20070128, 03:34  #1 
Jul 2003
wear a mask
1553_{10} Posts 
feature request
Currently, srsieve breaks up our sequences of interest into many subsequences. With one of the commandline options on srfile, the exponent sequence is displayed. Would it be possible to add a commandline option that would print the exponent forms for the subsequences AND counts for that sequence?
What I'm thinking is that if there are some extremely lowweight subsequences it might be possible to get rid of those subsequences (by testing or P1 factoring) and thus speed up the overall project sieve. 
20070131, 05:08  #2  
Mar 2003
New Zealand
13×89 Posts 
Quote:
srfile c X input.txt to get the length of each modulo X subsequence in input.txt. X should be the value that the sieve reports in `split S base B sequences into T base B^X subsequences'. 

20070131, 09:35  #3 
Jan 2005
479 Posts 
If I understand it correctly, you will try to eliminate the 243 values of n in
204394*5^n1: n = 16*m+11, 7509 terms with n = 51 (mod 60): 243 terms to eliminate the n=51 case of 204394, which is about 1/1800th of the total of cases? If I understand this correctly, it will only very marginally speed things up However, I might be terribly wrong 
20070131, 14:54  #4 
Jul 2003
wear a mask
1,553 Posts 
I was expecting the minimum sequence to be a little smaller. I thought that if there were several subsequences with less than about 50 n remaining, we could test out those subsequences and see a boost.
Actually it might be fun anyway to test out some of the lowest weighted subsequences... get some timing results for PRP tests at n = 2 million, speed up the overall sieve marginally... 
20070131, 15:04  #5 
Jan 2005
479 Posts 
I'm in for a little challenge... is there a way to create a list of those numbers?
(204394*5^n1: n = 16*m+11 with n = 51 (mod 60): 243 terms)? 
20070131, 15:07  #6 
Jul 2003
wear a mask
1,553 Posts 
You could do it with Excel or Gnumeric (on linux)... it's a little bit of work that way. Maybe Geoff has a trick he knows of...

20070131, 16:59  #7 
Oct 2006
7·37 Posts 
don't forget that PRP don't remove k/n pair from the sieve file ... the sieve file contain a lot of allready prp'ed value.
so if you want to remove a subsequence, you have to find factors. but factors are comming very slow: for exemple i sieved my k (285728) up to 15000 *10^9 (15T i think) and now i find 2 factors every day (amd x24200, one core sieving) and there is only 5 subsequences. PRP give exactly the same rate (2 test a day per core, at n= 740000) one possible attack is p1 factoring of the lowest weighted sequence. i know that some people love p1 factoring. but first we need to know the top 10 of the "lowest weighted subsequence" 
20070131, 18:17  #8 
Jan 2005
111011111_{2} Posts 
I think we would remove them if they are doublechecked prp.
And 2 tests per day isn't too bad, since we 'only' need to do some 250 of them (if no factors are found). (say that around 2M it will take 2 days per test, still doable) 
20070131, 20:18  #9  
Oct 2006
7·37 Posts 
Quote:
and yes 250 test is doable 

20070201, 10:55  #10 
Jan 2005
479 Posts 
Those number which were prp'd once were left in only to accomodate the doublechecking effort. (otherwise we would need to do the sieving once again).
Also, when sieving now eliminates a prp'd value, it will thereby eliminate the need for a doublecheck. All of these that have been doublechecked can be removed, but this has not been done, since it only marginally speeds up the sieving process. Hmm... upto 60k doublechecked... that is now 3%... More then marginally now, maybe we should delete them now. 
20070201, 22:32  #11 
Jan 2005
479 Posts 
First result:
204394*5^2022511 has a factor: 159148635697417 (I am running ECM with B1=1000 and B2=100000 10 curves and P1 with B1=10000 and B2=100000 on every number (which have not been prp'd yet)) If those parameters are way off, let me know please :> Last fiddled with by michaf on 20070201 at 22:34 
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