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package de.lmu.ifi.dbs.elki.algorithm.outlier.lof.parallel;
/*
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.datastore.DataStore;
import de.lmu.ifi.dbs.elki.database.datastore.DoubleDataStore;
import de.lmu.ifi.dbs.elki.database.ids.DBIDRef;
import de.lmu.ifi.dbs.elki.database.ids.DBIDUtil;
import de.lmu.ifi.dbs.elki.database.ids.DoubleDBIDListIter;
import de.lmu.ifi.dbs.elki.database.ids.KNNList;
import de.lmu.ifi.dbs.elki.math.MathUtil;
import de.lmu.ifi.dbs.elki.parallel.Executor;
import de.lmu.ifi.dbs.elki.parallel.processor.AbstractDoubleProcessor;
import de.lmu.ifi.dbs.elki.parallel.variables.SharedDouble;
/**
* Processor for the "local reachability density" of LOF.
*
* @author Erich Schubert
* @since 0.7.0
*
* @apiviz.has Instance
*/
public class LRDProcessor extends AbstractDoubleProcessor {
/**
* KNN store
*/
private DataStore<? extends KNNList> knns;
/**
* k-distance store
*/
private DoubleDataStore kdists;
/**
* Constructor.
*
* @param knns k nearest neighbors
* @param kdists k distances
*/
public LRDProcessor(DataStore<? extends KNNList> knns, DoubleDataStore kdists) {
super();
this.knns = knns;
this.kdists = kdists;
}
@Override
public Instance instantiate(Executor master) {
return new Instance(master.getInstance(output));
}
/**
* Instance
*
* @author Erich Schubert
*/
private class Instance extends AbstractDoubleProcessor.Instance {
/**
* Constructor.
*
* @param output Output variable
*/
protected Instance(SharedDouble.Instance output) {
super(output);
}
@Override
public void map(DBIDRef id) {
KNNList knn = knns.get(id);
double lrd = 0.0;
int size = 0;
for(DoubleDBIDListIter n = knn.iter(); n.valid(); n.advance()) {
// Do not include the query object
if(DBIDUtil.equal(n, id)) {
continue;
}
lrd += MathUtil.max(kdists.doubleValue(n), n.doubleValue());
size += 1;
}
// Avoid division by 0:
output.set(lrd > 0 ? size / lrd : Double.POSITIVE_INFINITY);
}
}
}
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