正如Chris Shain 的精彩回答所阐明的那样:您不能依赖于不同平台甚至 .NET 的主要版本上的结果相同
我们在@BlueLineGames遇到了这个确切的问题,因为我们使用 MonoGame 编写了一个游戏,该游戏在 Windows 的 .NET 中运行,但是当它在 OSX 的 Mono 上运行时产生了不同的值。
正如史蒂夫建议的那样,编写自己的 PRNG 是一个很好的解决方案。希望它可以为其他人节省一些时间,这里有一个可以代替 System.Random 的类和一些快速使用信息。
/// <summary>
/// This class is a drop-in replacement to use instead of Random(). Its
/// main purpose is to work identically across multiple platforms for a given
/// seed value - whereas the Random class is not guaranteed to give the
/// same results on different platforms even when the seed is the same.
///
/// This is an implementation of a Linear Congruential Generator which is
/// a very simple pseudorandom number generator. It is used instead of Random()
/// since Random() is implemented differently in Mono than .NET (and even
/// between different major-versions of .NET).
///
/// This is NOT recommended to be used for anything that should be secure such
/// as generating passwords or secret tokens. A "cryptogrpahically secure pseudorandom
/// number generator" (such as Mersenne Twister) should be used for that, instead.
///
/// More about Linear Congruential Generators can be found here:
/// http://en.wikipedia.org/wiki/Linear_congruential_generator
/// </summary>
public class CrossPlatformRandom : Random
{
// To start with, we'll be using the same values as Borland Delphi, Visual Pascal, etc.
// http://en.wikipedia.org/wiki/Linear_congruential_generator#Parameters_in_common_use
private const int LCG_MULTIPLIER = 134775813; // 0x08088405
private const int LCG_INCREMENT = 1;
private int _seed;
/// <summary>
/// Initializes a new instance of the CrossPlatformRandom class, using a time-dependent
/// default seed value.
///
/// Please note that this values generated from this are NOT guaranteed to be the same
/// cross-platform because there is no seed value. In cases where the caller requires
/// predictable or repeatable results, they MUST specify the seed.
/// </summary>
public CrossPlatformRandom()
{
// System.Random is time-dependent, so we will just use its first number to generate
// the seed.
Random rand = new Random();
this._seed = rand.Next();
}
/// <summary>
/// Initializes a new instance of the System.Random class, using the specified seed value.
/// </summary>
/// <param name="seed">A number used to calculate a starting value for the pseudo-random number sequence. If a negative number is specified, the absolute value of the number is used.</param>
public CrossPlatformRandom(int seed)
{
_seed = seed;
}
private int GetNext() // note: returns negative numbers too
{
_seed = (_seed * LCG_MULTIPLIER) + LCG_INCREMENT;
return _seed;
}
/// <summary>
// Returns a nonnegative random number.
/// </summary>
/// <returns>A 32-bit signed integer greater than or equal to zero and less than System.Int32.MaxValue.</returns>
public override int Next()
{
return this.Next(int.MaxValue);
}
/// <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 integer greater than or equal to zero, and less than maxValue; that is, the range of return values ordinarily includes zero but not maxValue. However, if maxValue equals zero, maxValue is returned.</returns>
/// <exception cref="System.ArgumentOutOfRangeException">maxValue is less than zero.</exception>
public override int Next(int maxValue)
{
if (maxValue < 0)
{
throw new System.ArgumentOutOfRangeException("maxValue is less than zero.");
}
ulong result = (ulong)(uint)GetNext() * (ulong)(uint)maxValue;
return (int)(result >> 32);
}
/// <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 integer 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="System.ArgumentOutOfRangeException">minValue is greater than maxValue.</exception>
public override int Next(int minValue, int maxValue)
{
if (minValue > maxValue)
{
throw new System.ArgumentOutOfRangeException("minValue is greater than maxValue.");
}
return minValue + this.Next(maxValue - minValue);
}
/// <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="System.ArgumentNullException">buffer is null.</exception>
public override void NextBytes(byte[] buffer)
{
if (buffer == null)
{
throw new System.ArgumentNullException("buffer is null.");
}
for (int index = 0; index < buffer.Length; index++)
{
buffer[index] = (byte)this.Next((int)byte.MaxValue);
}
}
/// <summary>
/// Returns a random number between 0.0 and 1.0.
/// </summary>
/// <returns>A double-precision floating point number greater than or equal to 0.0, and less than 1.0.</returns>
public override double NextDouble()
{
return this.Sample();
}
/// <summary>
/// Returns a random number between 0.0 and 1.0.
///
/// Since System.Random no longer uses this as the basis for all of the other random methods,
/// this method isn't used widely by this class. It's here for completeness, primarily in case Random
/// adds new entry points and we are lucky enough that they base them on .Sample() or one of the other existing methods.
/// </summary>
/// <returns>A double-precision floating point number greater than or equal to 0.0, and less than 1.0.</returns>
protected override double Sample()
{
return ((double)this.Next() / (double)int.MaxValue);
}
}
您应该能够安全地删除此类,而不是使用任何 Random(),但您实际上只需要在使用种子构造它的地方执行此操作(例如:new Random(seedValue))。
一些示例用法:
int seed = 42;
CrossPlatformRandom r = new CrossPlatformRandom(seed);
for (int i = 0; i < 10; ++i)
Console.WriteLine(r.Next(100));