complex numbers

[Paolo Carlini]

Andreas Klein wrote:

>>... but notice that this issue is tricky: there are computational issues
>>(we are adding
>>at least a branch for each division) and correctness issues (what about
>>C99?)
>>    
>>
>As I see it the naive formula needs
>
>6 multipications, 2 divisions and 3 additions/subtractions
>
>and the improved formua needs
>
>1 comparision, 3 multipactions, 3 divisions and 3 additions/subtractions
>
>This look like a good deal. However for floting point computations I
>prevere good results over fast results.
>  
>
Thanks for the summary: I just sent a message to the gcc list, let's see 
what comes
out... Maybe you may want to reply something there.

>What do you meen with "correctness issues"?
>  
>
Have a look to the implementation: it looks like that even if we switch 
to the
better algorithm, still we don't get fully right C99. Of course this 
last point
must be better investigate (I'm not a floating point expert) but I 
expect someone
replying: "let's implement C99 division right instead".

Paolo.