原文:【原创】开源Math.NET基础数学类库使用(12)C#随机数扩展方法
本博客所有文章分类的总目录：http://www.cnblogs.com/asxinyu/p/4288836.html
开源Math.NET基础数学类库使用总目录：http://www.cnblogs.com/asxinyu/p/4329737.html
前言
真正意义上的随机数（或者随机事件）在某次产生过程中是按照实验过程中表现的分布概率随机产生的，其结果是不可预测的，是不可见的。而计算机中的随机函数是按照一定算法模拟产生的，其结果是确定的，是可见的。我们可以这样认为这个可预见的结果其出现的概率是100%。所以用计算机随机函数所产生的“随机数”并不随机，是伪随机数。伪随机数的作用在开发中的使用非常常见，因此.NET在System命名空间，提供了一个简单的Random随机数生成类型。但这个类型并不能满足所有的需求，本节开始就将陆续介绍Math.NET中有关随机数的扩展以及其他伪随机生成算法编写的随机数生成器。
今天要介绍的是基于System.Random的扩展方法。
如果本文显示有问题，请参考：http://www.cnblogs.com/asxinyu/p/4301544.html
1.Random的扩展方法类
Rondom扩展及随机数相关的类都在Math.NET的MathNet.Numerics.Random命名空间，今天要介绍的 RandomExtensions 类是 扩展Random的静态方法类，可以直接在System.Random的对象上使用，相关功能介绍：
1.可以直接返回填充0-1随机数据的数组，如NextDoubles方法；
2.可以返回一个无限长度的IEnumerable接口对象，一直迭代返回double类型的随机数，是NextDoubleSequence方法；
3.类似的还可以返回其他类型的随机数据数组，如NextBytes，NextInt32s等；
4.还可以单独返回Int32类型和Int64类型的随机数，其范围在该类型的所有值域上，如NextFullRangeInt32，NextFullRangeInt64；
5.还可以单独返回Int32类型和Int64类型的随机数，其范围是该类型所有值域上的非负数,如NextInt64;
2.RandomExtensions类的实现
作为静态类，使用非常简单，为了方便理解，我将注释进行了部分翻译，贴出该类的所有源码，大家可以参考参考：
/// <summary>这个类是对System.Random类的扩展，扩展方法可以生成更多类型的伪随机数，而不是仅仅是double和Int32类型</summary>
/// <remarks>这个扩展是线程安全的，并且只有在Math.NET提供的随机数发生器或者RandomSource的继承类中被调用</remarks>
public static class RandomExtensions
{
/// <summary>使用(0-1)范围内的均匀随机数填充1个数组</summary>
/// <param name="rnd">Random类型的随机数生成器</param>
/// <param name="values">要填充随机数的数组</param>
/// <remarks>这个扩展是线程安全的，并且只有在Math.NET提供的随机数发生器或者RandomSource的继承类中被调用</remarks>
public static void NextDoubles(this System.Random rnd, double[] values)
{
var rs = rnd as RandomSource;
if (rs != null)
{
rs.NextDoubles(values);
return;
} for (var i = ; i < values.Length; i++)
{
values[i] = rnd.NextDouble();
}
} /// <summary>返回一个(0-1)范围内的均匀随机数填充1个数组</summary>
/// <param name="rnd">Random类型的随机数生成器</param>
/// <param name="count">要返回的数组的长度</param> public static double[] NextDoubles(this System.Random rnd, int count)
{
var values = new double[count];
NextDoubles(rnd, values);
return values;
} /// <summary>返回1个无限的0-1均匀分布随机数序列</summary>
public static IEnumerable<double> NextDoubleSequence(this System.Random rnd)
{
var rs = rnd as RandomSource;
if (rs != null) return rs.NextDoubleSequence();
return NextDoubleSequenceEnumerable(rnd);
} static IEnumerable<double> NextDoubleSequenceEnumerable(System.Random rnd)
{
while (true)
{
yield return rnd.NextDouble();
}
} /// <summary>返回1个均匀分布的byte数组</summary>
/// <param name="rnd">Random类型的随机数生成器</param>
/// <param name="count">要返回的数组的长度</param>
public static byte[] NextBytes(this System.Random rnd, int count)
{
var values = new byte[count];
rnd.NextBytes(values);
return values;
} /// <summary>
/// Fills an array with uniform random numbers greater than or equal to 0.0 and less than 1.0.
/// </summary>
/// <param name="rnd">The random number generator.</param>
/// <param name="values">The array to fill with random values.</param>
/// <param name="minInclusive">Lower bound, inclusive.</param>
/// <param name="maxExclusive">Upper bound, exclusive.</param>
public static void NextInt32s(this System.Random rnd, int[] values, int minInclusive, int maxExclusive)
{
var rs = rnd as RandomSource;
if (rs != null)
{
rs.NextInt32s(values, minInclusive, maxExclusive);
return;
}
for (var i = ; i < values.Length; i++)
{
values[i] = rnd.Next(minInclusive, maxExclusive);
}
} /// <summary>
/// Returns an infinite sequence of uniform random numbers greater than or equal to 0.0 and less than 1.0.
/// </summary>
public static IEnumerable<int> NextInt32Sequence(this System.Random rnd, int minInclusive, int maxExclusive)
{
var rs = rnd as RandomSource;
if (rs != null)
{
return rs.NextInt32Sequence(minInclusive, maxExclusive);
}
return NextInt32SequenceEnumerable(rnd, minInclusive, maxExclusive);
} static IEnumerable<int> NextInt32SequenceEnumerable(System.Random rnd, int minInclusive, int maxExclusive)
{
while (true)
{
yield return rnd.Next(minInclusive, maxExclusive);
}
} /// <summary>返回Int64类型的非负随机数</summary>
/// <param name="rnd">Random类型的随机数生成器</param>
/// <returns>
/// A 64-bit signed integer greater than or equal to 0, and less than <see cref="Int64.MaxValue"/>; that is,
/// the range of return values includes 0 but not <see cref="Int64.MaxValue"/>.
/// </returns>
/// <seealso cref="NextFullRangeInt64"/>
public static long NextInt64(this System.Random rnd)
{
var buffer = new byte[sizeof (long)]; rnd.NextBytes(buffer);
var candidate = BitConverter.ToInt64(buffer, ); candidate &= long.MaxValue;
return (candidate == long.MaxValue) ? rnd.NextInt64() : candidate;
} /// <summary>
/// Returns a random number of the full Int32 range.
/// </summary>
/// <param name="rnd">The random number generator.</param>
/// <returns>
/// A 32-bit signed integer of the full range, including 0, negative numbers,
/// <see cref="Int32.MaxValue"/> and <see cref="Int32.MinValue"/>.
/// </returns>
/// <seealso cref="System.Random.Next()"/>
public static int NextFullRangeInt32(this System.Random rnd)
{
var buffer = new byte[sizeof (int)];
rnd.NextBytes(buffer);
return BitConverter.ToInt32(buffer, );
} /// <summary>
/// Returns a random number of the full Int64 range.
/// </summary>
/// <param name="rnd">The random number generator.</param>
/// <returns>
/// A 64-bit signed integer of the full range, including 0, negative numbers,
/// <see cref="Int64.MaxValue"/> and <see cref="Int64.MinValue"/>.
/// </returns>
/// <seealso cref="NextInt64"/>
public static long NextFullRangeInt64(this System.Random rnd)
{
var buffer = new byte[sizeof (long)];
rnd.NextBytes(buffer);
return BitConverter.ToInt64(buffer, );
} /// <summary>
/// Returns a nonnegative decimal floating point random number less than 1.0.
/// </summary>
/// <param name="rnd">The random number generator.</param>
/// <returns>
/// A decimal floating point number greater than or equal to 0.0, and less than 1.0; that is,
/// the range of return values includes 0.0 but not 1.0.
/// </returns>
public static decimal NextDecimal(this System.Random rnd)
{
decimal candidate; // 50.049 % chance that the number is below 1.0. Try until we have one.
// Guarantees that any decimal in the interval can
// indeed be reached, with uniform probability.
do
{
candidate = new decimal(
rnd.NextFullRangeInt32(),
rnd.NextFullRangeInt32(),
rnd.NextFullRangeInt32(),
false,
);
}
while (candidate >= 1.0m); return candidate;
}
}
其使用非常简单，这里就不再举例子。这种扩展大家也应该写过，后面几篇文章将介绍Math.NET中实现的其他算法的随机数发生器。请关注
3.资源
源码下载：http://www.cnblogs.com/asxinyu/p/4264638.html
如果本文显示有问题，请参考本文原文：http://www.cnblogs.com/asxinyu/p/4301544.html