1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.rng.core.source64;
19
20 /**
21 * A fast all-purpose 64-bit generator.
22 *
23 * <p>This is a member of the Xor-Shift-Rotate family of generators. Memory footprint is 128 bits
24 * and the period is 2<sup>128</sup>-1. Speed is expected to be similar to
25 * {@link XoShiRo256StarStar}.</p>
26 *
27 * @see <a href="http://xoshiro.di.unimi.it/xoroshiro128starstar.c">Original source code</a>
28 * @see <a href="http://xoshiro.di.unimi.it/">xorshiro / xoroshiro generators</a>
29 * @since 1.3
30 */
31 public class XoRoShiRo128StarStar extends AbstractXoRoShiRo128 {
32 /**
33 * Creates a new instance.
34 *
35 * @param seed Initial seed.
36 * If the length is larger than 2, only the first 2 elements will
37 * be used; if smaller, the remaining elements will be automatically
38 * set. A seed containing all zeros will create a non-functional generator.
39 */
40 public XoRoShiRo128StarStar(long[] seed) {
41 super(seed);
42 }
43
44 /**
45 * Creates a new instance using a 2 element seed.
46 * A seed containing all zeros will create a non-functional generator.
47 *
48 * @param seed0 Initial seed element 0.
49 * @param seed1 Initial seed element 1.
50 */
51 public XoRoShiRo128StarStar(long seed0, long seed1) {
52 super(seed0, seed1);
53 }
54
55 /**
56 * Creates a copy instance.
57 *
58 * @param source Source to copy.
59 */
60 protected XoRoShiRo128StarStar(XoRoShiRo128StarStar source) {
61 super(source);
62 }
63
64 /** {@inheritDoc} */
65 @Override
66 protected long nextOutput() {
67 return Long.rotateLeft(state0 * 5, 7) * 9;
68 }
69
70 /** {@inheritDoc} */
71 @Override
72 protected XoRoShiRo128StarStar copy() {
73 // This exists to ensure the jump function performed in the super class returns
74 // the correct class type. It should not be public.
75 return new XoRoShiRo128StarStar(this);
76 }
77 }