20060318, 07:50  #1 
"Jason Goatcher"
Mar 2005
5×701 Posts 
Need help factoring Cunningham numbers
I know I'm supposed to do Stage 1 with Prime95 and Stage 2 with GMPECM, but I can't for the life of me find the instructions.
I'll have finished up my SOB sieving by early Wednesday morning GMT, so I think I've got plenty of time to learn, but I'd really appreciate some help. Thanks in advance! 
20060318, 09:12  #2 
Jul 2004
Potsdam, Germany
831_{10} Posts 
You'll probably find this thread interesting, especially #23.
Basically, you have to: 1. Add GmpEcmHook=1 to your prime.ini 2. Enter the number you want to factor into worktodo.ini (the syntax for ECM2 can be found in whatsnew.txt  important: set B2 value to 1) 3. ecm resume [resultsFile] 1 [B1][wantedB2] > [outputFile] You have to replace the [xyz] with the resp. content. And maybe you want to add the "n" parameter to the start to lower the priority of gmpecm. 
20060319, 12:48  #3  
"Jason Goatcher"
Mar 2005
5×701 Posts 
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Also, I need to know how to reserve numbers.(I'm just now reading the other threads, so I apologize if it's easily answered) Last fiddled with by jasong on 20060319 at 12:56 

20060319, 13:11  #4  
Oct 2004
Austria
7×353 Posts 
Quote:
Edit: The seventh value (here in bold font) the line ECM=16384,11000000,1,100,0,0,1,0 determines if you want to ecm a number of the form 2^n1 or 2^n+1. 0 stands for 2^n1 and 1 for 2^n+1. Last fiddled with by Andi47 on 20060319 at 13:17 

20060319, 13:30  #5 
Feb 2004
France
2×457 Posts 
ECM vs ECM2 ?!
What are the differences between:
ECM=16384,11000000,1,100,0,0,1,0 and: ECM2=1,2,16384,1,44000000,0,20,0,0 ? Last one (ECM2) provides the following results in results file: 2^16384+1 completed 10 ECM curves, B1=44000000, B2=4290000000 T. 
20060319, 13:43  #6 
"Jason Goatcher"
Mar 2005
5×701 Posts 
I apologize in advance if a search could've solved this problem, but I'm hoping the answer will be easy for you, although not obvious to me.
I've been told ecm is a basically random process. In the case of first running Prime95 and then ecm is it still that same random process? Basically, what I'm asking is: Should I just randomly pick a number from the Cunningham tables and run it for, say, 24 hours, then report the number of curves? Or is there something else I need to be aware of? (Obviously, if I find a factor, I'll report it. ) 
20060319, 14:22  #7  
Jul 2004
Potsdam, Germany
3·277 Posts 
Quote:
If it's the first: ECM2 can be used in a much more general way, as base, exponent and constant can be chosen "arbitrarily". 

20060319, 14:30  #8  
Oct 2004
Austria
2471_{10} Posts 
Quote:
"Do 20 curves at B1=44M on 1*2^16384+1", and if the bold value is 0, it would do curves on 1*2^163841 ? What are the other values, being zero in this example? Last fiddled with by Andi47 on 20060319 at 14:31 

20060319, 14:33  #9  
Jul 2004
Potsdam, Germany
3×277 Posts 
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By the way: In certain circumstances, it could be better to also use gmpecm for stage1. This is especially the case when: 1. the remaining composite is much smaller than the original number and/or 2. the base is greater than 2. In such cases, you should do a speed comparison of stage1 before fully getting into the factorization of that number. Be aware that most numbers of the Cunningham Tables already sustained quite some factorization effort. I wouldn't start below the 45 digit range (> B1=11M). 

20060319, 14:39  #10  
Jul 2004
Potsdam, Germany
1477_{8} Posts 
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Last fiddled with by Mystwalker on 20060319 at 14:41 

20060319, 15:03  #11  
Oct 2004
Austria
7×353 Posts 
Quote:


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