Hi.
Here is a micro-benchmark report (performed with "PerfTestUtils"):
-----
nextInt() (calls per timed block: 2000000, timed blocks: 100, time
unit: ms)
name time/call std dev total time ratio cv
difference
o.a.c.m.r.JDKRandomGenerator 1.088e-05 2.8e-06 2.1761e+03 1.000 0.26
0.0000e+00
o.a.c.m.r.MersenneTwister 1.024e-05 1.5e-06 2.0471e+03 0.941 0.15
-1.2900e+02
o.a.c.m.r.Well512a 1.193e-05 4.4e-07 2.3864e+03 1.097 0.04
2.1032e+02
o.a.c.m.r.Well1024a 1.348e-05 1.9e-06 2.6955e+03 1.239 0.14
5.1945e+02
o.a.c.m.r.Well19937a 1.495e-05 2.1e-06 2.9906e+03 1.374 0.14
8.1451e+02
o.a.c.m.r.Well19937c 1.577e-05 8.8e-07 3.1542e+03 1.450 0.06
9.7816e+02
o.a.c.m.r.Well44497a 1.918e-05 1.4e-06 3.8363e+03 1.763 0.08
1.6602e+03
o.a.c.m.r.Well44497b 1.953e-05 2.8e-06 3.9062e+03 1.795 0.14
1.7301e+03
o.a.c.m.r.ISAACRandom 1.169e-05 1.9e-06 2.3375e+03 1.074 0.16
1.6139e+02
-----
where "cv" is the ratio of the 3rd to the 2nd column.
Questions are:
* How meaningful are micro-benchmarks when the timed operation has a
very
small duration (wrt e.g. the duration of other machine instructions
that
are required to perform them)?
* In a given environment (HW, OS, JVM), is there a lower limit
(absolute
duration) below which anything will be deemed good enough?
* Can a library like CM admit a trade-off between ultimate performance
and
good design?
IOW, is there an acceptable overhead in exchange for other qualities
(clarity, non-redundancy, extensibility, etc.)?
* Does ultimate performance for the base functionality (generation of a
random number) trump any consideration of use-cases that would need
an
extension (of the base functionality, such as computation to match
another
distribution) that will unavoidably degrades the performance (hence
the
micro-benchmark will be completely misleading for those users)?
* What are usages of the CM RNGs?
Do those use-cases strictly forbid "loosing" a dozen milliseconds per
million calls?
IOW, would those users for which such a difference matters use CM at
all?
Thanks,
Gilles
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