Re: [boost] Removing auto_ptr/etc. from Boost

Subject: Re: [boost] Removing auto_ptr/etc. from Boost
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2015-03-19 20:47:31

On 19 Mar 2015 at 19:33, Stephan T. Lavavej wrote:

> [STL]
> > (mt19937 is awesome, but at 5 KB I'd be slightly nervous about making it thread_local.)
> 
> [Steven Watanabe]
> > boost::mt19937 is only 2.5 KB.
> 
> Thanks - I see where the factor of 2 is coming from, although it'll need a bit more thought to untangle. I've filed a bug in our internal database.

Anyone considering using mt19937 should be aware it was painfully 
slow on ARM where it used the generic C implementation. I use the 
past tense because I don't know the current state of things having 
excised all uses of Mersenne from my code as a result - nevertheless, 
Mersenne is only awesome on Intel, and a similar dog slow speed to a 
crypto random source on some other CPUs.

Personally speaking if I need portable, fast, not awful randomness, I 
like http://burtleburtle.net/bob/rand/smallprng.html. It's much 
faster to initialise than mersenne too, runs very well on all CPUs 
without special opcodes, but the output isn't quite as random. As a 
rand() replacement it ought to be plenty fine, a 2^126 average period 
is plenty.

Niall

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