20190131, 16:26  #1 
Mar 2016
59 Posts 
meta poly for Cxxx ?
I am working on C156,and at least two other C156 are in line (none of them are special form).
I am using yafu without Msieve (ini file below). Is it possible to use some existing poly dedicated for C156 (I.E. this one) and decrease sieve time instead of spending another ~35 CPUhours to find one. If not  how it will fail: at once, during sieve, atlinear, or (not this one please) in sqrt stage. If yes  how to create nfs.dat.p entry when values of norm,alpha and rroots are unknown; I would create nfs.job and nfs.fb myself but why the poly's in those files are different. Thanks in advance, cubaq PS. yafu.ini: B1ecm=11000 B1pm1=100000 B1pp1=20000 rhomax=1000 threads=8 pretest_ratio=0.25 %ggnfs_dir=D:\ggnfs\ ggnfs_dir=D:/ggnfs/ R=1 %ecm_path=..\GmpEcm\ecm.exe ecm_path=..\GmpEcm\ecm tune_info= Intel(R) Xeon(R) CPU E54650 0 @2.70GHz,LINUX64,1.73786e05,0.200412,0.400046,0.0987873,98.8355,2699.98 session.log (partial) 01/31/19 11:53:07 v1.34.5 @ WLODEKKOMPUTER,System/Build Info: Using GMPECM 6.3, Powered by GMP 5.1.1 cached 78498 primes. pmax = 999983 detected Intel(R) Core(TM) i72600 CPU @ 3.40GHz detected L1 = 32768 bytes, L2 = 8388608 bytes, CL = 64bytes measured cpu frequency ~= 3565.667100 using 20 random witnesses for RabinMiller PRP checks Last fiddled with by cubaq on 20190131 at 16:35 
20190131, 17:04  #2 
Apr 2010
Over the rainbow
3^{2}·281 Posts 
Unfortunately, poly are composite specific. So it will crash imediately.
As for finding a poly, you can ask for one in this thread https://mersenneforum.org/showthread.php?t=18368 The trouble is that it will take around 24H to get a 'decent' usable poly. As for how to create nfs.dat.p and the other file, I do not know. 
20190131, 17:46  #3 
"Curtis"
Feb 2005
Riverside, CA
2^{2}×3×389 Posts 
Pretest ratio of 0.25 is really low; for a C156 you ought to do at *minimum* a T45 worth of ECM. I'd do half a T50 before GNFS, personally. (Or maybe I misunderstand what pretest ratio is)
That's about a 6desktopcoreweek job to run through GNFS; spending 1.5 days on poly select is likely about right. If you get a score within 10% of the record poly score for that size, it's "good enough". If you don't have a GPU to use with msieve, the CADO tools produce very nice polys from CPU searches. Trying to use a poly from a different input will crash GNFS immediately with error "poly does not divide N!" or similar. 
20190201, 12:26  #4 
Mar 2016
59 Posts 
Thank You both for reply
@firejuggler: While using 'other' poly will crash, that knowlege seems to be pointless. @VBCurtis: Pretest ratio does not control upper limit of ECM stage. From the other hand, I am using ecm directly (yes up to ~T50 for C156). How do You measure that kind of percentage (i.e. i have e 1.952e012 for C156  is it good enough?). As far CADO I've just start to learn "How To …" so it'l take some weeks: do I really may ask for proper poly for C156,C157 on forum? Thanks once more, cubaq 
20190201, 15:25  #5 
Mar 2016
59_{10} Posts 
@firejuggler:
I am terrible sorry, I've just realize how that may be read. I ment the last sentence of Your reply. Sorry once more. cubaq. 
20190201, 16:34  #6  
"Curtis"
Feb 2005
Riverside, CA
2^{2}×3×389 Posts 
Quote:
The poly you've found would take roughly 25% longer to sieve than one with the score I've estimated (the ratio of the scores is roughly the inverse ratio of sieving times). It's worth spending a few days on poly select to save ~1.5 coreweeks of sieving! 

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