Re: Mersenne: Meanwhile, in another part of the planet
A global celebration at the same time... good idea.. Halliday, Ian wrote: I'm just quietly reading about the possibly enormous and possibly tiny party to celebrate the discovery of M39. Is there anyone who would care to join me for a couple of quiet beers in Wellington, New Zealand to celebrate the same event? Expressions of interest or flames to me off the list please. Thank you. Regards, Ian -- Ian W Halliday, BA Hons, MIMIS, AAIBF Snr, ATMB, CL +64 27 245 6089 (GMT+13) http://baptism.co.nz Focus On Success -- Word documents not accepted -- see http://baptism.co.nz/word.html _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Trial factoring time
Hi, At 12:46 AM 11/27/2001 +0100, george de fockert wrote: One of my machines does trial factoring. Now in the M1790 range, factoring to 2^66. This takes a very long time, is it better to let it double check ? It is a matter of personal preference. You can figure out how long a double-check would take at http://www.mersenne.org/bench.htm Another option for slow machines is ECM factoring. See http://www.mersenne.org/ecm.htm for details (this is not an automated project) Or is it time for a more efficient trial factor implementation (if possible ?). If someone wants to volunteer to improve factoring performance that would be great. The P4 could use an SSE2 implementation. CPU-specific factoring code over 64 bits could be written. While factoring could probably be improved tens of percent, it has not been a high priority item for me. A 10% boost in factoring speed lets you factor (on average) 10% deeper, which finds about 1 more factor in every 650 exponents. That isn't a great throughput improvement for the GIMPS project. -- George _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Factoring benefit/cost ratio (was: Mersenne: Fw: The Mersenne Newsletter, issue #18)
Earlier, Brian Beesley wrote: Eh? Doesn't it make more sense to concentrate on factoring Mnumbers that haven't yet been L-L tested? That way success in finding a factor reduces the number of LL tests, as well as (eventually) the number of double checks. ... to which Daran G. recently responded: Not necessarily. The marginal benefit/cost ratio of doing factoring work on exponant x awaiting a first time test, is twice what it would be if exponant x were awaiting a DC. This does not mean that it is greater that doing factoring work on exponant y which is awaiting a DC. But ones factoring benefit calculation might [should would be in line with the popular theme of prescribing what's best for other GIMPS participants :)] include not only the time savings of eliminating the need for one or two L-L tests, but also the extra benefit of finding a specific factor. In the GIMPS Search Status table at www.mersenne.org/status.htm the march of progress is from Status Unknown to Composite - One LL to Composite - Two LL to ... Composite - Factored. This reflects the view (with which I agree) that it is more valuable to know a specific factor of a Mnumber than to know that a Mnumber is composite but not to know any specific factor of that Mnumber. So a Factored status is better for GIMPS than a Two LL status, but calculations of factoring benefit that consider only the savings of L-L test elimination are neglecting the difference between those two statuses. If one consciously wants to neglect that difference ... well, okay ... but I prefer to see that explicitly acknowledged. Richard Woods _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
