Karim BELABAS on Mon, 21 Feb 2000 19:38:47 +0100 (MET) |
[Date Prev] [Date Next] [Thread Prev] [Thread Next] [Date Index] [Thread Index]
Re: p-adic shift |
[Diana Bosio:] > I am working on p-adic dynamics and would like to use PARI in library > mode for some of my computations. One of operations I need to perform > is a p-adic shift. I know there is a dyadic shift, I would like to > know if there is an analogue for p (apart from the obvious division by > p^n). If not, can I rely on the division by p^n as being exact, > provided I am in the ideal (p^n)? Hi, 1) there is no p-adic shift for p > 2. 2) you can rely on gdiv(x, pn) being an integer (t_INT) if pn divides x. It will be a t_FRAC otherwise. Also, you can always use divii(x, pn) which only computes the euclidean quotient (and will be a bit faster). 3) IF x is of type t_PADIC, then gdiv(x, p) will actually perform a kind of p-adic shift (updating valp(x)). BUT padics are a nightmare in terms of efficiency so you'll be much bettter off sticking to integers. Good luck, Karim. __ Karim Belabas email: Karim.Belabas@math.u-psud.fr Dep. de Mathematiques, Bat. 425 Universite Paris-Sud Tel: (00 33) 1 69 15 57 48 F-91405 Orsay (France) Fax: (00 33) 1 69 15 60 19 -- PARI/GP Home Page: http://hasse.mathematik.tu-muenchen.de/ntsw/pari/