I am trying different kinds of parallelization using OpenMP. As a result I have several lines of #pragma omp parallel for
in my code which I (un-)comment alternating. Is there a way to make these lines condi开发者_StackOverflowtional with something like the following, not working code?
define OMPflag 1
#if OMPFlag pragma omp parallel for
for ...
C99 has the _Pragma
keyword that allows you to place what otherwise would be #pragma
inside macros. Something like
#define OMP_PARA_INTERNAL _Pragma("omp parallel for")
#if [your favorite condition]
#define OMP_FOR OMP_PARA_INTERNAL for
#else
#define OMP_FOR for
#endif
and then in your code
OMP_FOR (unsigned i; i < n; ++i) {
...
}
An OpenMP parallel construct can have an if
clause specified. In Fortran I'd write something like this:
!$omp parallel if(n>25) ...
I sometimes use this when a problem might be too small to bother parallelising. I guess you could use the same approach to check a debug flag at run time. I'll leave it up to you to figure out the C++ syntax but it's probably exactly the same.
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