Karim BELABAS on Fri, 07 Nov 2003 12:11:40 +0100 |
[Date Prev] [Date Next] [Thread Prev] [Thread Next] [Date Index] [Thread Index]
Re: Experimenting with the Alpha build. |
On Thu, 6 Nov 2003, Phil Carmody wrote: > --- Karim BELABAS <Karim.Belabas@math.u-psud.fr> wrote: >> On Thu, 6 Nov 2003, Phil Carmody wrote: >>> I was wondering if -ffast-math would do to Pari/GP/GMP on the alpha. >>> The speed-ups weren't significant on the whole (I should have tried >>> -mno-ieee too perhaps) >> >> This is expected: there's almost no floating point code in PARI (everything >> is emulated using 'unsigned long' arithmetic). Might be considered a >> shortcoming. >> >> There are lots of variables of type 'double', but they are used in parts of >> the code which is negligible timewise. And never where stability / accuracy >> is important. I.e --fast-math should be a no-op with respect to performances >> or results. > > I also recompiled GMP with -ffast-math too for the test. In theory GMP might > perform some FP maths (FFT multiplication? or is it NTT?). NTT from a quick glance at the code. I don't think GMP uses doubles much, either. mp_limb_t is always a variant of some unsigned integer (int, long, long long). Cheers, Karim. -- Karim Belabas Tel: (+33) (0)1 69 15 57 48 Dép. de Mathématiques, Bât. 425 Fax: (+33) (0)1 69 15 60 19 Université Paris-Sud http://www.math.u-psud.fr/~belabas/ F-91405 Orsay (France) http://pari.math.u-bordeaux.fr/ [PARI/GP]