20220618, 20:01  #1 
Nov 2021
3_{16} Posts 
Question on "ECM on Mersenne cofactor" work type
I set Prime95 up to do the "ECM on Mersenne cofactor" work type and was sort of expecting that I would get an assignment that ran ECM on a cofactor of a Mersenne number many times, until it was deemed unproductive to continue. What actually happens is that I get an assignment to do ECM on a Mersenne number once, then it moves on to a different Mersenne number.
Using M2106347 as an example (approx 700000 decimal digits if my maths is correct), it has 4 known factors totalling about 50 decimal digits, so the remaining unfactored amount is relatively speaking a similar size to M2106347. Is this why we just repeat the ECM on M2106347 instead of on the unfactored amount? I still don't understand the apparent scatter gun approach where I get assigned 1 attempt at many different exponents (rather than repeatedly trying to factor the same number). 
20220619, 04:17  #2  
Jun 2003
5427_{10} Posts 
Quote:
Depthfirst vs breadthfirst search. Your best bet of finding a factor is to run ECM on the least ECMed number. Server will keep track. 

20220619, 08:23  #3 
Nov 2021
3_{10} Posts 
Thank you.

20220626, 11:49  #4  
Oct 2020
Terre Haute, IN
2×61 Posts 
Quote:


20220626, 12:56  #5 
"Jane Sullivan"
Jan 2011
Beckenham, UK
476_{8} Posts 

20220626, 13:29  #6  
Jun 2003
12463_{8} Posts 
Quote:
Last fiddled with by axn on 20220626 at 13:29 

20220626, 17:07  #7  
Mar 2019
2·5·31 Posts 
Quote:


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