20090922, 16:00  #12 
Tribal Bullet
Oct 2004
6743_{8} Posts 
Was that the complete input file? I can't get any relations produced even when I fill in alim, lpb[ra], etc.
(I'm using the latest GGNFS source; can you tell I don't do lattice sieving often?) 
20090922, 16:32  #13 
(loop (#_fork))
Feb 2006
Cambridge, England
6454_{10} Posts 
Sorry: cutandpaste error on my part. Omitting mfba and mfbr makes gnfslasieve4I1?e use defaults which cause no relations to be found ...
Code:
n: 1248763129719355523107879850580906737073652359373784929661233741389327470271436463810348813 skew: 269019.30 Y0: 4938227649481593747717 Y1: 517398632491 c0: 871341534477377379017980 c1: 69959334784958737916 c2: 186442429493209 c3: 1091661800 c4: 2100 alim: 1000000 rlim: 1000000 lpba: 33 lpbr: 33 mfba: 66 mfbr: 66 alambda: 2.6 rlambda: 2.6 Last fiddled with by fivemack on 20090922 at 16:34 
20090922, 19:46  #14 
Noodles
"Mr. Tuch"
Dec 2007
Chennai, India
10011101001_{2} Posts 
Is this number 2,877 that is giving error on the square root phase with msieve upon using 33 bit large primes? Why does this number use up only an algebraic factor base limit of 1 million, and then that degree 4 polynomial only, within the file? If it is not so, what number it is so?

20090922, 21:13  #15 
(loop (#_fork))
Feb 2006
Cambridge, England
14466_{8} Posts 
This is a random C91 (index 1056 of aliquot sequence starting 560328); I have my own script for chasing aliquot sequences, it does GNFS when that's the right thing to do, and this means I have a load of GNFS polynomials for small numbers lying around.

20090923, 20:05  #16 
Tribal Bullet
Oct 2004
3^{2}×5×79 Posts 
Tom, we were both right; problem fixed in SVN 60.
Note that only about 10% of the relations in the dataset had a large prime > 2^32, and each dependency only had 100200 of those relations out of ~85000. It's possible you have to tweak mfb[ra] to be more than 2*lpb[ra] if you want lots of large primes near the specified bound. Last fiddled with by jasonp on 20090923 at 20:09 
20100601, 05:11  #17  
May 2008
447_{16} Posts 
Quote:
Quote:


20100601, 11:27  #18 
(loop (#_fork))
Feb 2006
Cambridge, England
2·7·461 Posts 
That's interesting. I hadn't tried making lambda that big because I'd done experiments that showed that 2.8 gave the same answer as 2.6, and I _thought_ that the restriction to two large primes meant that very large lambda values didn't make sense.
I had thought that the cutoff was 2^(lpba*lambda), not alim^lambda ! So in this case going from lambda=2.6 to lambda=3.5 is giving me three times as many relations per Q (admittedly at the price of slowing timeperrelation by a factor eight). I'm still seeing only two large primes per side, but many more relations with very large largeprimes on both sides. Last fiddled with by fivemack on 20100601 at 11:30 
20100601, 11:55  #19  
Oct 2004
Austria
9B2_{16} Posts 
Quote:


20100601, 12:45  #20 
(loop (#_fork))
Feb 2006
Cambridge, England
1100100110110_{2} Posts 
I don't think it makes a difference for current projects, because for 2801^791 we have alim=2^27, and 2.6 * 27 is already greater than mfba; for the aliquot job alim=2^26, and 2.6*26 is also large enough.
Whilst in this case alim=2^20, and 2.6*20 is substantially less than 66. 
20100601, 13:46  #21 
Tribal Bullet
Oct 2004
3^{2}×5×79 Posts 
For future reference, can the existing sievers find large primes larger than 2^33? There is a check to reject them, but is that the only thing stopping them from appearing in relations?
I ask because if I ever add MPI support to the LA then there may be a groundswell of support for doing a large job. 
20100601, 13:58  #22 
(loop (#_fork))
Feb 2006
Cambridge, England
2·7·461 Posts 
I checked that all the calculations were being done in mpz_t rather than in unsigned long, removed the check, and managed to do some sieving with 36bit large primes; but this was a while ago, and I don't think I completed the job.

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