Add performance tests for MyersDiff
Add some tests which make sure that the diff algorithm really behaves in the promised O(N*D) manner. This tests compute diffs between multiple big chunks of data, measure time for computing the diffs and fail if the measured times are off O(N*D) by more than a factor 10 Signed-off-by: Christian Halstrick <christian.halstrick@sap.com> Change-Id: I8e1e0be60299472828718371b231f1d8a9dc21a7 Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>
This commit is contained in:
Christian Halstrick
Robin Rosenberg
parent
2484ad6fe0
commit
b0772d7a5c
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/*
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* Copyright (C) 2009, Christian Halstrick <christian.halstrick@sap.com>
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* and other copyright owners as documented in the project's IP log.
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*
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* This program and the accompanying materials are made available
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* under the terms of the Eclipse Distribution License v1.0 which
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* accompanies this distribution, is reproduced below, and is
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* available at http://www.eclipse.org/org/documents/edl-v10.php
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials provided
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* with the distribution.
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*
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* - Neither the name of the Eclipse Foundation, Inc. nor the
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* names of its contributors may be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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package org.eclipse.jgit.diff;
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public class DiffTestDataGenerator {
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/**
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* Generate sequence of characters in ascending order. The first character
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* is a space. All subsequent characters have an ASCII code one greater then
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* the ASCII code of the preceding character. On exception: the character
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* following which follows '~' is again a ' '.
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*
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* @param len
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* length of the String to be returned
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* @return the sequence of characters as String
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*/
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public static String generateSequence(int len) {
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return generateSequence(len, 0, 0);
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}
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/**
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* Generate sequence of characters similar to the one returned by
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* {@link #generateSequence(int)}. But this time in each chunk of
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* <skipPeriod> characters the last <skipLength> characters are left out. By
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* calling this method twice with two different prime skipPeriod values and
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* short skipLength values you create test data which is similar to what
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* programmers do to their source code - huge files with only few
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* insertions/deletions/changes.
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*
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* @param len
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* length of the String to be returned
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* @param skipPeriod
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* @param skipLength
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* @return the sequence of characters as String
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*/
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public static String generateSequence(int len, int skipPeriod,
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int skipLength) {
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StringBuilder text = new StringBuilder(len);
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int skipStart = skipPeriod - skipLength;
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int skippedChars = 0;
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for (int i = 0; i - skippedChars < len; ++i) {
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if (skipPeriod == 0 || i % skipPeriod < skipStart) {
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text.append((char) (32 + i % 95));
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} else {
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skippedChars++;
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}
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}
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return text.toString();
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}
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}
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@ -0,0 +1,196 @@
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/*
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* Copyright (C) 2009, Christian Halstrick <christian.halstrick@sap.com>
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* and other copyright owners as documented in the project's IP log.
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*
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* This program and the accompanying materials are made available
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* under the terms of the Eclipse Distribution License v1.0 which
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* accompanies this distribution, is reproduced below, and is
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* available at http://www.eclipse.org/org/documents/edl-v10.php
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials provided
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* with the distribution.
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*
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* - Neither the name of the Eclipse Foundation, Inc. nor the
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* names of its contributors may be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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package org.eclipse.jgit.diff;
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import java.text.DecimalFormat;
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import java.text.NumberFormat;
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import java.util.Collections;
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import java.util.Comparator;
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import java.util.LinkedList;
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import java.util.List;
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import junit.framework.TestCase;
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import org.eclipse.jgit.util.CPUTimeStopWatch;
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/**
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* Test cases for the performance of the diff implementation. The tests test
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* that the performance of the MyersDiff algorithm is really O(N*D). Means the
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* time for computing the diff between a and b should depend on the product of
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* a.length+b.length and the number of found differences. The tests compute
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* diffs between chunks of different length, measure the needed time and check
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* that time/(N*D) does not differ more than a certain factor (currently 10)
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*/
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public class MyersDiffPerformanceTest extends TestCase {
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private static final long longTaskBoundary = 5000000000L;
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private static final int minCPUTimerTicks = 10;
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private static final int maxFactor = 15;
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private CPUTimeStopWatch stopwatch=CPUTimeStopWatch.createInstance();
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public class PerfData {
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private NumberFormat fmt = new DecimalFormat("#.##E0");
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public long runningTime;
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public long D;
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public long N;
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private double p1 = -1;
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private double p2 = -1;
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public double perf1() {
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if (p1 < 0)
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p1 = runningTime / ((double) N * D);
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return p1;
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}
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public double perf2() {
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if (p2 < 0)
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p2 = runningTime / ((double) N * D * D);
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return p2;
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}
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public String toString() {
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return ("diffing " + N / 2 + " bytes took " + runningTime
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+ " ns. N=" + N + ", D=" + D + ", time/(N*D):"
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+ fmt.format(perf1()) + ", time/(N*D^2):" + fmt
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.format(perf2()));
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}
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}
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public static Comparator<PerfData> getComparator(final int whichPerf) {
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return new Comparator<PerfData>() {
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public int compare(PerfData o1, PerfData o2) {
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double p1 = (whichPerf == 1) ? o1.perf1() : o1.perf2();
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double p2 = (whichPerf == 1) ? o2.perf1() : o2.perf2();
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return (p1 < p2) ? -1 : (p1 > p2) ? 1 : 0;
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}
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};
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}
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public void test() {
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if (stopwatch!=null) {
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List<PerfData> perfData = new LinkedList<PerfData>();
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perfData.add(test(10000));
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perfData.add(test(20000));
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perfData.add(test(50000));
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perfData.add(test(80000));
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perfData.add(test(99999));
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perfData.add(test(999999));
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Comparator<PerfData> c = getComparator(1);
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double factor = Collections.max(perfData, c).perf1()
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/ Collections.min(perfData, c).perf1();
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assertTrue(
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"minimun and maximum of performance-index t/(N*D) differed too much. Measured factor of "
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+ factor
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+ " (maxFactor="
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+ maxFactor
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+ "). Perfdata=<" + perfData.toString() + ">",
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factor < maxFactor);
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}
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}
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/**
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* Tests the performance of MyersDiff for texts which are similar (not
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* random data). The CPU time is measured and returned. Because of bad
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* accuracy of CPU time information the diffs are repeated. During each
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* repetition the interim CPU time is checked. The diff operation is
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* repeated until we have seen the CPU time clock changed its value at least
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* {@link #minCPUTimerTicks} times.
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*
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* @param characters
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* the size of the diffed character sequences.
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* @return performance data
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*/
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private PerfData test(int characters) {
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PerfData ret = new PerfData();
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String a = DiffTestDataGenerator.generateSequence(characters, 971, 3);
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String b = DiffTestDataGenerator.generateSequence(characters, 1621, 5);
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CharArray ac = new CharArray(a);
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CharArray bc = new CharArray(b);
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MyersDiff myersDiff = null;
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int cpuTimeChanges = 0;
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long lastReadout = 0;
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long interimTime = 0;
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int repetitions = 0;
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stopwatch.start();
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while (cpuTimeChanges < minCPUTimerTicks && interimTime < longTaskBoundary) {
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myersDiff = new MyersDiff(ac, bc);
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repetitions++;
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interimTime = stopwatch.readout();
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if (interimTime != lastReadout) {
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cpuTimeChanges++;
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lastReadout = interimTime;
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}
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}
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ret.runningTime = stopwatch.stop() / repetitions;
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ret.N = (ac.size() + bc.size());
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ret.D = myersDiff.getEdits().size();
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return ret;
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}
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private static class CharArray implements Sequence {
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private final char[] array;
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public CharArray(String s) {
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array = s.toCharArray();
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}
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public int size() {
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return array.length;
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}
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public boolean equals(int i, Sequence other, int j) {
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CharArray o = (CharArray) other;
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return array[i] == o.array[j];
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}
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}
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}
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@ -0,0 +1,111 @@
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/*
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* Copyright (C) 2009, Christian Halstrick <christian.halstrick@sap.com>
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* and other copyright owners as documented in the project's IP log.
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*
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* This program and the accompanying materials are made available
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* under the terms of the Eclipse Distribution License v1.0 which
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* accompanies this distribution, is reproduced below, and is
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* available at http://www.eclipse.org/org/documents/edl-v10.php
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* - Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials provided
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* with the distribution.
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*
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* - Neither the name of the Eclipse Foundation, Inc. nor the
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* names of its contributors may be used to endorse or promote
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* products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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* ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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package org.eclipse.jgit.util;
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import java.lang.management.ManagementFactory;
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import java.lang.management.ThreadMXBean;
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/**
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* A simple stopwatch which measures elapsed CPU time of the current thread. CPU
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* time is the time spent on executing your own code plus the time spent on
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* executing operating system calls triggered by your application.
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* <p>
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* This stopwatch needs a VM which supports getting CPU Time information for the
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* current thread. The static method createInstance() will take care to return
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* only a new instance of this class if the VM is capable of returning CPU time.
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*/
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public class CPUTimeStopWatch {
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private long start;
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private static ThreadMXBean mxBean=ManagementFactory.getThreadMXBean();
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/**
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* use this method instead of the constructor to be sure that the underlying
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* VM provides all features needed by this class.
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*
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* @return a new instance of {@link #CPUTimeStopWatch()} or
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* <code>null</code> if the VM does not support getting CPU time
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* information
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*/
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public static CPUTimeStopWatch createInstance() {
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return mxBean.isCurrentThreadCpuTimeSupported() ? new CPUTimeStopWatch()
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: null;
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}
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/**
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* Starts the stopwatch. If the stopwatch is already started this will
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* restart the stopwatch.
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*/
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public void start() {
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start = mxBean.getCurrentThreadCpuTime();
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}
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/**
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* Stops the stopwatch and return the elapsed CPU time in nanoseconds.
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* Should be called only on started stopwatches.
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*
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* @return the elapsed CPU time in nanoseconds. When called on non-started
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* stopwatches (either because {@link #start()} was never called or
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* {@link #stop()} was called after the last call to
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* {@link #start()}) this method will return 0.
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*/
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public long stop() {
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long cpuTime = readout();
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start = 0;
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return cpuTime;
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}
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/**
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* Return the elapsed CPU time in nanoseconds. In contrast to
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* {@link #stop()} the stopwatch will continue to run after this call.
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*
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* @return the elapsed CPU time in nanoseconds. When called on non-started
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* stopwatches (either because {@link #start()} was never called or
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* {@link #stop()} was called after the last call to
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* {@link #start()}) this method will return 0.
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*/
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public long readout() {
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return (start == 0) ? 0 : mxBean.getCurrentThreadCpuTime() - start;
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}
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}
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