Re: Factoring small numbers

[Charles Greathouse <charles.greathouse@case.edu>]

Are you sure it's not storing found factors?

removeprimes(setintersect(addprimes(), factor(19180172397815991981)[,1]~));
default(factor_add_primes,0)
for(i=1,1000,factor(19180172397815991981))
##

I get 52 ms for the factorization, and I don't think my computer is 20 times slower than yours. (2 or 3 times, maybe.)

Charles Greathouse
Analyst/Programmer
Case Western Reserve University

On Thu, May 8, 2014 at 12:45 PM, Igor Schein <igorschein@gmail.com> wrote:

On Thu, May 8, 2014 at 12:40 PM, Jeroen Demeyer <jdemeyer@cage.ugent.be> wrote:
> Dear pari-dev,
>
> While working on Sage today, I was very amazed that GAP is much faster than
> PARI for factoring small numbers.
>
> For example, for factoring 19180172397815991981, GAP beats PARI by a factor
> of about 20. As far as I know, PARI uses rho + MPQS while GAP only uses
> Pollard rho. So perhaps PARI shouldn't use MPQS for numbers of this size.
>
> Any opinions?
>
>
> Cheers,
> Jeroen.
>

gp takes under 3ms to factor 19180172397815991981.  Hard to beat that IMO.

Igor