[Cfp-interest 1478] Re: complex multiplication and division

[Damian McGuckin]

On Mon, 10 Feb 2020, paul zimmermann wrote:

> on the gcc10 machine from the GCC compile farm, with gcc 6.3.0, I get:
>
> x=(-1.0689346237980500e+252,7.8846096489686452e-145)
> y=(5.1152592576527620e-318,6.7327111521288819e+78)
> x/y=(1.1710898434244477e-223,1.5876733750267203e+173)
>
> Same on the machine "devel03" from the Plafrim platform with gcc 4.8.5:
>
> x=(-1.0689346237980500e+252,7.8846096489686452e-145)
> y=(5.1152592576527620e-318,6.7327111521288819e+78)
> x/y=(1.1710898434244477e-223,1.5876733750267203e+173)
>
> This is with -O0 (or no -O option), with -O1 or higher I get the MPC result
> (since then GCC uses constant folding, calling MPC).

I tried all -O options on my gcc 4.8.5.  Always the same answer, i.e. that 
you get from MPC 3.51...e-225.  I only get the about answers with 4.4.8.

I have no gcc 6.3.0, only an 8.?.? and 9.3.1.  These are CentOS packages.

It has me stumped.  SOrry, I cannot reproduce your issues.

Regards - Damian

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