A predictable random number generator. : Random « Development Class « Java

1. Java
2. Development Class
3. Random

A predictable random number generator.

  
/*
 * Encog(tm) Core v3.0 - Java Version
 * http://www.heatonresearch.com/encog/
 * http://code.google.com/p/encog-java/
 
 * Copyright 2008-2011 Heaton Research, Inc.
 *
 * 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.
 *   
 * For more information on Heaton Research copyrights, licenses 
 * and trademarks visit:
 * http://www.heatonresearch.com/copyright
 */

/**
 * A predictable random number generator. This is useful for unit tests and
 * benchmarks where we want random numbers, but we want them to be the same each
 * time. This class exists on both Java and C# so it can even provide consistent
 * random numbers over the two platforms.
 * 
 * Random numbers are created using a LCG.
 * 
 * http://en.wikipedia.org/wiki/Linear_congruential_generator
 */
public class LinearCongruentialGenerator {

  /**
   * First part of default mod.
   */
  public static final long DEFAULT_MOD1 = 2L;
  
  /**
   * Second part of default mod.
   */
  public static final long DEFAULT_MOD2 = 32L;
  
  /**
   * Default mult.
   */
  public static final long DEFAULT_MULT = 1103515245L;
  
  /**
   * Default inc.
   */
  public static final long DEFAULT_INC = 12345L;
  
  /**
   * The modulus.
   */
  private final long modulus;

  /**
   * The multiplier.
   */
  private final long multiplier;

  /**
   * The amount to increment.
   */
  private final long increment;

  /**
   * The current seed, set to an initial value and always holds the value of
   * the last random number generated.
   */
  private long seed;

  /**
   * The maximum rand number that the standard GCC based LCG will generate.
   */
  public static final long MAX_RAND = 4294967295L;

  /**
   * Construct the default LCG. You need only specify a seed.
   * 
   * @param theSeed
   *            The seed to use.
   */
  public LinearCongruentialGenerator(final long theSeed) {
    this((long) Math.pow(DEFAULT_MOD1, DEFAULT_MOD2), 
        DEFAULT_MULT, DEFAULT_INC, theSeed);
  }

  /**
   * Create a LCG with the specified modulus, multiplier and increment. Unless
   * you REALLY KNOW WHAT YOU ARE DOING, just use the constructor that just
   * takes a seed. It will set these values to the same as set by the GCC C
   * compiler. Setting these values wrong can create fairly useless random
   * numbers.
   * 
   * @param theModulus
   *            The modulus for the LCG algorithm.
   * @param theMultiplier
   *            The multiplier for the LCG algorithm.
   * @param theIncrement
   *            The increment for the LCG algorithm.
   * @param theSeed
   *            The seed for the LCG algorithm. Using the same seed will give
   *            the same random number sequence each time, whether in Java or
   *            DotNet.
   */
  public LinearCongruentialGenerator(final long theModulus,
      final long theMultiplier, final long theIncrement, 
      final long theSeed) {
    super();
    this.modulus = theModulus;
    this.multiplier = theMultiplier;
    this.increment = theIncrement;
    this.seed = theSeed;
  }

  /**
   * @return The LCG increment.
   */
  public final long getIncrement() {
    return this.increment;
  }

  /**
   * @return The LCG modulus.
   */
  public final long getModulus() {
    return this.modulus;
  }

  /**
   * @return The LCG multiplier.
   */
  public final long getMultiplier() {
    return this.multiplier;
  }

  /**
   * @return The current seed. Set to a constant to start, thereafter the
   *         previously generated random number.
   */
  public final long getSeed() {
    return this.seed;
  }

  /**
   * @return The next random number as a double between 0 and 1.
   */
  public final double nextDouble() {
    return (double) nextLong() / LinearCongruentialGenerator.MAX_RAND;
  }

  /**
   * @return The next random number as a long between 0 and MAX_RAND.
   */
  public final long nextLong() {
    this.seed = (this.multiplier * this.seed + this.increment)
        % this.modulus;
    return this.seed;
  }

  /**
   * Generate a random number in the specified range.
   * 
   * @param min
   *            The minimum random number.
   * @param max
   *            The maximum random number.
   * @return The generated random number.
   */
  public final double range(final double min, final double max) {
    final double range = max - min;
    return (range * nextDouble()) - min;
  }

  /**
   * Set the seed value. Setting a seed to a specific value will always result
   * in the same sequence of numbers, whether on Java or DotNet.
   * 
   * @param theSeed
   *            The seed value.
   */
  public final void setSeed(final long theSeed) {
    this.seed = theSeed;
  }

}

   
    
  

Related examples in the same category