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     * [-&#x0221A;3, +&#x0221A;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    }