| 1 | package desmoj.core.dist; |
| 2 | |
| 3 | import java.util.Random; |
| 4 | |
| 5 | /** |
| 6 | * Linear congruential random generator for uniformly distributed pseudo random |
| 7 | * numbers configured such that a stream of [0,1] double values is produced. |
| 8 | * Implements the <code>desmoj.dist.UniformRandomGenerator</code> interface. All |
| 9 | * <code>Distributions</code> in this package use this random generator by |
| 10 | * default. The implementation is based on the Java API |
| 11 | * <code>java.util.Random</code> class' random generator. The Java API Random |
| 12 | * class uses a 48-bit seed as input to the linear congruential formula. (See |
| 13 | * Donald Knuth, The Art of Computer Programming, Volume 2, Section 3.2.1.) |
| 14 | * |
| 15 | * @see desmoj.core.dist.UniformRandomGenerator |
| 16 | * @see desmoj.core.dist.Distribution |
| 17 | * @see java.util.Random |
| 18 | * |
| 19 | * @version DESMO-J, Ver. 2.3.3 copyright (c) 2011 |
| 20 | * @author Tim Lechler |
| 21 | * |
| 22 | * Licensed under the Apache License, Version 2.0 (the "License"); you |
| 23 | * may not use this file except in compliance with the License. You may |
| 24 | * obtain a copy of the License at |
| 25 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 26 | * |
| 27 | * Unless required by applicable law or agreed to in writing, software |
| 28 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 29 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or |
| 30 | * implied. See the License for the specific language governing |
| 31 | * permissions and limitations under the License. |
| 32 | * |
| 33 | */ |
| 34 | public class LinearCongruentialRandomGenerator implements |
| 35 | desmoj.core.dist.UniformRandomGenerator { |
| 36 | |
| 37 | /** |
| 38 | * The random generator provided by the Java API class |
| 39 | * <code>java.util.Random</code> |
| 40 | */ |
| 41 | protected Random javaAPIRandomGenerator; // the random generator used |
| 42 | |
| 43 | /** |
| 44 | * Creates a DefaultrandomGenerator with seed 42. The value 42 has been |
| 45 | * taken by pure coincidence. It is not really related to Douglas Adams' |
| 46 | * "Hitchhikers Guide to the Galaxy" trilogy of five books (so far). |
| 47 | */ |
| 48 | public LinearCongruentialRandomGenerator() { |
| 49 | |
| 50 | javaAPIRandomGenerator = new Random(42); |
| 51 | |
| 52 | } |
| 53 | |
| 54 | /** |
| 55 | * Creates a DefaultrandomGenerator with given value as initial seed. |
| 56 | * |
| 57 | * @param seed |
| 58 | * long : The initial seed of the underlying pseudo random |
| 59 | * generator |
| 60 | */ |
| 61 | public LinearCongruentialRandomGenerator(long seed) { |
| 62 | javaAPIRandomGenerator = new Random(seed); |
| 63 | } |
| 64 | |
| 65 | /** |
| 66 | * Returns the next pseudo random uniform [0,1] distributed double value |
| 67 | * from the stream produced by the underlying pseudo random number |
| 68 | * generator. |
| 69 | * |
| 70 | * @return double : The next pseudo random uniform [0,1] distributed double |
| 71 | * value |
| 72 | */ |
| 73 | public double nextDouble() { |
| 74 | |
| 75 | return javaAPIRandomGenerator.nextDouble(); |
| 76 | |
| 77 | } |
| 78 | |
| 79 | /** |
| 80 | * Sets the seed for the pseudo random number generator. |
| 81 | * |
| 82 | * @param newSeed |
| 83 | * long : The new initial seed value for the pseudo random number |
| 84 | * generator |
| 85 | */ |
| 86 | public void setSeed(long newSeed) { |
| 87 | |
| 88 | javaAPIRandomGenerator.setSeed(newSeed); |
| 89 | |
| 90 | } |
| 91 | } |