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Old 2004-08-26, 06:36   #1
ZachB
 
Aug 2004

102 Posts
Default LL question

Just wondering, when Prime95 is testing a number for primality, is it possible for it to discover that it's not prime partway through its testing, or does it have to test the number all the way to the end before it can be called a prime or not?
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Old 2004-08-26, 10:28   #2
S80780
 
Jan 2003
far from M40

53 Posts
Default

As for the LL-Test, yes, it has to be passed completely, before you can say anything about the tested number being prime or not.
As for Trial-Factoring, no, each candidate can be a factor thus stopping the test nearly instantly (as far as I know, the actual bit-level will be finished before).
As for P-1, no, the test can stop at any time a GCD is computed. Prime95 computes (up to) two GCDs, one for each stage of the P-1-Test.
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