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    /**
021     * This class implements a normalized uniform random generator.
022     * <p>Since it is a normalized random generator, it generates values
023     * from a uniform distribution with mean equal to 0 and standard
024     * deviation equal to 1. Generated values fall in the range
025     * [-&#x0221A;3, +&#x0221A;3].</p>
026     *
027     * @since 1.2
028     *
029     * @version $Revision: 811827 $ $Date: 2009-09-06 11:32:50 -0400 (Sun, 06 Sep 2009) $
030     */
031    
032    public class UniformRandomGenerator implements NormalizedRandomGenerator {
033    
034        /** Serializable version identifier. */
035        private static final long serialVersionUID = 1569292426375546027L;
036    
037        /** Square root of three. */
038        private static final double SQRT3 = Math.sqrt(3.0);
039    
040        /** Underlying generator. */
041        private final RandomGenerator generator;
042    
043        /** Create a new generator.
044         * @param generator underlying random generator to use
045         */
046        public UniformRandomGenerator(RandomGenerator generator) {
047            this.generator = generator;
048        }
049    
050        /** Generate a random scalar with null mean and unit standard deviation.
051         * <p>The number generated is uniformly distributed between -&sqrt;(3)
052         * and +&sqrt;(3).</p>
053         * @return a random scalar with null mean and unit standard deviation
054         */
055        public double nextNormalizedDouble() {
056            return SQRT3 * (2 * generator.nextDouble() - 1.0);
057        }
058    
059    }