@Override
public <A> int choose(
A options,
ArrayAdapter<? extends SpatialComparable, A> getter,
SpatialComparable obj,
int height,
int depth) {
final int size = getter.size(options);
assert (size > 0) : "Choose from empty set?";
// R*-Tree: overlap increase for leaves.
int best = -1;
double least_overlap = Double.POSITIVE_INFINITY;
double least_areainc = Double.POSITIVE_INFINITY;
double least_area = Double.POSITIVE_INFINITY;
// least overlap increase, on reduced candidate set:
for (int i = 0; i < size; i++) {
// Existing object and extended rectangle:
SpatialComparable entry = getter.get(options, i);
HyperBoundingBox mbr = SpatialUtil.union(entry, obj);
// Compute relative overlap increase.
double overlap_wout = 0.0;
double overlap_with = 0.0;
for (int k = 0; k < size; k++) {
if (i != k) {
SpatialComparable other = getter.get(options, k);
overlap_wout += SpatialUtil.relativeOverlap(entry, other);
overlap_with += SpatialUtil.relativeOverlap(mbr, other);
}
}
double inc_overlap = overlap_with - overlap_wout;
if (inc_overlap < least_overlap) {
final double area = SpatialUtil.volume(entry);
final double inc_area = SpatialUtil.volume(mbr) - area;
// Volume increase and overlap increase:
least_overlap = inc_overlap;
least_areainc = inc_area;
least_area = area;
best = i;
} else if (inc_overlap == least_overlap) {
final double area = SpatialUtil.volume(entry);
final double inc_area = SpatialUtil.volume(mbr) - area;
if (inc_area < least_areainc || (inc_area == least_areainc && area < least_area)) {
least_overlap = inc_overlap;
least_areainc = inc_area;
least_area = area;
best = i;
}
}
}
assert (best > -1) : "No split found? Volume outside of double precision?";
return best;
}
/**
* Compute the union of a number of objects as a flat MBR (low-level, for index structures).
*
* @param data Object
* @param getter Array adapter
* @param <E> object type
* @param <A> data value type
* @return Flat MBR
*/
public static <E extends SpatialComparable, A> double[] unionFlatMBR(
A data, ArrayAdapter<E, ? super A> getter) {
final int num = getter.size(data);
assert (num > 0) : "Cannot compute MBR of empty set.";
final int dim;
final double[] mbr;
{ // First entry
final E first = getter.get(data, 0);
dim = first.getDimensionality();
mbr = new double[2 * dim];
for (int d = 0; d < dim; d++) {
mbr[d] = first.getMin(d);
mbr[dim + d] = first.getMax(d);
}
} // Remaining entries
for (int i = 1; i < num; i++) {
E next = getter.get(data, i);
for (int d = 0; d < dim; d++) {
mbr[d] = Math.min(mbr[d], next.getMin(d));
mbr[dim + d] = Math.max(mbr[dim + d], next.getMax(d));
}
}
return mbr;
}
