On Thursday, 27 February 2020 at 15:29:02 UTC, Bruce Carneal
wrote:
big snip
TL;DR for the snipped: Unsurprisingly, different inputs will lead
to different timing results. The equi-probable values supplied
by a standard PRNG differ significantly from an equi-probable
digit input. In particular, the PRNG input is much more
predictable.
Note also that a uint PRNG will produce numbers that need 10
decimal digits. If my arithmetic is correct, you'll see "9 or
better" out of a uint PRNG 97.79% of the time. The
predictability of the full set of inputs is, secondarily but
importantly, also influenced by the ability of the branch
predictor to ferret out combinations.
I lack confidence in my ability to reason from first principles
when presented with a modern CPU branch predictor and a complex
input. Much easier for me to just run tests against various
distributions that I think span the input and reason from the
results.
