Raymond | dee0849 | 2015-04-02 10:43:13 -0700 | [diff] [blame] | 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.math.random; |
| 19 | |
| 20 | import org.apache.commons.math.util.FastMath; |
| 21 | |
| 22 | /** |
| 23 | * This class implements a normalized uniform random generator. |
| 24 | * <p>Since it is a normalized random generator, it generates values |
| 25 | * from a uniform distribution with mean equal to 0 and standard |
| 26 | * deviation equal to 1. Generated values fall in the range |
| 27 | * [-√3, +√3].</p> |
| 28 | * |
| 29 | * @since 1.2 |
| 30 | * |
| 31 | * @version $Revision: 990655 $ $Date: 2010-08-29 23:49:40 +0200 (dim. 29 août 2010) $ |
| 32 | */ |
| 33 | |
| 34 | public class UniformRandomGenerator implements NormalizedRandomGenerator { |
| 35 | |
| 36 | /** Serializable version identifier. */ |
| 37 | private static final long serialVersionUID = 1569292426375546027L; |
| 38 | |
| 39 | /** Square root of three. */ |
| 40 | private static final double SQRT3 = FastMath.sqrt(3.0); |
| 41 | |
| 42 | /** Underlying generator. */ |
| 43 | private final RandomGenerator generator; |
| 44 | |
| 45 | /** Create a new generator. |
| 46 | * @param generator underlying random generator to use |
| 47 | */ |
| 48 | public UniformRandomGenerator(RandomGenerator generator) { |
| 49 | this.generator = generator; |
| 50 | } |
| 51 | |
| 52 | /** Generate a random scalar with null mean and unit standard deviation. |
| 53 | * <p>The number generated is uniformly distributed between -&sqrt;(3) |
| 54 | * and +&sqrt;(3).</p> |
| 55 | * @return a random scalar with null mean and unit standard deviation |
| 56 | */ |
| 57 | public double nextNormalizedDouble() { |
| 58 | return SQRT3 * (2 * generator.nextDouble() - 1.0); |
| 59 | } |
| 60 | |
| 61 | } |