Re: A bug with factorint?

["Juan Luis Varona Malumbres" <jvarona@dmc.unirioja.es>]

Gerhard,

Thanks a lot for the answer.

I has been checking (with the same number) using your idea (flag=6),
and it seems that MPQS will expend about a month. So it is true,
it is not a very good MPQS implementation.

Anyway, I think it will be useful a possibility to control
the number of elliptic curves with gp code.

Yours,

Juan L. Varona

> > We never reach MPQS method.
>
> That is true only for large values of "never". :)  ECM in fact told
> you in advance that it was going to try for 38 iterations.
>
> You can suppress the ECM stage before MPQS through the flag argument
> to factorint  (use 6),  but MPQS on a 95-bit number with the present
> implementation will require on the order of many months  (sufficient
> memory assumed, and a stable system and reliable power supply) - enough
> to justify spending 3 weeks on ECM first, although this looks counter-
> intuitive to us impatient human spectators.
>
> Your best bet at present, if you want to do this with gp, is to
> attempt the factorization simultaneously on two machines with
> different flag settings, so that one will keep churning away
> with ECM while the other embarks on MPQS.  You'll find that this
> ECM stage will give up long before MPQS approaches the Gaussian
> elimination phase.  Of course, you can run software more specialized
> towards integer factorization simultaneously on a third machine...
>
> Cheers, Gerhard