Re: [boost] [xint] Boost.XInt formal review

Subject: Re: [boost] [xint] Boost.XInt formal review
From: Ivan Le Lann (ivan.lelann_at_[hidden])
Date: 2011-03-06 17:50:55

Le dimanche 06 mars 2011 à 08:20 -0500, Chad Nelson a écrit :
> >>
> >> 1. Parametrize with container type. [...]  
> >
> > I actually tested earlier iterations with containers such as vector
> > for their storage. The performance numbers were noticeably worse.
> >

You're restricting this to std::vector against your array, when many
container could fit. I did following modifications on reviewed XInt:

- naively turn magnitude_manager_t into a boost::array wrapper 
- add byref args in integer, raw_integer (and others, to compile)
- nothing else

(NB: I used the original with byref too as this was faster)

I used dummy code introduced by Phil Endecott with various fixed
lengths. Even at 20000 bits, boost::array version is almost twice
faster. At 2000 bits, thrice faster. I did not optimize boost::array
usage, using plain zero init in constructor, and I probably missed some
copies. Oh, by the way, boost::array version should be threadsafe.

My point: You're making choices in place of your user. This is a
dangerous way. If you like container genericity idea suggested by the
reviewer, I might try to provide my humble and limited help. I do not
consider this exposing internals, but rather keeping the internals out.
There is too much code in your library, actually.

Having said that, your library works well and seems easy to hack. A very
good point for the future. I'm not experienced enough to properly review
it but that's definitely a good one IMHO.

Ivan