ignore OpenMP in C++ program on machine without it

Hi,

I want to run a C++ program using OpenMP on several machines. Some of them have OpenMP installed and others don't because their GCC is below version 4.2.x which doesn't support OpenMP. .

How could I make the Makefile of my program know if a machine has no OpenMP and ask g++ to ignore in my code those "#include omp.h", OpenMP directives (like "#pragma omp parallel ...") and/or library functions (like "tid = omp_get_thread_num();") instead of failing compilation? So that I can run my program without multi-threading on those machines without OpenMP?

Thanks and regards!

Pre-defined Compiler Macros
Use the __GNUC__ macros to ID the compiler version, and conditionally compile accordingly.

You can look into using autoconf and automake which handle these situations for you. This may be a little overkill if you just have a simple application though.

OpenMP is designed in such a way that if your compiler doesn't support it, it does nothing and the resulting program behaves correctly. Unless you use OpenMP specific functions like omp_get_num_threads();