20130428, 07:56  #1 
Feb 2013
7 Posts 
Best way to scale polynomial selection
If I want to scale polynomial selection (over multiple cores / computers) is the best way to have each CPU check a different range of coefficients (like below):
./msieve v s test1 l test1 nf test1 np "min_coeff=0 max_coeff=1000" m 18482358805813848044952912904056328155022481776091991120664052047908519720614998988214854943918675611393700936203073 Currently I'm doing it this way and it seems to work, is there a better way I should be doing it? Thanks :) P. 
20130428, 09:03  #2 
(loop (#_fork))
Feb 2006
Cambridge, England
13·491 Posts 
That's how I do it, though it's worth remembering that small leadingcoefficients complete much more slowly than large ones (it's about proportional to 1/sqrt(C5), but not precisely). I never managed to split it up statically in a way I was happy with, so I tend to use a makefile distributing lots of 1k ranges to the set of available cores.

20130428, 11:56  #3  
Bamboozled!
"πΊππ·π·π"
May 2003
Down not across
11×971 Posts 
Quote:


20130428, 13:30  #4 
Sep 2009
977 Posts 
There's a patch for MPI polynomial selection with msieve

20130507, 10:58  #5 
Feb 2013
7 Posts 
Thanks for the replies :) they've been a great help.
I'm now trying to scale ggnfs sieving up  I've noticed that factmsieve.py starts sieving at q=13550000 e.g. the output shows making sieve job for q = 13550000 in 13550000 .. 13562500 as file ./outputf.m.job.T0 Is there any particular reason for this? wouldn't it be just as good to start at q = 0? or is this an effort to get each block to process in a similar time frame? Thanks P. 
20130507, 20:37  #6 
Sep 2009
1111010001_{2} Posts 
Did you get around to polishing the scripts you mentioned at http://www.mersenneforum.org/showthread.php?t=17847 ? Or maybe this is still part of the feature / polishing work
Starting at overly low q values tends to produce higher duplicate rates, which will be filtered later anyway. Therefore, "low" q values are not much (if at all) more productive than higher q values. 
20130508, 09:01  #7 
Feb 2013
7 Posts 
I sure did :) I got distracted by another project for a while but i'm now back working on it  I've built a light weight standalone python + sqlite3 job server and a client that can be started on Amazon EC2 spot instances.
Polynomial selection is working pretty well  for a recent C155 I found a polynomial with a score of 3.212e12 in < 1 hr (If anyone needs help finding a good polynomial quickly let me know) I'm going to work on the sieving distribution this weekend  now the server + client is written it shouldn't require too much work to finish off. Once I'm happy with it i'll make the code and a fully configured Amazon AMI available. One of the issues I've had is getting ggnfs to compile properly on 64 bit linux. I've ended up using some precompiled binaries I found online  I could get it to compile but it just kept giving me a Error 11 when it was doing some of the sieving :S 
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