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

Subject: Re: [boost] [review] Multiprecision review scheduled for June 8th - 17th, 2012
From: Marc Glisse (marc.glisse_at_[hidden])
Date: 2012-05-31 03:58:11

(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.

-- 
Marc Glisse