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/*
* Copyright (C) 2019, Matthias Sohn <matthias.sohn@sap.com> and others
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Distribution License v. 1.0 which is available at
* https://www.eclipse.org/org/documents/edl-v10.php.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
package org.eclipse.jgit.util;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import org.junit.Test;
public class StatsTest {
@Test
public void testStatsTrivial() {
Stats s = new Stats();
s.add(1);
s.add(1);
s.add(1);
assertEquals(3, s.count());
assertEquals(1.0, s.min(), 1E-6);
assertEquals(1.0, s.max(), 1E-6);
assertEquals(1.0, s.avg(), 1E-6);
assertEquals(0.0, s.var(), 1E-6);
assertEquals(0.0, s.stddev(), 1E-6);
}
@Test
public void testStats() {
Stats s = new Stats();
s.add(1);
s.add(2);
s.add(3);
s.add(4);
assertEquals(4, s.count());
assertEquals(1.0, s.min(), 1E-6);
assertEquals(4.0, s.max(), 1E-6);
assertEquals(2.5, s.avg(), 1E-6);
assertEquals(1.666667, s.var(), 1E-6);
assertEquals(1.290994, s.stddev(), 1E-6);
}
@Test
/**
* see
* https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Example
*/
public void testStatsCancellationExample1() {
Stats s = new Stats();
s.add(1E8 + 4);
s.add(1E8 + 7);
s.add(1E8 + 13);
s.add(1E8 + 16);
assertEquals(4, s.count());
assertEquals(1E8 + 4, s.min(), 1E-6);
assertEquals(1E8 + 16, s.max(), 1E-6);
assertEquals(1E8 + 10, s.avg(), 1E-6);
assertEquals(30, s.var(), 1E-6);
assertEquals(5.477226, s.stddev(), 1E-6);
}
@Test
/**
* see
* https://en.wikipedia.org/wiki/Algorithms_for_calculating_variance#Example
*/
public void testStatsCancellationExample2() {
Stats s = new Stats();
s.add(1E9 + 4);
s.add(1E9 + 7);
s.add(1E9 + 13);
s.add(1E9 + 16);
assertEquals(4, s.count());
assertEquals(1E9 + 4, s.min(), 1E-6);
assertEquals(1E9 + 16, s.max(), 1E-6);
assertEquals(1E9 + 10, s.avg(), 1E-6);
assertEquals(30, s.var(), 1E-6);
assertEquals(5.477226, s.stddev(), 1E-6);
}
@Test
public void testNoValues() {
Stats s = new Stats();
assertTrue(Double.isNaN(s.var()));
assertTrue(Double.isNaN(s.stddev()));
assertTrue(Double.isNaN(s.avg()));
assertTrue(Double.isNaN(s.min()));
assertTrue(Double.isNaN(s.max()));
s.add(42.3);
assertTrue(Double.isNaN(s.var()));
assertTrue(Double.isNaN(s.stddev()));
assertEquals(42.3, s.avg(), 1E-6);
assertEquals(42.3, s.max(), 1E-6);
assertEquals(42.3, s.min(), 1E-6);
s.add(42.3);
assertEquals(0, s.var(), 1E-6);
assertEquals(0, s.stddev(), 1E-6);
}
}
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