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From Gilles Sadowski <>
Subject Re: [Rng] New XoShiRo generators
Date Mon, 18 Mar 2019 14:12:55 GMT

>>> [...]
> >>
> >> One actual issue is that we are testing long providers using the long to create
2 int values. Should we test using a series of the upper 32 bits and then a series of the
lower 32 bits?
> >
> > Is that useful since the test now sees the integers as they are produced (i.e. 2
> > values per long)?
> >
> It is not relevant if you are concerned about int quality. But if you are concerned about
long quality then it is relevant. The long quality is important for the quality of nextDouble().
Although in that case only the upper 53 bits of the long. This means that the quality of a
long from an int provider is also not covered by the benchmark as that would require testing
alternating ints twice using the series: 1, 3, 5…, 2n+1 and 2, 4, 6, … 2n.

I don't follow: I'd think that if the full sequence passes the test,
then "decimated"
sequences will too.

> Given that half of the int values were previously discarded from the BigCrush analysis,
the current results on the user guide page actually represent BigCrush running on the upper
32-bits of the long, byte reversed due to the big/little endian interpretation of the bytes
in Java and linux.
> So maybe the an update to the RandomStressTester to support analysis for int or long
quality is needed.

I'm not convinced.

> For now the quality section on the website should just state that the quality is for
the ‘nextInt()’ method of the RNG.
> I have the results of BigCrush using the new bridge c program:
> XorShiftSerialComposite : 40, 39, 39 : 608.2 +/- 3.9

Makes sense now. :-}

> So it fails.
> The XorShiftXorComposite crashed after 2 hours about 1/4 of the results file complete.
I am running again so I can monitor it for memory usage. Something in the BigCrush suite just
cannot handle this generator output.



>>> [...]

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