> -----Original Message----- > From: Robert Dewar [mailto:de...@adacore.com] > Sent: Sunday, May 08, 2011 13:02 > To: Michael D. Berger > Cc: gcc@gcc.gnu.org > Subject: Re: numerical results differ after irrelevant code change > > On 5/8/2011 12:48 PM, Michael D. Berger wrote: > > > I made the changes you suggest. While I was previously getting > > -1.16e-16 and -1.03e-16 depending presence of an "extra" > > class member, I now get 1.11e-16 (sic not -). But it is now > > independent of the extra class member, which is excellent. > Hopefully, > > things will stay that way. > > This is a fairly big change to make in your program, since it > completely alters the fpt semantics, but probably in a > desirable way. Sounds like you don't have any real careful > analysis of the reliability of the results or needed > precision anyway, you just don't like the non-repeatability, > and indeed the change to restrict the precision to 64-bits > should work to solve that problem. >
As I should have said originally, I just did the -march=pentium4 -mfpmath=sse, I didn't change to a 64 bit system. Will that get the repeatabiility? It has on the brief test I did. Thanks, Mike.