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Old 2018-01-22, 15:06   #1
justinstevens42
 
"Justin Stevens"
Jan 2018
Edmonton, Alberta

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Default Status of Double Checked LL Test

After two users confirm the same residue using the Lucas-Lehmer test, why doesn't the status of the number change on the report page? For instance, for $M_{47605039}$, despite the LL just being confirmed , the status still says "No factors below $2^{73}$." Possibly I'm misinterpreting how the LL test works in the first place?
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Old 2018-01-22, 15:57   #2
chalsall
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"Chris Halsall"
Sep 2002
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Quote:
Originally Posted by justinstevens42 View Post
Possibly I'm misinterpreting how the LL test works in the first place?
The LL test shows that the exponent is composite (unless, of course, the residue is 0 at the end of the test). The DC confirms that the original test was done correctly (assuming the residues match).

However, the report also shows that although the candidate is known not to be prime (read: there are at least two factors beyond 1 and itself), there are also no known factors below 73 "bits". This is useful knowledge for those who enjoy factoring candidates after they've already been proven composite; this work doesn't help the main GIMPS goal of finding Mersenne primes at all, but some enjoy doing it anyway.

Last fiddled with by chalsall on 2018-01-22 at 16:04 Reason: s/factoring candidates/factoring candidates after they've already.../
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Old 2018-01-22, 16:03   #3
retina
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Quote:
Originally Posted by justinstevens42 View Post
Possibly I'm misinterpreting how the LL test works in the first place?
Yeah, LL tests don't find factors. LL can only prove that factors exist, or don't exist. It can't tell you the factors, or the size of the factors, or how many factors. It gives a simple yes/no result about whether there are factors to be found, nothing else.
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