20110715, 02:12  #1 
Jul 2011
2×3 Posts 
SNFS Polynomial selection help?
I am having trouble with writing an SNFS polynomial of the form
(381*(3^381)1)/(2*37*4223). Is it feasable to write a SNFS polynomial, or would GNFS be better? Matt Hill 
20110715, 02:52  #2 
"Bob Silverman"
Nov 2003
North of Boston
2^{3}×937 Posts 

20110715, 03:51  #3 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
2×3^{3}×5×37 Posts 
Try something like:
Code:
n: 70660119042903854046516409844370038935302985028064659122643072861070853843136559153244087740059607644464606489303319089200206965812929296697868636129615795714605815617265147516321 c5: 127 c0: 27 Y1: 1 Y0: 5474401089420219382077155933569751763 type: snfs skew: 0.73 Last fiddled with by Batalov on 20110715 at 04:03 
20110715, 04:55  #4 
Mar 2007
Germany
2^{3}×3×11 Posts 
You can try the snfs poly generator (experiment) from this site http://factorization.ath.cx/index.php
This option is new from Syd  more Informations here http://www.mersenneforum.org/showpos...postcount=1128 
20110715, 11:15  #5 
Jul 2011
2·3 Posts 
Thanks guys.
I am new to SNFS, so I was playing around with the polys. I won't get around to running it for a day or so, until my gnfs C134 finishes. The link is useful too, as I was unsure about where to set the other factors of the search (rlim, alim, etc.) Matt Last fiddled with by mhill12 on 20110715 at 11:24 
20110715, 12:21  #6 
Jul 2011
6_{8} Posts 
Are there any default guesses for skews, for a deg. 4, 5, and 6 poly of this type? I plan on doing some pretesting first, but I would like to know what skew values are good guesses for the degrees. I plan on testing each poly I have, then narrowing in on the right skew value.

20110715, 15:09  #7  
"Bob Silverman"
Nov 2003
North of Boston
2^{3}·937 Posts 
Quote:
Computing the skew is easy. No need to guess. Let the polynomial be a_n x^n + .... + a_0. Set the skew to (a_0/a_n)^1/n [or its reciprocal depending on how the code uses it] 

20120926, 03:23  #8  
Basketry That Evening!
"Bunslow the Bold"
Jun 2011
40<A<43 89<O<88
3×29×83 Posts 
Quote:
Quote:
Last fiddled with by Dubslow on 20120926 at 03:30 

20120926, 03:44  #9 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
2·3^{3}·5·37 Posts 
Thank you, Capt. Obvious!

20120926, 03:51  #10 
Basketry That Evening!
"Bunslow the Bold"
Jun 2011
40<A<43 89<O<88
3×29×83 Posts 
I'm Mjr. learnedhowtodothisafewhoursago, and Cnl. wantstobesurehisintuitioniscorrecttopreventfuturefsckups. (Note this is the "help" thread. Thanks for helping, I suppose.)
Last fiddled with by Dubslow on 20120926 at 03:52 
20120926, 05:24  #11 
Sep 2008
Kansas
2×3^{2}×11×19 Posts 
Should we also revisit the powerhalving technique?
(I'm partly serious about this question for the newbies.) 
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