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 }