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.math3.random;
019    
020    import org.apache.commons.math3.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     * [-&#x0221A;3, +&#x0221A;3].</p>
028     *
029     * @since 1.2
030     *
031     * @version $Id: UniformRandomGenerator.java 1416643 2012-12-03 19:37:14Z tn $
032     */
033    
034    public class UniformRandomGenerator implements NormalizedRandomGenerator {
035    
036        /** Square root of three. */
037        private static final double SQRT3 = FastMath.sqrt(3.0);
038    
039        /** Underlying generator. */
040        private final RandomGenerator generator;
041    
042        /** Create a new generator.
043         * @param generator underlying random generator to use
044         */
045        public UniformRandomGenerator(RandomGenerator generator) {
046            this.generator = generator;
047        }
048    
049        /** Generate a random scalar with null mean and unit standard deviation.
050         * <p>The number generated is uniformly distributed between -&sqrt;(3)
051         * and +&sqrt;(3).</p>
052         * @return a random scalar with null mean and unit standard deviation
053         */
054        public double nextNormalizedDouble() {
055            return SQRT3 * (2 * generator.nextDouble() - 1.0);
056        }
057    
058    }