[GiNaC-devel] GiNaC is not a C compiler [Was: Optimized C-style output]

[Stefan Weinzierl]

Hi,

I have the impression that I hit on an internal religous war on the
evilness of certain files. This was not my intention.

To avoid other misunderstandings, I did not propose to replace standard
print_csrc output by something else. This should remain as it is.

But I would like to see that GiNaC offers the opportunity that C code is
generated in an additional  different way with temporary variables. (I
carefully try to avoid the word "optimized code" here, but that's what I mean.)
The decision which output format to use should be put into the hands of
the user, he or she will know best what suits here needs.

I will have a look at the excompiler.cpp file and see how it fits
together.

There are also several good points which Alexei mentioned:

If expressions of type add and mul should be substituted or rather
calculated on the fly is certainly worth a discussion.
My experience would lead me towards substitution, but I admit that in
different circumstances the conclusion could be the opposite.
Maybe flags or a visitor object could fine-tune this behaviour on an
individual basis.

Collecting and running normal() on the coefficients is also something
I do privately on expressions where I excpect improvements. As normal()
involves a gcd computation I did not include it in the code generation
routine.

Best wishes,

    Stefan


On Wed, 21 Mar 2007, Jens Vollinga wrote:

> Dear Stefan,
>
> Stefan Weinzierl schrieb:
> > I believe an efficient way to do this is to write the expression as C code
> > into a file, compile and reload the compiled function into memory.
>
> Sheplyakov Alexei schrieb:
>  > However, GiNaC does support code generation, and even got that evil
>  > GiNaC::excompiler thing...
>
> The evil thing Alexei mentioned is part of CVS HEAD. Maybe you can have
> a look at it (it is in the files excompiler.* mostly). Most parts of it
> are unscrupulously stolen from your code in gtybalt ...
> Maybe we can combine/improve that code with your patch. What do you think?
>
> Regards,
> Jens
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