Ignore OpenMP on machine that does not have it

Question

I have a C++ program using OpenMP, which will run on several machines that may have or not have OpenMP installed.

How could I make my program know if a machine has no O

Answer 1

OpenMP compilation adds the preprocessor definition "_OPENMP", so you can do:

#if defined(_OPENMP)
   #pragma omp ...
#endif

For some examples, see http://bisqwit.iki.fi/story/howto/openmp/#Discussion and the code which follows.