Timed out 3-2. Enacted by card.
Adminned at 18 May 2017 17:29:46 UTC
In the Appendix under “Random Generators” add the following text:
DICEN cannot be rolled in the GNDT if N is 22 or more digits long.
Seems urgent enough to be a CfJ
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Comments
Cuddlebeam:
Tried it out. As a single DICEN not apparently because the GNDT won’t let me, but it could be done via several dicerolls. For example a DICE(10^63) could be rolled as three DICE(10^21), with the first one corresponding to the first 21 digits, the second one for digits 22 to 43 and a third for 44 to 63.
Sphinx:
I don’t really see this as an issue.
Matt:
@Cuddlebeam, that may result in a non-uniform distribution, which would give bias to the randomness.
There ought to be some sane upper bound. Basing it on the limits of the system seems sound.
pokes:
We’d need to ask Kevin about the GNDT source but I suspect a DICE(10^21) isn’t the distribution we think it is. If DICE(X) is ceil(X * U) where U is floating point uniform from [0,1], U probably doesn’t have the 10^21 levels of precision we want.
pokes:
*Kevan. Sorry you got autocorrected, Kevan
card:
So would 20 digits or less have the precision we want? What digits do have a reasonable distribution?
pokes:
Yes: That some of the larger integer DICE most recently rolled are divisible by 4096 is likely not a concidence.
pokes:
That yes was in response to my own comment. No, 20 digits is too many still.
pokes:
I don’t think we can know for sure without Kevan’s knowledge. 9 digits are probably safe. Anything that gets to that point has gotta be just as game breaking as something at 21 digits.
Sphinx:
I’d naively assume that it’s a double, so the largest number where we still have single integer precision would be 2^53, or about 10^15.
Kevan:
The source code is just an int(rand($sides)+1) in perl.
Publius Scribonius Scholasticus:
We should have a more logical upper bound.
pokes:
Perl appears to have a 48-bit RNG, although any DICE close to 2^48 will still be notably non-uniform.
Cuddlebeam:
@Matt: ...How?
card:
[PSS] What’s more logical than the limitations of the GNDT? In the context of being able to see each individual digit of a die result at least.
Sphinx:
I think it’s fine