How to disable OpenMP directives in a nice way?

c++ c openmp
Jakub M. picture Jakub M. · Oct 21, 2011 · Viewed 15.7k times · Source

I have C++ code with OpenMP pragmas inside. I want to test this code both for multithread mode (with OpenMP) and in single thread mode (no OpenMP).

For now, to switch between modes I need to comment #pragma omp (or at least parallel).

What is the cleanest, or default, way to enable / disable OpenMP?

Answer

snatverk picture snatverk · Dec 5, 2011

If you do not compile with -fopenmp option, you won't get the parallel code. You can do it with an appropiate define and makefile that generates all codes.

The OpenMP documentation says (only an example):

#ifdef _OPENMP
   #include <omp.h>
#else
   #define omp_get_thread_num() 0
#endif

See http://www.openmp.org/mp-documents/spec30.pdf (conditional compilation).

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