Re: [boost] [xint] Third release is ready, requesting preliminary review

Subject: Re: [boost] [xint] Third release is ready, requesting preliminary review
From: DE (satan66613_at_[hidden])
Date: 2010-05-02 16:39:54

on 02.05.2010 at 20:48
 Chad Nelson wrote :
>> I'm curious:  Are you researching, or do you have plans to research,
>> more efficient multiplication algorithms (Karatsuba's, FFT-based, etc.)?
>> I believe these only become efficient at large integers, but I'm not
>> sure how large...

> Yes, I already have a description of the Karatsuba one to work from, for
> a later release. It's supposed to be more effective than the traditional
> version once you get past a certain size, but I don't know what that
> size is yet. Once that's added, I'll look into the others.

wikipedia says that kartsuba gains any advantage starting from ~10000
_decimal_ digits (that is roughly )

>> Okay, some questions regarding the arithmetic functions:  It looks like
>> you have named free functions for all the arithmetic operators which
>> have identical functionality to the overloaded arithmetic operators.
>> This was obviously deliberate.  Can you comment on this decision, i.e.,
>> why have the named free functions at all?

> Originally those were the functions that handled the internals. I had to
> move the internals down by another layer of abstraction in order to
> efficiently handle the fixed_integer types, and I just never thought to
> remove the free functions.

>> Do you have free functions that implement the low-level arithmetic
>> operations for just pairs of pointers? [...]

> Not pairs of pointers, but I do have lower-level functions (the ones in
> the detail namespace) that work on base_integer types.

>> ?  Okay this signature is probably not what you'd want, but

>> [...] more fundamentally my question is, have you separated the
>> arithmetic/numeric algorithms from the memory management algorithms?

> They're separated, in that the memory management is all done by the
> base_integer class, and the math is handled by the higher classes and
> free functions.

>> Can one build their own, e.g., stack-based integer class as just a
>> wrapper around the arithmetic algorithms?

> Maybe, if one wants to implement all the free functions for their type.
> :-) I hadn't considered that anyone might want to.

>> Also, I don't see any allocator template parameters anywhere.  I'm
>> guessing any consideration of acceptance into boost is conditional on
>> allocator support.

> <sigh> I wish someone had mentioned that before. Not that it makes that
> much difference... while trying to add the data-caching stuff to the
> fixed_integer types last night, I came to the conclusion that I needed
> something like that anyway.

>> Very nice work on the documentation.  I'll have to continue to troll
>> through it at my usually leisurely pace.

> Thanks!

-- 
Pavel
P.S.
if you notice a grammar mistake or weird phrasing in my message
please point it out