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/// ------------------------------------------------------
/// RandomOps - (Pseudo) Random Number Generator For C#
/// Copyright (C) 2003-2010 Magnus Erik Hvass Pedersen.
/// Please see the file license.txt for license details.
/// RandomOps on the internet: http://www.Hvass-Labs.org/
/// ------------------------------------------------------
using System;
using System.Diagnostics;
namespace RandomOps
{
/// <summary>
/// Pseudo-Random Number Generator (PRNG) based on XorShift as
/// described in the paper: G. Marsaglia, Random Number Generators,
/// Journal of Modern Applied Statistical Methods, 2003, vol. 2, no. 1,
/// p. 2-13. Period of this PRNG is about 2^160. Not thread-safe.
/// </summary>
/// <remarks>
/// This is a translation of the C source-code published 2003-05-13
/// in the newsgroup comp.lang.c by George Marsaglia, published
/// here with Marsaglia's authorization under the license in license.txt
/// </remarks>
public class XorShift : RanUInt32Array
{
#region Constructors.
/// <summary>
/// Constructs the PRNG-object without a seed. Remember
/// to seed it before drawing random numbers.
/// </summary>
public XorShift()
: base()
{
}
/// <summary>
/// Constructs the PRNG-object using the designated seed.
/// This is useful if you want to repeat experiments with the
/// same sequence of pseudo-random numbers.
/// </summary>
public XorShift(UInt32[] seed)
: base(seed)
{
}
/// <summary>
/// Constructs the PRNG-object and uses another RNG for seeding.
/// </summary>
public XorShift(Random rand)
: base(rand)
{
}
#endregion
#region Public properties.
/// <summary>
/// Default seed.
/// </summary>
public static readonly UInt32[] SeedDefault = { 123456789, 362436069, 521288629, 88675123, 886756453 };
#endregion
#region Internal definitions and variables
/// <summary>
/// Iterator variables.
/// </summary>
UInt32 X, Y, Z, W, V;
/// <summary>
/// Is PRNG ready for use?
/// </summary>
bool IsReady = false;
#endregion
#region PRNG Implementation.
/// <summary>
/// Draw a random number in inclusive range {0, .., RandMax}
/// </summary>
public sealed override UInt32 Rand()
{
Debug.Assert(IsReady);
UInt32 t = (X ^ (X >> 7));
X=Y;
Y=Z;
Z=W;
W=V;
V = (V ^ (V << 6)) ^ (t ^ (t << 13));
UInt32 retVal = (Y+Y+1)*V;
return retVal;
}
/// <summary>
/// The maximum possible value returned by Rand().
/// </summary>
public sealed override UInt32 RandMax
{
get { return UInt32.MaxValue; }
}
/// <summary>
/// Length of seed-array.
/// </summary>
public sealed override int SeedLength
{
get { return 5; }
}
/// <summary>
/// Seed with an array.
/// </summary>
public sealed override void Seed(UInt32[] seed)
{
Debug.Assert(seed.Length == SeedLength);
X = seed[0];
Y = seed[1];
Z = seed[2];
W = seed[3];
V = seed[4];
IsReady = true;
}
#endregion
#region Base-class overrides.
/// <summary>
/// Name of the RNG.
/// </summary>
public override string Name
{
get { return "XorShift"; }
}
#endregion
}
}
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