test.it.unimi.dsi.bits.FastTest Maven / Gradle / Ivy

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package it.unimi.dsi.bits;

import static org.junit.Assert.assertEquals;
import it.unimi.dsi.util.SplitMix64RandomGenerator;

import org.junit.Test;

/*
 * DSI utilities
 *
 * Copyright (C) 2010-2017 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 .
 *
 */

public class FastTest {

	@Test
	public void testCeilLog2() {
		for(int i = 1; i < 1000; i++) assertEquals((int)Math.ceil(Math.log(i) / Math.log(2)), Fast.ceilLog2(i));
	}

	@Test
	public void testLength() {
		assertEquals(1, Fast.length(0));
		assertEquals(1, Fast.length(0L));
		for(int i = 1; i < 100; i++) assertEquals(Fast.mostSignificantBit(i) + 1, Fast.length(i));
		for(long i = 1; i < 100; i++) assertEquals(Fast.mostSignificantBit(i) + 1, Fast.length(i));
	}

	@Test
	public void testMostSignificantBitInt() {
		assertEquals(-1, Fast.mostSignificantBit(0));
		for(int i = 0; i < 32; i++) {
			assertEquals(i, Fast.mostSignificantBit(1L << i));
			assertEquals(i, Fast.mostSignificantBit(1L << i | 1));
			assertEquals(i, Fast.mostSignificantBit(1L << i));
			assertEquals(i, Fast.mostSignificantBit(1L << i | 1));
		}
	}

	@Test
	public void testMostSignificantBitLong() {
		assertEquals(-1, Fast.mostSignificantBit(0));
		for(int i = 0; i < 64; i++) {
			assertEquals(i, Fast.mostSignificantBit(1L << i));
			assertEquals(i, Fast.mostSignificantBit(1L << i | 1));
			assertEquals(i, Fast.mostSignificantBit(1L << i));
			assertEquals(i, Fast.mostSignificantBit(1L << i | 1));
		}
	}


	@Test
	public void testSelect2() {
		assertEquals(0, Fast.select(1, 0));
		for(int i = 0; i < 64; i++) assertEquals(i, Fast.select(0xFFFFFFFFFFFFFFFFL, i));
		for(int i = 1; i < 32; i++) assertEquals(2 * i + 1, Fast.select(0xAAAAAAAAAAAAAAAAL, i));
		SplitMix64RandomGenerator r = new SplitMix64RandomGenerator(0);
		for(int i = 100000; i-- != 0;) {
			final long x = r.nextLong();
			final int count = Long.bitCount(x);
			for(int rank = count; rank-- != 0;) assertEquals(Fast.select(x, rank), Fast.select(x, rank));
		}
	}



	@Test
	public void testInt2Nat() {
		assertEquals(Integer.MAX_VALUE, Fast.int2nat(Integer.MIN_VALUE / 2));
		assertEquals(Integer.MAX_VALUE - 2, Fast.int2nat(Integer.MIN_VALUE / 2 + 1));
		assertEquals(Integer.MAX_VALUE - 1, Fast.int2nat(Integer.MAX_VALUE / 2));

		for(int i = 0; i < 16; i++) assertEquals(2*i, Fast.int2nat(i));
		for(int i = -16; i < 0; i++) assertEquals(-2*i-1, Fast.int2nat(i));

		assertEquals(Long.MAX_VALUE, Fast.int2nat(Long.MIN_VALUE / 2));
		assertEquals(Long.MAX_VALUE - 2, Fast.int2nat(Long.MIN_VALUE / 2 + 1));
		assertEquals(Long.MAX_VALUE - 1, Fast.int2nat(Long.MAX_VALUE / 2));

		for(int i = 0; i < 16; i++) assertEquals(2L*i, Fast.int2nat(i));
		for(int i = -16; i < 0; i++) assertEquals(-2L*i-1, Fast.int2nat(i));
	}

	@Test
	public void testNat2Int() {
		assertEquals(Integer.MIN_VALUE / 2, Fast.nat2int(Integer.MAX_VALUE));
		assertEquals(Integer.MIN_VALUE / 2 + 1, Fast.nat2int(Integer.MAX_VALUE - 2));
		assertEquals(Integer.MAX_VALUE / 2, Fast.nat2int(Integer.MAX_VALUE - 1));

		for(int i = 0; i < 16; i++) assertEquals(i, Fast.nat2int(2*i));
		for(int i = -16; i < 0; i++) assertEquals(i, Fast.nat2int(-2*i-1));

		assertEquals(Long.MIN_VALUE / 2 + 1, Fast.nat2int(Long.MAX_VALUE - 2));
		assertEquals(Long.MIN_VALUE / 2, Fast.nat2int(Long.MAX_VALUE));
		assertEquals(Long.MAX_VALUE / 2, Fast.nat2int(Long.MAX_VALUE - 1));

		for(int i = 0; i < 16; i++) assertEquals(i, Fast.nat2int(2L*i));
		for(int i = -16; i < 0; i++) assertEquals(i, Fast.nat2int(-2L*i-1));

	}
}