Sophie Germains, multiple nranges, future of TPS
This thread is for discussing a possible search for Sophies and searching a range of both n and k for twins.
Recently, a couple of people have asked me about doing a search for both sophies and twins for n=500K. Doing so means that there's a greater chance of finding either a sophie or a twin, but one problem is that the chance of finding a twin in a range decreases the higher you sieve. As a guide, there are about 500,000 candidates left after triplesieving a range of 10G to p=1T. Continuing to p=1000T with a twinsieve would leave 320,000 candidates remaining, while continuing to p=1000T with a triplesieve would leave only 256,000 candidates remaining. Some of those candidates eliminated with a triple sieve but not eliminated with a twin sieve may have been twins. Another suggested idea came up in this rather long thread: [url]http://www.mersenneforum.org/showthread.php?t=8479[/url] It was suggested that TPS search for a range of n with a smaller k range instead of searching a large krange with a fixed n. The advantage is that the low kcandidates in a variable nrange are faster to test than those with a fixed n, while a disadvantage is that sieving won't be as efficient. If you want TPS to also look for sophies, I'd welcome suggestions for a suitable krange for triple sieving n=500K. For those who want to try triplesieving a test range to get the idea of how it works and how much time and RAM is required, download David Underbakke's Twingen software at: [url]http://www.sendspace.com/file/261wdk[/url] 
[quote=MooooMoo;145219]This thread is for discussing a possible search for Sophies and searching a range of both n and k for twins.
Recently, a couple of people have asked me about doing a search for both sophies and twins for n=500K. Doing so means that there's a greater chance of finding either a sophie or a twin, but one problem is that the chance of finding a twin in a range decreases the higher you sieve. As a guide, there are about 500,000 candidates left after triplesieving a range of 10G to p=1T. Continuing to p=1000T with a twinsieve would leave 320,000 candidates remaining, while continuing to p=1000T with a triplesieve would leave only 256,000 candidates remaining. Some of those candidates eliminated with a triple sieve but not eliminated with a twin sieve may have been twins. Another suggested idea came up in this rather long thread: [URL]http://www.mersenneforum.org/showthread.php?t=8479[/URL] It was suggested that TPS search for a range of n with a smaller k range instead of searching a large krange with a fixed n. The advantage is that the low kcandidates in a variable nrange are faster to test than those with a fixed n, while a disadvantage is that sieving won't be as efficient. If you want TPS to also look for sophies, I'd welcome suggestions for a suitable krange for triple sieving n=500K. For those who want to try triplesieving a test range to get the idea of how it works and how much time and RAM is required, download David Underbakke's Twingen software at: [URL]http://www.sendspace.com/file/261wdk[/URL][/quote]I for one am highly in favor of the smaller krange, variable nrange idea, and would be sure to find some CPU time to throw on it if TPS chooses to go that route. :smile: (Anyway, just my $0.02. I know I haven't really contributed much to this project besides a bunch of PrimeGrid TPS WU's a while back, so I guess my vote may not count as much as others'. :smile:) 
I actually like the idea of doing multiple n small k range just above n=195000. I would like to see the feasablity of doing this. Can it be adapted to primegrid somehow? Assuming n=333333 stalls out or something, there might be interest in the possibility of a record with the smaller n's. I personally have lost any real interest in n=333333. I get htis feeling of 'going to take forever' to find the twin.
Again, I'd like to see a much larger prime, but with a lower n value, we could do a lot of work in less time to check feasablity for going higher. Thoughts? 
To save repitition of work, I have searched for twins from n=195,032 to 201,700(ish), k from 1003 to 124751. (I think I missed two ranges of n of size 8.)
I found about 150 Riesels but no twins. (Obviously!) It took about 3 months of all 4 C2Q cores at 3.18GHz, including sieving. I am no longer searching below top5000 level. 
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[QUOTE=Skligmund;147102]I actually like the idea of doing multiple n small k range just above n=195000. I would like to see the feasablity of doing this. Can it be adapted to primegrid somehow? Assuming n=333333 stalls out or something, there might be interest in the possibility of a record with the smaller n's. I personally have lost any real interest in n=333333. I get htis feeling of 'going to take forever' to find the twin.
Again, I'd like to see a much larger prime, but with a lower n value, we could do a lot of work in less time to check feasablity for going higher. Thoughts?[/QUOTE] I've posted a sieve file for you since you were interested in doing a multiple n, small k range. It tests n=197000197009 from k=11M. It should be slightly faster to test than n=195000 because of the small k's. The sieve file hasn't been sieved deeply (only to p=250G) because each n must be sieved separately and because the k range is so small. At p=250G, 1 k is eliminated every 3040 seconds, while it takes slightly less than a minute to LLR them. This search for twins a bit above n=195000 might be adapted to Primegrid, but I'll wait until n=333333 is done first. Note: The file now excludes all k below 124,000 since Flatlander LLR'ed it already. 
Alright. I'll download that as soon as I get home and play with it. Thanks!

Hello,
is prping of 197000197009.txt complete ? primes known ? I will try to find fast any primes with my selection methode. best[U][/U][URL="http://www.mersenneforum.org/attachment.php?attachmentid=2875&d=1225314621"] [/URL] 
[quote=Cybertronic;147937]
I will try to find fast any primes with my selection methode. [/quote] Hm, it works fine . The first prime "987975*2^1970021 is prime!" 
No joke , I select n=200065 , sieved with Newpgen all k's from 125000 to 1M 3 minutes and start my 4 tasks. After 2 minutes I found
"830535*2^2000651 is prime! Time : 86.763 sec." I wonder how easy it is to find so large primes :) 
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