|Igor Schein on Mon, 25 Mar 2002 19:19:59 -0500|
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|Re: A bug with factorint?|
On Tue, Jan 29, 2002 at 09:41:57AM +0100, Gerhard Niklasch wrote: [snip] > Your best bet at present, if you want to do this with gp, is to Yes, the big *if*. With all credits due to Gerhard for implementing an excellent, robust and well-intergrated factorization mechanism in pari/gp, it is not (unfortunately) the fastest available implementation of either ECM or MPQS. In particular, implementation of ECM available from ECMNET has been greatly superior to our ECM in my experience. As far as MPQS, it's inferior, in particular, to Parallel Prime MPQS algorithm, implemented by Satoshi Tomabechi. Maybe one day Gerhard will be able allocate a time slot from his busy schedule to implement PPMPQS in pari, but as of now one should be aware of alternative venues. And, returning back to ECM issue, there's too much difference between the front ends of 2 implementations to make a fair citrus-to-citrus comparison, but every time I run them side by side on the same input, ECMNET implementation is always far ahead. > 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 Igor P.S. Actually, there's one feature that I always wanted to see in gp - optionally, automatically add factors found during factorization to the prime table, given there's no more limitation of 100 entries in addprimes(). 1 problem I can see is what to do if ^C has been pressed in the middle of factorization, but I guess it's a matter of choice.