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 2004-05-25, 08:46 #1 Boulder   May 2003 3×13 Posts 28.0M - 28.01M to 65 bits for starters Hi, I've started factoring the range to 65 bits. I'll probably go deeper as soon as the round is complete and I'll keep you posted.
 2004-07-08, 12:33 #2 Boulder   May 2003 3×13 Posts Now going at M28005269, only one exponent with a factor found so far
 2004-07-08, 14:20 #3 ThomRuley     May 2003 23·31 Posts One exponent? That's great! One less exponent for LL testing. Your couple hours of factoring just saved the project about a month of LL. Great job.
 2004-07-08, 17:15 #4 Boulder   May 2003 3×13 Posts Well, I would have expected a couple but then again, aren't the factors more rare when you TF the exponents 'deeper' ?
 2004-07-08, 21:42 #5 Uncwilly 6809 > 6502     """"""""""""""""""" Aug 2003 101×103 Posts 24·593 Posts Consider that by factoring up to 55bits, many many factors have been removed (maybe 50% of all exponents are eliminated by factoring to 55bit). What you are doing is squeezing a few more out before P-1 will get ~1% of the remaning. All of this proves that it is not prime and saves much time in the hunt.
 2004-07-09, 04:31 #6 markr     "Mark" Feb 2003 Sydney 3·191 Posts All factors are good - they save on LL tests! One factor is well within what's expected: if I'm close in reckoning that you had TF'd 114 exponents from 2^64 to 2^65, you had 30% chance of one factor and 27% chance of two factors. According to prime95's help file, the chance of finding a factor for an exponent between 2^b & 2^(b+1) is approximately 1/b. The killer is that the time taken doubles. It is very much worth it though - TF will still be cost-effective up to 2^67 for these exponents.
 2004-07-09, 05:29 #7 Boulder   May 2003 1001112 Posts Thanks for the explanations, guys. I've been thinking about starting TF'ing the remaining exponents to 2^66 as soon as 2^65 is finished but I'm not sure how far I would get before the range will be in PrimeNet. Since I do some real work on the computer (a P4-2.76GHz), it's very hard to estimate the time needed. At the moment the time per exponent is a bit over three hours if I'm not doing anything special. If I shut down all the other processes the time might go down to two and a half hours so it would take about 5-7 hours per exponent when TF'ing to 2^66. Guess I'll just go with the range as long as I can EDIT: By the way, is it that TF'ing to 2^64 is not as effective on a SSE2-capable machine as to 2^65? Last fiddled with by Boulder on 2004-07-09 at 05:37
 2004-07-09, 07:34 #8 markr     "Mark" Feb 2003 Sydney 3×191 Posts Above 2^64, SSE2 gives a big advantage - I don't know by how much. Below 2^62, Athlons outpace P4s apparently because of some fancy coding that does two-for-one somehow. I don't know any more about why it is (and even this might be wrong!) or where non-SSE2 intel cpus fit in, but I do know that for TF below 2^62 an Athlon XP at 1533MHz is way faster than a P4 at 1800MHz. In between... not sure.
 2004-07-09, 10:40 #9 garo     Aug 2002 Termonfeckin, IE 32×307 Posts These were some tests I ran a while back: Time taken to complete 14366959 to 0.98% Code: To Bit On PII 450 On P4 2533 Improv On 1333TB Improv 59 6 2.5 2.4 1.85 3.25 60 12 5 2.4 3.7 3.25 61 24 10 2.4 7.4 3.25 62 48 20 2.4 14.8 3.25 63 170 37.5 4.5 51 3.33 64 340 75 4.5 102 3.33 65 1540 180 8.5 480 3.21 Last fiddled with by garo on 2004-07-09 at 10:41
 2004-11-06, 11:18 #10 Boulder   May 2003 3×13 Posts Hi all, I had an HD crash two months ago and lost a lot of work. I'm now attempting to factor the range to 2^65 before it hits the network, but can't promise anything. I remember seeing at least one number being factored so there's some motivation at least. Please notify me if the range goes out, I might not remember to log in often.
 2004-11-18, 15:27 #11 Boulder   May 2003 1001112 Posts OK, I'll release the range as it should soon enter PrimeNet. I emailed the results to George, I nailed that one candidate which I remembered getting factored

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