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From "Alex Herbert (Jira)" <j...@apache.org>
Subject [jira] [Commented] (RNG-122) Change SeedFactory random source
Date Mon, 07 Oct 2019 13:14:00 GMT

    [ https://issues.apache.org/jira/browse/RNG-122?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16945880#comment-16945880
] 

Alex Herbert commented on RNG-122:
----------------------------------

bq. That's a good reason in itself. I assumed that it was done already; sorry for the noise.

No problem.

It was not very clear that I was testing the generator (or alternatives) that we use in the
SeedFactory. Not the same generator when created from variants of the SeedFactory (i.e. different
seeds).



> Change SeedFactory random source
> --------------------------------
>
>                 Key: RNG-122
>                 URL: https://issues.apache.org/jira/browse/RNG-122
>             Project: Commons RNG
>          Issue Type: Improvement
>          Components: simple
>    Affects Versions: 1.3
>            Reporter: Alex Herbert
>            Assignee: Alex Herbert
>            Priority: Trivial
>
> The SeedFactory uses {{XOR_SHIFT_1024_S}}. This has a systematic failure in BigCrush
using the lower 32-bit bit in reverse order:
> [Xorshift1024*, xorshift1024+, xorshift128+ and xoroshiro128+ fail statistical tests
for linearity|https://www.sciencedirect.com/science/article/pii/S0377042718306265?dgcid=author]
> I have tested {{XOR_SHIFT_1024_S}} and {{XOR_SHIFT_1024_S_PHI}} using 10 runs of BigCrush
and see the following results:
> {noformat}
> RNG                     Bit-reversed    TestU01 (BigCrush) 
> XOR_SHIFT_1024_S        true            1,2,1,1,1,1,2,2,1,1
> XOR_SHIFT_1024_S_PHI    true            1,1,1,1,2,1,1,1,1,1
> RandomSource,Bit-reversed,Test,Failures,Failed
> XOR_SHIFT_1024_S,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S,true,TestU01 (BigCrush),2,68  MatrixRank, L=1000, r=0|80  LinearComp,
r = 0
> XOR_SHIFT_1024_S,true,TestU01 (BigCrush),2,25  ClosePairs mNP2S, t = 16|80  LinearComp,
r = 0
> XOR_SHIFT_1024_S,true,TestU01 (BigCrush),2,74  RandomWalk1 M (L=50, r=0)|80  LinearComp,
r = 0
> XOR_SHIFT_1024_S_PHI,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S_PHI,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S_PHI,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S_PHI,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S_PHI,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S_PHI,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S_PHI,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S_PHI,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S_PHI,true,TestU01 (BigCrush),1,80  LinearComp, r = 0
> XOR_SHIFT_1024_S_PHI,true,TestU01 (BigCrush),2,80  LinearComp, r = 0|80  LinearComp,
r = 0
> {noformat}
> This shows a systematic failure of the {{LinearComp}} test as observed in the paper linked
above.
> Update the SeedFactory to use a different generator.



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