> -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of John R > Pierce > Sent: Friday, June 13, 2003 6:42 PM > To: Aaron Lehmann; Mersenne discussion list > Subject: Re: Mersenne: M#40 - what went wrong? > > > > On Fri, Jun 13, 2003 at 03:16:24PM -0400, George Woltman wrote: > > > 2) This case results from the way my C compiler treats floating point > NaN. > > > NaN stands for not a number. If NaN is converted to an integer, the > integer > > > is zero. So if the FFT data is all NaNs, prime95 will report a prime. > > > > I expect this is a FAQ and apologize in advance, but in the age of > > SSE2 integer instructions why is it still necessary to use floating > > point calculations? > > precision. > > The extended FP multiply has 64 bits of mantissa. SSE2 is, I believe, > restricted to 32bit multiplies, so it would take 4 times as many to equal > one 64bit (gross simplification, but sufficient for the purposes here).
Is that still true on the 64-bit platforms (ia64 and amd64)? Brandon > > > _________________________________________________________________________ > Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm > Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers > > _________________________________________________________________________ Unsubscribe & list info -- http://www.ndatech.com/mersenne/signup.htm Mersenne Prime FAQ -- http://www.tasam.com/~lrwiman/FAQ-mers
