whats happening ?

Jason Moxham J.L.Moxham@maths.soton.ac.uk
Sat, 2 Nov 2002 02:52:30 +0000

On Wednesday 23 Oct 2002 1:08 am, Kevin Ryde wrote:
> Jason Moxham <J.L.Moxham@maths.soton.ac.uk> writes:
> > mpz_rootexact (like mpz_divexact but for roots)  using varible precis=
> > , division free p-adic newton method
> Not sure if there'd be much direct use for that.  When would one know
> a number is an exact power?

I have come across it a few times , but nothing springs to mind . If the=20
p-adics are faster (than real newton iterations)(and they should be) for=20
perfect_power testing then we can get the mpz_rootexact for free.

> > mpz_perfect_power_p using parts of the above fn's
> If it finds a use there then it'd be fine.
> > mpz_invert_2exp (like mpz_invert but 2^n modulas) again using above
> > p-adics

again this fn would come for free from a p-adic perfect power testing fn =
although I don't know of any uses besides redc-init

> I looked at that as part of the redc, since it wants such an inverse.
> The function would match mpz_invert nicely, but again I'm not sure
> quite how much use it would get.
> Paul Z had some ideas about efficiency which I've (still) yet to look
> at properly.  Efficiency isn't a big deal for the prospective mpm
> since the inverse is calculated just once at the start.

interesting , they could be usefull for the p-adic perfect power test