WyRand64 (bit reversed) fails PractRand at 32TB

[vigna]

rng=WyRand64-rev, seed=0x7cb0345e
length= 32 terabytes (2^45 bytes), time= 2032274 seconds
  Test Name                         Raw       Processed     Evaluation
  [Low1/8]BCFN(0+0,13-0,T)          R= +12.9  p =  1.9e-6   mildly suspicious
  [Low8/32]Gap-16:B                 R=  +5.8  p =  6.6e-5   unusual
  [Low8/64]BCFN(0+9,13-0,T)         R= +12.3  p =  4.1e-6   unusual
  [Low8/64]BCFN(0+10,13-0,T)        R= +20.6  p =  1.5e-10  very suspicious
  [Low8/64]BCFN(0+11,13-0,T)        R= +14.7  p =  2.2e-7   mildly suspicious
  [Low8/64]Gap-16:A                 R= +10.7  p =  2.1e-7   very suspicious
  [Low8/64]Gap-16:B                 R= +16.2  p =  8.3e-14    FAIL
  ...and 2410 test result(s) without anomalies

This test examines the bits produced by Wyrand64 after reversing them. PractRand examines in more detail the lower bits, so testing after a bit reversal is essential to discover weaknesses in the upper bits. The options used were -tf 2 -te 1 -tlmaxonly -tlmax 128TB

The normal (without bit inversion) test starts to give problem at 32TB but still does not fail:

rng=WyRand64, seed=0xdc6a32fb
length= 32 terabytes (2^45 bytes), time= 2032770 seconds
  Test Name                         Raw       Processed     Evaluation
  [Low4/64]Gap-16:B                 R=  +5.7  p =  8.2e-5   unusual
  [Low8/64]DC6-9x1Bytes-1           R=  -6.8  p =1-6.7e-4   unusual
  ...and 2415 test result(s) without anomalies

I expect to to fail at 64TB. Will report later the output.

[wangyi-fudan]

do{
torture;
}while(!fail)
return fail;

Yes, the hero failed, but he is still my hero.

[vigna]

Frankly, if you think that running one of the most popular test suites for PRNG is "torture" you should revise your research methods. Running PractRand is one of the first thing I do with any generator.

[wangyi-fudan]

Thanks man! I updated the readme.