content: /*******************************************************************************
   * Copyright (c) 2010 Haifeng Li
   *   
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *  
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   *******************************************************************************/
  
  package smile.math;
  
  import smile.math.random.MersenneTwister;
  import smile.math.random.UniversalGenerator;
  
  /**
   * This is a high quality random number generator as a replacement of
   * the standard Random class of Java system.
   * 
   * @author Haifeng Li
   */
  public class Random {
  
      private UniversalGenerator real;
      private MersenneTwister twister;
  
      /**
       * Initialize with default random number generator engine.
       */
      public Random() {
          real = new UniversalGenerator();
          twister = new MersenneTwister();
      }
  
      /**
       * Initialize with given seed for default random number generator engine.
       */
      public Random(long seed) {
          real = new UniversalGenerator(seed);
          twister = new MersenneTwister(seed);
      }
  
      /**
       * Generator a random number uniformly distributed in [0, 1).
       * @return a pseudo random number
       */
      public double nextDouble() {
          return real.nextDouble();
      }
  
      /**
       * Generate n uniform random numbers in the range [0, 1)
       * @param d array of random numbers to be generated
       */
      public void nextDoubles(double[] d) {
          real.nextDoubles(d);
      }
  
      /**
       * Generate a uniform random number in the range [lo, hi)
       * @param lo lower limit of range
       * @param hi upper limit of range
       * @return a uniform random real in the range [lo, hi)
       */
      public double nextDouble(double lo, double hi) {
          return (lo + (hi - lo) * nextDouble());
      }
  
      /**
       * Generate n uniform random numbers in the range [lo, hi)
       * @param lo lower limit of range
       * @param hi upper limit of range
       * @param d array of random numbers to be generated
       */
      public void nextDoubles(double[] d, double lo, double hi) {
          real.nextDoubles(d);
  
          double l = hi - lo;        
          int n = d.length;
          for (int i = 0; i < n; i++) {
              d[i] = lo + l * d[i];
          }
      }
  
      /**
       * Initialize the random generator with a seed.
       */
      public void setSeed(long seed) {
          real.setSeed(seed);
          twister.setSeed(seed);
      }
  
      /**
       * Returns a random integer.
       */
      public int nextInt() {
          return twister.nextInt();
      }
      
      /**
       * Returns a random integer in [0, n).
       */
      public int nextInt(int n) {
          return twister.nextInt(n);
      }
  
      public long nextLong() {
          return twister.nextLong();
      }
  
      /**
       * Generates a permutation of 0, 1, 2, ..., n-1, which is useful for
       * sampling without replacement.
       */
      public int[] permutate(int n) {
          int[] x = new int[n];
          for (int i = 0; i < n; i++) {
              x[i] = i;
          }
  
          permutate(x);
  
          return x;
      }
  
      /**
       * Generates a permutation of given array.
       */
      public void permutate(int[] x) {
          for (int i = 0; i < x.length; i++) {
              int j = i + nextInt(x.length - i);
              Math.swap(x, i, j);
          }
      }
  
      /**
       * Generates a permutation of given array.
       */
      public void permutate(float[] x) {
          for (int i = 0; i < x.length; i++) {
              int j = i + nextInt(x.length - i);
              Math.swap(x, i, j);
          }
      }
  
      /**
       * Generates a permutation of given array.
       */
      public void permutate(double[] x) {
          for (int i = 0; i < x.length; i++) {
              int j = i + nextInt(x.length - i);
              Math.swap(x, i, j);
          }
      }
  
      /**
       * Generates a permutation of given array.
       */
      public void permutate(Object[] x) {
          for (int i = 0; i < x.length; i++) {
              int j = i + nextInt(x.length - i);
              Math.swap(x, i, j);
          }
      }
  }