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Old 2008-09-06, 20:18   #1
DasIon
 
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Default Holy Saint Lucas! 2 new primes? (M45 related, and M47)

Did I miss something? The status page reports 2 unverified primes!

Frank
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Old 2008-09-06, 20:59   #2
akruppa
 
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Indeed. But I don't find any decoy exponent with the fake residue 0xB6C801... in cleared.txt like we should get if there were a new prime.

Alex
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Old 2008-09-06, 21:00   #3
Mini-Geek
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Quote:
Originally Posted by DasIon View Post
Did I miss something? The status page reports 2 unverified primes!

Frank
Wow! Nothing I heard of before. Anyone know when this appeared?
Quote:
Originally Posted by akruppa View Post
Indeed. But I don't find any decoy exponent with the fake residue 0xB6C801... in cleared.txt like we should get if there were a new prime.

Alex
The B6C isn't required (it would only be like that if the last 4 bits in the exponent were equal, but note the last one is always 1 because it's odd, so there's 8 combinations, unless I'm missing something else), but regardless, there's nothing that matches "80" in the requisite position (and that's required by the algorithm).
e.g. my first GIMPS exponent, 33983237, would make an algorithm of 0x5A480124800013__

Last fiddled with by Mini-Geek on 2008-09-06 at 21:23
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Old 2008-09-06, 21:23   #4
davieddy
 
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Perhaps this thread explains it?
http://mersenneforum.org/showthread....149#post141149
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Old 2008-09-06, 21:28   #5
akruppa
 
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I doubt it. Many people must have used Prime95 to test know Mersenne primes before, and they never showed up as unverified new primes so far.

Alex
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Old 2008-09-06, 21:30   #6
Mini-Geek
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Quote:
Originally Posted by akruppa View Post
I doubt it. Many people must have used Prime95 to test know Mersenne primes before, and they never showed up as unverified new primes so far.

Alex
Then again, how often does Prime95 think it's a new Mersenne prime? I know I've done what you describe myself, but it didn't try to report it.
I hope that's not all it is, but admittedly it does seem rather unlikely that while M45 is verifying we'd find M46.
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Old 2008-09-06, 22:28   #7
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Quote:
Originally Posted by DasIon View Post
Did I miss something? The status page reports 2 unverified primes!

Frank
Woooohooo, what's going on?? TWO primes??!!??
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Old 2008-09-06, 22:33   #8
cheesehead
 
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Quote:
Originally Posted by Mini-Geek View Post
Then again, how often does Prime95 think it's a new Mersenne prime?
Apparently, it doesn't consult a list of already-known Mersenne primes (as the server does, IIRC) ... which makes sense in that a static built-in table would become obsolete as new ones were discovered (not to mention being able to test the new-prime code by deliberately testing a known one).

Quote:
I hope that's not all it is, but admittedly it does seem rather unlikely that while M45 is verifying we'd find M46.
OTOH the longer the verifying effort for one discovery stretches out, the more time there is for finding and reporting another discovery before the previous one's verification is complete.
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Old 2008-09-06, 22:41   #9
ixfd64
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You know what's really odd?

I had a feeling that this would happen not long after M45 was reported. I guess I need to develop my prime-predicting powers.

OK, maybe I read way too many comic books.
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Old 2008-09-06, 22:55   #10
Flatlander
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I suppose the worst case scenario is that someone just missed out on a large share of $100k.
I hear the sound of distant crying.

Last fiddled with by Flatlander on 2008-09-06 at 23:13
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Old 2008-09-06, 22:57   #11
ixfd64
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Quote:
Originally Posted by davieddy View Post
I doubt that's the case. Otherwise, we'd be getting a bunch of "unverified" primes due to people testing their GIMPS clients!

I think there are three possibilities:

1. Some really did find a new prime.
2. Someone (who is not on the official verification team) guessed the exponent of M45 and independently tested it on a high-performance system.
3. Someone used an old version of Prime95 that caused false positives.

I have a strong feeling that #2 is the case, but I'm really hoping it's #1.

Last fiddled with by ixfd64 on 2008-09-06 at 23:01 Reason: grammar
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