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package de.lmu.ifi.dbs.elki.database.query.knn;
/*
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.Arrays;
import java.util.List;
import de.lmu.ifi.dbs.elki.database.ids.DBID;
import de.lmu.ifi.dbs.elki.database.query.DistanceResultPair;
import de.lmu.ifi.dbs.elki.database.query.DoubleDistanceResultPair;
import de.lmu.ifi.dbs.elki.database.query.distance.PrimitiveDistanceQuery;
import de.lmu.ifi.dbs.elki.distance.distancefunction.PrimitiveDoubleDistanceFunction;
import de.lmu.ifi.dbs.elki.distance.distancevalue.DoubleDistance;
import de.lmu.ifi.dbs.elki.utilities.datastructures.heap.KNNHeap;
/**
* Optimized linear scan query for {@link PrimitiveDoubleDistanceFunction}s.
*
* @author Erich Schubert
*
* @apiviz.uses PrimitiveDoubleDistanceFunction
*
* @param <O> Object type
*/
public class LinearScanRawDoubleDistanceKNNQuery<O> extends LinearScanPrimitiveDistanceKNNQuery<O, DoubleDistance> {
/**
* Constructor.
*
* @param distanceQuery Distance function to use
*/
public LinearScanRawDoubleDistanceKNNQuery(PrimitiveDistanceQuery<O, DoubleDistance> distanceQuery) {
super(distanceQuery);
if(!(distanceQuery.getDistanceFunction() instanceof PrimitiveDoubleDistanceFunction)) {
throw new UnsupportedOperationException("LinearScanRawDoubleDistance instantiated for non-RawDoubleDistance!");
}
}
@Override
public List<DistanceResultPair<DoubleDistance>> getKNNForDBID(DBID id, int k) {
return getKNNForObject(relation.get(id), k);
}
@Override
public List<DistanceResultPair<DoubleDistance>> getKNNForObject(O obj, int k) {
@SuppressWarnings("unchecked")
final PrimitiveDoubleDistanceFunction<O> rawdist = (PrimitiveDoubleDistanceFunction<O>) distanceQuery.getDistanceFunction();
// Optimization for double distances.
final KNNHeap<DoubleDistance> heap = new KNNHeap<DoubleDistance>(k);
double max = Double.POSITIVE_INFINITY;
for(DBID candidateID : relation.iterDBIDs()) {
final double doubleDistance = rawdist.doubleDistance(obj, relation.get(candidateID));
if(doubleDistance <= max) {
heap.add(new DoubleDistanceResultPair(doubleDistance, candidateID));
// Update cutoff
if(heap.size() >= heap.getK()) {
max = ((DoubleDistanceResultPair) heap.peek()).getDoubleDistance();
}
}
}
return heap.toSortedArrayList();
}
@Override
protected void linearScanBatchKNN(List<O> objs, List<KNNHeap<DoubleDistance>> heaps) {
final int size = objs.size();
@SuppressWarnings("unchecked")
final PrimitiveDoubleDistanceFunction<O> rawdist = (PrimitiveDoubleDistanceFunction<O>) distanceQuery.getDistanceFunction();
// Track the max ourselves to reduce object access for comparisons.
final double[] max = new double[size];
Arrays.fill(max, Double.POSITIVE_INFINITY);
// The distance is computed on arbitrary vectors, we can reduce object
// loading by working on the actual vectors.
for(DBID candidateID : relation.iterDBIDs()) {
O candidate = relation.get(candidateID);
for(int index = 0; index < size; index++) {
final KNNHeap<DoubleDistance> heap = heaps.get(index);
double doubleDistance = rawdist.doubleDistance(objs.get(index), candidate);
if(doubleDistance <= max[index]) {
heap.add(new DoubleDistanceResultPair(doubleDistance, candidateID));
if(heap.size() >= heap.getK()) {
max[index] = ((DoubleDistanceResultPair) heap.peek()).getDoubleDistance();
}
}
}
}
}
}
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