20100815, 20:59  #1 
Jun 2010
2·127 Posts 
Two sieving questions
1.) What's the optimal sieve depth, and how is it calculated? I'm assuming the LLR part of the project goes like this:
A.) Test k<100K for n=480K495K. If a twin is found, work on "Operation Megabit Twin". If not, go to step B. B.) Test 100K<k<1M for n=480495K. If a twin is found, work on "Operation Megabit Twin". If not, go to step C. C.) Test 1M<k<10M. If a twin is found, work on "Operation Megabit Twin". If not, repeat the same process for n=495K500K. Would it be a good idea to stop sieving now until the project is done with k<1M? At p=550T, it takes 56 minutes to find a k<1M factor on one core, but only four and a half minutes to finish an LLR test. 2.) How much efficiency is lost by breaking up the 480K495K range into three separate ranges? Shouldn't they be merged into one 480K495K file? 
20100815, 23:27  #2  
A Sunny Moo
Aug 2007
USA (GMT5)
3×2,083 Posts 
Quote:
Quote:
Note that this assumes that the entire file (k<10M) will eventually be used. I'm not sure how we're going to do that, whether we'll test the whole range or stop after the first twin. It really is most efficient to go and test the whole file (as otherwise we'd be potentially wasting quite a bit of sieve work), but usually the popular opinion is for the next twin to be significantly bigger than the last (not just marginally so as it would be from later in the same range). Quote:
Last fiddled with by mdettweiler on 20100815 at 23:29 

20100816, 06:28  #3  
May 2010
499 Posts 
Quote:
If I were to use all cores of that same machine for LLR instead, I'd be completing tests at a rate of 6566 seconds per test. When you take other things into account (duplicate factors, factors for candidates which have already been LLR tested, and computers which are better in LLRing than at sieving), you'll find that 6P is more or less the optimal sieve depth. 

20110413, 23:46  #4  
"Lennart"
Jun 2007
2140_{8} Posts 
Quote:
When I sieve on my GPU I get 227 f/hr Thats 3600/227 = 15.9 sec If you merge two files to 480k490k You will do it faster. Lennart EDIT I forgot to say this was on 6P6002T Last fiddled with by Lennart on 20110413 at 23:50 

20130424, 01:37  #5 
Apr 2013
1_{16} Posts 
Question re Prime Spiral Sieve Spin on Twin Primes
I'm wondering if the way I've presented the factorization of twin primes is even remotely useful to any of you ... http://www.primesdemystified.com/twinprimes ... accepting that this is from the perspective of a crackpot arithmetician sticking his neck out to ask a sincere question of bonafide mathematicians and programmers(?)

20181219, 18:38  #6 
Jun 2009
13×53 Posts 
Talking about sieving  I tried to run tpsievecuda on a recent and powerful GPU. But it appears to be looking for some libcudart library that is way outdated and nowhere to be found on the system. Does anybody know how to get it to run on a modern system?

20181220, 07:32  #7 
Romulan Interpreter
Jun 2011
Thailand
23064_{8} Posts 
can you post lib name? there are lots of old cuda libs here somewhere, we may be able to find it for you...

20181221, 10:12  #8 
Just call me Henry
"David"
Sep 2007
Cambridge (GMT/BST)
13440_{8} Posts 
If the binaries are ancient then you are probably better off recompiling as it will then be optimised for your modern gpu this might give you a nice speed boost(or not).

20181225, 17:57  #9 
Jun 2009
1010110001_{2} Posts 
It's looking for libcudart.so.2 but I don't know where it's trying to find that file.
Is the source available? Trying to compile might be a good idea. Last fiddled with by PuzzlePeter on 20181225 at 17:57 
20181227, 10:02  #10 
Romulan Interpreter
Jun 2011
Thailand
2^{2}×3×5×163 Posts 

20190704, 18:26  #11 
Jun 2009
2B1_{16} Posts 
I had a look at the source, but that's not what I am very good at. I learned it is "built from the ppsieve package" but I am at a loss at how to get a tpsieve from that?
I had a hard time tweaking polysieve which is only a single file of code and a short one also. These multifile builds just go over my head. It clearly shows I never really learned to write software. 
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