20120409, 18:36  #12 
Jun 2009
1253_{8} Posts 
Luigi,
how many candidates do you start with? I'd like to do at least 1e11 k values at a time, but using fermfact the files are way too large. Peter 
20120409, 19:16  #13 
Just call me Henry
"David"
Sep 2007
Cambridge (GMT/BST)
2×29×101 Posts 
I wonder how difficult it would be to add a switch in srsieve that removes all the correct candidates for quads when a factor is found.

20120409, 19:23  #14 
Jun 2003
7·19·37 Posts 
I have adapted my LuckyMinus code to sieve for quadruples [k*2^n1,+1,+5,+7]. Attached is the source code in Pascal. You'll need freepascal or another pascal compiler to compile the code. If needed, I can post a windows executable. More thorough testing needs to be done. Once the initial sieving is done by the program, you can use NewPGen to take it to higher depths.

20120409, 19:46  #15  
Jun 2009
683 Posts 
Quote:
EDIT: A windows executable (32 bit) would be very much appreciated. EDIT2: *lol* Of course I couldn't resist. I downloaded freepascal and it compiled nicely ( so no need for a windows executable). Now it's running and I am very curious about timings... Last fiddled with by PuzzlePeter on 20120409 at 19:58 

20120410, 09:03  #16  
Banned
"Luigi"
Aug 2002
Team Italia
2^{2}·3·401 Posts 
Quote:
I usually handle files of tehths of Megabytes (my last work was on N=61000 to 70000, and k=20000 to 30000), that's like starting with about 2.5*10^18 values, that become 3*10^6 after a few seconds of sieving. Keep in mind that FermFact is best used with N > 10000 and "squared areas", that is about the same number of Ns and ks... Luigi 

20120410, 16:40  #17 
"Sander"
Oct 2002
52.345322,5.52471
29·41 Posts 
How about running newpgen to 10/50/100M. It will still split the files but won't sieve that long. After that, manually combine the sieve files and start newpgen where you left off?

20120410, 21:55  #18 
Jun 2009
683 Posts 
I'm doing singlen searches with lots of k values, meaning 1e13 k's and more. Even when split and sieved to p=1G with NewPGen the resulting file is 1+ GB sieved for quadruples, many times that when only sieved for twins or, even worse, sierpinski primes.
I tried using NewPGen and make it sieve to only 100M and it really does speed up the process by 50% while the files get about twice as large which seems to be a good compromise. So without axn's help this would probably be the way to go. Now I don't have exact exact timings for axn's code yet, but first tests seem to hint at a 90% reduction in time for a 1T range sieved to p=1G. I don't yet know how it copes with bigger ranges. I'll keep you updated. Speaking of the code, when I want to use it to sieve for triplets, I think this part Code:
{ c = +7 ==> x = [7*t+k] } x := t*2; if(x >= n) then x := x  n; {2t} x := x+t; if(x >= n) then x := x  n; {3t} x := x*2; if(x >= n) then x := x  n; {6t} x := x+t; if(x >= n) then x := x  n; {7t} x := x+k; if(x >= n) then x := x  n; {7t+k} if(x > 0) then x := nx; {  } ndx[i, 4] := x; Thanks again to everybody who's trying to help. Peter Last fiddled with by PuzzlePeter on 20120410 at 21:55 
20120410, 22:18  #19  
Jun 2003
7·19·37 Posts 
Quote:


20120411, 02:26  #20 
Jun 2003
7×19×37 Posts 
That went faster than expected. Here's the triple version. I've modified it to accept the k range in G rather than T. It's probably between 2x and 3x faster than NewPGen.

20120411, 14:57  #21 
Jun 2009
683 Posts 
Thanks for making the triple version! I knew there would be some hidden subtleties to modify... T ranges would have been ok as any triple large enough to make Chris Caldwells TOP20 needs a search space of several T's except you're very lucky. But that's not important and I can change this myself.
As for the quad, I did a 1T range with both your code and NewPGen. The files matched perfectly and my 10fold speedup estimate (based on the first few minutes) turned out to be quite accurate. Great work! I'll play around with different sievesize settings and then test the triple version. Thanks again! Peter 
20120414, 06:39  #22 
Jun 2009
683 Posts 
Wow, switching to a 12core machine I can do 600T for quads in less than 4 days. Chunks of 50T (resulting in 2GB files each) is about the max that NewPGen is able to digest. This is great!
I see a slowdown when running on several cores at once. It's probably due to having Sievesize>L2Cache which was fastest on 1 core. I'll try if Sievesize<L2Cache is better for using all cores. 
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