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1   /*
2    * Copyright (C) 2019, Matthias Sohn <matthias.sohn@sap.com>
3    * and other copyright owners as documented in the project's IP log.
4    *
5    * This program and the accompanying materials are made available
6    * under the terms of the Eclipse Distribution License v1.0 which
7    * accompanies this distribution, is reproduced below, and is
8    * available at http://www.eclipse.org/org/documents/edl-v10.php
9    *
10   * All rights reserved.
11   *
12   * Redistribution and use in source and binary forms, with or
13   * without modification, are permitted provided that the following
14   * conditions are met:
15   *
16   * - Redistributions of source code must retain the above copyright
17   *   notice, this list of conditions and the following disclaimer.
18   *
19   * - Redistributions in binary form must reproduce the above
20   *   copyright notice, this list of conditions and the following
21   *   disclaimer in the documentation and/or other materials provided
22   *   with the distribution.
23   *
24   * - Neither the name of the Eclipse Foundation, Inc. nor the
25   *   names of its contributors may be used to endorse or promote
26   *   products derived from this software without specific prior
27   *   written permission.
28   *
29   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30   * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31   * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33   * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34   * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36   * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37   * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38   * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40   * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42   */
43  package org.eclipse.jgit.util;
44  
45  import static org.junit.Assert.assertEquals;
46  import static org.junit.Assert.assertTrue;
47  
48  import org.eclipse.jgit.util.Stats;
49  import org.junit.Test;
50  
51  public class StatsTest {
52  	@Test
53  	public void testStatsTrivial() {
54  		Stats s = new Stats();
55  		s.add(1);
56  		s.add(1);
57  		s.add(1);
58  		assertEquals(3, s.count());
59  		assertEquals(1.0, s.min(), 1E-6);
60  		assertEquals(1.0, s.max(), 1E-6);
61  		assertEquals(1.0, s.avg(), 1E-6);
62  		assertEquals(0.0, s.var(), 1E-6);
63  		assertEquals(0.0, s.stddev(), 1E-6);
64  	}
65  
66  	@Test
67  	public void testStats() {
68  		Stats s = new Stats();
69  		s.add(1);
70  		s.add(2);
71  		s.add(3);
72  		s.add(4);
73  		assertEquals(4, s.count());
74  		assertEquals(1.0, s.min(), 1E-6);
75  		assertEquals(4.0, s.max(), 1E-6);
76  		assertEquals(2.5, s.avg(), 1E-6);
77  		assertEquals(1.666667, s.var(), 1E-6);
78  		assertEquals(1.290994, s.stddev(), 1E-6);
79  	}
80  
81  	@Test
82  	/**
83  	 * see
84  	 * https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Example
85  	 */
86  	public void testStatsCancellationExample1() {
87  		Stats s = new Stats();
88  		s.add(1E8 + 4);
89  		s.add(1E8 + 7);
90  		s.add(1E8 + 13);
91  		s.add(1E8 + 16);
92  		assertEquals(4, s.count());
93  		assertEquals(1E8 + 4, s.min(), 1E-6);
94  		assertEquals(1E8 + 16, s.max(), 1E-6);
95  		assertEquals(1E8 + 10, s.avg(), 1E-6);
96  		assertEquals(30, s.var(), 1E-6);
97  		assertEquals(5.477226, s.stddev(), 1E-6);
98  	}
99  
100 	@Test
101 	/**
102 	 * see
103 	 * https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Example
104 	 */
105 	public void testStatsCancellationExample2() {
106 		Stats s = new Stats();
107 		s.add(1E9 + 4);
108 		s.add(1E9 + 7);
109 		s.add(1E9 + 13);
110 		s.add(1E9 + 16);
111 		assertEquals(4, s.count());
112 		assertEquals(1E9 + 4, s.min(), 1E-6);
113 		assertEquals(1E9 + 16, s.max(), 1E-6);
114 		assertEquals(1E9 + 10, s.avg(), 1E-6);
115 		assertEquals(30, s.var(), 1E-6);
116 		assertEquals(5.477226, s.stddev(), 1E-6);
117 	}
118 
119 	@Test
120 	public void testNoValues() {
121 		Stats s = new Stats();
122 		assertTrue(Double.isNaN(s.var()));
123 		assertTrue(Double.isNaN(s.stddev()));
124 		assertTrue(Double.isNaN(s.avg()));
125 		assertTrue(Double.isNaN(s.min()));
126 		assertTrue(Double.isNaN(s.max()));
127 		s.add(42.3);
128 		assertTrue(Double.isNaN(s.var()));
129 		assertTrue(Double.isNaN(s.stddev()));
130 		assertEquals(42.3, s.avg(), 1E-6);
131 		assertEquals(42.3, s.max(), 1E-6);
132 		assertEquals(42.3, s.min(), 1E-6);
133 		s.add(42.3);
134 		assertEquals(0, s.var(), 1E-6);
135 		assertEquals(0, s.stddev(), 1E-6);
136 	}
137 }