Mersenne: Double Checking
Will the 64-bit residue be the SAME when a given exponent was originally Lucas-Lehmer tested with a 384K FFT, but the double-check is performed using a 448K FFT ? mikus _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Double Checking
On Saturday 28 June 2003 18:47, you wrote: Will the 64-bit residue be the SAME when a given exponent was originally Lucas-Lehmer tested with a 384K FFT, but the double-check is performed using a 448K FFT ? Hopefully - in fact the whole 2^p-1 bit residue R(p) should be the same! R(2)=4 R(n+1) = R(n)^2 -2 modulo 2^p-1 I don't see how the FFT run length should affect this ... in fact the FFT is only used at all because it's the most efficient method known of doing the multiplication of very large numbers. If the residues calculated with 384K FFT 448K FFT are different, then: - most likely, at least one of the runs has been affected by a glitch of some sort; - or, the 384K FFT run length is too small some data value was rounded to the wrong integer during the run - I do not think that this is very likely unless serious abuse has been made of the SoftCrossoverAdjust parameter; - or, there is a systematic error in the program code for at least one of the run lengths. Since short runs (400 or 1000 iterations) have been crosschecked with various FFT run lengths, again I do not think this is very likely. Regards Brian Beesley _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Double-checking milestone!
Congratulations GIMPSters, Yesterday the last double-check below M(6972593) came in. This proves there are no undiscovered Mersenne primes below M(6972593) making it the 38th Mersenne prime. Thanks to everyone for all their hard work in making this milestone possible. Keep on crunching and have fun, George --- Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.449 / Virus Database: 251 - Release Date: 1/27/2003
Mersenne: Double checking factoring
Is there a double check for factoring when no factor is found? Since it seems to be interesting to know what are the smallest factors of mersenne numbers, it seems wothwhile to have a proof (by double checking) that the smallest factor is, say, 2^66 (This also applies to the case where factors are indeed found - to verify that no smaller one was missed due to an error). Norbert _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Double Checking Errors
At 07:28 PM 8/9/2002 -0700, Gary Edstrom wrote: That brings to mind another question. I was wondering what you do when you detect an error during double checking. Do you notify the person that sent in the erroneous result so that he can check out his computer further? No, for several reasons. 1) We don't know your double-check is wrong until a triple (or even quadruple) check is run. Thus, it could be a few months before we'd email you. 2) If a first time check is bad, it will be two or three years before the double check and triple check come in to confirm this. 3) It would be a fair amount of work for me. Right now the server does not verify double-checks. That is done by me, with the aid of a program, at home. Matching bad results with email addresses, sending the email, and wading through bounced emails is not something I would relish! Is there interest in adding a new file to ones you can download at the bottom of http://www.mersenne.org/status.htm? It could contain all the confirmed bad results (I have kept this data). This would make it easier for you folks to check and see if you have any problem computers. _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Double Checking Errors
Yes George, A list of all bad results would be an excellent idea. It would go a long way in helping us keep tabs on our computers and at the same time keep the stats junkies - like those on Team Prime Rib :-) - accurately informed on their contribution or lack thereof. Anurag Garg _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
RE: Mersenne: Double Checking Errors (and Prime95 NT service issues)
I think looking at that file would at least provide interesting to the curious among us. I say go for it :) Aaron PS - Regarding the running Prime95 as an NT service... I concur that if you run it on your own machine, it's obviously not a security risk since I'd hope that you're already a local admin on your own NT/win2k/winxp box. For more protected machines, any vulnerability would still require the ability to logon locally, and that's something that any good server should already address. The major flaw only seems to be workstations where maybe you don't allow the normal user to have local admin access, and I know some companies set it up that way. And in that case, WITH PROPER PERMISSION (had to say that), it would make more sense to run it without the icon visible anyway so the user isn't distracted or can change things. All in all, what I'm saying is, it seems to be a moot point in 99.% of the cases I can imagine. -Original Message- From: [EMAIL PROTECTED] [mailto:mersenne-invalid- [EMAIL PROTECTED]] On Behalf Of George Woltman Sent: Saturday, August 10, 2002 11:25 AM To: Gary Edstrom; [EMAIL PROTECTED] Subject: Re: Mersenne: Double Checking Errors At 07:28 PM 8/9/2002 -0700, Gary Edstrom wrote: That brings to mind another question. I was wondering what you do when you detect an error during double checking. Do you notify the person that sent in the erroneous result so that he can check out his computer further? No, for several reasons. 1) We don't know your double-check is wrong until a triple (or even quadruple) check is run. Thus, it could be a few months before we'd email you. 2) If a first time check is bad, it will be two or three years before the double check and triple check come in to confirm this. 3) It would be a fair amount of work for me. Right now the server does not verify double-checks. That is done by me, with the aid of a program, at home. Matching bad results with email addresses, sending the email, and wading through bounced emails is not something I would relish! Is there interest in adding a new file to ones you can download at the bottom of http://www.mersenne.org/status.htm? It could contain all the confirmed bad results (I have kept this data). This would make it easier for you folks to check and see if you have any problem computers. _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Double Checking Errors
On Mon, 05 Aug 2002 15:09:55 -0400, George Woltman [EMAIL PROTECTED] wrote: At 09:58 AM 8/4/2002 -0700, you wrote: I was curious about how often the PrimeNet server detects a problem in a double-check result and has to re-submit the exponent for another round of testing. I looked around the GIMPS web pages and couldn't find any figures. I don't have any exact figures. I'd guess between 2 and 3 percent of the time. That brings to mind another question. Since I have only been around for a couple of weeks and have only completed LL testing a single exponent, I don't know what all of your procedures are. I was wondering what you do when you detect an error during double checking. Do you notify the person that sent in the erroneous result so that he can check out his computer further? It would seem that notifying people when their systems are in error would be even better than the initial self test that is run because it gives an on-going status for the computer. Thanks, Gary Edstrom P.S: I have two more results both due next Wednesday: An LL test from this desktop computer, and a double-check from my laptop. _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Double Checking Errors
I was curious about how often the PrimeNet server detects a problem in a double-check result and has to re-submit the exponent for another round of testing. I looked around the GIMPS web pages and couldn't find any figures. Thanks, Gary _ Unsubscribe list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Double Checking
TWIMC: Is a single Double Check always enough to retire an exponent? Regards, Stefanovic _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Re: Mersenne: Double Checking
Stefan Struiker asked: Is a single Double Check always enough to retire an exponent? Regards, Stefanovic IIRC, George compares the residues once per week of all the double-checks compared that ween when he updates the database. If they don't match, then either one or both of the previous runs were in error; this happens about 1.5% of the time. That figure can be expected to increase as people continue double-checking longer runs. George reissues the mismatched exponents until two residues match. Nathan Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Double Checking Finds A Factor
Hi All, Well it finally happened to me, I was double checking an exponent in the 5M range, using the beta of V20 and it found a factor! I often wondered about how often that happened, anyone have any other hard data? 5008021 63 DF 7054282710141713489 10-Apr-00 07:09 gateway regards Gordon _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
RE: Mersenne: Double-Checking
Assume that a set of 400,000 exponents get single checked, and double checked, and the error rate per check is 0.5%. If the error occurrence is independent, that means about 4000 will not match. Of these 4000 then the triple checks would have errors in about 20, and require a quadruple check which most likely would match one of the previous results. But, just to clarify, even if both a first time check and a double check both fail and come up with a bad residue for some reason, the partial residues from each run won't match, so they'd still be caught and flagged for a triple check. A triple check will match the first or the second run, or maybe neither requiring a 4th run. It all sounds pretty solid to me. :-) _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Double-Checking
Do ALL exponents get Double-Checked? ...or are only selected exponents done beecause the original LL run was suspect? Just curious, Russ _ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
Mersenne: Double-checking credits on Primenet?
I just started my second machine on double-checking and am curious on whether I would expect to see my LL P90 year total increase when a double-checking assignment is turned in. Also, I notice that one can disable "Request whatever type of work makes the most sense" and then proceed to select *two* types of work that you want. How does the server decide which to send? I assume that it'll choose factoring over double-checking, double-checking over primality testing, and factoring over primality testing. Is this correct? If so, the windows versions might better be served wait radio-buttons so that only one can be selected. Rick. - [EMAIL PROTECTED] http://www.alienshore.com/ Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Re: Mersenne: Double-checking (was Chronons)
At 11:59 AM 1999/03/05 GMT, "Brian J Beesley" [EMAIL PROTECTED] wrote: (Ken wrote) Right. The odds heavily favor both mismatched residues being nonzero. A zero residue at the last iteration is what indicates primality. Depends on what you mean. If a Mersenne number that has been tested once really is prime, but the test "went wrong", then we have a wrong result i.e. calling the number composite when it isn't. I mean that nearly all mersenne numbers are nonprime even if the exponents are prime, so of the numbers we bother to LLtest, when an error occurs, the odds are 99%+ that it does not conceal an actual Mersenne prime. And in the unusal case of a nonprime Mersenne number being erroneously identified as prime, it would be multiply-checked and so the error caught, rather than being announced as a prime. This is why double-checking is so important, if we want to find *all* the Mersenne primes for exponents up to a given limit. I agree that double checking is important in an exhaustive search, and that exhaustive search (rather than haphazard or opportunistic search) is valuable. There *might* be one or two lurking somewhere in the mass of exponents which have only been tested once. Also what causes the errors, bugs in the code? What I've seen most often is that prime95 and its relatives provide early warning of unreliable hardware, whether cpu, RAM module, or motherboard. Usually caused by overheating - failed CPU fan, poor ventilation or excessively hot environment, overclocking, poor thermal contact between processor substrate and heatsink ... The sorts of things I've seen include, in systems with good cpu heat sinking, multiple case fans, cpu fans properly installed and no overclocking: mechanically ill-fitting case causing a system to be unreliable unreliable single SIMM out of a set of 4 unreliable CPU chip unreliable motherboard whether these component-level problems were due to electrical stress (power outages, spikes, brownouts, static), thermal stress (overheating or too-frequent power on/off), or latent defects in manufacture is unknown. Ken Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Mersenne: Double-checking (was Chronons)
Hi, At 07:35 PM 2/26/99 -0800, Spike Jones wrote: How about sweetening the pot for anyone who is doing double checking that discovers a mistake in the first LL analysis? How does this work? The first LL test returns a residual, then the double checking routine takes that residual and... what? How often is a result overturned by double checking? From your point of view a double-check is just like a first time test. You run a Lucas-Lehmer test and when done send in your 64-bit residue. I compare that residue to the first run and if they match, the exponent is declared double-checked. If they don't match, a third test is run to properly double-check the number. Finding an error in the first LL test is not rare. I've said about 1 in 200 are incorrect. When the entire 1,400,000 - 2,000,000 range has been double-checked I'll perform some more rigorous analysis of the reliability of first-time LL results. Best regards, George Unsubscribe list info -- http://www.scruz.net/~luke/signup.htm
Re: Mersenne: double checking
Hi Bryan, At 03:45 AM 11/18/98 -0500, Bryan Fullerton wrote: I've noticed that when I manually request exponents from the Primenet web page the lines to be inserted into worktodo.ini all start with Test=, but when the util gets double checking exponents itself the lines start with DoubleCheck=. Is there any functional difference between these two? Scott should tweak his web forms. There is only one difference. The probability of finding a new prime as reported by Test/Status is much smaller when the correct DoubleCheck= syntax is used. Best regards, George
