> On Thu, 18 Mar 1999, Cornelius Caesar wrote:
> > I got the idea to do some factoring with my now slower-than-average
> > machine (a P133), but I don't want to factor at the current assignments
> > (in the 9M range); instead I would like to fill up the factor limits of
> > small exponents to some common value (56 bits or 58 bits or so).
How small an exponent? Bear in mind that the number of candidate
factors of 2^p-1 in the range (2^k,2^(k+1)) doubles with a unit
increase in k but is inversely proportional to p. i.e. trial factoring
from 61 to 62 bits for an exponent around 4 million takes about the
same time as trial factoring from 59 to 60 bits for an exponent
around 1 million. (Once you go over 62 bits, hardware starts to
interfere, testing each candidate > 2^62 takes significantly longer
than it would do if the candidate was < 2^62)
> >
> > Of course, doing it manually using "Advanced - Factor" is out of question,
> > so I thought to create appropriate entries in worktodo.ini and send the
> > results unsolicited :-) to the PrimeNet server.
Well, the PrimeNet server will mutter at you, but I think the results
would nevertheless be accepted. I'm not sure if doing things this
way would make extra work for Scott and/or George, so I think
you'd better check before embarking on a stunt like this "big time".
Also, you won't get "credit" for assignments that were not issued
by PrimeNet as part of the normal, automatic process.
> >
> > However, I seem to hit the automatic factor limit value in Prime95, or
> > something else:
> >
> > Error: Work-to-do-file contained bad factoring assignment: 65537,56
> >
> > Is it possible to do what I am trying?
What are you trying to do? Factor=65537,56 says that exponent
65537 has already been trial-factored to 56 bits, please trial factor
until the limit coded into Prime95 has been reached.
> Only by recompiling Prime95/mprime, the limits are hardcoded in
the code.
A smart hacker would be able to patch the constants directly in the
executable - but I didn't suggest it, and will strenuously deny any
liability for any consequential damage...
>
> From commonc.h in version 17.7:
>
> /* Factoring limits based on complex formulas given the speed of the */
> /* factoring code vs. the speed of the Lucas-Lehmer code */
>
> #define FAC64 9150000L /* How far to factor */
> #define FAC63 7270000L
> #define FAC62 5160000L
> #define FAC61 LIMIT192 /* This is 3960000L */
> #define FAC60 2950000L
> #define FAC59 2360000L
> #define FAC58 1930000L
> #define FAC57 1480000L
> #define FAC56 1000000L
These limits were in fact changed recently (when v17 was
introduced). Therefore there are a number of exponents which have
had one or two LL tests run, by old versions of Prime95 and/or
other programs, which have not been trial factored to the current
limit. It would be possible to winkle these out (nofactor.zip from the
database) & run trial factoring to the current limit.
It would be better to stick to the exponents that have only been
tested once - the point is that, if you find any new factors, you will
save a double-check LL test. Those exponents which have already
been double-checked, we are sure are composite, even though we
don't know any factors.
Nevertheless I feel that it would be better to run ECM instead, if
you're looking for new factors of small(ish) exponents.
Regards
Brian Beesley
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