种子会在不同的Ruby中生成相同的随机序列吗? [英] Does seed generate same random sequence across different Rubys?
问题描述
假设我呼叫 srand(1234)，然后反复呼叫 rand().无论我的环境如何，我都可以保证获得相同的随机数序列吗?
Suppose I call srand(1234), then call rand() repeatedly. Am I guaranteed to get the same sequence of random numbers regardless of my environment?
例如
- Ruby 1.8.7 vs 1.9.3 vs 2.0
- MRI与JRuby
- Windows vs Mac vs Linux
推荐答案
根据我的经验，答案是是"
The answer in my experience is "yes"
在测试新宝石时，我也做同样的事情.gem尚不适合在现实世界中使用，但在很大程度上依赖于随机数，并且大多数测试都涉及事先运行Ruby的srand()，因此我得到了可预测的数字断言.总而言之，每次运行测试套件时，我可能都会测试由rand()生成的几百个小整数.
I do this exact same thing when testing a new gem. The gem is not ready for real-world use, but relies heavily on random numbers, and most of the tests involve running Ruby's srand() beforehand so I get predictable numbers for assertions. All in all I probably test a few hundred small integers generated by rand() every time I run the test suite.
到目前为止，我已经测试过:
So far I have tested:
在Windows上:MRI 1.9.3
On Windows: MRI 1.9.3
在Mac上:MRI 1.8.7，MRI 1.9.3和MRI 2.0.0
On Mac: MRI 1.8.7, MRI 1.9.3 and MRI 2.0.0
在Travis上(请参阅内部版本 https://travis-ci.org/neilslater/games_dice )，我将对所有这些内容进行测试:
On Travis (see build https://travis-ci.org/neilslater/games_dice), I test all these:
- "1.8.7"
- "1.9.3"
- "2.0.0"
- jruby-18mode#JRuby处于1.8模式
- jruby-19mode#1.9模式下的JRuby
- rbx-18mode
- rbx-19mode
最后两个我什至都不知道它们是什么:-)
The last two of which I don't even know what they are :-)
由于Ruby的 rand 方法中的数字意外，测试套件从未失败.
The test suite has never failed due to an unexpected number from Ruby's rand method.
Ruby中的底层机制称为Mersenne Twister http://en.wikipedia.org/wiki/Mersenne_twister ，这将从相同的种子生成相同的值，即使是在实施该语言的不同语言中也是如此.据我所知，该算法是Ruby的 rand()(和 srand())在所有标准实现中使用的算法.
The underlying mechanism in Ruby is called the Mersenne Twister http://en.wikipedia.org/wiki/Mersenne_twister and this will generate same values from the same seeds, even across different languages, where it has been implemented. As far as I know, this algorithm is the one used by Ruby's rand() (and srand()) in all the standard implementations.
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