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

There is another approach that I like, borrowed from Bisqwit:

#if defined(_OPENMP)
#include 
extern const bool parallelism_enabled = true;
#else
extern const bool parallelism_enabled = false;
#endif

Then, start your OpenMP parallel for loops like this:

#pragma omp parallel for if(parallelism_enabled)

Note: there are valid reasons for not using pragma, which is non-standard, hence why Google and others do not support it.