[RNG-122] Change SeedFactory random source

• Type: Improvement
• Status: Closed
• Priority: Trivial
• Resolution: Implemented
• Affects Version/s: 1.3
• Fix Version/s: 1.3
• Component/s: simple
• Assignee: Alex Herbert
• Reporter: Alex Herbert
• Created: 07/Oct/19 11:22
• Updated: 11/Nov/19 14:25
• Resolved: 07/Oct/19 14:22

Description

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

I have tested XOR_SHIFT_1024_S and XOR_SHIFT_1024_S_PHI using 10 runs of BigCrush and see the following results:

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

This shows a systematic failure of the LinearComp test as observed in the paper linked above.

Update the SeedFactory to use a different generator.