in reply to is rand random enough to simulate dice rolls?

While the above seems to be ok on my platform, can I expect the same result on every platform? and for every perl version around the world?

At least old perls for Windows had a very limited PRNG, with an interval of only 2^14 (?). I've no idea how evenly distributed its output is/was. So, the quality of rand() differs from platform to platform and may also change with the perl version.

Should I repeat the check 100 times to have an average of averages?

Averaging averages won't help. After all, you just sum up n*m numbers and divide by n*m - either in n steps or all at once. Using the median of n averages might help.

Update:

See also Random numbers are not random enough on Windows and https://www.effectiveperlprogramming.com/2014/06/perl-5-20-uses-its-own-random-number-generator/.

Alexander

--
Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)
  • Comment on Re: is rand random enough to simulate dice rolls?

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Re^2: is rand random enough to simulate dice rolls?
by LanX (Saint) on Jan 03, 2021 at 16:33 UTC
    > At least old perls for Windows had a very limited PRNG, with an interval of only 2^14 (?).

    Having an interval of 2**14 ~= 16_000 means the sequence repeats.

    > I've no idea how evenly distributed its output is/was.

    By definition it must hit the average 3.5 exactly after 2**14 runs.°

    IMHO 10000 runs for a margin of ± 0.2 is a safe bet. ²

    If this test fails, something must be done.

    Cheers Rolf
    (addicted to the Perl Programming Language :)
    Wikisyntax for the Monastery

    °) modulo rounding errors with Perl floats

    ²) that's more than 3% of the interval!

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