20090329, 18:08  #12  
Jun 2003
Ottawa, Canada
2225_{8} Posts 
Quote:
Jeff. 

20090329, 20:24  #13 
(loop (#_fork))
Feb 2006
Cambridge, England
2·7·461 Posts 
I don't have a defpar.txt file, nor do I use the ggnfs scripts for large numbers. I have a couple of perl scripts, but they tend to have comments like 'now put the polynomial into count.gp and copy the results into this array'; not very fireandforget.
I start by picking the largeprime bound: I then try various smallprime bounds, and one or two sievers, and do test sieving over small ranges, estimate from those how long the job would take to get enough relations given the largeprime bound, and pick the smallprime bound and siever that gives the quickest runtime. I don't think you can avoid doing something at least that fiddly if you're working outside the bounds of experience. A rule of thumb which seems reasonable at least up to 140 digits is to pick the smallprime bound such that you can expect to get all your relations by sieving from spb/2 up to spb; small Q are at least slightly higheryielding than large Q. However, I'll post a few example points  I've tended to do individual verylarge jobs, I don't have a statistically significant collection of jobs above 130 digits. GNFS 120130 digits: 27bit large primes, siever 13e, small primes 6000000 works quite well for me towards the top end of the range, small primes 4000000 works OK towards the lower end. GNFS, 138 digits: probably 28bit large primes, 13e and 14e pretty comparable, small prime 10 million works for me By 150 digits you'll want 29bit large primes and siever 14e, small prime bound 20 million seems reasonable. Don't change over too early; 28bit LP was faster than 29bit LP at the 144digit point. I'm currently doing a 159digit GNFS with 29bit large primes and siever 15e, small prime bound 50 million. SNFS difficulty 180ish: 28bit large primes are better than 27bit; siever 13e; small prime bound around 10 million crossover 2829 is somewhere around 200; 30 is too big at difficulty 200. SNFS 210240: 30bit large primes, siever 14e, small prime bound somewhere around 30 million SNFS 240270: 31bit large primes, siever 15e, small prime bound around 100 million for larger numbers Not much above SNFS 270, you'll want to switch to siever 16e; but the current version of this horribly overestimates the memory usage (wants ~3.5G per process), and fixing that will be a serious development effort. Last fiddled with by fivemack on 20090329 at 20:39 
20090331, 03:40  #14 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
89×113 Posts 
I have added a small patch to the factMsieve.pl in the GGNFS repository. It is based on personal experience as well as collective experience of nearrepunit participants (which was modelfitted by M.Kamada).
The ten lines of perl code should extend defpar.txt virtually. Now that I've read Tom's comments, I am very glad that the perl hack agrees very much with his ideas. The SVN version is 344. 
20090331, 14:09  #15  
Jun 2003
Ottawa, Canada
3×17×23 Posts 
Quote:
You can download the latest factMsieve.pl here: http://ggnfs.svn.sourceforge.net/vie.../factMsieve.pl 

20090331, 17:16  #16 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
23511_{8} Posts 
Here is a reference to M.Kamada's statistics:
http://homepage2.nifty.com/m_kamada/...ions.htm#howto (the five graphs). The first thing for everyone to consider (regardless of parameters) is how much time one is willing to spend. See the first graph  expected time in CPU hours. If you don't have a 1000 CPUhours for a complete job, then please do not consider going above 205210 digits snfs (145 digits gnfs). The perl script will do better than before, but do keep in mind that there are certain factorizations that would still benefit from careful manual .poly file crafting (see Tom's message above for guidance); here's a short list that is not meant to be complete: 1. Quartics for larger numbers (when quartic is necessary): at the very least, switch the side to a and ponder uneven limits, 2. Sextics (converted quartics) for numbers with difficulty ~160190, same as #1, but lopsided to the other side. 3. All numbers above, say 200210: testsieving (deciding quintic vs. sextic, finetuning the limits, lambdas), custom scripts (that would avoid idle CPUs and not even try to filter before a certain number of relations), etc, etc... The script should behave better under 200210. 
20090401, 06:29  #17 
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
10057_{10} Posts 
"MINRELS.txt" file
Yet another hack: adding a file to the working directory called "MINRELS.txt". You can create/edit it while the perl script is already running. The script will read it before every filtering stage, so if you have got a good idea how many relations msieve's filtering "wants"  put that number in that file. If you later get a better idea  edit it!
You will save a ton of time from needless filtering; it also allows you to deliberately oversieve (for a smaller matrix). You need the 345 version of the http://ggnfs.svn.sourceforge.net/vie.../factMsieve.pl 
20090401, 16:41  #18  
Jun 2003
Ottawa, Canada
3×17×23 Posts 
Quote:
This way is much better because I can tweak things on the fly and not have to worry about editing the script itself. Good job! 

20090404, 16:32  #19  
Oct 2004
Austria
9B2_{16} Posts 
BEEP!
Quote:


20090404, 16:56  #20  
"Sander"
Oct 2002
52.345322,5.52471
29·41 Posts 
Quote:
Code:
# for($i = 0; $i < 5; $i++){sleep 1;print "\a";} 

20090404, 17:02  #21 
Nov 2008
4422_{8} Posts 
I would guess those beeps are there to alert you trhat the factorization has finished. It was quite useful when I had a job that took 4 dependencies and I was not in the room as I usually am.

20090404, 18:59  #22  
"Serge"
Mar 2008
Phi(4,2^7658614+1)/2
89·113 Posts 
Quote:
There's a lot of interesting "decorations" there, in the end of the script, including calling procrels (and only to gauge the speed of the computer; if it fails  never mind); the dmesg calls (btw, they also fail sometimes, not working as expected after the computer had been up for a while  the kernel ring buffer messages about the bogomips and CPUs get "ring"ed out.) 

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