> On Tuesday 24 October 2006 19:18, david eddy wrote: > > > > what happens when a LL test is proved wrong? > >
Brian Beesley wrote: > Hmm ... the LL test is never wrong, it is a mathematical theorem! > > However computations performed in a computer can (and sometimes do) go wrong, > for a number of reasons. The important reason a LL-test goes wrong is due to using floating point FFT to perform exact integer arithmetic. It is fortunate that double-checking introduces effective certainty to the result, enabling us to claim to have "proved" that M13,466,917 is the 39th Mersenne prime. As I am currently doing a double check I am interested in how the probability of an erroneous LL test varies as we go from the bottom to the top of the range of exponents for a given FFT size. The probability at the top of the range is presumably such that the cost in time of an erroneous LL test balances the extra time needed for the next FFT size, for which the chance of error is small. David Eddy _________________________________________________________________ Be one of the first to try Windows Live Mail. http://ideas.live.com/programpage.aspx?versionId=5d21c51a-b161-4314-9b0e-4911fb2b2e6d _______________________________________________ Prime mailing list [email protected] http://hogranch.com/mailman/listinfo/prime
