[phobos] std.complex: updates, bugs, and questions

[Lars Tandle Kyllingstad]

Don Clugston wrote:
> On 28 March 2010 17:35, Lars Tandle Kyllingstad <lars at kyllingen.net> wrote:
>> I've committed an update of my std.complex proposal:
>>
>>  http://github.com/kyllingstad/ltk/blob/master/ltk/complex.d
>>
>> The current status is as follows:
>>
>> - Changed mod() to abs(), like Don requested.  I'll implement abs() with
>> std.math.hypot() as soon as bug 4023 is fixed.
> 
> Yup, that's an embarrassing one. I'll get it fixed ASAP.

Thanks!


>> [...]
>>
>>
>> Two questions:
>>
>> I had a look at the implementation of std.numeric.FPTemporary, and noted
>> that it's just an alias for real, regardless of the specified type. (Also,
>> the std.math.hypot() function is just defined for the real type.)  Can we be
>> sure this is always what the user wants?  Won't using double be faster in
>> some cases, or is it so that calculations are done with 80-bit precision
>> anyway?
> 
> On x86, real is always better. On other architectures, the definition
> of FPTemporary will be different.
> 
>> As you may have seen, I've put in two different multiplication formulae.  I
>> did this because I read that multiplication is slow on some architectures,
>> and the first formula has fewer multiplications.  On my machine, however,
>> the second (and "standard") one is slightly faster. Do you know which
>> architecures this refers to, and are any of them relevant for D?
> 
> I don't think that would be true of any architectures made in the last
> twenty years.
> Worrying about that would be premature optimisation.

All right, I'll remove it then.  Thanks again!

-Lars


> WRT both these last two points, array operations on complex types is
> the place where optimisation really matters.
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