    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    }