Verifying OpenMP compatibility

[jwreep]

Since not all compilers (or versions) support OpenMP, it would be useful to have a check that prevents crashes when attempting to use OpenMP with a compiler that doesn't support it.

For example, embed the OPENMP define in something like the following:

// Check if compiler is GNU:
#if defined(__GNUC__) || defined(__GNUG__)   
   // Check version >= 6.1, which has full OpenMP support:
   #if (__GNUC__ > 6) ||  (__GNUC__ == 6 && (__GNUC_MINOR__ >= 1) ) 
      #define OPENMP
   #endif 
#endif 

This isn't strictly necessary, but it might save a headache if one forgets to verify compiler version.

[jwreep]

Alternatively, a warning could be added to alert the user.

// Check if compiler is GNU:
#if defined(__GNUC__) || defined(__GNUG__)   
   // Check version >= 6.1, which has full OpenMP support:
   #if (__GNUC__ > 6) ||  (__GNUC__ == 6 && (__GNUC_MINOR__ >= 1) ) 
      printf("Compiler version not compatible with OpenMP: expect this to crash!");
   #endif 
#endif