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 64-bit generator suitable for {@code double} generation. This is slightly faster than the
022 * all-purpose generator {@link XoRoShiRo128StarStar}.
023 *
024 * <p>This is a member of the Xor-Shift-Rotate family of generators. Memory footprint is 128 bits
025 * and the period is 2<sup>128</sup>-1. Speed is expected to be similar to
026 * {@link XoShiRo256Plus}.</p>
027 *
028 * @see <a href="http://xoshiro.di.unimi.it/xoroshiro128plus.c">Original source code</a>
029 * @see <a href="http://xoshiro.di.unimi.it/">xorshiro / xoroshiro generators</a>
030 * @since 1.3
031 */
032public class XoRoShiRo128Plus extends AbstractXoRoShiRo128 {
033    /**
034     * Creates a new instance.
035     *
036     * @param seed Initial seed.
037     * If the length is larger than 2, only the first 2 elements will
038     * be used; if smaller, the remaining elements will be automatically
039     * set. A seed containing all zeros will create a non-functional generator.
040     */
041    public XoRoShiRo128Plus(long[] seed) {
042        super(seed);
043    }
044
045    /**
046     * Creates a new instance using a 2 element seed.
047     * A seed containing all zeros will create a non-functional generator.
048     *
049     * @param seed0 Initial seed element 0.
050     * @param seed1 Initial seed element 1.
051     */
052    public XoRoShiRo128Plus(long seed0, long seed1) {
053        super(seed0, seed1);
054    }
055
056    /**
057     * Creates a copy instance.
058     *
059     * @param source Source to copy.
060     */
061    protected XoRoShiRo128Plus(XoRoShiRo128Plus source) {
062        super(source);
063    }
064
065    /** {@inheritDoc} */
066    @Override
067    protected long nextOutput() {
068        return state0 + state1;
069    }
070
071    /** {@inheritDoc} */
072    @Override
073    protected XoRoShiRo128Plus copy() {
074        // This exists to ensure the jump function performed in the super class returns
075        // the correct class type. It should not be public.
076        return new XoRoShiRo128Plus(this);
077    }
078}