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Old 2003-07-24, 21:37   #1
Firedog18
 
Jul 2003

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Default chance of finding a factor?......Read me read me read me :)

when you 1st start the LL test prime95 says

"chance of finding a factor is an estimated X.XX%"

what do most people get for the X.XX%
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Old 2003-07-25, 08:08   #2
Firedog18
 
Jul 2003

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50 people read this and no one posts a single thing...:(
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Old 2003-07-25, 08:14   #3
smh
 
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"Sander"
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Default Re: chance of finding a factor?......Read me read me read me

Quote:
Originally Posted by Firedog18
when you 1st start the LL test prime95 says

"chance of finding a factor is an estimated X.XX%"
A LL test won't find a factor. You only get this message when you are running P-1
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Old 2003-07-25, 08:37   #4
Firedog18
 
Jul 2003

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ummmm...yeah that also.....LOL

my bad
so when testing a number what are the steps?

factoring 2^x
P-1 factoring

then what?
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Old 2003-07-25, 11:17   #5
eepiccolo
 
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After the program finishes trial factoring (factoring 2^x) and p-1 factoring, if a factor is not found, it will perform the Lucas-Lehmer (LL) test. The idea for factoring is that maybe we can find a small factor of the number to show that the number is not prime, so we don't have to perform the LL test, because the LL test can take from several weeks to several months, depending on the computer and depending on the exponent.

And if the LL test starts, it has to get all the way to 100% to determine if the number is prime or not. The LL test doesn't find factors, it just determines primality.
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Old 2003-07-25, 12:03   #6
markr
 
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The last P-1 test I saw start gave a probability something like 4.87%. It will vary with how much memory you allow prime95 to have (and probably other stuff).
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Old 2003-07-25, 12:35   #7
Wolf
 
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Just started doublechecking a 9M exponent
P-1 bounds B1=50000 B2=750000
Chance of finding a factor is an estimated 2.91%
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Old 2003-07-25, 13:43   #8
QuintLeo
 
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I think I usually get an estimate around 4.5%, but I'm NOT gonna stop and restart clients just to check - and I don't think Prime gives that estimate anyway at anytime other than the start of the P-1 1'st stage?
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Old 2003-07-25, 14:41   #9
dswanson
 
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3.62% for M10979453 with bounds B1=60000, B2=1020000
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Old 2003-07-25, 17:10   #10
PrimeFun
 
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M10983677 B1=60000 B2=1110000 (64 bit level) 3.38%
M10983677 B1=55000 B2=907500 (65 bit level) 2.8%
M10983677 B1=50000 B2=775000 (66 bit level) 2.31%

Prime set to use 400MB of ram on all cases.

So as you can see it all depends on how far that factor has been factored up to this point. The higher you go the less likely you are to find a factor, which makes sense.
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