The variables OMP_DYNAMIC, OMP_MAX_ACTIVE_LEVELS, OMP_NESTED, OMP_NUM_THREADS, OMP_SCHEDULE, OMP_STACKSIZE,OMP_THREAD_LIMIT and OMP_WAIT_POLICY are defined by section 4 of the OpenMP specifications in version 3.1, while GOMP_CPU_AFFINITY and GOMP_STACKSIZE are GNU extensions.