Re: com php-src: Fix #71152: mt_rand() returns the different values from original mt19937ar.c: ext/standard/rand.c
ext/standard/tests/math/mt_rand_value.phpt

On Wed, Feb 17, 2016 at 4:32 AM, Xinchen Hui <laruence@php.net> wrote: > Commit: 6f6bd8ce531636134efd5f669a4e8373fb2e9e51 > Author: kusano <kusano@users.noreply.github.com> Thu, 17 Dec > 2015 19:26:38 +0900 > Committer: Xinchen Hui <laruence@gmail.com> Wed, 17 Feb 2016 > 11:32:59 +0800 > Parents: 837e2a912d1fb1b38438f0fe26362baf5b848467 > Branches: PHP-7.0 master > > Link: > > http://git.php.net/?p=php-src.git;a=commitdiff;h=6f6bd8ce531636134efd5f669a4e8373fb2e9e51 > > Log: > Fix #71152: mt_rand() returns the different values from original > mt19937ar.c > > Bugs: > https://bugs.php.net/71152 > > Changed paths: > M ext/standard/rand.c > A ext/standard/tests/math/mt_rand_value.phpt > > > Diff: > diff --git a/ext/standard/rand.c b/ext/standard/rand.c > index 2dd05e7..bc32f24 100644 > --- a/ext/standard/rand.c > +++ b/ext/standard/rand.c > @@ -146,7 +146,7 @@ PHPAPI zend_long php_rand(void) > #define loBits(u) ((u) & 0x7FFFFFFFU) /* mask the highest bit > of u */ > #define mixBits(u, v) (hiBit(u)|loBits(v)) /* move hi bit of u to hi bit > of v */ > > -#define twist(m,u,v) (m ^ (mixBits(u,v)>>1) ^ > ((php_uint32)(-(php_int32)(loBit(u))) & 0x9908b0dfU)) > +#define twist(m,u,v) (m ^ (mixBits(u,v)>>1) ^ > ((php_uint32)(-(php_int32)(loBit(v))) & 0x9908b0dfU)) > > /* {{{ php_mt_initialize > */ > diff --git a/ext/standard/tests/math/mt_rand_value.phpt > b/ext/standard/tests/math/mt_rand_value.phpt > new file mode 100644 > index 0000000..eeb009e > --- /dev/null > +++ b/ext/standard/tests/math/mt_rand_value.phpt > @@ -0,0 +1,53 @@ > +--TEST-- > +Test mt_rand() - returns the exact same values as mt19937ar.c > +--FILE-- > +<?php > + > +mt_srand(12345678); > + > +for ($i=0; $i<16; $i++) { > + echo mt_rand().PHP_EOL; > +} > +echo PHP_EOL; > + > +$x = 0; > +for ($i=0; $i<1024; $i++) { > + $x ^= mt_rand(); > +} > +echo $x.PHP_EOL; > + > +/* > +excpect values are obtained from original mt19937ar.c as follows: > + > +int i, x; > +init_genrand(12345678); > +for (i=0; i<16; i++) { > + printf("%d\n", genrand_int31()); > +} > +printf("\n"); > +x = 0; > +for (i=0; i<1024; i++) { > + x ^= genrand_int31(); > +} > +printf("%d\n", x); > +*/ > +?> > +--EXPECTF-- > +527860569 > +1711027313 > +1280820687 > +688176834 > +770499160 > +412773096 > +813703253 > +898651287 > +52508912 > +757323740 > +511765911 > +274407457 > +833082629 > +1923803667 > +1461450755 > +1301698200 > + > +1612214270 > Does this change the mt_rand sequence for all seeds or only specific seeds? If the former, please do not apply it to PHP-7.0, it will break tests. Also, if we're going to change the mt_rand sequence, we should also fix the scaling at the same time. Nikita