Re: std::norm improvement

[Jaroslav Hajek <highegg at gmail dot com>]

On Wed, Mar 4, 2009 at 9:32 AM, Jaroslav Hajek <highegg@gmail.com> wrote:
> On Wed, Mar 4, 2009 at 9:22 AM, Andrew Pinski <pinskia@gmail.com> 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.
>

Hmm, it seems that there's no simple fix to achieve (Inf, NaN) giving
Inf and (x, NaN) giving NaN, which is probably what is wanted. Sorry
for the noise.

regards

-- 
RNDr. Jaroslav Hajek
computing expert & GNU Octave developer
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz