Re: Factoring small numbers

[Igor Schein <igorschein@gmail.com>]

100% sure.  I even started the new session and cleaned up tmp
directory just in case.  This was on my VM.  On a faster machine it
takes less than 1ms.  I am using pari-2.8.
Igor.

On Thu, May 8, 2014 at 2:05 PM, Charles Greathouse
<charles.greathouse@case.edu> wrote:
> 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
>>
>