Re: [boost] [XInt] Some after thoughts

Subject: Re: [boost] [XInt] Some after thoughts
From: Jeremy Maitin-Shepard (jeremy_at_[hidden])
Date: 2011-03-10 18:36:12

On 03/10/2011 01:06 AM, falcou wrote:

 > [snip]

> 4/ Have a way to say large integer use SIMD register of 128 bits and
> implement a SIMD aware large integer
>

This last item seems particularly useful, but I don't see how it has 
anything to do with a potential restructuring.  Since non-bitwise 
operations aren't explicitly single instruction multiple data 
operations, really what we are talking about is optimizing the library 
so as to make the most use of the processor capabilities, which may 
include SSE instructions, etc.  (Presumably the performance of GMP 
already reflects such optimizations.)

Maybe what you have in mind is letting the digit type be a template 
parameter, and then substituting in a user-defined type (or in the case 
of some compilers, a compiler-defined non-standard type) that serves as 
a 128-bit unsigned integer.  I'm not convinced that this level of 
abstraction is compatible with generation of optimal code, though. 
Furthermore, this abstraction doesn't seem particularly useful, as the 
only purpose I can imagine of specifying a non-default digit type would 
be for this particular optimization.