001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017
018package org.apache.commons.rng.core.source64;
019
020/**
021 * A fast all-purpose 64-bit generator.
022 *
023 * <p>This is a member of the Xor-Shift-Rotate family of generators. Memory footprint is 128 bits
024 * and the period is 2<sup>128</sup>-1. Speed is expected to be similar to
025 * {@link XoShiRo256StarStar}.</p>
026 *
027 * @see <a href="http://xoshiro.di.unimi.it/xoroshiro128starstar.c">Original source code</a>
028 * @see <a href="http://xoshiro.di.unimi.it/">xorshiro / xoroshiro generators</a>
029 * @since 1.3
030 */
031public class XoRoShiRo128StarStar extends AbstractXoRoShiRo128 {
032    /**
033     * Creates a new instance.
034     *
035     * @param seed Initial seed.
036     * If the length is larger than 2, only the first 2 elements will
037     * be used; if smaller, the remaining elements will be automatically
038     * set. A seed containing all zeros will create a non-functional generator.
039     */
040    public XoRoShiRo128StarStar(long[] seed) {
041        super(seed);
042    }
043
044    /**
045     * Creates a new instance using a 2 element seed.
046     * A seed containing all zeros will create a non-functional generator.
047     *
048     * @param seed0 Initial seed element 0.
049     * @param seed1 Initial seed element 1.
050     */
051    public XoRoShiRo128StarStar(long seed0, long seed1) {
052        super(seed0, seed1);
053    }
054
055    /**
056     * Creates a copy instance.
057     *
058     * @param source Source to copy.
059     */
060    protected XoRoShiRo128StarStar(XoRoShiRo128StarStar source) {
061        super(source);
062    }
063
064    /** {@inheritDoc} */
065    @Override
066    protected long nextOutput() {
067        return Long.rotateLeft(state0 * 5, 7) * 9;
068    }
069
070    /** {@inheritDoc} */
071    @Override
072    protected XoRoShiRo128StarStar copy() {
073        // This exists to ensure the jump function performed in the super class returns
074        // the correct class type. It should not be public.
075        return new XoRoShiRo128StarStar(this);
076    }
077}