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20180617, 11:58  #1 
Jun 2018
17 Posts 
In CUDALucas, do I have to wait until 100% completion before knwoing that my cadidate is composite?
I am running a CUDALucas Mersenne prime test since several months, and I am reaching the 20% mark. My candidate is purely random[1] (the prime exponent, that is), so I do not expect to find a new Mersenne prime. However, the fact that CUDALucas continues to compute for months without ruling out that it's composite makes me wonder:
 does CUDALucas need to reach 100% before giving a "verdict"?  should I entertain hopes that finding a prime has more probability, now that several months of computing have elapsed? _________________________ [1] i.e., it doesn't fulfill any of the criteria of the new Mersenne conjecture. 
20180617, 12:08  #2  
"Forget I exist"
Jul 2009
Dartmouth NS
2^{3}·3·5·71 Posts 
Quote:
Last fiddled with by science_man_88 on 20180617 at 12:35 

20180617, 13:52  #3 
Einyen
Dec 2003
Denmark
2^{7}·3^{3} Posts 
What graphic card are you running this on? How big is the exponent approximately?
It is not supposed to take many months, so either it is a very old card and/or you have chosen a way too large exponent. It might also be one of those graphic cards that is best used for trial factoring because double precision speed (needed for LL test) is 32 times slower than single precision speed (used for trial factoring). 
20180617, 14:00  #4  
Jun 2018
17 Posts 
Quote:


20180617, 15:25  #5 
Sep 2003
2×5×7×37 Posts 
Only the final result matters, and it is a yesorno result.
Zero means yes it's prime, and nonzero means no it's not prime. Any interim result (or the exact numerical value of a nonzero final result) is useful only for comparison purposes when it comes time for someone else to do a verification run, to doublecheck the accuracy of your test. If the two runs don't match then one or possibly both of them is wrong and further tests are needed. 
20180617, 15:36  #6 
"Forget I exist"
Jul 2009
Dartmouth NS
10000101001000_{2} Posts 
Is the exponent in the 25.92 billion range ?
Last fiddled with by science_man_88 on 20180617 at 15:36 
20180617, 16:39  #7 
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
8093_{10} Posts 

20180617, 16:55  #8 
"Forget I exist"
Jul 2009
Dartmouth NS
2^{3}·3·5·71 Posts 

20180617, 17:29  #9 
Jun 2018
17 Posts 
Iteration times are around 60 ms, and the PC is on 24/7. Note that I'm only using a home PC, nothing fancy with a GeForce GTX Ti 1050. My exponent isn't in't the billions range, as someone suggested. Instead, it's in the 100 million.

20180617, 18:45  #10  
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
8,093 Posts 
Quote:
a) yes b) only in the sense that it has not obviously crashed yet. Only the last LucasLehmer sequence output tells of primality status, the other iterations are necessary steps to reach it. Did you use good practice, fft benchmarking the card, in CUDALucas for the fft lengths of interest, threads benchmarking the card, run the residue selftest, run memory test over the whole card, run a couple of low double checks to verify it's working at differing fft lengths, before tackling a several months or some years' length assignment? Check out the exponent? Confirm that 64bit residues are changing from one status line to the next, and knownbad behavior not happening? What version CUDALucas is running? (V2.06 May 5 2017 beta?) 

20180617, 18:46  #11 
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
8,093 Posts 
CUDALucas won't run 25 billion or even 2 billion exponent; 1.143 billion max exponent, for 64M fft length max.
Last fiddled with by kriesel on 20180617 at 18:50 
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