Global variable with OpenMP

Question

Hi All,

Question on OpenMP for multi-threaded code:

Are all global variables shared by the threads? How does one make certain global variable private to master thread?

Thanks

PS: It is a C code.

Answer 1

if i recall correctly

#pragma omp threadprivate

global variables are a bit tricky, if they has to be initialized, you have to use copyfirst directive (i think that is correct name). also threadprivate variables may carry a significant penalty, on some implementations variable access becomes a function call.