On Wednesday, 23 November 2016 at 05:26:12 UTC, Ilya Yaroshenko
wrote:
Mir Random is going to be a library with saturated uniform FP
RNGs and almost saturated exponential FP RNGs. Comparing with
all other libraries (any language) the basic uniform FP numbers
will be generated in interval (-1, +1) and contains _all_
possible values including all subnormal numbers. 64 bit
generators are 2 times faster for this task if you need to
generate a 64 bit floating point number. Explanation of
technique will be in my post/article. --Ilya
All of which is fine in its own terms, but why prioritize the
speed of the default behaviour over its reliability and
reproducibility?
Anyone who cares about that combination of speed and statistical
quality will have enough information in the documentation to know
what to do. By contrast producing different results for
identical user code depending on whether you're making a 32- or
64-bit build is an unpleasant complication it could be better to
avoid.
In any case, given what you say above, shouldn't the choice of
32- vs. 64-bit RNG depend on whether one is using a distribution
that generates 32- vs. 64-bit floating-point variates, rather
than whether one is building for a 32- or 64-bit target? In
which case it needs to be a user choice, since it's only the user
who knows what distribution they're using.
