20140831, 21:12  #177 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
59·157 Posts 
You need to list all known factors as the last parameter, in " ".
Otherwise you will keep finding the easy know factors and their products. Last fiddled with by Batalov on 20140831 at 21:13 
20140831, 21:23  #178 
ἀβουλία
"Mr. Meeseeks"
Jan 2012
California, USA
3^{2}·241 Posts 

20140901, 03:37  #179 
May 2013
East. Always East.
11·157 Posts 
I've read the ECM page on the Mersenne Wiki but I don't quite understand how the collaborated aspect works.
If I wanted to throw some computing power at the ECM of this exponent, how would I go about it without repeating a bunch of work? I get that there are a bunch of curves with different parameters defining them, and that they're "run" one at a time, but how do we keep track of which ones are done? 
20140901, 03:42  #180  
ἀβουλία
"Mr. Meeseeks"
Jan 2012
California, USA
100001111001_{2} Posts 
Quote:
I think what makes it different/random is the random sigma? Dunno... I should probably look into the math of it. Possibly Stupid/Wrong Last fiddled with by kracker on 20140901 at 03:43 Reason: speeling 

20140901, 03:45  #181  
Apr 2014
7×17 Posts 
Quote:
http://www.mersenne.org/report_ecm/d...nof_hi=7508981 

20140901, 10:55  #182  
"Victor de Hollander"
Aug 2011
the Netherlands
1176_{10} Posts 
Quote:
http://mersenneforum.org/showthread.php?t=18544 Each curve has a random sigma, so you can run dozens in parallel. For instance for M7508981 running XXX number of curves with a B1=YYYY , you would expect to have found a ZZ digit factor at least once (if there is one). The chance of missing a ZZ digit factor with that number of curves/B1 value is 1/e (~37%). Curves with a high B1 value take more time/computational resources, so the idea is you look for increasingly bigger factors as to not 'waste' resources on running curves with B1=millions and only finding very small factors. For instance: 1 curve with B=50,000 takes only 0.3316 GHzdays 1 curve with B=110,000,000 takes a massive 729.482 GHzdays But as pointed out earlier, the server can convert the effort with non standard B1 values, so if everyone reports their results to Primenet we don't have to worry about keeping track of the number of curves/B1 values ourselves. Quote:
Edit: I'm doing a few curves with B=1,000,000 Last fiddled with by VictordeHolland on 20140901 at 11:01 Reason: Extra info + running a few curves 

20140901, 12:00  #183  
Account Deleted
"Tim Sorbera"
Aug 2006
San Antonio, TX USA
17×251 Posts 
Quote:
(this is tangential to your question, and may be something you already know, but is possibly interesting:) For each potential factor p, there is a group order that can be (via some complex calculations, but trivial for a computer) calculated from p and sigma. The group order is within of p, so it's always roughly the same size. If this group order's factorization meets the B1 and B2 bounds that you're running at, you'll find the factor. You might notice that this is similar to P1 factoring, where if p1's factorization meets the B1 and B2 bounds, you'll find the factor. But instead of only having one shot at it, you have a nearlimitless number of different group orders that can be chosen for each p, via the sigma. This is the upside to ECM. The sigma is chosen from a large enough range that collisions are rare, so we don't have to keep track of which sigmas have already been run. We could choose sigmas sequentially, but by choosing the sigmas randomly, we allow this easy parallel collaboration. Last fiddled with by MiniGeek on 20140901 at 12:02 

20140901, 14:39  #184  
Apr 2014
1110111_{2} Posts 
Quote:
Are you still ecm'ing 9100919? Is it fair game for folks to test as well? Maybe we can have a dueling banjo session to see which one gets to 12 factors first :) http://youtu.be/4gw0fxuIvBM 

20140901, 15:16  #185 
Aug 2002
Dawn of the Dead
235_{10} Posts 
I'm wondering on sigma values. Recently I have been working M25xxx and in the first few batches I was not aware that, for several hundred worktodo lines, there were only twelve different exponents! I found a factor, and later found another one, but on submission the server rejected it as already found. Looking this up on mersenne.ca, it was found by myself!
I then put all the entries for new work in a spreadsheet, sorted them, combined the number of curves into a single assignment and then paste to worktodo. The reasoning is that, in a single run (of several thousand curves), the client will not repeat sigma, whereas with fifteen or twenty assignments of the same exponent (manual system hands out 150 curves per assignment), duplication becomes possible. I hope I'm understanding this correctly. If we are doing mass work on this, then it makes sense to run as many curves as required for the bounds, all in one discrete sequence, to avoid duplicating possible sigma values. Last fiddled with by PageFault on 20140901 at 15:18 
20140901, 15:25  #186 
Just call me Henry
"David"
Sep 2007
Cambridge (GMT/BST)
5×19×61 Posts 
There should be enough sigma values(quite possibly 2^32 or some such number) that no overlaps should happen. Multiple sigma values will find the same factor. Maybe reducing the number of curves run in each batch and reporting them to the server more often would be nice. In this case I don't think you are wanting to stop after a factor is found anyway. Finding a factor a few times doesn't reduce the chance of finding another factor. Occasionally two factors will get found at once.

20140901, 17:09  #187 
May 2013
East. Always East.
11×157 Posts 
Okay, this helps a lot. Thanks.
Increasing the B1 increases the maximum size of the factors which can be found, yes? Does that mean we start with smaller B1's for the sake of quickly finding some small factors but we eventually go bigger to find the bigger ones? EDIT: As a followup question, I would ask if that means that after a significant amount of, say, B1 = 10,000,000, doing B1 = 1,000,000 is pointless? Last fiddled with by TheMawn on 20140901 at 17:13 
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