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 64-bit generator suitable for {@code double} generation. This is slightly faster than the
22 * all-purpose generator {@link XoRoShiRo128StarStar}.
23 *
24 * <p>This is a member of the Xor-Shift-Rotate family of generators. Memory footprint is 128 bits
25 * and the period is 2<sup>128</sup>-1. Speed is expected to be similar to
26 * {@link XoShiRo256Plus}.</p>
27 *
28 * @see <a href="http://xoshiro.di.unimi.it/xoroshiro128plus.c">Original source code</a>
29 * @see <a href="http://xoshiro.di.unimi.it/">xorshiro / xoroshiro generators</a>
30 * @since 1.3
31 */
32 public class XoRoShiRo128Plus extends AbstractXoRoShiRo128 {
33 /**
34 * Creates a new instance.
35 *
36 * @param seed Initial seed.
37 * If the length is larger than 2, only the first 2 elements will
38 * be used; if smaller, the remaining elements will be automatically
39 * set. A seed containing all zeros will create a non-functional generator.
40 */
41 public XoRoShiRo128Plus(long[] seed) {
42 super(seed);
43 }
44
45 /**
46 * Creates a new instance using a 2 element seed.
47 * A seed containing all zeros will create a non-functional generator.
48 *
49 * @param seed0 Initial seed element 0.
50 * @param seed1 Initial seed element 1.
51 */
52 public XoRoShiRo128Plus(long seed0, long seed1) {
53 super(seed0, seed1);
54 }
55
56 /**
57 * Creates a copy instance.
58 *
59 * @param source Source to copy.
60 */
61 protected XoRoShiRo128Plus(XoRoShiRo128Plus source) {
62 super(source);
63 }
64
65 /** {@inheritDoc} */
66 @Override
67 protected long nextOutput() {
68 return state0 + state1;
69 }
70
71 /** {@inheritDoc} */
72 @Override
73 protected XoRoShiRo128Plus copy() {
74 // This exists to ensure the jump function performed in the super class returns
75 // the correct class type. It should not be public.
76 return new XoRoShiRo128Plus(this);
77 }
78 }