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Old 2010-12-11, 19:21   #45
Primeinator
 
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Quote:
Originally Posted by NBtarheel_33 View Post
Only problem is that this single exponent (which is now holding up *two* milestones) is being run on a P3 by a user who updates only every 28 days, and is not due to finish the test until May of next year...

...yeah, yeah, I know, 100.00000001 is *still* faster than 100, and all that jazz.
Just think about it this way- we know that when it is updated, the apparent progress of all numbers below 'x' being tested at least once will jump by a LARGE amount.
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Old 2010-12-11, 20:13   #46
davieddy
 
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Quote:
Originally Posted by davar55 View Post
That was from the MARX brothers, as i recall.
Is that some newfangled computer or summat?
How much do they know about the FA Cup?
It may well be the comfy chair for them.

Oh no!
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Old 2010-12-12, 03:38   #47
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Quote:
Originally Posted by davar55 View Post
That was from the MARX brothers, as i recall.
Of course.
When we know it as well as we do, it almost
invariably sounds too contrived to be funny.

But then nobody can say it like Chico!

David

Oops. That sounds like a cue for cmd:)

Last fiddled with by davieddy on 2010-12-12 at 03:41
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Old 2010-12-12, 05:22   #48
Uncwilly
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moderation is needed
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Old 2010-12-12, 10:51   #49
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Quote:
Originally Posted by Mini-Geek View Post
[...] While I should hope there aren't many people intentionally submitting wrong results twice (or even once!), I would be surprised if no numbers are marked as done with DC with incorrect residues due to this.[...] I'd be surprised if any primes are missed by PrimeNet, though in the future a triple check, with results only allowed through trusted sources, checking large blocks of GIMPS work would probably be worthwhile.
Mini-Geek, your suggestion that the PrimeNet database may not be completely accurate is discouraging, and I'm especially wondering if there is something new that you now know and didn't know before to explain why you have apparently changed your mind?
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Old 2010-12-12, 10:51   #50
davieddy
 
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Quote:
Originally Posted by Uncwilly View Post

moderation is needed
Another typically witty comment, obviously conducive
to veering the thread (the creation of which was totally unnecessary)
back on ANY topic.

I think there is good reason why neither you nor I (prolific
contributors as we may be) are not considered moderator material

David
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Old 2010-12-12, 11:13   #51
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Quote:
Originally Posted by Brian-E View Post
Mini-Geek, your suggestion that the PrimeNet database may not be completely accurate is discouraging, and I'm especially wondering if there is something new that you now know and didn't know before to explain why you have apparently changed your mind?
I'm sure George has explained the practice before, but it could
certainly do with more publicity.

I think it goes like this:
If a second LLtest (referred to as a "Double Check" during its
execution) produces a residue different from the original, the number
is not listed as "composite" and a further test is allocated referred to
as LL rather than DC. Assuming (likely) that this residue matches one
of the previous, the number is put to bed as composite (or prime).

Hope this post is considered on topic and constructive.
Can't think of a suitable musical accompaniment or even a jest ATM,
UncWilly will be disappointed to hear.

David
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Old 2010-12-12, 13:12   #52
Mini-Geek
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Quote:
Originally Posted by Brian-E View Post
Mini-Geek, your suggestion that the PrimeNet database may not be completely accurate is discouraging, and I'm especially wondering if there is something new that you now know and didn't know before to explain why you have apparently changed your mind?
I wouldn't say there's new information, just a different way of looking at it. I was thinking within the normal PrimeNet framework, and mainly considering software/hardware errors instead of the effects of some kinds of cheaters/malicious people. Triple checks from regular users can't be trusted if we want 100% certainty of the GIMPS DB (after all, for completed DCs the full residue is shown; even if no credit is given anywhere for results in this triple check, you couldn't be sure they really did the work, unless they submitted results with a different shift and valid checksum; note that not all PrimeNet-allowed programs support those features!), it'd have to be a trusted third party. Within the normal PrimeNet framework, a triple check whose result doesn't match the first two would be considered wrong, but if we are doing a special check of PrimeNet/GIMPS results, we would retest it to see which is really right. Also, I think that hardware generally would produce an error every X hours of running, (instead of every X calculations) so in the future when tests can be run in a much shorter time, we'd have more reason to trust the triple check than the original tests.
Quote:
Originally Posted by Mini-Geek View Post
I'm 99% sure that triple checks are very close to being totally useless. (unless for some other purpose...definitely not useful in the same way that double checks are useful)
I was thinking mainly of software and hardware errors here. So I still think that triple checks aren't useful (well, technically they are, but in such a ridiculously slight way it hardly matters, something like changing the chance of matching accidentally-wrong residues from 1/(2^64)^2 to 1/(2^64)^3) in the main way that double checks are, i.e. for detecting accidental errors, but they are useful in another way: detecting fraudulent results.

Last fiddled with by Mini-Geek on 2010-12-12 at 13:18
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Old 2010-12-12, 13:29   #53
henryzz
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Another thing to consider is that occasional program versions have been released that aren't completely relyable(take pfgw recently for example as an extreme case). If that version does both ll and dc then we will have an error in our data.

Last fiddled with by henryzz on 2010-12-12 at 13:29
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Old 2010-12-12, 14:54   #54
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Quote:
Originally Posted by henryzz View Post
Another thing to consider is that occasional program versions have been released that aren't completely relyable(take pfgw recently for example as an extreme case). If that version does both ll and dc then we will have an error in our data.
Yes, but with the "different shift" requirement, I'm pretty sure the chance of a software bug like that producing identical residues is practically nil.
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Old 2010-12-12, 19:24   #55
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Cheesehead also gave me a superb informative reply when I asked about this issue as a newcomer to this forum.

I suppose when you go to the lengths of verification using only a "trusted" third party (which is not, of course, a universal concept), it ceases to be a true distributed computing project.
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