mersenneforum.org  

Go Back   mersenneforum.org > Factoring Projects > Msieve

Reply
 
Thread Tools
Old 2009-09-22, 16:00   #12
jasonp
Tribal Bullet
 
jasonp's Avatar
 
Oct 2004

3×52×47 Posts
Default

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?)
jasonp is offline   Reply With Quote
Old 2009-09-22, 16:32   #13
fivemack
(loop (#_fork))
 
fivemack's Avatar
 
Feb 2006
Cambridge, England

11000110100002 Posts
Default

Sorry: cut-and-paste error on my part. Omitting mfba and mfbr makes gnfs-lasieve4I1?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 2009-09-22 at 16:34
fivemack is offline   Reply With Quote
Old 2009-09-22, 19:46   #14
Raman
Noodles
 
Raman's Avatar
 
"Mr. Tuch"
Dec 2007
Chennai, India

100111010012 Posts
Default

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?
Raman is offline   Reply With Quote
Old 2009-09-22, 21:13   #15
fivemack
(loop (#_fork))
 
fivemack's Avatar
 
Feb 2006
Cambridge, England

24·397 Posts
Default

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.
fivemack is offline   Reply With Quote
Old 2009-09-23, 20:05   #16
jasonp
Tribal Bullet
 
jasonp's Avatar
 
Oct 2004

3×52×47 Posts
Default

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 100-200 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 2009-09-23 at 20:09
jasonp is offline   Reply With Quote
Old 2010-06-01, 05:11   #17
jrk
 
jrk's Avatar
 
May 2008

44716 Posts
Default

Quote:
Originally Posted by fivemack View Post
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
Quote:
Originally Posted by jasonp View Post
Note that only about 10% of the relations in the dataset had a large prime > 2^32, and each dependency only had 100-200 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.
I think that's because the lambda values are too low for finishing the large composites. If I understand correctly, the ggnfs siever will start rejecting composites larger than about fblim^lambda after sieving, which in this case is much smaller than the mfba,mfbr bits requested, so raising mfba,mfbr will probably do nothing. Using lambda values of about 3.2 or 3.4 with the other parameters unchanged will find many more relations and a bigger proportion of them will have factors >2^32, but it will of course be a lot slower too.
jrk is offline   Reply With Quote
Old 2010-06-01, 11:27   #18
fivemack
(loop (#_fork))
 
fivemack's Avatar
 
Feb 2006
Cambridge, England

24·397 Posts
Default

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 time-per-relation by a factor eight). I'm still seeing only two large primes per side, but many more relations with very large large-primes on both sides.

Last fiddled with by fivemack on 2010-06-01 at 11:30
fivemack is offline   Reply With Quote
Old 2010-06-01, 11:55   #19
Andi47
 
Andi47's Avatar
 
Oct 2004
Austria

248210 Posts
Default

Quote:
Originally Posted by fivemack View Post
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 time-per-relation by a factor eight). I'm still seeing only two large primes per side, but many more relations with very large large-primes on both sides.
Does it make sense to rise the lambdas for running projects like 2801^79-1 or alq4788.2529?
Andi47 is offline   Reply With Quote
Old 2010-06-01, 12:45   #20
fivemack
(loop (#_fork))
 
fivemack's Avatar
 
Feb 2006
Cambridge, England

24×397 Posts
Default

I don't think it makes a difference for current projects, because for 2801^79-1 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.
fivemack is offline   Reply With Quote
Old 2010-06-01, 13:46   #21
jasonp
Tribal Bullet
 
jasonp's Avatar
 
Oct 2004

3·52·47 Posts
Default

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.
jasonp is offline   Reply With Quote
Old 2010-06-01, 13:58   #22
fivemack
(loop (#_fork))
 
fivemack's Avatar
 
Feb 2006
Cambridge, England

18D016 Posts
Default

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 36-bit large primes; but this was a while ago, and I don't think I completed the job.
fivemack is offline   Reply With Quote
Reply

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Where do I send my PRP primes with large k? Trilo Riesel Prime Search 3 2013-08-20 00:32
lots of large primes Peter Hackman Factoring 2 2008-08-15 14:26
NFS with 5 and 6 large primes jasonp Factoring 4 2007-12-04 18:32
Why only three large primes fivemack Factoring 18 2007-05-10 12:14
What is the use of these large primes Prime Monster Lounge 34 2004-06-10 18:12

All times are UTC. The time now is 18:24.

Thu Jul 16 18:24:00 UTC 2020 up 113 days, 15:57, 2 users, load averages: 1.78, 1.42, 1.44

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, Jelsoft Enterprises Ltd.

This forum has received and complied with 0 (zero) government requests for information.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation.
A copy of the license is included in the FAQ.