On Saturday, August 27, 2016 at 7:13:28 AM UTC+2, Christopher Howard wrote:

I know that, ff you feed mkStdGen a particular seed, and pull a list of
random numbers from that StdGen, that that the list will always be the
same if your run your compiled program over and over again on that same
system. But which of the following will cause you to get different output?:

2) Changes in "random" library version

Here's my semi-informed two cents:

In principle yes if they change random-generation algorithm.

1) Changes in GHC version

3) Compiling / Running on a different host computer (but compiling with
the same GHC & random versions.

 

IIUC no: the actual random number generator is not only a fully deterministic algorithm, but is written using simple integer arithmetic (not even bitwise operations) which should always have the same semantics (my only doubt is about the size of `Int`).
OTOH generating random floating-point numbers does more hackery which would require a closer inspection.

Reference: stdNext and stdSplit in http://hackage.haskell.org/package/random-1.1/docs/src/System-Random.html#StdGen

For further details and better reassurances, you might have better luck asking the authors (on GitHub). Maybe this could be documented?

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