Re: [boost] [random] new threefry random engine

AMDG On 06/13/2014 09:17 AM, John Salmon wrote:

On Tue, May 27, 2014 at 2:48 PM, John Salmon wrote:

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Can we agree that counter_based_engine, implemented roughly along these lines is a worthwhile addition to Boost.Random? If so, what's the way forward?

The main thing I need is documentation as doxygen+quickbook.

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Should I start a 'feature branch', i.e., https://svn.boost.org/trac/boost/wiki/StartModMaint#Startworkonanewfeature to make it easier to ultimately merge into boost?

Sure. The headers aren't a big deal, since it's trivial for me to copy files, but the documentation does need to be integrated into the Boost.Random docs. - threefry primary template: BOOST_STATIC_ASSERT( N==2 || N==4 ) Just don't provide the primary template. - counter_traits.hpp: comments about SeedSeq and birthday paradox. I'm not sure that this is actually true. It's obviously the case that mapping from 4 integers to 3 is going to have this problem, but there is no way around this. If the destination range is larger, then I really hope the outputs would always be distinct for distinct inputs of the same size. I haven't analyzed the algorithm and I have no idea where it comes from, but if it doesn't have this property, then some outputs would be totally unreachable. (Of course, the performance issues of seed_seq still apply.) - Making detail::counter_traits a template parameter of counter_based_engine adds boost::random::detail to the set of associated namespaces. - make_counter and 64-bit: Boost.Random generally requires 32-bit sequences. (This is inherited from std::seed_seq) Handling different widths is a lot of complication for - The iterator seed and constructors of counter_based_engine are overloaded based on the constness of the first argument. Don't do this. It's far to error-prone. - I'm unconvinced of the value of restart. I'm thinking that we can get the same result by allowing multiprecision integers with discard.

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Second ping, Can anybody hear me?

It's been more than two weeks, with no response to the above, nor to a resend on June 3. I understand that people are busy. But note that I'm asking what *I* should do, not for someone else to do something. In any case, a reply along the lines of "I'm busy and won't be able to get into this until approximately <DATE>, but until then, you could help by doing XXX" would be appreciated.

In Christ, Steven Watanabe