20170517, 21:20  #1 
Aug 2004
New Zealand
341_{8} Posts 
SNFS of C112 cofactor of 608^60+480^76
I've been trying to complete 608^60+480^76 by SNFS using yafu. I first took out the obvious 2^300, then generated a degree 5 polynomial from (19^12)^5+15(2^16 * 5^75)^5. There is also a small factor 193. My input looks like:
Code:
n: 1512787865815604665168125992005458173124947471321097315052908880093889444629900995273034048975712989271411140657 m: 938653510572529699833798948683334366050403278236720135828886826556700342961769485489321955075594682751310365305 deg: 5 skew: 1.718 type: snfs c5: 1 c0: 15 Y0: 2213314919066161 Y1: 28697814000000000000000 rlim: 588500 alim: 588500 lpbr: 25 lpba: 25 mfbr: 47 mfba: 47 rlambda: 2.3 alambda: 2.3 Code:
Wed May 17 20:14:24 2017 error 11 reading relation 0 Wed May 17 20:14:24 2017 error 11 reading relation 1 Wed May 17 20:14:24 2017 error 11 reading relation 2 ... 
20170517, 21:42  #2  
Sep 2008
Kansas
2^{3}×431 Posts 
Quote:
It appears you forgot the 3^75. Edit: Actually it should be 3^15 * 5^15 if raised to the fifth power. Last fiddled with by RichD on 20170517 at 21:44 

20170517, 21:47  #3  
Aug 2004
New Zealand
3^{2}·5^{2} Posts 
Quote:
2^16*15^15 = 28697814000000000000000. So although my formula in explanation was wrong, I think I have the correct value in my polynomial. 

20170517, 21:50  #4 
Sep 2008
Kansas
2^{3}·431 Posts 
After further review, I think it should be 2^30 * 15^15.
Edit: Never mind. I can't do math. You are correct. Last fiddled with by RichD on 20170517 at 22:03 
20170517, 22:07  #5 
Aug 2004
New Zealand
3^{2}·5^{2} Posts 
Thanks for your time looking at this, but 2^30 * 15^15 doesn't work: not a common root of the polynomial.
How did you get 2^30? I'm seeing it like this 480^76 = 2^(5*76) * 3^76 * 5^76. Then remove 2^300, to get 2^80*3^76*5^76 = 15*(2^16*15^15)^5. 
20170517, 23:10  #6 
Jun 2012
3203_{10} Posts 
You could let Yafu choose the poly automatically, for comparison purposes. It will almost certainly choose the same poly as you but adds parameters etc as required by yafu for sieving. Maybe something will show up that is missing, like "size:" (I don't think yafu requires that parameter but I'm not sure). It is missing from your nfs.job file.
Code:
nfs(1512787865815604665168125992005458173124947471321097315052908880093889444629900995273034048975712989271411140657) v 
20170517, 23:22  #7  
Aug 2004
New Zealand
225_{10} Posts 
Quote:
I've done a bunch of somewhat similar cases without problem, but there must be something unusual or special about this one or some error I've made in my polynomials. I have yafu, v1.34.5. 

20170517, 23:41  #8 
Sep 2008
Kansas
2^{3}×431 Posts 
I removed the parameters and ran the poly through factMsieve and it factored it into p44 * p68. factMsieve used similar parameters so nothing wrong with the poly.
If you want the solution I can post to FDB but I'm sure you want to Last fiddled with by RichD on 20170517 at 23:48 Reason: clarification 
20170517, 23:43  #9 
Jun 2012
3,203 Posts 
Yeah I guess your composite is not derived from the forms yafu checks during SNFS poly selection, so it defaults to GNFS.
Well if your poly was incorrect yafu would quickly crash. Since that is not happening, the poly works. The only thing missing is a line size: 200 (or whatever the difficulty is for this composite). Try adding the size? Also, you don't need deg: 5. Yafu probably ignores it, but maybe it's causing problems? ETA: the recent ggnfs sievers sometimes act strangely for me when I do small jobs like this. Maybe try with an older version of ggnfs? Last fiddled with by swellman on 20170517 at 23:46 
20170518, 01:34  #10  
Aug 2004
New Zealand
3^{2}·5^{2} Posts 
Quote:
I tried various other things around the job file for yafu, including the suggestions of swellman, but I still couldn't get it to work  and I'm sick of trying various combinations now. Since both are pointing at the same underlying siever, I can only assume it must be some issue with the filtering in yafu. I've actually found a second case where yafu does the same thing, so I will try doing that one with factMsieve as well. 

20170518, 02:15  #11 
Jun 2012
3,203 Posts 
This is a puzzling bug. I'll try to duplicate it tomorrow once I'm back in front of a computer.
I've got a bunch of computers with different versions of yafu, giving a nice cross section of environments. Maybe something will turn up. Have you tried compiling the dev branch of yafu discussed here? Apparently a lot of bugs fixed, maybe this one too? Last fiddled with by swellman on 20170518 at 02:15 
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