20190222, 17:18  #12 
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
2^{2}×3×7×53 Posts 
V2.06 May 5 2017 beta of CUDALucas, to be exact; it has a bit more error detection in it than the April 18 2017 beta, which has more than 2.05. It's pretty solid; see https://www.mersenneforum.org/showpo...82&postcount=4
https://www.mersenneforum.org/showpo...83&postcount=8 https://www.mersenneforum.org/showpo...24&postcount=3 https://www.mersenneforum.org/showpo...19&postcount=4 
20190222, 17:25  #13 
Sep 2003
2^{2}·3·5·43 Posts 
The characteristic error of CUDALucas is sometimes zeroing out the residue, so then it stays zeroed until the end.
But there are three machines that I mentioned with a very high error rate, returning nonzero residues. Maybe those are running mprime and there's a hardware problem. You should look into that, or at least run PRP with those machines, for far superior error checking. 
20190222, 17:59  #14  
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
10544_{8} Posts 
CUDALucas repositories maintenance needed
Quote:
The mirror at https://download.mersenne.ca/CUDALucas lacks the v2.06 may 5 2017 build of Windows multiple executables package, but has a CUDA9.1 supporting version. (Wasn't there a CUDA10 version of CUDALucas build done also? Maybe I'm thinking of an mfaktc build.) As I recall, linux builds are distribution or version dependent, so executables posted built from any given linux environment are limited where they're useful in linux. MAYBE static linking would make it less so. For some recent experience in getting it to compile in linux, see the CUDALucas thread, such as https://www.mersenneforum.org/showpo...postcount=2670 Please consider posting there some successful compiled linux executables, specifying what environment and CUDA level and compute capability range they are for. Last fiddled with by kriesel on 20190222 at 18:10 

20190222, 18:14  #15  
Aug 2006
3×5^{2}×79 Posts 
Quote:


20190222, 20:09  #16  
"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest
4452_{10} Posts 
Quote:
%badresidues=( 'cllucas', '0x0000000000000002, 0xffffffff80000000', 'cudalucas', '0x0000000000000000, 0x0000000000000002, 0xfffffffffffffffd', 'cudapm1', '0x0000000000000000, 0x0000000000000001, 0xfff7fffbfffdfffe, 0xfff7fffbfffdffff, 0xfff7fffbfffffffe, 0xfff7fffbffffffff, '. '0xfff7fffffffdfffe, 0xfff7fffffffdffff, 0xfff7fffffffffffe, 0xfff7ffffffffffff, 0xfffffffbfffdfffe, 0xfffffffbfffdffff, '. '0xfffffffbfffffffe, 0xfffffffbffffffff, 0xfffffffffffdfffe, 0xfffffffffffdffff, 0xfffffffffffffffe, 0xffffffffffffffff', 'gpuowl', '0x0000000000000000', 'mfaktc', '', 'mfakto', '' ); Residue64 values are not as applicable for mfaktx. The bad CUDAPm1 residues seen with lots of f's were cyclic, not monotonic repeats. Mfaktc can return a known specious factor 38814612911305349835664385407. It's only valid for one p value, which is part of the self test. I think based on past experience with a couple declining gpus here, that this shows up for other exponents at declining hardware reliability. Last fiddled with by kriesel on 20190222 at 20:16 

20190223, 05:40  #17  
Serpentine Vermin Jar
Jul 2014
2·1,637 Posts 
Quote:
Honestly, George and I are at the point where when we see the email notification that a possible prime was found, and we see the cudalucas version is 2.05.1, we just ignore it. WAY too many false positives. To put it simply, if you're using cudalucas 2.05.1, update it. 

20190223, 05:44  #18 
Serpentine Vermin Jar
Jul 2014
2×1,637 Posts 
I apologize, Travis, because I saw the multiple emails that the server generated when you submitted the result. I meant to email you to let you know it was almost certainly because of a bug in that version of code, but I didn't get a chance.

20190223, 05:49  #19 
Jan 2019
Pittsburgh, PA
347_{8} Posts 
Greetings!
I had the same problem running cudaLucas 2.05 on my 2070 and 2080, returning zero residues from the start. I was able to solve the problem by running 2.06 beta. Maybe it's a driver or cuda software issue I assume? As it does not seem to affect pascal cards. 
20190223, 15:56  #20 
"Daniel Jackson"
May 2011
14285714285714285714
601 Posts 
So what was the exact exponent that the OP posted? Is it really a false positive? If not, could you please PM me the exponent?

20190223, 20:59  #21  
"/X\(‘‘)/X\"
Jan 2013
2·1,433 Posts 
Quote:


20190223, 22:40  #22 
Jan 2019
Pittsburgh, PA
3×7×11 Posts 
I'm curious, what is the probability that a residue from an LL test is bad? Is it dependent on the software/hardware/exponent/FFT size/etc?
If the residue is not guaranteed to be 100% correct (well I guess that's why we have double checks), what can we do overall to improve the accuracy (... beside getting ecc memory and quadros/tesla graphics) and should we be expecting bad results in some kind of frequency? And how unlikely is it for both the original LL test and the doublecheck test for an exponent to return the bad residue that is identical? I should probably read the wikipedia page on FFT or something to understand it, but procrastinates. How much prerequisites do I need to understand the mathematical concept and proof behind fft assuming i have the standard algebra/analysis background as a grad student? Any recommendations on any resources that introduces and proves this topic? Thanks guys. I appreciate it. 
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