Re: [Help-gsl] callback performance

[Brian Gough]

At Sun, 15 Jul 2007 06:47:28 -0700 (PDT),
Amir Hossein Zamani Safa wrote:
> I've got much better speed up results in Numeric Integration and
> root finding where I redefined the callback functions
> (gsl_function_struct and gsl_function_fdf_struct) as __fastcall
> (instead of standard __cdecl)
> 
> Why the GSL library does not use __fastcall (as a marco option)
> overall?
> 

Thanks for your email.

Concerns about portability are the main reason for not using any
attribute declarations in the header files.

Also, presumably this would only beneficial if the function is very
simple---otherwise the function call overhead should be small in
comparison to the actual computation of the value.

It would be interesting to see some numbers on the speed up.  I have
never investigated the effects of __fastcall myself.  Maybe it is
something that should be more widely known.

-- 
Brian Gough

Network Theory Ltd,
Publishing Free Software Manuals --- http://www.network-theory.co.uk/