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 2017-05-16, 18:07 #1 BudgieJane     "Jane Sullivan" Jan 2011 Beckenham, UK 3528 Posts snfs for homogeneous cunninghams with a,b>12 Pardon my ignorance, but how can I persuade YAFU to run snfs on homogeneous Cunningham numbers where a and b can take any values (including >12) subject to the usual constraints? I assume this will require me to input my own polynomial, etc. Last fiddled with by BudgieJane on 2017-05-16 at 18:08
 2017-05-18, 12:41 #2 swellman     Jun 2012 2×5×7×41 Posts What number are you trying to factor? A recent example is discussed here http://www.mersenneforum.org/showthread.php?t=22317.
2017-05-18, 18:00   #3
BudgieJane

"Jane Sullivan"
Jan 2011
Beckenham, UK

2×32×13 Posts

Quote:
 Originally Posted by swellman What number are you trying to factor?
All numbers a^n ± b^n for 1≤b<a and n>1 and (a,b)=1, going on for ever.

Quote:
 Originally Posted by swellman A recent example is discussed here http://www.mersenneforum.org/showthread.php?t=22317.
Yes, I saw that.

What would be really nice is if snfs allowed "Homoeneous Cunninghams" to include values of a and b above 12, even though I have been reminded that those additional numbers are not really homogeneous Cunninghams.

 2017-05-19, 03:04 #4 bsquared     "Ben" Feb 2007 1100110111112 Posts The development version of yafu will find them up to a,b < 51. Code: nfs: commencing nfs on c101: 15067758128205500531528890729654007316625403247110194481701428976958933222260247689424312462463918293 nfs: searching for brent special forms... nfs: searching for homogeneous cunningham special forms... nfs: input divides 31^71 + 17^71 . . . gen: ======================================================== gen: selected polynomial: gen: ======================================================== n: 15067758128205500531528890729654007316625403247110194481701428976958933222260247689424312462463918293 # 31^71+17^71, difficulty: 107.38, anorm: 4.59e+025, rnorm: 6.48e+032 # scaled difficulty: 108.57, suggest sieving rational side # size = 2.260e-011, alpha = -0.092, combined = 1.530e-007, rroots = 0 type: snfs size: 107 skew: 1.1621 c4: 17 c0: 31 Y1: -14063084452067724991009 Y0: 699053619999045038539170241 m: 6031149606693380230432903286363238884791256368312046189530706734714464935231322816039209826333920537
 2017-05-19, 11:10 #5 BudgieJane     "Jane Sullivan" Jan 2011 Beckenham, UK EA16 Posts Ideally I'd like to do them up to a,b<1000.
 2017-05-19, 23:54 #6 BudgieJane     "Jane Sullivan" Jan 2011 Beckenham, UK 2×32×13 Posts I have just spent a very profitable day figuring out what I need to do to specify the polynomials for factoring an ± bn, and I've managed to run a nice 100-digit example to prove that it works. I'd like to thank those who have written various messages not just in this thread, but in several others (including "SNFS Polynomial selection help").

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