Path: csiph.com!eternal-september.org!feeder.eternal-september.org!nntp.eternal-september.org!.POSTED!not-for-mail From: Tim Rentsch Newsgroups: comp.lang.c Subject: Re: Article of Melissa O'Nail Date: Thu, 08 Jan 2026 09:40:21 -0800 Organization: A noiseless patient Spider Lines: 31 Message-ID: <868qe8ngu2.fsf@linuxsc.com> References: <10ib0ka$3cgil$1@dont-email.me> <10ibava$2sora$1@dont-email.me> <10ibcub$25ihi$2@dont-email.me> <10ibu81$2sora$2@dont-email.me> <10ibvrm$25ihh$2@dont-email.me> <20251222204538.00003fc2@yahoo.com> <10iekvr$pa8n$1@paganini.bofh.team> <20251224000824.00005ce7@yahoo.com> <10iga40$11ds6$1@paganini.bofh.team> <20251224121211.00000e8f@yahoo.com> <20251228024431.00000016@yahoo.com> <10iqfpd$2g8io$1@paganini.bofh.team> <20251228123533.000062a2@yahoo.com> <20260105142144.000074ac@yahoo.com> <10jldr2$1khpu$1@paganini.bofh.team> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Date: Thu, 08 Jan 2026 17:40:25 +0000 (UTC) Injection-Info: dont-email.me; posting-host="f646824e109d26d154da12d2f3c25277"; logging-data="1779847"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+iJpiiNfLrXkghQB8mc4CbS0K5z+aXObA=" User-Agent: Gnus/5.11 (Gnus v5.11) Emacs/22.4 (gnu/linux) Cancel-Lock: sha1:BstbyUuVjvcuo/qW/SQSd4Pg8A0= sha1:ZxDJP8MdzOsa0qjAWhi0BgXJ7lk= Xref: csiph.com comp.lang.c:396303 antispam@fricas.org (Waldek Hebisch) writes: > Michael S wrote: > >> I experimented a bit more (in fact, more like a lot more) with >> test batteries of L?Ecuyer. It led me to conclusion that occasional >> failure in the either middle or big battery means nothing. >> Sometimes even cripto-quality PRNG does not pass one or another test. >> Then you try to reproduce it and see that with any other seed that you >> try a failure does not happen. >> All in all, it makes me more suspect of PRNGs that consistently pass >> both batteries with various seed. I start to see it as a sign of >> PRNG being rigged to pass tests. > > Well, that depends on the tests and threshhold in the tests. > Some tests when fed with trurly random source will produce produce > very small variation of the results. With generous threshhold > such test will essentially never fail for trurly random source. > OTOH when expected variation of the results is larger and > threshhold is tight, then trurly random source will fail the > test from time to time. And if you test long enough you should > be able to estimate probability of failure and possibly compare > is with theoretical result if available. It's inherent in the nature of statistical testing that every so often a statistical test will "fail" even for a truly random input. An input source that never fails can also be indicative of a low quality source (and perhaps one that was tuned to the particular set of tests being done). It took me a while to learn that the results of a PRNG test suite should not be seen as purely binary.