Complex numbers in compilers - upcoming GNU Tools Cauldron.

Complex numbers in compilers - upcoming GNU Tools Cauldron.

[Toon Moene]

This is going to be an interesting discussion.

In the upcoming GNU Tools Cauldron meeting the representation of complex 
numbers in GCC will be discussed from the following "starting point":

"Complex numbers are used to describe many physical phenomenons and are 
of prime importance in data signal processing. Nevertheless, despite 
being part of the C and C++ standards since C99, they are still not 
completely first class citizens in mainstream compilers."

*This* is from the Fortran 66 Standard (http://moene.org/~toon/f66.pdf - 
a photocopy of the 1966 Standard):

- - - - -

Chapter 4. Data Types:
...
4.2.4 Complex Type.

A complex datum is processor approximation to the value of a complex number.
...

- - - - -

I can recall people complaining about the way complex arithmetic was 
handled by compilers since the late 70s.

This is even obvious in weather forecasting software I have to deal with 
*today* (all written in Fortran). Some models use complex variables to 
encode the "spectral" (wave-decomposed) computations in parts where that 
is useful - others just "degrade" those algorithms to explicitly use reals.

Kind regards,

-- 
Toon Moene - e-mail: toon@moene.org - phone: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands

Re: Complex numbers in compilers - upcoming GNU Tools Cauldron.

[Richard Biener]

On Tue, Sep 5, 2023 at 10:44 PM Toon Moene <toon@moene.org> wrote:
>
> This is going to be an interesting discussion.
>
> In the upcoming GNU Tools Cauldron meeting the representation of complex
> numbers in GCC will be discussed from the following "starting point":
>
> "Complex numbers are used to describe many physical phenomenons and are
> of prime importance in data signal processing. Nevertheless, despite
> being part of the C and C++ standards since C99, they are still not
> completely first class citizens in mainstream compilers."
>
> *This* is from the Fortran 66 Standard (http://moene.org/~toon/f66.pdf -
> a photocopy of the 1966 Standard):
>
> - - - - -
>
> Chapter 4. Data Types:
> ...
> 4.2.4 Complex Type.
>
> A complex datum is processor approximation to the value of a complex number.
> ...
>
> - - - - -
>
> I can recall people complaining about the way complex arithmetic was
> handled by compilers since the late 70s.
>
> This is even obvious in weather forecasting software I have to deal with
> *today* (all written in Fortran). Some models use complex variables to
> encode the "spectral" (wave-decomposed) computations in parts where that
> is useful - others just "degrade" those algorithms to explicitly use reals.

Lack of applications / benchmarks using complex numbers is also a
problem for any work on this.

Richard.

> Kind regards,
>
> --
> Toon Moene - e-mail: toon@moene.org - phone: +31 346 214290
> Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands

Re: Complex numbers in compilers - upcoming GNU Tools Cauldron.

[Martin Uecker]

Am Dienstag, dem 12.09.2023 um 11:25 +0200 schrieb Richard Biener via Gcc:
> On Tue, Sep 5, 2023 at 10:44 PM Toon Moene <toon@moene.org> wrote:
> > 
> > This is going to be an interesting discussion.
> > 
> > In the upcoming GNU Tools Cauldron meeting the representation of complex
> > numbers in GCC will be discussed from the following "starting point":
> > 
> > "Complex numbers are used to describe many physical phenomenons and are
> > of prime importance in data signal processing. Nevertheless, despite
> > being part of the C and C++ standards since C99, they are still not
> > completely first class citizens in mainstream compilers."
> > 
> > *This* is from the Fortran 66 Standard (http://moene.org/~toon/f66.pdf -
> > a photocopy of the 1966 Standard):
> > 
> > - - - - -
> > 
> > Chapter 4. Data Types:
> > ...
> > 4.2.4 Complex Type.
> > 
> > A complex datum is processor approximation to the value of a complex number.
> > ...
> > 
> > - - - - -
> > 
> > I can recall people complaining about the way complex arithmetic was
> > handled by compilers since the late 70s.
> > 
> > This is even obvious in weather forecasting software I have to deal with
> > *today* (all written in Fortran). Some models use complex variables to
> > encode the "spectral" (wave-decomposed) computations in parts where that
> > is useful - others just "degrade" those algorithms to explicitly use reals.
> 
> Lack of applications / benchmarks using complex numbers is also a
> problem for any work on this.
> 

I could probably provide some examples such as a FFT, 
complex Gaussian random number generation, mandelbrot
set computation, etc.

Martin

Re: Complex numbers in compilers - upcoming GNU Tools Cauldron.

[Paul Koning]

> On Sep 12, 2023, at 7:12 AM, Martin Uecker via Gcc <gcc@gcc.gnu.org> wrote:
> 
> Am Dienstag, dem 12.09.2023 um 11:25 +0200 schrieb Richard Biener via Gcc:
>>> ...
>> 
>> Lack of applications / benchmarks using complex numbers is also a
>> problem for any work on this.
> 
> I could probably provide some examples such as a FFT, 
> complex Gaussian random number generation, mandelbrot
> set computation, etc.

Another nice one might be NEC-2, an electromagnetic field analyzer used to model antennas and similar problems.

	paul

Re: Complex numbers in compilers - upcoming GNU Tools Cauldron.

[Toon Moene]

On 9/12/23 11:25, Richard Biener wrote:

> On Tue, Sep 5, 2023 at 10:44 PM Toon Moene <toon@moene.org> wrote:

>> This is even obvious in weather forecasting software I have to deal with
>> *today* (all written in Fortran). Some models use complex variables to
>> encode the "spectral" (wave-decomposed) computations in parts where that
>> is useful - others just "degrade" those algorithms to explicitly use reals.
> 
> Lack of applications / benchmarks using complex numbers is also a
> problem for any work on this.

Yes, a certain amount of circular "reasoning" is at work here.

However, there is sufficient Fortran programming out there to study how 
to compile complex number arithmetic ... LAPACK and its test programs.

I realize that they are not "benchmarks" in the sense that they do not 
give you a measure how to speed up the code the compiler generates; but 
they are real-life complex number algorithms coded in a programming 
language that had complex number support from the beginning.

Hope this helps,

-- 
Toon Moene - e-mail: toon@moene.org - phone: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands