C# Advanced RNG Example

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using System;

using CenterSpace.NMath.Core;

namespace CenterSpace.NMath.Core.Examples.CSharp
{
  /// <summary>
  /// A .NET example in C# showing how to create a random number generator for a 
  /// particular probability distribution using a specified uniform deviate
  /// method. Also shown is how to access and modify the uniform deviate
  /// generating object from the NMath Core random number generator object.
  /// </summary>
  class AdvancedRNGExample
  {

    static void Main( string[] args )
    {
      Console.WriteLine();

      // Create a RandomNumberGenerator.UniformRandomNumber delegate object
      // from the method System.Random.NextDouble().
      var sysRand = new Random();
      var uniformDeviates = new RandomNumberGenerator.UniformRandomNumber( sysRand.NextDouble );

      // Now, construct a binomial random number generator using this delegate to
      // generate uniformly distributed random deviates between 0 and 1 (the 
      // binomial generator will transform these uniform deviates into binomial
      // deviates).
      int trials = 2000;
      double prob = 0.002;
      var binRand = new RandGenBinomial( trials, prob, uniformDeviates );

      // Create a vector of binomial deviates and use it to create a histogram.
      int n = 200;
      var randomVec = new DoubleVector( n, binRand );

      // Create histogram
      int numBins = 20;
      var h = new Histogram( numBins, randomVec );
      Console.WriteLine( h.StemLeaf() );

      // Change the uniform deviate generator to use the method NextDouble() form
      // NMath Cores RandGenMTwist class.
      int seed = 0x124;

      // Construct the MT generator with the given seed.
      var mt = new RandGenMTwist( seed );

      // Create the delegate.
      uniformDeviates = new RandomNumberGenerator.UniformRandomNumber( mt.NextDouble );

      // Use the delegate to generate the uniform deviates necessary to for the 
      // binomial generator.
      binRand.UniformDeviateMethod = uniformDeviates;

      // Generate a vector of binomial deviates.
      var randomSequence1 = new DoubleVector( n, binRand );

      // All NMathCore random number generator classes have Reset() and Reset(int) 
      // methods that attempt to reset the underlying uniform generator with the
      // time of day, for the no argument reset, or the given seed, for the integer
      // argument version. These methods return true if the reset was successful and
      // false if it was not. The reset methods will succeed if the following 
      // conditions are met:
      // 1. The uniform generator delegate is an instance method, i.e. the Target 
      //    property of the Delegate class returns a non-null reference.
      // 2. The object reference thus obtained has a method named Initialize that
      //    returns void and takes no arguments, for the Reset() method, or a 
      //    single integer argument for the Reset(int) method.
      // The RandGenMTwist class has an Initialize(int) method, so the Reset(int)
      // method should succeed.
      if ( binRand.Reset( seed ) )
      {
        // Random sequences started using the same seed, so they should be identical.
        var randomSequence2 = new DoubleVector( n, binRand );
        Console.WriteLine( "randomSequence1 == randomSequence2 is {0}", randomSequence1 == randomSequence2 );
      }
      else
      {
        Console.WriteLine( "Could not reset generator" );
      }

      Console.WriteLine();
      Console.WriteLine( "Press Enter Key" );
      Console.Read();
    }
  }
}

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