On 31st Oct George Woltman wrote: > At 03:22 PM 10/31/2006, you wrote: > > >On the other hand, the excerpts from you and George which Steinar dug up > >suggest that you were indeed trying to fix the boundaries at the point where > >probability of roundoff error equalled the percentage time increase incurred > >by using the next size of FFT. > > No, Brian and I choose the boundary points such that a roundoff error would be > rare but not impossible. The definition of rare was rather arbitrary based on > extrapolation from experimental data. > > Why "rare" instead of "optimal"? Well, I don't want to be the one to > tell someone > he missed a prime because his run had a not-unexpected round off error.
OTOH he (or she!) was more likely to miss finding a prime because excessive time was wasted using the larger FFT. It amounts to paying unnecessarily high insurance. How about informing testers of exponents at the bottom of one of your ranges what the risk of using the smaller FFT is, and allowing them to take it if they want to? BTW I replaced Prime95v24.14 with v23.18 mid run, achieving a 14% speed up on my PII. Any danger I have sabotaged the test? Regards 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
