This is the mail archive of the mailing list for the libstdc++ project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: std::norm improvement

On Wed, Mar 4, 2009 at 9:22 AM, Andrew Pinski <> wrote:
> " Still, I think
> gcc is pointlessly (is that an English word?) decreasing performance
> if ffast-math is not on (it's not on even with -O3).
> "
> No it is not, this is the problem here. That is from the thread you
> wrote in.

Yes, I've learned afterwards in the same thread that it is not pointless.

> You did not test every single input to figure out if your
> implementation is better or worse. ?I think it might be best if you
> tested every input include NaNs and infs. ?That is where some problems
> come into play also I think.

You mean like every pair of real numbers? Isn't there about 2^128 of
them (for double)? Even if a single test took a mere picosecond, that
would still eat up a trillion years...

I can certainly test all combinations of Infs and NaNs, if that's what
you meant. I'll report back with the results.


RNDr. Jaroslav Hajek
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]