20110630, 21:38  #1 
Jun 2011
2×3 Posts 
test of the software
What testing was done on the Primenet software to be sure it works for large exponents? i raise this question because I looked at the LL results
for exponents from 59,000,000 to 110,000,000 and for those few exponents that were tried twice the residues never agree and an error was reported in some of the cases. 
20110630, 23:42  #2 
Dec 2010
Monticello
5×359 Posts 
How many few? And by what kind of machines? Prime95 (as opposed to Primenet, which is the server and the internet communications) is well beyond the point where actual machine errors can be expected, especially in overclocked machines.
If you want, we can pick an exponent, maybe one of those with multiple LL residues, and make sure it is TF'ed to 72 or 73 bits, and then both run an LL test on it. But it's a project, and it will take a month or two. 
20110701, 01:27  #3 
Jun 2011
6_{8} Posts 
results of LL for large exponents
I count 7 unverified pairs that have unmatched residues.
the display does not reveal the type of machine that was used. 1 pair shows an error. I should have used the term Prime95 instead of Primenet. I still would like to know how the software was tested for large exponents. 
20110701, 02:07  #4 
Dec 2010
Monticello
11100000011_{2} Posts 
And how many verified? Are you interested in attempting LLD on any of them?

20110701, 02:32  #5 
6809 > 6502
"""""""""""""""""""
Aug 2003
101×103 Posts
13·787 Posts 
The software works great. Many of those above the current range and below 79,300,000 have been done a while back. The machines are the issue. As a test takes longer (the bigger the number the longer the test), there is a greater chance of an error occurring in the machine (hardware related issues and cosmic rays, etc.) This has been seen before when there was a push by some to try to find the first prime with 10 million digits. Many of those early tests suffered hardware issues.
The basic algorithm to run the LL test is the same. The software is run on smaller numbers, but using the larger FFT sizes to verify that they work. The FFT's are also used in other tests. The program is ok, it is the actual machines. There are other threads around that talk about this. 
20110701, 02:51  #6  
"Richard B. Woods"
Aug 2002
Wisconsin USA
1111000001100_{2} Posts 
prime95
Quote:
Before you use that report again, please carefully examine all the checkbox options. When the "Exclude verified results" box is checked (by default), the report excludes all verified results. When you _do_ specify the verified results (by unchecking the "Exclude verified results" box) and exclude the unverified results (by checking the "Exclude unverified results" box), you get something like: Code:
Verified test results Exponent,User name,Computer name,Residue 67108763,Stephan Grupp,P4,53023CAC72917105 67108763,Brian J. Beesley,Canopus,53023CAC72917105 67239937,Alexandr Fomin,FAA,F2DC9FBF28E585EB 67239937,Luigi Morelli,Manual testing,F2DC9FBF28E585EB 68808029,wavelet3000,Manual testing,A9878EE6E59BA060 68808029,msft,,A9878EE6E59BA060 69100037,Team_Bundu,bundu5,2C97F61B5F6869BA 69100037,msft,Manual testing,2C97F61B5F6869BA 70022021,Norman Carlson,NormNew,8FC5E5F795149FF8 70022021,msft,Manual testing,8FC5E5F795149FF8 79299821,Ars Technica Team Prime Rib,DSheets_02,C1D3BB65E8D3ED07 79299821,arnaud,SPR18,C1D3BB65E8D3ED07 100000007,William Christian,StarQwest1,F9042256B193FAA0 100000007,TeamComputerraRU,Yxine,F9042256B193FAA0 Have you considered that 1) the prime95 software works in partnership with hardware, 2) that hardware sometimes, in the midst of quadrillions of instructions, has a bit go wrong because of a slight defect or a cosmic ray hit, and 3) the longer the LL test (i.e., the higher the exponent), the greater the chance that a hardware error will occur sometime during it? Last fiddled with by cheesehead on 20110701 at 03:04 

20110701, 04:32  #7 
Jun 2011
2·3 Posts 
how was it tested?
Perhaps it would be useful to report for the unverified results
the software version used and the machine type. If cosmic rays are the explanation, then it would be interesting to see a plot of exponent range vs number of mismatched exponents in that range. 
20110701, 23:42  #8 
"Richard B. Woods"
Aug 2002
Wisconsin USA
1111000001100_{2} Posts 
This sort of thing is more often discussed in the Data subforum (mersenneforum.org > Great Internet Mersenne Prime Search > Data). Look through some of the threads there.

20110704, 20:52  #9  
"Patrik Johansson"
Aug 2002
Uppsala, Sweden
5^{2}×17 Posts 
Quote:


20110707, 14:19  #10 
Feb 2011
2^{2}·13 Posts 

20110708, 01:53  #11  
Jun 2011
6_{8} Posts 
error rates
Quote:
I am seeing decline error rates generally as a function of exponent size. If cosmic rays are cited as reason for errors, then with larger exponents i expect longer running times, so more chance for the rays to flip a bit and cause an error. But I don't see that happening. Could there be another explanation? I think what is really needed is a graph of error rate by machine type as a first approximation. 

Thread Tools  
Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Fastest software for Mersenne primality test?  JonathanM  Information & Answers  25  20200616 02:47 
Modifying the Lucas Lehmer Primality Test into a fast test of nothing  Trilo  Miscellaneous Math  25  20180311 23:20 
Intel software emulator lets you test drive AVX512  tServo  Hardware  0  20160401 15:31 
Legal to implant prime95 as a stresstest in another software  SvenBent  Software  1  20141007 17:36 
A primality test for Fermat numbers faster than Pépin's test ?  T.Rex  Math  0  20041026 21:37 