baseTest.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.util;

import static org.jenetics.stat.StatisticsAssert.assertUniformDistribution;

import java.util.Random;
import java.util.stream.IntStream;

import org.testng.Assert;
import org.testng.annotations.Test;

import org.jenetics.internal.math.DoubleAdder;
import org.jenetics.internal.math.base;

import org.jenetics.stat.Histogram;

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

	@Test
	public void summarize() {
		final double[] values = new double[150000];
		for (int i = 0; i < values.length; ++i) {
			values[i] = 1.0/values.length;
		}

		Assert.assertEquals(DoubleAdder.sum(values), 1.0);
	}

	@Test
	public void subset() {
		final Random random = new Random();

		for (int i = 1; i < 100; ++i) {
			int[] sub = new int[i];
			base.subset(1000, sub, random);

			Assert.assertTrue(isSortedAndUnique(sub));
		}
	}

	private static boolean isSortedAndUnique(final int[] array) {
		boolean sorted = true;
		for (int i = 0; i < array.length - 1 && sorted; ++i) {
			sorted = array[i] < array[i + 1];
		}
		return sorted;
	}

	@Test(invocationCount = 20, successPercentage = 95)
	public void subSetDistribution() {
		final int[] sub = new int[3];
		final int n = 100_000;

		final Random random = new Random();
		final Histogram<Integer> histogram = Histogram.ofInteger(0, n, 13);

		IntStream.range(0, 10_000)
			.flatMap(i -> IntStream.of(base.subset(n, sub, random)))
			.forEach(histogram::accept);

		assertUniformDistribution(histogram);
	}

	// https://en.wikipedia.org/wiki/Reservoir_sampling
	static void subset(final int n, final int sub[], final Random random) {
		for (int i = 0; i < sub.length; ++i) {
			sub[i] = i;
		}

		for (int i = sub.length; i < n; ++i) {
			final int j = random.nextInt(i);
			if (j < sub.length) {
				sub[j] = i;
			}
		}
	}

}