001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 018 package org.apache.commons.math.random; 019 020 import org.apache.commons.math.util.FastMath; 021 022 /** 023 * This class implements a normalized uniform random generator. 024 * <p>Since it is a normalized random generator, it generates values 025 * from a uniform distribution with mean equal to 0 and standard 026 * deviation equal to 1. Generated values fall in the range 027 * [-√3, +√3].</p> 028 * 029 * @since 1.2 030 * 031 * @version $Revision: 990655 $ $Date: 2010-08-29 23:49:40 +0200 (dim. 29 ao??t 2010) $ 032 */ 033 034 public class UniformRandomGenerator implements NormalizedRandomGenerator { 035 036 /** Serializable version identifier. */ 037 private static final long serialVersionUID = 1569292426375546027L; 038 039 /** Square root of three. */ 040 private static final double SQRT3 = FastMath.sqrt(3.0); 041 042 /** Underlying generator. */ 043 private final RandomGenerator generator; 044 045 /** Create a new generator. 046 * @param generator underlying random generator to use 047 */ 048 public UniformRandomGenerator(RandomGenerator generator) { 049 this.generator = generator; 050 } 051 052 /** Generate a random scalar with null mean and unit standard deviation. 053 * <p>The number generated is uniformly distributed between -&sqrt;(3) 054 * and +&sqrt;(3).</p> 055 * @return a random scalar with null mean and unit standard deviation 056 */ 057 public double nextNormalizedDouble() { 058 return SQRT3 * (2 * generator.nextDouble() - 1.0); 059 } 060 061 }