mersenneforum.org What if we don't find twin prime n=333333?
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 2009-04-14, 11:45 #1 cipher     Feb 2007 211 Posts What if we don't find twin prime n=333333? What is the probability that we will find twin prime for n=333333 before 100G is up? What if we don't find a twin prime before 100G? do we start sieving 100G to 200G? or do we abandon n=333333 for a higher n=Value? Thanks
 2009-04-14, 14:20 #2 Svenie25     Aug 2008 Good old Germany 3×47 Posts Over at primegrid Lennart said, that they will stop LLR until the sieve is at 12P. I´ve seen for myself, that sieving needs atm ~45 seconds for one k and a LLRtest takes 2:40 minutes. I think that nobody expected, that we will need so long to find this little twin. One of the problems ist, that primes you find here (no twin) will not get into the top5000. And so not many people are interested. But on the other hand, in the last few days were more than 2 times more LLRtest were crunched at Primegrid. And for myself I would like to see the end of this project. There must be a twin! ;) Hopefully it is not to far in the future...
2009-04-15, 15:28   #3
MooooMoo
Apprentice Crank

Mar 2006

2·227 Posts

Quote:
 Originally Posted by cipher What is the probability that we will find twin prime for n=333333 before 100G is up? What if we don't find a twin prime before 100G? do we start sieving 100G to 200G? or do we abandon n=333333 for a higher n=Value? Thanks
The probability that we'll find a twin between now (60G) and 100G is about 60-65%.

There are no plans for sieving 100G-200G, so it looks like we'll abandon n=333333 for a higher n-value.

 2009-04-15, 15:35 #4 Svenie25     Aug 2008 Good old Germany 3·47 Posts Oh, doesn´t sound good. But we will see. I´m switching now back to sieving until at least sunday. should be the next n? n=666666? Last fiddled with by Svenie25 on 2009-04-15 at 15:43
 2009-04-16, 02:48 #5 geoff     Mar 2003 New Zealand 13·89 Posts It should be possible to make a program that sieves x different (carefully chosen) exponents at once at only a small extra cost in time (but requiring x times more memory). Minimising the number of 1 bits in the binary expansion of the exponent should also reduce sieve time (i.e. an exponent which is a power of two would be fastest). E.g. sieving n=2^19+1=524289 and n=2^19+2^18+1=786433 together should be almost as fast as sieving n=524289 alone.
 2009-04-16, 21:53 #6 Joshua2     Sep 2004 13·41 Posts A 64 bit sieve would be good too. But it would be good to have a n that finds top-5000 primes again.

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