20040908, 23:01  #1 
2^{2}·7·29 Posts 
Factoring  a few questions?
I was wondering about a couple of things 
Out of interest, how many 2627 million exponents have to be run before we expect a factor to be found  1 in 10 to 15? and how many bits is this most likely to be found in i.e. 2^67 because it has the most numbers? Also, if Primenet runs out of prefactored exponents, will it just go ahead and instruct clients to factor the numbers before LLing if 'run first time exponents' is selected? (and just factoring, not P1?) Should do anyway  in that case no probs. I was taking a look at Primenet and at the moment it seems that the LL wave is slowly gaining on the factoring wave (I can't be sure of the rate because it's hard to tell without manually checking over time myself)  but when factoring hits the magic 28.13 million (in about 6 months?) and the next tier 2^68 is needed this will slow tfing by about half and mean that the LL gains at double the closing speed. I know that on my factoring machine as it's not a P4 it is not an efficient use of its time to factor beyond 2^67 (because tfing is more efficient above 2^65 on a P4) and I'll probably have to move it onto something else. Hope someone can comment Thanks (Minty) 
20040909, 00:36  #2  
"Mark"
Feb 2003
Sydney
1075_{8} Posts 
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Other factors will moderate the impact, although I haven't quantified them. Leading up to 28M, TF will actually become slightly quicker, while LL testing always takes longer for larger exponents, and has also just passed a limit for a larger FFT size which will slow it down some more. And of course George can adjust the thresholds in new versions of the client for the default work it will ask for, to keep the three streams flowing. (We don't want doublechecking to fall further behind, do we!) If you do take that machine off TF, you could put it onto LMH... Hope this helps! 

20040909, 13:09  #3 
16420_{8} Posts 
Thanks very much for the speedy and informative reply  its really appreciated.
I don't know what the best alternative DC project is  GIMPS is rock solid and very understandable, so it's a favourite for me (SoB is a little less so and seems to have some client issues). I tend not to like science/bio projects because there's always politics in the background  i.e. DF is going down soon, and I don't think we'll ever find ET!. Crypto is pretty much dead as all the quick ones are gone (D.net's a 900 yr end and md5crk is gone too). Zetagrid will probably go down after January  there are plenty of Maths ones, but to find something a little special is hard for me. NFSNet looks OK  but requires some discipline and I'm not sure exactly what the achievements are, and Lucas is still down  will keep looking anyhow and in the meantime will factor on! Thanks again! Mints 
20040909, 13:26  #4  
Nov 2003
2^{2}×5×373 Posts 
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waste time factoring numbers with NFS that could more easily be done with ECM. See:http://webloria.loria.fr/~zimmerma/records/ecmnet.html and:http://www.mersenne.org/ecm.htm Or, if you want something OFFLINE, I could send my NFS code (source!) and you could help finish 2^667+ and 2^689+. Bob 

20040909, 22:52  #5 
2·4,703 Posts 
Thanks for the suggestions Bob  lots of helpful people on this forum :)
I think I'll give ECMNet a go when the new client is released, which is hopefully quite soon. (Fortunately I've got broadband so I'm on all the time!) I've always shied away from projects in the past where I've had to compile the source as I've no knowledge whatsoever on what to do in Windows (XP), and to make sure it's running efficiently on a particular architecture could be tricky for me! Hopefully the new client will come in .exe format (maybe even with athlon/P4 optimisations? or maybe they're not necessary). Anyway, I'll keep a lookout and see what comes along, All the best Minty 
20040910, 00:50  #6 
"Mark"
Apr 2003
Between here and the
2×5×631 Posts 
It will still be a couple of weeks before I release the new client. My beta testers have asked for a few changes, so I will be working on those and trying to get those tested.

20040910, 01:24  #7 
Mar 2003
New Zealand
485_{16} Posts 
I like the ECM factoring because the difficulty of finding a factor makes each discovery quite exciting, but the time between discoveries is not so long that I become discouraged.
I have been doing ECM for about six months on the base two Cunningham tables and in that time have found three factors of 43, 45, and 47 digits. I am using a Celeron 2.4, a P4 2.4, plus two old i586 class machines. Athlons are probably more efficient overall but there are some numbers in these tables where a P4 with Prime95 can be put to very good use. 
20040910, 11:55  #8  
Nov 2003
2^{2}×5×373 Posts 
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20040910, 17:41  #9  
Jul 2004
Potsdam, Germany
3×277 Posts 
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The achievements are the factorizations of several numbers with up to 212 digits so far: http://www.nfsnet.org/announcements.html The good thing is that the time to completion can be predicted well and it doesn't take more than at most some months to factor a number. Quote:
Personally, I like the ECM Server, e.g. used by ElevenSmooth. This way, ECM is completely automated. It uses gmp_ecm as well. Do you know a project that can try to ecm 24737*2^991+1? It's the last test of Seventeen or Bust with n < 1000 for which there is no known factor... 

20040910, 19:01  #10  
Nov 2003
7460_{10} Posts 
Quote:
/http://www.mersenne.org/ecm.htm Please report any ECM efforts you might make to George Woltman (you can email him from the GIMPS website). I know of no project to factor your suggested number; IMO there are already too many such projects. The Cunningham project has been going on for over 80 years. It is always easy to start up a project to factor some new set of numbers. One always makes easy early progress. But (IMO) the real pleasure comes from factoring a (set of) numbers that has withstood efforts for a long time. Such as finishing 2,n+ and 2,n to n=1200. 

20040911, 00:56  #11  
Dec 2003
Hopefully Near M48
2×3×293 Posts 
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Last fiddled with by jinydu on 20040911 at 00:59 

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