DoubleMomentStatisticsTest.java

/*
 * Java Genetic Algorithm Library (@__identifier__@).
 * Copyright (c) @__year__@ Franz Wilhelmstötter
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Author:
 *    Franz Wilhelmstötter (franz.wilhelmstoetter@gmx.at)
 */
package org.jenetics.stat;

import static org.jenetics.stat.DoubleMomentStatistics.toDoubleMomentStatistics;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import org.apache.commons.math3.stat.descriptive.DescriptiveStatistics;
import org.testng.Assert;
import org.testng.annotations.DataProvider;
import org.testng.annotations.Test;

/**
 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
 */
public class DoubleMomentStatisticsTest {

	private List<Double> numbers(final int size) {
		final Random random = new Random(123);
		final List<Double> numbers = new ArrayList<>(size);
		for (int i = 0; i < size; ++i) {
			numbers.add(random.nextDouble());
		}

		return numbers;
	}

	@Test(dataProvider = "sampleCounts")
	public void summary(final Integer sampleCounts, final Double epsilon) {
		final List<Double> numbers = numbers(sampleCounts);

		final DescriptiveStatistics expected = new DescriptiveStatistics();
		numbers.forEach(expected::addValue);

		final DoubleMomentStatistics summary = numbers.stream()
			.collect(toDoubleMomentStatistics(Double::doubleValue));

		Assert.assertEquals(summary.getCount(), numbers.size());
		assertEqualsDouble(min(summary.getMin()), expected.getMin(), 0.0);
		assertEqualsDouble(max(summary.getMax()), expected.getMax(), 0.0);
		assertEqualsDouble(summary.getSum(), expected.getSum(), epsilon);
		assertEqualsDouble(summary.getMean(), expected.getMean(), epsilon);
		assertEqualsDouble(summary.getVariance(), expected.getVariance(), epsilon);
		assertEqualsDouble(summary.getSkewness(), expected.getSkewness(), epsilon);
		assertEqualsDouble(summary.getKurtosis(), expected.getKurtosis(), epsilon);
	}

	@Test(dataProvider = "parallelSampleCounts")
	public void parallelSummary(final Integer sampleCounts, final Double epsilon) {
		final List<Double> numbers = numbers(sampleCounts);

		final DescriptiveStatistics expected = new DescriptiveStatistics();
		numbers.forEach(expected::addValue);

		final DoubleMomentStatistics summary = numbers.parallelStream()
			.collect(toDoubleMomentStatistics(Double::doubleValue));

		Assert.assertEquals(summary.getCount(), numbers.size());
		assertEqualsDouble(min(summary.getMin()), expected.getMin(), 0.0);
		assertEqualsDouble(max(summary.getMax()), expected.getMax(), 0.0);
		assertEqualsDouble(summary.getSum(), expected.getSum(), epsilon);
		assertEqualsDouble(summary.getMean(), expected.getMean(), epsilon);
		assertEqualsDouble(summary.getVariance(), expected.getVariance(), epsilon);
		assertEqualsDouble(summary.getSkewness(), expected.getSkewness(), epsilon);
		assertEqualsDouble(summary.getKurtosis(), expected.getKurtosis(), epsilon);
	}

	private static double min(final double value) {
		return value == Double.POSITIVE_INFINITY ? Double.NaN : value;
	}

	private static double max(final double value) {
		return value == Double.NEGATIVE_INFINITY ? Double.NaN : value;
	}

	private static void assertEqualsDouble(final double a, final double b, final double e) {
		if (Double.isNaN(b)) {
			Assert.assertTrue(
				Double.isNaN(a),
				String.format("Expected: Double.NaN \nActual: %s", a)
			);
		} else {
			Assert.assertEquals(a, b, e);
		}
	}

	@DataProvider(name = "sampleCounts")
	public Object[][] sampleCounts() {
		return new Object[][] {
			{0, 0.0},
			{1, 0.0},
			{2, 0.05},
			{3, 0.05},
			{100, 0.05},
			{1_000, 0.0001},
			{10_000, 0.00001},
			{100_000, 0.000001},
			{1_000_000, 0.0000001},
			{2_000_000, 0.0000005}
		};
	}

	@DataProvider(name = "parallelSampleCounts")
	public Object[][] parallelSampleCounts() {
		return new Object[][] {
			{0, 0.0},
			{1, 0.0},
			{2, 0.05},
			{3, 0.05},
			{100, 0.5},
			{1_0, 0.003},
			{10_000, 0.00001},
			{100_000, 0.000001},
			{1_000_000, 0.0000001},
			{2_000_000, 0.0000005}
		};
	}

}