Delete DiffPerformanceTest

This test isn't that useful.  The better way to evaluate diff
algorithm performance is to run `jgit debug-diff-algorithms` over
real-world repositories, such as linux-2.6.git.  Whenever we modify
an algorithm we should manually verify that its runtime performance
doesn't get any worse than it already is.

Change-Id: I0beed3a5a8a537c958a5a6438a1283f97fa2097a
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

4 files changed, 6 insertions, 352 deletions

diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/DiffPerformanceTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/DiffPerformanceTest.java
deleted file mode 100644
index 17c586f1e0..0000000000
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/DiffPerformanceTest.java
+++ /dev/null
@@ -1,213 +0,0 @@
-/*
- * 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 DiffPerformanceTest 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();
-		int D = 0;
-		int cpuTimeChanges = 0;
-		long lastReadout = 0;
-		long interimTime = 0;
-		int repetitions = 0;
-		stopwatch.start();
-		while (cpuTimeChanges < minCPUTimerTicks && interimTime < longTaskBoundary) {
-			D = MyersDiff.INSTANCE.diff(cmp, ac, bc).size();
-			repetitions++;
-			interimTime = stopwatch.readout();
-			if (interimTime != lastReadout) {
-				cpuTimeChanges++;
-				lastReadout = interimTime;
-			}
-		}
-		ret.runningTime = stopwatch.stop() / repetitions;
-		ret.N = ac.size() + bc.size();
-		ret.D = D;
-
-		return ret;
-	}
-
-	static class CharArray extends Sequence {
-		final char[] array;
-
-		public CharArray(String s) {
-			array = s.toCharArray();
-		}
-
-		@Override
-		public int size() {
-			return array.length;
-		}
-	}
-
-	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];
-		}
-	}
-}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/DiffTestDataGenerator.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/DiffTestDataGenerator.java
deleted file mode 100644
index 91d757bcce..0000000000
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/DiffTestDataGenerator.java
+++ /dev/null
@@ -1,93 +0,0 @@
-/*
- * 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;
-
-public class DiffTestDataGenerator {
-	/**
-	 * Generate sequence of characters in ascending order. The first character
-	 * is a space. All subsequent characters have an ASCII code one greater then
-	 * the ASCII code of the preceding character. On exception: the character
-	 * following which follows '~' is again a ' '.
-	 *
-	 * @param len
-	 *            length of the String to be returned
-	 * @return the sequence of characters as String
-	 */
-	public static String generateSequence(int len) {
-		return generateSequence(len, 0, 0);
-	}
-
-	/**
-	 * Generate sequence of characters similar to the one returned by
-	 * {@link #generateSequence(int)}. But this time in each chunk of
-	 * <skipPeriod> characters the last <skipLength> characters are left out. By
-	 * calling this method twice with two different prime skipPeriod values and
-	 * short skipLength values you create test data which is similar to what
-	 * programmers do to their source code - huge files with only few
-	 * insertions/deletions/changes.
-	 *
-	 * @param len
-	 *            length of the String to be returned
-	 * @param skipPeriod
-	 * @param skipLength
-	 * @return the sequence of characters as String
-	 */
-	public static String generateSequence(int len, int skipPeriod,
-			int skipLength) {
-		StringBuilder text = new StringBuilder(len);
-		int skipStart = skipPeriod - skipLength;
-		int skippedChars = 0;
-		int block = 0;
-		for (int i = 0; i - skippedChars < len; ++i) {
-			if ((i % skipPeriod) == 1)
-				text.append((char) (256 + block++));
-			else if (skipPeriod == 0 || i % skipPeriod < skipStart) {
-				text.append((char) (32 + i % 95));
-			} else {
-				skippedChars++;
-			}
-		}
-		return text.toString();
-	}
-}
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/HistogramDiffTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/HistogramDiffTest.java
index f9353af174..85740e1f8d 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/HistogramDiffTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/HistogramDiffTest.java
@@ -43,8 +43,6 @@
 
 package org.eclipse.jgit.diff;
 
-import org.eclipse.jgit.diff.DiffPerformanceTest.CharArray;
-import org.eclipse.jgit.diff.DiffPerformanceTest.CharCmp;
 
 public class HistogramDiffTest extends AbstractDiffTestCase {
 	@Override
@@ -116,47 +114,21 @@ public class HistogramDiffTest extends AbstractDiffTestCase {
 
 	public void testFallbackToMyersDiff() {
 		HistogramDiff hd = new HistogramDiff();
-		hd.setMaxChainLength(64);
+		hd.setMaxChainLength(4);
 
-		String a = DiffTestDataGenerator.generateSequence(40000, 971, 3);
-		String b = DiffTestDataGenerator.generateSequence(40000, 1621, 5);
-		CharCmp cmp = new CharCmp();
-		CharArray ac = new CharArray(a);
-		CharArray bc = new CharArray(b);
+		RawTextComparator cmp = RawTextComparator.DEFAULT;
+		RawText ac = t("bbbbb");
+		RawText bc = t("AbCbDbEFbZ");
 		EditList r;
 
 		// Without fallback our results are limited due to collisions.
 		hd.setFallbackAlgorithm(null);
 		r = hd.diff(cmp, ac, bc);
-		assertEquals(70, r.size());
+		assertEquals(1, r.size());
 
 		// Results go up when we add a fallback for the high collision regions.
 		hd.setFallbackAlgorithm(MyersDiff.INSTANCE);
 		r = hd.diff(cmp, ac, bc);
-		assertEquals(73, r.size());
-
-		// But they still differ from Myers due to the way we did early steps.
-		EditList myersResult = MyersDiff.INSTANCE.diff(cmp, ac, bc);
-		assertFalse("Not same as Myers", myersResult.equals(r));
-	}
-
-	public void testPerformanceTestDeltaLength() {
-		HistogramDiff hd = new HistogramDiff();
-		hd.setFallbackAlgorithm(null);
-
-		String a = DiffTestDataGenerator.generateSequence(40000, 971, 3);
-		String b = DiffTestDataGenerator.generateSequence(40000, 1621, 5);
-		CharCmp cmp = new CharCmp();
-		CharArray ac = new CharArray(a);
-		CharArray bc = new CharArray(b);
-		EditList r;
-
-		hd.setMaxChainLength(64);
-		r = hd.diff(cmp, ac, bc);
-		assertEquals(70, r.size());
-
-		hd.setMaxChainLength(176);
-		r = hd.diff(cmp, ac, bc);
-		assertEquals(72, r.size());
+		assertEquals(5, r.size());
 	}
 }
diff --git a/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/MyersDiffTest.java b/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/MyersDiffTest.java
index 896b0fbccb..4df2c5a407 100644
--- a/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/MyersDiffTest.java
+++ b/org.eclipse.jgit.test/tst/org/eclipse/jgit/diff/MyersDiffTest.java
@@ -43,21 +43,9 @@
 
 package org.eclipse.jgit.diff;
 
-import org.eclipse.jgit.diff.DiffPerformanceTest.CharArray;
-import org.eclipse.jgit.diff.DiffPerformanceTest.CharCmp;
-
 public class MyersDiffTest extends AbstractDiffTestCase {
 	@Override
 	protected DiffAlgorithm algorithm() {
 		return MyersDiff.INSTANCE;
 	}
-
-	public void testPerformanceTestDeltaLength() {
-		String a = DiffTestDataGenerator.generateSequence(40000, 971, 3);
-		String b = DiffTestDataGenerator.generateSequence(40000, 1621, 5);
-		CharArray ac = new CharArray(a);
-		CharArray bc = new CharArray(b);
-		EditList r = algorithm().diff(new CharCmp(), ac, bc);
-		assertEquals(131, r.size());
-	}
 }