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package de.lmu.ifi.dbs.elki.index.tree.metrical.mtreevariants.query;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2015
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.database.ids.DBID;
import de.lmu.ifi.dbs.elki.database.ids.DBIDUtil;
import de.lmu.ifi.dbs.elki.database.ids.KNNHeap;
import de.lmu.ifi.dbs.elki.database.ids.KNNList;
import de.lmu.ifi.dbs.elki.database.query.distance.DistanceQuery;
import de.lmu.ifi.dbs.elki.database.query.knn.AbstractDistanceKNNQuery;
import de.lmu.ifi.dbs.elki.index.tree.DirectoryEntry;
import de.lmu.ifi.dbs.elki.index.tree.metrical.mtreevariants.AbstractMTree;
import de.lmu.ifi.dbs.elki.index.tree.metrical.mtreevariants.AbstractMTreeNode;
import de.lmu.ifi.dbs.elki.index.tree.metrical.mtreevariants.MTreeEntry;
import de.lmu.ifi.dbs.elki.index.tree.query.DoubleMTreeDistanceSearchCandidate;
import de.lmu.ifi.dbs.elki.utilities.datastructures.heap.ComparableMinHeap;
/**
* Instance of a KNN query for a particular spatial index.
*
* @author Erich Schubert
* @since 0.4.0
*
* @apiviz.uses AbstractMTree
* @apiviz.uses DoubleMTreeDistanceSearchCandidate
*
* @param <O> Object type
*/
public class MetricalIndexKNNQuery<O> extends AbstractDistanceKNNQuery<O> {
/**
* The index to use
*/
protected final AbstractMTree<O, ?, ?, ?> index;
/**
* Constructor.
*
* @param index Index to use
* @param distanceQuery Distance query used
*/
public MetricalIndexKNNQuery(AbstractMTree<O, ?, ?, ?> index, DistanceQuery<O> distanceQuery) {
super(distanceQuery);
this.index = index;
}
@Override
public KNNList getKNNForObject(O q, int k) {
if(k < 1) {
throw new IllegalArgumentException("At least one object has to be requested!");
}
index.statistics.countKNNQuery();
KNNHeap knnList = DBIDUtil.newHeap(k);
double d_k = Double.POSITIVE_INFINITY;
final ComparableMinHeap<DoubleMTreeDistanceSearchCandidate> pq = new ComparableMinHeap<>();
// Push the root node
pq.add(new DoubleMTreeDistanceSearchCandidate(0., index.getRootID(), null, 0.));
// search in tree
while(!pq.isEmpty()) {
DoubleMTreeDistanceSearchCandidate pqNode = pq.poll();
if(knnList.size() >= k && pqNode.mindist > d_k) {
break;
}
AbstractMTreeNode<?, ?, ?> node = index.getNode(pqNode.nodeID);
DBID id_p = pqNode.routingObjectID;
double d1 = pqNode.routingDistance;
// directory node
if(!node.isLeaf()) {
for(int i = 0; i < node.getNumEntries(); i++) {
MTreeEntry entry = node.getEntry(i);
DBID o_r = entry.getRoutingObjectID();
double r_or = entry.getCoveringRadius();
double d2 = id_p != null ? entry.getParentDistance() : 0.;
double diff = Math.abs(d1 - d2);
double sum = d_k + r_or;
if(diff <= sum) {
double d3 = distanceQuery.distance(o_r, q);
index.statistics.countDistanceCalculation();
double d_min = Math.max(d3 - r_or, 0.);
if(d_min <= d_k) {
pq.add(new DoubleMTreeDistanceSearchCandidate(d_min, ((DirectoryEntry) entry).getPageID(), o_r, d3));
}
}
}
}
// data node
else {
for(int i = 0; i < node.getNumEntries(); i++) {
MTreeEntry entry = node.getEntry(i);
DBID o_j = entry.getRoutingObjectID();
double d2 = id_p != null ? entry.getParentDistance() : 0.;
double diff = Math.abs(d1 - d2);
if(diff <= d_k) {
double d3 = distanceQuery.distance(o_j, q);
index.statistics.countDistanceCalculation();
if(d3 <= d_k) {
knnList.insert(d3, o_j);
d_k = knnList.getKNNDistance();
}
}
}
}
}
return knnList.toKNNList();
}
}
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