Thread: parallel for and threadpools

Hi,

if I use an openMP parallel for construct like

Code:

#pragma omp parallel for num_threads(4)
for(int i=0; i<10; ++i){}

when are the 4 threads created, after the pragma and therefore eventually very often during process live time or is the run time clever enough to create a ready to use thread pool prior process start up?

Thanks in advance!