OMP_NESTED – Nested parallel regions

Description:

Enable or disable nested parallel regions, i.e., whether team members are allowed to create new teams. The value of this environment variable shall be TRUE or FALSE. If set to TRUE, the number of maximum active nested regions supported will by default be set to the maximum supported, otherwise it will be set to one. If OMP_MAX_ACTIVE_LEVELS is defined, its setting will override this setting. If both are undefined, nested parallel regions are enabled if OMP_NUM_THREADS or OMP_PROC_BINDS are defined to a list with more than one item, otherwise they are disabled by default.

See also:

omp_set_max_active_levels – Limits the number of active parallel regions, omp_set_nested – Enable/disable nested parallel regions

Reference:

OpenMP specification v4.5, Section 4.6