test.it.unimi.dsi.util.XorShift128PlusRandomTest Maven / Gradle / Ivy

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package it.unimi.dsi.util;

/*
 * DSI utilities
 *
 * Copyright (C) 2014-2017 Sebastiano Vigna
 *
 *  This library is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU Lesser General Public License as published by the Free
 *  Software Foundation; either version 3 of the License, or (at your option)
 *  any later version.
 *
 *  This library is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 *  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program; if not, see .
 *
 */


import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;

import org.junit.Test;


@SuppressWarnings("deprecation")
public class XorShift128PlusRandomTest {
	private final static long seeds[] = { 0, 1, 1024, 0x5555555555555555L };

	@Test
	public void testNextFloat() {
		for (long seed : seeds) {
			XorShift128PlusRandom xorShiftRandom = new XorShift128PlusRandom(seed);
			double avg = 0;
			for (int i = 1000000; i-- != 0;) {
				float d = xorShiftRandom.nextFloat();
				assertTrue(d < 1);
				assertTrue(d >= 0);
				avg += d;
			}

			assertEquals(500000, avg, 1000);
		}
	}

	@Test
	public void testNextDouble() {
		for (long seed : seeds) {
			XorShift128PlusRandom xorShiftRandom = new XorShift128PlusRandom(seed);
			double avg = 0;
			for (int i = 1000000; i-- != 0;) {
				double d = xorShiftRandom.nextDouble();
				assertTrue(d < 1);
				assertTrue(d >= 0);
				avg += d;
			}

			assertEquals(500000, avg, 1000);
		}
	}

	@Test
	public void testNextInt() {
		for (long seed : seeds) {
			XorShift128PlusRandom xorShiftRandom = new XorShift128PlusRandom(seed);
			double avg = 0;
			for (int i = 100000000; i-- != 0;) {
				int d = xorShiftRandom.nextInt(101);
				assertTrue(d <= 100);
				assertTrue(d >= 0);
				avg += d;
			}

			assertEquals(5000000000L, avg, 1000000);
		}
	}

	@Test
	public void testNextInt2() {
		for (long seed : seeds) {
			XorShift128PlusRandom xorShiftRandom = new XorShift128PlusRandom(seed);
			final int[] count = new int[32];
			long change = 0;
			int prev = 0;
			for (int i = 1000000; i-- != 0;) {
				int d = xorShiftRandom.nextInt();
				change += Long.bitCount(d ^ prev);
				for (int b = 32; b-- != 0;)
					if ((d & (1 << b)) != 0) count[b]++;
				prev = d;
			}

			assertEquals(32 * 1000000L, change, 31000);
			for (int b = 32; b-- != 0;) assertEquals(500000, count[b], 2000);
		}
	}

	@Test
	public void testNextLong() {
		for (long seed : seeds) {
			XorShift128PlusRandom xorShiftRandom = new XorShift128PlusRandom(seed);
			final int[] count = new int[64];
			long change = 0;
			long prev = 0;
			for (int i = 1000000; i-- != 0;) {
				long d = xorShiftRandom.nextLong();
				change += Long.bitCount(d ^ prev);
				for (int b = 64; b-- != 0;)
					if ((d & (1L << b)) != 0) count[b]++;
				prev = d;
			}

			assertEquals(32 * 1000000L, change, 7000);
			for (int b = 64; b-- != 0;) assertEquals(500000, count[b], 2000);
		}
	}
}