Re: Use of php_mt_rand() rather than php_rand()

Hi all, On Wed, Jul 16, 2014 at 2:13 PM, Yasuo Ohgaki <yohgaki@ohgaki.net> wrote: > There are few places that uses php_rand() currently. > > https://bugs.php.net/bug.php?id=66718 > > 2]Õèð[9­D > €nrÝ+http://lxr.php.net/search?q=php_rand&defs=&refs=&path=&hist=&project=PHP_5_5 > > These functions could use php_mt_rand() instead of php_rand(). > > php_rand() uses several rand functions > > 62PHPAPI long php_rand(TSRMLS_D) > 63{ > 64 long ret; > 65 > 66 if (!BG(rand_is_seeded)) { > 67 php_srand(GENERATE_SEED() TSRMLS_CC); > 68 } > 69 > 70#ifdef ZTS > 71 ret = php_rand_r(&BG(rand_seed)); > 72#else > 73# if defined(HAVE_RANDOM) > 74 ret = random(); > 75# elif defined(HAVE_LRAND48) > 76 ret = lrand48(); > 77# else > 78 ret = rand(); > 79# endif > 80#endif > 81 > 82 return ret; > 83} > > Most systems use random() which has cycle of 16 * ((2^31) - 1), > while MT rand has 2^19937-1. > > php_mt_rand() could be used where php_rand() is used. Unlike php_rand(), > php_mt_rand() does not check if it is seeded or not. It should be changed > to check seed status. > > The only BC issue I can think of is game that expects the same pseudo > random sequences. These apps may use mt_srand() to get fixed random > sequences and adjust their apps if it is needed. This is acceptable BC > for new releases. IMO. > > It would be good idea to support 64bit version of MT on 64bit platforms, > too. > > http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt64.html > > Any comments? > RFC for this is created. https://wiki.php.net/rfc/use-php_mt_rand New rand() function name is TBD. I cannot think of good name, but I like rand_system(). rand() may stay as it is now also. Regards, -- Yasuo Ohgaki yohgaki@ohgaki.net