package de.lmu.ifi.dbs.elki.index.tree.spatial.rstarvariants.strategies.insert;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2012
Ludwig-Maximilians-Universität München
Lehr- und Forschungseinheit für Datenbanksysteme
ELKI Development Team
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import de.lmu.ifi.dbs.elki.data.HyperBoundingBox;
import de.lmu.ifi.dbs.elki.data.spatial.SpatialComparable;
import de.lmu.ifi.dbs.elki.data.spatial.SpatialUtil;
import de.lmu.ifi.dbs.elki.utilities.datastructures.arraylike.ArrayAdapter;
import de.lmu.ifi.dbs.elki.utilities.documentation.Reference;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.AbstractParameterizer;
/**
* The choose subtree method proposed by the R*-Tree for leaf nodes.
*
* <p>
* N. Beckmann, H.-P. Kriegel, R. Schneider, B. Seeger:<br />
* The R*-tree: an efficient and robust access method for points and rectangles<br />
* in: Proceedings of the 1990 ACM SIGMOD International Conference on Management
* of Data, Atlantic City, NJ, May 23-25, 1990
* </p>
*
* @author Erich Schubert
*/
@Reference(authors = "N. Beckmann, H.-P. Kriegel, R. Schneider, B. Seeger", title = "The R*-tree: an efficient and robust access method for points and rectangles", booktitle = "Proceedings of the 1990 ACM SIGMOD International Conference on Management of Data, Atlantic City, NJ, May 23-25, 1990", url = "http://dx.doi.org/10.1145/93597.98741")
public class LeastOverlapInsertionStrategy implements InsertionStrategy {
/**
* Static instance.
*/
public static final LeastOverlapInsertionStrategy STATIC = new LeastOverlapInsertionStrategy();
/**
* Constructor.
*/
public LeastOverlapInsertionStrategy() {
super();
}
@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;
}
/**
* Parameterization class.
*
* @author Erich Schubert
*
* @apiviz.exclude
*/
public static class Parameterizer extends AbstractParameterizer {
@Override
protected LeastOverlapInsertionStrategy makeInstance() {
return LeastOverlapInsertionStrategy.STATIC;
}
}
}