# Really random ? - Thread: https://externals.io/message/43248 - Original archive: https://news-web.php.net/php.internals/43248 - Started by Kenan Sulayman on 2009-03-04T13:50:05+00:00 - Messages: 8 - Reply by email to internals@lists.php.net - More for agents: search with https://externals.io/search.md?q={query} · JSON API at https://externals.io/api · documentation at https://externals.io/llms.txt --- ## #43248 — Kenan Sulayman — 2009-03-04T13:50:05+00:00 URL: https://externals.io/message/43248#43248 Hello PHP internals, I've been running several million tests regarding the arithmetically-random-functions. The returning value at the end: Avg: mt_r: 1073848211.4106 r: 16384.155746685 ~8016909 Avg: mt_r: 1073904131.0286 r: 16384.164383921 ~8503575 Avg: mt_r: 1074010520.4456 r: 16384.091213092 ~13136327 Shape: Avg: mt_r: { avg of `mt_rand()` } r: { avg of `rand()` } ~ { value of $i ( iterations ) } Means: Average of mersenne twister in 8016909 it's is 1073848211.4106 ( corresponding to that in 8503575 it's the avg. is 1073904131.0286). That's acceptable. The rand(x) function alters the avg in 5M iterations really by just 0.1 ? Wow, that's creepy. Is there any way - to make it better ( or a bit as good as the m_twister is ? ) ? Thanks, -- (c) Kenan Sulayman Freelance Designer and Programmer Life's Live Poetry --- ## #43249 — Pierre Joye — 2009-03-04T14:30:40+00:00 URL: https://externals.io/message/43248#43249 · In reply to: #43248 hi, > I've been running several million tests regarding the > arithmetically-random-functions. > > The returning value at the end: > Avg: mt_r: 1073848211.4106 r: 16384.155746685 ~8016909 > Avg: mt_r: 1073904131.0286 r: 16384.164383921 ~8503575 > Avg: mt_r: 1074010520.4456 r: 16384.091213092 ~13136327 > > Shape: > Avg: mt_r: { avg of `mt_rand()` } r: { avg of `rand()` } ~ { value of $i ( > iterations ) } > > Means: > Average of mersenne twister in 8016909 it's is 1073848211.4106 ( > corresponding to that in 8503575 it's the avg. is 1073904131.0286). > That's acceptable. > > The rand(x) function alters the avg in 5M iterations really by just 0.1 ? > Wow, that's creepy. > > Is there any way - to make it better ( or a bit as good as the m_twister is > ? ) ? Use http://us.php.net/mtrand Still some issues but already better. Cheers, -- Pierre http://blog.thepimp.net | http://www.libgd.org --- ## #43250 — Pierre Joye — 2009-03-04T14:32:10+00:00 URL: https://externals.io/message/43248#43250 · In reply to: #43248 hi, And please disable this auto reply on your system: "Der Server hat ihre Nachricht erfolgreich verarbeitet! Vielen Dank, Ihr KurealCorporation Kunden Service." Cheers, -- Pierre http://blog.thepimp.net | http://www.libgd.org --- ## #43251 — Kenan Sulayman — 2009-03-04T14:46:42+00:00 URL: https://externals.io/message/43248#43251 · In reply to: #43250 Hey Pierre! Didn't I included the mt_rand function in my tests ? Quote: "Average of mersenne twister in 8016909 it's is 1073848211.4106 ( corresponding to that in 8503575 it's the avg. is 1073904131.0286)." The mail was meant to make the rand(x) function more good; I already use the `mt_rand()` function, but why should the rand(x) function still be used, if it's so freakin' insecure ? P.s.: Thanks for the "And please disable this auto reply on your system:"; I thought, I disabled that a year ago ;-P. Your, -- (c) Kenan Sulayman Freelance Designer and Programmer Life's Live Poetry 2009/3/4 Pierre Joye > hi, > > And please disable this auto reply on your system: > > "Der Server hat ihre Nachricht erfolgreich verarbeitet! > Vielen Dank, > Ihr KurealCorporation Kunden Service." > > > Cheers, > -- > Pierre > > http://blog.thepimp.net | http://www.libgd.org --- ## #43252 — Hartmut Holzgraefe — 2009-03-04T14:52:02+00:00 URL: https://externals.io/message/43248#43252 · In reply to: #43248 Kenan Sulayman wrote: > The rand(x) function alters the avg in 5M iterations really by just 0.1 ? > Wow, that's creepy. > > Is there any way - to make it better ( or a bit as good as the m_twister is > ? ) ? there's a reason why `mt_rand()` is referred to as "Generate a better random value" in the `rand()` documentation ;) And i can't resist to add http://web.archive.org/web/20011027002011/http://dilbert.com/comics/dilbert/archive/images/dilbert2001182781025.gif -- Hartmut Holzgraefe, MySQL Regional Support Manager, EMEA Sun Microsystems GmbH, Sonnenallee 1, 85551 Kirchheim-Heimstetten Amtsgericht Muenchen: HRB161028 Geschaeftsfuehrer: Thomas Schroeder, Wolfgang Engels, Dr. Roland Boemer Vorsitzender des Aufsichtsrates: Martin Haering --- ## #43253 — Stefan Walk — 2009-03-04T15:28:49+00:00 URL: https://externals.io/message/43248#43253 · In reply to: #43251 > Hey Pierre! > > Didn't I included the mt_rand function in my tests ? > > Quote: "Average of mersenne twister in 8016909 it's is > 1073848211.4106 ( > corresponding to that in 8503575 it's the avg. is 1073904131.0286)." > > The mail was meant to make the rand(x) function more good; > I already use the `mt_rand()` function, but why should the rand(x) > function > still be used, if it's so freakin' insecure ? I hope that by "insecure" you don't imply that you're using those pseudorandom generators for cryptography purposes. As the manual states, `rand()` uses the libc `rand()`, which can be desirable if you want to generate the same sequence of numbers across languages. And you don't need to complain about its drawbacks, because they are well- known (see ). If you want "secure" random numbers, use something that at least tries to utilize "real" entropy. But that topic has nothing to do with the development of PHP ... Regards, Stefan --- ## #43255 — Kenan Sulayman — 2009-03-04T15:44:09+00:00 URL: https://externals.io/message/43248#43255 · In reply to: #43253 Guess you're right ;-D Thanks! -- (c) Kenan Sulayman Freelance Designer and Programmer Life's Live Poetry 2009/3/4 Stefan Walk > > > > Hey Pierre! > > […] > > I hope that by "insecure" you don't imply that you're using those > pseudorandom generators for cryptography purposes. As the manual states, > `rand()` uses the libc `rand()`, which can be desirable if you want to generate > the same sequence of numbers across languages. And you don't need to > complain about its drawbacks, because they are well-known (see < > http://en.wikipedia.org/wiki/Linear_congruential_generator#Advantages_and_disadvantages_of_LCGs>). > If you want "secure" random numbers, use something that at least tries to > utilize "real" entropy. But that topic has nothing to do with the > development of PHP ... > > Regards, > Stefan --- ## #43261 — Tim Starling — 2009-03-05T03:42:18+00:00 URL: https://externals.io/message/43248#43261 · In reply to: #43248 Kenan Sulayman wrote: > Hello PHP internals, > > I've been running several million tests regarding the > arithmetically-random-functions. > > The returning value at the end: > Avg: mt_r: 1073848211.4106 r: 16384.155746685 ~8016909 > Avg: mt_r: 1073904131.0286 r: 16384.164383921 ~8503575 > Avg: mt_r: 1074010520.4456 r: 16384.091213092 ~13136327 > > Shape: > Avg: mt_r: { avg of `mt_rand()` } r: { avg of `rand()` } ~ { value of $i ( > iterations ) } > > Means: > Average of mersenne twister in 8016909 it's is 1073848211.4106 ( > corresponding to that in 8503575 it's the avg. is 1073904131.0286). > That's acceptable. > > The rand(x) function alters the avg in 5M iterations really by just 0.1 ? > Wow, that's creepy. > You're exhausting the period. It's not creepy, it's expected, for a random number generator with only 16 bits of state. > Is there any way - to make it better ( or a bit as good as the m_twister is > ? ) ? > No, apparently it's conventional to expose whatever crap PRNG the system has lying around instead of forcing programmers to use one of the two perfectly good ones that PHP bundles. -- Tim Starling