Re: Enabling OpenMP by default

[John W. Eaton]

On 03/10/2013 08:14 PM, Susi Lehtola wrote:
> On Sun, 10 Mar 2013 17:50:05 -0300
> Júlio Hoffimann<address@hidden>  wrote:
> > For every occurrence (239 so far) of a parallel region we ideally
> > want the pragma to be wrapped by a #ifdef directive (e.g. #if
> > defined(_OPENMP) ... #endif), but this would cause an unacceptable
> > decrease in readability since 239*3 = 717 new lines of boilerplate.
> > The number of regions is that high because the array classes don't
> > satisfy the DRY principle, and probably can't.
>
> This is just a thought, but if you want to avoid a lot of #ifdef's,
> then maybe you could just #define some pragmas to be used inside
> Octave, e.g.
>
> #ifdef _OPENMP
> #pragma omp parallel for
> #endif
>
> could be just e.g.
>
> #octave_omp_parfor
>
> and this macro could be defined to be empty if OpenMP is disabled...

That doesn't work as you can not #define a #pragma.  But your message 
prompted me to do some searching and it appears we could use the _Pragma 
keyword.  _Pragma will work in macros and I think it should be portable 
to any compiler that can compile Octave's C++.

jwe