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# Re: Change definition of complex::norm

*To*: Brad Lucier <lucier at math dot purdue dot edu>
*Subject*: Re: Change definition of complex::norm
*From*: Benjamin Kosnik <bkoz at redhat dot com>
*Date*: Thu, 1 Nov 2001 18:17:15 -0800 (PST)
*cc*: Gabriel Dos Reis <gdr at codesourcery dot com>, Brad Lucier <lucier at math dot purdue dot edu>, gcc at gcc dot gnu dot org, hjstein at bloomberg dot com, nbecker at fred dot net

We might want to consider moving this over to the libstdc++ list, instead
of gcc.
> Sorry, I forgot that the exponent range is not symmetric, the formula I
> gave for the absolute error tolerance is incorrect. The smallest
> nonzero denormal in double precision IEEE is 4.940656e-324. And in the
> example I gave, the answer in exact arithmetic is exactly halfway between
> 4.940656e-324 and 0.0, so there is little to choose between them.
I'm hoping Gaby will summarize this argument.
I would think that this patch could go in, or be provided for float,
double specializations of complex.
Can you generate a patch and post it to libstdc++@gcc.gnu.org?
Does this impact the performance noted here:
http://gcc.gnu.org/ml/libstdc++/2001-09/msg00091.html
http://gcc.gnu.org/ml/libstdc++/2001-09/msg00110.html
thanks,
benjamin