INFO* es_info,
ANNpointArray pa, // points to split
ANNidxArray pidx, // point indices
int n, // number of points
int d, // dimension along which to split
ANNcoord cv, // cutting value
int &br1, // first break (values < cv)
int &br2) // second break (values == cv)
{
int l = 0;
int r = n-1;
for(;;) { // partition pa[0..n-1] about cv
#if 1 // es code
es_info->get_value_by_index(pidx[l]);
#endif
while (l < n && PA(l,d) < cv) {
l++;
#if 1 // es code
es_info->get_value_by_index(pidx[l]);
#endif
}
#if 1 // es code
es_info->get_value_by_index(pidx[r]);
#endif
while (r >= 0 && PA(r,d) >= cv) {
r--;
#if 1 // es code
es_info->get_value_by_index(pidx[r]);
#endif
}
if (l > r) break;
PASWAP(l,r);
l++; r--;
}
br1 = l; // now: pa[0..br1-1] < cv <= pa[br1..n-1]
r = n-1;
for(;;) { // partition pa[br1..n-1] about cv
#if 1 // es code
es_info->get_value_by_index(pidx[l]);
#endif
while (l < n && PA(l,d) <= cv) {
l++;
#if 1 // es code
es_info->get_value_by_index(pidx[l]);
#endif
}
#if 1 // es code
es_info->get_value_by_index(pidx[r]);
#endif
while (r >= br1 && PA(r,d) > cv) {
r--;
#if 1 // es code
es_info->get_value_by_index(pidx[r]);
#endif
}
if (l > r) break;
PASWAP(l,r);
l++; r--;
}
br2 = l; // now: pa[br1..br2-1] == cv < pa[br2..n-1]
}
/************************************************
Partition a range of data points by manipulation the permutation index.
The sliding midpoint rule is used for the partitioning.
Params:
pa : data points
pidx : permutation index of data points
no_dims: number of dimensions
start_idx : index of first data point to use
n : number of data points
bbox : bounding box of data points
cut_dim : dimension used for partition (return)
cut_val : value of cutting point (return)
n_lo : number of point below cutting plane (return)
************************************************/
int partition_float(float *pa, uint32_t *pidx, int8_t no_dims, uint32_t start_idx, uint32_t n, float *bbox, int8_t *cut_dim, float *cut_val, uint32_t *n_lo)
{
int8_t dim = 0, i;
uint32_t p, q, i2;
float size = 0, min_val, max_val, split, side_len, cur_val;
uint32_t end_idx = start_idx + n - 1;
/* Find largest bounding box side */
for (i = 0; i < no_dims; i++)
{
side_len = bbox[2 * i + 1] - bbox[2 * i];
if (side_len > size)
{
dim = i;
size = side_len;
}
}
min_val = bbox[2 * dim];
max_val = bbox[2 * dim + 1];
/* Check for zero length or inconsistent */
if (min_val >= max_val)
return 1;
/* Use middle for splitting */
split = (min_val + max_val) / 2;
/* Partition all data points around middle */
p = start_idx;
q = end_idx;
while (p <= q)
{
if (PA(p, dim) < split)
{
p++;
}
else if (PA(q, dim) >= split)
{
/* Guard for underflow */
if (q > 0)
{
q--;
}
else
{
break;
}
}
else
{
PASWAP(p, q);
p++;
q--;
}
}
/* Check for empty splits */
if (p == start_idx)
{
/* No points less than split.
Split at lowest point instead.
Minimum 1 point will be in lower box.
*/
uint32_t j = start_idx;
split = PA(j, dim);
for (i2 = start_idx + 1; i2 <= end_idx; i2++)
{
/* Find lowest point */
cur_val = PA(i2, dim);
if (cur_val < split)
{
j = i2;
split = cur_val;
}
}
PASWAP(j, start_idx);
p = start_idx + 1;
}
else if (p == end_idx + 1)
{
/* No points greater than split.
Split at highest point instead.
Minimum 1 point will be in higher box.
*/
uint32_t j = end_idx;
split = PA(j, dim);
for (i2 = start_idx; i2 < end_idx; i2++)
{
/* Find highest point */
cur_val = PA(i2, dim);
if (cur_val > split)
{
j = i2;
split = cur_val;
}
}
PASWAP(j, end_idx);
p = end_idx;
}
/* Set return values */
*cut_dim = dim;
*cut_val = split;
*n_lo = p - start_idx;
return 0;
}
