mersenneforum.org  

Go Back   mersenneforum.org > Factoring Projects > Factoring

Reply
 
Thread Tools
Old 2013-01-21, 19:41   #1
ryanp
 
ryanp's Avatar
 
Jun 2012
Boulder, CO

22·47 Posts
Default Advice for large SNFS jobs?

Hi all,

I'm working on factoring (2801^83-1)/2800 using a modified factmsieve.py -- and yes, I have a cluster available to me... :)

factmsieve tells me at the get-go:

Fri Jan 18 09:58:41 2013 -> Estimated minimum relations needed: 5.53168e+08

I'm able to make it up to about 200M relations with the default parameters (starting at rational q from 238450000, FAMAX = 476900000) before hitting GGNFS' limit: it can't handle special q >= 2^30 - 1.

Does anyone have any advice for what to do with jobs this big? Try to change the sieving window somehow? (And if so -- to what)?

Here's the polynomial I'm using:

Code:
n: 4784427753962229503583191777575386925462640502543527013793934480234680863804447852383959785408791045459809147067083157248015897910382151758867576620242257524246139326208569043470479714282260046673050230392057658284742406595942226610043596316622243579005395853667131475327572196568483
m: 1829715316371090533839726975772594414416841479201
deg: 6
skew: 0
type: snfs
c6: 1
c0: -2801
which gives the factor base:

Code:
N 4784427753962229503583191777575386925462640502543527013793934480234680863804447852383959785408791045459809147067083157248015897910382151758867576620242257524246139326208569043470479714282260046673050230392057658284742406595942226610043596316622243579005395853667131475327572196568483
SKEW 3.75      
A6 1
A0 -2801
R1 1
R0 -1829715316371090533839726975772594414416841479201
FAMAX 476900000
FRMAX 476900000
SALPMAX 4294967296
SRLPMAX 4294967296
ryanp is offline   Reply With Quote
Old 2013-01-21, 19:50   #2
fivemack
(loop (#_fork))
 
fivemack's Avatar
 
Feb 2006
Cambridge, England

18B216 Posts
Default

I'm impressed by the scale of your cluster, but factmsieve is not designed for jobs this big.

The polynomial is right, and the alim and lp look reasonable, but you're clearly using the wrong sieving binary since you're getting 0.25 relations per Q. I think you should be using 16e, and you should be using three large primes on the rational side (lpbr=32 mfbr=96 rlambda=3.6)

For things this large I tend to start from small Q (eg Q=1e7) rather than Q=Qmax/2.
fivemack is offline   Reply With Quote
Old 2013-01-21, 19:56   #3
debrouxl
 
debrouxl's Avatar
 
Sep 2009

11110100012 Posts
Default

What siever did factmsieve.py choose for such a job ? NFS@Home would probably choose ggnfs-lasieve4I16e, if not the corresponding lasieve5.
debrouxl is offline   Reply With Quote
Old 2013-01-21, 22:19   #4
ryanp
 
ryanp's Avatar
 
Jun 2012
Boulder, CO

22·47 Posts
Default

debrouxl: It's using gnfs-lasieve4I16e, as I expected.

fivemack: Thanks, I'll try starting with Q=1e7 and the mfbr/rlambda values you suggested... With those values, do you think there's a shot that GGNFS/msieve will be able to finish this thing? :)
ryanp is offline   Reply With Quote
Old 2013-01-21, 22:33   #5
henryzz
Just call me Henry
 
henryzz's Avatar
 
"David"
Sep 2007
Cambridge (GMT/BST)

22×1,433 Posts
Default

Quote:
Originally Posted by ryanp View Post
debrouxl: It's using gnfs-lasieve4I16e, as I expected.

fivemack: Thanks, I'll try starting with Q=1e7 and the mfbr/rlambda values you suggested... With those values, do you think there's a shot that GGNFS/msieve will be able to finish this thing? :)
Even if it doesn't assuming you are on linux you should be able to run the later version of the siever that will sieve higher Qs.
henryzz is offline   Reply With Quote
Old 2013-01-21, 22:58   #6
ryanp
 
ryanp's Avatar
 
Jun 2012
Boulder, CO

22·47 Posts
Default

Quote:
Originally Posted by henryzz View Post
Even if it doesn't assuming you are on linux you should be able to run the later version of the siever that will sieve higher Qs.
Is that in the latest released version of GGNFS, or the version from head in SVN?
ryanp is offline   Reply With Quote
Old 2013-01-22, 00:27   #7
henryzz
Just call me Henry
 
henryzz's Avatar
 
"David"
Sep 2007
Cambridge (GMT/BST)

22·1,433 Posts
Default

Here is a link to the newer siever. There shouldn't be much speed difference unless you can get ecm working helpfully.
http://mersenneforum.org/showpost.ph...8&postcount=15

I don't think the source is in the svn.
henryzz is offline   Reply With Quote
Old 2013-01-22, 01:11   #8
Batalov
 
Batalov's Avatar
 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2

23·7·163 Posts
Default

It's definitely been there for two years and is patched for many found problems. remdups is contrib/ directory.

I thought that the lasieve5 source was also there but it is not maintained; you'd have to figure everything for yourself. If it is not there, you can find a zip somewhere on this forum.
Batalov is offline   Reply With Quote
Old 2013-01-22, 07:34   #9
ryanp
 
ryanp's Avatar
 
Jun 2012
Boulder, CO

22×47 Posts
Default

Quote:
Originally Posted by henryzz View Post
Here is a link to the newer siever. There shouldn't be much speed difference unless you can get ecm working helpfully.
http://mersenneforum.org/showpost.ph...8&postcount=15

I don't think the source is in the svn.
Hmm, after downloading/untarring that version I still get:

Code:
./gnfs-lasieve4I16e -k -o spairs.out.test -v -n0 -r input.job.test
gnfs-lasieve4I16e (with asm64): L1_BITS=15, SVN $Revision: 399 $
Cannot handle special q >= 1073741823
Same with building from source (in the src/experimental/lasieve4_64 tree, using the instructions in INSTALL). Am I doing something wrong, or is there a newer version somewhere that can handle large q?
ryanp is offline   Reply With Quote
Old 2013-01-22, 07:36   #10
ryanp
 
ryanp's Avatar
 
Jun 2012
Boulder, CO

2748 Posts
Default

Erm, perhaps I missed this in INSTALL:

Code:
NOTE for Phenom/K8 users: replace in athlon64/ls-defs.asm
 define(l1_bits,15)dnl
=>
 define(l1_bits,16)dnl

and in athlon64/siever-config.h
#define L1_BITS 15
=>
#define L1_BITS 16
though that's not my CPU type... Is it still "safe"/advised?
ryanp is offline   Reply With Quote
Old 2013-01-22, 08:00   #11
Batalov
 
Batalov's Avatar
 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2

23·7·163 Posts
Default

No, this is only for the CPUs that have 64Kb L1 cache, i.e. AMD CPUs. (log264Kb = 16) Don't change L1 bits for Intel CPUs.

How much of the q area have you already sieved? What side have you sieved on? There's no need really for a project of this size to go over q>2^30. Try to cover the area from q=10^7 to your current lower limit (where you started, 238450000). Even if you go over 2^30, the yield will be less and less. You may get a better yield by repeating some of the most productive (lower q) areas with the parameters that Tom (fivemack) suggested earlier. Have you used 3LP? Like -
Code:
lpbr: 33
lpba: 33
mfba: 66
mfbr: 96
alambda: 2.55
rlambda: 3.7

Have you tried to filter your existing set of relations?
Last but not the least, do you have a computer (set of computers) to solve the resulting >40M matrix?
(As the saying goes, take no offense, - it's not the size (of the cluster), it's how you use it that matters. Have you done a snfs-~270-280 before doing this snfs-290?)

If you really want to go to very high q values, use the link to lasieve5 message.

Last fiddled with by Batalov on 2013-01-22 at 08:20
Batalov is offline   Reply With Quote
Reply

Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
29 to 30 bit large prime SNFS crossover VBCurtis Factoring 11 2015-03-09 07:01
How many jobs should I run? Warlord Software 12 2013-10-11 22:18
Advice for large GNFS jobs? WraithX Factoring 59 2013-07-30 01:13
doing large NFS jobs on Amazon EC2? ixfd64 Factoring 3 2012-06-06 08:27
Filtering on large NFS jobs, particularly 2^908+1 bdodson Factoring 20 2008-11-26 20:45

All times are UTC. The time now is 03:25.

Tue Oct 27 03:25:00 UTC 2020 up 47 days, 35 mins, 1 user, load averages: 2.52, 1.95, 1.72

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.