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package de.lmu.ifi.dbs.elki.evaluation.index;
/*
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 java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map.Entry;
import de.lmu.ifi.dbs.elki.data.DoubleVector;
import de.lmu.ifi.dbs.elki.database.Database;
import de.lmu.ifi.dbs.elki.database.ids.DBID;
import de.lmu.ifi.dbs.elki.database.relation.Relation;
import de.lmu.ifi.dbs.elki.evaluation.Evaluator;
import de.lmu.ifi.dbs.elki.index.tree.Node;
import de.lmu.ifi.dbs.elki.index.tree.spatial.SpatialDirectoryEntry;
import de.lmu.ifi.dbs.elki.index.tree.spatial.SpatialEntry;
import de.lmu.ifi.dbs.elki.index.tree.spatial.SpatialIndexTree;
import de.lmu.ifi.dbs.elki.index.tree.spatial.SpatialPointLeafEntry;
import de.lmu.ifi.dbs.elki.math.MeanVariance;
import de.lmu.ifi.dbs.elki.result.CollectionResult;
import de.lmu.ifi.dbs.elki.result.Result;
import de.lmu.ifi.dbs.elki.result.ResultHierarchy;
import de.lmu.ifi.dbs.elki.result.ResultUtil;
import de.lmu.ifi.dbs.elki.utilities.DatabaseUtil;
/**
* Compute the purity of index pages as a naive measure for performance
* capabilities using the Gini index.
*
* @author Erich Schubert
* @since 0.5.0
*/
public class IndexPurity implements Evaluator {
/**
* Constructor.
*/
public IndexPurity() {
super();
}
@Override
public void processNewResult(ResultHierarchy hier, Result newResult) {
Database database = ResultUtil.findDatabase(hier);
final ArrayList<SpatialIndexTree<?, ?>> indexes = ResultUtil.filterResults(hier, newResult, SpatialIndexTree.class);
if(indexes == null || indexes.size() <= 0) {
return;
}
Relation<String> lblrel = DatabaseUtil.guessLabelRepresentation(database);
for(SpatialIndexTree<?, ?> index : indexes) {
List<? extends SpatialEntry> leaves = index.getLeaves();
MeanVariance mv = new MeanVariance();
for(SpatialEntry e : leaves) {
SpatialDirectoryEntry leaf = (SpatialDirectoryEntry) e;
Node<?> n = index.getNode(leaf.getEntryID());
final int total = n.getNumEntries();
HashMap<String, Integer> map = new HashMap<>(total);
for(int i = 0; i < total; i++) {
DBID id = ((SpatialPointLeafEntry) n.getEntry(i)).getDBID();
String label = lblrel.get(id);
Integer val = map.get(label);
if(val == null) {
val = 1;
}
else {
val += 1;
}
map.put(label, val);
}
double gini = 0.0;
for(Entry<String, Integer> ent : map.entrySet()) {
double rel = ent.getValue() / (double) total;
gini += rel * rel;
}
mv.put(gini);
}
Collection<DoubleVector> col = new ArrayList<>();
col.add(new DoubleVector(new double[] { mv.getMean(), mv.getSampleStddev() }));
database.getHierarchy().add((Result) index, new CollectionResult<>("Gini coefficient of index", "index-gini", col));
}
}
}
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