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Date: Wed, 15 Jun 2016 14:04:36 +0100
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Subject: Re: [PHP-DEV] [RFC] RNG fixes
From: j.boggiano@seld.be (Jordi Boggiano)

On 15/06/2016 13:41, Tom Worster wrote:
>     int mt_rand ( $mode = MT_RAND_COMPAT )
>
>     int mt_rand ( int $min, int $max, $mode = MT_RAND_COMPAT )
>
>     MT_RAND_COMPAT = 1
>
>     MT_RAND_MT19937 = 2
>
> A PHP user needs to make the right choice of what to use in their
> situation. A technical description of the modes would be confusing and
> unhelpful to most users. I have no idea how to document this simply,
> honestly and accurately, and without jumping to conclusions about
> suitability.
>
> This is why I think a compat/correct mode switch doesn't improve PHP.
> It's inconsistent with the spirit set out in the preamble of "PHP RFC:
> Your Title Here"[1].
>
> [1] https://wiki.php.net/rfc/template
>
> Similarly, the $mode arg allows us to add MT_RAND_XOROSHIRO128_PLUS or
> whatever (interesting to some of us, more "modern", perhaps arguably
> more "strong" or are otherwise "better") aren't improvements to PHP
> unless users are asking for them.

Just a thought here, if the goal is to provide a better interface, 
wouldn't it be better to use OO for this? Not because OO is better, but 
because it would avoid having problems if two mt_rand-using pieces of 
code are executed concurrently.

Something like this:

$gen1 = new SeededRandom(MT_RAND_MT19937, 23);
$gen2 = new SeededRandom(MT_RAND_MT19937, 23);
$gen1->rand(); // or get()? generate()?
$gen1->rand();
$gen2->rand(); // returns the same as the first call as both use seed 23

With the current situation, if you add a library that relies on mt_rand 
you can suddenly break your ability to get consistent numbers.

Cheers

-- 
Jordi Boggiano
@seldaek - http://seld.be