Re: [boost] [review] Multiprecision review scheduled for June 8th - 17th, 2012

Subject: Re: [boost] [review] Multiprecision review scheduled for June 8th - 17th, 2012
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2012-06-05 11:30:29

On Thu, May 31, 2012 at 12:58 AM, Marc Glisse <marc.glisse_at_[hidden]> wrote:

> (sorry for the broken thread, I wasn't subscribed yet)
>
> A few quick comments:
>
> * gmpxx != mpfr_class
>
> * the version of gmpxx in the repository hasn't used any temporary for the
> example given in the introduction for a while, it is only because of a slow
> release cycle that you haven't seen it yet (will be in 5.1).
>
> * the example about using 0 vs 11 temporaries doesn't mention what happens
> to the boost package if we disable expression template. Does it use a
> single temporary (using rvalue-references) or plenty?
>
> * having an implicit narrowing conversion from double to bigint is a bad
> idea, it should be explicit (it isn't completely obvious from the doc if
> that is the case).
>
> * you could get good results with a backend that uses gmp's mpn_*
> functions but not the mpz_t type.
>
> * what about infinite precision floats? By that I mean something like
> bigint*2^n, where operations + - * are computed exactly. It can be quite a
> bit faster than rationals, when it is sufficient.
>
> * if I want reference-counting, I guess that should be done in a back-end.
>

Thanks for the pre-review comments, Marc; it's good to get such detailed
exposure prior to the formal review! I'm doing my best to track your
concerns.

- Jeff