1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
package de.lmu.ifi.dbs.elki.index.tree.metrical.mtreevariants.split;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2011
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 java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import de.lmu.ifi.dbs.elki.database.ids.DBID;
import de.lmu.ifi.dbs.elki.database.query.distance.DistanceQuery;
import de.lmu.ifi.dbs.elki.distance.DistanceUtil;
import de.lmu.ifi.dbs.elki.distance.distancevalue.Distance;
import de.lmu.ifi.dbs.elki.index.tree.DistanceEntry;
import de.lmu.ifi.dbs.elki.index.tree.metrical.mtreevariants.AbstractMTreeNode;
import de.lmu.ifi.dbs.elki.index.tree.metrical.mtreevariants.MTreeEntry;
/**
* Abstract super class for splitting a node in an M-Tree.
*
* @author Elke Achtert
*
* @apiviz.composedOf Assignments
*
* @param <O> the type of DatabaseObject to be stored in the M-Tree
* @param <D> the type of Distance used in the M-Tree
* @param <N> the type of AbstractMTreeNode used in the M-Tree
* @param <E> the type of MetricalEntry used in the M-Tree
*/
public abstract class MTreeSplit<O, D extends Distance<D>, N extends AbstractMTreeNode<O, D, N, E>, E extends MTreeEntry<D>> {
/**
* Encapsulates the two promotion objects and their assignments.
*/
Assignments<D, E> assignments;
/**
* Creates a balanced partition of the entries of the specified node.
*
* @param node the node to be split
* @param routingObject1 the id of the first routing object
* @param routingObject2 the id of the second routing object
* @param distanceFunction the distance function to compute the distances
* @return an assignment that holds a balanced partition of the entries of the
* specified node
*/
Assignments<D, E> balancedPartition(N node, DBID routingObject1, DBID routingObject2, DistanceQuery<O, D> distanceFunction) {
HashSet<E> assigned1 = new HashSet<E>();
HashSet<E> assigned2 = new HashSet<E>();
D currentCR1 = distanceFunction.nullDistance();
D currentCR2 = distanceFunction.nullDistance();
// determine the nearest neighbors
List<DistanceEntry<D, E>> list1 = new ArrayList<DistanceEntry<D, E>>();
List<DistanceEntry<D, E>> list2 = new ArrayList<DistanceEntry<D, E>>();
for(int i = 0; i < node.getNumEntries(); i++) {
DBID id = node.getEntry(i).getRoutingObjectID();
// determine the distance of o to o1 / o2
D d1 = distanceFunction.distance(routingObject1, id);
D d2 = distanceFunction.distance(routingObject2, id);
list1.add(new DistanceEntry<D, E>(node.getEntry(i), d1, i));
list2.add(new DistanceEntry<D, E>(node.getEntry(i), d2, i));
}
Collections.sort(list1);
Collections.sort(list2);
for(int i = 0; i < node.getNumEntries(); i++) {
if(i % 2 == 0) {
currentCR1 = assignNN(assigned1, assigned2, list1, currentCR1, node.isLeaf());
}
else {
currentCR2 = assignNN(assigned2, assigned1, list2, currentCR2, node.isLeaf());
}
}
return new Assignments<D, E>(routingObject1, routingObject2, currentCR1, currentCR2, assigned1, assigned2);
}
/**
* Assigns the first object of the specified list to the first assignment that
* it is not yet assigned to the second assignment.
*
* @param assigned1 the first assignment
* @param assigned2 the second assignment
* @param list the list, the first object should be assigned
* @param currentCR the current covering radius
* @param isLeaf true, if the node of the entries to be assigned is a leaf,
* false otherwise
* @return the new covering radius
*/
private D assignNN(Set<E> assigned1, Set<E> assigned2, List<DistanceEntry<D, E>> list, D currentCR, boolean isLeaf) {
DistanceEntry<D, E> distEntry = list.remove(0);
while(assigned2.contains(distEntry.getEntry())) {
distEntry = list.remove(0);
}
// Update the parent distance.
distEntry.getEntry().setParentDistance(distEntry.getDistance());
assigned1.add(distEntry.getEntry());
if(isLeaf) {
return DistanceUtil.max(currentCR, distEntry.getDistance());
}
else {
return DistanceUtil.max(currentCR, distEntry.getDistance().plus((distEntry.getEntry()).getCoveringRadius()));
}
}
/**
* Returns the assignments of this split.
*
* @return the assignments of this split
*/
public Assignments<D, E> getAssignments() {
return assignments;
}
}
|
