/Utilities/Math/RandomBase.cs

using System;

using System.Diagnostics;

using NUnit.Framework;



namespace Delta.Utilities.Math

{

	/// <summary>

	/// This class represents the base class for all random generator

	/// algorithms. Based on the article "Random isn't Really Random --

	/// C# Random Number Generation" by Matthew Cochran. @see:

	/// http://www.c-sharpcorner.com/UploadFile/rmcochran/random07172006175425PM/random.aspx

	/// </summary>

	public abstract class RandomBase : Random

	{

		#region Constructors

		/// <summary>

		/// Random base

		/// </summary>

		public RandomBase()

		{

		}



		/// <summary>

		/// Create random base

		/// </summary>

		public RandomBase(int seed)

			: base(seed)

		{

		}

		#endregion



		#region Next (Public)

		/// <summary>

		/// Returns a nonnegative random number.

		/// </summary>

		/// <returns>

		/// A 32-bit signed uinteger greater than or equal to zero and less than

		/// <see cref="F:System.uint32.MaxValue"></see>.

		/// </returns>

		public abstract override int Next();



		/// <summary>

		/// Returns a nonnegative random number less than the specified maximum.

		/// </summary>

		/// <param name="maxValue">

		/// The exclusive upper bound of the random number to be generated.

		/// maxValue must be greater than or equal to zero.

		/// </param>

		/// <returns>

		/// A 32-bit signed uinteger greater than or equal to zero, and less than

		/// maxValue; that is, the range of return values includes zero but not

		/// maxValue.

		/// </returns>

		/// <exception cref="T:System.ArgumentOutOfRangeException">

		/// maxValue is less than zero.

		/// </exception>

		public override int Next(int maxValue)

		{

			return Next(0, maxValue);

		}



		/// <summary>

		/// Returns a random number within a specified range.

		/// </summary>

		/// <param name="minValue">The inclusive lower bound of the random number

		/// returned.

		/// </param>

		/// <param name="maxValue">The exclusive upper bound of the random number

		/// returned. maxValue must be greater than or equal to minValue.

		/// </param>

		/// <returns>

		/// A 32-bit signed uinteger greater than or equal to minValue and less

		/// than maxValue; that is, the range of return values includes minValue

		/// but not maxValue. If minValue equals maxValue, minValue is returned.

		/// </returns>

		/// <exception cref="T:System.ArgumentOutOfRangeException">

		/// minValue is greater than maxValue.

		/// </exception>

		public override int Next(int minValue, int maxValue)

		{

			return Convert.ToInt32(((maxValue - 1) - minValue) * Sample() + minValue);

		}

		#endregion



		#region NextDouble (Public)

		/// <summary>

		/// Returns a random number between 0.0 and 1.0. If you just need a float

		/// value instead of a double, just convert it after calling this method.

		/// </summary>

		/// <returns>

		/// A double-precision floating pouint number greater than or equal to 0.0,

		/// and less than 1.0.

		/// </returns>

		public override double NextDouble()

		{

			return Sample();

		}

		#endregion



		#region NextBytes (Public)

		/// <summary>

		/// Fills the elements of a specified array of bytes with random numbers.

		/// </summary>

		/// <param name="buffer">An array of bytes to contain random numbers.</param>

		/// <exception cref="T:System.ArgumentNullException">buffer is null. </exception>

		public override void NextBytes(byte[] buffer)

		{

			int i, j, tmp;



			// fill the part of the buffer that can be covered by full Int32s

			for (i = 0; i < buffer.Length - 4; i += 4)

			{

				tmp = Next();



				buffer[i] = Convert.ToByte(tmp & 0x000000FF);

				buffer[i + 1] = Convert.ToByte((tmp & 0x0000FF00) >> 8);

				buffer[i + 2] = Convert.ToByte((tmp & 0x00FF0000) >> 16);

				buffer[i + 3] = Convert.ToByte((tmp & 0xFF000000) >> 24);

			}



			tmp = Next();



			// fill the rest of the buffer

			for (j = 0; j < buffer.Length % 4; j++)

			{

				buffer[i + j] =

					Convert.ToByte((tmp & (0x000000FF << (8 * j))) >> (8 * j));

			}

		}

		#endregion



		#region Methods (Private)



		#region GetBaseNextInt32

		/// <summary>

		/// Get base next int 32

		/// </summary>

		protected int GetBaseNextInt32()

		{

			return base.Next();

		}

		#endregion



		#region GetBaseNextUInt32

		/// <summary>

		/// Get base next u texture coordinate int 32

		/// </summary>

		protected uint GetBaseNextUInt32()

		{

			return ConvertToUInt32(base.Next());

		}

		#endregion



		#region GetBaseNextDouble

		/// <summary>

		/// Get base next double

		/// </summary>

		protected double GetBaseNextDouble()

		{

			return base.NextDouble();

		}

		#endregion



		#region Sample

		/// <summary>

		/// Returns a random number between 0.0 and 1.0.

		/// </summary>

		/// <returns>

		/// A double-precision floating pouint number greater than or equal to 0.0, and less than 1.0.

		/// </returns>

		protected override double Sample()

		{

			// generates a random number on [0,1) and divided by 2^31

			// (Int32 absolute value)

			return Convert.ToDouble(Next()) / 2147483648.0;

		}

		#endregion



		#region ConvertToUInt32

		/// <summary>

		/// Convert to u texture coordinate int 32

		/// </summary>

		/// <param name="value">Value</param>

		protected static UInt32 ConvertToUInt32(Int32 value)

		{

			return BitConverter.ToUInt32(BitConverter.GetBytes(value), 0);

		}

		#endregion



		#region ConvertToInt32

		/// <summary>

		/// Convert to int 32

		/// </summary>

		/// <param name="value">Value</param>

		protected static Int32 ConvertToInt32(UInt32 value)

		{

			return BitConverter.ToInt32(BitConverter.GetBytes(value), 0);

		}



		/// <summary>

		/// Convert to int 32

		/// </summary>

		/// <param name="value">Value</param>

		protected static Int32 ConvertToInt32(UInt64 value)

		{

			return BitConverter.ToInt32(

				BitConverter.GetBytes(value & 0x000000007fffffff), 0);

		}

		#endregion



		#endregion



		/// <summary>

		/// Tests for RandomBase implementations

		/// </summary>

		internal class RandomBaseTests

		{

			#region PerformGenerator (Static)

			/// <summary>

			/// Perform generator

			/// </summary>

			[Test]

			private static void PerformGenerator(Random generator,

				Stopwatch timeCounter)

			{

				timeCounter.Reset();

				timeCounter.Start();

				for (int index = 0; index < 10000000; index++)

				{

					generator.NextDouble();

				}

				timeCounter.Stop();



				Console.WriteLine(

					"The time for the '" + generator + "' generator took '" +

					timeCounter.ElapsedMilliseconds + "' ms.");



				Console.Write("Example values are: ");

				for (int index = 0; index < 10; index++)

				{

					Console.Write(generator.NextDouble().ToString("0.000000 | "));

				}

				Console.WriteLine();

			}

			#endregion



			#region TestPerformance (LongRunning)

			/// <summary>

			/// Test performance

			/// </summary>

			[Test, Category("LongRunning")]

			public static void TestPerformance()

			{

				Stopwatch timeCounter = new Stopwatch();



				PerformGenerator(new Random(), timeCounter);

				PerformGenerator(new Random250Algorithm(), timeCounter);

			}

			#endregion

		}

	}

}