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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 XoShiRo256StarStar}.
23   *
24   * <p>This is a member of the Xor-Shift-Rotate family of generators. Memory footprint is 256 bits
25   * and the period is 2<sup>256</sup>-1.</p>
26   *
27   * @see <a href="http://xoshiro.di.unimi.it/xoshiro256plus.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 XoShiRo256Plus extends AbstractXoShiRo256 {
32      /**
33       * Creates a new instance.
34       *
35       * @param seed Initial seed.
36       * If the length is larger than 4, only the first 4 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 XoShiRo256Plus(long[] seed) {
41          super(seed);
42      }
43  
44      /**
45       * Creates a new instance using a 4 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       * @param seed2 Initial seed element 2.
51       * @param seed3 Initial seed element 3.
52       */
53      public XoShiRo256Plus(long seed0, long seed1, long seed2, long seed3) {
54          super(seed0, seed1, seed2, seed3);
55      }
56  
57      /**
58       * Creates a copy instance.
59       *
60       * @param source Source to copy.
61       */
62      protected XoShiRo256Plus(XoShiRo256Plus source) {
63          super(source);
64      }
65  
66      /** {@inheritDoc} */
67      @Override
68      protected long nextOutput() {
69          return state0 + state3;
70      }
71  
72      /** {@inheritDoc} */
73      @Override
74      protected XoShiRo256Plus copy() {
75          // This exists to ensure the jump function performed in the super class returns
76          // the correct class type. It should not be public.
77          return new XoShiRo256Plus(this);
78      }
79  }