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package de.lmu.ifi.dbs.elki.utilities.datastructures.heap;
/*
This file is part of ELKI:
Environment for Developing KDD-Applications Supported by Index-Structures
Copyright (C) 2012
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 static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Queue;
import java.util.Random;
import org.junit.Test;
/**
* Unit test to ensure that our heap is not significantly worse than SUN javas
* regular PriorityQueue.
*
* @author Erich Schubert
*/
public class TestHeapPerformance {
final private int queueSize = 200000;
final private int preiterations = 20;
final private int iterations = 200;
final private long seed = 123456L;
@Test
public void testRuntime() throws Exception {
// prepare the data set
final List<Integer> elements = new ArrayList<>(queueSize);
{
final Random random = new Random(seed);
for(int i = 0; i < queueSize; i++) {
elements.add(i);
}
Collections.shuffle(elements, random);
}
// Pretest, to trigger hotspot compiler, hopefully.
{
for(int j = 0; j < preiterations; j++) {
ComparableMinHeap<Integer> pq = new ComparableMinHeap<>();
testHeap(elements, pq);
}
for(int j = 0; j < preiterations; j++) {
PriorityQueue<Integer> pq = new PriorityQueue<>();
testQueue(elements, pq);
}
}
long pqstart = System.nanoTime();
{
for(int j = 0; j < iterations; j++) {
PriorityQueue<Integer> pq = new PriorityQueue<>();
testQueue(elements, pq);
}
}
long pqtime = System.nanoTime() - pqstart;
long hstart = System.nanoTime();
{
for(int j = 0; j < iterations; j++) {
ComparableMinHeap<Integer> pq = new ComparableMinHeap<>();
testHeap(elements, pq);
}
}
long htime = System.nanoTime() - hstart;
System.err.println("Heap performance test: us: " + htime*1E-9 + " java: " + pqtime*1E-9);
assertTrue("Heap performance regression - run test individually, since the hotspot optimizations may make the difference! " + htime + " >>= " + pqtime, htime < 1.05 * pqtime);
// 1.05 allows some difference in measuring
}
private void testHeap(final List<Integer> elements, ComparableMinHeap<Integer> pq) {
// Insert all
for(int i = 0; i < elements.size(); i++) {
pq.add(elements.get(i));
}
// Poll first half.
for(int i = 0; i < elements.size() >> 1; i++) {
assertEquals((int) pq.poll(), i);
// assertEquals((int) pq.poll(), queueSize - 1 - i);
}
assertTrue("Heap not half-empty?", pq.size() == (elements.size() >> 1));
pq.clear();
}
private void testQueue(final List<Integer> elements, Queue<Integer> pq) {
// Insert all
for(int i = 0; i < elements.size(); i++) {
pq.add(elements.get(i));
}
// Poll first half.
for(int i = 0; i < elements.size() >> 1; i++) {
assertEquals((int) pq.poll(), i);
// assertEquals((int) pq.poll(), queueSize - 1 - i);
}
assertTrue("Heap not half-empty?", pq.size() == (elements.size() >> 1));
pq.clear();
}
}
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