On Thu, Sep 2, 2021 at 5:10 PM Go Kudo <zeriyo...@gmail.com> wrote: > Hi Internals. > > Expanded from the previous RFC and changed it to an RFC that organizes the > whole PHP random number generator. Also, the target version has been > changed to 8.2. > > https://wiki.php.net/rfc/rng_extension > https://github.com/php/php-src/pull/7453 > > Hopefully you will get some good responses. >
This RFC currently tries to keep some semblance of compatibility with the existing mt_rand() algorithm by retaining the same implementation for mapping the raw random number stream into a range. However, the algorithm we use for that is not exactly state of the art and requires two full-width divisions at minimum. There are more efficient scaling algorithms based on fixed-point multiplication, which are "nearly divisionless" ( https://arxiv.org/pdf/1805.10941.pdf). The variant at https://github.com/apple/swift/pull/39143 is entirely divisionless. Doing this would improve performance (though I'm not sure by how much -- maybe once we add up our call overhead, it isn't important anymore?) but it would provide a different sequence than mt_rand(). Something we might want to consider. Regards, Nikita
