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The DSI utilities are a mishmash of classes accumulated during the last twenty years in projects developed at the DSI (Dipartimento di Scienze dell'Informazione, i.e., Information Sciences Department), now DI (Dipartimento di Informatica, i.e., Informatics Department), of the Universita` degli Studi di Milano.

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package it.unimi.dsi.util;

/*
 * DSI utilities
 *
 * Copyright (C) 2014-2019 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;


public class XoShiRo256PlusPlusRandomTest {
	private final static long seeds[] = { 0, 1, 1024, 0x5555555555555555L };

	@Test
	public void testNextFloat() {
		for (final long seed : seeds) {
			final XoShiRo256PlusPlusRandom xoshiro = new XoShiRo256PlusPlusRandom(seed);
			double avg = 0;
			for (int i = 1000000; i-- != 0;) {
				final float d = xoshiro.nextFloat();
				assertTrue(Float.toString(d), d < 1);
				assertTrue(Float.toString(d), d >= 0);
				avg += d;
			}

			assertEquals(500000, avg, 1000);
		}
	}

	@Test
	public void testNextDouble() {
		for (final long seed : seeds) {
			final XoShiRo256PlusPlusRandom xoshiro = new XoShiRo256PlusPlusRandom(seed);
			double avg = 0;
			for (int i = 1000000; i-- != 0;) {
				final double d = xoshiro.nextDouble();
				assertTrue(d < 1);
				assertTrue(d >= 0);
				avg += d;
			}

			assertEquals(500000, avg, 1000);
		}
	}

	@Test
	public void testNextDoubleFast() {
		for (final long seed : seeds) {
			final XoShiRo256PlusPlusRandom xoshiro = new XoShiRo256PlusPlusRandom(seed);
			double avg = 0;
			for (int i = 1000000; i-- != 0;) {
				final double d = xoshiro.nextDoubleFast();
				assertTrue(d < 1);
				assertTrue(d >= 0);
				avg += d;
			}

			assertEquals(500000, avg, 1000);
		}
	}

	@Test
	public void testNextInt() {
		for (final long seed : seeds) {
			final XoShiRo256PlusPlusRandom xoshiro = new XoShiRo256PlusPlusRandom(seed);
			double avg = 0;
			for (int i = 100000000; i-- != 0;) {
				final int d = xoshiro.nextInt(101);
				assertTrue(d <= 100);
				assertTrue(d >= 0);
				avg += d;
			}

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

	@Test
	public void testNextInt2() {
		for (final long seed : seeds) {
			final XoShiRo256PlusPlusRandom xoshiro = new XoShiRo256PlusPlusRandom(seed);
			final int[] count = new int[32];
			long change = 0;
			int prev = 0;
			for (int i = 1000000; i-- != 0;) {
				final int d = xoshiro.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, 38000);
			for (int b = 32; b-- != 0;) assertEquals(500000, count[b], 2000);
		}
	}

	@Test
	public void testNextInt3() {
		final XoShiRo256PlusPlusRandom xoshiro = new XoShiRo256PlusPlusRandom(0);
		for(int i = 0; i < 100; i++) assertTrue(xoshiro.nextInt(16) < 16);
	}

	@Test
	public void testNextInt4() {
		final XoShiRo256PlusPlusRandom xoshiro = new XoShiRo256PlusPlusRandom(0);
		assertEquals(0, xoshiro.nextInt(1));
	}


	@Test
	public void testNextLong() {
		for (final long seed : seeds) {
			final XoShiRo256PlusPlusRandom xoshiro = new XoShiRo256PlusPlusRandom(seed);
			final int[] count = new int[64];
			long change = 0;
			long prev = 0;
			for (int i = 1000000; i-- != 0;) {
				final long d = xoshiro.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, 6000);
			for (int b = 64; b-- != 0;) assertEquals(500000, count[b], 2000);
		}
	}

	@Test
	public void testRight() {
		final long[] init = { 0x7743a154e17a5e9bL, 0x7823a1cd9453899bL, 0x976589eefbb1c7f5L, 0x702cf168260fa29eL };
		final long[] orbit = { 0xd5c766557e6e16e4L, 0xf8eb8f8747a8cc67L, 0xfc18365710a653eeL, 0xc698a193593f232L, 0xa44ddeaac93b1be7L, 0x678dcd0e0516c741L, 0x351d94668d7c35eL, 0x73160e24fc8768daL, 0x562ca11220c31698L, 0x3dba336235c48913L };
		final XoShiRo256PlusPlusRandom xoshiro = new XoShiRo256PlusPlusRandom();
		xoshiro.setState(init);
		for(int i = 0; i < 10; i++) assertEquals(orbit[i], xoshiro.nextLong());
		xoshiro.setState(init);
		xoshiro.jump();
 		final long[] jump = { 0x39c4396d8759c874L, 0x4b948d9de69752ecL, 0x871591604b03d9a6L, 0x444d6d471322d17bL, 0xb0a9eb9383bf0803L, 0x481f6c796c1d0ecaL, 0xb89a346b480341bfL, 0x1494bad1d1b19126L, 0xa2f5ca0a0ab0805L, 0x75a4de1da308cc8fL };
		for(int i = 0; i < 10; i++) assertEquals(jump[i], xoshiro.nextLong());
		xoshiro.setState(init);
		xoshiro.longJump();
		final long[] longJump = { 0xea14aabc151743b5L, 0x8941269998260040L, 0x4cf6a8517950ced8L, 0x2c657736be0af94cL, 0x9ce62322d721ea8fL, 0x6f2e0950267a4252L, 0x5ac6463cf03b2904L, 0x630400b3a65ac6c0L, 0xa220c012240ddeb0L, 0x9b1b712840162f46L };
		for(int i = 0; i < 10; i++) assertEquals(longJump[i], xoshiro.nextLong());
	}
}