16055[PrimeNumbers] Re: Sieving primo-factorials
- Feb 9, 2005I wrote:
> > The default trial factor depth in pfgw -f tries to be near optimal, i.e.Décio wrote:
> > stop when the "expected" factoring time matches prp time (although
> > different prp times for different forms is not taken into account).
> Except that it doesn't take into account the fact that n! +/- n# +/- 1 isn'tAvoiding divisibility by small primes is irrelevant for the trial factor
> divisible by primes up to n; Jim suggested that I try -f35 instead of the
> default, as that's near optimal according to his experiments.
limit. After n is passed, every prime p has estimated chance 1/p of being a
factor in a sufficiently "random" form without special factor properties.
The default -f is much better than no factoring, but experimentation can
sometimes find a better limit.
A lot of things play in so it is hard for pfgw to guess the best limit when it
doesn't first time a partial factoring and prp'ing of the particular number
(and pfgw shouldn't start doing that).
I wrote "different prp times for different forms is not taken into account".
This is one thing pfgw could do but it requires analyzing the form before
> I should grab that version -- I was running the latest compiled binary forNote that development versions at openpfgw are often less tested than released
> Linux that was available in the files area of the openpfgw group.
versions at primeform group.
Factors can be trivially verified so a possibility is:
Factor with development, verify factors, prp with release.
Jens Kruse Andersen
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