20191010, 22:20  #1 
"mrh"
Oct 2018
Temecula, ca
5·11 Posts 
Factoring M7777171
I'd like to factor 7777171, for no particular reason, other than I like the way it looks.
I threw some time at it, but it resists. What do you think would be best to try next? Just a bunch of ECM curves? Last fiddled with by mrh on 20191010 at 22:41 
20191010, 23:01  #2 
1976 Toyota Corona years forever!
"Wayne"
Nov 2006
Saskatchewan, Canada
43·103 Posts 
Yes. You've done a lot of TF AND PM1.

20191010, 23:05  #3 
"mrh"
Oct 2018
Temecula, ca
5·11 Posts 

20191010, 23:12  #4 
1976 Toyota Corona years forever!
"Wayne"
Nov 2006
Saskatchewan, Canada
114D_{16} Posts 
https://www.mersenne.org/report_ecm/...1&ecm_hi=15000
Tells you how much is done/ remaining at each digit level. I'd start with the lowest.: 50,000 (B2= 10x B1). Run as many curves as you like. 
20191010, 23:28  #5 
Sep 2003
A15_{16} Posts 

20191011, 00:03  #6 
1976 Toyota Corona years forever!
"Wayne"
Nov 2006
Saskatchewan, Canada
43×103 Posts 

20200909, 19:37  #7 
Nov 2014
11_{10} Posts 
Factoring M20825573
I'm doing something similiar at the moment: Trying to find a factor for M20825573 in order to make up for my bad DC 11 years ago (which was one of my very first tests!).
I assume ECM is the way to go from now? Or should I increase P1 again? Currently I'm running another ECM curve with B1=250000, B2=100*B1 and TF up to 75bits with mfaktc. However they take around 6 hours one, this is so long ... I might never find a factor :*( 
20200909, 20:28  #8  
Jul 2003
wear a mask
1444_{10} Posts 
Quote:
1) Finish the TF to 75 bits  you'll have then put about 300 GPU GhzDays into TF. 2) One more P1 attempt: B1 = 7,000,000, B2 = 200,000,000. 3) Complete the recommended set of 280 ECM curves at B1=50,000, B2 = 5,000,000. Steps 2 and 3 are about 300 CPU GhzDays. Note that each ECM curve gives you an independent chance of finding a factor. There's no point in increasing B1,B2 for ECM until you complete the recommended set of curves at the 25 digit level. I estimate that steps 2 and 3 represent about 2 weeks of work for my Haswell i5 cpu. That's a lot of work to dedicate to one exponent. A quixotic quest, but one that I hope is fruitful for you. 

20200910, 10:03  #9  
Nov 2014
11 Posts 
Quote:
Also, it is the only exponent showing up as "bad" in my lifetime statistic. Previously there was also M21717953 in it, which I was able to move to the category "Factor found later" with P1. I probably won't do complete t25, but maybe 100 curves or so. Last fiddled with by gLauss on 20200910 at 10:08 

20201019, 15:28  #10 
Nov 2014
11 Posts 

20201019, 16:55  #11  
"Curtis"
Feb 2005
Riverside, CA
1000101000010_{2} Posts 
Quote:
Curves at B1=50k could still find a factor, but B1=250k will have more than 5x the chance per curve (while taking about 5x as long, so oddsperday improve). 

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