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- /*
- * Copyright (C) 2009, Christian Halstrick <christian.halstrick@sap.com>
- * and other copyright owners as documented in the project's IP log.
- *
- * This program and the accompanying materials are made available
- * under the terms of the Eclipse Distribution License v1.0 which
- * accompanies this distribution, is reproduced below, and is
- * available at http://www.eclipse.org/org/documents/edl-v10.php
- *
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or
- * without modification, are permitted provided that the following
- * conditions are met:
- *
- * - Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * - Redistributions in binary form must reproduce the above
- * copyright notice, this list of conditions and the following
- * disclaimer in the documentation and/or other materials provided
- * with the distribution.
- *
- * - Neither the name of the Eclipse Foundation, Inc. nor the
- * names of its contributors may be used to endorse or promote
- * products derived from this software without specific prior
- * written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
- * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
- * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
- * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
- * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
- * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
- * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
- * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
- * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- */
-
- package org.eclipse.jgit.diff;
-
- import java.text.DecimalFormat;
- import java.text.NumberFormat;
- import java.util.Collections;
- import java.util.Comparator;
- import java.util.LinkedList;
- import java.util.List;
-
- import junit.framework.TestCase;
-
- import org.eclipse.jgit.util.CPUTimeStopWatch;
-
- /**
- * Test cases for the performance of the diff implementation. The tests test
- * that the performance of the MyersDiff algorithm is really O(N*D). Means the
- * time for computing the diff between a and b should depend on the product of
- * a.length+b.length and the number of found differences. The tests compute
- * diffs between chunks of different length, measure the needed time and check
- * that time/(N*D) does not differ more than a certain factor.
- */
- public class MyersDiffPerformanceTest extends TestCase {
- private static final long longTaskBoundary = 5000000000L;
-
- private static final int minCPUTimerTicks = 10;
-
- private static final int maxFactor = 15;
-
- private CPUTimeStopWatch stopwatch=CPUTimeStopWatch.createInstance();
-
- public class PerfData {
- private NumberFormat fmt = new DecimalFormat("#.##E0");
-
- public long runningTime;
-
- public long D;
-
- public long N;
-
- private double p1 = -1;
-
- private double p2 = -1;
-
- public double perf1() {
- if (p1 < 0)
- p1 = runningTime / ((double) N * D);
- return p1;
- }
-
- public double perf2() {
- if (p2 < 0)
- p2 = runningTime / ((double) N * D * D);
- return p2;
- }
-
- public String toString() {
- return ("diffing " + N / 2 + " bytes took " + runningTime
- + " ns. N=" + N + ", D=" + D + ", time/(N*D):"
- + fmt.format(perf1()) + ", time/(N*D^2):" + fmt
- .format(perf2()) + "\n");
- }
- }
-
- public static Comparator<PerfData> getComparator(final int whichPerf) {
- return new Comparator<PerfData>() {
- public int compare(PerfData o1, PerfData o2) {
- double p1 = (whichPerf == 1) ? o1.perf1() : o1.perf2();
- double p2 = (whichPerf == 1) ? o2.perf1() : o2.perf2();
- return (p1 < p2) ? -1 : (p1 > p2) ? 1 : 0;
- }
- };
- }
-
- public void test() {
- if (stopwatch!=null) {
- // run some tests without recording to let JIT do its optimization
- test(10000);
- test(20000);
- test(10000);
- test(20000);
-
- List<PerfData> perfData = new LinkedList<PerfData>();
- perfData.add(test(10000));
- perfData.add(test(20000));
- perfData.add(test(40000));
- perfData.add(test(80000));
- perfData.add(test(160000));
- perfData.add(test(320000));
- perfData.add(test(640000));
- perfData.add(test(1280000));
-
- Comparator<PerfData> c = getComparator(1);
- double factor = Collections.max(perfData, c).perf1()
- / Collections.min(perfData, c).perf1();
- assertTrue(
- "minimun and maximum of performance-index t/(N*D) differed too much. Measured factor of "
- + factor
- + " (maxFactor="
- + maxFactor
- + "). Perfdata=<" + perfData.toString() + ">",
- factor < maxFactor);
- }
- }
-
- /**
- * Tests the performance of MyersDiff for texts which are similar (not
- * random data). The CPU time is measured and returned. Because of bad
- * accuracy of CPU time information the diffs are repeated. During each
- * repetition the interim CPU time is checked. The diff operation is
- * repeated until we have seen the CPU time clock changed its value at least
- * {@link #minCPUTimerTicks} times.
- *
- * @param characters
- * the size of the diffed character sequences.
- * @return performance data
- */
- private PerfData test(int characters) {
- PerfData ret = new PerfData();
- String a = DiffTestDataGenerator.generateSequence(characters, 971, 3);
- String b = DiffTestDataGenerator.generateSequence(characters, 1621, 5);
- CharArray ac = new CharArray(a);
- CharArray bc = new CharArray(b);
- CharCmp cmp = new CharCmp();
- MyersDiff<CharArray> myersDiff = null;
- int cpuTimeChanges = 0;
- long lastReadout = 0;
- long interimTime = 0;
- int repetitions = 0;
- stopwatch.start();
- while (cpuTimeChanges < minCPUTimerTicks && interimTime < longTaskBoundary) {
- myersDiff = new MyersDiff<CharArray>(cmp, ac, bc);
- repetitions++;
- interimTime = stopwatch.readout();
- if (interimTime != lastReadout) {
- cpuTimeChanges++;
- lastReadout = interimTime;
- }
- }
- ret.runningTime = stopwatch.stop() / repetitions;
- ret.N = ac.size() + bc.size();
- ret.D = myersDiff.getEdits().size();
-
- return ret;
- }
-
- private static class CharArray extends Sequence {
- final char[] array;
-
- public CharArray(String s) {
- array = s.toCharArray();
- }
-
- @Override
- public int size() {
- return array.length;
- }
- }
-
- private static class CharCmp extends SequenceComparator<CharArray> {
- @Override
- public boolean equals(CharArray a, int ai, CharArray b, int bi) {
- return a.array[ai] == b.array[bi];
- }
-
- @Override
- public int hash(CharArray seq, int ptr) {
- return seq.array[ptr];
- }
- }
- }
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